Reduction in thigh muscle cross-sectional area and strength in a 4-year follow-up in late polio

Objective: To study changes in cross-sectional thigh muscle area and muscle strength in late polio subjects over a 4-year period. Design: Longitudinal study of a cohort of polio survivors, comparing subjects who acknowledge (unstable) with those who do not acknowledge (stable) new muscle weakness. Setting: University hospital. Subject: Eighteen subjects (6 men, 12 women) with polio-myelitis sequelae (39 to 46 years of age) were studied on two occasions rt years apart; the first examination was 37 to 14 years after onset of polio. Subjects were recruited through hospital registers, newspaper advertisement, and a patient organization. Outcome Measurements: Thigh muscle and intermuscular and intramuscular adipose tissue (AT) cross-sectional areas were measured by computed tomography. Isometric muscle strength for knee extension and flexion was measured using a Kin-Com dynamometer. Results: Cross-sectional muscle area decreased on average 1.3 +/- 3.6cm(2) (1.4%, p <.05): the intermuscular and intramuscular AT area increased 1.8 +/- 3.4cm(2) (12.1%, p <.05). When divided by legs in which subjects reported (unstable) or did not report (stable) Increased muscle weakness, unstable legs showed significant reduction (p <.05) in muscle area, whereas stable legs did not. Estimated total thigh muscle strength decreased 7.8% +/- 2.9% (p <.01), with a significant (p <.001) reduction in unstable legs (13.4% +/- 4.3%) but not in stable legs. The reduction in strength appears to be greater than the reduction in cross-sectional muscle area, but there is still a significant correlation (r-=.44, p<.05). Conclusion: The present results demonstrate not only progress of muscle weakness, but also of muscle atrophy in postpolio subjects. (C) 1996 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation