Friday, November 21, 2008

Hamstrings and Filet Mignon

The reason I gave up eating red meat can be traced back to my experiences as a medical student dissecting cadavers in gross anatomy. I learned that filet mignon was a cut from the psoas major muscle of the steer. Knowing that, and looking simultaneously at the psoas major of a human (albeit a dead one), did the trick— instant vegetarian. Eventually I gained back my appetite for meat, but it's now pretty much restricted to fish and chicken.

The "hamstrings" are the muscles that compose the posterior thigh. Roughly speaking, they run from the pelvis to the knee, and are composed of the biceps femoris, semitendinosus and semimembranosus muscles. The ham of the dinner table is typically the hamstring of the pig:

Photo by cactusbones
The verb "hamstring", meaning "to disable or render useless", derives from the observation that cutting the hamstring tendons renders a person or animal lame.

Hamstring injuries are common in sports. Many people consider these to be fairly innocuous injuries, but Askling et al. recently pointed out that these can be extremely debilitating injuries (AJSM 36:1799-1804,2008).

Consider this case, a 55 year-old female athlete, with sustained a sports injury three weeks ago:

A coronal T1-weighted image depicts a near-complete avulsion of the right hamstring tendon (red arrow) from the ischial tuberosity. Note the normal left hamstring (green arrows).

An axial T2-weighted image with fat saturation shows the nearly naked right ischial tuberosity (red arrow), where the hamstring tendon has been avulsed. Note the normal left hamstring tendon (green arrow):

Askling et al. examined 30 subjects from 21 different sports. All the hamstring injuries they studied were located proximally in the posterior thigh, close to the ischial tuberosity. They found that a large percentage of patients (47%) actually chose to give up their sport after an extended time of rehabilitation (median, 63 weeks). Of those patients that returned to sports, 88% of the subjects still reported symptoms from the injury.

Thus, high-grade partial or complete proximal hamstring tears can be an extremely debilitating, serious injury that can have a prolonged recovery time. It is important to give an accurate description of the location and degree of tear when interpreting the MRI examination.

Vic David MD

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