Abstract
We report the results of proximal femoral osteotomy that was performed to treat osteoarthrosis in twenty-three consecutive young adults (twenty-five hips) who had a mean age of thirty-eight years (range, eighteen to fifty-three years). The mean duration of follow-up was seven years (range, two to twelve years). With conversion to a total hip replacement as the end point, the rate of survival at twelve years was 67 per cent (95 per cent confidence interval, 37 to 88 per cent). Four hips (16 per cent) were converted to a total hip replacement at a mean of eight years after the osteotomy. For the patients who did not have conversion to a total hip replacement, the mean score for pain, according to the system of Merle d'Aubigné and Postel as modified by Charnley, improved from 3.4 points preoperatively to 5.1 points postoperatively, the mean score for walking ability improved from 3.9 to 4.7 points, and the mean score for range of motion improved from 3.2 to 4.2 points. These results compare favorably with those following other forms of operative treatment of osteoarthrosis of the hip in young adults. In addition, the osteotomy does not preclude subsequent replacement arthroplasty if one is necessary.
Total hip arthroplasty is thought to be an uncertain form of treatment for osteoarthrosis of the hip in young adults5,20. Early reports of the results of total hip replacement with cement in this age-group demonstrated a rate of survival of the prosthesis of only 76 per cent (twenty-two of twenty-nine hips) at five years6. The probability of survival at twenty years in another study was 51 per cent (twenty-nine of fifty-six hips)12. Various types of replacements have been tried. In one study of twenty-eight isoelastic Butel hip replacements (Smith and Nephew Richards, Memphis, Tennessee) performed without cement10, the rate of failure of the femoral component was 43 per cent (twelve hips) at four years. Kaplan-Meier survivorship analysis of 108 RM-Isoelastic hip replacements (Protek, Bern, Switzerland) performed without cement13 revealed a rate of survival of 80 per cent (95 per cent confidence interval, 77 to 92 per cent) at eight years. The rate of failure of P.C.A. (porous-coated anatomic) femoral components (Howmedica, Rutherford, New Jersey) was reported to be 11 per cent (three of twenty-eight hips) at four years11.
In addition to frank clinical failure, wear, the formation of particles, and secondary osteolysis are matters of concern when replacement procedures are considered in young adults. Although resurfacing was thought to be successful when it was first performed, it is not considered an established procedure now. The use of components with hydroxyapatite coating is promising, but the long-term results are not yet known8. Developments in cementing techniques have been shown to improve the results of total hip replacement18, and one study demonstrated a rate of survival of 75 per cent (thirty-three) of forty-four hips at ten years2. However, the results of hip replacements in younger adults remain, in general, less favorable than those in older adults18. Therefore, there are still doubts regarding the durability of currently used implants, the long-term problems associated with them, the reproducibility of the results, and the appropriateness of the procedure in young adults.
Preservation of bone stock with use of osteotomy in young adults is an attractive alternative to total hip replacement3,15,17,24. Osteotomies may be categorized as displacement or angulation techniques. The femoral osteotomy currently performed by most surgeons combines both techniques, and the possibility of a subsequent hip replacement4 is taken into consideration. The use of purely displacement osteotomies, such as medial displacement osteotomies16, has been mostly abandoned. Different theories3,14,16,22,26 have been proposed to explain the effects of osteotomy; these include an increase in the area of weight-bearing, reduction of joint force by alteration of the lever arm, reduction of joint force by division of muscles, and reduction of intramedullary pressure.
When we began the present study, intertrochanteric osteotomy was still thought of, at least in the United Kingdom, in terms of the largely uncontrolled medial displacement osteotomy described by McMurray and had, to a great extent, been abandoned as a practical form of treatment. At the same time, however, discussion was beginning regarding osteotomies based on biomechanical principles, such as that described by Bombelli, as based on the work of Pauwels.
