Abstract

Periacetabular osteotomy (PAO) is effective in the management of developmental dysplasia of the hip and femoroacetabular impingement secondary to acetabular retroversion. During anteverting PAO for acetabular retroversion, the need for both labral treatment and femoral head–neck junction osteochondroplasty remains equivocal. Accordingly, this study evaluated patient-reported outcome measures (PROM) and reoperation rates after anteverting PAO with or without intraarticular intervention. Cases of anteverting PAO performed at a single institution between November 2009 and January 2016 were retrospectively reviewed. Patients were divided into three groups: no intervention and intraarticular intervention with arthrotomy or arthroscopy. Subsequently, patients were reclassified by the intraarticular procedure performed at surgery into major (labral repair, femoral head–neck osteochondroplasty) and minor (labral debridement, femoral/acetabular chondroplasty) groups. The cohort was 75% female, median age was 19.5 years and mean body mass index was 25.0 kg/m2. Preoperative to postoperative improvement was compared to minimal clinically important differences (MCID) for eight PROM. Patients receiving major interventions exceeded MCID in a greater proportion of PROM compared to minor and no intervention groups (P < 0.007); major or minor interventions did not increase the risk of reoperation over no intervention (P ≥ 0.39). Based on the current data, surgeons performing anteverting PAO for acetabular retroversion should perform arthroscopic or open labral repair and assess for impingement after the correction and perform a head–neck junction osteochondroplasty if indicated.

INTRODUCTION

The Bernese periacetabular osteotomy (PAO) is the preferred reorientation surgery for morphologic disorders of the hemipelvis in skeletally mature patients [1]. The procedure involves four sequential osteotomies and a controlled fracture to mobilize the acetabulum, allowing for surgical adjustment of the center of rotation, and anterior–posterior or lateral coverage of the femoral head. The procedure is an appropriate method to surgically treat symptomatic developmental dysplasia of the hip (DDH) or acetabular retroversion with posterior undercoverage [1, 2].

Acetabular retroversion can present in its pure form or may be a morphologic feature present in one out of five dysplastic hips [3, 4]. If femoral anteversion is normal, both groups most often present clinically with reduced internal rotation at 90° of flexion and pain with provocative hip maneuvers. So, even in the dysplastic hip where instability is of concern, impingement of the femoral head–neck junction against the retroverted rim represents an important pathophysiological feature that leads to intraarticular damage. The repeated impaction of the anterior head–neck junction of the femur against the retroverted rim will lead to early labral damage located in the area of impingement with late separation of the labrum and acetabular cartilage [5–7]. Damage to the labrum occurs early in the process, and is in clear contradistinction to what is seen with cam impingement, where the labral damage usually occurs late, after debonding of the cartilage. Patients with retroverted sockets therefore will present commonly with pain associated with labral damage that could be worse in those hips that have combined cam morphology or femoral retroversion.

Treatment of the labrum at the time of PAO surgery done for dysplasia has been controversial. In classic dysplasia, surgeons who do not recommend treatment simply state that with correction of the dysplasia, the dysplastic labrum is mostly offloaded and could heal, or even if it does not heal, the tear could become asymptomatic [8]. This would likely not be the case with the retroverted socket. During the anteverting PAO, the anterior rim and labrum may actually be translated to a more weight-bearing position and increase its load, thus the integrity of the labrum and chondrolabral junction would seem to be much more important. Despite this theoretical concern, Zurmuhle et al. [2] presented a series of retroverted sockets treated with PAO without labral repair and reported better results with PAO compared to surgical hip dislocation. However, there is a paucity of literature looking at these results from the perspective of the patient using validated patient-reported outcome measures (PROMs). Intuitively, it would make the most sense that visualization and treatment of intraarticular pathologies at the time of anteverting PAO would lead to improved outcomes as the surgeon would be able to address all possible pain generators.

The aim of this study was to determine if there was a difference in PROM or reoperation rates when comparing those patients undergoing anteverting PAO with intraarticular intervention (classified as a major or minor procedure) to those without. Furthermore, differences in PROM and reoperation rates based on the extent of the intraarticular intervention performed at the time of surgery were assessed.

