Treatment of Femoro-Acetabular Impingement with Surgical Dislocation and Débridement in Young Adults

Peters, Christopher L. MD; Erickson, Jill A. PA-C

Journal of Bone & Joint Surgery - American Volume: August 2006 - Volume 88 - Issue 8 - p 1735–1741
doi: 10.2106/JBJS.E.00514
Scientific Articles

Background: Femoro-acetabular impingement has been associated with acetabular labral and/or articular cartilage damage that may ultimately result in osteoarthritis of the hip. Surgical treatment of femoro-acetabular impingement is directed at restoring a more normal femoral head-neck offset to alleviate femoral abutment against the acetabular rim and treating associated labral and articular cartilage damage.

Methods: Thirty hips with femoro-acetabular impingement (in twenty-nine patients) underwent débridement through a greater trochanteric flip osteotomy and anterior dislocation of the femoral head. There were sixteen male patients and thirteen female patients with a mean age of thirty-one years. Cam (femoral based) impingement was noted in fourteen hips; pincer (acetabular based) impingement, in one hip; and combined cam and pincer impingement, in fifteen hips. The mean duration of clinical and radiographic follow-up was thirty-two months. All patients were followed according to a prospective protocol, with Harris hip scores and plain radiographs obtained preoperatively and at six months, one year, and annually for a minimum of two years.

Results: The mean Harris hip score improved from 70 points preoperatively to 87 points at the time of final follow-up (p < 0.0001). Osteonecrosis did not develop in any hip, and there were no trochanteric nonunions. In eighteen hips, severe damage of the acetabular articular cartilage that had not been appreciated on preoperative plain radiographs or magnetic resonance arthrography was noted on arthrotomy. Eight of these eighteen hips subsequently had radiographic evidence of progression of the osteoarthritis, and four of the eight hips required or were expected to soon require conversion to a total hip arthroplasty to treat progressive pain.

Conclusions: At the time of early follow-up, we found that surgical dislocation and débridement of the hip for the treatment of femoro-acetabular impingement in hips without substantial damage to the articular cartilage can reduce pain and improve function. This procedure has a low rate of complications. Radiographic signs of progression of osteoarthritis and clinical failure requiring conversion to a total hip arthroplasty were seen only in patients with severe damage to the acetabular articular cartilage, a finding that emphasizes the need for better imaging methods to assess the extent of damage to the acetabular articular cartilage in patients with this disorder.

Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

1 Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, UT 84108. E-mail address for C.L. Peters: Chris.Peters@hsc.utah.edu

Article Outline

Femoro-acetabular impingement, or abutment of the anterior femoral head-neck junction against the anterior aspect of the acetabular rim or labrum, has been recently described1-6. This disorder was first recognized as a consequence of periacetabular osteotomy, occurring when a dysplastic acetabulum was repositioned into a more anterior and lateral position, thereby allowing the proximal part of a femur with insufficient femoral head-neck offset to abut against the newly positioned anterior aspect of the acetabular rim in flexion, internal rotation, and adduction of the hip7. Femoro-acetabular impingement was subsequently recognized in active young adults who presented with groin pain and who had not had a periacetabular osteotomy2,5,8-10.

Initial surgical observations during arthrotomies done to treat femoro-acetabular impingement demonstrated damage to the anterior aspect of the acetabular labrum and to the underlying articular cartilage1. In many respects, these findings were consistent with the impingement-like processes seen in hips of patients with Legg-Calvé-Perthes disease or slipped capital femoral epiphysis, conditions that have in common a reduction in the femoral head-neck offset8,9,11. In these conditions, damage to the anterior aspect of the acetabular labrum and the hyaline cartilage can lead to the development of early osteoarthritis of the hip12-16.

Because of the apparent relationship between femoroacetabular impingement and the development of early osteoarthritis of the hip, Ganz and others advocated early surgical intervention in symptomatic hips1-4,8,11,17,18. The surgical goal is to eliminate impingement of the femoral head-neck junction on the anterior aspect of the acetabular rim by débriding the excessive bone from the femoral head and neck and/or reorienting the anterior aspect of the acetabulum with a periacetabular osteotomy. To allow complete visualization of the intra-articular proximal part of the femur and acetabulum, Ganz et al. described a safe method for surgical dislocation of the femoral head by means of a trochanteric flip osteotomy and anterior capsulotomy, thereby preserving the posteriorly based femoral head blood supply19-21.