In order to be considered for a valgus extension osteotomy, the patient has to have predominantly anterosuperolateral osteoarthrosis, a flattened or mushroom-shaped femoral head, an osteophyte on the medial side of the femoral head (the capital-drop osteophyte), and an osteophyte at least partially covering the true acetabular floor. The altered shape of the proximal aspect of the femur produced by the osteotomy (Fig. 1) shifts the center of stress from anterosuperolateral to medial between the capital-drop and the acetabular osteophyte. This medial displacement of the center of rotation of the hip, which is akin to the medial displacement of the socket originally advocated by Charnley for total hip replacement9, reduces the load on the hip. The abductor lever arm is largely maintained by elevation of the greater trochanter through insertion of part of the wedge of bone taken from the osteotomy as a graft under the trochanter. Extension recenters the femoral head in the sagittal plane and tends to prevent anterior subluxation. Joint-loading is reduced somewhat further by a psoas tenotomy and by transient weakening of the abductor muscles as a result of the procedure.
The requirements for a varus extension osteotomy are anterosuperolateral osteoarthrosis and a round femoral head. The main effects of the osteotomy are an increase in the abductor lever arm and a more horizontal direction to the resultant force on the hip, which tends to center the femoral head into the acetabulum. The principle of extension is the same as that with valgus osteotomy.
In 1981, few centers outside of mainland Europe had any experience with these techniques and no long-term results were available. However, because the principles seemed to have a great deal of merit, the senior one of us (M. D. N.-B.) decided to include intertrochanteric osteotomy with use of these principles and techniques as part of his armamentarium for the treatment of adults who were less than fifty years old21.
We reviewed the results of twenty-five proximal femoral osteotomies and subjected the results to survivorship analysis.
All patients who were fifty years old or less and were referred to the senior one of us, between December 1, 1981, and June 30, 1992, because of osteoarthrosis of the hip that was sufficiently symptomatic to merit consideration of operative treatment were assessed to determine if they were candidates for an osteotomy. The best procedure for patients who were more than fifty years old was believed to be total hip replacement, if the condition was sufficiently symptomatic. A few patients who were slightly more than fifty years old were also referred during the study period with a specific request that they be considered for osteotomy performed with the technique described by Bombelli because the referring surgeon thought that they were too young for a replacement. These patients were also assessed with regard to the suitability of osteotomy.
The patients were first evaluated in standard clinical fashion. The symptoms and physical signs were classified with use of the scoring system of Merle d'Aubigné and Postel, as modified by Charnley. With this system, pain, walking ability, and range of motion are each graded from 1 to 6 points, with 6 points indicating normal or no symptoms.
Next, plain anteroposterior and lateral radiographs were made. The shape of the femoral head and the locations of radiographic signs of excessive pressure on the joint surfaces, such as thinning of the cartilage, subchondral sclerosis, and cysts, were noted. A patient was considered as a possible candidate for intertrochanteric osteotomy only if the signs of excessive pressure were localized and in the common superolateral position on the anteroposterior radiographs and if similar signs were seen in this location on the lateral radiographs. Although we realize that patients who have medial (or protrusio-type) osteoarthrosis, which is usually associated with a varus deformity of the femoral neck, can be managed with valgus osteotomy3, such patients were not considered for an osteotomy in this series.
Patients who had superolateral osteoarthrosis with an elliptical femoral head were considered to be possible candidates for a valgus extension osteotomy, and those who had a round femoral head were considered to be possible candidates for a varus extension osteotomy. Periacetabular osteotomy was not yet being used to redirect the acetabulum during the study period.
The patients formed a very disparate group that ranged from young women who had mild symptoms (a pain score of 5 points, for example) and a mobile hip (a score for range of motion of 5 or even 6 points), often with a round femoral head, valgus deformity of the femoral neck, and early superolateral degenerative changes, to severely disabled patients (a pain score of 2 points, for example) who had marked stiffness (a score for range of motion of 2 points, for example) and severe secondary osteoarthrosis. We believed that patients at each of these extremes of the clinical spectrum could be managed correctly with osteotomy if the results of additional stress radiography indicated that such a procedure was appropriate, as will be described. We considered that osteotomy was appropriate for patients who had minor symptoms when it was clear from the clinical and radiographic assessment (often during a series of outpatient visits) that the symptoms would continue to worsen and the condition of the hip would continue to deteriorate. We believed that if operative treatment was delayed until the symptoms were considerably worse the hip would no longer be salvageable with an osteotomy. We found that patients often readily agreed to the osteotomy on this basis, particularly in light of the increased public understanding that the results of total hip replacement in this age-group are uncertain.
Stress radiographs were then made, almost always with the patient under general anesthesia, in the radiology department by the senior one of us, with use of image intensification and a facility for making plain radiographs. First, the range of motion of the hip with the patient under anesthesia was noted; it usually was considerably improved compared with the range noted when the patient was awake since pain can contribute to a decreased range of motion.
