head diameter, and cup thickness studied with a hip simulator. *Acta Orthop Scand.*

high congenital dislocation of the hip. *J Arthroplasty.* Vol.17, No.1, (January), pp.41-

weight-bearing ball- and socket joint in a young growing animal; gross alterations in bone and cartilage. *J Bone Joint Surg Am.* Vol.40-A, No.5, (October), pp.1121-1127,

fixation for arthroplasty of the dysplastic hip. A case report. *J Arthroplasty.* Vol.3,

bonding to cancellous bone graft. An experimental study in dogs. Read the combined meetings of the Hellenic Association of Orthopaedic Surgery and

**10**

*Serbia*

**Hip Arthroplasty in Highly Dislocated Hips**

Developmental disorder of the hip (DDH) is the most frequent disease of this joint. It is manifested by dysplasia, subluxation or luxation in childhood period and arthrosis in adults. Early degenerative changes of the hip occur at the location of disordered anatomy and biomechanics already in youth, while in the childhood age they are mostly

DDH mostly occurs in females, even 4-10 times more often than in males. Also, the disease is unevenly expanded, both ethnically and geographically, but also according to different habits in regard to the nursing care of neonates and infants. For example, the disease does not develop among the Bantu colored population, while in Canadian Indians it is very frequent rating even 12.3%, which is related to their habit of nursing babies in narrow wooden cradles. In those Indians who do not practice it the frequency is considerably lower

In our regions data on the frequency of DDH vary between 0.5-34.8%, depending on the regional customs in nursing children, but also on the method applied in the diagnostics of the disease; clinically it is the lowest, radiographically higher, and ultrasonographically the highest (Klisic et al., 1984). Former classical term of the disease was "congenital dislocation of the hip", which, over the years became unsustainable, since it has been disclosed that the disease is not congenital, but that it often develops after birth under the influence of environmental factors. In addition, it does not always involve a total dislocation, but only disturbed interrelationship among the joint surfaces of the hip. Although the former term can be still found in the literature, today the term "developmental disorder of the hip" is

To understand the problem faced by the arthroplastic surgeon in treating a high luxation of the hip in adults, it is necessary to be acquainted with etiopathogenesis of the disease,

After numerous years of research, attitudes of the leading world experts on this disease have been mostly brought in accordance (Ando & Gotoh 1990; Cherney & Westin 1989;

**1. Introduction**

asymptomatic (Ando & Gotoh, 1990).

(1.2%) (Vukasinovic et al., 1994, 2004).

accepted worldwide (Klisic, 1989).

**2. Etiopathogenesis and pathoanatomy of DDH**

Klisic et al. 1984, 1989; Vukasinovic & Bascarevic, 2004).

because it is in a direct association with its pathoanatomic substrate.

Zoran Bascarevic1,2, Zoran Vukasinovic1,2, Violeta Bascarevic2 and Vladimir Bascarevic1,3 *1Faculty of Medicine, University of Belgrade, Belgrade 2Institute of Orthopaedic Surgery "Banjica", Belgrade*

*3Institute of Neurosurgery, Clinical Center of Serbia, Belgrade*

dislocation of the hip. *J Arthroplasty.* Vol.12, No.8, (December), pp.880-888, ISBN 9458253

Yoder S.A., Brand R.A., Pedersen D.R., O'Gorman T.W. (1988). Total hip acetabular component position affects component loosening rates. *Clin Orthop Relat Res.* Vol.228, (March), pp.79-87, ISBN 3342591

## **Hip Arthroplasty in Highly Dislocated Hips**

Zoran Bascarevic1,2, Zoran Vukasinovic1,2,

 Violeta Bascarevic2 and Vladimir Bascarevic1,3 *1Faculty of Medicine, University of Belgrade, Belgrade 2Institute of Orthopaedic Surgery "Banjica", Belgrade 3Institute of Neurosurgery, Clinical Center of Serbia, Belgrade Serbia*

## **1. Introduction**

152 Recent Advances in Hip and Knee Arthroplasty

Yoder S.A., Brand R.A., Pedersen D.R., O'Gorman T.W. (1988). Total hip acetabular

Vol.228, (March), pp.79-87, ISBN 3342591

9458253

dislocation of the hip. *J Arthroplasty.* Vol.12, No.8, (December), pp.880-888, ISBN

component position affects component loosening rates. *Clin Orthop Relat Res.*

Developmental disorder of the hip (DDH) is the most frequent disease of this joint. It is manifested by dysplasia, subluxation or luxation in childhood period and arthrosis in adults. Early degenerative changes of the hip occur at the location of disordered anatomy and biomechanics already in youth, while in the childhood age they are mostly asymptomatic (Ando & Gotoh, 1990).

DDH mostly occurs in females, even 4-10 times more often than in males. Also, the disease is unevenly expanded, both ethnically and geographically, but also according to different habits in regard to the nursing care of neonates and infants. For example, the disease does not develop among the Bantu colored population, while in Canadian Indians it is very frequent rating even 12.3%, which is related to their habit of nursing babies in narrow wooden cradles. In those Indians who do not practice it the frequency is considerably lower (1.2%) (Vukasinovic et al., 1994, 2004).

In our regions data on the frequency of DDH vary between 0.5-34.8%, depending on the regional customs in nursing children, but also on the method applied in the diagnostics of the disease; clinically it is the lowest, radiographically higher, and ultrasonographically the highest (Klisic et al., 1984). Former classical term of the disease was "congenital dislocation of the hip", which, over the years became unsustainable, since it has been disclosed that the disease is not congenital, but that it often develops after birth under the influence of environmental factors. In addition, it does not always involve a total dislocation, but only disturbed interrelationship among the joint surfaces of the hip. Although the former term can be still found in the literature, today the term "developmental disorder of the hip" is accepted worldwide (Klisic, 1989).

## **2. Etiopathogenesis and pathoanatomy of DDH**

To understand the problem faced by the arthroplastic surgeon in treating a high luxation of the hip in adults, it is necessary to be acquainted with etiopathogenesis of the disease, because it is in a direct association with its pathoanatomic substrate.

After numerous years of research, attitudes of the leading world experts on this disease have been mostly brought in accordance (Ando & Gotoh 1990; Cherney & Westin 1989; Klisic et al. 1984, 1989; Vukasinovic & Bascarevic, 2004).

Hip Arthroplasty in Highly Dislocated Hips 155

developmental stimulation caused by the absent head in the joint. (Vukasinovic & Djoric,

*The limbus* gradually flattens and thickens first in the superoposterior portion. Gradually, a groove is formed enabling the head to slide out of the joint. It is partially grown together with the capsule and is lacking in some areas. In subluxations it is everted, while in full luxations it is inverted and interpolated between the head and the acetabulum. (Vukasinovic

*The ligamentum teres* differs depending on the severity of disorder ranging from normal and occasionally hypoplastic, elongated and hypertrophic, up to fully atrophic in

*The femoral head* can be differently formed, from normal - spherical to flattened and deformed with limbal impression. It is most often decreased with highly expressed fovea.

*The femoral neck* is usually shortened with increased anteversion. However, it can even be normal, but also retroverted. The collo-diaphyseal angle is usually normal, but can be also

*The capsule of the joint* is thickened and mostly lax, but can be also tightened. With the progression of luxation, it becomes lengthened and narrowed in the empty space between the head and the acetabulum resuming the form of a sand-clock. It grows adhering to the bones that form the acetabulum, thus impeding reduction. (Vukasinovic & Djoric, 1994;

*The ligamentum transversum* is most frequently strong and thickened and additionally narrows the already dysplastic acetabulum. Its position is the only constant one in the pathological anatomy of the hip in high luxations and represents the major and occasionally the only orientation point in the attempt to find the true acetabulum in the total arthroplasty

*Muscular motion starters* are also changed, particularly the iliopsoas; its tendon is short and thickened, while short external rotators are hypotrophic, but also shortened. However, the major hip abductors, primarily the gluteus medius, although hypotrophic, are not shortened and do not create resistance before reduction. In addition, after arthroplasty and induction of the necessary muscular length (close to physiological) they show unusual vitality in the restitution of strength and function of joints. (Vukasinovic & Djoric, 1994; Bascarevic &

Finally, when we speak of high luxations of the hip in the light of aloarthroplasty, attention should be turned to the fact that DDH is not the only condition causing high luxation of the hip in adults. Hip trauma, juvenile rheumatism, neonatal sepsis and some other similar conditions can also cause established hip luxation that can be resolved only when treated by a total hip arthroplasty (Besset et al., 2003; Betz et al., 1990; Choi et al., 1990; Learmonth et al., 1989; Maric & Haynes 1993; Ruddlesdin et al., 1986; Young-Hoo et

In the literature there are several classifications that determine high hip dislocation in adults. **Crowe** classification of hip dislocation describes four stages, depending on the

1994; Bascarevic & Vukasinovic, 2004).

decreased or conversely increased.

Bascarevic & Vukasinovic, 2004).

Vukasinovic, 2004).

al., 2009).

of the hip. (Bascarevic & Vukasinovic, 2004).

**3. Classification of high hip dislocation in adults**

luxations.

& Djoric, 1994; Bascarevic & Vukasinovic, 2004).

(Vukasinovic & Djoric, 1994; Bascarevic & Vukasinovic, 2004).

There is the predominating opinion that two groups of etiological factors contribute to the development of DDH; endogenous and exogenous (mechanical). (Vukasinovic & Djoric, 1994; Vukasinovic & Bascarevic, 2004).

Endogenous factors involve acetabular dysplasia, increased anteversion of the femoral neck and head, as well as joint laxity. Beside primary acetabular dysplasia, which is one of the causes of the disease, the so called secondary acetabular dysplasia is also mentioned, which develops due to hip dislocation itself. Although a lax joint capsule can be generalized, as for example when associated with Ehlers-Danlos syndrome, in DDH it is mostly only elongated in the superior-posterior portion, thus secondary, caused by luxation instead of being its major cause. (Vukasinovic & Djoric, 1994; Vukasinovic & Bascarevic, 2004).

Exogenous (mechanical) factors involve the basis of the so called mechanical theory which has been obtaining a rising number of supporters as it can explain the frequency of luxations in first pregnancies, pelvic positions, Cesarean section, high birth weight, oligohydramnion and fetopelvic disproportion. In addition, hip luxation due to DDH is often associated with other deformities of the feet, knees, neck (torticollis) and other. (Vukasinovic & Djoric, 1994; Vukasinovic & Bascarevic, 2004).

Exogenous (mechanical) factors can affect the fetus intrauterine, during delivery and postnatally. The intrauterine factors mostly involve three luxating fetal positions, while the postnatal ones above all refer to traditional baby diapering with bent knees and extended legs. Not only can such a position induce a spontaneous reduction of unstable joint, but it can also provoke the development of luxation. The mechanical factors occurring during birth can be discarded today, because even in newborns the hips are so stable that rough manual manipulation will sooner cause femoral head epyphysiolisis or diaphyseal fracture than hip luxation. It is considered that action of two factors is necessary for DDH to develop; a specific position of the femur involving the head which is not orientated toward the base of the acetabulum and expulsion force pushing the baby's head out of the acetabulum. (Vukasinovic & Djoric, 1994; Vukasinovic & Bascarevic, 2004).

In short, DDH pathogenesis features the following: a predisposing base representing unstable genetic factors, above all acetabular dysplasia and capsular laxity, while the determinant mechanical factors exert pressure on the great trochanter in one of the luxating fetal positions. This can explain the growing incidence of bilateral luxations in pelvic births; forces act on both great trochanters, i.e. isolated left-sided luxations in normal birth (baby head down presentation with left turned back); the maternal promontorium exerting pressure on the great trochanter. (Vukasinovic & Djoric, 1994; Vukasinovic & Bascarevic, 2004).

Pathological changes involve all structures of the joint, while the pathoanatomical substrate differs depending on the degree of disorder.

*The acetabulum* changes in depth during physiological development becoming the shallowest in the perinatal period. Spherical formation (joint congruency) is caused by the presence and pressure of the femoral head. In DDH unfavorable intra-articular relationships lead to acetabular anterior and superior deficiency, as well as its anteversion. Consequently, the acetabulum becomes ovoid or even triangle-like insufficiently covering the femoral head. It is mostly dilated, but can be also completely undeveloped, narrowed due to the lack of

There is the predominating opinion that two groups of etiological factors contribute to the development of DDH; endogenous and exogenous (mechanical). (Vukasinovic & Djoric,

Endogenous factors involve acetabular dysplasia, increased anteversion of the femoral neck and head, as well as joint laxity. Beside primary acetabular dysplasia, which is one of the causes of the disease, the so called secondary acetabular dysplasia is also mentioned, which develops due to hip dislocation itself. Although a lax joint capsule can be generalized, as for example when associated with Ehlers-Danlos syndrome, in DDH it is mostly only elongated in the superior-posterior portion, thus secondary, caused by luxation instead of being its major cause. (Vukasinovic & Djoric, 1994; Vukasinovic &

Exogenous (mechanical) factors involve the basis of the so called mechanical theory which has been obtaining a rising number of supporters as it can explain the frequency of luxations in first pregnancies, pelvic positions, Cesarean section, high birth weight, oligohydramnion and fetopelvic disproportion. In addition, hip luxation due to DDH is often associated with other deformities of the feet, knees, neck (torticollis) and other. (Vukasinovic & Djoric, 1994;

Exogenous (mechanical) factors can affect the fetus intrauterine, during delivery and postnatally. The intrauterine factors mostly involve three luxating fetal positions, while the postnatal ones above all refer to traditional baby diapering with bent knees and extended legs. Not only can such a position induce a spontaneous reduction of unstable joint, but it can also provoke the development of luxation. The mechanical factors occurring during birth can be discarded today, because even in newborns the hips are so stable that rough manual manipulation will sooner cause femoral head epyphysiolisis or diaphyseal fracture than hip luxation. It is considered that action of two factors is necessary for DDH to develop; a specific position of the femur involving the head which is not orientated toward the base of the acetabulum and expulsion force pushing the baby's head out of the acetabulum. (Vukasinovic & Djoric, 1994; Vukasinovic &

In short, DDH pathogenesis features the following: a predisposing base representing unstable genetic factors, above all acetabular dysplasia and capsular laxity, while the determinant mechanical factors exert pressure on the great trochanter in one of the luxating fetal positions. This can explain the growing incidence of bilateral luxations in pelvic births; forces act on both great trochanters, i.e. isolated left-sided luxations in normal birth (baby head down presentation with left turned back); the maternal promontorium exerting pressure on the great trochanter. (Vukasinovic & Djoric, 1994; Vukasinovic & Bascarevic,

Pathological changes involve all structures of the joint, while the pathoanatomical substrate

*The acetabulum* changes in depth during physiological development becoming the shallowest in the perinatal period. Spherical formation (joint congruency) is caused by the presence and pressure of the femoral head. In DDH unfavorable intra-articular relationships lead to acetabular anterior and superior deficiency, as well as its anteversion. Consequently, the acetabulum becomes ovoid or even triangle-like insufficiently covering the femoral head. It is mostly dilated, but can be also completely undeveloped, narrowed due to the lack of

1994; Vukasinovic & Bascarevic, 2004).