Other than the report by Beck et al.1, only one study (of twenty-three hips) regarding surgical débridement for the treatment of femoro-acetabular impingement22 has been published, to our knowledge. The purpose of the present review was to investigate the early clinical results of surgical dislocation and débridement for the treatment of femoro-acetabular impingement at a tertiary care referral center specializing in dysplastic conditions of the hip in adolescents and young adults. Our goal was to better define optimum patient selection and the limitations of surgical treatment.

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Materials and Methods

Our institutional review board approved this study. Between 2000 and 2003, thirty hips in twenty-nine patients underwent anterior dislocation and débridement for the treatment of femoro-acetabular impingement by the senior author (C.L.P.). The specific diagnoses were primary femoro-acetabular impingement in twenty-five patients (twenty-six hips), Legg-Calvé Perthes disease in three patients (three hips), and slipped capital femoral epiphysis in one patient (one hip). Fourteen patients (fourteen hips) had cam-type impingement, one patient (one hip) had pincer-type impingement, and fourteen patients (fifteen hips) had combined cam and pincer-type impingement (Fig. 1)7,10.

The study included thirteen female and sixteen male patients with an average age of thirty-one years (range, sixteen to fifty-one years). The right side was involved in fifteen patients and the left side, in thirteen patients. One female patient had bilateral staged procedures. The average patient height was 68 in (1.7 m) (range, 62 to 75 in [1.6 to 1.9 m]), and the average body mass index was 26.6 (range, 16.8 to 34.4). Six patients (six hips) had undergone prior procedures (see Appendix).

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Clinical Evaluation

The characteristic symptoms of the femoro-acetabular impingement included anterior groin pain with flexion activities such as sitting, squatting, or certain work-specific maneuvers. On physical examination, we recorded the ranges of motion of both hips in full extension, in 90° of flexion, and in maximum flexion if >90° of flexion was permitted. The impingement test, performed in 90° of flexion with internal rotation and adduction of the femur, produced pain in all patients2. A fluoroscopically guided intra-articular hip injection with local anesthetic and corticosteroid was utilized in many, but not all, patients to further corroborate that signs and symptoms were caused by an intra-articular pathological condition.

Patients were followed prospectively according to a clinical and radiographic protocol that we have used for all patients treated for hip dysplasia with bioregenerative surgery since 1997. Clinical results were graded with the Harris hip score, which was measured preoperatively, at six months and one year postoperatively, and then yearly for a minimum of two years. A physician assistant (J.A.E.) who is a member of our adult reconstruction service performed the clinical and radiographic evaluations. Clinical failure was defined as progressive pain that was unresponsive to nonoperative management, conversion to a total hip arthroplasty, or a Harris hip score at the time of final follow-up that was lower than the preoperative score.

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Radiographic Evaluation

All thirty hips had standing anteroposterior pelvic and lateral cross-table radiographs made preoperatively, immediately postoperatively, at six weeks, at six months, and then yearly1. Radiographic measurements included version of the acetabulum7,10,23, the articulotrochanteric distance24, and the center-edge angle of Wiberg25. We also evaluated the radiographs for any evidence of postoperative osteonecrosis and the extent of healing of the greater trochanter. The articulotrochanteric distance was deemed to be positive when the center of the femoral head was above the tip of the greater trochanter, zero when it was at the same level, and negative when the center of the femoral head was below the tip of the greater trochanter24.

Pincer impingement caused by acetabular overcoverage or acetabular retroversion was assessed according to the anterior and posterior wall relationships on the anteroposterior pelvic radiograph. Cam impingement caused by anterior femoral deformity was assessed on the lateral cross-table radiograph, and cam impingement caused by lateral femoral deformity was assessed on the anteroposterior pelvic radiograph.