Flexion of at least 45 degrees and adduction of at least 20 degrees were prerequisites for a valgus extension osteotomy. The radiographic appearance of the hip in flexion and adduction was then assessed. Obvious radiographic evidence, under image intensification, of medial movement of the contact area and superolateral separation of the weight-bearing surfaces was considered to be an indication that a similar displacement achieved operatively would be effective, regardless of the severity of the osteoarthrosis.
A flexion arc of at least (but, preferably, considerably more than) 45 degrees was considered a prerequisite for a varus extension osteotomy. The essential feature on screening was that the femoral head move concentrically in the acetabulum.
At the conclusion of this examination, the patients were divided into three groups. One group consisted of patients who were not thought to be candidates for an osteotomy, and they were excluded from the present study. Most of these patients were thought to be candidates for joint replacement because they had very restricted motion of the hip, even under anesthesia, or they had an elliptical femoral head and a joint that did not open superolaterally on adduction. It was believed that a valgus extension osteotomy in such patients would not achieve medial displacement of the contact area. Patients who had a round femoral head that did not move easily and concentrically on adduction or a hip that showed any signs of hinge abduction were also eliminated from the present study. A small number of hips for which intertrochanteric osteotomy was contraindicated were considered candidates for acetabular augmentation with a Chiari osteotomy.
Another group consisted of patients who were thought to be possible candidates for an osteotomy but the indications were weak. The arguments for and against osteotomy were discussed in detail with these patients. Frequently, it was believed that operative treatment should be delayed until the symptoms worsened, at which time a joint replacement would be performed.
The patients in the final group were considered to be good candidates for a proximal femoral osteotomy and are the subjects of the present study. Radiographs to aid in the planning of the procedure were made before the patient left the radiology department. A precise decision was made regarding the valgus or varus correction angle, and the necessary extension was estimated; a definitive decision regarding extension was made intraoperatively. The osteotomies were performed during a separate hospital admission as soon as possible after the radiographs were made.
Twenty-five hips in twenty-three patients were included in the study (Table I). All of the preoperative evaluations, decision-making, and preoperative planning, and all but two of the operations, were done by the senior one of us. The remaining two operations (Cases 9 and 12), which were both valgus extension osteotomies, were carried out in our operating room, with exactly the same technique as was used for the other procedures, by Professor Bombelli himself. The thirteen men and ten women ranged in age from eighteen to fifty-three years (mean, thirty-eight years). Two patients had a bilateral osteotomy. The preoperative diagnosis was primary osteoarthrosis in eight hips and secondary osteoarthrosis in seventeen. Fifteen left hips and ten right hips were treated. Nineteen hips were treated with a valgus extension osteotomy and six were treated with a varus extension osteotomy. One of the hips that was treated with a varus extension osteotomy also had a Chiari osteotomy with anterior trochanteric transposition and advancement as part of a planned two-stage procedure; the blade-plate that had been used to fix the site of the varus osteotomy was removed at the time of the Chiari osteotomy.
The operations were performed with the technique used by Bombelli. The anterior aspect of the capsule was exposed through a lateral approach. For the valgus osteotomy, an extracapsular trochanteric osteotomy was performed, the capsule was opened, and the junction of the head and neck was defined. Guide-wires were inserted according to the preoperative plan to give the necessary correction, and the hip was flexed to increase anterior coverage, as judged with direct vision. The seating chisel was then inserted from laterally, usually through the distal part of the trochanteric bed, and its inner tip was inserted into the inferior half of the femoral head. The guide on the seating chisel was set at 130 degrees; the part of the guide that corresponded to the blade of the blade-plate was kept horizontal during insertion of the chisel in order to give the necessary degree of extension. The femoral osteotomy was performed by removal of a wedge of bone from the intertrochanteric region; the proximal limit of the osteotomy laterally was approximately two centimeters distal to the site of entry of the blade. The seating chisel was usually removed, and the blade-plate was partially inserted before the osteotomy was completed so that the blade would go up the correct track. The distal fragment was then displaced outward, and the iliopsoas tendon was released. The lower limb was moved from its flexed position into neutral rotation. The osteotomy site was reduced and was then fixed with a 130-degree four-hole AO/ASIF angled blade-plate (Stratec Medical, Hertfordshire, United Kingdom); the plate was fixed under compression, and the shaft was displaced laterally. The wedge of bone taken from the main osteotomy site was divided into two pieces. One piece was placed under the knuckle of the plate, and the other was put into the site of the trochanteric osteotomy to increase the abductor lever arm.
