Osteoporosis Influences the Early Period of the Healing After Distraction Osteogenesis in a Rat Osteoporotic Model

Introduction: Despite the clinical adoption of distraction osteogenesis (DO), studies examining the bone healing process at the distraction gap in osteoporotic bone are limited. We examined the effect of osteoporosis in the ovariectomized rat on DO.

Material And Methods: Mid-diaphyseal osteotomies were performed on the femurs of ovariectomized (OVX) rats. External distractors were placed on these rats and also on sham-ovariectomized rats. After a 7-day latency period, distraction was carried out at a rate of 0.5mm/day for 10 days. The bone volume (BV) of the distraction gap was measured by Micro-focused X-ray computed tomography (micro-CT) at 0, 2, and 4 weeks after completion of the distraction, and the distraction gap was examined histologically.

Results: The BV of the distraction gap in the OVX group was significantly lower than that in the sham group at 2 and 4 weeks after completion of distraction (p<0.01). On histological examination, the distraction gap in the OVX group was filled with scattered smaller bone trabeculae than those seen in the sham group at 4 weeks after completion of distraction. Osteoclast numbers at the distraction gap in the OVX group were significantly increased when compared to the sham group (p<0.01).

Conclusion: Bone turnover with osteoclast predominance in ovariectomized rats is likely to be the cause of a reduction in new bone formation at the distraction gap.