Acetabular retroversion after triple pelvic osteotomy for Legg–Calvé–Perthes disease and its impact on the femoroacetabular impingement: a case/control study at 15 years of follow-up

The objective of this study was to compare the effect of triple pelvic osteotomy (TPO) in Legg-Calvé-Perthes disease (LCPD) on acetabular version in a group of patients who developed a femoroacetabular impingement (FAI) and a control group without FAI. Patients who received a TPO for unilateral LCPD were retrospectively included. Patients with bilateral LCPDs, requiring TPO with femoral procedures, or with incomplete imaging were excluded. Seven patients with FAI (FAI+) and eight patients without FAI (FAI-) were evaluated at a mean follow-up of 14.8 years. The two groups were comparable in demographic data, age at diagnosis, Herring score, and BMI. We measured anatomical acetabular version on computed tomography scans, the difference (delta) of acetabular version between the operated hip and the healthy hip, the McKibbin (femoral version + acetabular version), Stulberg, and Tönnis scoring system. The two groups were not statistically different on the Stulberg and Tönnis scores. All operated hip acetabula were retroverted, FAI+: -8.41° (range, -44 to 10.5), FAI-: -3.38° (range, -37.3 to 11.5) (P = 0.61). The average delta was FAI+: 23.79° (range, 1.5-59.5), FAI-: 20.14° (range, 5-45.3) (P = 0.68). All seven patients of the FAI+ group have pathologic McKibbin index (<30°) versus only four of the FAI- group (P = 0.03). TPO induces acetabular retroversion in patients with LCPD. This retroversion, assessed in a static benchmark (anterior pelvic plane), does not in itself explain the FAI.