The varus osteotomy was performed with a similar technique, but a 90-degree blade-plate was used without a trochanteric osteotomy and a wedge was not taken from the main osteotomy site.
Postoperatively, the patients remained in bed for about two weeks, during which time they performed active exercises of the hip. After two weeks, the patients were allowed to walk with strict non-weight-bearing and crutches, to allow the osteotomy site to heal, for six weeks. They were also taught a sequence of exercises, as recommended by Bombelli, to do regularly at home; these exercises, which involved partial weight-bearing, included flexion, abduction, and abductor-muscle exercises as well as adduction movements with the patient supporting himself or herself against a bar and standing on the untreated limb while adducting the treated limb in front of and behind the contralateral limb. Rotational movements were also recommended, together with gradually increasing use of an exercise bicycle, if available. In addition, some of the patients who were managed early in the series came to the hospital for physiotherapy. All of the patients continued to use two crutches with restricted weight-bearing until three to four months postoperatively and were then encouraged to continue to use a walking aid until about six months after the operation, if feasible. Compliance with this regimen was not verified.
The patients were examined three months and one year postoperatively and then at yearly intervals. The duration of follow-up ranged from two to twelve years (mean, seven years). One patient (Case 8) was lost to follow-up after two years. For the survivorship analysis, the date of the final review was June 30, 1994.
The mean angular correction was 27 degrees (range, 20 to 40 degrees) in the hips that were treated with a valgus osteotomy (Figs. 2-A, 2-B, 2-C, 3-A and 3-B) and 26 degrees (range, 20 to 30 degrees) in the hips that were treated with a varus osteotomy (Figs. 4-A and 4-B). The mean extension for the two groups combined was 29 degrees (range, 10 to 40 degrees). We did not usually record the degree of rotation needed to bring the limb into neutral before the osteotomy, but one patient, who had a severe external rotation deformity as a result of a previous slipped capital femoral epiphysis, needed about 30 degrees of internal rotation. Another patient needed about 30 degrees of external rotation.
Four patients had a conversion to a Charnley low-friction arthroplasty at five, seven, nine, and ten years postoperatively. The patient (Case 8) who was lost to follow-up (a man who was twenty years old at the time of the operation) had extremely good function and was working full-time as a pipe layer two years postoperatively. Attempts to contact him after two years were not successful. Although it is possible that he had a later conversion to a hip replacement performed elsewhere, it does not seem likely.
The mean pain score improved from 3.3 points preoperatively to 4.7 points at the time of the most recent follow-up or the last follow-up examination before conversion to a total hip replacement. When the hips that had an arthroplasty were excluded, the improvement in the mean pain score was from 3.4 points preoperatively to 5.1 points at the time of follow-up. Preoperatively, one hip had a score of 2 points, eighteen had a score of 3 points, four had a score of 4 points, and two had a score of 5 points. At the most recent follow-up examination, two hips had a score of 2 points, three had a score of 3 points, three had a score of 4 points, nine had a score of 5 points, and eight had a score of 6 points.
The mean score for walking ability improved from 3.8 points preoperatively to 4.4 points at the most recent follow-up examination or the last follow-up visit before conversion. When the hips that had an arthroplasty were excluded, the improvement in the mean score was from 3.9 points preoperatively to 4.7 points at the time of follow-up. Preoperatively, thirteen hips had a score of 3 points, four had a score of 4 points, and eight had a score of 5 points. At the most recent follow-up examination, six hips had a score of 3 points, eight had a score of 4 points, six had a score of 5 points, and five had a score of 6 points.
The mean score for range of motion improved from 3.0 points preoperatively to 4.0 points at the most recent follow-up examination or the last one before conversion. When the hips that had an arthroplasty were excluded, the improvement in the mean score was from 3.2 points preoperatively to 4.2 points at the time of follow-up. This increase in motion was probably due to a combination of two factors: reduction of muscular spasm through relief of the pain, similar to that seen at the initial examination under anesthesia, and true structural change in the hip with a decrease in the severity of the osteoarthrosis.