Bascarevic, 2004).

Bascarevic, 2004).

2004).

Vukasinovic & Bascarevic, 2004).

differs depending on the degree of disorder.

developmental stimulation caused by the absent head in the joint. (Vukasinovic & Djoric, 1994; Bascarevic & Vukasinovic, 2004).

*The limbus* gradually flattens and thickens first in the superoposterior portion. Gradually, a groove is formed enabling the head to slide out of the joint. It is partially grown together with the capsule and is lacking in some areas. In subluxations it is everted, while in full luxations it is inverted and interpolated between the head and the acetabulum. (Vukasinovic & Djoric, 1994; Bascarevic & Vukasinovic, 2004).

*The ligamentum teres* differs depending on the severity of disorder ranging from normal and occasionally hypoplastic, elongated and hypertrophic, up to fully atrophic in luxations.

*The femoral head* can be differently formed, from normal - spherical to flattened and deformed with limbal impression. It is most often decreased with highly expressed fovea. (Vukasinovic & Djoric, 1994; Bascarevic & Vukasinovic, 2004).

*The femoral neck* is usually shortened with increased anteversion. However, it can even be normal, but also retroverted. The collo-diaphyseal angle is usually normal, but can be also decreased or conversely increased.

*The capsule of the joint* is thickened and mostly lax, but can be also tightened. With the progression of luxation, it becomes lengthened and narrowed in the empty space between the head and the acetabulum resuming the form of a sand-clock. It grows adhering to the bones that form the acetabulum, thus impeding reduction. (Vukasinovic & Djoric, 1994; Bascarevic & Vukasinovic, 2004).

*The ligamentum transversum* is most frequently strong and thickened and additionally narrows the already dysplastic acetabulum. Its position is the only constant one in the pathological anatomy of the hip in high luxations and represents the major and occasionally the only orientation point in the attempt to find the true acetabulum in the total arthroplasty of the hip. (Bascarevic & Vukasinovic, 2004).

*Muscular motion starters* are also changed, particularly the iliopsoas; its tendon is short and thickened, while short external rotators are hypotrophic, but also shortened. However, the major hip abductors, primarily the gluteus medius, although hypotrophic, are not shortened and do not create resistance before reduction. In addition, after arthroplasty and induction of the necessary muscular length (close to physiological) they show unusual vitality in the restitution of strength and function of joints. (Vukasinovic & Djoric, 1994; Bascarevic & Vukasinovic, 2004).

Finally, when we speak of high luxations of the hip in the light of aloarthroplasty, attention should be turned to the fact that DDH is not the only condition causing high luxation of the hip in adults. Hip trauma, juvenile rheumatism, neonatal sepsis and some other similar conditions can also cause established hip luxation that can be resolved only when treated by a total hip arthroplasty (Besset et al., 2003; Betz et al., 1990; Choi et al., 1990; Learmonth et al., 1989; Maric & Haynes 1993; Ruddlesdin et al., 1986; Young-Hoo et al., 2009).

### **3. Classification of high hip dislocation in adults**

In the literature there are several classifications that determine high hip dislocation in adults. **Crowe** classification of hip dislocation describes four stages, depending on the

Hip Arthroplasty in Highly Dislocated Hips 157

Fig. 1a. A 35-year old male after acetabular osteosynthesis performed due to traumatic dislocation of the right hip with superior and posterior acetabular wall fracture.

Fig. 1b.The same patient, six month later high dislocation of the hip occured due to failed osteosynthesis. Full absence of superior and posterior acetabular walls. Leg length

discrepancy was 48 mm.

position of the femoral head within the joint. The first three stages define the progressive migration of the head to the level of subluxation, while the fourth stage is luxation (Crowe et al., 1979).

According to the classification by **Eftekhar** the problem of the developmental disorders of the hip is viewed through acetabular changes. Four stages are also described; A/ slightly widened and dysplastic acetabulum with milder deformation of the head, B/ intermediately positioned false acetabulum, C/ high position of the false acetabulum, and D/ high nonweight bearing dislocation with the femoral head that has never been in contact with the iliac bone (Eftekhar 1978).

The most modern and up-to-now the best classification recommending total arthroplasty in relation to joint deficiency was given by **Hartofilakidis** et al. in 1996, according to which the condition was viewed as acetabular dysplasia, low dislocation and high dislocation (Hartofilakidis et al., 1996).

## **4. Treatment of high hip dislocation in adults**

Treatment of the developmental disorder of the hip should be initiated at the moment of the disease detection, and the best results are achieved in the earliest childhood. At that period various forms of non-operative and operative treatments by biological surgeries are possible to be applied. (Vukasinovic & Djoric, 1994; Vukasinovic & Bascarevic, 2004). However, if the treatment is initiated only after the onset of arthrosis or under the conditions of high nonweight bearing hip luxation, operative treatment modalities are only reduced to total hip arthroplasty.

The operative procedure is most challenging because of changed anatomical correlations. The topographic correlation of muscles initiators of the hip, joint capsule and neurovascular elements are changed and unstable thus making the operative approach very difficult. The identification of bone structures, primarily of the true acetabulum, is also not at all easy (Lai et al., 1996, 2005; Charnley & Feagin 1973; Crowe et al., 1979; Dunn & Hess, 1976; Eskelinen et al., 2006; Hartofilakidis et al., 1998, 2004, 2008; Holinka et al., 2010; Paavilainen et al., 1990).

The ligamentum transversum is the only reliable parameter determining, not only the height and center of the artificial hip, but also the anteversion (flexion) position of the acetabular ring.

The proximal part of the femoral bone canal is very narrow, with markedly increased anteversion. The acetabular bone mass is underdeveloped, while the bone is insufficiently firm. The joint capsule is elongated, inelastic and thickened, while the surrounding muscles are without any strength, shortened and grown to the capsule. The neurovascular structures are shortened and dislocated from their anatomic positions (Carrlson et al., 2003; Holinka et al., 2010; Paavilainen et al., 1990).

In the past there were numerous unsuccessful attempts to perform total hip arthroplasty in adults at the location of high luxation caused by developmental disorder. Exactly due to excessively changed anatomic characteristics of the acetabulum and proximal femur, the operative procedure and the entire surgical concept are most complicated. Therefore, some authors consider high hip luxation as a contraindication for total arthroplasty (Figs. 1, 2, 3).

position of the femoral head within the joint. The first three stages define the progressive migration of the head to the level of subluxation, while the fourth stage is luxation (Crowe et

According to the classification by **Eftekhar** the problem of the developmental disorders of the hip is viewed through acetabular changes. Four stages are also described; A/ slightly widened and dysplastic acetabulum with milder deformation of the head, B/ intermediately positioned false acetabulum, C/ high position of the false acetabulum, and D/ high nonweight bearing dislocation with the femoral head that has never been in contact with the

The most modern and up-to-now the best classification recommending total arthroplasty in relation to joint deficiency was given by **Hartofilakidis** et al. in 1996, according to which the condition was viewed as acetabular dysplasia, low dislocation and high dislocation

Treatment of the developmental disorder of the hip should be initiated at the moment of the disease detection, and the best results are achieved in the earliest childhood. At that period various forms of non-operative and operative treatments by biological surgeries are possible to be applied. (Vukasinovic & Djoric, 1994; Vukasinovic & Bascarevic, 2004). However, if the treatment is initiated only after the onset of arthrosis or under the conditions of high nonweight bearing hip luxation, operative treatment modalities are only reduced to total hip

The operative procedure is most challenging because of changed anatomical correlations. The topographic correlation of muscles initiators of the hip, joint capsule and neurovascular elements are changed and unstable thus making the operative approach very difficult. The identification of bone structures, primarily of the true acetabulum, is also not at all easy (Lai et al., 1996, 2005; Charnley & Feagin 1973; Crowe et al., 1979; Dunn & Hess, 1976; Eskelinen et al., 2006; Hartofilakidis et al., 1998, 2004, 2008; Holinka et al., 2010; Paavilainen et al.,

The ligamentum transversum is the only reliable parameter determining, not only the height and center of the artificial hip, but also the anteversion (flexion) position of the acetabular

The proximal part of the femoral bone canal is very narrow, with markedly increased anteversion. The acetabular bone mass is underdeveloped, while the bone is insufficiently firm. The joint capsule is elongated, inelastic and thickened, while the surrounding muscles are without any strength, shortened and grown to the capsule. The neurovascular structures are shortened and dislocated from their anatomic positions (Carrlson et al., 2003; Holinka et

In the past there were numerous unsuccessful attempts to perform total hip arthroplasty in adults at the location of high luxation caused by developmental disorder. Exactly due to excessively changed anatomic characteristics of the acetabulum and proximal femur, the operative procedure and the entire surgical concept are most complicated. Therefore, some authors consider high hip luxation as a contraindication for total arthroplasty (Figs.

al., 1979).

iliac bone (Eftekhar 1978).

(Hartofilakidis et al., 1996).

arthroplasty.

1990).

ring.

1, 2, 3).

al., 2010; Paavilainen et al., 1990).

**4. Treatment of high hip dislocation in adults**

Fig. 1a. A 35-year old male after acetabular osteosynthesis performed due to traumatic dislocation of the right hip with superior and posterior acetabular wall fracture.

Fig. 1b.The same patient, six month later high dislocation of the hip occured due to failed osteosynthesis. Full absence of superior and posterior acetabular walls. Leg length discrepancy was 48 mm.

Hip Arthroplasty in Highly Dislocated Hips 159

Fig. 2b. The same patient, one year after bilateral total arthroplasty of the hip with

Fig. 3a. A 30-year old female with bilateral high dislocation of the hips after multiple

restitution of rotation centers.

surgeries due to neonatal sepsis.

Fig. 1c. The same patient, three months after total arthroplasty of the hip, with the osteoplasty of the superior and posterior acetabular walls by solitary bone grafts from the bone bank. Restitution of leg length by positioning the acetabular component into the physiological hip rotation center.

Fig. 2a. A 20-year old female with bilateral secondary arthrosis of the hips due to juvenile rheumatoid arthritis. Bilateral hip subluxation with various disorders of collo-diaphyseal femoral angle.

Fig. 1c. The same patient, three months after total arthroplasty of the hip, with the

physiological hip rotation center.

femoral angle.

osteoplasty of the superior and posterior acetabular walls by solitary bone grafts from the bone bank. Restitution of leg length by positioning the acetabular component into the

Fig. 2a. A 20-year old female with bilateral secondary arthrosis of the hips due to juvenile rheumatoid arthritis. Bilateral hip subluxation with various disorders of collo-diaphyseal

Fig. 2b. The same patient, one year after bilateral total arthroplasty of the hip with restitution of rotation centers.

Fig. 3a. A 30-year old female with bilateral high dislocation of the hips after multiple surgeries due to neonatal sepsis.

