Increased Combined Anteversion Is an Independent Predictor of Ischiofemoral Impingement in the Setting of Borderline Dysplasia With Coxa Profunda.

PURPOSE: To investigate the differences in radiologic parameters between borderline dysplasia hips (BDDH) +/- coxa profunda and normal hips and to evaluate the correlations between these parameters and the prevalence of ischiofemoral impingement (IFI) in borderline dysplasia.

METHODS

The imaging of patients with BDDH (18° ≤ lateral center edge angle <25°) treated in our hospital from January 2018 to December 2019 was retrospective reviewed. These patients were divided into BDDH with coxa profunda (acetabular fossa touches the ilioischial line, pBDDH) and without coxa profunda (nBDDH) groups. The groups were compared with a control group with normal acetabular coverage. Neck-shaft angle, femoral offset, acetabular versions, acetabular coverage, ischial angle, femoral neck version, and combined anteversion were reviewed and analyzed using computed tomography imaging using one-way analysis of variance.

RESULTS

There were 43 patients (36 female/7 male, 26.13 ± 4.96 years) in the pBDDH group, 22 patients (17 female/5 male, 28.60 ± 5.89 years) in the nBDDH group, and 23 patients (14 female/9 male, 27.67 ± 5.98 years) in the control group. The pBDDH group had increased femoral version, ischial angle, acetabular versions, and decreased ischiofemoral space (IFS)/quadratus femoris space (QFS) than the other 2 groups. The IFS/QFS correlated with neck-shaft angle, femoral offset, femoral neck version, acetabular versions, ischial angle, femoral neck-lesser trochanter angle, posterior acetabular coverage, and combined anteversion in patients with BDDH. Combined anteversion at the 3-o'clock level was an independent predictor of a decreased IFS (beta = -0.348, P = .007) and QFS (beta = -0.255, P = .01, R2 = .550). Binary logistic regression demonstrated that patients with BDDH with large combined anteversion at the 3-o'clock level had a greater prevalence of IFI (odds ratio 1.148; P = .001, R2 = .505).

CONCLUSIONS

In patients with borderline dysplasia, the QFS/IFS significantly correlated with combined anteversion at the 3-o'clock level on clock face of acetabulum. BDDH with coxa profunda might have a greater prevalence of IFI because of large combined anteversion.

LEVEL OF EVIDENCE: III, retrospective comparative observation study.