Extracorporeal Shockwave Therapy as an Adjunctive Therapy for Frozen Shoulder: A Systematic Review and Meta-analysis

Background: The best nonsurgical treatment for frozen shoulder is still unclear. Extracorporeal shockwave therapy (ESWT) is an innovative adjunctive treatment for frozen shoulder, but its effect is still unclear. Purpose: To evaluate the published literature regarding the potential of ESWT as an adjunctive therapy for frozen shoulder. Study Design: Systematic review; Level of evidence, 1. Methods: Searches were conducted in the PubMed, EMBASE, Cochrane Library, China National Knowledge Infrastructure (CNKI), and VIP Information databases for relevant studies between inception and November 2020. Included were randomized controlled trials (RCTs) for frozen shoulder that compared ESWT with routine treatments to controls. There were no restrictions on the treatment period, type of ESWT, or severity of symptoms. At least 1 of the following outcome indices was assessed: visual analog scale (VAS) for pain, Constant-Murley score (CMS) for shoulder function assessment, or external rotation range of movement (ER ROM). RevMan 5.3 software was used to evaluate the bias and quality of the included studies. For continuous variables, the mean difference (MD) or standardized MD (SMD) with the 95% CI was extracted. For dichotomous data, event ratios and sample sizes were extracted. Results: Overall, 20 studies were included. The ESWT used as an adjunct to other interventions had better outcomes compared with control groups regarding immediate and short-term analgesic effects (immediate: MD, –1.10 [95% CI, –1.27 to –0.92], P < .00001; short-term: MD, –0.72 [95% CI, –0.94 to –0.50], P < .00001) as well as immediate function (SMD, 1.54 [95% CI, 1.19 to 1.89], P < .00001], I 2 = 0%). There was significant heterogeneity between studies for long-term analgesia (MD, –0.90 [95% CI, –1.40 to –0.41], P < .00001, I 2 = 89%) and ER ROM (MD, 10.31 [95% CI, 3.46 to 17.17], P < .003, I 2 = 93%). Conclusion: ESWT seems to be beneficial to patients with frozen shoulder by alleviating pain and improving function. ESWT could be used as an adjunct therapy to routine treatments, although the quality of the included RCTs was hampered by significant heterogeneity regarding long-term analgesia and joint ROM.