The influence of extra-articular changes on hip function in young adults with a history of Perthes disease.

Abstract

Residual deformities after Perthes disease, such as high-rising greater trochanter (HGT) and reduced femoral offset (FO), may compromise abductor function and influence long-term hip function. To determine the prevalence of HGT and abnormal FO in young adults with healed unilateral Perthes disease and evaluate their associations with the Stulberg classification and hip function. In this cross-sectional follow-up study, 180 individuals (mean age 28.2 years, 72% male) previously diagnosed with unilateral Perthes disease were examined with radiographs and clinical tests. Articulo-trochanteric distance (ATD) and FO were measured on calibrated pelvic radiographs. Femoral head shape was classified using a modified 3-group Stulberg classification. Hip function was evaluated using the Trendelenburg test, passive hip abduction range of motion, and the Copenhagen Hip and Groin Outcome Score (HAGOS). ATD was significantly lower in Perthes hips compared to contralateral hips (7.7 mm [SD 9.6] vs. 20.7 mm [SD 6.2], <i>p</i> < 0.001). HGT was present in 70 individuals (39%), and a positive Trendelenburg test was observed in 12 Perthes hips (7%). Risk factors for a positive test included hip pain, aspherical femoral head, and surgical treatment. Mean FO was lower in Perthes hips (34.2 mm vs. 39.7 mm, <i>p</i> < 0.001), as was hip abduction (25.5° vs. 29.7°). ATD and FO were significantly associated with the modified Stulberg classification, particularly between Stulberg 1 and Stulberg 3 hips (<i>p</i> < 0.001). No significant associations were found between ATD, FO, and hip function parameters, nor between HGT and HAGOS scores in spherical hips. Reduced ATD and FO were prevalent in young adults with previous PD and were associated with the modified Stulberg classification but not with hip function. ClinicalTrials.gov (NCT03995960).