METHODS

After obtaining Institutional Review Board approval (IRB No.: 17-001303), we retrospectively reviewed all patients undergoing PAO at a single tertiary referral center between November 2009 and January 2016. All patients were treated by one of two senior hip preservation surgeons (R.T.T. or R.J.S.). Candidates for PAO had symptomatic DDH or femoroacetabular impingement (FAI), defined by lateral center-edge angle (LCEA) [9] (<25° for DDH; >40° for FAI), acetabular index [10] (>10° for DDH; <0° for FAI), anterior center-edge angle (ACEA) [11] (<25° for DDH; >45° for FAI) and Tönnis Grade 0 or Grade 1 degenerative changes [12] with an age ≤50 years. We identified 212 patients (239 hips) who met these criteria. From this group, we further selected patients undergoing anteverting PAO yielding 41 patients (48 hips), which comprised the final cohort. All patients were symptomatic and complained of hip pain associated with activities. Preoperative review of pelvic radiographs identified patients with lateral undercoverage in addition to retroversion, or with pure acetabular retroversion. All patients had failed non-operative management for at least 3 months. The mean age at the time of surgery was 21.2 ± 5.6 years (range: 13.4–36.8 years) and mean body mass index (BMI) 25.0 ± 5.4 kg/m2 (range: 17.1–39.2 kg/m2) (Table I). The average preoperative range of motion for these patients was 13.5 ± 9.1° (range: 0–35°) of internal rotation at 90° of flexion and 96.8 ± 9.5° (range: 85–120°) of straight flexion (Table I). Twenty-one patients (22 hips) had combined acetabular retroversion and dysplasia (Table I).

Table I.

