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The effectiveness of conservative management for disabled throwing shoulder in baseball: a systematic review of Japanese-language primary studies

Background: Conservative management is often the first-choice treatment for baseball players with disabled throwing shoulder (DTS). Considering the high popularity of baseball in Japan, we suspected that there might be some evidence regarding this topic in the Japanese-language literature. Objective: This study aimed to systematically review Japanese-language primary studies investigating the effectiveness of conservative management for DTS in baseball. Methods: Eight databases were systematically searched from inception to 7 April 2016. Data on authors, publication years, sample characteristics, types of interventions, outcome measures and results were extracted. Data were synthesised qualitatively. Results: Seven studies with low evidence level and low-to-moderate study quality were included. Interventions examined in the included studies were downward throwing, combined physiotherapy interventions and joint distension. Forming correction, stretching for posterior shoulder muscles and strengthening exercises to improve scapular/trunk stability were commonly used in combined physiotherapy interventions. Downward throwing and combined physiotherapy interventions corresponded with expert opinions described in the English-language literature. Due to the lack of studies with high level of evidence, however, it was difficult to determine the genuine effects of these interventions. Conclusion: Our systematic review found limited evidence about the effectiveness of any conservative management for baseball players with DTS. Although downward throwing and combined physiotherapy interventions might be appropriate management in some cases, further studies of higher level of evidence and greater methodological rigour are required.