
 surgical management of displaced subcapital fractures of the femoral neck continues to be challenging .
internal fixation , hemiarthroplasty , and total hip replacement could be considered as appropriate solutions . for internal fixation , most orthopaedic surgeons choose either a dynamic hip screw ( dhs ) or multiple cannulated screws ( mcs ) .
osteosynthesis with mcs fixation is a less invasive technique and reduces blood loss and soft tissue stripping [ 13 ] . with the use of dhs
published a biomechanical comparison of internal fixation techniques for the treatment of unstable basicervical femoral neck fractures .
its disadvantages are large skin incisions , more extensive soft tissue dissection , a greater need for blood transfusion , and a longer stay in hospital . in a cross - sectional survey using a regressive analysis , bhandari et al .   suggested that surgeons in europe were more likely to indicate a dhs device over mcs than north american surgeons .
defended the use of only two cannulated screws in nondisplaced femoral neck fractures but suggested dhs , as a more stable implant , for garden iii - iv fractures .
, after reviewing 90 fractures , concluded that dhs showed a trend for an increased rate of overall success in elderly patients with nondisplaced femoral neck fracture compared with mcs .
there are few published reports focusing on dhs in the treatment of femoral intracapsular displaced neck fractures .
they reviewed 25 randomized trials and concluded that most studies have had an insufficient number of subjects to permit a valid comparison .
.   found overall failure in 15.9% of cases using mcs and in 2.5% of cases using dhs .
chen et al . , using dhs in extracapsular basicervical neck fractures , achieved union in 97.5% of their patients , with no cases of avascular necrosis and 1.7% of nonunion .
osteosynthesis not only has the potential to offer normal hip function after fracture consolidation but also has a relatively high rate of failure and complications in the form of nonunion , avascular necrosis , redisplacement , and so forth .
the purpose of the present study was to correlate the incidence of avascular necrosis following treatment with the dhs with patient demographics , time elapsed from the fracture to surgery , quality of reduction , garden 's classification , and the position of the screw in the head .
the present study prospectively evaluated 96 patients who had subcapital fractures of the femoral neck and were assigned to close reduction and internal fixation with dhs .
the inclusion criterion was subcapital fractures of the femoral neck and not tumoral ones , whereas exclusion criteria were bad quality x - rays pre- or postoperatively , more than a week since fracture , comminuted fractures , dislocated fractures classified as garden iii and iv in patients older than 75 years , rheumatoid arthritis and metabolic diseases ( including osteoporosis singh stage iii or less ) , and incomplete records .
we prospectively followed 128 patients , but 32 cases were excluded from the final analysis according to the exclusion criteria .
four patients died but were still included , because they died 3 years , 4 years and 6 months , 8 years , and 7 years , respectively , after the onset of fracture .
all surgeries were performed by closed reduction , on a standard fracture table assisted by fluoroscopy .
if the fracture was incompletely reduced , small incremental increases in both traction and internal rotation were subsequently performed , checking the position after each adjustment .
a standard internal fixation with a 135 dhs was used , varying the number of screws and length of the plate as required .
reduction was judged on both the anterior - posterior ( ap ) and lateral views .
the junction of the convex femoral head and neck should produce an s - shaped curve in all planes .
a valgus reduction is inherently more stable , whereas a varus reduction is associated with a much higher risk of fixation failure .
what constitutes an acceptable reduction is debatable , and arnold   recommended that there should be less than 20 degrees of posterior angulation to minimize the risk of fixation failure .
garden   described an alignment index to measure the quality of reduction , which was used in the present work .
demographics , age at the onset of fracture , trauma mechanism , garden 's classification , associated fractures , time elapsed to surgery , american society of anaesthesiologists ' ( asa )   criteria , baumgaertner index , and hospital discharge were evaluated . the tip - apex distance ( tad ) of all lag screws was measured , as described by baumgaertner et al . ,
and the position of the screw in the head was classified in the anterior - posterior projection as high , middle , or low .
the same was done in the lateral projection , classifying the position as anterior , central , or posterior .
the accepted definition of union was the development of a well - established trabecular pattern across the fracture site within 6 months following the date of injury .
avascular necrosis of the femoral head was diagnosed based on progressive pain with the classic mottled appearance , increasing radiodensity , segmental collapse , and degenerative changes .
the fisher method of statistical analysis was used to correlate all possible positions of the screw in the head with avascular necrosis .

