SLR - April 2020 - Candice N. Cooper

The Diagnostic Accuracy of Radiographs and Magnetic Resonance Imaging in Predicting Deltoid Ligament Ruptures in Ankle Fractures 

Reference:  Warner SJ, Garner MR, Fabricant PD, Schottel PC, Loftus ML, Hentel KD, Helfet DL, Lorich DG.  The Diagnostic Accuracy of Radiographs and Magnetic Resonance Imaging in Predicting Deltoid Ligament Ruptures in Ankle Fractures. HSSJ. Jan 15(2019):115-121. 

Scientific Literature Review

Reviewed By: Candice N. Cooper, DPM 
Residency Program: Hennepin County Medical Center – Minneapolis, MN  

Podiatric Relevance: The presence of a deltoid injury in supination external rotation (SER) ankle fractures indicates increased instability requiring operative treatment. The most common methods to assess for a deltoid injury have been stress radiographs and MRI evaluation. This article aims to compare ankle mortise radiographs and MRI when evaluating for a deep deltoid rupture (DDR) in patients who sustained SER ankle fractures.  

Methods: Patients who sustained SER ankle fractures, had pre-operative ankle mortise radiographs, manual stress exam radiographs if the medial clear space (MCS) < 5 millimeters on injury radiographs, and an ankle MRI within one week of the injury were included in this study. Patients were considered to have a DDR and underwent operative treatment if they had a MCS > 5 millimeters on mortise or stress radiographs or an MRI revealing a DDR. During operative treatment, the deep deltoid was evaluated and determined to be either intact or completely ruptured and then repaired using a 5 millimeter suture anchor.   

Results: Seventy-nine patients were included in this study. Sixty-nine patients were diagnosed with a DDR based on injury or stress radiographs and 58 patients were diagnosed with a DDR by MRI. During operative management, 71 patients were found to have a ruptured deep deltoid and eight were found to have an intact deep deltoid. Of the patients who were found to have a DDR intra-operatively, 52 had a MCS > 5 millimeters on mortise radiographs, 10 had a MCS > 5 millimeters on manual stress radiographs and 58 had a DDR diagnosed by MRI. MCS measurements had an 87 percent sensitivity, 13 percent specificity and 80 percent accuracy for diagnosing a DDR while MRI had an 82 percent sensitivity, 100 percent specificity, and 84 percent accuracy. In patients with MCS < 5mm on radiographs, MRI had a 74 percent sensitivity, 100 percent specificity and 79 percent accuracy for diagnosing a DDR while MCS had a 53 percent sensitivity, 20 percent specificity and 46 percent accuracy. In contrast, in patients with a MCS > 5 millimeters on radiographs, MCS measurements had 100 percent sensitivity and 95 percent accuracy while MRI had 85 percent sensitivity and specificity for diagnosing a DDR. The authors determined a final algorithm consisting of using only mortise radiographs if the MCS > 5 millimeters and obtaining an MRI for those whose MCS < 5 millimeters rather than performing stress radiographs. This resulted in a 93 percent sensitivity, 63 percent specificity and 90 percent accuracy for diagnosing a DDR.  

Conclusions: The authors concluded that MCS measurements on non-stress ankle mortise radiographs were most accurate for diagnosing a DDR when the MCS was > 5 millimeters. When the MCS measured < 5 millimeters, MRI proved to be a better diagnostic tool at determining if there was a DDR rather than stress radiographs. While this information is useful, MRI is not a highly utilized diagnostic tool for ankle fractures and question remains in the literature as to whether surgical fixation of a DDR in SER ankle fractures is necessary.  

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