Preoperative and more-than-five-year postoperative radiographs were available for review for ninety-seven (95%) of the 102 preserved hips (Table II). Seventy-nine hips (81%) had had grade-0 or 1 signs of osteoarthritis before surgery, and eighteen (19%) had had grade-2 or 3 signs of osteoarthritis before surgery. In comparison, seventy-one hips (70%) had grade-0 to 1 changes at the time of the most recent follow-up visit. Twenty-four hips (24%) had progression in terms of the osteoarthritis grade (with eighteen hips advancing from grade 0 to grade 1). Eleven hips (11%) demonstrated radiographic regression of osteoarthritis by at least one grade.
Two hips had a postoperative crossover sign. As stated, the criteria for correct positioning of the pelvis were not in place during the study period and it is therefore difficult to accurately judge the importance of this finding. One hip lacked a follow-up false-profile radiograph to assess anterior coverage, and the other hip had an anterior center-edge angle of 40°, which may explain the appearance of this crossover sign. Both hips had a negative Tönnis angle, indicating lateral overcoverage as well. However, at an average of ten years after surgery, both patients rated the pain in that hip as 0 (no pain).
Within this group of preserved hips, fifty-seven hips (59%) had had a preoperative minimum joint space of <2 mm, a Tönnis grade of 2 or 3, and/or poor or fair congruency. The average postoperative pain score for these hips was 2.2 at an average of nine years after the periacetabular osteotomy.
Outcomes for Hips with Failure of Periacetabular Osteotomy
Thirty-three hips (24%) had a failure according to the combined criteria. The average age of the patients in this group was 31.3 ± 8.8 years. Demographic and radiographic data are presented in Table I.
Preoperative and more-than-five-year postoperative radiographs were available for review for thirty-one (94%) of the thirty-three hips that had a failure (Table II). Seventeen hips (55%) had had grade-0 or 1 signs of osteoarthritis before surgery, and fourteen (45%) had had grade-2 or 3 signs of osteoarthritis before surgery. In comparison, twelve hips (39%) had grade-0 or 1 changes at the time of the most recent follow-up visit. Thirteen hips (42%) had progression of the osteoarthritis grade (with ten hips advancing from grade 0 to grade 1). Five hips (16%) demonstrated radiographic regression of the osteoarthritis by one grade.
Seven hips (21%) had diagnosis and treatment of a labral tear at the time of the osteotomy. No hip had a crossover sign postoperatively. Two hips had a break in the Shenton line. In both cases, the Tönnis angle was <10°. The lateral and anterior center-edge angles in those two hips were 25° to 28°, with no radiographic signs of subluxation.
Within this group of hips that had a failure, we also found that thirteen hips (42%) had had good or excellent joint congruency, seventeen (55%) had had a Tönnis osteoarthritis grade of 0 or 1, and twenty-seven (87%) had had ≥2 mm of joint space preoperatively.
As previous studies had evaluated conversion to total hip arthroplasty as the primary mode of osteotomy failure, we assessed the seventeen hips that fell into this category. The average age in this group was 34.4 ± 6.3 years. Kaplan-Meier analysis with arthroplasty as the end point revealed an estimated survival rate of 96% (95% confidence interval, 93% to 99%) at five years and 84% (95% confidence interval, 77% to 90%) at ten years (Fig. 3).
An average WOMAC pain score of 10 indicated moderate pain and discomfort and was set as a marker for failure. At the time of the most recent review, sixteen hips had a pain score of ≥10 (Fig. 2). The average age at the time of surgery for this group was 27.7 ± 9.5 years. The Kaplan-Meier estimated survival rate with failure due to a pain score of ≥10 as the end point could not be accurately calculated as we did not have serial evaluations to determine the exact time to this type of failure.
