Treatment of experimental avascular necrosis of the femoral head with hyperbaric oxygen in rats: histological evaluation of the femoral heads during the early phase of the reparative process.

The healing of vascular deprivation-induced necrosis of the femoral head of rats exposed to hyperbaric oxygen was compared with that in untreated rats. The amount of necrotic bone, extent of osteoneogenesis, degree of remodeling, and changes of the articular cartilage were histologically graded on a semiquantitative scale of 0 to 3+. On the 2nd, 7th, and 21st postoperative days, there were no differences between the two groups. Newly formed appositional and intramembranous bone was more abundant and remodeling was more advanced in the femoral heads of the hyperbaric oxygen-treated than untreated rats sacrificed on the 42nd postoperative day; also there was less necrotic debris in the femoral heads of the treated rats. There were no differences in the severity of the degenerative changes of the articular cartilage of the treated and untreated rats. Exposure of rats to hyperbaric oxygen does not preserve tissue viability after all arteries supplying the femoral head are severed. Yet, resulting in an increased oxygen tension of the tissues, it seems to provide the optimal settings for reparative processes. The results suggest that hyperoxygenation-mediated relief of ischemia enhances the fibroblastic, angioblastic, osteoblastic, and osteoclastic activities such that healing of the rats' necrotic femoral heads is expedited. Copyright 1999 Academic Press.