Patient characteristics by surgical technique and intraarticular intervention

. Ante. PAO (N = 8) . Ante. PAO + arthrotomy (N = 23) . Ante. PAO + arthroscopy (N = 17) . P-value . No intervention (N = 14) . Minor (N = 7) . Major (N = 27) . P-value . Total (N = 48) . Age at surgery    0.50    0.45   Mean (SD) 20.8 (6.1) 21.9 (6.5) 20.4 (4.0)  22.7 (6.9) 21.0 (4.5) 20.4 (5.1)  21.2 (5.6)  Median 18.5 20.0 20.1  19.6 19.8 19.3  19.5  Q1, Q3 16.9, 23.6 16.7, 26.9 17.2, 23.0  16.9, 27.9 17.8, 26.6 16.5, 23.0  16.9, 24.0  Range (15.9–32.7) (13.4–36.8) (15.0–27.5)  (15.9–36.8) (15.6–27.5) (13.4–34.4)  (13.4–36.8) Gender    0.78    0.65   Female 7 (87.5%) 16 (69.6%) 13 (76.5%)  12 (85.7%) 5 (71.4%) 19 (70.4%)  36 (75.0%)  Male 1 (12.5%) 7 (30.4%) 4 (23.5%)  2 (14.3%) 2 (28.6%) 8 (29.6%)  12 (25.0%) BMI (kg/m2)    0.25    0.47   Mean (SD) 27.4 (5.6) 24.0 (4.9) 25.1 (5.9)  25.5 (5.1) 22.8 (6.1) 25.2 (5.4)  25.0 (5.4)  Median 27.0 22.8 23.1  24.2 21.3 24.4  23.2  Q1, Q3 22.6, 30.8 21.1, 25.3 21.3, 27.0  21.8, 29.0 19.2, 22.8 21.7, 27.0  21.3, 27.5  Range (21.3–37.4) (17.1–36.4) (17.4–39.2)  (19.3–37.4) (17.4–36.0) (17.1–39.2)  (17.1–39.2) Diagnosis    0.41a    0.17a   DDH + retroversion 3 (37.5%) 9 (39.1%) 10 (58.8%)  8 (57.1%) 1 (14.3%) 13 (48.1%)  22 (45.8%)  Retroversion 5 (62.5%) 14 (60.9%) 7 (41.2%)  6 (42.9%) 6 (85.7%) 14 (51.9%)  26 (54.2%) Prior surgery to affected hip    0.096    0.25   No 6 (75.0%) 17 (73.9%) 16 (94.1%)  11 (78.6%) 4 (57.1%) 24 (88.9%)  39 (81.3%)  Yes 2 (25.0%) 6 (26.1%) 1 (5.9%)  3 (21.4%) 3 (42.9%) 3 (11.1%)  9 (18.8%) Range of motion: flexion (deg)  Preoperative 96.7 (10.3) 95.6 (8.9) 98.3 (10.3) 0.70 98.3 (12.2) 92.5 (2.7) 97.3 (9.4) 0.14 96.8 (9.5)  Postoperative 98.6 (5.6) 103.5 (7.0) 98.2 (6.1) 0.11 100.0 (6.1) 97.5 (4.2) 101.7 (7.5) 0.29 100.7 (6.8)  Change (Post-Pre) 2.5 (6.9) 9.4 (8.6) 1.4 (11.7) 0.086 5.0 (7.6) 5.0 (3.2) 5.4 (12.2) 0.99 5.3 (10.2)   P-value 0.56 0.001 0.55  0.16 0.063 0.035   Range of motion: internal rotation (deg)  Preoperative 13.6 (6.9) 13.5 (8.8) 13.3 (10.8) 0.99 13.5 (6.3) 10.0 (6.3) 14.3 (10.7) 0.40 13.5 (9.1)  Postoperative 27.1 (8.1) 33.3 (13.8) 27.1 (9.6) 0.27 29.4 (9.2) 28.0 (11.0) 30.2 (12.8) 0.91 29.7 (11.5)  Change (Post-Pre) 13.6 (9.0) 19.7 (12.0) 15.0 (11.8) 0.32 15.6 (8.8) 19.0 (6.5) 16.6 (13.3) 0.66 16.7 (11.4)   P-value 0.031 <0.001 0.001  0.008 0.063     . Ante. PAO (N = 8) . Ante. PAO + arthrotomy (N = 23) . Ante. PAO + arthroscopy (N = 17) . P-value . No intervention (N = 14) . Minor (N = 7) . Major (N = 27) . P-value . Total (N = 48) . Age at surgery    0.50    0.45   Mean (SD) 20.8 (6.1) 21.9 (6.5) 20.4 (4.0)  22.7 (6.9) 21.0 (4.5) 20.4 (5.1)  21.2 (5.6)  Median 18.5 20.0 20.1  19.6 19.8 19.3  19.5  Q1, Q3 16.9, 23.6 16.7, 26.9 17.2, 23.0  16.9, 27.9 17.8, 26.6 16.5, 23.0  16.9, 24.0  Range (15.9–32.7) (13.4–36.8) (15.0–27.5)  (15.9–36.8) (15.6–27.5) (13.4–34.4)  (13.4–36.8) Gender    0.78    0.65   Female 7 (87.5%) 16 (69.6%) 13 (76.5%)  12 (85.7%) 5 (71.4%) 19 (70.4%)  36 (75.0%)  Male 1 (12.5%) 7 (30.4%) 4 (23.5%)  2 (14.3%) 2 (28.6%) 8 (29.6%)  12 (25.0%) BMI (kg/m2)    0.25    0.47   Mean (SD) 27.4 (5.6) 24.0 (4.9) 25.1 (5.9)  25.5 (5.1) 22.8 (6.1) 25.2 (5.4)  25.0 (5.4)  Median 27.0 22.8 23.1  24.2 21.3 24.4  23.2  Q1, Q3 22.6, 30.8 21.1, 25.3 21.3, 27.0  21.8, 29.0 19.2, 22.8 21.7, 27.0  21.3, 27.5  Range (21.3–37.4) (17.1–36.4) (17.4–39.2)  (19.3–37.4) (17.4–36.0) (17.1–39.2)  (17.1–39.2) Diagnosis    0.41a    0.17a   DDH + retroversion 3 (37.5%) 9 (39.1%) 10 (58.8%)  8 (57.1%) 1 (14.3%) 13 (48.1%)  22 (45.8%)  Retroversion 5 (62.5%) 14 (60.9%) 7 (41.2%)  6 (42.9%) 6 (85.7%) 14 (51.9%)  26 (54.2%) Prior surgery to affected hip    0.096    0.25   No 6 (75.0%) 17 (73.9%) 16 (94.1%)  11 (78.6%) 4 (57.1%) 24 (88.9%)  39 (81.3%)  Yes 2 (25.0%) 6 (26.1%) 1 (5.9%)  3 (21.4%) 3 (42.9%) 3 (11.1%)  9 (18.8%) Range of motion: flexion (deg)  Preoperative 96.7 (10.3) 95.6 (8.9) 98.3 (10.3) 0.70 98.3 (12.2) 92.5 (2.7) 97.3 (9.4) 0.14 96.8 (9.5)  Postoperative 98.6 (5.6) 103.5 (7.0) 98.2 (6.1) 0.11 100.0 (6.1) 97.5 (4.2) 101.7 (7.5) 0.29 100.7 (6.8)  Change (Post-Pre) 2.5 (6.9) 9.4 (8.6) 1.4 (11.7) 0.086 5.0 (7.6) 5.0 (3.2) 5.4 (12.2) 0.99 5.3 (10.2)   P-value 0.56 0.001 0.55  0.16 0.063 0.035   Range of motion: internal rotation (deg)  Preoperative 13.6 (6.9) 13.5 (8.8) 13.3 (10.8) 0.99 13.5 (6.3) 10.0 (6.3) 14.3 (10.7) 0.40 13.5 (9.1)  Postoperative 27.1 (8.1) 33.3 (13.8) 27.1 (9.6) 0.27 29.4 (9.2) 28.0 (11.0) 30.2 (12.8) 0.91 29.7 (11.5)  Change (Post-Pre) 13.6 (9.0) 19.7 (12.0) 15.0 (11.8) 0.32 15.6 (8.8) 19.0 (6.5) 16.6 (13.3) 0.66 16.7 (11.4)   P-value 0.031 <0.001 0.001  0.008 0.063    Table I.