Predictors of Osteotomy Failure
Univariate and multivariate analyses were performed to determine predictors of periacetabular osteotomy failure. Preserved and failed hips were found to be similar with regard to patient sex, the side of surgery, and the amount of dysplasia (based on the center-edge and Tönnis angles) (Table I). We did not find that the presence of a labral tear predicted failure as has been noted by other authors8,11. Univariate predictors for failure included an age of more than thirty-five years at the time of surgery, <2 mm of joint space, preoperative poor or fair joint congruency indicating a mismatch in the radii of curvature with at least partial loss of joint space, and a higher Tönnis osteoarthritis grade. However, only an age of more than thirty-five years and preoperative poor or fair congruency were found to be independently predictive of failure on multivariate analysis. A simplified probability-of-failure table (Table III) was constructed to estimate the probability of failure of the osteotomy because of either a higher pain score (≥10) or total hip arthroplasty on the basis of the number of independent preoperative predictors. This table can be summarized as follows: the probability of failure of the osteotomy, defined as an arthroplasty (at an average of six years) or moderate or worse pain (at an average of nine years), was 14% if no predictors were present, 36% if one predictor was present, and 95% if both predictors were present. The relationship of these predictors was examined with receiver operating characteristic analysis. The area under this curve was 0.80, indicating good to excellent diagnostic performance of these two predictors.
Additional Intertrochanteric Osteotomy
A simultaneous intertrochanteric osteotomy was performed in twenty-five (19%) of the 135 hips following periacetabular osteotomy. Twenty-three varus derotational osteotomies were performed for the treatment of coxa valga (two with shortening), and two valgus-producing osteotomies were performed for the treatment of mild coxa vara to improve joint congruency. These procedures were evenly spread throughout this initial experience. No complications were associated with the performance of the femoral osteotomy or with the implants. There were no clinical or radiographic predictors of the need for an additional intertrochanteric osteotomy.
Arthroscopy Following Osteotomy
Fifteen hips (11%) underwent arthroscopic débridement of either painful labral or chondral lesions at an average of 6.8 ± 2.9 years following the periacetabular osteotomy. All but one hip had had an arthrotomy at the time of the osteotomy, and three had had a full-thickness labral tear that was débrided to a stable margin. The preoperative evaluation demonstrated an average Tönnis score of 0.3, an average joint space width of 3.9 mm, and good to excellent congruency on the average. No patient had a magnetic resonance imaging before the osteotomy.
Postoperative radiographic evaluation demonstrated no radiographic predictors of later surgery. One hip had an anterior center-edge angle of 41°. However, the remainder of the hips in this group had average anterior and lateral center-edge angles of 28.5° ± 9.4° and 28.5° ± 8.6°, respectively. All patients presented with mechanical symptoms of locking and/or catching and had pain with flexion, adduction, and internal rotation of the hip. Pre-arthroscopy magnetic resonance imaging was performed for all hips, and either direct or indirect arthrography was performed for five.
Magnetic resonance imaging accurately predicted the arthroscopic findings for both labral and articular cartilage lesions in four hips. In the remaining eleven hips, discrepancies were found between the imaging findings and the arthroscopic assessment of the articular cartilage. At the time of arthroscopy, thirteen hips had at least partial-thickness loss of femoral weight-bearing cartilage and, of these, four had a full-thickness cartilage defect. Two hips had intact acetabular articular cartilage, and the remaining thirteen had at least partial loss of cartilage, primarily in the weight-bearing zone. Three hips had full-thickness cartilage loss, two at the anterior acetabular rim and one more medially in the weight-bearing zone opposite a chondral lesion of the femoral head. All had a labral tear that was débrided back to a stable margin.
Four hips had a pain score of ≥10. One of those hips was treated with arthroplasty within two years. The other three hips had an average post-arthroscopy pain score of 12. For the remaining hips that underwent arthroscopy, the average post-arthroscopy pain score was 1.7. We could find no preoperative clinical or radiographic predictors of subsequent cartilage pathology requiring arthroscopic débridement.
