Out-toeing and in-toeing in patients with Perthes disease: role of the femoral hump.

BACKGROUND Some patients with Perthes disease develop abnormal gait in the transverse plane, that is, out-toeing or in-toeing. Considering that this phenomenon occurs mainly in patients who presented late without previous treatment or failed in the containment treatment, we postulated that the deformed femoral head and its impingement to the acetabulum may play an important role in the pathomechanism of this abnormal gait. METHODS Three-dimensional computed tomography (CT) and gait analysis were performed for 9 patients with late-presenting unilateral Perthes disease, who recently developed out-toeing (n = 5) or in-toeing (n = 4) gaits without torsional problems or foot deformities. Deformity of the femoral head was investigated, with special attention to the location and size of the femoral "hump." Kinematic gait data were used to analyze the difference in the impinging pattern of the hip joint between the 2 opposite groups of patients. The gait parameters evaluated were foot progression angle, hip rotation, and pelvis rotation in the transverse plane; hip flexion and extension in the sagittal plane; hip adduction and abduction in the coronal plane. RESULTS In the 5 out-toeing patients, all affected hips had anteriorly deviated femoral hump, and they were externally rotated in the CT gantry with the hump facing the anterolateral part of the hip joint. On the other hand, all affected hips of the 4 in-toeing patients had laterally deviated hump, and they were internally rotated in the CT gantry with the hump facing the anterolateral part of the hip joint. Gait analysis showed abnormal hip rotation and compensatory pelvis rotation. Maximal flexion was decreased in all out-toeing hips. Unintentional adduction was observed in all in-toeing hips. CONCLUSIONS The results suggest that out-toeing and in-toeing gaits are apparently caused by the compensatory rotation of the proximal femur to avoid impingement by placing the femoral hump to the relatively deficient anterolateral part of the hip joint.