Histological observations on muscles from cases with aplasia of the tibia.

Muscles of the lower leg and foot from 3 cases with aplasia of the tibia were investigated by light microscopy. The crural muscles are atrophied in all cases, whereas the small muscles of the foot are quite normal. The histological appearance of the degenerated muscles is characterized by atrophied muscle fibers and fatty infiltration. There are no signs of hypertrophy or regeneration. These observations suggest that the atrophy is caused selectively by inactivity of the crural muscles.