Age / Sex : 54 / M

M/54

C.C.; posterior thigh pain with palpable mass

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

* Send Application Answers to In Sook Lee, MD ([email protected])

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tear of semimembranosus m & tendon /c hematoma formation

Discussion

Findings; The semitendinosus muscle of distal level shows heterogeneously high signal intensities on T1- and T2-weighted MR images and discontinuity in the musculotendinous junction. Especially the semitendinosus tendon is retracted and shows wavy contour on sagittal and coronal planes.

Discussion

A hamstring strain or a pulled hamstring as it is sometimes called is a tear in one or more of the hamstrings muscles. Strictly speaking there are three hamstring muscles (Semitendinosus, Semimembranosus and Biceps femoris) which are known as the hamstring muscle group. Semitendinosus fibers arise from the inferomedial impression of the upper portion of the ischial tuberosity by way of a conjoint tendon with the long head of the biceps femoris muscle. Caudal to the ischial tuberosity, the semitendinosus muscle becomes bulbous, with the semimembranosus tendon lying anterior to it. More distally, the semitendinosus muscle forms a long tendon. This elongated distal tendon may predispose the muscle to rupture. The muscle fibers distal to the raphe insert onto the tibia with the gracilis muscle at the Gerdy tubercle. Hamstring muscle injury typically occurs in the region of the musculotendinous junction (MTJ), which, as opposed to being a distinct point, is really a 10–12-cm transition zone in which myofibrils contribute to form the tendon. Semitendinosus tears are a relatively infrequently injured structure in hamstring injuries. During sprinting or high velocity movements, hamstring injuries are frequent. Koulouris et al retrospective review of hamstring muscle complex injuries, discovered biceps femoris injuries in 124 case, semimembranosus in 21 cases, and semitendinosis in only 9 cases. The high signal intensity of edema, fluid, and blood products(high SI on T1WI) characteristically dissects along disrupted fibrils and lies between the fibrils of isointense but intact skeletal muscle near the musculotendinous junction, creating a feathered appearance. Such tears can be subtle at MR imaging.

Grade I muscle strains: Increased interstitial fluid signal between muscle fibers.

Grade II strains: There is increased signal between muscles. A focal muscular defect may or may not be seen. The tendon is thinned and irregular, with surrounding abnormal signal.

Grade III strains: There is a complete muscle disruption, with associated gap between retracted components.

References

1.     Koulouris G, Connell D. Hamstring Muscle Complex: An Imaging Review. RadioGraphics 2005;25:571-589

2.     Koulouris G, Connell D. Evaluation of the hamstring muscle complex following acute injury. Skeletal Radiol 2003;32:435-445