Enhancing mechanical strength during early fracture healing via shockwave treatment: an animal study

Objective. This investigation aims to determine (1) whether shockwave treatment helps fracture healing and (2) whether the effect of shockwave treatment on fracture healing is dose dependent. Design. Shockwave was applied over tibial osteotomy in an animal model to assess its effect on the healing of the fracture. Methodology. Bilateral tibial diaphyseal transverse osteotomy was conducted on 42 rabbits, dividing into experimental and control group, immobilized using an external skeletal fixator, with one leg tested with shockwave therapy and the contralateral leg acting as the control without therapy. Serial radiography and measurement of bone mineral density via dual-energy X-ray absorptiometry were performed to assess the fracture healing. The experimental animals had two or three sessions of shockwave therapy (5000 impulses, 0.32 mJ/mm(2), Orthopedic(TM)) over the osteotomy sites on day 7, 21 and 35; while the control group did not receive any treatment. The animals were sacrificed on day 42 or 56. Then, bilateral tibias were harvested and sent for mechanical tests as well as the histological examination. The pertinent statistic methods were applied to analyze the results. Background. Shockwave therapy has become a useful alternative approach in treating various orthopedic conditions, but the mechanism which it works remains unclear. Thus far, shockwave therapy has been found effective in treating long bone pseudoarthrosis, but whether it can benefit fresh fracture healing continues to be debated. Results. Higher union rates occurred during the early but not the late stages in the experimental group, while mechanical strength was higher in the experimental group than in the control group. No significant dose-dependent response occurred between the second and third applications of shockwave treatment. No significant difference in mechanical strength occurred between the experimental groups at 4 weeks and the control group at 6 weeks, or between the experimental groups at 6 and 8 weeks. Furthermore, no significant correlation occurred between the absolute values of maximum torque and bone mineral density. Conclusion. Based on this investigation, shockwave treatment has a positive effect on early fracture healing while its long term effects require further investigation.