Hip Arthroplasty in Highly Dislocated Hips 161

two acts. (Carrlson et al., 2003; Eskelinen et al., 2006; Hartofilakidis et al., 1996; Holinka et

As a part of total arthroplasty, the surgical technique applied to achieve the reduction of a high luxation of the hip without using femoral osteotomy is a relatively rare operative procedure. In the literature it was described by Lai et al. in 1996 and 2005, and then by Holinka et al. in 2010 (Carrlson et al., 2003; Eskelinen et al., 2006; Holinka et al., 2010; Lai et

The leading idea of this surgical procedure is based on the hypothesis that operative procedures with femoral abbreviation osteotomies, regardless of the type, could generally leave a considerable leg-length discrepancy, as well as muscular weakness of hip motion starters. The authors found a back-up for this notion in the articles by Crowe et al., Charnley et al., Dunn et al., Hartofilakidis et al., Paavilainen et al.Eskelinen et al., and others (Charnley & Feagin 1973; Crowe et al., 1979; Dunn & Hess, 1976; Eskelinen et al., 2006;

The operative procedure is performed in two acts. Namely, total arthroplasty is preceded by iliofemoral distraction with the Wagner's apparatus positioned in the ilium and distal femur. Before the distraction, it is necessary to perform subcutaneous adductor tenotomy of the hip, while femoral head resection with a total soft tissue release can be done before the distraction (Holinka et al.) or in the second act, as a part of total arthroplasty (Lai et al.). The distraction is performed gradually, 2-5 mm daily with regular X-ray check-ups and follow-up of neurocircular status of extremities, until the required joint reduction is achieved, bringing the femoral small trochanter into the acetabular teardrop level. During this period the patient is kept in bed. The second surgical act is performed after a few weeks involving removal of the Wagner's distraction apparatus and total arthroplasty of

The principles of total arthroplasty with positioning of the acetabular ring into the paleoacetabulum and the stem in the femoral channel are standard. (Carrlson et al., 2003; Holinka

Such a surgical procedure is very complicated and requires long-term hospitalization and inactivity of the patient. The fact itself that in achieving the goal, total arthroplasty of the hip, requires two operative acts makes it twice riskier for the patient. In addition, the positioning of an extrafocal external apparatus in the area of the hip before arthroplasty might be as such problematic, because of exposing bone tissue to external environment over a long period of time. Strong Schantz screws in the femoral diaphysis can also present areas of decreased biomechanical resistance, particularly as known that the femur is anyway dysplastic in high luxations. Problems can also arise intraoperatively if there is extensive femoral anteversion. Namely, the positioning of a stem of standard geometry under such conditions could prove impossible to perform in the correction of overextensive anteversion. A solution could found in using special stems of small dimensions and/or modular geometry; however, this does not solve the problem of the residual anterior torsion of the

All this is probably the reason why such operative procedure is rarely described in the

**4.1.1 Total hip arthoplasty with iliofemoral distraction in high hip dislocation**

al., 2010; Lai et al., 1996, 2005; Paavilainen et al., 1990).

Fig. 3b. The same patient, one month after total arthroplasty of the left hip with restitution of rotation centers. The leg length equality is expected after the operation of the opposite hip.

#### **4.1 Surgical procedures**

The literature reports many operative techniques for total arthroplasty of the hip in patients with high dislocation. All agree on one point; the center of joint rotation should be restored, meaning that the acetabular component of the implant must be positioned in the primary paleo-acetabulum. This is the only way to expect good joint function, being the only mode to establish the physiological distance between the ends of the muscular initiators of hip motion, thus enabling their full strength. However, there is no full agreement as to the preparation and positioning of the proximal femur at the required level of the primary acetabulum (Carrlson et al., 2003; Crowe et al., 1979; Dunn & Hess, 1976; Eskelinen et al., 2006; Hartofilakidis et al., 1996, 1998, 2004; Holinka et al., 2010; Lai et al., 1996, 2005; Paavilainen et al., 1990).

Many surgical techniques have been described by authors discussing the type and modes of femoral abbreviation osteotomies. Some of them are performed through the very trochanteric mass (midtrochanteric), while others are done below it (subtrochanteric), with various forms of resection osteotomies with or without fixation of the proximal fragment or great trochanter. Some authors achieve the adequate position of the femur in correlation to paleo-acetabulum by extrafocal distraction after the resection of the joint. Arthroplasty is to follow as a new operative technique, where the entire operative procedure is performed in

Fig. 3b. The same patient, one month after total arthroplasty of the left hip with restitution of rotation centers. The leg length equality is expected after the operation of the opposite

The literature reports many operative techniques for total arthroplasty of the hip in patients with high dislocation. All agree on one point; the center of joint rotation should be restored, meaning that the acetabular component of the implant must be positioned in the primary paleo-acetabulum. This is the only way to expect good joint function, being the only mode to establish the physiological distance between the ends of the muscular initiators of hip motion, thus enabling their full strength. However, there is no full agreement as to the preparation and positioning of the proximal femur at the required level of the primary acetabulum (Carrlson et al., 2003; Crowe et al., 1979; Dunn & Hess, 1976; Eskelinen et al., 2006; Hartofilakidis et al., 1996, 1998, 2004; Holinka et al., 2010; Lai et al., 1996, 2005;

Many surgical techniques have been described by authors discussing the type and modes of femoral abbreviation osteotomies. Some of them are performed through the very trochanteric mass (midtrochanteric), while others are done below it (subtrochanteric), with various forms of resection osteotomies with or without fixation of the proximal fragment or great trochanter. Some authors achieve the adequate position of the femur in correlation to paleo-acetabulum by extrafocal distraction after the resection of the joint. Arthroplasty is to follow as a new operative technique, where the entire operative procedure is performed in

hip.

**4.1 Surgical procedures**

Paavilainen et al., 1990).

two acts. (Carrlson et al., 2003; Eskelinen et al., 2006; Hartofilakidis et al., 1996; Holinka et al., 2010; Lai et al., 1996, 2005; Paavilainen et al., 1990).

## **4.1.1 Total hip arthoplasty with iliofemoral distraction in high hip dislocation**

As a part of total arthroplasty, the surgical technique applied to achieve the reduction of a high luxation of the hip without using femoral osteotomy is a relatively rare operative procedure. In the literature it was described by Lai et al. in 1996 and 2005, and then by Holinka et al. in 2010 (Carrlson et al., 2003; Eskelinen et al., 2006; Holinka et al., 2010; Lai et al., 1996, 2005).

The leading idea of this surgical procedure is based on the hypothesis that operative procedures with femoral abbreviation osteotomies, regardless of the type, could generally leave a considerable leg-length discrepancy, as well as muscular weakness of hip motion starters. The authors found a back-up for this notion in the articles by Crowe et al., Charnley et al., Dunn et al., Hartofilakidis et al., Paavilainen et al.Eskelinen et al., and others (Charnley & Feagin 1973; Crowe et al., 1979; Dunn & Hess, 1976; Eskelinen et al., 2006; Hartofilakidis et al., 1998; Paavilainen et al., 1990).

The operative procedure is performed in two acts. Namely, total arthroplasty is preceded by iliofemoral distraction with the Wagner's apparatus positioned in the ilium and distal femur. Before the distraction, it is necessary to perform subcutaneous adductor tenotomy of the hip, while femoral head resection with a total soft tissue release can be done before the distraction (Holinka et al.) or in the second act, as a part of total arthroplasty (Lai et al.). The distraction is performed gradually, 2-5 mm daily with regular X-ray check-ups and follow-up of neurocircular status of extremities, until the required joint reduction is achieved, bringing the femoral small trochanter into the acetabular teardrop level. During this period the patient is kept in bed. The second surgical act is performed after a few weeks involving removal of the Wagner's distraction apparatus and total arthroplasty of the hip.

The principles of total arthroplasty with positioning of the acetabular ring into the paleoacetabulum and the stem in the femoral channel are standard. (Carrlson et al., 2003; Holinka et al., 2010; Lai et al., 1996, 2005; Paavilainen et al., 1990).

Such a surgical procedure is very complicated and requires long-term hospitalization and inactivity of the patient. The fact itself that in achieving the goal, total arthroplasty of the hip, requires two operative acts makes it twice riskier for the patient. In addition, the positioning of an extrafocal external apparatus in the area of the hip before arthroplasty might be as such problematic, because of exposing bone tissue to external environment over a long period of time. Strong Schantz screws in the femoral diaphysis can also present areas of decreased biomechanical resistance, particularly as known that the femur is anyway dysplastic in high luxations. Problems can also arise intraoperatively if there is extensive femoral anteversion. Namely, the positioning of a stem of standard geometry under such conditions could prove impossible to perform in the correction of overextensive anteversion. A solution could found in using special stems of small dimensions and/or modular geometry; however, this does not solve the problem of the residual anterior torsion of the femoral neck.

All this is probably the reason why such operative procedure is rarely described in the literature.

Hip Arthroplasty in Highly Dislocated Hips 163

has undergone minor modifications. The essence has remained identical, only some details were changed regarding the extent of capsular excision and the mode of femoral osteotomy. Namely, today we do not excise the entire joint capsule, although it is cautiously prepared and freed from attached muscles, while the stability of the femoral segments is achieved by the adapted transverse osteotomy and implantation of the standard stem with distal rotational stability. Also, over the last 11 years, with the emergence of new implants, above all hemispheric press-fit acetabular rings, the need for acetabuloplasty, which was almost regularly applied at the time of screw ring usage, nowadays is almost nonexistent (Radojevic & Zlatic, 1990; Tabak et al., 2003; Zlatic et al.,

The relaxation of the neuromuscular elements is achieved by the postoperative positioning of the leg with the hip and the knee in flexion which is individually adapted to each patient. Gradual stretching is done during the next days and last on average for 2- 3 days. Only then the patient is allowed to stand up and to begin walking. Individually tolerant weight bearing on the operated leg is immediately allowed. Discarding the crutches is also done on individual basis, above all depending on the patient's capability to achieve a stabile weight bearing within a given time. Certainly, osteotomy bone consolidation and the incorporation of endoprosthetic components also contribute to the decision on when walking supports could be discarded. Thromboembolic profilactic therapy is applied with low molecular weight heparine from the day of surgery until

Fig. 4a. A 35-year old female with bilateral high dislocation of the hips due to DDH.

1990).

elapsed 35 postsurgical days (Fig. 4).

## **4.1.2 Total hip arthoplasty with femoral abbreviation osteotomies**

Today there are basically two operative techniques for total arthroplasty of the hip in high luxations with femoral abbreviation osteotomies, and both are based on osteotomies in the subtrochanteric region.

One technique involves resection of a larger part of the trochanter mass, hence the entire metaphysis and a portion of diaphysis, with preservation of the great trochanter with abductor attachments, while by other operative procedures resection osteotomy is performed only on the diaphysis below the small trochanter, with the metaphysis remaining preserved.

Femoral abbreviation osteotomies in total arthroplasty of the hip, particularly when treating high luxations due to DDH, have been described by numerous authors (Dunn et al., 1976; Crowe et al., 1979 ; Paavilainen at al., 1990, 1993; Hartofilakidis et al., 1996, 1998, 2004, 2008 ; Papagelopoulos et al., 1996; Numair et al., 1997; Carrlson et al., 2003).

The original operative technique by Paavilainen et al. has been slightly modified by Carlsson et al., but basic postulates have remained the same. After exposing the hip through the posterolateral approach, abbreviation osteotomy of the proximal femur is performed at two levels, horizontal and sagittal. The diaphysis is osteotomized transversally 7-9 cm below the top of the great trochanter, and then osteotomy of the proximal fragment at the sagittal level is performed, thus leavening abductor attachments of the hip, primarily of the gluteus medius in the lateral part, which basically represents the great trochanter. The remaining portion of the proximal fragment is removed, i.e. if necessary it can be used as a graft. The conical stem of small dimensions is implanted into the distal fragment, namely directly into the femoral diaphysis. After having positioned the acetabular component of the endoprosthesis, the remaining proximal fragment is lowered onto the proximal portion of the diaphysis and fixed with screws and/or wire serclages. Walking with partial weightbearing is immediately allowed, while full weight-bearing can be allowed after two months (Paavilainen at al., 1990, 1993; Carrlson et al., 2003).

This operative procedure has the advantage over those described above primarily because arthroplasty of the hip is performed in one act. Hospital stay is much shorter, with more rapid rehabilitation and without any significant limitation as to weight-bearing. Although osteotomy of the proximal femur is done, the function of the gluteus medius remains preserved. Rather, its strength is reinstituted with the distalization of the trochanter attachments.

Theoretically, the problem of this operative procedure might be non-healing of the great trochanter dislocated onto the diaphysis, however, authors have reported no such incidence in any of the cases. Also, theoretically, a delayed problem of potential revisional surgery might present a full loss of the metaphyseal bone of the proximal femur. The necessity to use a slightly more specific dysplastic stems, i.e. the impossibility of standard femoral implants (due to absent metaphyseal) does not present a true problem if taken into consideration a relatively small number of patients with such a condition.

At the Institute of Orthopaedic Surgery "Banjica" in Belgrade, high dislocation of the hip in adults is treated by transverse subtrochanteric abbreviational femoral osteotomy and, of course, a mandatory implantation of the acetabular component into the primary acetabulum. The operative technique was developed in 1984, however, over the time it

Today there are basically two operative techniques for total arthroplasty of the hip in high luxations with femoral abbreviation osteotomies, and both are based on osteotomies in the

One technique involves resection of a larger part of the trochanter mass, hence the entire metaphysis and a portion of diaphysis, with preservation of the great trochanter with abductor attachments, while by other operative procedures resection osteotomy is performed only on the diaphysis below the small trochanter, with the metaphysis remaining

Femoral abbreviation osteotomies in total arthroplasty of the hip, particularly when treating high luxations due to DDH, have been described by numerous authors (Dunn et al., 1976; Crowe et al., 1979 ; Paavilainen at al., 1990, 1993; Hartofilakidis et al., 1996, 1998, 2004, 2008 ;

The original operative technique by Paavilainen et al. has been slightly modified by Carlsson et al., but basic postulates have remained the same. After exposing the hip through the posterolateral approach, abbreviation osteotomy of the proximal femur is performed at two levels, horizontal and sagittal. The diaphysis is osteotomized transversally 7-9 cm below the top of the great trochanter, and then osteotomy of the proximal fragment at the sagittal level is performed, thus leavening abductor attachments of the hip, primarily of the gluteus medius in the lateral part, which basically represents the great trochanter. The remaining portion of the proximal fragment is removed, i.e. if necessary it can be used as a graft. The conical stem of small dimensions is implanted into the distal fragment, namely directly into the femoral diaphysis. After having positioned the acetabular component of the endoprosthesis, the remaining proximal fragment is lowered onto the proximal portion of the diaphysis and fixed with screws and/or wire serclages. Walking with partial weightbearing is immediately allowed, while full weight-bearing can be allowed after two months

This operative procedure has the advantage over those described above primarily because arthroplasty of the hip is performed in one act. Hospital stay is much shorter, with more rapid rehabilitation and without any significant limitation as to weight-bearing. Although osteotomy of the proximal femur is done, the function of the gluteus medius remains preserved. Rather, its strength is reinstituted with the distalization of the trochanter

Theoretically, the problem of this operative procedure might be non-healing of the great trochanter dislocated onto the diaphysis, however, authors have reported no such incidence in any of the cases. Also, theoretically, a delayed problem of potential revisional surgery might present a full loss of the metaphyseal bone of the proximal femur. The necessity to use a slightly more specific dysplastic stems, i.e. the impossibility of standard femoral implants (due to absent metaphyseal) does not present a true problem if taken into consideration a relatively small number of patients with such a

At the Institute of Orthopaedic Surgery "Banjica" in Belgrade, high dislocation of the hip in adults is treated by transverse subtrochanteric abbreviational femoral osteotomy and, of course, a mandatory implantation of the acetabular component into the primary acetabulum. The operative technique was developed in 1984, however, over the time it

**4.1.2 Total hip arthoplasty with femoral abbreviation osteotomies**

Papagelopoulos et al., 1996; Numair et al., 1997; Carrlson et al., 2003).

