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Keywords:

  • Metatarsals;
  • Robusticity;
  • Surgery;
  • Experiment

Abstract

When a marginal metatarsal (M1 or M5) is amputated in neonatal rats, robusticity increases in all other metatarsals in both sexes. The robusticity increase is greatest in the metatarsal adjacent to the operation and declines in the direction away from it. The tripod structure of the rat's foot with its maximum robusticity of the marginal metatarsals is retained. When both marginal metatarsals are removed, this tripod arrangement is less clearly retained. When robusticity of all remaining metatarsals is averaged in a total robusticity quotient, total robusticity increase is greater in M1 than in M5 removal and greatest when both are removed. Total increase is greater in females than in males.

Metatarsal robusticity increases result from retardation of longitudinal growth and increase of weight. The fact that some robusticity increases coincide with lesser length but not with increased weight suggests that in the process of robusticity increase longitudinal growth retardation precedes that of weight increase.

Lesser length and greater weight of a long bone occurs also when hypofunction is produced in neonatal rats. However, in hypofunction the thickness of the compacta is increased leading to an obliteration of the medullary canal, while in the experimental metatarsals of this study, submitted to greater weight-bearing stresses, this canal is never reduced or obliterated.