Relationship Between Patients' Self-Reported Injury Mechanism and MRI Outcomes in Hamstring Muscle Injury: A Prospective Cohort Study on 71 Patients.

Background: Hamstring muscle injury (HMI) is the most common injury in sports that require sprints and accelerations. Different HMI subtypes have been described according to the muscle, location, tissue, and severity of the injury. It is of interest to determine whether these subtypes are related to a particular clinical injury mechanism.

Hypothesis: There would be an association between the muscle involved and the injury mechanism.

Study design: Prospective, multicenter, observational cohort study.

Level of evidence: Level 3.

Methods: All patients underwent postinjury magnetic resonance imaging (MRI) and were assessed for their mechanism of injury using a survey. Statistical analyses used chi squared test and analysis of variance.

Results: A total of 71 patients were included in the present study. MRI scans were performed within 7.5 ± 4.9 days of injury. There was no significant association between the HMI mechanism and the injured muscle (χ² = 6.86; P = 0.34), or with proximo-distal position (χ² = 20.28; P = 0.16). There was a significant association between HMI mechanism and HMI grade (χ² = 23.7; P < 0.001) and the HMI volume (F(3,67) = 5.223; P = 0.003) with significant higher severity and higher volume in stretching than in running mechanisms (P = 0.002).

Conclusion: We showed an association between HMI mechanism and MRI scan grade and volume, with significant higher injury grade and larger volume in stretching mechanism.

Clinical relevance: These differences, depending on the mechanism of injury, may lead to changes in clinical practice.