(Paavilainen at al., 1990, 1993; Carrlson et al., 2003).

subtrochanteric region.

preserved.

attachments.

condition.

has undergone minor modifications. The essence has remained identical, only some details were changed regarding the extent of capsular excision and the mode of femoral osteotomy. Namely, today we do not excise the entire joint capsule, although it is cautiously prepared and freed from attached muscles, while the stability of the femoral segments is achieved by the adapted transverse osteotomy and implantation of the standard stem with distal rotational stability. Also, over the last 11 years, with the emergence of new implants, above all hemispheric press-fit acetabular rings, the need for acetabuloplasty, which was almost regularly applied at the time of screw ring usage, nowadays is almost nonexistent (Radojevic & Zlatic, 1990; Tabak et al., 2003; Zlatic et al., 1990).

The relaxation of the neuromuscular elements is achieved by the postoperative positioning of the leg with the hip and the knee in flexion which is individually adapted to each patient. Gradual stretching is done during the next days and last on average for 2- 3 days. Only then the patient is allowed to stand up and to begin walking. Individually tolerant weight bearing on the operated leg is immediately allowed. Discarding the crutches is also done on individual basis, above all depending on the patient's capability to achieve a stabile weight bearing within a given time. Certainly, osteotomy bone consolidation and the incorporation of endoprosthetic components also contribute to the decision on when walking supports could be discarded. Thromboembolic profilactic therapy is applied with low molecular weight heparine from the day of surgery until elapsed 35 postsurgical days (Fig. 4).

Fig. 4a. A 35-year old female with bilateral high dislocation of the hips due to DDH.

Hip Arthroplasty in Highly Dislocated Hips 165

Fig. 4d. The same patient, 18 months after right total hip arthroplasty and nine month after

As can be seen, all previously described operative techniques for high hip luxation

According to our opinion both operative techniques with femoral abbreviation osteotomies have significant advantages over two-act operative procedures. The theoretical advantage of the latter described operative technique, with diaphyseal subtrochateric resection, over the former ones, with diaphyseal and metaphyseal resection, could be in the preservation of the bone metaphysis of the proximal femur with the possibility to use the standard midcoated implants without distal ingrowing and without additional fixation. On the other hand, the advantage of the former technique could refer to the healing of osteotomized fragments. Namely, a potentially delayed healing, and even non-healing of diaphyseal and metaphyseal bones in the subtrochanteric region is more probable than the fusion of firmly

This work was supported by Ministry of Education and Science, Republic of Serbia (Grant

Ando, M, Gotoh, E. (1990). Significance of inguinal folds for diagnosis of congenital

No. 3, (May-Jun 1990) pp. (331-334), ISSN 0271-6798

dislocation of the hip in infants aged three to four mounts. *J Pediatr Orthop*, Vol. 10,

treatment with total hip arthroplasty are reliable in hands of experienced surgeons.

left total hip artroplasty. Both osteotomies were fully consolidated.

**5. Conclusion**

fixed great trochanter to the diaphysis.

**6. Acknowledgment**

No. 41004).

**7. References**

Fig. 4b. The same patient, nine months after total arthroplasty of the right hip. Good bone consolidation after four centimetres shortening subtrochanteric osteotomy.

Fig. 4c. The same patient, three months after left hip arthroplasty with abreviation subtrochanteric osteotomy. Leg length equality established. Bone consolidation in progress, femoral stem stable.

Fig. 4b. The same patient, nine months after total arthroplasty of the right hip. Good bone

consolidation after four centimetres shortening subtrochanteric osteotomy.

Fig. 4c. The same patient, three months after left hip arthroplasty with abreviation

femoral stem stable.

subtrochanteric osteotomy. Leg length equality established. Bone consolidation in progress,

Fig. 4d. The same patient, 18 months after right total hip arthroplasty and nine month after left total hip artroplasty. Both osteotomies were fully consolidated.

## **5. Conclusion**

As can be seen, all previously described operative techniques for high hip luxation treatment with total hip arthroplasty are reliable in hands of experienced surgeons. According to our opinion both operative techniques with femoral abbreviation osteotomies have significant advantages over two-act operative procedures. The theoretical advantage of the latter described operative technique, with diaphyseal subtrochateric resection, over the former ones, with diaphyseal and metaphyseal resection, could be in the preservation of the bone metaphysis of the proximal femur with the possibility to use the standard midcoated implants without distal ingrowing and without additional fixation. On the other hand, the advantage of the former technique could refer to the healing of osteotomized fragments. Namely, a potentially delayed healing, and even non-healing of diaphyseal and metaphyseal bones in the subtrochanteric region is more probable than the fusion of firmly fixed great trochanter to the diaphysis.

## **6. Acknowledgment**

This work was supported by Ministry of Education and Science, Republic of Serbia (Grant No. 41004).

## **7. References**

Ando, M, Gotoh, E. (1990). Significance of inguinal folds for diagnosis of congenital dislocation of the hip in infants aged three to four mounts. *J Pediatr Orthop*, Vol. 10, No. 3, (May-Jun 1990) pp. (331-334), ISSN 0271-6798

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Hartofilakidis, G, Stamos, K, Karachalios, T, Ioannidis, TT, Zacharakis, N. (1996). Congenital

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Lai, KA, Shen, WJ, Huang, LW, Chen, MY. (2005). Cementless total hip arthroplasty and

Maric, Z, Haynes, RJ. (1993). Total hip arthroplasty in juvenile rheumatoid arthritis. *Clin*

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Papachristou, G, Hatzigrigoris, P, Panousis, K, Plessas, S, Sourlas, J, Levidiotis, C,

Pitto, RP, Schikora, N. (2004). Acetabular reconstruction in developmental hip dysplasia

Radojevic, B, Zlatic, M. (1990). An L-shaped bone graft for acetabular deficiency. *J Bone Joint Surg Br,* Vol. 72, No. 1, (January 1990), pp. (152-153), ISSN 0301-620X Ruddlesdin, C, Ansell, BM, Arden, GP, Swann, M. (1986). Total hip replacement in children

Tabak, AY, Celebi, L, Muratli, H, Yagmurlu, F, Aktekin, C, Bicimoglu, A. (2003). Cementless

*Int Orthop,* Vol. 30, No. 1, (February 2006), pp. (21–25), ISSN 0341-2695 Papagelopoulos, P, Trousdale, RT, Lewallen, DG. (1996). Cementless total hip arthroplasty

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replacement in congenital high hip dislocation following iliofemoralmonotube distraction. *Int Orthop*, Vol. 35, No. 5, (March 2010), pp. (639-645), ISSN 0341-2695 Klisic, P. (1989). Congenital dislocation of the hip: a misleading term. *J Bone Joint Surg,* Vol.

dislocation of the hip before total hip arthroplasty. *J Arthoplasty,* Vol.11, No. 5,

limb-length equalization in patients with unilateral Crowe type-IV hip dislocation. J *Bone Joint Surg Am,* Vol. 87, No. 2, (February 2005), pp. (339-345), ISSN 0021-9355 Learmonth, ID, Heywood, AW, Kaye, J, Dall, D. (1989). Radiological loosening after

cemented hip replacement for juvenile chronic arthritis. *J Bone Joint Surg Br,* Vol. 71,

congenital dysplasia or dislocation of the hip. Survivorship analysis and long-term results. *J Bone Joint Surg Am,* Vol. 79, No. 9, (September 1997), pp. (1352–1360), ISSN

dysplastic or dislocated hips. *J Bone Joint Surg Br,* Vol. 72, No. 2, (March 1990), pp.

Chronopoulos, E. (2006). Total hip arthroplasty for developmental hip dysplasia.

with femoral osteotomy for proximal femoral deformity. *Clin Orthop,* Vol. 332, No.

using reinforcement ring with a hook*. Int Orthop,* Vol. 28, No. 4, (August 2004), pp.

with juvenile chronic arthritis*. J Bone Joint Surg Br,* Vol. 68, No. 2, (March 1986), pp.

total hip replacement in patients with high total dislocation: the results of femoral

Bascarevic Z, Vukasinovic Z, Slavkovic N, Dulic B, Trajkovic G, Bascarevic V, Timotijevic S.

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Cherney, D, Westin, G. (1989). Acetabular development in the infants dislocated hips. *Clin Orthop Relat Res*, Vol. 242, No. 5, (May 1989), pp. (98-103), ISSN 0009-921X Choi IH, Pizzutillo PD, Bowen JR, Dragann R, Malhis T. (1990). Sequelae and reconstruction

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**11**

*Slovenia*

**Modular Femoral Neck Fracture**

In the middle of the 20th century total hip arthroplasty (THA) became the most popular and the most common reconstructive procedure of the hip. It is important as a last resort in treatment of terrible pain due to progressive hip arthritis of different etiologies. Implanting an artificial hip prosthesis, the surgeon helps the patient by releasing the pain and restoring

Historically, treatment of progressive osteoarthritis evolved from arthrodesis through different osteotomies, nerve divisions, joint debridements, and interpositions of different organic or inorganic materials between the articular surfaces, towards the final introduction of total hip endoprosthesis. The first endoprostheses were made of glass. Afterwards the quality of the materials progressed from plastic, steel, to cobalt-chromium alloys and finally titanium alloys. Additionally, considerable effort was made to improve the manufacturing techniques, hip biomechanics and the usage of appropriate materials (Harkess & Crockarell, 2007). The studies of materials revealed that orthopaedic implants must be biocompatible; they have to resist all forms of corrosion (Sharan, 1999), resist degradation and withstand all forces that potentially apply. Different designs of total hip endoprostheses follow different philosophies. Two kinds of prosthesis designs are currently used in primary hip arthroplasty. Monoblock is a femoral stem prosthesis made of a single piece, while modular prostheses are made of two modules: the femoral stem and the femoral neck. The stem can be of different sizes, and the neck is of different sizes and different neck angle versions. According to the American Academy of Orthopaedic Surgeons (AAOS), more than 193,000 total hip replacements are performed yearly in the United States alone. The prediction for the US is that the number of total hip replacements will at least double by the year 2030

Modular neck hip prosthesis has been gaining popularity worldwide for the last thirty years. Modular stems are commonly used in revision hip surgery. The use of this kind of endoprosthesis was first published in 1948 by McBride, then later by Bousquet and Bornard in 1978. Several companies presently offer different versions of modular neck hip endoprostheses for primary total hip arthroplasty (Keppler, 2006). The advantage of this type of endoprosthesis is that the surgeon has an intraoperative choice of neck version and

the range of movement so that the patient can resume his normal activities.

**1. Introduction**

(Wilson N., 2008).

**2. Modular neck hip prosthesis**

**After Total Hip Arthroplasty**

Igor Vučajnk and Samo K. Fokter *Celje General and Teaching Hospital*

shortening by subtrochanteric segmental resection. *Acta Orthop Traumatol Turc,* Vol. 37, No.4, (April 2003), pp. (277-283), ISSN 1017-995x

## **Modular Femoral Neck Fracture After Total Hip Arthroplasty**

Igor Vučajnk and Samo K. Fokter *Celje General and Teaching Hospital Slovenia*

## **1. Introduction**

168 Recent Advances in Hip and Knee Arthroplasty

Vukasinovic, Z, Bascarevic, Z. (2004). Diseases of the infant hip, In: *Special orthopaedics*,

Vukasinovic, Z, Djoric, I. (1994). Developmental disorder of the hip, In: *Hip diseases in*

Kim YH, Seo HS, Kim JS. (2009). Outcomes after THA in patients with high hip after

Zlatic, M, Radojevic, B, Lazovic, C. (1990). Reconstruction of the hipoplastyc acetabulum in

37, No.4, (April 2003), pp. (277-283), ISSN 1017-995x

ISBN 86-82411-04-0, Belgrade

2378), ISSN 0009-921X

375), ISSN 0341-2695

Belgrade, ISBN 86-82411-01-6, Belgrade

shortening by subtrochanteric segmental resection. *Acta Orthop Traumatol Turc,* Vol.

Vukasinovic Z, pp (237-273), Institute for orthopaedic diseases "Banjica" Belgrade,

*childhood*, Vukasinovic Z, pp. (37-78), Special orthopeadic hospital "Banjica"

childhood sepsis. *Clin Orthop Relat Res,* Vol. 467, No. 9, (September 2009), pp. (2371-

cementless arthroplasty of the hip. *Int Orthop,*Vol. 14, No.4, (April 1990), pp. (371-

In the middle of the 20th century total hip arthroplasty (THA) became the most popular and the most common reconstructive procedure of the hip. It is important as a last resort in treatment of terrible pain due to progressive hip arthritis of different etiologies. Implanting an artificial hip prosthesis, the surgeon helps the patient by releasing the pain and restoring the range of movement so that the patient can resume his normal activities.