 table 1 presents the characteristics of the 96 patients . there were 56 ( 58% ) males and 40 ( 42% ) females with an overall mean age at the onset of fracture of 53 years ( 14 ) , ranging from 18 to 70 years .
sixteen ( 16% ) had fallen from height and three ( 3% ) were victims of automobile traffic trauma .
with respect to garden 's classification for femoral neck fractures , 58 ( 60% ) were identified as garden iv , 25 ( 26% ) were garden iii , and 13 ( 14% ) were garden ii .
fifty patients ( 52% ) had fractures of the right hip and 46 ( 48% ) of the left one .
eleven patients had associated fractures : three distal radius fractures , three rib fractures , two ankle fractures , two proximal humeral fractures , and one tibial shaft fracture . only one ( 1% ) patient was operated on in the first 24 hours .
fifty - five ( 57% ) patients were operated on between 24 to 72 hours after fracture .
when considering clinical conditions , 68 ( 71% ) were considered asa i ( normal healthy ) and 28 ( 29% ) were asa ii ( mild systemic disease ) .
the dhs plate was fixed with two screws in five patients ( 5% ) , while three screws were used in 61 patients ( 64% ) , and four screws in 30 patients ( 31% ) .
good reduction was obtained in 94 ( 98% ) of the patients , which means normal or slightly valgus reduction .
the average hospital discharge was 9 days . the greatest penetration into the femoral head for the lag screw of the dhs was 66  mm , whereas the least penetration was 31  mm , with an average of 42.3  mm .
the mean tad was 16  mm ( ranging from 11 to 24  mm ) .
a satisfactory union was achieved in 80 patients , with a failure rate of about 20% .
three patients failed to show union after 6 months ( 3% ) and presented criteria justifying surgical reintervention . in these cases ,
the radiographs showed no radiological signs of consolidation , with resorption of the fracture , pain , and synthesis failure .
all of these nonunions were treated with a valgus intertrochanteric osteotomy , all of them achieving successful healing .
sixteen cases of avascular necrosis were observed ( 16% ) , ten of which were classified as ficat 3 and six as ficat 4 .
most of our patients ( 58% ; 56/96 ) were operated on in the first 72 hours . however
, a substantial number was operated on after 72 hours ( 42% ; 40/96 ) .
the percentage of osteonecrosis in the latter group was 23% ( 9/40 ) , being almost double that of the former ( 13% ; 7/56 ) .
four fractures healed with shortening of the femoral neck of less than 15  mm .
we also analysed the screw position based on all nine possibilities presented in figure 1 for the ap and lateral projections ( see also table 2 ) and correlated them with osteonecrosis .
the most frequent position was middle ( ap ) and central ( lateral view ) , as observed in 47 patients ( 49% ) , with four cases of osteonecrosis ( 9% ; 4/47 ) .
the combination high ( ap ) and anterior ( lateral ) was observed in eight fractures ( 8% ) and five of these patients developed osteonecrosis ( 63% ; 5/8 ) .
this was the only statistically significant association between screw placement and osteonecrosis ( p = 0.0029 , using fisher 's correction ) .
regarding the d ' aubign and postel score , sixty patients ( 63% ) scored 18 points , 18 ( 19% ) scored 17 points , and 18 ( 19% ) scored less than 17 points .
we correlated age , gender , side , time elapsed until surgery , garden 's classification , and quality of reduction with avascular necrosis and no statistical differences were found , but when we analysed the position of the screw in the femoral head we found a significant correlation between necrosis and the high , anterior position ( p = 0.003 ) .
