or The Use of Extracorporeal Shock Wave Therapy to Improve Fracture Healing

http://www.ortho.hyperguides.com/index.php?option=com_content&view=article&id=1934

David J. Hak, MD, MBA
Denver Health
University of Colorado
Denver, CO

Introduction
Extracorporeal shock wave therapy (ESWT) is commonly used in the treatment of urolithiasis (kidney stones). Extracorporeal shock waves are single, high-amplitude sound waves generated by either electrohydraulic, electromagnetic, or piezoelectric methods that propagate in tissue, leading to a sudden rise of ambient pressure and maximum pressure at the wave front, followed by lower tensile amplitude.¹ Initial animal experiments in the early 1990's examined the effect of shock wave energy on bone and fracture healing. Positive basic science findings have lead to subsequent human clinical trials.

Mechanism of Action
Two major mechanisms, membrane hyperpolarization, and the formation of oxygen free radicals, have been proposed to explain how the mechanical shock wave energy is translated into its biological effects.

In a rabbit fracture model, ESWT treatment has been shown to increase vascular endothelial growth factor (VEGF), endothelial nitric oxide synthase, proliferating cell nuclear antigen, and bone morphogenetic protein 2 (BMP-2).² Other animal fracture studies have shown that ESWT treatment produces increased callus formation, decreased healing time, and increased mechanical strength of the healed fractures.^3,4

Human clinical studies
Zelle et al reported a review of 10 studies investigating shock wave therapy in the treatment of fractures and delayed unions and/or nonunions.¹ The overall union rate was 76% in the 924 patients reviewed (95% confidence interval 73%-79%). The union rate was significantly higher in hypertrophic nonunions than in atrophic nonunions.
Wang et al performed a prospective, randomized study of 56 patients with 59 acute high-energy fractures.⁵ All patients underwent open reduction and internal fixation (ORIF) with intermedullary (IM) nailing and plate fixation; patients in the active arm of the study received additional shockwave therapy following surgery while patients in the control group did not. There were 40 femur fractures (19 in the shock wave group and 21 in the control group) and 19 tibia fractures (9 in the shock wave group and 10 in the control group). Patients were evaluated at 3, 6 and, 12 months with clinical assessments of pain score, weight bearing status, and radiographs. The primary endpoint was the rate of nonunion at 12 months and the secondary end point was the rate of fracture healing at 3, 6 and, 12 months.

At 12 months, the rate of nonunion was 11% in the group treated with shock wave compared with 20% in the control group (P < 0.001). Also, the rate of fracture healing was significantly better in the shock wave treatment group compared with the control group at 3, 6, and 12 months (P < 0.001).

Cacchio et al reported on a prospective, randomized, multicenter study of 126 patients with long-bone nonunions.⁶ The study included patients with hypertrophic nonunions (n = 92) and atrophic nonunions (n = 34). Patients were randomized to one of three groups. Groups 1 and 2 both received four shock wave treatments; group 1 receiving an energy flux density of 0.40 mJ/mm² and group 2 received an energy flux density of 0.70 mJ/mm2. The four shock wave treatments were administered at weekly intervals and performed under regional anesthesia. The third group of patients was randomized to surgical treatment. The location of nonunions included in this study were femurs (n = 34), tibias (n = 67), humerus (n = 15), and radius/ulna (n = 10).

The authors reported that extracorporeal shock wave therapy was as effective as surgery in stimulating union in long bone hypertrophic nonunions. At 6 months the percentage of patients that had healed in each group was 70% in group 1 and 71% in group 2, compared with 73% in the surgically treated patients in group 3. Early clinical outcomes at 3 and 6 months were better in the shock wave treated groups, but at 12 and 24 months there were no differences in the clinical outcomes, except for the DASH scores.

Summary
Extracorporeal shock wave therapy appears to be a promising adjunct in the management of patients with nonunions. The current level of evidence is rated as poor because of the absence of high quality prospective randomized studies. Further investigation with large- scale, well-designed, prospective, randomized clinical studies is warranted to better determine the effectiveness and optimal indication for the use of extracorporeal shock wave therapy in patients with nonunions and acute fractures.

References