Thus, with the hips that had an arthroplasty excluded from the analysis, the improvement in the mean pain score, compared with the preoperative value, was substantial (1.7 points); the improvements in the score for walking ability (0.8 point) and the score for range of motion (1.0 point) were somewhat smaller.
Complications
Two patients had an early complication: one had a hematoma that necessitated operative drainage, and the other had a superficial infection. Neither complication led to problems later. A persistent adduction deformity developed in a third patient (Case 4) after a valgus osteotomy, possibly because of intraoperative technical difficulties related to the abductor repair. This patient was one of the four who had a subsequent conversion to a total hip replacement. The only other serious complication related to the operation was delayed union, which occurred in a heavy, active man (Case 24) who had severe bilateral hip disease. After the patient had been examined under anesthesia preoperatively, it was decided that one hip would be treated with a valgus extension osteotomy and the other, with resurfacing. The osteotomy was done first, and the contralateral hip was resurfaced as soon as it was believed to be safe to do so. During the recovery after the resurfacing, the level of pain increased on the side of the osteotomy, and a radiograph showed breakage of all of the screws that had been holding the plate to the femoral shaft as well as delayed union with some loss of position. The site of the osteotomy was fixed, nine months after the osteotomy had been performed, with use of the original plate supplemented with autogenous cancellous-bone graft. The planned valgus rotation and extension were accurately restored, and the end result was not affected.
Conversion to Total Hip Replacement
Failure of the osteotomy in one patient (Case 25) was probably related to his age at the time of the operation (fifty-three years) as well as to the severity of the osteoarthrosis. In another patient (Case 9), the superolateral opening seen on the stress radiographs may not have been sufficient. The other two patients, both women who had congenital dislocation of the hip, did not have any radiographic improvement postoperatively. This was thought to be the result of a possible technical error in one patient (Case 4), who had a persistent adduction deformity that necessitated an adductor tenotomy, as discussed earlier. In the other patient (Case 12), there was a suggestion that the planned corrections had not been achieved with full accuracy at the time of the osteotomy, but it is not certain whether a better result would have been achieved had these problems not occurred.
Radiographic Evaluation
The degree of osteoarthrosis (mild, moderate, or severe) was determined on the basis of the preoperative radiographs. Two hips had mild osteoarthrosis, eighteen had moderate osteoarthrosis, and five had severe osteoarthrosis.
The follow-up radiographs were evaluated, with particular attention paid to the width or uniformity of the radiographic joint space, or both; any changes in the acetabular subchondral bone (sourcil); and any changes in the osteoarthrotic appearance of the substance of the femoral head (Table I). A marked improvement in the overall appearance, with a gradual increase in the width of the joint space of about two millimeters or more, was seen in seven hips. Moderate improvement was seen in eight hips. No apparent change apart from that due to repositioning of the femoral head was seen in five hips. One hip had radiographic deterioration after early improvement. All four hips that were converted to a total hip replacement had deteriorated radiographically.
Survivorship Analysis
A life table (Table II) was constructed1. The number of hips at risk was calculated at the start of each postoperative year, and the probability of survival (with conversion to total hip replacement as the end point) was determined. There were no deaths. The rate of survival at twelve years was 67 per cent (95 per cent confidence interval, 37 to 88 per cent) (Fig. 5).
A review of the literature suggests that intertrochanteric osteotomy can be an effective treatment for osteoarthrosis of the hip in carefully selected young patients, but it is less effective in patients who have primary hip disease or a reduced range of motion17,24,25. Bombelli himself reported that 188 (68 per cent) of 277 patients had an excellent or good result eleven to fifteen years after a valgus extension osteotomy that he had performed, but the precise criteria for the categorization of the results were not given17. The results of intertrochanteric osteotomy have tended to be unpredictable, and no clear pattern has emerged to indicate the likelihood of a successful result in a given patient23,26-28. Some authors have reported better results in patients who had a broken Shenton line20 and pain at rest preoperatively or in patients who had early radiographic changes15. Most authors17,26 have reported the best results in patients who are less than forty years old and have unilateral involvement. It has been thought that an osteotomy should not be performed in patients who have marked restriction of motion as the range of motion is not improved postoperatively3,24. Clearly, the osteotomy should not jeopardize any subsequent operative procedures, such as arthroplasty4; therefore, osteotomy with major displacement of the femoral shaft should be avoided if possible10.
