Gastrocnemius muscle belly and tendon length in stroke patients and able-bodied persons.

Length changes of gastrocnemius muscle belly and tendon at different passive tensions and ranges of motion (ROM) were measured in 31 healthy persons and 15 hemiplegic patients with clinically demonstrated ankle joint plantar flexion (PF) contractures. Preliminary studies were done to obtain accurate determination of gastrocnemius muscle insertion and origin points on x-ray films, to calculate the magnification factor due to x-ray beam divergence and to measure the length changes in muscle belly by the use of a wire hook placed at the muscle-tendon junction. Our results revealed: (1) change in length at different passive tensions is in the muscle belly, not in the tendon, (2) in hemiplegic patients no statistical difference in elongational characteristics of affected gastrocnemius muscle bellies with clinically demonstrated ankle PF contractures and of the contralateral nonaffected muscle bellies, (3) spastic and flaccid gastrocnemius muscle bellies are not statistically different in respect to passive elongations, (4) gastrocnemius muscle bellies of both affected and nonaffected legs of hemiplegic patients were statistically different from the muscle bellies of healthy persons in regard to maximal ROM and maxinum muscle belly length changes, (5) there was approximately .5 mm change in the belly length for each degree of ankle ROM, (6) age is not a factor influencing passive elongation of muscle belly, (7) average muscle belly lengths were consistently shorter in hemiplegic muscles while their tendon lengths did not change. The enumerated findings suggest that the limitation of ankle ROM in spastic hemiplegic legs obtained by the standard clinical measurements technique represents a change in muscle belly rest length without a structural contracture of the muscle fibers.