Synovitis and soft tissue impingement of the ankle: assessment with enhanced three-dimensional FSPGR MR imaging

To assess soft tissue impingement as well as synovitis of the ankle associated with trauma by using contrast-enhanced (CE), fat-suppressed, three-dimensional, fast gradient-recalled acquisition in the steady state with radiofrequency spoiling (FSPGR) magnetic resonance (MR) imaging.

A total of 36 patients who had had chronic ankle pain associated with a traumatic injury undertook fat-suppressed CE three-dimensional FSPGR MR imaging and then arthroscopy of the ankle. The ankle joint was divided into four compartments by anatomic details: the anterolateral gutter, anteromedial gutter, anterior recess, and posterior recess. Synovial enhancement was graded as follows: grade I, no enhancement; grade II, linear enhancement; grade III, focal nodular enhancement; and grade IV, irregular nodular enhancement. MR grading of the synovial enhancement (synovitis, grade III or IV; soft tissue impingement, grade III or IV with its intrusion from the capsular reflection) was compared with arthroscopic findings. A control study of twenty asymptomatic ankles was done for determining enhancement. Arthroscopy confirmed synovitis in 47 compartments of 27 patients. Of the 27 patients, 15 revealed soft tissue impingement in 17 compartments.

For the assessment of synovitis, fat-suppressed CE three-dimensional FSPGR MR imaging had an accuracy of 72.9%, sensitivity of 91.5%, and specificity of 63.9%; whereas for that of soft tissue impingement it had an accuracy of 94.4%, sensitivity of 76.5%, and specificity of 96.9%. All of the asymptomatic subjects showed grade I (81%) or II (19%) synovial enhancement.

Fat-suppressed CE three-dimensional FSPGR MR imaging was sensitive for the evaluation of synovitis of the ankle associated with trauma, whereas it was specific for soft tissue impingement evaluation.