Patients Lost to Follow-up
Twenty-three hips in twenty-two patients were not found for evaluation. Radiographs of fifteen of these hips were available for review. No pain scores were obtained for this group. The average age for this group (27.1 years) was similar to that for the study group. The preoperative and one-year postoperative radiographic results that were available for these hips did not differ from those for hips that had more than five years of follow-up. None of the fifteen hips that had one year of follow-up had gone on to arthroplasty at the time of that evaluation.
Twenty patients (twenty hips) experienced complications related to the periacetabular osteotomy that were evaluated during the first year after surgery. The most common complication was a transient peroneal nerve palsy (nine hips; 6.7%), followed by a wound hematoma requiring surgical drainage (six hips; 4.4%). Of the wound hematomas, two demonstrated growth of organisms on culture and were subsequently reclassified as infections and were treated with appropriate antibiotics until resolution. Two patients (two hips) had an asymptomatic nonunion of the superior pubic ramus osteotomy site. Two hips had development of Brooker class-3 heterotopic ossification26. One patient presented with an intrapelvic abscess two months after surgery and was managed with surgical drainage.
The present report on 135 hips with varying degrees of developmental dysplasia describes the early experience and initial learning curve of a single surgeon with the use of the Bernese periacetabular osteotomy at our institution. Seventy-six percent of the hips remained preserved with little or no pain at an average of nine years after the osteotomy, and 24% of the hips had a failure according to our criteria.
Previous reports on the intermediate and long-term results of reorienting acetabular osteotomies for the treatment of hip dysplasia have shown good to excellent survival rates and improvement in clinical outcomes. Van Hellemondt et al. reported that 88% of fifty-one triple pelvic osteotomies were preserved at an average of fifteen years, with improvement of the Merle d'Aubigné and Postel clinical score from 12.9 preoperatively to 13.3 postoperatively15. Trousdale et al., in a report on the intermediate-term results of periacetabular osteotomy in forty-two patients who had an average duration of follow-up of four years, noted that the Harris hip score improved from 62 preoperatively to 86 postoperatively9. Siebenrock et al. reported that 82% of seventy-one hips were preserved at an average of 11.3 years after a Bernese periacetabular osteotomy, with significant improvement in the Merle d'Aubigné and Postel clinical score from 14.6 preoperatively to 16.3 postoperatively8. They also noted several prognostic factors that were independently associated with a negative outcome following the periacetabular osteotomy. Significant variables included an older age at the time of surgery, the presence and grade of arthritis, the presence of a labral lesion, and failure to attain complete coverage of the femoral head. Poorer outcomes included conversion to total hip arthroplasty (twelve of seventy-one hips), conversion to arthrodesis (one hip), and a “fair” Merle d'Aubigné and Postel rating (six of fifty-eight preserved hips). More recently, this same group of patients was reviewed at a minimum of nineteen years after osteotomy27. Once again, predictors of poor outcome included an older age (more than thirty years) at the time of surgery, worse preoperative arthritis, and the presence of a preoperative limp or a positive anterior impingement test.
While all of those studies demonstrated improved average pain and function scores in association with periacetabular osteotomy, each study included patients who experienced substantial pain in the hip and/or loss of function postoperatively. Siebenrock et al. reported “fair” clinical results in 10% of hips8. Similarly, in the present study, sixteen hips (12%) had pain that was rated as ≥10 (moderate to extreme) on this scale.
We considered this amount of postoperative pain to be a clinical failure. These hips were then combined with the seventeen hips that underwent conversion to arthroplasty in an effort to describe what we believe to be a more accurate representation of periacetabular osteotomy failure. Univariate and multivariate analyses involving this combined criterion of higher postoperative pain or conversion to arthroplasty demonstrated that an age of more than thirty-five years at the time of surgery and preoperative poor or fair joint congruency were independently predictive of periacetabular osteotomy failure. To further aid in assessing the risk of failure, we constructed a simplified analysis for the probability of failure (Table III), which demonstrated good to excellent diagnostic performance in predicting failure after osteotomy. This prediction rule based on independent multivariate predictors may be a useful guide to the surgeon and the patient for decision-making when considering periacetabular osteotomy as a joint-preserving procedure.
