The Effects Of Unfocused High Energy Shock Waves On The Healing Of Osteoporotic Fracture, Bone-microarchitecture And Biomechanical Property In Rat

Objective To investigate the influence of the unfocused high energy shock waves on the healing process, bone microstructure and biomechanical properties of osteoporotic fractures in rat.Methods Ninety female SD rats of14-week-old randomly were selected six for Sham operation, and the others were underwent ovariectomy (OVX) to establish the osteoportic models. After these models were confirmed, we made the left limb (the study side) open fractures and fixed with Kirschner wires. Then,the rats were randomly divided into treatment group and control group.After a week,the treatment group were dealled with unfocused high energy shock wave while the control group were not processed conventionally.Then, X-ray study were tested on sometimes..Callus samples were taken for HE and immunohistochemical staining to observe the callus histological changes, detect callus of BMP-2, VEGF expression, change and distribution in different stages (2,4and8weeks). Then we detected the expression of CTX-I and PINP in serum at different stages (2,4and8weeks) with enzyme-linked immunosorbent assay Micro-CT and three-point bending test were used to compare the two groups at4and8weeks.Results Compared to the control group,OVX+SW group which achieved bone healing after6weeks of treatment was significantly more,while all rats of these two groups completed bone healing at8th week on X-ray film.2Histological observation showed that the formation of bone trabeculae of control group at2weeks were less than treatment group,while treatment group expressed stronger inflammatory response than the control group at the time;at Four weeks, the treatment group had more mature trabecular bone than the control group, and there were more cartilage bone callus gradually replaced by bone callus.at8weeks bone trabecular of treatment group basic rebuilded completely, while the rebuilding and calcification of trabecular bone of the control group were not complete.3Immunohistochemical observation showed in two weeks and four weeks, BMP-2and VEGF expressed positively in both groups, while in the treatment group they both expressed better than the control group.compared with the control group, at two weeks Collagen and osteoblasts were much more in the treatment group, while more active osteogenesis in the treatment group; on4weeks the treatment group osteoblast were active, and significantly more bone were formation; at8weeks in treatment group trabecular bone were beginning to mould to the lamellar bone while fibrous callus were disappear, The control group occasionally experssed BMP-2in osteoblast; while VEGF positive staining only in osteoclasts.5Biochemical indicators of bone metabolism.No significantly differences existed between the groups of PINP in the OVX+SW group and OVX+Control group at each time point.however, the CTX-I in two weeks after treatment (0.62±0.23ng/ml),4weeks (1.26±0.39ng/ml),8weeks (0.45±0.36ng/ml) compared with the OVX+Control group (0.52±0.16ng/ml)(p=0.417),(1.78±0.34ng/ml)(p=0.035),(1.21±0.48ng/ml)(p=0.011) which showed the difference between the groups at four weeks and eight weeks.6the micro-CT analysis showed that bone mineral density (Density of TV),the relative bone volume (BV/TV),trabecular thickness (Tb. Th) trabecular number (Tb.N)in OVX+SW group are significantly higher than in OVX+Sham group both at4weeks and8weeks; Three point bending test results showed that the maximum load of fracture fragment in treatment group were significantly better than the control group both at4weeks and8weeks (P<0.05)Conclusion1Unfocused high energy shock waves may through increasing the expression of BMP-2, VEGF to promote bone formation to improve the blood supply of fracture to accelerate the bone healing process;2Unfocused high energy shock waves may have some inhibitory effect on bone resorption;3Unfocused high energy shock waves can improve bone microstructure, increase bone density and improve bone mechanical properties. Thus, unfocused high energy shock waves may become a non-invasive treatment of osteoporosis and osteoporotic fractures.