Shoulder Range of Motion and Baseball Arm Injuries: A Systematic Review and Meta-Analysis.

OBJECTIVE: Arm injuries in baseball players are a common problem. The identification of modifiable risk factors, including range of motion (ROM), is essential for injury prevention. The purpose of this review was to assess the methodologic quality and level of evidence in the literature and to investigate the relationship between shoulder ROM and the risk of arm injuries in baseball players.

DATA SOURCES: Relevant studies in PubMed, CINAHL, Embase, and SPORTDiscus published from inception to August 1, 2017.

STUDY SELECTION: Only studies that encompassed healthy baseball cohorts who were assessed for shoulder ROM and prospectively evaluated for injuries throughout a baseball season or seasons were included.

DATA EXTRACTION: Six articles met the search criteria. Only 3 studies were included in the meta-analysis due to disparate participant groups.

DATA SYNTHESIS: The modified Downs and Black scale (0-15 points) was used to analyze methodologic quality. Study quality ranged from 11 to 14. Four studies received high-quality (≥12) and 2 studies received moderate-quality (≥10) scores. The overall pooled analysis demonstrated that absolute and internal-rotation deficits (-5.93 [95% confidence interval {CI} = -9.43, -2.43], P < .001 and 4.28 [0.71, 7.86], P = .02, respectively) and absolute total ROM (TROM; -6.19 [95% CI = -10.28, -2.10]; P = .003) were predictors of injury, and these data exhibited homogeneity (absolute IR P value = .77, I2 = 0%; IR deficit P value = .41, I2 = 0%; absolute TROM P value = .78, I2 = 0%). No significance was observed for absolute external rotation (-2.86 [95% CI = -6.56, 0.83], P = .13), which had data with high heterogeneity ( P = .003; I2 = 83%). A deficit in horizontal adduction was a predictor of injury (-8.32 [95% CI = -12.08, -4.56]; P < .001); these data were homogeneous but yielded a moderate heterogenic effect ( P = .16; I2 = 50%).

CONCLUSIONS: High-quality evidence demonstrated that deficits in throwing-arm TROM and IR were associated with upper extremity injury in baseball players. Heterogeneity across studies for horizontal adduction suggested that this may be a modifiable risk factor for injury, but it requires further research.