Historically, treatment of progressive osteoarthritis evolved from arthrodesis through different osteotomies, nerve divisions, joint debridements, and interpositions of different organic or inorganic materials between the articular surfaces, towards the final introduction of total hip endoprosthesis. The first endoprostheses were made of glass. Afterwards the quality of the materials progressed from plastic, steel, to cobalt-chromium alloys and finally titanium alloys. Additionally, considerable effort was made to improve the manufacturing techniques, hip biomechanics and the usage of appropriate materials (Harkess & Crockarell, 2007). The studies of materials revealed that orthopaedic implants must be biocompatible; they have to resist all forms of corrosion (Sharan, 1999), resist degradation and withstand all forces that potentially apply. Different designs of total hip endoprostheses follow different philosophies. Two kinds of prosthesis designs are currently used in primary hip arthroplasty. Monoblock is a femoral stem prosthesis made of a single piece, while modular prostheses are made of two modules: the femoral stem and the femoral neck. The stem can be of different sizes, and the neck is of different sizes and different neck angle versions.

According to the American Academy of Orthopaedic Surgeons (AAOS), more than 193,000 total hip replacements are performed yearly in the United States alone. The prediction for the US is that the number of total hip replacements will at least double by the year 2030 (Wilson N., 2008).

#### **2. Modular neck hip prosthesis**

Modular neck hip prosthesis has been gaining popularity worldwide for the last thirty years. Modular stems are commonly used in revision hip surgery. The use of this kind of endoprosthesis was first published in 1948 by McBride, then later by Bousquet and Bornard in 1978. Several companies presently offer different versions of modular neck hip endoprostheses for primary total hip arthroplasty (Keppler, 2006). The advantage of this type of endoprosthesis is that the surgeon has an intraoperative choice of neck version and

Modular Femoral Neck Fracture After Total Hip Arthroplasty 171

modularity gives important advantage for fine adjustments of leg length and femoral

The materials used for modular femoral stem and modular neck are made of cobalt alloys (Co-Cr-Mo; cobalt-chromium-molybdenum) and of titanium alloys (Ti-6Al-4V; titaniumaluminium-vanadium). Cobalt alloys are among the strongest materials used for implants and can resist high-loading. The added molybdenum increases the strength even more. Chromium is added for hardness and makes the alloy more resistant to corrosion. The unique property of titanium alloys is their tissue biocompatibility. Corrosion is very limited in titanium alloys and they resist to crevice corrosion because they form a passive layer of oxide films (titanium oxide) on their surface. The biomaterials used have to resist crevice corrosion, fretting corrosion, galvanic corrosion, and pitting corrosion in order to withstand the degradation process. Also, the materials must have proper mechanical and wear

An increasing number of recently published case reports and studies describe catastrophic failures of modular femoral neck prostheses resulting from material fracture. The Swedish Hip Arthroplasty Register Annual Report of femoral hip stems noted overall femoral stem implant failure in 493 prostheses out of the 299,368 primary hip arthroplasties performed from 1979 to 2008 (1.4%) (Garellick et al., 2009). A report on the Metha Short Hip Stem Prosthesis (Aesculap AG, Tuttlingen, Germany) also showed a 1.4% failure rate of modular necks (68 neck failures out of 5000 THA) (Grupp, 2010). According to the Wright Company, the Profemur (Profemur Z, Wright Medical Technology, Inc., Arlington, TN, USA) modular neck fracture rate in 198,331 implanted endoprostheses has been calculated to 0.028% (Wright Medical Technology Inc., 2010). The Profemur world wide fracture rate in all necks, including long and short necks is reported to be 0.058% (6 fractures out of every 10,000 THA) (Wright Medical Technology Inc., 2010). Both in Wright and in Aesculap, the necks were made of titanium alloys. This complication is supposed to occur in almost all cases with long necks, heavier patients and male patients. Both studies concluded that titanium long necks should be replaced with cobalt chrome alloy necks because they are safer (Wright Medical Technologies Inc., 2010; Grupp, 2010). The Zimmer Company reviewed over 300,000 primary VerSys prostheses (VerSys Hip System, Zimmer Inc., Warsaw, IN, USA) implanted since the year 2000 and their fracture rate was less than 0.0018% (Hertzler et al., 2009). A center implanting Acumatch M-series cementless hip endoprostheses (Acumatch M-series, Exactech Inc., Gainesville, Florida, USA) reported on fracture rates of

There are many reasons for prosthesis fracture. As mentioned in the previous section, orthopaedic implants are subject to crevice corrosion, fretting corrosion, galvanic corrosion and pitting corrosion (Sharan, 1999). The changing demographics of the patients undergoing total hip replacement surgeries could also contribute to the fracture rates. These include increased patient weight, increased physical activities, increased life expectancy, and the

Fretting is a phenomenon which occurs between two contacting bodies experiencing reciprocating motion. In our case small scale reciprocating movements occur between the femoral stem and the femoral neck at the taper junction. When the main factor causing

1.6% (8 fractures out of 500 implanted prostheses) (Paliwal, 2010).

timing of the operation (Chrowninshield, 2006).

anteversion.

properties.

**5. Modular neck fracture**

neck length independently of the stem size. The surgeon can then adjust the femoral offset, correct leg length and achieve hip stability.

Modular hip endoprostheses can be classified as proximal, mid-stem, distal and multimodular. The proximal ones have modules for sleeve, shoulder and neck, neck, collars and proximal pads (Froehlich, 2006). In this chapter we focus on proximal modular neck endoprostheses.

Important differences exist between the two sexes in femoral neck length, femoral shaft diameter, collum-caput-diaphysis angle (CCD), neck version and offset (Traina, 2009). In order to properly restore the hip biomechanics these parameters must be kept in mind. Appropriate restoration of femoral offset and appropriate soft tissue balancing is necessary. Unsatisfactory restoration of hip biomechanics can and will lead to limping, abductor muscle imbalances, and higher rates of wearing. In order to achieve the best biomechanics of the reconstructed hip, preoperative planning is essential. However, as the femoral version cannot be appropriately and adequately assessed with standard radiographs, modular hip prosthesis offers some advantage during the operation. In addition, some benefits of modular neck hip prosthesis in developmental dysplasia of the hip (DDH) have been reported. One study showed that monoblock stems restore offset in only one out of three patients. Eight different neck shaft angle solutions are necessary to restore the anatomy in 50% of the patients (Massin, 2000).

#### **3. Complications associated with modular neck hip prosthesis**

The complications associated with modular neck hip arthroplasty are divided in medical complications and complications associated with surgery and materials. Medical complications, such as cardiovascular, thromboembolic, pulmonary, anaemic and renal complications as well as delirium can be prevented or at least minimized with careful preoperative risk assessment and proper perioperative care (Foerg, 2005). Other complications including joint infection, nerve and blood vessel injury, and bleeding during or after the surgery can be reduced by proper operative techniques. Leg length inequality, prosthesis dislocation, and prosthesis impingement can be prevented with a proper choice of offset and neck version. The highly corrosive environment of the human body demands the use of such biomaterials which will withstand degradation that could lead to another serious complication – failure of the prosthetic material.

Instability is the second most common complication after aseptic loosening (Abraham, 2005). Dislocation rates vary among reports from 0.5% to 11%. The risk of dislocation is associated with time from the operation and with traumatic events, polyethylene wear and pseudocapsule laxity.

#### **4. Prosthesis size and materials**

Modular neck hip endoprostheses are made of different numbers of modules. The prosthesis used for primary THA is made of two modules, the femoral stem and the femoral modular neck. The femoral stem comes in different sizes in order to fit different femoral dimensions. The numbers of stem sizes differ from one manufacturer to the other. The femoral neck comes in different sizes and versions as well, and the number again depends on the manufacturer. The two modules connect at the stem neck junction called the taper. The modularity gives important advantage for fine adjustments of leg length and femoral anteversion.

The materials used for modular femoral stem and modular neck are made of cobalt alloys (Co-Cr-Mo; cobalt-chromium-molybdenum) and of titanium alloys (Ti-6Al-4V; titaniumaluminium-vanadium). Cobalt alloys are among the strongest materials used for implants and can resist high-loading. The added molybdenum increases the strength even more. Chromium is added for hardness and makes the alloy more resistant to corrosion. The unique property of titanium alloys is their tissue biocompatibility. Corrosion is very limited in titanium alloys and they resist to crevice corrosion because they form a passive layer of oxide films (titanium oxide) on their surface. The biomaterials used have to resist crevice corrosion, fretting corrosion, galvanic corrosion, and pitting corrosion in order to withstand the degradation process. Also, the materials must have proper mechanical and wear properties.

## **5. Modular neck fracture**

170 Recent Advances in Hip and Knee Arthroplasty

neck length independently of the stem size. The surgeon can then adjust the femoral offset,

Modular hip endoprostheses can be classified as proximal, mid-stem, distal and multimodular. The proximal ones have modules for sleeve, shoulder and neck, neck, collars and proximal pads (Froehlich, 2006). In this chapter we focus on proximal modular neck

Important differences exist between the two sexes in femoral neck length, femoral shaft diameter, collum-caput-diaphysis angle (CCD), neck version and offset (Traina, 2009). In order to properly restore the hip biomechanics these parameters must be kept in mind. Appropriate restoration of femoral offset and appropriate soft tissue balancing is necessary. Unsatisfactory restoration of hip biomechanics can and will lead to limping, abductor muscle imbalances, and higher rates of wearing. In order to achieve the best biomechanics of the reconstructed hip, preoperative planning is essential. However, as the femoral version cannot be appropriately and adequately assessed with standard radiographs, modular hip prosthesis offers some advantage during the operation. In addition, some benefits of modular neck hip prosthesis in developmental dysplasia of the hip (DDH) have been reported. One study showed that monoblock stems restore offset in only one out of three patients. Eight different neck shaft angle solutions are necessary to restore the anatomy in

The complications associated with modular neck hip arthroplasty are divided in medical complications and complications associated with surgery and materials. Medical complications, such as cardiovascular, thromboembolic, pulmonary, anaemic and renal complications as well as delirium can be prevented or at least minimized with careful preoperative risk assessment and proper perioperative care (Foerg, 2005). Other complications including joint infection, nerve and blood vessel injury, and bleeding during or after the surgery can be reduced by proper operative techniques. Leg length inequality, prosthesis dislocation, and prosthesis impingement can be prevented with a proper choice of offset and neck version. The highly corrosive environment of the human body demands the use of such biomaterials which will withstand degradation that could lead to another

Instability is the second most common complication after aseptic loosening (Abraham, 2005). Dislocation rates vary among reports from 0.5% to 11%. The risk of dislocation is associated with time from the operation and with traumatic events, polyethylene wear and

Modular neck hip endoprostheses are made of different numbers of modules. The prosthesis used for primary THA is made of two modules, the femoral stem and the femoral modular neck. The femoral stem comes in different sizes in order to fit different femoral dimensions. The numbers of stem sizes differ from one manufacturer to the other. The femoral neck comes in different sizes and versions as well, and the number again depends on the manufacturer. The two modules connect at the stem neck junction called the taper. The

**3. Complications associated with modular neck hip prosthesis**

serious complication – failure of the prosthetic material.

correct leg length and achieve hip stability.

50% of the patients (Massin, 2000).

pseudocapsule laxity.

**4. Prosthesis size and materials**

endoprostheses.

An increasing number of recently published case reports and studies describe catastrophic failures of modular femoral neck prostheses resulting from material fracture. The Swedish Hip Arthroplasty Register Annual Report of femoral hip stems noted overall femoral stem implant failure in 493 prostheses out of the 299,368 primary hip arthroplasties performed from 1979 to 2008 (1.4%) (Garellick et al., 2009). A report on the Metha Short Hip Stem Prosthesis (Aesculap AG, Tuttlingen, Germany) also showed a 1.4% failure rate of modular necks (68 neck failures out of 5000 THA) (Grupp, 2010). According to the Wright Company, the Profemur (Profemur Z, Wright Medical Technology, Inc., Arlington, TN, USA) modular neck fracture rate in 198,331 implanted endoprostheses has been calculated to 0.028% (Wright Medical Technology Inc., 2010). The Profemur world wide fracture rate in all necks, including long and short necks is reported to be 0.058% (6 fractures out of every 10,000 THA) (Wright Medical Technology Inc., 2010). Both in Wright and in Aesculap, the necks were made of titanium alloys. This complication is supposed to occur in almost all cases with long necks, heavier patients and male patients. Both studies concluded that titanium long necks should be replaced with cobalt chrome alloy necks because they are safer (Wright Medical Technologies Inc., 2010; Grupp, 2010). The Zimmer Company reviewed over 300,000 primary VerSys prostheses (VerSys Hip System, Zimmer Inc., Warsaw, IN, USA) implanted since the year 2000 and their fracture rate was less than 0.0018% (Hertzler et al., 2009). A center implanting Acumatch M-series cementless hip endoprostheses (Acumatch M-series, Exactech Inc., Gainesville, Florida, USA) reported on fracture rates of 1.6% (8 fractures out of 500 implanted prostheses) (Paliwal, 2010).

There are many reasons for prosthesis fracture. As mentioned in the previous section, orthopaedic implants are subject to crevice corrosion, fretting corrosion, galvanic corrosion and pitting corrosion (Sharan, 1999). The changing demographics of the patients undergoing total hip replacement surgeries could also contribute to the fracture rates. These include increased patient weight, increased physical activities, increased life expectancy, and the timing of the operation (Chrowninshield, 2006).

