Objective: The purpose of this study was to examine relationships between MR imaging measurements of the extent of hamstring injury and the amount of time lost from competition in a group of athletes.
Subjects and methods: Thirty-seven athletes with suspected hamstring injury underwent T1 and inversion recovery T2 turbo spin-echo MR imaging in axial and sagittal planes. The presence and dimensions of abnormal focal intra- and extramuscular T2 hyperintensity were independently recorded by two radiologists, and the muscles involved and intramuscular location of injury were noted. The percentage of abnormal cross-sectional muscle area, abnormal muscle volume, and length of extramuscular T2 hyperintensity were measured from T2-weighted images depicting the maximal extent of the injury. Time (days) lost from competition was noted during follow-up.
Results: MR imaging detected hamstring muscle and linear extramuscular T2 hyperintensity in 30 (81%) and 25 (68%) of 37 athletes, respectively. The long head of the biceps was the dominant site of injury in 21 cases. The musculotendinous junction was involved in 28 (76%) of 37 cases. A relationship was seen between days lost from competition and percentage of abnormal muscle area (r = 0.63, p = 0.001) and volume of muscle affected (r = 0.46, p = 0.01), but only a trend for linear extramuscular T2 hyperintensity (r = 0.33, p = 0.12) was shown.
Conclusion: Rehabilitation time was related to MR measurements such as the percentage of abnormal muscle area and approximate volume of muscle injury. Hamstring injury most frequently involved the long head of the biceps femoris muscle, and involvement of the intramuscular tendon was common.