The orientation of the acetabular walls was assessed for anteversion, retroversion, or neutral wall relationships preoperatively and postoperatively7,10,23. The presence and/or progression of osteoarthritis was graded according to the criteria of Tönnis et al.26. A preoperative magnetic resonance arthrogram was made for all patients to further characterize the source of impingement and the integrity of the acetabular labrum. Radiographic failure was defined as progression of the Tönnis grade to III, regardless of the preoperative grade.

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Operative Procedure

Surgical dislocation and débridement was performed with use of a lateral incision and a greater trochanteric flip osteotomy with the patient in the lateral position on a radiolucent table. The short external rotators including the piriformis and posterior aspect of the capsule were left intact. A z-shaped anterior capsulotomy was performed with the superior limb of the capsulotomy taken from the acetabular origin and the inferior limb taken from the femoral attachment; then, the femoral head was dislocated anteriorly19. The femoral head-neck area was assessed for ring osteophytes, reduction in femoral head-neck offset, and damage to the articular cartilage. An abnormal femoral head-neck offset was characterized by a loss of the concave transition between the normally spherical femoral articular surface and the more elliptical femoral neck. Any anterolateral chondro-osseous overgrowth was débrided with a chisel or osteotome and a high-speed rotating burr (Figs. 2-A through 2-D).

The operation consisted of a surgical dislocation and débridement in twenty-five hips and dislocation and débridement with relative femoral neck lengthening in five hips. Relative femoral neck lengthening was performed by moving the greater trochanter more distally at the time of reattachment and then débriding the residual bone from the medial aspect of the remaining greater trochanter and from the base of the femoral neck.

The acetabulum was inspected for damage to the labrum and articular cartilage. The size, character, and location of the damage to the acetabular articular cartilage was recorded and graded according to the Outerbridge system for grading chondral injury27 (see Appendix). The integrity of the acetabular labrum was assessed, and damage was classified as a labral tear, degeneration, detachment, or combinations of these lesions (see Appendix). The greater trochanter was fixed with two or three small or large-fragment screws under image intensification in all hips. An example is shown in Figs. 2-A through 2-D.

Estimated blood loss averaged 318 mL (range, 100 to 1500 mL). Patients stayed in the hospital for an average of three days (two, three, or four days). No drains were used, and dressings were removed on the second postoperative day. Anticoagulation included administration of enoxaparin and use of compression boots on an inpatient basis. Patients were given aspirin for six weeks following hospital discharge. Partial weight-bearing with two crutches was encouraged for six weeks. Then full weight-bearing was allowed, with one crutch or a cane used for six weeks or until the patient could walk without a limp.

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Statistical Methods

All collected data were analyzed with use of a commercially available software package (FileMaker Pro 7.0, Santa Clara, California, and Microsoft Excel, Redmond, Washington). The Student t test was used for comparisons, and significance was determined at alpha ≤ 0.05.

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Results

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Surgical Findings

Sixteen of the thirty hips had either a labral tear or labral degeneration (see Appendix). One hip (Case 30; see Appendix) had no identifiable labrum because of a prior arthroscopic débridement. Seven hips underwent a partial labral excision and débridement. Five hips underwent repair of the labrum by partial detachment, débridement, and reattachment with sutures to the acetabular rim. In four hips, the damaged labrum was left untreated.

In twenty-six hips, damage to the acetabular labrum or underlying articular cartilage was located in the anterior-superior quadrant of the acetabulum at the region of abutment of the femoral head-neck junction against the acetabulum, on the articular side. No acetabular damage was seen in four hips. Eighteen hips had severe (Outerbridge grade-IV) delamination of the acetabular articular cartilage, two hips had Outerbridge grade-III chondral damage, and ten hips had less severe (Outerbridge grade-0, I, or II) chondral damage.

Specific treatment of damaged acetabular articular cartilage varied over the course of the study period. Of the twenty hips with Outerbridge grade-III or IV cartilage delamination, ten underwent resection of the delaminated articular cartilage and either microfracture of the acetabular subchondral bone (three hips) or no specific osseous treatment (Fig. 3). Four acetabula underwent resection of the delaminated cartilage and the underlying subchondral bone with advancement of the labrum to a newly created anterolateral aspect of the acetabular rim. Osteochondroplasty of the femoral head-neck junction to improve femoral head-neck offset was performed in all thirty hips.

