Excessive hip flexion during gait in patients with static encephalopathy: an examination of contributing factors.

BACKGROUND Excessive hip flexion in gait is thought to be associated with hip flexion contracture, but has also been associated with excessive anterior pelvic tilt, knee flexion, internal hip rotation, and muscular factors. The purpose of this study was to examine the contributors to excessive hip flexion during gait in children with cerebral palsy, with and without hip flexion contractures. METHODS A retrospective chart review was conducted of 155 children with cerebral palsy. Potential contributors to excessive hip flexion in stance were evaluated, including static and dynamic range of motion, strength measurements, and patient factors including age, previous surgery, distribution of involvement (hemiplegia, diplegia, and quadriplegia), and Gross Motor Function Classification System level. Univariate analysis was performed using simple linear regression and analysis of variance, with appropriate post-hoc tests. All variables were then included in a stepwise linear regression using forward selection. RESULTS Univariate analysis demonstrated a significant relationship (P<0.05) between excessive hip flexion in stance and all predictive variables except static dorsiflexion range of motion with the knee flexed and maximum dorsiflexion in stance. Results of stepwise regression revealed that 3 variables accounted for 65% of the variance: passive hip extension range of motion, average pelvic tilt during the gait cycle, and knee extension achieved in the stance phase of gait. Twenty-two of 45 (49%) exhibiting hip flexion contractures of greater than 10 degrees did not exhibit excessive hip flexion in stance phase. CONCLUSIONS Hip extension in stance in children with static encephalopathy depends primarily on hip extension passive range of motion, the amount of pelvic tilt, and knee extension in stance phase. These 3 variables account for 65% of variance in these 155 patients, whereas other factors (age, dorsiflexion in stance, and hamstring range) each account for only 2% to 3% of the variance. Careful clinical examination, including computerized gait analysis when available, is recommended before surgical intervention to determine whether excessive hip flexion is a primary or compensatory deviation. LEVEL OF EVIDENCE Level IV, case series.