The burden of shoulder problems highlights the need for injury prevention strategies. Identifying risk factors and developing strategies to prevent injury, based on these risk factors, are key components for preventing injuries in sports. This reflects the second and third step in the ‘sequence of prevention’ and ‘translating research into injury prevention practice’ models.
Overall, 4,740 studies were excluded from this analysis from being inadequate quality. After quality appraisal of the remaining 38 studies, 17 studies were included in the best-evidence synthesis of risk factors for shoulder injuries.
Baseball was the most commonly studied overhead sport in the best-evidence synthesis (seven studies) and volleyball and lacrosse populations were evaluated in five studies.
There was limited evidence for an increased risk of shoulder injuries in male high school and college lacrosse players compared with female players.
There was limited evidence that a high number of training hours per week (>16 hours/week) was associated with a higher injury risk among youth baseball pitchers and catchers.
There was limited evidence that junior baseball pitchers and catchers with a history of shoulder pain or elbow pain were at higher risk of injury than those without a history of pain.
Among US baseball pitchers with glenohumeral internal rotation deficit, total rotation deficit or flexion deficit, there was limited evidence of no association between shoulder range of motion and being placed on the disabled list. There was limited evidence that players with insufficient external rotation (>5° less than the non-dominant shoulder) had higher odds of being placed on the disabled list compared with those without insufficient external rotation. There was limited evidence of an association between greater humeral torsion in the dominant arm of US baseball pitchers (3.5° greater) and shoulder injury.
Recommendations for future research in the field
When planning the study, make a well-informed estimation of the likely number of cases during the follow-up period to avoid the risk of low statistical power in the analyses of potential associations, potential confounders and effect modifiers.
Take potential confounding into consideration in the analyses of associations between the exposure and an outcome if the study is not a large randomized controlled trial. Confounders must be chosen a priori based on known or potential risk factors for the outcome that may be unevenly distributed among exposed and unexposed individuals.
Stepwise selection algorithms should not be used to select confounders since they place an overemphasis on P values.
In prevention studies, do address the effect on injury risk, and assess if the preventive measures have an effect on the factors that were hypothesized to influence injury risk, for example, biomechanical or physiological measures.
Differentiate between incidence and prevalence, and preferably use incidence rate or incidence proportion when examining risk factors for injury.
Distinguish between traumatic and non-traumatic injuries, since these types of injuries potentially have different injury mechanisms and as such, different risk factors.
Present a clear definition of a healthy cohort at baseline in risk analyses, to avoid the risk of reverse causality.
Specify the time frame when it is reasonable that an injured player is considered to be at risk for a new injury (ie, subsequent injury categorization).
Measure time at risk on an individual basis, rather than on group level for a more precise estimate of the incidence rate.
Present crude results as well as results adjusted for identified confounders with CIs. This gives the reader a better understanding of the influence of the confounders and it improves understanding of what potential confounders should be included in baseline measures of future studies.
Asker M, Brooke HL, Waldén M, Tranaeus U, Johansson F, Skillgate E, Holm LW. Risk factors for, and prevention of, shoulder injuries in overhead sports: a systematic reviewwith best-evidence synthesis. Br J Sports Med. 2018 Oct;52(20):1312-1319. doi: 10.1136/bjsports-2017-098254. Epub 2018 Mar 26. Review