the treatment of displaced femoral neck fractures has been debated for many years . the main question during decision making is whether to fix or replace the femoral neck .
many recently published papers have shown that a primary total hip replacement is superior to internal fixation for the treatment of displaced femoral neck fractures when performed in a relatively healthy and mentally competent elderly patient [ 5 , 7 , 1820 ] . however , the optimal treatment for a young or adult patient under 70 years old is controversial , as the younger the patient is , the more the orthopaedic surgeon is obliged to pursue internal fixation .
there are many factors that could influence the decision : the preinjury functional status regarding gait , mental ability , and habitat , but the most important consideration is probably the difference between chronological and biological age .
criticisms against internal fixation are due to its association with high rates of failure due to loss of fixation , osteonecrosis , and nonunion
. nevertheless , when a femoral head heals over the neck , the patient has the chance of regaining his physiologically normal hip .
lu - yao et al .   published a meta - analysis of 106 published reports and concluded that the rate of loss of fixation or reduction after open reduction and internal fixation ( orif ) is about 16% ( 927% ) , which is significantly higher than the risk of dislocation after hemiarthroplasty ( 2% ) or total hip replacement .
tronzo   identified more than 100 different available implants for orif of femoral neck fractures .
however , if a surgeon chooses orif , he basically must decide between two consecrated techniques : multiple cannulated screws ( mcs ) or a dynamic hip screw ( dhs ) .
several studies have attempted to identify predictive factors of failure in femoral neck fracture treatment .
there is little agreement among these studies regarding which fractures are more likely to fail because they analysed both displaced and nondisplaced fractures , different clinical and radiological factors , different implants for internal fixation , different weight - bearing times , and so forth .
the results of osteosynthesis in young patients are debatable by presenting a considerable complication rate .
however , there is little doubt that the main complication is the occurrence of osteonecrosis .
many variables have been hypothesized to be associated with this complication after femoral neck fractures .
the literature does not support differences regarding gender , but high rates of nonunion and avascular necrosis are more common in young adult patients .
various explanations have been elaborated , including high energy trauma and its correlation with dislocated fractures in the young adult .
, while operating on 25 young adults on an ordinary table using the traditional watson - jones approach , described three cases of osteonecrosis ( 12% ) .
protzman and burkhalter , reviewing 22 fractures in young patients aged under 40 years , found 86% of necrosis .
we divided our cases according to age into two main groups : under 50 years ( 46 fractures ) and over 50 years ( 50 fractures ) .
the incidence of osteonecrosis was 22% ( 10/46 ) in the first group and 12% ( 6/50 ) in the second one .
the author divided the fractures into not displaced ( garden i and ii ) or displaced ( garden iii and iv ) . in our study , only 13 fractures were considered nondisplaced ( 14% ) and 83 were considered displaced ( 86% ) .
we did not find any osteonecrosis in the first group , while there was an incidence of 19% ( 16/83 ) in the second group ( p = 0.12 ) .
conn and parker , when evaluating 375 nondisplaced fractures , observed necrosis in 4% ( 15/375 ) .
reviewed 84 cases of nondisplaced fractures and found an incidence of about 10% ( 8/84 ) .
this complication is more frequent . in an extensive meta - analysis , lu - yao et al
observed 13.4% ( 9/64 ) after a minimum of 5 years of follow - up .
haidukewych   found 27% ( 14/51 ) , and nikolopoulos et al .   found 39.4% in displaced fractures ( 15 out of 38 ) after a mean follow - up of 4.7 years .
kaplan et al .   recently performed a study comparing open and closed reduction with internal fixation .
