CLINICAL FEATURES OF 83 POSTERIOR THIGH INJURIES WITH MRI CORRELATION

Abstract

There is little known about the clinical features of Posterior Thigh Injuries [PTI] with respect to the accurate diagnosis and prognosis of Hamstring Muscle Strain Injury [HMSI]. PURPOSE To prospectively assess the clinical features of PTI useful in the diagnosis of HMSI and their role in predicting duration of absence from competition. Timing of injury to determine the role of muscle fatigue in HMSI was also studied. METHOD: Onset, timing, location, pain, tenderness and competition days lost were recorded for all PTI. Intramuscular T2-weighted hyperintensity on MRI was used to differentiate HMSI from non-HMSI. RESULTS Eighty-three PTI were recorded with MR imaging confirming HMSI in 68(82%). Biceps femoris involvement in 55(81%) being the sole muscle injured in 32(47%) and the principal muscle injured in 49(72%). Most hamstring injuries were sudden onset N=62(91%) and occurred after a significant warm-up period N=57(84%). Site of injury was distributed evenly throughout the posterior thigh and was not important in terms of competition days lost. More competition time was lost with HMSI (mean 27 days) compared to non-HMSI (mean 16 days). CONCLUSIONS All PTI had pain and tenderness irrespective of diagnosis, HMSI or otherwise, and these features were not predictive of actual muscle injury. Therefore exceptions to the typical clinical features of HMSI occur suggesting a possible role for MR for accurate diagnosis of PTI. This study verifies that the biceps muscle is the most commonly injured hamstring muscle. HMSI had a poorer prognosis in terms of a longer absence from playing competition compared to PTI where hamstring muscle injury is not detected on MRI. Muscle fatigue maybe important in the pathogenesis of HMSI as most injuries occur after the warm-up period. Supported by grant from OrthoTech (part costs MR scans)%