Fretting is a phenomenon which occurs between two contacting bodies experiencing reciprocating motion. In our case small scale reciprocating movements occur between the femoral stem and the femoral neck at the taper junction. When the main factor causing

Modular Femoral Neck Fracture After Total Hip Arthroplasty 173

cemented and uncemented way. They used S-Rom (S-Rom Modular Hip System, JMPC/DePuy, Warsaw, IN, USA), Apex Modular (Apex Modular Hip System, Global Orthopaedic Technology, Unanderra, NSW, Australia), K2 Apex (Apex K2 Modular Hip System, Omni Life Science, Inc., East Taunton, MA, USA), OTI/Encore R-120 cemented stem, OTI/Encore R-120 porous c.c. cementless stem (R-120 Modular Stem, DJO Surgical, Austin, TX, USA), UniSyn (UniSyn Total Hip System, Hayes Medical, Inc., El Dorado Hills, CA, USA) and Cremascoli Modular Neck (Wright Medical Technologies, Inc., Arlington, TN, USA). They experienced 12 femoral component failures, 2 in a c.c. proximal modular neck and 10 in proximal modular titanium shoulder neck. The authors remain enthusiastic about modularity and continue to use modular stems in their practice. The reason for failure in their cases was a single high load event and suggested quasi-static shear failure of the pin alignment. The OTI/Encore modular neck failure occurred in the distal neck engagement taper (Froehlich, 2006). The company increased the upper taper diameter, the lower taper diameter, the surface area, and the distal taper length so that the fatigue

Several recent case reports exist describing the failure of modular necks of the Profemur prostheses (Profemur Z, Wright Medical Technologies Inc., Arlington, TN, USA) (Atwood, 2010; Wright G., 2010; Wilson D. J., 2010). They describe a well integrated implant that could only be removed with trochanteric osteotomy. Usually the initiation site for failure was the anterior and superior part of the neck. Degradation of the polished surface was noted at the insertion point of the taper. Also, evidence of abrasion and corrosion was seen (Dangles, 2010). The Federal Drug Administration Manufacturer and User Facility Device Experience (FDA MAUDE) database describes 98 adverse effects for the Profemur modular neck prosthesis for the years 2000-2009. 37 of those include breakage of the femoral neck (FDA MAUDE, as cited in Skendzel et al., 2011). Skendzel et al. reported on two cases of fractured Profemur modular neck and concluded that the long varus necks used increased the bending moment by 32.7% when compared to short varus necks (Skendzel et al., 2011). The stress was concentrated at the modular junction. Removal of the complete femoral component was required during revision surgery because the Morse taper could not be removed. Both patients experienced a traumatic event before the failure. Atwood et al. described the fracture of a Profemur long straight neck in a man of 2 m height and 109.8 kg weight who fell on his hip (Atwood, 2010). The surgery revealed a crack of 2 mm below the stem edge. They found the initiation site near the lateral-anterior corner of the neck. They

Grupp et al. studied the Metha Short Hip Stem Prosthesis (Metha Short Hip Stem Prosthesis, Aesculap AG, Tuttlingen, Germany) as a consequence of several reports of failed titanium alloy femoral necks (Grupp, 2010). Out of 5,000 THA they found 68 neck adapter failures. They found neither processing or material deviation nor incorrect dimensioning. The retrieved prostheses showed a similar fracture pattern with the fracture starting in the anterolateral area at the upper part of the cone where there is maximum biomechanical stress. The reason for failure was attributed to fretting, fretting corrosion, and crevice corrosion which lead to the loss of fatigue strength of titanium alloy. The combination of factors listed above, as well as contamination of the cone adapter with fluids or particles, increased patient weight, high activity level, male gender, and CCD angle of 135 and smaller increased the rate of failure. They concluded that the change to cobalt-based alloy modular

testing results improved.

also found signs of crevice corrosion and fretting wear.

necks increases the safety of cone connection.

fretting is oxidation the process is called fretting corrosion. The more the neck is in varus position and the longer the neck is, the greater is the tendency for fretting because of the increased lever arm. Microscopic cracks develop in the fretting zone that can lead to femoral neck fracture. Studies in vitro show that mechanical loading accelerates the corrosion process (Goldberg and Gilbert, 2002).

Another type of process occurring at the taper connection is crevice corrosion. The crevice between two modules will be a corrosion site if there is enough space to allow the income of an aqueous solution (Colliere et al., 1992). The crevice should be sufficiently narrow to maintain a stagnant zone. As corrosion in this zone progresses, oxygen depletion will lead to an excess of positively charged ions in the surrounding aqueous environment of the crevice. The negatively charged chloride ions will migrate to balance them. As a result, hydrochloric acid will form. Hydrochloric acid can dissolve titanium or cobalt alloys which are otherwise stable. Once the crevice corrosion has begun it continues even in the absence of loading.

Concern was raised in the past that galvanic corrosion can arise from inappropriate combinations of dissimilar metal components. Galvanic corrosion is an electrochemical process in which two physically connected dissimilar metals experience metallic deterioration while being exposed to electrically conductive fluids. Different metals have different electrochemical characteristics. When two dissimilar metals are placed together, electrons will start to flow spontaneously from one metal to the other. The loss of electrons from the active metal is called oxidation and oxidation will lead to the process of corrosion (Shetty, 1989). Corrosion will start the release of metal ions and will cause among other complications damage to the prosthesis surface. This can lead to the loss of material strength and eventually to failure.

There is also a form of extremely localized, symmetric corrosion called pitting corrosion. It leads to the creation of small holes in the metal. The mechanism of pitting corrosion is probably the same as crevice corrosion.

The studies of modular neck adapters and stems showed that fretting leads to microcracks on the surface (Grupp, 2010; Wright Medical Technologies Inc., 2010). Fretting is accompanied with crevice corrosion and pitting corrosion. As mentioned above, the passive oxide film formed in titanium alloys is permanently destroyed by fretting corrosion and crevice corrosion. Fretting reduces the fatigue strength of titanium alloys. Fretting at the connection can be increased by the intraoperative contamination of taper with small particles of bone or tissue. Contamination should always be prevented by assembling the device carefully and drying the components before the assembly (Grupp, 2010). Both studies concluded that the change of femoral neck material from titanium alloys to cobalt alloys increases the safety of the connection (Grupp, 2010; Wright Medical Technologies Inc., 2010). Cobalt alloys have the same fatigue strength, they form the passive oxide layer and have excellent fretting corrosion characteristics in comparison to titanium alloys. Cobalt alloys are superior in stiffness and modules of elasticity, notch sensitivity, crack propagation, and abrasion compared to titanium alloys. However, cobalt alloys are inferior to titanium alloys in characteristics of crevice corrosion and are more allergenic. The authors recommended that heavier patients, especially those weighing more than 100 kg, and more physically active male patients require long necks made of cobalt alloys.

Froehlich et al. did a follow up of their experience with seven different modular stems implanted since 1984 (Froehlich, 2006). They implanted 2,248 stems for primary THA in

fretting is oxidation the process is called fretting corrosion. The more the neck is in varus position and the longer the neck is, the greater is the tendency for fretting because of the increased lever arm. Microscopic cracks develop in the fretting zone that can lead to femoral neck fracture. Studies in vitro show that mechanical loading accelerates the corrosion

Another type of process occurring at the taper connection is crevice corrosion. The crevice between two modules will be a corrosion site if there is enough space to allow the income of an aqueous solution (Colliere et al., 1992). The crevice should be sufficiently narrow to maintain a stagnant zone. As corrosion in this zone progresses, oxygen depletion will lead to an excess of positively charged ions in the surrounding aqueous environment of the crevice. The negatively charged chloride ions will migrate to balance them. As a result, hydrochloric acid will form. Hydrochloric acid can dissolve titanium or cobalt alloys which are otherwise stable. Once the crevice corrosion has begun it continues even in the absence

Concern was raised in the past that galvanic corrosion can arise from inappropriate combinations of dissimilar metal components. Galvanic corrosion is an electrochemical process in which two physically connected dissimilar metals experience metallic deterioration while being exposed to electrically conductive fluids. Different metals have different electrochemical characteristics. When two dissimilar metals are placed together, electrons will start to flow spontaneously from one metal to the other. The loss of electrons from the active metal is called oxidation and oxidation will lead to the process of corrosion (Shetty, 1989). Corrosion will start the release of metal ions and will cause among other complications damage to the prosthesis surface. This can lead to the loss of material strength

There is also a form of extremely localized, symmetric corrosion called pitting corrosion. It leads to the creation of small holes in the metal. The mechanism of pitting corrosion is

The studies of modular neck adapters and stems showed that fretting leads to microcracks on the surface (Grupp, 2010; Wright Medical Technologies Inc., 2010). Fretting is accompanied with crevice corrosion and pitting corrosion. As mentioned above, the passive oxide film formed in titanium alloys is permanently destroyed by fretting corrosion and crevice corrosion. Fretting reduces the fatigue strength of titanium alloys. Fretting at the connection can be increased by the intraoperative contamination of taper with small particles of bone or tissue. Contamination should always be prevented by assembling the device carefully and drying the components before the assembly (Grupp, 2010). Both studies concluded that the change of femoral neck material from titanium alloys to cobalt alloys increases the safety of the connection (Grupp, 2010; Wright Medical Technologies Inc., 2010). Cobalt alloys have the same fatigue strength, they form the passive oxide layer and have excellent fretting corrosion characteristics in comparison to titanium alloys. Cobalt alloys are superior in stiffness and modules of elasticity, notch sensitivity, crack propagation, and abrasion compared to titanium alloys. However, cobalt alloys are inferior to titanium alloys in characteristics of crevice corrosion and are more allergenic. The authors recommended that heavier patients, especially those weighing more than 100 kg, and more physically

Froehlich et al. did a follow up of their experience with seven different modular stems implanted since 1984 (Froehlich, 2006). They implanted 2,248 stems for primary THA in

process (Goldberg and Gilbert, 2002).

of loading.

and eventually to failure.

probably the same as crevice corrosion.

active male patients require long necks made of cobalt alloys.

cemented and uncemented way. They used S-Rom (S-Rom Modular Hip System, JMPC/DePuy, Warsaw, IN, USA), Apex Modular (Apex Modular Hip System, Global Orthopaedic Technology, Unanderra, NSW, Australia), K2 Apex (Apex K2 Modular Hip System, Omni Life Science, Inc., East Taunton, MA, USA), OTI/Encore R-120 cemented stem, OTI/Encore R-120 porous c.c. cementless stem (R-120 Modular Stem, DJO Surgical, Austin, TX, USA), UniSyn (UniSyn Total Hip System, Hayes Medical, Inc., El Dorado Hills, CA, USA) and Cremascoli Modular Neck (Wright Medical Technologies, Inc., Arlington, TN, USA). They experienced 12 femoral component failures, 2 in a c.c. proximal modular neck and 10 in proximal modular titanium shoulder neck. The authors remain enthusiastic about modularity and continue to use modular stems in their practice. The reason for failure in their cases was a single high load event and suggested quasi-static shear failure of the pin alignment. The OTI/Encore modular neck failure occurred in the distal neck engagement taper (Froehlich, 2006). The company increased the upper taper diameter, the lower taper diameter, the surface area, and the distal taper length so that the fatigue testing results improved.

Several recent case reports exist describing the failure of modular necks of the Profemur prostheses (Profemur Z, Wright Medical Technologies Inc., Arlington, TN, USA) (Atwood, 2010; Wright G., 2010; Wilson D. J., 2010). They describe a well integrated implant that could only be removed with trochanteric osteotomy. Usually the initiation site for failure was the anterior and superior part of the neck. Degradation of the polished surface was noted at the insertion point of the taper. Also, evidence of abrasion and corrosion was seen (Dangles, 2010). The Federal Drug Administration Manufacturer and User Facility Device Experience (FDA MAUDE) database describes 98 adverse effects for the Profemur modular neck prosthesis for the years 2000-2009. 37 of those include breakage of the femoral neck (FDA MAUDE, as cited in Skendzel et al., 2011). Skendzel et al. reported on two cases of fractured Profemur modular neck and concluded that the long varus necks used increased the bending moment by 32.7% when compared to short varus necks (Skendzel et al., 2011). The stress was concentrated at the modular junction. Removal of the complete femoral component was required during revision surgery because the Morse taper could not be removed. Both patients experienced a traumatic event before the failure. Atwood et al. described the fracture of a Profemur long straight neck in a man of 2 m height and 109.8 kg weight who fell on his hip (Atwood, 2010). The surgery revealed a crack of 2 mm below the stem edge. They found the initiation site near the lateral-anterior corner of the neck. They also found signs of crevice corrosion and fretting wear.

Grupp et al. studied the Metha Short Hip Stem Prosthesis (Metha Short Hip Stem Prosthesis, Aesculap AG, Tuttlingen, Germany) as a consequence of several reports of failed titanium alloy femoral necks (Grupp, 2010). Out of 5,000 THA they found 68 neck adapter failures. They found neither processing or material deviation nor incorrect dimensioning. The retrieved prostheses showed a similar fracture pattern with the fracture starting in the anterolateral area at the upper part of the cone where there is maximum biomechanical stress. The reason for failure was attributed to fretting, fretting corrosion, and crevice corrosion which lead to the loss of fatigue strength of titanium alloy. The combination of factors listed above, as well as contamination of the cone adapter with fluids or particles, increased patient weight, high activity level, male gender, and CCD angle of 135 and smaller increased the rate of failure. They concluded that the change to cobalt-based alloy modular necks increases the safety of cone connection.

Modular Femoral Neck Fracture After Total Hip Arthroplasty 175

Fig. 1. Standard antero-posterior radiograph of the patient's right hip at admission.