, in their historical paper , describe a long - term follow - up of 1503 subcapital fractures and conclude that the mortality rate increased when operation was delayed beyond 3 days following injury , but no significant difference was found in necrosis or late segmental collapse when delaying the operation up to 1 week .
most of our patients were operated on in the first 72 hours ( 58% ; 56/96 ) .
however , a substantial number was operated on after 72 hours : 42% ( 40/96 ) .
the percentage of osteonecrosis in the latter group was 23% ( 9/40 ) , being almost double that of the former : 13% ( 7/56 ) .
this suggests that it could be worse to fix the fracture more than 72 hours after the fracture 's onset , but no statistical difference was found between operating earlier or later in terms of necrosis ( p = 0.41 ) .
advocates of early surgery suggest that prompt reduction can produce an  unkinking  of the proximal femoral vessels , thus leading to intracapsular decompression , restoring the blood flow to the femoral head and minimizing the risk of necrosis [ 33 , 34 ] .
other studies confirm that early surgery may decrease the rate of femoral head osteonecrosis [ 3538 ] . on the contrary ,
several studies have reported no difference in the rate of osteonecrosis with more than a 24-hour delay .
upadhyay et al .   performed a prospective and randomized study of 102 patients , comparing open and closed reduction with internal fixation .
time to surgery did not affect the development of osteonecrosis . in a retrospective review of 73
he reported that 25% ( 17/73 ) of femoral neck fractures that were treated within 24 hours of diagnosis developed osteonecrosis .
twenty percent of the fractures that were internally fixed after 24 hours developed the same complication ( 4/20 ) .
most authors agree that the best position is anatomical reduction or a slight valgus [ 6 , 32 , 38 ] . in our study , of the 96 fractures we considered as a good quality reduction , necrosis occurred in 16 cases ( 16% ) .
there is a consensus that the anterior - superior position should be avoided [ 8 , 16 , 32 ] .
were probably the first to call attention to the fact that a nail or screw placed too superior and anterior in the femoral head was associated with a considerable failure rate in women ( 37% in garden iii and 52% in garden iv ) .
however , the present research demonstrates that the incidence of osteonecrosis is correlated with the position of the screw in the femoral head . since barnes et al
's study , there has been no paper in the literature regarding the position of the screw in relation to avascular necrosis .
they were the first to call attention to the association between the anterior - superior position of the screw and worse results .
the authors recognize that the present study has a nonrandomized nature , absence of control group , and a small number of patients , but we realize that our findings , although preliminary , are similar in relation to necrosis when comparing to the literature .
no statistically significant association was found between gender , time elapsed to surgery , quality of reduction and fracture displacement , and the onset of avascular necrosis of the femoral head .
the incidence of osteonecrosis in patients under 50 years was twofold higher than in patients over 50 years of age , but this difference was not statistically significant .
the incidence of osteonecrosis was associated with the  high and anterior  position of the screw in the femoral head .
 
 objectives . to study the correlation between avascular necrosis and the demographics , time elapsed from fracture to surgery , quality of reduction , garden classification , and the position of the screw following use of the dynamic hip screw ( dhs ) in the treatment of subcapital neck fractures . methods . 
 a prospective study of 96 patients with subcapital neck fractures was carried out in a faculty hospital . 
 patients underwent surgery with closed reduction and internal fixation with dhs . results . 
 there were 58% male and 42% female patients , with a mean age of 53 years ( + /14 ) . in terms of garden classification , 60% were garden iv , 26% were garden iii , and 14% were garden ii . 
 nonunion was observed in three cases ( 3% ) and was treated with valgus intertrochanteric osteotomy , in all cases leading to successful healing . 
 avascular necrosis was observed in 16% of patients . 
 the positioning of the screw into the femoral head showed a significant correlation with necrosis . 
 conclusions . 
 the incidence of necrosis in patients under the age of 50 years is twice as high as that in older patients . 
 displacement is a predictive factor regarding osteonecrosis and is associated with a high and anterior position of the screw in the femoral head . 
 level ii of evidence . 
 study type : therapeutic study . 
1. Introduction
2. Materials and Methods
3. Results
4. Discussion
5. Conclusions