Ulnar collateral ligament: differentiation of displaced and nondisplaced tears with US and MR imaging.

PURPOSE: To compare the usefulness of ultrasound (US) and magnetic resonance (MR) imaging in the differentiation of displaced and nondisplaced tears of the ulnar collateral ligament (UCL). MATERIALS AND METHODS: Seventeen patients (eight female and nine male, aged 14-70 years) with clinically diagnosed tears underwent examination with US and MR imaging. T1-weighted, spin-echo (SE) and T2-weighted, turbo SE sequences were used. MR and US findings were compared with those of surgery. Normal UCLs in 21 volunteers were also examined with MR imaging. RESULTS: The results of US were correct in 15 patients, but displaced and nondisplaced ruptures were misinterpreted in two patients (sensitivity, 88%; specificity, 83% for displaced, 91% for nondisplaced). Sensitivity and specificity were both 100% for MR imaging. The T2-weighted sequence was more useful because the normal UCL is rarely homogeneously hypointense. CONCLUSION: MR imaging is better than US, but both methods are useful in the evaluation of the torn UCL.