Slipped capital femoral epiphysis, fixation by single screw in situ: A kinematic and radiographic study.

BACKGROUND Slipped capital femoral epiphysis is known to produce characteristic deformities in the proximal femur, which affect hip motion and may cause a limp. This paper assessed the 3D gait kinematics in adolescents after single screw fixation of moderate to severe, stable, unilateral slipped capital femoral epiphysis. Our goals were to characterize the 3D kinematic patterns and to investigate the correlation between the severity of radiological deformity and severity of gait disturbance. METHODS This was a retrospective study of patients seen at our institution between 2000 and 2009. Antero-posterior and frog lateral X-rays were reviewed to measure: Southwick's lateral slip angle, the alpha angle of Notzli and Klein's line offset. Quantitative 3D gait data was collected using a state of the art motion capture system. Kinematic waveforms were compared using a functional data analysis version of the t-test. FINDINGS There were 30 patients with an average age at pinning of 13y (10-17y). Mean gait profile scores were significantly abnormal for slipped side (10.8°) versus sound side (6.8°), slipped side versus normal (5.6°) and sound side versus normal. There was little statistically significant correlation between severity of radiographic deformity and degree of gait disturbance. INTERPRETATION Major kinematic pattern deviations could be associated with (a) morphology of the proximal femur and potential femoral acetabular impingement problems and (b) leg length discrepancy. Gait analysis was able to quantify the kinematic deviations due to the anatomical deformities.