In order to properly reconstruct the biomechanics of the hip, cementless revision modular stem with ceramic head (Waldemar Link GmbH & Co, Hamburg, Germany) was used. The acetabular lining was exchanged as well and a custom made ANCA-Fit (Wright Medical Technology, Inc., Arlington, TN, USA) component implanted (Fig. 5). Standard tissue specimens were collected during the revision procedure for microbiologic cultures which

(Courtesy M. Kotnik, M. D.)

showed no bacterial growth.

However, some studies did not show any problems regarding modular femoral components. The study by Toni et al. showed no clinical complications related to modular necks (Toni et al., 2001). They studied 216 hip prostheses of AnCA Fit type (AnCA Fit, Cremascoli Ortho, Milan, Italy) which were implanted from June 1995 to December 1997. Another study by Duwelius et al. using the Zimmer M/L Taper Hip Prosthesis with Kinectiv Technology (Zimmer M/L Taper Hip Prosthesis with Kinectiv Technology, Zimmer, Warsaw, IN, USA) on 634 patients from April 2007 to November 2008 showed no complications related to modular neck failure (Duwelius et al., 2010). The stem and neck were manufactured from titanium alloy (Ti6Al4V).

## **6. Case report**

At the Depatment of Orthopaedic Surgery and Sports Trauma, Celje General and Teaching Hospital, Celje, Slovenia, modular hip prostheses have been used since the year 1992 in selected patients. The first prosthesis used was GSP (Cremascoli Ortho, Sorem Ortho, Toulon, France) and at the time of writing the prosthesis in use is the Profemur Z (Wright Medical Technology, Inc., Arlington, TN, USA). From 1992 to 2008, 306 modular neck hip prostheses of three different types were implanted at our department. From 1992 to 2004, 88 GSP modular neck hip prostheses (Cremascoli Orthopaedics, Sorem Ortho, Toulon, France) were implanted. From 2002 to 2006 we implanted 58 Anca Dual Fit hip stems (Cremascoli Ortho, Milan, Italy). In 2006 we started implanting Profemur Z modular neck hip prostheses (Wright Medical Technology, Inc., Arlington, TN, USA) and 160 of these were implanted by the end of 2008.

In December 2010, a 69-year old male was admitted to our hospital's emergency department with acute pain in his right hip. The pain appeared after a fall on his right side from standing height. The examination revealed right inguinal tenderness and shortening of his right lower extremity with external rotation. The review of standard radiographic exams showed modular prosthesis neck fracture. This was the first such complication seen at our department (Fig. 1). The patient's height was 178 cm and he weighed 110 kg (BMI 34.7). He was treated at our institution in 1998 when he was 56 years old. At that time his BMI was 31.6 (weight 100 kg). The operation was performed because the patient suffered from rheumatoid arthritis with the involvement of his right hip. A fully modular cementless total hip endoprosthesis was implanted (fully hidroxy-apatite coated femoral stem (GSP) with modular cobalt-chromium long straight neck, 28 mm diameter ceramic head, and acetabulum of the press-fit type (ANCA-Fit) with ceramic acetabular insert, (Cremascoli Orthopaedics, Sorem Ortho, Toulon, France). None of the postoperative visits or radiographic exams showed any signs of wear or other complications. The patient was pain free before the event.

Revision surgery was scheduled as soon as we received the custom made acetabular cup inlay (ANCA-Fit, Wright Medical Technology Inc., Arlington, TN, USA). The operation was performed by the same surgeon and the previous lateral approach was used. Revision surgery confirmed the fracture of the modular prosthesis neck. It was impossible to remove only the remaining neck from the taper, so that the entire femoral stem had to be removed. The femoral stem was well integrated in the femur and femoral osteotomy was necessary in order to remove the implant. Macroscopically, the tissue showed no metal debris or granuloma. The remaining part of the fractured neck module was approximately 2 mm below the top of the taper (Fig. 2-4).

However, some studies did not show any problems regarding modular femoral components. The study by Toni et al. showed no clinical complications related to modular necks (Toni et al., 2001). They studied 216 hip prostheses of AnCA Fit type (AnCA Fit, Cremascoli Ortho, Milan, Italy) which were implanted from June 1995 to December 1997. Another study by Duwelius et al. using the Zimmer M/L Taper Hip Prosthesis with Kinectiv Technology (Zimmer M/L Taper Hip Prosthesis with Kinectiv Technology, Zimmer, Warsaw, IN, USA) on 634 patients from April 2007 to November 2008 showed no complications related to modular neck failure (Duwelius et al., 2010). The stem and neck

At the Depatment of Orthopaedic Surgery and Sports Trauma, Celje General and Teaching Hospital, Celje, Slovenia, modular hip prostheses have been used since the year 1992 in selected patients. The first prosthesis used was GSP (Cremascoli Ortho, Sorem Ortho, Toulon, France) and at the time of writing the prosthesis in use is the Profemur Z (Wright Medical Technology, Inc., Arlington, TN, USA). From 1992 to 2008, 306 modular neck hip prostheses of three different types were implanted at our department. From 1992 to 2004, 88 GSP modular neck hip prostheses (Cremascoli Orthopaedics, Sorem Ortho, Toulon, France) were implanted. From 2002 to 2006 we implanted 58 Anca Dual Fit hip stems (Cremascoli Ortho, Milan, Italy). In 2006 we started implanting Profemur Z modular neck hip prostheses (Wright Medical Technology, Inc., Arlington, TN, USA) and 160 of these were implanted by

In December 2010, a 69-year old male was admitted to our hospital's emergency department with acute pain in his right hip. The pain appeared after a fall on his right side from standing height. The examination revealed right inguinal tenderness and shortening of his right lower extremity with external rotation. The review of standard radiographic exams showed modular prosthesis neck fracture. This was the first such complication seen at our department (Fig. 1). The patient's height was 178 cm and he weighed 110 kg (BMI 34.7). He was treated at our institution in 1998 when he was 56 years old. At that time his BMI was 31.6 (weight 100 kg). The operation was performed because the patient suffered from rheumatoid arthritis with the involvement of his right hip. A fully modular cementless total hip endoprosthesis was implanted (fully hidroxy-apatite coated femoral stem (GSP) with modular cobalt-chromium long straight neck, 28 mm diameter ceramic head, and acetabulum of the press-fit type (ANCA-Fit) with ceramic acetabular insert, (Cremascoli Orthopaedics, Sorem Ortho, Toulon, France). None of the postoperative visits or radiographic exams showed any signs of wear or other complications. The patient was pain

Revision surgery was scheduled as soon as we received the custom made acetabular cup inlay (ANCA-Fit, Wright Medical Technology Inc., Arlington, TN, USA). The operation was performed by the same surgeon and the previous lateral approach was used. Revision surgery confirmed the fracture of the modular prosthesis neck. It was impossible to remove only the remaining neck from the taper, so that the entire femoral stem had to be removed. The femoral stem was well integrated in the femur and femoral osteotomy was necessary in order to remove the implant. Macroscopically, the tissue showed no metal debris or granuloma. The remaining part of the fractured neck module was approximately 2 mm

were manufactured from titanium alloy (Ti6Al4V).

**6. Case report**

the end of 2008.

free before the event.

below the top of the taper (Fig. 2-4).

Fig. 1. Standard antero-posterior radiograph of the patient's right hip at admission. (Courtesy M. Kotnik, M. D.)

In order to properly reconstruct the biomechanics of the hip, cementless revision modular stem with ceramic head (Waldemar Link GmbH & Co, Hamburg, Germany) was used. The acetabular lining was exchanged as well and a custom made ANCA-Fit (Wright Medical Technology, Inc., Arlington, TN, USA) component implanted (Fig. 5). Standard tissue specimens were collected during the revision procedure for microbiologic cultures which showed no bacterial growth.

Modular Femoral Neck Fracture After Total Hip Arthroplasty 177

Fig. 3. A close-up photograph showing the fractured modular femoral neck.

Fig. 4. Photograph showing the removed prosthesis with fractured neck and the remaining

of the modular neck in the femoral stem taper.

Fig. 2. Photograph of the retrieved fully-modular prosthesis showing the modular neck fracture.

Fig. 2. Photograph of the retrieved fully-modular prosthesis showing the modular neck

fracture.

Fig. 3. A close-up photograph showing the fractured modular femoral neck.

Fig. 4. Photograph showing the removed prosthesis with fractured neck and the remaining of the modular neck in the femoral stem taper.

Modular Femoral Neck Fracture After Total Hip Arthroplasty 179

to the significant differences among the individuals requiring hip reconstruction. Some types of modular neck prostheses offer as much as 60 different variations with modularity

However, added modularity brings another possibility for complication. Recent reports emphasize the need for changing the neck material from titanium alloys to the safer cobaltchromium alloys. Constant evaluation of laboratory material should be continued, even though it does not always guarantee proper information regarding in vivo parameters. Careful preoperative planning should be performed in spite of modular neck THA allowing anatomic reconstruction of the hip. The increased variety of intraoperative surgical options with the fully-modular stems should not be an excuse for bad surgical technique and

Abraham R. & Arthur L. M. (2005). Instability after Total Hip Replacement. *Seminars in*

American Academy of Orthopaedic Surgeons, AAOS. (April 2009). Total Hip Replacement, In: *Your orthopaedic connection*, Accessed June 23 2011, Available from:

Atwood, S.; Patten, E.; Bozic, K.; Pruitt, L. & Ries, M. (2010). Corrosion-induced fracture of a

Collier, J.; Surprenant, V.; Jensen, R.; Mayor, M. & Surprenant, H. (1992). Corrosion between

Dangles, C. J. & Altstetter, C. J. (2010). Failure of the modular neck in a total hip

Duwelius, P. J.; Hartzband, M. A.; Burkhart, R.; Carnahan, C.; Blair, S.; Wu, Y. &

Foerg, F. (2005). Medical Complications Associated with Total Hip Arthroplasty. *Seminars in*

Froehlich, J. A.; McTighe, T.; Cameron, H. U.; Kegg, K.; Keggi, J.; Kennon, R. & Woodgate, I.

Garellick, G.; Kärrholm, J.; Rogmark, C. & Herberts, P. (October 2009). Swedish Hip

Goldberg, J. & Gilbert, J. (2002). In vitro corrosion testing of modular hip tapers. *Journal of*

*Medicine, Göteborg University,* Accessed June 24 2011, Available from:

*Arthroplasty*, Vol.16, No.2, (June 2005), pp. 88-99, ISSN 1045-4527

double-modular hip prosthesis: a case report. *The Journal of Bone and Joint Surgery,*

the components of modular femoral hip prostheses. *The Journal of Bone and Joint Surgery, British Volume*, Vol.74, No.4, (July 1992), pp. 511-517, ISSN 0301-620X Crowninshield, R.; Rosenberg, A. & Sporer, S. (2006). Changing demographics of patients

with total joint replacement. *Clinical Orthopaedics and Related Research*, Vol.443, No.2,

arthroplasty. *The Journal of Arthroplasty,* Vol.25, No.7, ( October 2010), pp. 5-7, ISSN

Grunkemeier, G. L. (2010). Clinical Results of a Modular Neck Hip System: Hitting the "Bull's-Eye" More Accurately. *American Journal of Orthopedics,* Vol.39, Suppl.10,

(2006). Defining the Role of Modular Stem Designs in THA, *ITSA 19th Annual*

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<http://orthoinfo.aaos.org/topic.cfm?topic=a00377>

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(October 2010), pp. 2-6, ISSN 1078-4519

*Symposium,* New York City, October 2006

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compared to only about 10 options offered by monoblock stems (Duwelius, 2010).

improper cup position.

0883-5403

**8. References**

Fig. 5. Radiograph of the revised right hip with the cementless revision modular prosthesis in place. (Courtesy M. Kotnik, M. D.)

## **7. Conclusion**

Modular neck hip prostheses are nowadays wildly used around the globe. The Profemur stem (Wright Medical Technology Inc., Arlington, TN, USA) only was sold in more than 200,000 units by the end of 2010 (Wright Medical Technologies Inc., 2010). There are many benefits in proximal modularity. The theoretical benefits of modular neck include bone and tissue conservation, restoration of joint biomechanics, reduced blood loss, easier rehabilitation, ease of revision, simple surgical technique, and different modular options (McTighe, 2008). In addition, the possibility of implanting a stem with a retroverted modular neck can prevent cup impingement and dislocation of the prosthesis. Moreover, if revision operation is necessary for the dislocated THA, only exchange of the modular neck might be required. The surgeon has an intraoperative option of choosing the appropriate neck length, neck version and CCD angle independently of the femoral stem size, taking into account the considerable differences in stem sizes between the two sexes (Traina, 2009). The proximal modular neck type of the prosthesis is useful in primary hip arthroplasty due to the significant differences among the individuals requiring hip reconstruction. Some types of modular neck prostheses offer as much as 60 different variations with modularity compared to only about 10 options offered by monoblock stems (Duwelius, 2010).

However, added modularity brings another possibility for complication. Recent reports emphasize the need for changing the neck material from titanium alloys to the safer cobaltchromium alloys. Constant evaluation of laboratory material should be continued, even though it does not always guarantee proper information regarding in vivo parameters. Careful preoperative planning should be performed in spite of modular neck THA allowing anatomic reconstruction of the hip. The increased variety of intraoperative surgical options with the fully-modular stems should not be an excuse for bad surgical technique and improper cup position.

