Ilan Elias MD, Presenter: Nothing to Disclose

Adam C. Zoga MD, Abstract Co-Author: Speakers Bureau, Bayer AG

Sachin Dheer MD, Abstract Co-Author: Nothing to Disclose

Marcus P. Besser PhD, Abstract Co-Author: Nothing to Disclose

Steven M. Raikin, Abstract Co-Author: Nothing to Disclose

William B. Morrison MD, Abstract Co-Author: Medical Advisory Board, ONI Medical Systems, Inc

Our objective was to assess the utility of MRI in diagnosing injury to the Lisfranc ligament, and to determine whether conventional non-invasive MRI is a reliable tool for diagnosing Lisfranc joint complex instability, using manual stress radiographic evaluation under anesthesia (MSRE) and surgical findings as a reference standard.

MRI exams dedicated to the midfoot at 1.5 Tesla in 21 patients with traumatic Lisfranc joint complex injury and equivocal radiographs were evaluated by two MSK radiologists. Signal and morphology of the dorsal (dC1-M2) and plantar (pC1-M2M3) bundles of the Lisfranc ligament were assessed on long and short axis sequences as was integrity of the plantar tarsal-metatarsal (pC2-M2) ligament. Fluid signal along the lateral aspect of the first metatarsal was recorded as were any regional fractures. MRI observations were correlated with MSRE/surgery findings (stable versus unstable Lisfranc joint) using logistic regression to find the best predictors of Lisfranc joint instability.

At surgery, there were 17 unstable and 4 stable Lisfranc joints. The strongest MRI predictor for instability was disruption or attenuation (grade 2/3 sprain) of the plantar C1-M2M3 ligament on long axis sequences. Using the regression model from this predictor, the sensitivity, specificity and positive predictive value of MRI for Lisfranc joint instability was 94%, 75% and 94% respectively. 19/21 (90%) were correctly classified as stable vs unstable on MRI: At MRI, 18/21 subjects had disruption of the pC2-M2 ligament, 13 patients had fluid signal tracking along the lateral aspect of the first metatarsal, and 9/21 had fractures, but these observations had low predictive values for instability.

MRI with a dedicated midfoot protocol is a sensitive and specific modality for predicting Lisfranc joint complex instability in the setting of equivocal radiographs. Disruption or attenuation of the plantar Lisfranc ligament bundle (pC1-M2M3) on long axis sequences is the strongest predictor of an unstable injury requiring surgical stabilization. A normal ligament at MRI strongly suggests stable midfoot, regardless of concomitant fractures or pC2-M2 ligament injury, and may obviate the need for MSRE under anesthesia.

MRI is a sensitive and specific modality for predicting Lisfranc joint complex  instability in the setting of equivocal clinical examination findings and radiographs.

Elias, I, Zoga, A, Dheer, S, Besser, M, Raikin, S, Morrison, W, Prediction of Lisfranc Joint Complex Instability: Comparison of MRI with Intraoperative Findings.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6012144.html