Ulnar impaction syndrome: MR imaging findings

PURPOSE: To evaluate magnetic resonance (MR) imaging findings in ulnar impaction syndrome and changes after ulnar recession arthroplasty. MATERIALS AND METHODS: MR imaging and arthroscopy were performed in 30 wrists in 27 patients (aged 15 - 62 years) in whom ulnar impaction syndrome was diagnosed on the basis of physical examinations. MR imaging was performed in 11 wrists before and after surgery. T1- and Ta-weighted spin-echo images were obtained. Signal intensities in the lunate, triquetrum, and ulnar head were evaluated. RESULTS: There was focal abnormal signal intensity of the ulnar aspect of the lunate in 87% of wrists, of the radial aspects of the triquetrum in 43%, and of the radial aspects of the ulnar head in 10% before surgery. The signal intensity of the abnormalities was decreased on T1-weighted and decreased or increased on T2-weighted images. After surgery, the signal intensity of the lunate shifted from low through slightly low to normal on T1-weighted and from low through high to normal on T2-weighted images. CONCLUSION: Most ulnar impaction syndrome cases have characteristic focal signal intensity changes in the ulnar part of the lunate. The signal intensity often returns to normal after ulnar recession arthroplasty.