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Clinical Results

The average Harris hip score improved from a preoperative value of 70 points (range, 20 to 81 points) to 88 points (range, 49 to 100 points) at one year (p < 0.0001) and 87 points (range, 49 to 100 points) at the time of final follow-up (p < 0.0001).

Four (13%) of the thirty hips, all in female patients, were considered failures because of pain and/or progressive arthrosis. Three of these hips (Cases 2, 6, and 26; see Appendix) were converted to a total hip arthroplasty because of the clinical failure; two were converted at three months and one, at three years postoperatively. None of these patients had undergone a previous hip procedure. At the time of the arthrotomy, all three were found to have severe delamination of the acetabular articular cartilage (Outerbridge grade IV). The fourth hip with a failure (Case 10) had radiographic signs of progressive arthrosis. The patient also had progressive pain and was expected to probably require a total hip arthroplasty in the future.

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Radiographic Results

Preoperative Assessment

Ten acetabula were anteverted, fifteen were retroverted, and five had neutral wall relationships. The average center-edge angle was 28° (range, 8° to 50°), and it was >15° in twenty-eight of the thirty hips. The articulotrochanteric distance was positive in eleven hips, zero in thirteen hips, and negative in six hips. An os acetabuli was seen on the radiographs of four hips, two in which the acetabulum was anteverted, one in which it was neutral, and one in which it was retroverted). The Tönnis grade of osteoarthritis was grade 0 in sixteen hips, grade I in twelve hips, grade II in two hips, and grade III in no hips.

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Final Follow-up Assessment

There was complete osseous union of the greater trochanter in twenty-two of the thirty hips and an incomplete osseous union in eight hips with no failure of trochanteric screws. No hip had osteonecrosis of the femoral head postoperatively. The articulotrochanteric distance was positive in eighteen hips, zero in twelve hips, and negative in no hips. Thus, the articulotrochanteric distance improved in thirteen hips, remained the same in sixteen hips, and worsened in one hip. The Tönnis osteoarthritis grade was 0 in ten hips, I in fifteen hips, II in three hips, and III in two hips. The osteoarthritis grade did not progress in twenty of the thirty hips. There was one Tönnis grade of progression in nine hips and two Tönnis grades of progression in one hip. Eight of the ten patients with radiographic evidence of progression of osteoarthritis had severe delaminations of the acetabular articular cartilage (Outerbridge grade IV) found at the arthrotomy.

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Discussion

The surgical treatment of the cam-type of femoro-acetabular impingement is directed at restoring a normal femoral head-neck offset by débriding impinging chondro-osseous tissue at the femoral head-neck junction and débriding or attempting to repair a diseased acetabular labrum and acetabular articular cartilage. The acetabular, or pincer, type of impingement can be addressed with an acetabular redirectional osteotomy and trimming of the femoral head-neck area.

The technique of safe surgical dislocation developed by Ganz et al.19 preserves the femoral head blood supply and allows direct visualization of the intra-articular lesion. The technique can be combined with other procedures such as trochanteric advancement, relative femoral neck lengthening, and even femoral neck osteotomy19. The originators of the technique reported preliminary results in nineteen patients with femoroacetabular impingement who had been followed for a mean of 4.2 years1. Five of the nineteen patients went on to have a total hip arthroplasty at an average of 3.1 years postoperatively. Failure was correlated with the damage to the acetabular articular cartilage noted at the time of the surgical dislocation.

Murphy et al. reported their experience with hip débridement in the treatment of femoro-acetabular impingement in twenty-three patients (average age, thirty-five years) who were followed for two to twelve years22. Many of the patients in that series were evaluated and treated prior to our current understanding of femoro-acetabular impingement and with techniques that are considered suboptimal today. For example, magnetic resonance imaging was not utilized preoperatively and the surgical exposure was a direct lateral approach in fourteen of the twenty-three hips, with only six hips treated with the trochanteric slide osteotomy and the surgical dislocation technique described by Ganz et al.19. Seven of the twenty-three patients subsequently required total hip arthroplasty: three required it “early” (no time specified) and four, between six and nine years postoperatively. No mention was made of radiographic signs of progression of osteoarthritis in the surviving hips, and no assessment of the extent of acetabular chondral injury was included. The authors concluded that hips with the greatest risk of failure were those with advanced arthrosis or a combination of impingement and instability.

