Tibialis Anterior Tendon and Extensor Retinaculum: Imaging in Cadavers and Patients with Tendon Tear

OBJECTIVE: Under the hypothesis that the anatomic relationship of the tibialis anterior tendon and extensor retinaculum of the foot and ankle is relevant to the clinical aspects of a tear in that tendon, we assessed the anatomic details of these structures using MRI in cadavers and evaluated MRI in patients with a tibialis anterior tendon tear. MATERIALS AND METHODS: Seven cadaveric feet underwent detailed MRI using standard and oblique coronal planes with respect to the course of the tibialis anterior tendon and extensor retinaculum. Cadaveric sections subsequently provided an anatomic correlation. MR images of seven patients with tibialis anterior tendon tear were analyzed by consensus of two musculoskeletal radiologists. RESULTS: Imaging-anatomic correlations allowed identification of the tibialis anterior tendon and extensor retinaculum. The tendon passed through three tunnels formed by the superior extensor retinaculum, oblique superomedial, and oblique inferomedial limbs of the inferior extensor retinaculum. Of seven patients with the tendon tear, three patients had complete tears and four patients had partial tears. In all partial tears, the level of the tear was at the ankle joint, corresponding to the approximate level of the oblique superomedial limb. In all complete tears, the proximal ends of torn tendons were retracted to a level below the oblique superomedial limb. In all tears, the oblique superomedial limb surrounding the torn tendon was seen with thickening in four patients and enhancement after IV gadolinium injection in two patients. Other findings included a bulbous appearance or swelling of the torn tendon in two complete and two partial tears and fluid collections within the tendon sheath and in an area confined by the extensor retinaculum in four patients. CONCLUSION: The relationship of the tibialis anterior tendon and extensor retinaculum is well depicted on MRI, even in patients with a tibialis anterior tendon tear, and is clinically relevant to the tear of this tendon.