Evaluation of posterior tibial pathology: comparison of sonography and MR imaging.

OBJECTIVE: To compare the results of sonographic (US) and magnetic resonance (MR) imaging in detecting pathology of the posterior tibial tendon (PTT) in patients with PTT dysfunction.

DESIGN: Twenty-two ankles that were clinically suspected by the orthopedic surgeon to have PTT dysfunction were evaluated with US (10 MHz linear-array transducer) and 1.5 T MR examinations within the same day. The US and MR studies were conducted and interpreted by two sonologists and two musculoskeletal radiologists who were masked to the results of the other study. Four patients had bilateral studies. Classic clinical findings were utilized as a standard reference in staging PTT dysfunction.

PATIENTS: Eighteen women (mean age 61 years, age range 39-86 years).

RESULTS: Based on a commonly accepted staging system for PTT dysfunction, 6 ankles were classified as stage I, 11 ankles as stage II, and 5 ankles as stage III. All stage I ankles were interpreted as having an intact PTT by both MR imaging and US. In the stage II and III tendons, MR imaging demonstrated PTT tears in 12 of 22 examinations, including 11 partial tears and 1 complete tear. US demonstrated PTT tears in 8 of 22 examinations, including 8 partial tears and no complete tears. The findings of US and MR imaging were consistent in 17 of 22 cases (77%). The five inconsistencies were as follows: in 4 cases, US reported tendinosis when MR imaging interpreted partial tears (no change in management); in one case, US diagnosed a partial tear when MR reported a complete tear of the PTT (no change in management because the clinical findings were more consistent with a partial tear).

CONCLUSIONS: In this study, US and MR imaging of the PTT were concordant in the majority of cases. US was slightly less sensitive than MR imaging for PTT pathology, but these discrepancies did not affect clinical management.