Background: A challenge for sports physicians is to estimate the risk of a hamstring re-injury, but the current evidence for MRI variables as a risk factor is unknown.
Objective: To systematically review the literature on the prognostic value of MRI findings at index injury and/or return to play for acute hamstring re-injuries.
Data sources: Databases of PubMed, Embase, MEDLINE, Scopus, CINAHL, Google Scholar, Web of Science, LILACS, SciELO, ScienceDirect, ProQuest, SPORTDiscus and Cochrane Library were searched until 20 June 2016.
Study eligibility criteria: Studies evaluating MRI as a prognostic tool for determining the risk of re-injury for athletes with acute hamstring injuries were eligible for inclusion.
Data analysis: Two authors independently screened the search results and assessed risk of bias using standardised criteria from a consensus statement. A best-evidence synthesis was used to identify the level of evidence. Post hoc analysis included correction for insufficient sample size.
Results: Of the 11 studies included, 7 had a low and 4 had a high risk of bias. No strong evidence for any MRI finding as a risk factor for hamstring re-injury was found. There was moderate evidence that intratendinous injuries were associated with increased re-injury risk. Post hoc analysis showed moderate evidence that injury to the biceps femoris was a moderate to strong risk factor for re-injury.
Conclusion: There is currently no strong evidence for any MRI finding in predicting hamstring re-injury risk. Intratendinous injuries and biceps femoris injuries showed moderate evidence for association with a higher re-injury risk.
Systematic review registration: Registration in the PROSPERO International prospective register of systematic reviews was performed prior to study initiation (registration number CRD42015024620).
Keywords: Hamstring; MRI; Recurrent; Risk factor; Thigh.
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