Are there sex-dependent differences in acetabular dysplasia characteristics?

Background: Many patients who undergo periacetabular osteotomy (PAO) for symptomatic acetabular dysplasia experience decreased pain and improved function, yet some experience inadequate clinical improvement. The etiologies of treatment failure have not been completely defined, and sex-dependent disease characteristics that may be associated with less pain relief are not understood.

Question/purposes: We sought to determine whether there were clinically important sex-specific differences between male and female patients undergoing PAO for acetabular dysplasia in terms of (1) clinical parameters (anthropomorphic traits and hip scores), (2) radiographic findings, and (3) intraoperative findings at the time of PAO, in particular findings potentially associated with femoroacetabular impingement (FAI) such as chondromalacia at the head-neck junction, impingement trough, or reduced head-neck offset.

Methods: Between 2007 and 2012 we treated 245 patients (270 hips) with a PAO for symptomatic acetabular dysplasia. Of those, 16 patients (16 hips; 6%) had insufficient documentation for review in the medical record and another 49 patients (51 hips; 19%) met prespecified exclusion criteria, leaving 180 patients (203 hips; 75%) for analysis in this retrospective study. One hundred thirty-nine patients were females and 41 were males. Clinical data including patient demographics, physical examination, patient self-reported outcome scores, radiographic morphologic features, and intraoperative findings were collected prospectively as part of an institutional registry. Statistical analysis was performed with univariate and multivariate analyses.

Results: Mean age was similar among sexes; however, BMI was greater in males compared with females (26 versus 24 kg/m(2); p = 0.002). Males had less hip ROM including internal rotation at 90° flexion (14° ± 13.8° versus 25° ± 16.2°; p = 0.001). Males had higher preoperative UCLA (7 ± 2, versus 6 ± 2; p = 0.02) and Harris hip scores (63 ± 15 versus 58 ± 16; p = 0.04). Radiographically, a crossover sign (88% versus 39%; p < 0.001) and posterior wall sign (92% versus 63%; p < 0.001) were more common in males. Males had greater alpha angles on the frog lateral (63° ± 15.3° versus 58° ± 16°; p = 0.04) and Dunn radiograph views (64° ± 15.5° versus 56° ± 14.8°; p = 0.02). The incidence of femoral head-neck chondromalacia (62% versus 82%; p = 0.03) and an impingement trough observed at surgery was greater in males (35% versus 17%; p = 0.01). Multivariate analysis showed differences between the sexes for reduced internal rotation in flexion, a higher Dunn alpha angle, increased incidence of a crossover sign, and a lower anterior center-edge angle.

Conclusions: There are sex-dependent, disease characteristic differences in patients with symptomatic acetabular dysplasia. Most notably, male patients have a greater prevalence of clinical, radiographic, and intraarticular findings consistent with concurrent FAI and instability and potentially a heightened risk of secondary FAI after PAO, however postoperative and long-term followup are needed to confirm these findings and it remains unclear which patients need surgical correction of the impingement and instability. Preoperative evaluation of acetabular dysplasia in males should at least include careful attention to factors associated with symptomatic FAI; however, further studies are needed to determine when surgical correction is needed.