Labral symptoms requiring operative treatment occur in some hips following otherwise successful acetabular realignment surgery. Our analysis did not demonstrate that the presence of a labral tear at the time of osteotomy was an independent predictor of failure, nor did it predict which hips would later have development of a torn labrum. Arthrotomy was not routinely performed early in this series, and it was performed in only eighty-two (61%) of the 135 reviewed hips. This may account for our inability to document a preoperative labral tear as a predictor of poor outcome. The contribution of acetabular retroversion to hip arthritis has been described18. A lack of standardized radiographs during the study period prevented us from making a definitive statement regarding retroversion and its potential contribution to outcomes in the present study.
In the present study, fifteen (11%) of the 135 hips later underwent arthroscopic débridement of torn labral or articular cartilage. Four of these hips had a postoperative pain score of ≥10, one of which underwent arthroplasty two years after arthroscopy. The remaining eleven hips regained nearly pain-free states, with an average pain score of 1.7. We identified no preoperative variable to predict which hips were at risk for the development of a painful labral or articular lesion following osteotomy. Preoperative magnetic resonance imaging was not performed in this patient cohort. However, magnetic resonance imaging has proved to be more effective than plain radiography for assessing the health of cartilage before surgery and for predicting which joints will still be painful postoperatively28.
Despite the association of arthritis with osteotomy failure, in many hips the preoperative assessment did not correlate with the postoperative outcome. Nine (53%) of the seventeen hips that underwent arthroplasty and eight (50%) of the sixteen hips that had a pain score of ≥10 had had little or no preoperative radiographic evidence of arthritis (Tönnis grade 0 to 1). Conversely, eighteen (19%) of the ninety-seven preserved hips with radiographs available for review had had obvious preoperative radiographic signs of arthritis (Tönnis grade 2 to 3). Eleven (11%) of these ninety-seven preserved hips demonstrated improvement in the Tönnis grade. These interesting and somewhat counterintuitive results emphasize the shortcomings of plain radiography and of this grading system in assessing and predicting the response of articular cartilage in dysplastic hips to joint-preserving surgery. Currently, we are employing the delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) technique preoperatively and postoperatively to assess the health of articular cartilage over time28.
While we found no significant difference between the preserved and failed hips with regard to preoperative or postoperative radiographic measurements of dysplasia (the center-edge and Tönnis angles), we believe that the final positioning of the acetabular fragment is a critical step in periacetabular osteotomy. Undercorrection or overcorrection leads to overloading of the acetabular rim, with negative consequences29-31. Given that the preserved and failed hips were equally corrected, additional factors must also be important in determining the outcome following this osteotomy.
The present study demonstrated a 15% complication rate, with transient nerve palsy being the most frequent complication. Trousdale et al. described a 45% complication rate in their first forty-two hips that were treated with periacetabular osteotomy9. In a follow-up study of seventy-five hips undergoing periacetabular osteotomy, Siebenrock et al. noted a lower complication rate of 20%8. Subsequently, Trousdale and Cabanela reported a complication rate of 11% in a study of 250 periacetabular osteotomies, with neurapraxia of the lateral femoral cutaneous nerve being common32. Nerve palsy following the pelvic osteotomy has been reported previously7-9,15,33. The most common complication in the present study was peroneal nerve palsy (6.7%). This finding is consistent with previously published electromyographic data acquired by Pring et al. during periacetabular osteotomy33. In the present study, all nine patients (nine hips) with this complication had recovered full nerve function by one year. While previous reports seem to demonstrate a general decrease in complication rates with increasing experience, there remains a relatively high risk of complications in association with this procedure, with the majority of complications being transient.
