MR imaging of posterior tibial tendon dysfunction

OBJECTIVE. The purpose of this study was to describe the MR findings of posterior tibial tendon dysfunction. MATERIALS AND METHODS. MR images and medical records were reviewed for 11 patients with surgically proven posterior tibial tendon abnormalities (i.e., tears or tenosynovitis) and for six patients with clinical evidence of posterior tibial tendon dysfunction. Our study group included 16 women and one man from 37 to 70 years old (mean, 53.5 years old). MR examinations used T1-weighted and T2-weighted spin-echo sequences in the oblique axial and sagittal planes. RESULTS. Abnormal MR findings were observed in all 17 patients. The spectrum of MR abnormalities included fluid in the tendon sheath of a normal tendon interpreted as isolated paratenonitis (tenosynovitis, n = 3); tendon thickening and surrounding fluid with normal tendon signal interpreted as tendinosis (degeneration, n = 1); tendon thickening with increased linear or heterogeneous intrasubstance signal interpreted as partial tear (n = 11); tendon discontinuity with fluid-filled tendon sheath interpreted as complete rupture (n = 2). In 11 patients, the posterior tibial tendon was explored at surgery. In these patients, MR imaging accurately showed two cases of isolated paratenonitis, one case of tendinosis, four partial tears, and two complete ruptures. In the remaining two patients, the presumed MR diagnosis did not correlate very closely with the surgical findings: one patient with isolated paratenonitis shown by MR imaging had tendinosis found at surgery; however, the surgery in this patient followed the MR examination by 10 months, a time during which degeneration might have occurred. The other patient had an MR diagnosis of partial tear, which was not found at surgery; however, tendon degeneration was severe and a small tear not reaching the tendon surface could have been missed at inspection. MR imaging characteristics of severe tendinosis and partial tear may overlap. CONCLUSION. MR imaging is effective for detecting abnormalities related to posterior tibial tendon dysfunction. Familiarity with the appearance of these changes facilitates accurate characterization.