The effects of osteoporosis on distraction osteogenesis: an experimental study in an ovariectomised rabbit model.

The effects of oestrogen deficiency-associated osteoporosis on callus distraction were investigated in rabbits. Twenty-four female New Zealand rabbits 5 to 6 months old were used. Ovariectomy was performed on 12 rabbits, which composed the osteoporotic model group. Six weeks later, osteotomy was carried out and Ilizarov external fixators were applied to the right proximal tibial metaphyses in both the osteoporotic model group and the control group. Beginning one week postosteotomy, the metaphyses were distracted 0.35 mm twice daily for 3 weeks, and the average length increase obtained for both groups was 17.2 mm (minimum: 16.8, maximum: 19 mm). Following a postdistraction waiting period of 6 weeks for newbone formation, the subjects were sacrified and specimens were examined histopathologically. Radiography was carried out at one-week intervals during the distraction period and at 2-week intervals during the waiting period, and scintigraphy was performed at the end of each period. On histopathologic examination, a significant difference in callus remodeling was observed between the control and osteoporotic model groups. On radiologic evaluation it was observed that, while both groups had inadequate callus tissue at the end of the waiting period, callus formation and remodeling occurred later in the model group than in the control group, and the new bone was more osteoporotic. Osteoporosis associated with estrogen deficiency adversely affects the outcome of callus distraction. Nonetheless, radiographic findings in rabbits indicate that the effects may not be so great as to preclude clinical procedures. It was concluded that these results should be supported with clinical studies.