**1. Introduction**

Hip arthroscopy has been available for some years. Although arthroscopy has not been as widely adopted in the hip joint as compared to its use in other joints, it is currently in a phase of rapid development.

This is mainly due to the description of femoroacetabular impingement syndrome, where hip arthroscopy has proven to be a precious diagnostic and therapeutic tool. The development and improvement of the technique together with the instrumentation has allowed broadening its indications.

The hip joint, is more difficult to access than other joints such as the knee and shoulder. This is due to its tight congruency, the degree of coverage of the ball and socket articular surfaces – the acetabulum extends beyond the equator of the femoral head - the powerful surrounding muscles and the proximity of important vessels and nerves.

These anatomical features restrict the manoeuvrability of the arthroscopic instruments making hip arthroscopy a more demanding technique.

With the techniques for the knee and shoulder joints already well established, we have witnessed the development of arthroscopy for the diagnosis and treatment of hip disorders over the last decade (Johnston et al., 2008; Kelly et al., 2003; Larson et al., 2009; Lubowitz & Poehling, 2006). Arthroscopic techniques have improved, increasing the surgical indications and achieving better outcomes (Byrd, 2006; Byrd & Jones, 2009; Larson & Giveans, 2009; Philippon, 2007a, 2007b). This procedure is performed in children and in adults for both diagnostic and therapeutic purposes, (Kocher et al., 2005; McCarthy & Lee, 2006; Parisien, 1988; Philippon et al., 2007b; Roy et al., 2009; Sampson, 2006), the most commonly treated disorder being femoroacetabular impingement syndrome (Philippon et al., 2007b).

The first publication concerning visualization of the hip joint was by Burman in 1931, who reported his experience in 20 hips using a 4-mm arthroscope and the use of water to achieve joint distension (Burman, 1931). He described the anterior peritrochanteric portal, concluding that this was the best option for visualizing the hip joint. He concluded that the hip joint was not suitable for arthroscopy due to the inability to access and visualize what nowadays is known as the central compartment. Although there were some other reports in the intervening years, it is considered that Gross, in 1977, was the first person to describe the

Arthroscopy after Total Hip Replacement Surgery 81

(Bajwa & Villar, 2011; Beck, 2009; Smith & Rorabeck, 1999), trochanteritis, subluxation and femoroacetabular impingement syndrome (Bajwa & Villar, 2011; Beck, 2009; Bozic & Rubash, 2004; Brown & Callaghan, 2008; Malik et al., 2007; Smith & Rorabeck, 1999), acute and sub-acute infection (Hyman et al., 1999; McCarthy et al., 2009), and pain of unknown

2. Pain due to the prosthesis itself Septic or aseptic loosening

Table 1**. Causes of pain following total Hip Replacement and indications for arthroscopic surgery**. In blue font: Indications for diagnostic hip arthroscopy; in red font: Indications for diagnostic and therapeutic hip; and in black: those conditions which cannot be addressed

A battery of complementary tests is available for its diagnosis. These include blood tests

The combination of scintigraphy tests with Ga67, Tc99, and In111- labelled leukocytes has high sensitivity and specificity for the diagnosis of implant loosening and for distinguishing between septic and aseptic inflammation (Merkel et al., 1985, 1986; Rushton et al., 1982). We routinely perform arthocentesis and take samples of synovial tissue from three or four areas around the prosthetic joint, as a first stage at the beginning of the surgical procedure. Samples were sent to the Pathology Unit. None of the patients receive antibiotic therapy for at least 5 days prior to the intervention and prophylaxis is not initiated until after the samples were taken. The assessment of signs of loosening is completed by applying force with a blunt-ended instrument to all the prosthetic components in turn and carrying out

Tendon inflammation around the implant is one of the typical causes of pain after THR. Amongst these, iliopsoas tendonitis secondary to hip replacement has a prevalence of up to 4.3% according to several authors (Ala Eddine et al., 2001; Bricteaux et al., 2000; Dora et al., 2007). Various factors can be responsible for iliopsoas inflammation, but particular attention should be drawn to changes in the course of the tendon due to the resection of the femoral head in hip replacement surgery. This modifies the course of the tendon bringing it closer to the medial edge of the prosthetic acetabulum and femoral neck, increasing the probability of

movements causing leverage under arthroscopy and fluoroscopic control (Fig-1).

