Peters, Christopher L.

Background: Periacetabular osteotomy (PAO) remains the gold-standard treatment for acetabular dysplasia in skeletally mature patients with preserved cartilage. The purpose of this multicenter cohort study was to delineate the long-term radiographic natural history of the dysplastic hip following PAO based on the final position of the acetabular fragment. Methods: We evaluated patients who underwent PAO performed by 4 hip preservation surgeons to treat acetabular dysplasia with or without concomitant retroversion from 1996 to 2012 at 3 academic institutions. There were 288 patients with a mean clinical and radiographic follow-up of 9 years (range, 5 to 21 years). Postoperative radiographs made at the first clinical visit were used to determine if the acetabular fragment fell into a safe zone according to the absence of retroversion, a lateral center-edge angle (LCEA) of 25° to 40°, an anterior center-edge angle (ACEA) of 25° to 40°, and a Tönnis angle of 0° to 10°. Every available subsequent radiograph was assessed for degenerative changes by the Tönnis classification (grades 0 to 3). The time to progression was analyzed using Cox proportional hazards regression and multistate modeling. Results: Only the absence of retroversion was independently associated with a decreased risk of progressing at least 1 Tönnis grade during follow-up: hazard ratio (HR), 0.60 (95% confidence interval [CI], 0.38 to 0.94; p = 0.025). Achieving the ACEA safe zone yielded the greatest time increase for remaining in Tönnis grade 0 or 1 (43 years for having an ACEA in the safe zone compared with 28 years for not having an ACEA in the safe zone), followed by the absence of retroversion (34 years for the absence of retroversion compared with 24 years for the presence of retroversion). However, attaining the Tönnis angle or LCEA safe zones did not delay progression. The achievement of additional safe zones generally increased the length of time that patients spent in Tönnis grade 0 or 1: 25 years for 0 safe zones, 36 years for 1 safe zone, 29 years for 2 safe zones, 37 years for 3 safe zones, and 44 years for 4 safe zones. Conclusions: This study demonstrates the importance of achieving appropriate acetabular reorientation to enhance the longevity of the native hip following PAO. Although the LCEA and the Tönnis angle are the most common metrics used to assess appropriate acetabular correction, this study shows that adequately addressing retroversion and the ACEA has a greater impact on improving the natural history. Level of Evidence: Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Background: Periacetabular osteotomy (PAO) is the most common treatment for symptomatic acetabular dysplasia, or developmental dysplasia of the hip (DDH), in skeletally mature patients. The purpose of this multicenter cohort study was to delineate the long-term radiographic natural history of the dysplastic hip following PAO. Methods: We evaluated all patients undergoing PAO from 1996 to 2012 at 3 academic institutions in the United States. Inclusion criteria were PAO for DDH with a minimum 5-year radiographic follow-up. Exclusion criteria were PAO for isolated acetabular retroversion, neurogenic dysplasia, Legg-Calvé-Perthes disease, and prior hip surgery including osteotomies and arthroscopy. There were 288 patients, 83% of whom were women; the mean age and body mass index (BMI) were 29 years and 25 kg/m 2 , respectively. The mean clinical and radiographic follow-up was 9.2 years (range, 5.0 to 21.1 years). Every preoperative and postoperative hip radiograph was assessed to determine the degree of osteoarthritis according to the Tönnis classification. Survivorship was analyzed by multistate modeling, enabling assessment of progression through the Tönnis grades rather than just individual transitions as with Kaplan-Meier techniques. Results: At the time of final follow-up, 144 patients (50%) had progressed at least 1 Tönnis grade, with 42 patients (14.6%) undergoing total hip arthroplasty. The mean number of years spent in each Tönnis grade following PAO was 19 for Tönnis grade 1, 8 for Tönnis grade 2, and 4 for Tönnis grade 3. The probability of progression to total hip arthroplasty increased significantly on the basis of a higher initial Tönnis grade (p < 0.001). The most marked difference occurred between Tönnis grade 0 or 1 and Tönnis grade 2; for Tönnis grade 1, the probability of progression to total hip arthroplasty at 5 and 10 years was 2% and 11%, respectively, compared with 23% and 53%, respectively, for Tönnis grade 2. Conclusions: PAO effectively alters the natural history of DDH. Precise