Our results support the concept that osteotomy can produce a biological reconstruction of the hip joint. Fifteen hips (60 per cent) in the present study had radiographic improvement postoperatively; approximately half of these had marked improvement. Our preoperative workup was very exacting, and we do not think that any additional refinements would have improved these results as there is probably an irreducible degree of biological unpredictability. The radiographic improvement in many hips was obvious and was usually accompanied by a decrease in symptoms. Although the treatment might have been better for some of the hips that subsequently had conversion to a total hip replacement, the lack of completely uniform success almost certainly was related to inevitable biological limitations, such as those related to union of fractures and many other naturally occurring healing processes. However, we did not find any obvious evidence of an upper age-limit for the osteotomy. Several patients who were in their forties did well. However, of the two patients who were fifty-three years old (the maximum age in the series), one had early conversion to a total hip replacement despite an apparently perfect technical procedure. With the continuing improvements in joint replacement, we would not now consider performing an osteotomy in a patient who was more than fifty years old.
Although relatively few of our patients had severe osteoarthrosis, this is not necessarily a contraindication to osteotomy, provided that the stress-radiography criteria are strictly met. Such patients must be warned, however, that the purpose of the procedure is to relieve pain and that the gain in motion, although likely to be large enough to be useful, will be limited.
While we did not analyze it specifically, the elimination of a fixed deformity seemed to influence some of our patients' satisfaction with the clinical result. Although only a small number of our patients had a varus osteotomy, and one of them also had a Chiari osteotomy, it should be noted that all of these patients did well. Nevertheless, varus osteotomy is accompanied by some inevitable shortening as well as a greater prominence of the trochanteric region on the treated side, which young women in particular may not like. In a number of these patients, the morphological abnormality was a combination of genu valgum and a degree of acetabular dysplasia; we now tend to manage such patients with a periacetabular osteotomy.
We think that a patient who has bilateral hip disease with marked stiffness should first have an osteotomy on the side with the strongest indications for that procedure and then have a joint replacement on the contralateral side. With this approach, there is a good chance that the patient will have marked improvement in the range of motion of one hip, albeit with the limitations imposed by the prosthesis. We do not think that there is any contraindication to a bilateral osteotomy when the hips are mobile.
It is well accepted that conversion to hip replacement is less straightforward than primary replacement. However, one of the merits of the osteotomy that we have described is that the shape of the proximal aspect of the femur is not greatly changed after healing. Thus, the difficulties with a subsequent total hip replacement are relatively minor and are far less substantial than those associated with conversion of the older types of osteotomy that involved major side-to-side displacement of the shaft in the intertrochanteric region.
Our results with regard to symptoms were generally not as good as those of a properly executed hip replacement, after which scores of 5 or 6 points for pain, walking ability, and range of motion are the norm. Thus, although pain relief was more than adequate, with a mean improvement from 3.4 to 5.1 points for the hips that did not subsequently have a total hip arthroplasty, it usually was not as complete, and the mean scores for walking ability (4.7 points) and range of motion (4.2 points) at the latest follow-up examination were still considerably lower than those for a normal hip. Nevertheless, in our experience these imperfections are often readily accepted by a younger person, since the possible long-term deficiencies associated with total hip replacement are now well known.
Another advantage of osteotomy is that the result is durable. Overuse of the limb may cause transient symptoms but is not likely to lead to an acute complication or to an earlier conversion to a total hip replacement. In the present study, the rate of survival at twelve years was 67 per cent. This makes osteotomy particularly applicable to younger, active patients. The decision to perform an osteotomy, however, is not an easy one; it requires careful assessment of the patient and his or her expectations as well as concern for the long-term results and for the hip itself. Thus, a man in his forties may prefer the durability of a hip that has been treated with an osteotomy, whereas a woman of the same age may prefer the perfect function obtained with a replacement. A disadvantage of osteotomy that must be seriously considered is the duration of the postoperative rehabilitation because these patients are still of working age, unlike many patients who have a replacement.
Proximal femoral osteotomy remains a valuable option for the management of young adults who have osteoarthrosis of the hip, provided that it is preceded by very careful evaluation and selection of patients. However, it should be viewed as an integral procedure with total hip replacement performed at a later stage.
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