4. Neuropathic pain Algodystrophy 5. Referred pain Lumbar, vascular…

6. Femoroacetabular impingement Cam, pincer 7. Acute infection in total hip prosthesis Acute arthritis 8. Pain of unknown origin Differential diagnosis

Neuralgia Calcification Trochanteritis

"Tip effect"

Piriformis syndrome Psoas syndrome Arthrofibrosis / plica

origin (Bozic & Rubash, 2004; Witvoët, 2001).

3. Tendon and muscle pain

using arthroscopic surgery

**2.1 Prosthesis loosening**

1. Pain associated with the site of surgical approach

(CRP and ESR), X-rays and particularly scintigraphy.

**2.2 Tendon pain (iliopsoas tendonitis)**

impingement (O'Sullivan et al., 2007).

clinical application of this approach and its therapeutic effect in hip diseases in children (Legg-Calvé-Perthes disease, congenital dislocation and epiphysiolysis). He used a 2.2-mm arthroscope and manual distraction. The use of traction was first described by Eriksson who employed forces of between 300 to 400 Newtons to distract the hip (Eriksson et al., 1986). The first description of the use of traction in the supine position was made by Byrd 8Byrd, 1994); while Glick was the first to report the use of the lateral decubitus position (Glick et al., 1987). Monllau published results of a study demonstrating that hip arthroscopy required instruments with a minimum length of 16 cm (Monllau et al., 2003).

It is well known that following total hip replacement THR, pain disappears in approximately 95-98% of the cases, usually between 3 to 6 months up to a year after surgery. However, between 1 and 2% of patients refer persistence of pain. Although prosthesis components loosening is responsible for these complications in more than 90% of the cases, there are other potential causes of pain such as heterotopic ossification, muscle and tendon pain around the prosthesis, impingement and radiating back pain. In 1% of the cases the cause of pain remains unknown (Witvoët, 2001).

There is a clear similarity between the aforementioned sources of ongoing pain after hip replacement and those reported in relation to persistence of pain after knee replacement. Since 1989, several authors have reported the use of arthroscopy as a diagnostic and therapeutic tool in painful complications of knee implants, Wasilewski being the earliest (Bocell et al., 1991; Johnson et al., 1990; Lawrence & Kan, 1992; Lucas et al., 1999; Markel et al., 1996; Scranton, 2001; Tzagarakis et al., 2001; Wasilewski & Frankl, 1989a, 1989b). The use of arthroscopy in selected patients with hip implants represents a step forward in diagnosis and possible treatment of painful, apparently well implanted prostheses (Cuéllar et al., 2009; McCarthy et al., 2009; Bajwa & Villar, 2011). In our hospital environment we have established an arthroscopic protocol for hip implant monitoring, similar to the approach we use in knee replacement patients and indicate arthroscopic surgery in cases in which, despite the prosthesis being apparently well implanted, patients continue to experience pain (Cuéllar et al., 2009).

#### **2. Differential diagnosis**

The differential diagnosis of pain following THR is wide and includes intrinsic and extrinsic causes to the implant. Septic or aseptic loosening is the cause of intrinsic complications in more than 90% of cases, but there are other potential causes such as stress fractures, mechanical failure or elasticity of the implant itself, subluxation or impingement (Bozic & Rubash, 2004; Smith & Rorabeck, 1999). Additionally there are other extrinsic causes of pain including lumbar radicular pain, neurogenic or vascular claudication (Beck, 2009), heterotopic ossification, trochanteritis or trochanteric non-union (Brown & Callaghan, 2008), peripheral nerve lesions (Malik et al., 2007), tendon and muscle pain around the implant (adductor and iliopsoas tendinitis, arthrofibrosis) (Hyman et al., 1999), femoral or inguinal hernia, and, more rarely, concomitant malignant conditions (Merkel et al., 1985). Finally, in around 1% of cases the source of the pain is never found.