Our results confirm that surgical dislocation by means of a trochanteric flip osteotomy and anterior dislocation of the femoral head is a safe technique that does not appear to jeopardize the vascularity of the femoral head, as we observed no cases of osteonecrosis postoperatively.

Four of thirty hips were considered failures because they required or were expected to require a total hip arthroplasty less than thirty-six months postoperatively. All of the failed hips had severe damage to the acetabular hyaline cartilage on surgical inspection. A retrospective analysis of these patients' preoperative plain radiographs and magnetic resonance imaging studies revealed evidence, albeit subtle, of acetabular arthritic involvement either in the form of acetabular cyst formation or a narrowed joint space.

Radiographic signs of progression of osteoarthritis were seen in ten of the thirty hips. Nine of these hips had one grade of progression and one hip, which was considered a failure radiographically, had two grades of progression. Interestingly, six of the ten hips with radiographic evidence of progression of osteoarthritis continued to function well, with an improved Harris hip score, at the time of final follow-up.

Eight of these ten hips and all four failures in our series had severe damage to the acetabular articular cartilage that was noted intraoperatively but not appreciated on preoperative studies. The area of chondral damage was located in the anterior-superior aspect of the acetabulum, at the site of impingement when the hip was flexed and internally rotated1. These findings suggest that arthroscopic or open procedures focusing on treatment of the labrum alone may be insufficient, as they do not address the more important lesion involving the underlying acetabular articular cartilage. We agree with Ganz et al.2 that chondral injury subjacent to the labrum is the primary injury and that labral damage occurs secondarily. We further believe that the prognosis for hips with femoroacetabular impingement depends on the state of the acetabular articular cartilage.

Our results support the concept that patients with minimal damage to the articular cartilage (Outerbridge grade 0, I, or II) can be treated effectively with this technique. Preoperative assessment of the integrity of the acetabular articular cartilage with use of magnetic resonance arthrography or magnetic resonance imaging alone is therefore essential3. In our experience, even with magnetic resonance arthrography, the extent of damage to the acetabular articular cartilage is often underestimated, a finding that emphasizes the need for improved cartilage imaging techniques.

The optimum treatment of severe acetabular chondral injury (Outerbridge grade III or IV) is unknown. We have performed a variety of treatments on the acetabulum: excision of damaged articular cartilage together with a portion of the underlying acetabular rim and labral advancement, débridement alone, and cartilage débridement with microfracture of subchondral bone. We cannot conclude that any of these methods is superior to another. At present, it is our practice to perform excision of the delaminated articular cartilage with the underlying bone followed by labral advancement to the newly created anterior aspect of the acetabular rim as we believe that this approach may provide the best outcome for these patients. The major caveat with this approach, however, is that resection of the underlying anterolateral acetabular bone may create the equivalent of a dysplastic acetabulum, which may require a subsequent reorientation acetabular osteotomy.

We believe that the major challenge and current limitation of the treatment of femoro-acetabular impingement remains the lack of a cartilage imaging technique that allows accurate assessment of the damage to the articular cartilage so that timely treatment can be performed before there is progression to advanced stages of arthrosis.

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Appendix

Tables listing the previous operations in six patients, describing the Outerbridge classification, and presenting detailed information on all thirty patients are available with the electronic versions of this article, on our web site at jbjs.org (go to the article citation and click on “Supplementary Material”) and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM). ▪

A video supplement to this article will be available from the Video Journal of Orthopaedics. A video clip will be available at the JBJS web site, . The Video Journal of Orthopaedics can be contacted at (805) 962-3410, web site: .

A commentary is available with the electronic versions of this article, on our web site () and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM).

NOTE: The authors express their gratitude to Jeff Mast, MD, for his teaching and guidance in the diagnosis and treatment of patients with femoro-acetabular impingement and hip dysplasia. They also thank Jerod Hines for his contribution of database management.

The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Investigation performed at the Department of Orthopaedics, University of Utah, Salt Lake City, Utah

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