Football physicians realize that a hamstring strain has climbed to the top of the injury rankings in professional football. These same physicians also know that the time lost to this injury is proportional to the amount of tissue damaged so MRI is a common method to confirm the diagnosis and make an estimate on the possible time when a player can return to training and competition.
Ekstrand’s group wanted to see just how accurate the use of MRI as a prognostic tool for time loss from a hamstring strain and to look at any association between the circumstances of the injury and the MRI findings. This prospective cohort project followed 23 European professional teams between 2007 and 2011. Each team’s medical staff was responsible for recording exposures and all time loss injuries. Imaging was graded according to a modification of Peetrons classification system that resulted in four grades (grade 0-3); grades 2 and 3 represented fibre disruption.
There were a total of 516 hamstring injuries and 58% of these injuries underwent an MRI. Of those that were evaluated with MRI, 13% were grade 0 injuries, 57% were grade 1 injuries, 27% were grade 2 injuries and 3% were grade 3 injuries. Grade 0 and 1 injuries (70% of the total) accounted for over half (2141/3830 days) of the total days lost. Lay-off time increased with each grade of injury: (8±3, 17±10, 22±11 and 73±60 days for grades 0-3 respectively, P<0.001). The biceps femoris was the most common location of injury (83%)followed by the semimembranosus (11%) and semitendinosus (5%) with 16% of all injuries being a re-injury (34/207), all of which were to the biceps femoris. MRI can help verify the diagnosis of a hamstring injury and when graded, can help estimate the time lost by the player. The majority (70%) of hamstring injuries to professional football show no signs of fibre disruption on MRI, but are still the major cause of time lost