No dose response effect in shockwave therapy applied to bone conditions: a systematic review, meta-analysis and meta-regression

Shock waves have been widely used to treat bone conditions, but despite the articles and meta-analyses, there are still doubts about its effectiveness, with a meta-analysis pointing to uncertain evidence of positive effects for pain and delayed or non-union, while others point to a positive effect on the same outcomes. One hypothesis for this conflict in the results is the lack of research on the relationship between the applied dose and clinical outcomes. Identify the effect of the dose applied in shockwave therapy on clinical results in bone conditions by meta-regression of controlled trials. Our search was conducted on PubMed (MEDLINE), EMBASE, Cochrane, Web of Science and Scopus in November 2022. The results of 3, 6, 12 and 24 months, post treatment of shockwave therapy of long bone fractures, osteonecrosis of femoral head and bone marrow edema were analyzed for pain, functional scores, size of lesion and non-union with meta-analysis and meta-regressions were conducted with the clinical results and the parameters of the quantity of pulses and energy flux density (EFD). 3641 studies were retrieved and after the selection process eight of them were included for analyses. Shockwave therapy applied at the moment of surgery led to significant lower raw mean difference (RMD) pain scores at six months (RMD: -1.53[-2.58; -0.48], p=0.004) and at 3 and 12 months. Better functional standard mean difference (SMD) scores were found at six months (SMD: 0.83[0.32; 1.33], p<0.001) and at 3 and 24 months. A reduction in the size of lesion for the osteonecrosis of the femoral head was found at 12 months (RMD: -19.01[-35.63; -2.39], p=0.02). The meta-regression analyses showed no association between EFD (R2=0.00; p=0.42), or the number of pulses (R2=0.00; p=0.36) with pain scores; or EFD (R2=0.00; p=0.75), and the number of pulses (R2=0.00; p=0.65) with functional values. The results point that shockwave therapy had positive effects in pain and functional scores at different time points after bone fractures or osteonecrosis of the femoral head, however, neither the quantity of pulses or the energy flux density showed any relationship with these positive outcomes.