Functional changes in the antagonists after lengthening the agonists in cerebral palsy. II. Quadriceps strength before and after distal hamstring lengthening.

In a recent study, 38 patients with spastic cerebral palsy (median age, 5.6 years) were examined before and at a median 13 months after distal lengthening of the hamstrings. Four weeks after operation, the strength of the quadriceps was reduced by a median value of 70%. Seven months after operation, the strength had been regained; by 13 months after operation, it had increased by a median value of 22%. In 20 cases, strength had increased by more than 50%. The present study confirms the theory that quadriceps function is strengthened when the antagonist function is weakened. The study also explains (1) why it often takes six months for gait to become better than before operation and (2) why spasticity of the rectus often increases after the hamstrings are lengthened.