Hip range of motion in Perthes’ disease: comparison of pre-operative and intra-operative values

Background Children with early Perthes’ disease and clinical loss of motion are commonly noted to have normal or almost normal hip range of motion (ROM) when examined under anesthesia (EUA). Despite anecdotal comments about this observation, no series has documented these findings. The lack of such data led to this study. Methods Consecutive patients with unilateral Herring class B or C Perthes’ disease in mid to late Waldenstrom’s fragmentation stages who failed a non-operative course of hip motion restoration had hip range of motion (ROM) documented pre-operatively and intra-operatively by a single, experienced pediatric orthopedic surgeon. The opposite normal hip’s ROM was used as the control. Joint congruity was assessed arthrographically. Results Twenty-seven patients, 6–10 years old (average 7.9 years) with early Perthes’ disease were reviewed. Twenty-one of 27 patients (77.7%) had full or almost full hip ROM of the involved side when examined under anesthesia (EUA). Six patients (22.3%) had limited abduction (<50 degrees) and underwent an adductor tenotomy that normalized hip ROM. Five of these six patients were older than 8 years. Intra-operative arthrography did not demonstrate lack of containment, hinge abduction or joint incongruity. Conclusions Loss of hip ROM in this series of patients with early Perthes’ disease without intra-articular incongruity was due to pain and muscle spasm which were obviated by anesthesia, demonstrating essentially normal hip ROM in the majority of patients. Pre-operative bed rest and traction was not required to restore ROM in this group of patients.