HAMSTRINGS AND PSOAS LENGTHS DURING NORMAL AND CROUCH GAIT - IMPLICATIONS FOR MUSCLE-TENDON SURGERY

Crouch gait, one of the most common movement abnormalities among child ren with cerebral palsy, is characterized by persistent flexion of the knee during the stance phase. Short hamstrings are thought to be the cause of crouch gait; thus, crouch gait is often treated by surgical l engthening of the hamstrings. In this study, a graphics-based model of the lower extremity was used in conjunction with three-dimensional ki nematic data obtained from gait analysis to estimate the lengths of th e hamstrings and psoas muscles during normal and crouch gaits. Only th ree of 14 subjects with crouch gait (our of 20 limbs with knee flexion of 20 degrees or more throughout stance) had hamstrings that were sho rter than normal by more than 1 SD during walking. Most (80%) of the s ubjects with crouch gait had hamstrings of normal length or longer, de spite persistent knee flexion during stance. This occurred because the excessive knee flexion was typically accompanied by excessive hip fle xion throughout the gait cycle. All of the subjects with crouch gait h ad a psoas that was shorter than normal by more than 1 SD during walki ng. These results emphasize the need to consider the geometry and kine matics of multiple joints before performing surgical procedures aimed at correcting crouch gait.