The limitations of the present study included the lack of comparative preoperative and postoperative pain assessment; the lack of scoring of hip function; the lack of a similar control group; the moderate kappa values for the Yasunaga system for the classification of congruency; and the incompletely characterized natural history of developmental hip dysplasia. In addition, as is common to retrospective studies, our inability to locate and/or completely review all patients and their radiographs may have confounded our results, including the overall osteotomy survival rate.
In summary, our analysis of periacetabular osteotomy for the treatment of painful dysplasia in 135 hips with a mean duration of follow-up of nine years demonstrated that 76% of the hips were still preserved and had little or no pain. While radiographic correction of dysplasia is possible with the Bernese periacetabular osteotomy, the amount of intra-articular pathology at the time of surgery is often difficult to accurately assess preoperatively. As with other initial series, there was a substantial rate of complications (15%) in this early experience, with the majority of complications being transient. We were unable to find predictors of the need for subsequent surgery. However, we identified two independent predictors of failure resulting in a high pain score or total hip arthroplasty: an age of more than thirty-five years and poor or fair joint-space congruency. Validation of our prediction model and advances in imaging modalities will likely improve patient selection and decrease the rate of failure. Additional improvement in outcomes is expected as a result of refinements in surgical technique that have been incorporated since the beginning of the experience reported here, including improved assessment of intra-articular pathology and optimization of acetabular fragment placement.
NOTE: The authors thank Reinhold Ganz, Robert Poss, and Heinz Wagner.
Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received 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, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.
A commentary is available with the electronic versions of this article, on our web site (www.jbjs.org) and on our quarterly CD-ROM/DVD (call our subscription department, at 781-449-9780, to order the CD-ROM or DVD).
Investigation performed at the Department of Orthopaedic Surgery, Children's Hospital Boston, Boston, Massachusetts
1. Aronson J. Osteoarthritis of the young adult hip: etiology and treatment. Instr Course Lect. 1986;35:119-28.
2. Harris WH. Etiology of osteoarthritis of the hip. Clin Orthop Relat Res. 1986;213:20-33.
3. Murray RO. The aetiology of primary osteoarthritis of the hip. Br J Radiol. 1965;38:810-24.
4. Tönnis D. Congenital dysplasia and dislocation of the hip in children and adults. New York: Springer; 1987. p 156-61.
5. Tönnis D, Heinecke A. Acetabular and femoral anteversion: relationship with osteoarthritis of the hip. J Bone Joint Surg Am. 1999;81:1747-70.
6. Wiberg G. Studies on dysplastic acetabula and congenital subluxation of the hip joint. With special reference to the complications of osteoarthritis. Acta Chir Scand. 1939;58(Suppl):5-135.
7. Nakamura S, Ninomiya S, Takatori Y, Morimoto S, Umeyama T. Long-term outcome of rotational acetabular osteotomy: 145 hips followed for 10-23 years. Acta Orthop Scand. 1998;69:259-65.
8. Siebenrock KA, Leunig M, Ganz R. Periacetabular osteotomy: the Bernese experience. Instr Course Lect. 2001;50:239-45.
9. Trousdale RT, Ekkernkamp A, Ganz R, Wallrichs SL. Periacetabular and intertrochanteric osteotomy for the treatment of osteoarthrosis in dysplastic hips. J Bone Joint Surg Am. 1995;77:73-85.
10. Murphy S, Deshmukh R. Periacetabular osteotomy: preoperative radiographic predictors of outcome. Clin Orthop Relat Res. 2002;405:168-74.
11. Yasunaga Y, Ochi M, Terayama H, Tanaka R, Yamasaki T, Ishii Y. Rotational acetabular osteotomy for advanced osteoarthritis secondary to dysplasia of the hip. J Bone Joint Surg Am. 2006;88:1915-9.
12. Clohisy JC, Barrett SE, Gordon JE, Delgado ED, Schoenecker PL. Periacetabular osteotomy in the treatment of severe acetabular dysplasia. Surgical technique. J Bone Joint Surg Am. 2006;88 Suppl 1(Pt 1):65-83.
