Interrelationships of strength and gait before and after hamstrings lengthening.

Muscle-tendon lengthenings are an essential part of the orthopaedic management of static and dynamic joint contractures associated with cerebral palsy. Although these procedures typically have a positive biomechanical effect on joint alignment, the potential negative effects of alterations in tendon length on muscle strength and gait function have not been well documented in these patients, in whom muscle weakness is a prevalent clinical symptom. The purpose of this study was to examine the change in strength values of the hamstring and quadriceps muscle groups during a 9-month postoperative period in patients who had undergone hamstring tendon lengthenings, in comparison to an operative "no hamstring surgery" control group, and to relate baseline strength and postoperative changes to gait function in these patients. Results for the "hamstring surgery" group indicated that although hamstring strength declined initially, the strength increased with time and was similar to preoperative values by 9 months. Quadriceps strength measured at 30 degrees of knee flexion increased significantly during the recovery period as a direct result of improvements in knee extension. Although hamstring surgery produced an immediate effect on passive motion and knee-joint alignment, functional improvement, as evidenced by increased stride length, was not evident until strength values approximated or exceeded preoperative values.