The hamstring muscle complex.

PURPOSE: The anatomical appearance of the hamstring muscle complex was studied to provide hypotheses for the hamstring injury pattern and to provide reference values of origin dimensions, muscle length, tendon length, musculotendinous junction (MTJ) length as well as width and length of a tendinous inscription in the semitendinosus muscle known as the raphe. METHODS: Fifty-six hamstring muscle groups were dissected in prone position from 29 human cadaveric specimens with a median age of 71.5 (range 45-98). RESULTS: Data pertaining to origin dimensions, muscle length, tendon length, MTJ length and length as well as width of the raphe were collected. Besides these data, we also encountered interesting findings that might lead to a better understanding of the hamstring injury pattern. These include overlapping proximal and distal tendons of both the long head of the biceps femoris muscle and the semimembranosus muscle (SM), a twist in the proximal SM tendon and a tendinous inscription (raphe) in the semitendinosus muscle present in 96 % of specimens. CONCLUSION: No obvious hypothesis can be provided purely based on either muscle length, tendon length or MTJ length. However, it is possible that overlapping proximal and distal tendons as well as muscle architecture leading to a resultant force not in line with the tendon predispose to muscle injury, whereas the presence of a raphe might plays a role in protecting the muscle against gross injury. Apart from these architectural characteristics that may contribute to a better understanding of the hamstring injury pattern, the provided reference values complement current knowledge on surgically relevant hamstring anatomy. LEVEL OF EVIDENCE: IV.

Postmortem imaging exposed: an aid in MR imaging of musculoskeletal structures.

OBJECTIVE: To identify factors that influence the quality of postmortem magnetic resonance (MR) images of musculoskeletal (MSK) structures as described in the literature, and to evaluate the extent to which these MR images are affected. MATERIALS AND METHODS: Four useful studies were retrieved from a PubMed and EMBASE search, covering the literature up to 1 March 2012. Three additional studies were included after a manual search from reference lists. RESULTS: Four human studies and three animal studies are considered in this review. Postmortem MRI quality can be affected by storage temperature, repeated freezing and thawing and fixation. Provided there was an adequate, but above-freezing storage temperature, postmortem changes in fresh cadavers did not appear to affect the MR image quality of MSK structures up to 14 days after death. Image contrast, signal intensities, and relaxation times are temperature-dependent, regardless of whether the specimen was fresh or postmortem for up to 7 days. Bad image quality can occur owing to accelerated autolysis. Freezing and thawing did not affect image quality, unless repeated too often, or whenever a heating pad was used to speed up the thawing process. Conventional formalin-based fixation leads to swelling of soft tissue and fluid accumulation in joints, and therefore to deteriorated images, with image quality just sufficient to visualize gross anatomy. CONCLUSION: Various factors were identified that affect postmortem MR image quality of MSK structures. Postmortem MR image quality was good, except for images of the fixated specimen. Freezing is the preferred method of conservation for specimens that are to be subjected to postmortem MRI.