Bony ingrowth induced by treadmill exercise in rats with femoral shaft bone defects

Zhang Jie; Zhang Wen; Chen Xi; Luo Zong-ping; Yang Hui-lin

doi:10.3969/j.issn.2095-4344.2014.15.005

Abstract：BACKGROUND:It is wel-known that mechanical stimulation could promote fracture healing. However, what kind of mechanical stimulation induced by treadmil exercise can increase the bone conductibility of bone material and promote the healing of bone defect is stil unclear. <br> OBJECTIVE:To evaluate the influence of indirect mechanical stimulation produced by treadmil exercise on bone defect healing and osteogenesis of bone materials. <br> METHODS:Sprague-Dawley rats at 12 weeks old were used in this study to establish a bone defect of 3 mm in diameter and height at the left distal femur. Afterwards, calcium sulphate scaffolds were implanted into the defects. The rats were divided into treadmil exercise group and control group. Treadmil exercise was began at 1 week postoperatively, 10 m/min, 45 minutes per day, 5 days per week, for 3 weeks. Control group did not receive any exercise. Micro-computed tomography was used to determine bone formation in the bone defects at 1, 2, 3, and 4 weeks after surgery. The sections of left distal femur were subject to hematoxylin-eosin staining, the new bone formation and degradation of bone materials in the bone defects were observed. <br> RESULTS AND CONCLUSION:Micro-CT analysis showed that, a smal amount of new bone formed in both treadmil exercise group and control group at 1 week after surgery. In treadmil exercise group, new bone formation was significantly higher than the control group at 2, 3, 4 weeks (P<0.05). At 4 weeks, histological results also confirmed the difference of new bone formation in bone defect between treadmil exercise group and control group. In addition, bone mineral density of treadmil exercise group was higher than that of control group at 2, 3, 4 weeks, but no significant difference was found (P>0.05). The results suggest that moderate treadmil exercise could promote bone defect healing and enhance osteoconductivity of bone substitute.