No abstract

In 48 rabbits the bone-formation rates and strength in the tibial shaft, osteotomized and treated with rigid internal plate fixation, were compared with contralateral bones, which were treated with plate fixation without osteotomy. The plate fixation alone induced a 35 percent decrease in torsional strength after 12 weeks. The healing of the osteotomy counteracted the decrease in strength induced by stress protection of the rigid plate at 6 weeks, but this effect subsided within 12 weeks. The osteotomy also induced a 2-3-fold increase in the synthesis of bone matrix and mineral accretion of the bone underlying the plate at 6 and 9 weeks when compared with the contralateral side, which was plated but not osteotomized. The bone-formation levels returned to normal within 12 weeks; and the bone underlying the plate became subject to atrophy, resulting in decreased mechanical strength.

No abstract

We studied the effect of human recombinant growth hormone on diaphyseal bone in 40 adult rabbits. The diaphyseal periosteum of one femur in each animal was mechanically stimulated by a nylon cerclage band. The bands induced an increase in bone formation, bone mineral content, and maximum torque capacity of the diaphyseal bone at 1 and 2 months. Growth hormone enhanced the anabolic effect of the cerclage bands on bone metabolism, evidenced by a further increase in torsional strength of the femurs.

Both humeri of seven professional tennis players and seven controls were examined with x-ray spectrophotometry, and computed tomography. Both the bone mineral content and the cortical cross-sectional area were found to be larger in the dominant arm of the tennis players than in their non-dominant arm, and in comparison to both arms of the controls. The increase in cortical cross-sectional area was a result of an increased outer diameter of the diaphysis.