Patient characteristics by surgical technique and intraarticular intervention

. Ante. PAO (N = 8) . Ante. PAO + arthrotomy (N = 23) . Ante. PAO + arthroscopy (N = 17) . P-value . No intervention (N = 14) . Minor (N = 7) . Major (N = 27) . P-value . Total (N = 48) . Age at surgery    0.50    0.45   Mean (SD) 20.8 (6.1) 21.9 (6.5) 20.4 (4.0)  22.7 (6.9) 21.0 (4.5) 20.4 (5.1)  21.2 (5.6)  Median 18.5 20.0 20.1  19.6 19.8 19.3  19.5  Q1, Q3 16.9, 23.6 16.7, 26.9 17.2, 23.0  16.9, 27.9 17.8, 26.6 16.5, 23.0  16.9, 24.0  Range (15.9–32.7) (13.4–36.8) (15.0–27.5)  (15.9–36.8) (15.6–27.5) (13.4–34.4)  (13.4–36.8) Gender    0.78    0.65   Female 7 (87.5%) 16 (69.6%) 13 (76.5%)  12 (85.7%) 5 (71.4%) 19 (70.4%)  36 (75.0%)  Male 1 (12.5%) 7 (30.4%) 4 (23.5%)  2 (14.3%) 2 (28.6%) 8 (29.6%)  12 (25.0%) BMI (kg/m2)    0.25    0.47   Mean (SD) 27.4 (5.6) 24.0 (4.9) 25.1 (5.9)  25.5 (5.1) 22.8 (6.1) 25.2 (5.4)  25.0 (5.4)  Median 27.0 22.8 23.1  24.2 21.3 24.4  23.2  Q1, Q3 22.6, 30.8 21.1, 25.3 21.3, 27.0  21.8, 29.0 19.2, 22.8 21.7, 27.0  21.3, 27.5  Range (21.3–37.4) (17.1–36.4) (17.4–39.2)  (19.3–37.4) (17.4–36.0) (17.1–39.2)  (17.1–39.2) Diagnosis    0.41a    0.17a   DDH + retroversion 3 (37.5%) 9 (39.1%) 10 (58.8%)  8 (57.1%) 1 (14.3%) 13 (48.1%)  22 (45.8%)  Retroversion 5 (62.5%) 14 (60.9%) 7 (41.2%)  6 (42.9%) 6 (85.7%) 14 (51.9%)  26 (54.2%) Prior surgery to affected hip    0.096    0.25   No 6 (75.0%) 17 (73.9%) 16 (94.1%)  11 (78.6%) 4 (57.1%) 24 (88.9%)  39 (81.3%)  Yes 2 (25.0%) 6 (26.1%) 1 (5.9%)  3 (21.4%) 3 (42.9%) 3 (11.1%)  9 (18.8%) Range of motion: flexion (deg)  Preoperative 96.7 (10.3) 95.6 (8.9) 98.3 (10.3) 0.70 98.3 (12.2) 92.5 (2.7) 97.3 (9.4) 0.14 96.8 (9.5)  Postoperative 98.6 (5.6) 103.5 (7.0) 98.2 (6.1) 0.11 100.0 (6.1) 97.5 (4.2) 101.7 (7.5) 0.29 100.7 (6.8)  Change (Post-Pre) 2.5 (6.9) 9.4 (8.6) 1.4 (11.7) 0.086 5.0 (7.6) 5.0 (3.2) 5.4 (12.2) 0.99 5.3 (10.2)   P-value 0.56 0.001 0.55  0.16 0.063 0.035   Range of motion: internal rotation (deg)  Preoperative 13.6 (6.9) 13.5 (8.8) 13.3 (10.8) 0.99 13.5 (6.3) 10.0 (6.3) 14.3 (10.7) 0.40 13.5 (9.1)  Postoperative 27.1 (8.1) 33.3 (13.8) 27.1 (9.6) 0.27 29.4 (9.2) 28.0 (11.0) 30.2 (12.8) 0.91 29.7 (11.5)  Change (Post-Pre) 13.6 (9.0) 19.7 (12.0) 15.0 (11.8) 0.32 15.6 (8.8) 19.0 (6.5) 16.6 (13.3) 0.66 16.7 (11.4)   P-value 0.031 <0.001 0.001  0.008 0.063     . Ante. PAO (N = 8) . Ante. PAO + arthrotomy (N = 23) . Ante. PAO + arthroscopy (N = 17) . P-value . No intervention (N = 14) . Minor (N = 7) . Major (N = 27) . P-value . Total (N = 48) . Age at surgery    0.50    0.45   Mean (SD) 20.8 (6.1) 21.9 (6.5) 20.4 (4.0)  22.7 (6.9) 21.0 (4.5) 20.4 (5.1)  21.2 (5.6)  Median 18.5 20.0 20.1  19.6 19.8 19.3  19.5  Q1, Q3 16.9, 23.6 16.7, 26.9 17.2, 23.0  16.9, 27.9 17.8, 26.6 16.5, 23.0  16.9, 24.0  Range (15.9–32.7) (13.4–36.8) (15.0–27.5)  (15.9–36.8) (15.6–27.5) (13.4–34.4)  (13.4–36.8) Gender    0.78    0.65   Female 7 (87.5%) 16 (69.6%) 13 (76.5%)  12 (85.7%) 5 (71.4%) 19 (70.4%)  36 (75.0%)  Male 1 (12.5%) 7 (30.4%) 4 (23.5%)  2 (14.3%) 2 (28.6%) 8 (29.6%)  12 (25.0%) BMI (kg/m2)    0.25    0.47   Mean (SD) 27.4 (5.6) 24.0 (4.9) 25.1 (5.9)  25.5 (5.1) 22.8 (6.1) 25.2 (5.4)  25.0 (5.4)  Median 27.0 22.8 23.1  24.2 21.3 24.4  23.2  Q1, Q3 22.6, 30.8 21.1, 25.3 21.3, 27.0  21.8, 29.0 19.2, 22.8 21.7, 27.0  21.3, 27.5  Range (21.3–37.4) (17.1–36.4) (17.4–39.2)  (19.3–37.4) (17.4–36.0) (17.1–39.2)  (17.1–39.2) Diagnosis    0.41a    0.17a   DDH + retroversion 3 (37.5%) 9 (39.1%) 10 (58.8%)  8 (57.1%) 1 (14.3%) 13 (48.1%)  22 (45.8%)  Retroversion 5 (62.5%) 14 (60.9%) 7 (41.2%)  6 (42.9%) 6 (85.7%) 14 (51.9%)  26 (54.2%) Prior surgery to affected hip    0.096    0.25   No 6 (75.0%) 17 (73.9%) 16 (94.1%)  11 (78.6%) 4 (57.1%) 24 (88.9%)  39 (81.3%)  Yes 2 (25.0%) 6 (26.1%) 1 (5.9%)  3 (21.4%) 3 (42.9%) 3 (11.1%)  9 (18.8%) Range of motion: flexion (deg)  Preoperative 96.7 (10.3) 95.6 (8.9) 98.3 (10.3) 0.70 98.3 (12.2) 92.5 (2.7) 97.3 (9.4) 0.14 96.8 (9.5)  Postoperative 98.6 (5.6) 103.5 (7.0) 98.2 (6.1) 0.11 100.0 (6.1) 97.5 (4.2) 101.7 (7.5) 0.29 100.7 (6.8)  Change (Post-Pre) 2.5 (6.9) 9.4 (8.6) 1.4 (11.7) 0.086 5.0 (7.6) 5.0 (3.2) 5.4 (12.2) 0.99 5.3 (10.2)   P-value 0.56 0.001 0.55  0.16 0.063 0.035   Range of motion: internal rotation (deg)  Preoperative 13.6 (6.9) 13.5 (8.8) 13.3 (10.8) 0.99 13.5 (6.3) 10.0 (6.3) 14.3 (10.7) 0.40 13.5 (9.1)  Postoperative 27.1 (8.1) 33.3 (13.8) 27.1 (9.6) 0.27 29.4 (9.2) 28.0 (11.0) 30.2 (12.8) 0.91 29.7 (11.5)  Change (Post-Pre) 13.6 (9.0) 19.7 (12.0) 15.0 (11.8) 0.32 15.6 (8.8) 19.0 (6.5) 16.6 (13.3) 0.66 16.7 (11.4)   P-value 0.031 <0.001 0.001  0.008 0.063    