radiographic progression based on the Tönnis grade can now be used to ascribe prognosis for the native hip. Importantly, this investigation demonstrates a stark increase in progression to total hip arthroplasty within 10 years of PAO for patients with preoperative Tönnis grade-2 osteoarthritis compared with those with Tönnis grade-0 or 1 osteoarthritis. Level of Evidence: Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Background: There is a paucity of data on the results of reverse (anteverting) periacetabular osteotomy (RPAO) for treatment of femoroacetabular impingement (FAI) secondary to acetabular retroversion. Purpose: To evaluate the midterm outcomes of RPAO for FAI secondary to acetabular retroversion in those with and without hip dysplasia. Study Design: Cohort study; Level of evidence, 3. Methods: A retrospective review identified RPAOs performed on patients with acetabular retroversion in isolation or in the setting of dysplasia (lateral center-edge angle [LCEA] ≤19°). Acetabular retroversion with FAI was diagnosed clinically and radiographically, with a positive crossover and posterior wall signs on pelvic radiographs. Twenty-three patients (30 hips) met the inclusion criteria; 20 hips with isolated retroversion and 10 hips with retroversion and hip dysplasia. The average age at the time of the procedure was 26 years (range, 13-45 years). The average length of follow-up was 5 years (range, 2-19 years). Harris Hip Score (HHS) and radiographs were evaluated preoperatively and at last follow-up. Results: The mean preoperative LCEA was 31° (range, 22°-49°) in the isolated retroversion group and 9° (range, –4° to 17°) in the dysplastic group. Postoperatively, the LCEA in the dysplastic group increased to 35° (range, 15°-46°) ( P = .0001). The crossover sign corrected in 55% (11/20) of the isolated retroversion group and 80% (8/10) of the dysplastic group. The acetabular index (mean ± SD) improved from 1.3 ± 0.3 to 1.7 ± 0.6 ( P = .0001), indicating improved anteversion. At the latest follow-up, the average HHS in the isolated retroversion group increased from 58 preoperatively (range, 23-77) to 93 (range, 68-100) ( P = .0001); the HHS in the dysplastic group improved from 49 (range, 20-74) to 92 (range, 77-100) ( P < .0001). Complication rates were similar in both groups. Excluding hardware removal, additional surgeries were performed in 13% (4/30). Conclusion: RPAO performed for FAI in the young patient with isolated acetabular retroversion or retroversion in the setting of dysplasia successfully improved clinical and radiographic results at mid- to long-term follow-up.

Background: The morphologic characteristics of the labrum in patients with symptomatic acetabular dysplasia have been described to some extent in smaller retrospective series, but the need remains to further define these disease characteristics and their importance as a diagnostic feature of hip instability. Purpose: To (1) characterize the morphologic characteristics of the labrum in patients with symptomatic acetabular dysplasia and (2) test the relationships between specific labral variants, severity of dysplasia, and duration of symptoms. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Thirteen surgeons from 10 centers enrolled patients undergoing periacetabular osteotomy (PAO) for symptomatic acetabular dysplasia from 2008 to 2014. Patient demographics, presenting characteristics, preoperative radiographic data, operative data, and intraoperative findings were prospectively collected and retrospectively reviewed. Results: A total of 942 patients (972 hips) met the initial inclusion criteria, with a mean age of 25.2 years (range, 9-51 years; 84% female, 16% male). In addition to having PAO, 52.6% of hips had an anterior arthrotomy and 19.8% had a hip arthroscopy either to perform an osteochondroplasty of the femoral head-neck junction or to address labral pathologic changes. Of these 553 hips in which the labrum was visualized, labral morphologic status was graded as hypertrophic in 50%, normal in 45%, hypoplastic in 4%, and ossified in less than 1%. Decreased lateral center-edge angle and anterior center-edge angle and increased acetabular inclination were associated with labral hypertrophy, but chronicity of symptoms was not. Of the 553 hips, 64% had tears of the labrum, with the majority being degenerative-type tears. Conclusion: Labral pathologic changes are common in patients with symptomatic acetabular dysplasia. Labral hypertrophy, however, is not a universal finding, particularly in hips with mild dysplasia, and therefore should not be considered a reliable diagnostic criterion for instability.