The protocol that we routinely use for differential diagnosis includes a detailed medical history and a thorough clinical examination, laboratory tests (FBC, ESR, and CRP), Radiology investigations (X-rays, CT scan, and scintigraphy) and diagnostic nerve blocks.

Of all the possible causes of pain (Bozic & Rubash, 2004; Smith & Rorabeck, 1999; Witvoët, 2001), we highlight those which we can be addressed using arthroscopy (Table 1): loosening (diagnostic value), tendon pain (iliopsoas, piriformis and plica syndromes or arthrofibrosis)

clinical application of this approach and its therapeutic effect in hip diseases in children (Legg-Calvé-Perthes disease, congenital dislocation and epiphysiolysis). He used a 2.2-mm arthroscope and manual distraction. The use of traction was first described by Eriksson who employed forces of between 300 to 400 Newtons to distract the hip (Eriksson et al., 1986). The first description of the use of traction in the supine position was made by Byrd 8Byrd, 1994); while Glick was the first to report the use of the lateral decubitus position (Glick et al., 1987). Monllau published results of a study demonstrating that hip arthroscopy required

It is well known that following total hip replacement THR, pain disappears in approximately 95-98% of the cases, usually between 3 to 6 months up to a year after surgery. However, between 1 and 2% of patients refer persistence of pain. Although prosthesis components loosening is responsible for these complications in more than 90% of the cases, there are other potential causes of pain such as heterotopic ossification, muscle and tendon pain around the prosthesis, impingement and radiating back pain. In 1% of the cases the

There is a clear similarity between the aforementioned sources of ongoing pain after hip replacement and those reported in relation to persistence of pain after knee replacement. Since 1989, several authors have reported the use of arthroscopy as a diagnostic and therapeutic tool in painful complications of knee implants, Wasilewski being the earliest (Bocell et al., 1991; Johnson et al., 1990; Lawrence & Kan, 1992; Lucas et al., 1999; Markel et al., 1996; Scranton, 2001; Tzagarakis et al., 2001; Wasilewski & Frankl, 1989a, 1989b). The use of arthroscopy in selected patients with hip implants represents a step forward in diagnosis and possible treatment of painful, apparently well implanted prostheses (Cuéllar et al., 2009; McCarthy et al., 2009; Bajwa & Villar, 2011). In our hospital environment we have established an arthroscopic protocol for hip implant monitoring, similar to the approach we use in knee replacement patients and indicate arthroscopic surgery in cases in which, despite the prosthesis being apparently well implanted, patients continue to experience pain (Cuéllar et

The differential diagnosis of pain following THR is wide and includes intrinsic and extrinsic causes to the implant. Septic or aseptic loosening is the cause of intrinsic complications in more than 90% of cases, but there are other potential causes such as stress fractures, mechanical failure or elasticity of the implant itself, subluxation or impingement (Bozic & Rubash, 2004; Smith & Rorabeck, 1999). Additionally there are other extrinsic causes of pain including lumbar radicular pain, neurogenic or vascular claudication (Beck, 2009), heterotopic ossification, trochanteritis or trochanteric non-union (Brown & Callaghan, 2008), peripheral nerve lesions (Malik et al., 2007), tendon and muscle pain around the implant (adductor and iliopsoas tendinitis, arthrofibrosis) (Hyman et al., 1999), femoral or inguinal hernia, and, more rarely, concomitant malignant conditions (Merkel et al., 1985). Finally, in

The protocol that we routinely use for differential diagnosis includes a detailed medical history and a thorough clinical examination, laboratory tests (FBC, ESR, and CRP), Radiology investigations (X-rays, CT scan, and scintigraphy) and diagnostic nerve blocks. Of all the possible causes of pain (Bozic & Rubash, 2004; Smith & Rorabeck, 1999; Witvoët, 2001), we highlight those which we can be addressed using arthroscopy (Table 1): loosening (diagnostic value), tendon pain (iliopsoas, piriformis and plica syndromes or arthrofibrosis)

instruments with a minimum length of 16 cm (Monllau et al., 2003).

cause of pain remains unknown (Witvoët, 2001).

around 1% of cases the source of the pain is never found.

al., 2009).