For the analyses, the 48 hips were divided into three groups: no intraarticular intervention and intervention with arthrotomy or arthroscopy. A separate analysis was done by classifying hips by the extent of intraarticular intervention performed at the time of surgery into major (labral repair or femoral head–neck osteochondroplasty) and minor (labral debridement or femoral/acetabular chondroplasty) groups. A patient simultaneously receiving a major and minor intraarticular intervention was included in the major intraarticular intervention group. Patients who did not have arthrotomy or arthroscopy were included in the no intervention group. There were six additional patients (six hips) who underwent hip arthroscopy or arthrotomy in the no intervention group.

As part of a prospectively collected hip preservation registry, 12 PROM were recorded at the preoperative and most recent clinical follow-up visits, with the latter occurring at a mean of 3.2 years postoperatively (range: 0.9–5.9 years). PROM included the UCLA activity score, Harris Hip Score (HHS) [13], five subcomponents of the Hip Disability and Osteoarthritis Outcome Score (HOOS) [Pain, Activities of Daily Living (ADL), Sports and Recreation, Quality of Life], four subcomponents of the Western Ontario and McMaster Universities Questionnaire (WOMAC) (Pain, Stiffness, Physical, Total) and two subcomponents of the SF-12 Health Survey (Physical and Mental). Each score has been used previously to assess the functional outcome of patients treated with PAO for symptomatic dysplasia [14–17]. For a subset of eight PROM collected in this study, the preoperative to postoperative change was compared to the established minimal clinically important difference (MCID) reported in the literature [18].