13. Peters CL, Erickson JA, Hines JL. Early results of the Bernese periacetabular osteotomy: the learning curve at an academic medical center. J Bone Joint Surg Am. 2006;88:1920-6.
14. Tönnis D, Arning A, Bloch M, Heinecke A, Kalchschmidt K. Triple pelvic osteotomy. J Pediatr Orthop B. 1994;3:54-67.
15. Van Hellemondt GG, Sonneveld H, Schreuder MH, Kooijman MA, de Kleuver M. Triple osteotomy of the pelvis for acetabular dysplasia: results at a mean follow-up of 15 years. J Bone Joint Surg Br. 2005;87:911-5.
16. Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW. Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip and knee. J Rheumatol. 1988;15:1833-40.
17. Lequesne M, de Sèze. [False profile of the pelvis. A new radiographic incidence for the study of the hip. Its use in dysplasias and different coxopathies]. Rev Rhum Mal Osteoartic. 1961;28:643-52. French.
18. Reynolds D, Lucas J, Klaue K. Retroversion of the acetabulum. A cause of hip pain. J Bone Joint Surg Br. 1999;81:281-8.
19. Siebenrock KA, Kalbermatten DF, Ganz R. Effect of pelvic tilt on acetabular retroversion: a study of pelves from cadavers. Clin Orthop Relat Res. 2003;407:241-8.
20. Ganz R, Klaue K, Vinh TS, Mast JW. A new periacetabular osteotomy for the treatment of hip dysplasias. Technique and preliminary results. Clin Orthop Relat Res. 1988;232:26-36.
21. Murphy SB, Millis MB. Periacetabular osteotomy without abductor dissection using direct anterior exposure. Clin Orthop Relat Res. 1999;364:92-8.
22. Harris EK, Albert A. Survivorship analysis for clinical studies. New York: Dekker; 1991. p 29-49.
23. Hosmer DW, Lemeshow S. Applied logistic regression. 2nd ed. New York: Wiley; 2000. p 91-142.
24. Katz MH. Multivariable analysis: a practical guide for clinicians. 2nd ed. New York: Cambridge University Press; 2006. p 137-52.
25. Obuchowski NA. Receiver operating characteristic curves and their use in radiology. Radiology. 2003;229:3-8.
26. Brooker AF, Robinson RA, Riley LH. Ectopic ossification following total hip replacement. Incidence and a method of classification. J Bone Joint Surg Am. 1973;55:1629-32.
27. Steppacher SD, Tannast M, Ganz R, Siebenrock KA. Mean 20-year followup of Bernese periacetabular osteotomy. Clin Orthop Relat Res. 2008;466:1633-44.
28. Kim YJ, Jaramillo D, Millis MB, Gray ML, Burstein D. Assessment of early osteoarthritis in hip dysplasia with delayed gadolinium-enhanced magnetic resonance imaging of cartilage. J Bone Joint Surg Am. 2003;85:1987-92.
29. Klaue K, Durnin CW, Ganz R. The acetabular rim syndrome. A clinical presentation of dysplasia of the hip. J Bone Joint Surg Br. 1991;73:423-9.
30. Wenger DE, Kendell KR, Miner MR, Trousdale RT. Acetabular labral tears rarely occur in the absence of bony abnormalities. Clin Orthop Relat Res. 2004;426:145-50.
31. Myers SR, Eijer H, Ganz R. Anterior femoroacetabular impingement after periacetabular osteotomy. Clin Orthop Relat Res. 1999;363:93-9.
32. Trousdale RT, Cabanela ME. Lessons learned after more than 250 periacetabular osteotomies. Acta Orthop Scand. 2003;74:119-26.
Copyright 2009 by The Journal of Bone and Joint Surgery, Incorporated
33. Pring ME, Trousdale RT, Cabanela ME, Harper CM. Intraoperative electromyographic monitoring during periacetabular osteotomy. Clin Orthop Relat Res. 2002;400:158-64.