Ankle MRI for Anterolateral Soft Tissue Impingement: Increased Accuracy with the Use of Contrast-Enhanced Fat-Suppressed 3D-FSPGR MRI

OBJECTIVE: To validate the use of contrast-enhanced (CE) fat-suppressed three-dimensional (3D) fast gradient-recalled acquisition in the steady state with radiofrequency spoiling (FSPGR) magnetic resonance imaging (MRI) for the diagnosis of anterolateral soft tissue impingement of the ankle, as compared to the use of routine ankle MRI. MATERIALS AND METHODS: Contrast-enhanced fat-suppressed 3D-FSPGR MRI and routine MRI scans were retrospectively reviewed for 45 patients with arthroscopically proven anterolateral impingement. In addition, scans were reviewed in 45 control subjects with diagnoses other than impingement. Two radiologists independently reviewed the two sets of images in random order. Using areas (Az) under the receiver operating characteristic curve (ROC), we compared the depiction of anterolateral soft tissue impingement in the two sets of images. RESULTS: The overall accuracy for lesion characterization was significantly higher (p < 0.05) using the CE fat-suppressed 3D-FSPGR MR images (Az = 0.892 and 0.881 for reader 1 and 2, respectively) than using the routine MR images (Az = 0.763 and 0.745). The use of CE fat-suppressed 3D-FSPGR MRI enhanced impingement depiction in most cases. However, in cases with a thickened non-enhancing scar or joint effusion, the routine images better depicted a soft tissue mass that intruded into anterolateral gutter than the CE images. CONCLUSION: The use of CE fat-suppressed 3D-FSPGR MRI of the ankle allows a more accurate assessment of anterolateral soft tissue impingement of the ankle, as compared to the use of routine MRI.

Subtalar Coalition: Usefulness of the C Sign on Lateral Radiographs of the Ankle

PURPOSE: To assess the usefulness of the talocalcaneal C sign in the diagnosis of subtalar coalition, as seen on lateral radiographs of the ankle. MATERIALS AND METHODS: Lateral radiographs of 12 ankles in 11 patients were included in this study. Twelve subtalar coalitions were confirmed by surgery (n=6), or by CT and/or MR (n=6). The presence of the talocal-caneal C sign on lateral ankle radiographs was determined. RESULTS: The C sign was continuous in six feet and interrupted in the remaining six. Subtalar coalition occurred simultaneously in the middle and posterior subtalar joints in two cases, the posterior subtalar joint only in six, and in the middle subtalar joint only in four. In six cases confirmed at surgery, subtalar coalitions consisted of both synostosis and non-osseous fusion (synchondrosis and/or syndesmosis) and in one case of middle subtalar coalition, there was a bony bridge. The remaining six cases, confirmed at CT or MRI, involved both synostosis and non-osseous fusion (n=1) or non-osseous fusion only (n=5). CONCLUSION: In the diagnosis of subtalar coalition, the talocalcaneal C sign, seen on lateral radiographs of the ankle, is a useful indicator.

Ankle Ligaments: Comparison of MR Arthrography with Conventional MR Imaging in Amputated Feet

PURPOSE: To compare magnetic resonance (MR) arthrography with conventional MR imaging in the evaluation of ankle ligaments. MATERIALS AND METHODS: Eight freshly amputated human feet underwent conventional MR imaging and MR arthrography. For the former, 1.5-T magnets in the axial, coronal and sagittal planes were used, and T1-weighted sequences were obtained. Following the injection of 6 -10 ml of diluted contrast media (Gd-DTPA 1:250), T1-weighted images were obtained in the same positions as conventional MR images. Paired conventional MR imaging and MR arthrography of each ankle ligament were rated on a five-point scale, and to reflect inter-group differences a Wilcoxon singed-rank test was used to compare the different measurements (p<0.05). In two ankles, MR images of the ligaments were correlated with ankle dissection. RESULTS: Anterior and posterior talofibular ligaments were more clearly revealed by MR arthrography than by conventional MR imaging, while calcaneofibular ligaments showed no difference between these two modalities. With regard to deltoid ligaments, visualization of the anterior and posterior tibiotalar ligament was much improved when contrast material was used to outline the ligament's articular aspect. Visualization of the posterior inferior tibiofibular ligament and inferior transverse ligament were also improved when the use of contrast material provided delineation of the articular side of the ligaments and separated them from adjacent bone. In addition, MR arthrography was very useful for identification of the posterior intermalleolar ligament, though its use did not enhance visualization of the calcaneofibular, tibiocalcaneal, spring or tibiospring ligaments. CONCLUSION: MR arthrography accurately revealed the anatomic details of ankle ligaments, and may therefore be more useful than conventional MR imaging for evaluation of these structures.