The data are presented as counts and percentages for categorical variables or means and standard deviations for continuous variables. Retroversion index [19] and alpha angle [20] measurements were obtained from preoperative and postoperative AP pelvic and frog-leg lateral radiographs, respectively, for the 41 patients (48 hips) undergoing anteverting PAO. All postoperative AP pelvic radiographs were reviewed by a senior author to confirm appropriate correction following anteverting PAO. Comparisons of baseline characteristics and PROM (preoperative, postoperative, the change from preoperative to postoperative and the difference between the preoperative to postoperative change and MCID) were made using generalized estimating equations to account for the fact that a patient may have more than one hip included in the analysis, and that results for those hips may be correlated. Where appropriate, posthoc pairwise comparisons were conducted using the generalized estimating equations with P-values adjusted for multiple comparisons using the Benjamini–Hochberg false discovery rate method [21]. The proportion of PROM exceeding the MCID was compared between groups using the Fisher’s exact test. Cox proportional hazards regression with a robust variance estimator were used to assess the incidence of reoperations following anteverting PAO. Counts and the nature of postoperative complications and reoperations were confirmed in the medical record. Reoperation was defined as any additional procedure to the affected hip, not including isolated hardware removal. All analyses were performed using SAS version 9.4 (SAS Institute Inc., Cary, NC, USA) and R version 3.4.2 (R Core Team, Vienna, Austria).

RESULTS

Forty-one patients (48 hips) are in the final cohort. Twenty patients (22 hips) underwent arthrotomy, 14 patients (16 hips) underwent arthroscopy and 5 patients (6 hips) received anteverting PAO alone. Two patients (four hips) underwent staged bilateral anteverting PAO with side-to-side differences in the surgical technique. In both cases, the left hip underwent anteverting PAO alone while the right hip received anteverting PAO + arthrotomy in one case and anteverting PAO + arthroscopy in the other. The anteverting PAO, anteverting PAO + arthrotomy and anteverting PAO + arthroscopy groups did not differ significantly by age, BMI, sex, incidence of prior surgery to the affected hip or range of motion in flexion or internal rotation (P ≥ 0.096) (Table I). There were no significant differences in preoperative Tönnis grade, LCEA, ACEA, acetabular inclination, alpha angle or retroversion index (P ≥ 0.25) (Table II). The preoperative to postoperative improvement exceeded the MCID for 7, 3 and 2 of 8 PROM for anteverting PAO + arthrotomy, anteverting PAO + arthroscopy and anteverting PAO alone, respectively (Table III). The proportion of PROM that surpassed the MCID was significantly greater for anteverting PAO + arthrotomy versus anteverting PAO alone (P = 0.04) but did not differ between anteverting PAO + arthrotomy and anteverting PAO + arthroscopy (P = 0.12). The distribution of PROM by diagnosis is presented in Supplementary Table SI.

Table II.

Radiographic characteristics by surgical technique and intraarticular intervention

