Sl. Delp et al., HAMSTRINGS AND PSOAS LENGTHS DURING NORMAL AND CROUCH GAIT - IMPLICATIONS FOR MUSCLE-TENDON SURGERY, Journal of orthopaedic research, 14(1), 1996, pp. 144-151
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.