Anatomic variations in the first extensor compartment of the wrist: accuracy of US.

PURPOSE: To evaluate the accuracy of ultrasonography (US) in determining the anatomic variations in the first extensor compartment of the wrist.
MATERIALS AND METHODS: Approval from the anatomic donations department was obtained. The first extensor compartment of the wrist of 40 nonembalmed cadaveric forearms (15 male and 25 female; age range at death, 65-100 years) were assessed at US by two observers for the presence or absence of a vertical septum, the presence or absence of an osseous ridge with a double groove in the bony floor, and whether there were single or multiple slips of the abductor pollicis longus and the extensor pollicis brevis tendons. These findings were also evaluated at dissection.
RESULTS: The accuracies of US in depicting a septum and an osseous ridge with a double groove were respectively 95% (95% confidence interval [CI]: 83%, 99%) and 100% (95% CI: 91%, 100%). At dissection, a septum was invariably associated with the presence of an osseous ridge. The accuracies of US in depicting multiple tendon slips of the abductor pollicis longus and the extensor pollicis brevis were respectively 80% (95% CI: 64%, 91%) and 97% (95% CI: 86%, 100%).
CONCLUSION: US was highly accurate in depicting anatomic variations in the first extensor compartment. US detection of an osseous ridge was an indirect sign of the presence of a septum dividing the first extensor compartment into two subcompartments. © RSNA, 2010.