#### **8. References**

178 Recent Advances in Hip and Knee Arthroplasty

Fig. 5. Radiograph of the revised right hip with the cementless revision modular prosthesis

Modular neck hip prostheses are nowadays wildly used around the globe. The Profemur stem (Wright Medical Technology Inc., Arlington, TN, USA) only was sold in more than 200,000 units by the end of 2010 (Wright Medical Technologies Inc., 2010). There are many benefits in proximal modularity. The theoretical benefits of modular neck include bone and tissue conservation, restoration of joint biomechanics, reduced blood loss, easier rehabilitation, ease of revision, simple surgical technique, and different modular options (McTighe, 2008). In addition, the possibility of implanting a stem with a retroverted modular neck can prevent cup impingement and dislocation of the prosthesis. Moreover, if revision operation is necessary for the dislocated THA, only exchange of the modular neck might be required. The surgeon has an intraoperative option of choosing the appropriate neck length, neck version and CCD angle independently of the femoral stem size, taking into account the considerable differences in stem sizes between the two sexes (Traina, 2009). The proximal modular neck type of the prosthesis is useful in primary hip arthroplasty due

in place. (Courtesy M. Kotnik, M. D.)

**7. Conclusion**

**12**

**Surface Replacement of Hip Joint**

*2Professor of Trauma and Orthopaedics, Warwick Orthopaedics*

*1Orthopaedic Research Fellow/PhD Student, Warwick Orthopaedics*

Surface hip replacement more commonly known as hip resurfacing arthroplasty is a type of a hip replacement that is different to a total hip replacement. In a total hip replacement femoral head and neck are removed and a metal stem is inserted to the femoral shaft. In hip resurfacing articular surface is shaved and a metal cap (Fig 1) is inserted preserving most of

Fig. 1. X Ray shows a Hip Resurfacing arthroplasty (Right) and a Total Hip Replacement (Left)

**1. Introduction**

the bone in femoral head and neck.

Hiran Amarasekera and Damian Griffin

*University of Warwick Medical School*

*University of Warwick Medical School*

*United Kingdom*

## **Surface Replacement of Hip Joint**

## Hiran Amarasekera and Damian Griffin

*1Orthopaedic Research Fellow/PhD Student, Warwick Orthopaedics University of Warwick Medical School 2Professor of Trauma and Orthopaedics, Warwick Orthopaedics University of Warwick Medical School United Kingdom*

## **1. Introduction**

180 Recent Advances in Hip and Knee Arthroplasty

Grupp, T.; Weik, T.; Bloemer, W. & Knaebel, H. (2010). Modular titanium alloy neck adapter

Hertzler, J. S.; Johnson, T. S. & Meulink, S. L. (2009). *Performance evaluation of Kinectiv™*

Keppler, L.; Cameron, H. U. & McTighe, T. (2006). The Role of Modularity in Primary THA -

Massin, P.; Geais, L.; Astoin, E.; Simondi, M. & Lavaste, F. (2000). The anatomic basis for the

McTighe, T.; Woodgate, I.; Turnbull, A.; Keggi, J.; Kennon, R.; Keppler, L.; Harrison, J.;

Paliwal, M.; Gordon Allan, D. & Filip, P. (2010). Failure analysis of three uncemented

Sharan, D. (1999). The problem of corrosion in orthopaedic implant materials. *Orthopaedic*

Shetty, R. (1989). *Use of Dissimilar Metals in Orthopaedic Implants,* Zimmer, Inc., Retrieved

Skendzel, J. G.; Blaha, J. D. & Urquhart, A. G. (2011). Total hip arthroplasty modular neck failure. *The Journal of Arthroplasty*, Vol.26, No.2, (February 2011), pp. 338.e1-338.e4 Toni, A.; Paderni, S.; Sudanese, A.; Guerra, E.; Traina, F.; Antonietti, B. & Giunti, A. (2001).

necks: 3 to 5 years follow-up. *Hip International,* Vol.11, No.1, (2001), pp. 1-17 Traina, F.; De Clerico, M.; Biondi, F.; Pilla, F.; Tassinari, E. & Toni, A. (2009). Sex differences

Wilson, N.; Schneller, E.; Montgomery, K. & Bozic, K. (2008). Hip and knee implants: current trends and policy considerations. *Health Affairs,* Vol.27, No.6, (2008), pp. 1587-1598 Wright, G.; Sporer, S.; Urban, R. & Jacobs, J. (2010). Fracture of a Modular Femoral Neck

Wright Medical Technology, Inc. (2010). Masters Hip Post Training Document, Amsterdam,

pdf/Performance\_Evaluation\_of\_Kinectiv\_Technology.pdf>

THA Stem. *AAOS Scientific Exhibit,* San Francisco, March 2008

Is There One?, *AAOS Scientific Exhibit*, Chicago, 2006

(July 2010), pp. 1230-1238, ISSN 1350-6307

Orthopaedic\_Implants.pdf>

*Update (India),* Vol.9, No.1, (December 1999), pp. 1-5

*Surgery*, Vol.92, No.6, (June 2010), pp. 1514-1517

Vol.92, No.6, (June 2010), pp. 1518–1521

July 2010

u1.0-B978-0-323-03329-9..50010-6>

ISSN 0883-5403

failures in hip replacement - failure mode analysis and influence of implant material. *BMC Musculoskeletal Disorders*, Vol.11, No.3, (January 2010), pp. 1-12 Harkess, J. W. & Crockarell, J. R. (2007). Arthroplasty of the hip, In: *Campbell's Operative*

*Orthopaedics,* Canale, S. T. & Beaty, J. H., (Eds.), pp. 314-351, Mosby, An Imprint of Elsevier, Retrieved from <http://www.mdconsult.com/books/page.do?eid=4 u1.0-B978-0-323-03329-9..50010-6&isbn=978-0-323-03329-9&uniqId=263852506-2#4-

*Technology*, Zimmer, Inc, Retrieved from <http://www.zimmer.com/web/enUS/

concept of lateralized femoral stems: a frontal plane radiographic study of the proximal femur. *The Journal of Arthroplasty,* Vol.15, No.1, (January 2000), pp. 93-101,

Brazil, D.; Wu, W. & Cameron, H. U. (2008). A New Approach To Neck Sparing

titanium-alloy modular total hip stems. *Engineering Failure Analysis*, Vol.17, No.5,

from http://www.zimmer.co.nz/web/enUS/pdf/Use\_Of\_Dissimilar\_Metals\_in\_

Anatomic cementless total hip arthroplasty with ceramic bearings and modular

in hip morphology: is stem modularity effective for total hip replacement? *The Journal of Bone and Joint Surgery,* Vol.91, Suppl.6, (November 2009), pp. 121-128 Wilson, D. J.; Dunbar, M.; Amirault, J. & Farhat, Z. (2010). Early failure of a modular femoral

neck total hip arthroplasty component: a case report. *The Journal of Bone and Joint*

After Total Hip Arthroplasty. A Case Report. *The Journal of Bone and Joint Surgery,*

Surface hip replacement more commonly known as hip resurfacing arthroplasty is a type of a hip replacement that is different to a total hip replacement. In a total hip replacement femoral head and neck are removed and a metal stem is inserted to the femoral shaft. In hip resurfacing articular surface is shaved and a metal cap (Fig 1) is inserted preserving most of the bone in femoral head and neck.

Fig. 1. X Ray shows a Hip Resurfacing arthroplasty (Right) and a Total Hip Replacement (Left)

Surface Replacement of Hip Joint 183

With a high range of motion and a low dislocation rate surface replacement seem to be the ideal option for a young adult who could have a near normal range of motion following resurfacing arthroplasty. If the patient requires a revision to total hip replacement then this could be delayed and a second revision delayed even further. As people live longer with an increasing life expectancy rate this enables the orthopaedic surgeon to delay the first total hip replacement. (Della Valle, Nunley, and Barrack 2008; Hing, Back, and

However with the availability of the long-term complications of hip resurfacing arthroplasty the initial interest that prevailed in early 1990s has waned over the last few years and, many

Resurfacing is better tolerated by men than women. Pre-menopausal women have a better chance than the post menopausal women as the femoral neck fracture rate increases after menopause.(Shimmin and Back 2005) Some studies suggest that surgical technique, implant selection, and implant positioning should be modified according to the gender. If this is done there is a high possibility that gender specific bias can be eliminated, as this is a common problem in surface replacement.(Amstutz, Wisk, and Le Duff 2011; Jameson et al.

Ideal candidate for a hip resurfacing is a patient with primary osteoarthritis. However most patients do not develop primary osteoarthritis at an early age. Younger patients developing osteoarthritis is mostly due to secondary causes. Surface replacement of the hip has been performed in many pathological conditions that eventually lead to secondary osteoarthritis. However conditions in which the bone may be weak such as osteoporosis, resurfacings should be avoided as this can lead to high incidence of femoral neck fractures. Avascular necrosis (AVN) is a relative contraindication for hip resurfacing. Even though some surgeons have performed hip resurfacing in AVN patients most surgeons believe that resurfacing should not be done on these patients. Partial hip resurfacing/hemi resurfacing seems to be the popular treatment option for patients with Avascular Necrosis. In partial resurfacing only the necrotic area of the articular surface is removed and replaced (Fig 2).(Siguier et al. 2001; Ushio et al. 2003) Partial resurfacing is also done for localised

The indications for hip resurfacing has changed during the past decade as high failure rates

Surgical approach to the hip is similar to the approaches done when performing a total hip replacement. However there are many additional considerations to be kept in mind when

This has lead to a re think and development of more stringent patient selection criteria.

Shimmin 2007)

**3.1.1 Age**

**3.1.2 Sex**

2008)

**3.1 Selection criteria**

**3.1.3 Pathology of the hip**

**3.2 Surgical techniques**

osteochondral defects. (Van Stralen et al. 2009)

were observed among certain patient groups.(McMinn et al. 2011)

surgeons have narrowed selection criteria down.

55 years for women 65 years for men.(Corten et al. 2011)

Compared to the total hip replacement resurfacing arthroplasty preserves more bone on the femoral side (Fig.1). Acetabular replacement is similar to both procedures. Main advantages of surface replacement include preservation of femoral bone stock; increase degree of motion, and easier conversion to a total hip replacement during revision. All these make resurfacing arthroplasty an attractive alternative to a total hip replacement especially in the young active adults.

## **2. History**

Professor Sir John in initially introduced hip resurfacing early in 1950s. (Charnley 1960; McMinn and Daniel 2006) The initial designs were uncemented PTFE (polytetrafluaroethelene) on metal. All early implants had an acetabular component made of softer material such as PFFE and femoral component made of metal. This combination of hard on soft surface caused many problems.

The previous designs failed due to two main reasons. Firstly combination of hard on soft surfaces and large diameter heads lead to increase wear, wear particle accumulation, osteolysis of the bone.

Secondly posterior approach used during the procedure damaged the blood supply to the femoral head. This lead to reduced femoral head vascularity, osteonecrosis, femoral neck fractures, and aseptic loosening of the implant.

Due to these problems hip resurfacings in the 50s through 80s were not a popular option to treat arthritis in the young adult. However in early 1990s *McMinn et al (McMinn et al. 1996)* introduced the modern hip resurfacing which used metal on metal bearings with improved instrumentation for precision placement of implants. It was believed metal on metal reduce the wear and tear of the implanted hip. Vascularity too was addressed by proposing many surgical approaches such as the trochanteric flip(Ganz et al. 2001) anterolateral(Jacobs, Goytia, and Bhargava 2008) or direct-lateral (Hardinge 1982)as alternative approaches to the conventional posterior approach which is widely used in total hip replacement.

Hip resurfacings has been conducted in many centres since early 1990 as popular option in treating young active adults with hip problems. However with time long term results from the modern surface replacements has identified it's own set of complications(Shimmin, Bare, and Back 2005) such as femoral neck fractures aseptic loosening, avascular necrosis, osteolysis of head and increase metal ions levels.(Hing, Back, and Shimmin 2007)

Due to these factors the selection criteria for surface replacement has changed from a much broader set to a narrow and a limited set, over the last decade.(Nunley, Della Valle, and Barrack 2009)

At present even-though the selection criteria is narrowed it sill remains a key alternative to the conventional hip replacements.

## **3. Indications for hip resurfacing**

When surface replacement was re introduced in early 1990 s the ideal candidate for the procedure was a young active adult with good hip morphology and a reasonably good bone quality, with osteoarthritis of the hip.(McMinn et al. 2011)

With a high range of motion and a low dislocation rate surface replacement seem to be the ideal option for a young adult who could have a near normal range of motion following resurfacing arthroplasty. If the patient requires a revision to total hip replacement then this could be delayed and a second revision delayed even further. As people live longer with an increasing life expectancy rate this enables the orthopaedic surgeon to delay the first total hip replacement. (Della Valle, Nunley, and Barrack 2008; Hing, Back, and Shimmin 2007)

However with the availability of the long-term complications of hip resurfacing arthroplasty the initial interest that prevailed in early 1990s has waned over the last few years and, many surgeons have narrowed selection criteria down.

#### **3.1 Selection criteria**

#### **3.1.1 Age**

182 Recent Advances in Hip and Knee Arthroplasty

Compared to the total hip replacement resurfacing arthroplasty preserves more bone on the femoral side (Fig.1). Acetabular replacement is similar to both procedures. Main advantages of surface replacement include preservation of femoral bone stock; increase degree of motion, and easier conversion to a total hip replacement during revision. All these make resurfacing arthroplasty an attractive alternative to a total hip replacement especially in the

Professor Sir John in initially introduced hip resurfacing early in 1950s. (Charnley 1960; McMinn and Daniel 2006) The initial designs were uncemented PTFE (polytetrafluaroethelene) on metal. All early implants had an acetabular component made of softer material such as PFFE and femoral component made of metal. This combination of

The previous designs failed due to two main reasons. Firstly combination of hard on soft surfaces and large diameter heads lead to increase wear, wear particle accumulation,

Secondly posterior approach used during the procedure damaged the blood supply to the femoral head. This lead to reduced femoral head vascularity, osteonecrosis, femoral neck