**2. Differential diagnosis**

(Bajwa & Villar, 2011; Beck, 2009; Smith & Rorabeck, 1999), trochanteritis, subluxation and femoroacetabular impingement syndrome (Bajwa & Villar, 2011; Beck, 2009; Bozic & Rubash, 2004; Brown & Callaghan, 2008; Malik et al., 2007; Smith & Rorabeck, 1999), acute and sub-acute infection (Hyman et al., 1999; McCarthy et al., 2009), and pain of unknown origin (Bozic & Rubash, 2004; Witvoët, 2001).

Table 1**. Causes of pain following total Hip Replacement and indications for arthroscopic surgery**. In blue font: Indications for diagnostic hip arthroscopy; in red font: Indications for diagnostic and therapeutic hip; and in black: those conditions which cannot be addressed using arthroscopic surgery

### **2.1 Prosthesis loosening**

A battery of complementary tests is available for its diagnosis. These include blood tests (CRP and ESR), X-rays and particularly scintigraphy.

The combination of scintigraphy tests with Ga67, Tc99, and In111- labelled leukocytes has high sensitivity and specificity for the diagnosis of implant loosening and for distinguishing between septic and aseptic inflammation (Merkel et al., 1985, 1986; Rushton et al., 1982).

We routinely perform arthocentesis and take samples of synovial tissue from three or four areas around the prosthetic joint, as a first stage at the beginning of the surgical procedure. Samples were sent to the Pathology Unit. None of the patients receive antibiotic therapy for at least 5 days prior to the intervention and prophylaxis is not initiated until after the samples were taken. The assessment of signs of loosening is completed by applying force with a blunt-ended instrument to all the prosthetic components in turn and carrying out movements causing leverage under arthroscopy and fluoroscopic control (Fig-1).


*2.2. Fine Mapping of the YL Gene*

To unravel the molecular mechanism of the *yl* phenotype, we performed genetic mapping to isolate the *YL* gene. The *yl* mutant was crossed to two soybean cultivars with normal green leaves, Williams 82 and Zhonghuang 13, and three F2 mapping populations were produced by reciprocal crosses, *yl* × Williams 82, *yl* × Zhonghuang 13 and Zhonghuang 13 × *yl*. The leaf color of all F1 plants was normal green. The segregation ratio of green to yellow leaves appeared to be 3:1 in F2 populations, indicating that the *yl* phenotype is controlled by a single recessive nuclear gene (Table 1).

**Table 1.** Segregation pattern and chi-square tests for green/yellow leaves of F2 progeny from the crosses between *yl* and Williams 82 or Zhonghuang 13.

The *yl* mutation was primarily mapped on chromosome 20 between microsatellite markers Satt162 and Sat\_155, which were 9.9 centimorgans (cM) and 1.1 cM from *yl*, respectively (Figure 3A). The *YL* locus was ultimately fine mapped into a 28-kb interval between single nucleotide polymorphism (SNP) markers S3 and S7-3 (Figure 3A). According to the soybean gene annotation database (www. phytozome.net) [31], there were three putative open reading frames (ORFs) within this 28-kb region

(Figure 3A). We sequenced the 28-kb sequences between the wild type and *yl* mutant and found a C to A transition at the eighth exon of *Glyma.20G187000* (Figure 3B).

**Figure 3.** Fine mapping of the *YL* gene. (**A**) The *YL* locus was initially mapped to a region between markers Satt162 and Sat\_155 on soybean chromosome 20. The gene was finally delimited to a 28 kb region between markers S3 and S7-3. Three predicted open reading frames (ORFs) were within this region. (**B**) *YL* (*Glyma.20G187000*) structure indicating nine exons (gray boxes), eight introns (line segments between the exons), and 5 and 3 untranslated regions (white boxes with black frame). Start (ATG) and stop (TGA) codons are marked. The *yl* mutation in the *YL* gene is shown.