Functional Adaptation of Bone in Response to Sinusoidally Varying Controlled Compressive Loading of the Ovine Metacarpus

To obtain carried load, quantitative data relating functional adaptation of bone to controlled, sinusoidally-varying, compressive loading of constant amplitude was applied to the right metacarpal bones via Steinmann's pins inserted through the metaphyses in 13 sheep. Loading was applied for two 1-hr periods/day at 24 cycle/minute, through-out a test period of 28 days. The amplitude of the applied loading was varied from test to test, giving peak stresses on the mid-diaphyseal cross-section that ranged from 2.2-8.3 N/mm2. In the mid-diaphyseal region, the bone responded by periosteal apposition, with maximum proliferation usually occurring on the medio- and laterovolar borders and relatively little new bone on the dorsal and volar aspects. The cross-sectional areas of new bone was roughly proportional to the applied stress, with a maximum increase of approximately 8% in the most highly stressed bones. There was also evidence that periosteal resorption had occurred, presumably as the first step in the apposition process. A significantly increased level of intracortical activity was found in the right metacarpus as compared with the contralateral bone.