The objective of this study was to investigate cases of femoroacetabular impingement (FAI) and analyze the risk factors for a painful hip at skeletal maturity after Perthes disease. We hypothesized that FAI occurs as a sequela of Perthes disease and that coxa plana and triple osteotomy of the pelvis (TOP) may be risk factors.

Ninety-five hips were included from 1981 to 2011, 56 of which were operated on with TOP (53) or shelf acetabuloplasty (3). The results were evaluated at a mean 13years of follow-up (range, 2–23years) with Oxford score and hip radiograph analysis including the Stulberg grade, coxometry, and presence of a femoral bump. FAI was characterized by positional hip pain with preserved joint space and aspherical/nonspherical femoral head.

The Oxford score was optimal (12) in 79 hips (75%) and 20 or above in nine hips (9.5%). Seventeen hips were rated Stulberg I (18%), 36 Stulberg II (38%), 27 Stulberg III (28%), and 15 Stulberg IV or V (16%). The average acetabular angle was 10° (range, −4 to 25), VCE 41.5° (range, 18–80), and VCA 38.5° (range, 13–70). A femoral bump was noted in 31 hips (33%). Five cases of FAI were managed operatively with at least pain relief. Hip pain at the latest follow-up correlated with coxa plana (P=0.0003) and femoral bump (P=0.007). No significant correlation was found with a history of hip surgery or coxometry parameters.

Perthes hips bear risk for later FAI. Risk factors include coxa plana and femoral bump. In case of TOP, it is advocated to avoid excessive tilt, which may cause FAI.

IV.