Assessment of Ankle Mortise Instability After Isolated Supination-External Rotation Lateral Malleolar Fractures

Abstract

Background: The diagnosis of clinically important instability following isolated supination-external rotation (SER) distal fibular fractures is a challenge. The purpose of this study was to investigate the accuracy of clinical findings including medial tenderness, swelling, and ecchymosis, combined with the gravity stress test and magnetic resonance imaging (MRI), in the assessment of ankle mortise stability in association with isolated SER-type lateral malleolar fractures. The external rotation (ER) stress test was used as the reference with which the methods of assessment were compared. Methods: Thirty-seven patients were enrolled prospectively. Using the ER stress test as a reference, we evaluated the sensitivity, specificity, likelihood ratio (LR), and post-test probability of instability when using clinical examination, the gravity stress test, and MRI for diagnosing ankle mortise instability after an isolated SER lateral malleolar fracture. Results: The positive LR for clinical findings ranged from 1.45 to 2.54, and the negative LR ranged from 0.25 to 0.70, shifting the pre-test probability to a rarely important degree. In contrast, the positive LR for the gravity stress test was 5.71 with a 95% confidence interval (CI) of 1.52 to 21.48, a moderate shift from the pre-test probability, and the negative LR was 0.33 (95% CI = 0.16 to 0.66), indicating a small shift. In cases with a deep deltoid ligament disruption identified on MRI, the positive LR was 3.05 (95% CI = 1.03 to 9.02) and the negative LR was 0.53 (95% CI = 0.31 to 0.91), demonstrating a small but sometimes important shift. Conclusions: The gravity stress test is a reliable method for diagnosing ankle mortise instability in patients with an isolated SER lateral malleolar fracture. Nevertheless, this test alone would not qualify as a replacement for the ER stress test. However, when the gravity stress test result is consistent with the clinical or MRI findings, its diagnostic value is almost equivalent to that of the ER stress test. Level of Evidence: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Arthroscopic Quantitative Measurement of Medial Clear Space for Deltoid Injury of the Ankle: A Cadaveric Comparative Study With Stress Radiography

“…A standard mortise radiograph was then obtained with the tibia in approximately 10°of internal rotation. 13,20 The standard mortise view was confirmed by the perpendicular position of the transfixation pin to the ground (Figure 4C). A 10-mm spherical metallic marker was placed at the lateral malleolus of the ankle for adjustment of radiographic measurement of the MCS.…”

“…A standard mortise radiograph was then obtained. 13 A 10-mm spherical metallic marker (Syntec Scientific Corporation. Taipei, Taiwan) was placed at the lateral malleolus of the ankle for adjustment of radiographic measurement of the MCS.…”

Diagnostic tools to evaluate ankle instability caused by a deltoid ligament rupture in patients with supination-external rotation ankle fractures: A systematic review and meta-analysis

“…In contrast, Nortunen et al [33] would not recommend MRI for evaluating deltoid ligament integrity since only 54.1% of the patients who appeared to have a deltoid ligament rupture according to an MRI, actually had a rupture. Jeong et al [16] concluded that using MRI alone is inadequate to evaluate deltoid ligament ruptures, while the results of Warner et al [19] suggest that MRI is able to detect deltoid ligament rupture with sufficient certainty. However, the results of Warner et al [19] may be questioned since they only included surgically treated patients with SER-type ankle fractures, which may explain the high prevalence of deltoid ligament ruptures and, ultimately, influenced the sensitivity and specificity.…”

Identifying Intra-Articular Pathology With Arthroscopy Prior to Open Ankle Fracture Fixation

“…Magnetic resonance imaging findings alone are not sufficient for the diagnosis of ligamentous injury and may miss deep deltoid injuries. 21 Cadaveric studies have shown that radiographs with the ankle positioned in dorsiflexion and external rotation are the most reliable combination for prediction of deep deltoid injury. 22 However, there is currently no consensus for recommendation on the objective amount of medial clear space widening, with some suggesting 4 to 6 mm as cutoff for a positive examination.…”