. Ante. PAO (N = 8) . Ante. PAO + arthrotomy (N = 23) . Ante. PAO + arthroscopy (N = 17) . P-value . No intervention (N = 14) . Minor (N = 7) . Major (N = 27) . P-value . Total (N = 48) . Tonnis classification    0.87    0.80   Grade 0 6 (75.0%) 17 (73.9%) 13 (76.5%)  11 (78.6%) 5 (71.4%) 20 (74.1%)  36 (75.0%)  Grade 1 2 (25.0%) 6 (26.1%) 4 (23.5%)  3 (21.4%) 2 (28.6%) 7 (25.9%)  12 (25.0%) Lateral center-edge angle (deg)  Preoperative 27.0 (7.0) 25.7 (10.4) 26.4 (7.0) 0.91 26.1 (10.6) 28.7 (10.6) 25.5 (7.1) 0.74 26.1 (8.7)  Postoperative 33.6 (4.8) 32.2 (6.5) 33.1 (6.4) 0.87 33.9 (6.8) 35.4 (4.6) 31.2 (5.9) 0.26 32.7 (6.1)  Change (Post-Pre) 7.6 (5.6) 6.6 (14.2) 3.9 (4.5) 0.38 8.5 (12.7) 7.9 (14.7) 3.8 (8.4) 0.50 6.0 (10.9)   P-value 0.13 0.18 0.023  0.064 0.25 0.13   Acetabular inclination (deg)  Preoperative 6.2 (6.4) 7.8 (6.9) 10.1 (16.4) 0.70 7.9 (6.8) 5.4 (9.6) 9.3 (13.1) 0.66 8.4 (11.0)  Postoperative −1.0 (2.2) 5.0 (6.8) −1.7 (3.0) 0.006 4.6 (9.2) −0.8 (5.5) 1.2 (3.1) 0.34 2.1 (6.2)  Change (Post-Pre) −9.6 (6.4) −3.0 (7.2) −5.7 (3.6) 0.18 −4.8 (8.6) −7.7 (7.2) −4.0 (4.6) 0.54 −4.8 (6.4)   P-value 0.13 0.096 0.008  0.11 0.13 0.003   Alpha angle (deg)  Preoperative 45.6 (2.7) 52.9 (7.4) 54.5 (9.9) 0.056 46.4 (3.0)a 47.3 (4.4)a 56.4 (8.6)b 0.002 52.2 (8.3)  Postoperative 46.3 (2.0) 46.6 (2.3) 46.6 (2.5) 0.92 46.7 (2.0) 47.0 (3.3 46.4 (2.1) 0.84 46.6 (2.3)  Change (Post-Pre) 0.7 (1.5)b −6.3 (6.7)a −7.9 (10.6)a 0.043 0.3 (1.8)a −0.3 (2.4)a −10.1 (8.5)b <0.001 −5.7 (8.2)   P-value 0.19 <0.001 0.006  0.51 0.94 <0.001   Retroversion index  Preoperative 35.2 (9.9) 36.1 (5.5) 36.8 (6.2) 0.89 35.6 (8.2) 35.7 (2.9) 36.6 (6.5) 0.45 36.2 (6.6)  Postoperative 7.5 (6.8) 5.9 (8.4) 8.0 (9.0) 0.80 6.2 (6.4) 4.8 (4.3) 7.7 (9.7) 0.40 6.9 (8.3)  Change (Post-Pre) −26.5 (12.1) −29.9 (8.1) −28.8 (10.3) 0.78 −28.1 (10.9) −30.9 (6.0) −28.9 (9.7) 0.82 −28.9 (9.5)   P-value 0.016 <0.001 <0.001  0.001 0.016 <0.001    . Ante. PAO (N = 8) . Ante. PAO + arthrotomy (N = 23) . Ante. PAO + arthroscopy (N = 17) . P-value . No intervention (N = 14) . Minor (N = 7) . Major (N = 27) . P-value . Total (N = 48) . Tonnis classification    0.87    0.80   Grade 0 6 (75.0%) 17 (73.9%) 13 (76.5%)  11 (78.6%) 5 (71.4%) 20 (74.1%)  36 (75.0%)  Grade 1 2 (25.0%) 6 (26.1%) 4 (23.5%)  3 (21.4%) 2 (28.6%) 7 (25.9%)  12 (25.0%) Lateral center-edge angle (deg)  Preoperative 27.0 (7.0) 25.7 (10.4) 26.4 (7.0) 0.91 26.1 (10.6) 28.7 (10.6) 25.5 (7.1) 0.74 26.1 (8.7)  Postoperative 33.6 (4.8) 32.2 (6.5) 33.1 (6.4) 0.87 33.9 (6.8) 35.4 (4.6) 31.2 (5.9) 0.26 32.7 (6.1)  Change (Post-Pre) 7.6 (5.6) 6.6 (14.2) 3.9 (4.5) 0.38 8.5 (12.7) 7.9 (14.7) 3.8 (8.4) 0.50 6.0 (10.9)   P-value 0.13 0.18 0.023  0.064 0.25 0.13   Acetabular inclination (deg)  Preoperative 6.2 (6.4) 7.8 (6.9) 10.1 (16.4) 0.70 7.9 (6.8) 5.4 (9.6) 9.3 (13.1) 0.66 8.4 (11.0)  Postoperative −1.0 (2.2) 5.0 (6.8) −1.7 (3.0) 0.006 4.6 (9.2) −0.8 (5.5) 1.2 (3.1) 0.34 2.1 (6.2)  Change (Post-Pre) −9.6 (6.4) −3.0 (7.2) −5.7 (3.6) 0.18 −4.8 (8.6) −7.7 (7.2) −4.0 (4.6) 0.54 −4.8 (6.4)   P-value 0.13 0.096 0.008  0.11 0.13 0.003   Alpha angle (deg)  Preoperative 45.6 (2.7) 52.9 (7.4) 54.5 (9.9) 0.056 46.4 (3.0)a 47.3 (4.4)a 56.4 (8.6)b 0.002 52.2 (8.3)  Postoperative 46.3 (2.0) 46.6 (2.3) 46.6 (2.5) 0.92 46.7 (2.0) 47.0 (3.3 46.4 (2.1) 0.84 46.6 (2.3)  Change (Post-Pre) 0.7 (1.5)b −6.3 (6.7)a −7.9 (10.6)a 0.043 0.3 (1.8)a −0.3 (2.4)a −10.1 (8.5)b <0.001 −5.7 (8.2)   P-value 0.19 <0.001 0.006  0.51 0.94 <0.001   Retroversion index  Preoperative 35.2 (9.9) 36.1 (5.5) 36.8 (6.2) 0.89 35.6 (8.2) 35.7 (2.9) 36.6 (6.5) 0.45 36.2 (6.6)  Postoperative 7.5 (6.8) 5.9 (8.4) 8.0 (9.0) 0.80 6.2 (6.4) 4.8 (4.3) 7.7 (9.7) 0.40 6.9 (8.3)  Change (Post-Pre) −26.5 (12.1) −29.9 (8.1) −28.8 (10.3) 0.78 −28.1 (10.9) −30.9 (6.0) −28.9 (9.7) 0.82 −28.9 (9.5)   P-value 0.016 <0.001 <0.001  0.001 0.016 <0.001   Table II.

Radiographic characteristics by surgical technique and intraarticular intervention

. Ante. PAO (N = 8) . Ante. PAO + arthrotomy (N = 23) . Ante. PAO + arthroscopy (N = 17) . P-value . No intervention (N = 14) . Minor (N = 7) . Major (N = 27) . P-value . Total (N = 48) . Tonnis classification    0.87    0.80   Grade 0 6 (75.0%) 17 (73.9%) 13 (76.5%)  11 (78.6%) 5 (71.4%) 20 (74.1%)  36 (75.0%)  Grade 1 2 (25.0%) 6 (26.1%) 4 (23.5%)  3 (21.4%) 2 (28.6%) 7 (25.9%)  12 (25.0%) Lateral center-edge angle (deg)  Preoperative 27.0 (7.0) 25.7 (10.4) 26.4 (7.0) 0.91 26.1 (10.6) 28.7 (10.6) 25.5 (7.1) 0.74 26.1 (8.7)  Postoperative 33.6 (4.8) 32.2 (6.5) 33.1 (6.4) 0.87 33.9 (6.8) 35.4 (4.6) 31.2 (5.9) 0.26 32.7 (6.1)  Change (Post-Pre) 7.6 (5.6) 6.6 (14.2) 3.9 (4.5) 0.38 8.5 (12.7) 7.9 (14.7) 3.8 (8.4) 0.50 6.0 (10.9)   P-value 0.13 0.18 0.023  0.064 0.25 0.13   Acetabular inclination (deg)  Preoperative 6.2 (6.4) 7.8 (6.9) 10.1 (16.4) 0.70 7.9 (6.8) 5.4 (9.6) 9.3 (13.1) 0.66 8.4 (11.0)  Postoperative −1.0 (2.2) 5.0 (6.8) −1.7 (3.0) 0.006 4.6 (9.2) −0.8 (5.5) 1.2 (3.1) 0.34 2.1 (6.2)  Change (Post-Pre) −9.6 (6.4) −3.0 (7.2) −5.7 (3.6) 0.18 −4.8 (8.6) −7.7 (7.2) −4.0 (4.6) 0.54 −4.8 (6.4)   P-value 0.13 0.096 0.008  0.11 0.13 0.003   Alpha angle (deg)  Preoperative 45.6 (2.7) 52.9 (7.4) 54.5 (9.9) 0.056 46.4 (3.0)a 47.3 (4.4)a 56.4 (8.6)b 0.002 52.2 (8.3)  Postoperative 46.3 (2.0) 46.6 (2.3) 46.6 (2.5) 0.92 46.7 (2.0) 47.0 (3.3 46.4 (2.1) 0.84 46.6 (2.3)  Change (Post-Pre) 0.7 (1.5)b −6.3 (6.7)a −7.9 (10.6)a 0.043 0.3 (1.8)a −0.3 (2.4)a −10.1 (8.5)b <0.001 −5.7 (8.2)   P-value 0.19 <0.001 0.006  0.51 0.94 <0.001   Retroversion index  Preoperative 35.2 (9.9) 36.1 (5.5) 36.8 (6.2) 0.89 35.6 (8.2) 35.7 (2.9) 36.6 (6.5) 0.45 36.2 (6.6)  Postoperative 7.5 (6.8) 5.9 (8.4) 8.0 (9.0) 0.80 6.2 (6.4) 4.8 (4.3) 7.7 (9.7) 0.40 6.9 (8.3)  Change (Post-Pre) −26.5 (12.1) −29.9 (8.1) −28.8 (10.3) 0.78 −28.1 (10.9) −30.9 (6.0) −28.9 (9.7) 0.82 −28.9 (9.5)   P-value 0.016 <0.001 <0.001  0.001 0.016 <0.001    . Ante. PAO (N = 8) . Ante. PAO + arthrotomy (N = 23) . Ante. PAO + arthroscopy (N = 17)