Concomitant Unstable and Stable Gravity Stress Tests on Weight-Bearing Stable Weber B Ankle Fractures Treated Nonoperatively

Abstract

Background: Replacing gravity stress tests with weight-bearing radiographs to evaluate the stability of Weber B (also called Lauge-Hansen supination-external rotation [SER]) ankle fractures results in a lower surgery rate, thus avoiding associated risks and complications. Still, nonoperative treatment of weight-bearing stable fractures is controversial because of the scarcity of strong evidence. We investigated the influence of a concomitant unstable gravity stress test compared with a stable gravity stress test on outcomes after nonoperative treatment of weight-bearing stable fractures. Methods: We performed a prospective, noninferiority study on 149 patients with Weber B ankle fractures and stable weight-bearing radiographs. Gravity stress radiographs classified fractures as stable (SER2 [n = 88]) or partially unstable (SER4a [n = 61]). All were treated with a functional orthosis and weight-bearing was allowed; patients were followed for 2 years. The primary outcome was the Manchester-Oxford Foot and Ankle Questionnaire (MOXFQ), with a range from 0 to 100, in which lower scores indicate fewer symptoms. A noninferiority margin was prospectively defined as 7.5 points. The secondary outcomes included the Olerud-Molander Ankle Score, assessment of ankle congruence, and treatment-related adverse events. Results: The primary outcome data were available for 144 (96.6%) of 149 participants at 2 years. The between-group difference in the MOXFQ score was 1.0 point (95% confidence interval, −1.4 to 3.4 points; p = 0.397) in favor of the SER2 group, consistent with noninferiority. We found no appreciable between-group differences for any other outcome. Conclusions: In Weber B/SER ankle fractures that are stable on weight-bearing radiographs, are treated with removable orthoses, and are allowed to bear weight, a concomitant unstable gravity stress test (SER4a) was not associated with worse patient-reported or radiographic outcomes compared with a stable gravity stress test (SER2) at the 2-year follow-up. Thus, the identification of stress instability seems redundant, which questions the applicability of stress instability for surgical decision-making. Level of Evidence: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

2023 Evidence-Based Medicine (EBM) Update

“…In a Level II prospective study, Gregersen et al 15 performed a noninferiority study of 149 Weber B ankle fractures deemed to be stable on weightbearing radiographs, treated with functional orthoses and early weightbearing. The authors found that those patients with a concurrent gravity stress test considered unstable (indicating a partial deltoid ligament rupture) did not have unfavorable outcomes at 2-year follow-up when compared with those with a stable gravity stress test.…”

Functional orthosis versus cast immobilization for weightbearing stable Weber B ankle fractures with concomitant unstable gravity stress tests

“…A difference of 7.5 MOxFQ points constitutes our noninferiority limit. Based on preliminary results from another study conducted on ankle fractures at our hospital, 24 we used a standard deviation (SD) of 12 points MOxFQ score. To detect a mean difference in MOxFQ score of 7.5 points (SD 12) at two years with a significance level of 5% and power of 90% with equal allocation to two arms will require 44 patients in each arm of the trial.…”

Effects of Fibular Plate Fixation on Ankle Stability in a Weber B Fracture Model With Partial Deltoid Ligament Sectioning

“…12 Other studies have suggested that fractures that are stable on weightbearing radiographs (SER2 and SER4a) can be treated nonoperatively with satisfactory short-and midterm results. 3,[5][6][7][8]11,13,14 We defined ankle stability as the joint's ability to remain anatomically aligned in the presence of deforming forces. Two recent biomechanical studies support the nonoperative treatment of SER4a fractures.…”

“…However, understanding ankle fractures with concomitant deltoid ligament injuries has evolved. 4 - 6 The traditional binary understanding of stability, either as stable or unstable, has been challenged by clinical and biomechanical findings indicating that partial deltoid ligament injuries, where the deep posterior tibiotalar ligament (dPTTL) remains intact, are common. 2 , 4 - 6 , 9 It has been proposed to classify such injuries as SER4a.…”

“… 4 - 6 The traditional binary understanding of stability, either as stable or unstable, has been challenged by clinical and biomechanical findings indicating that partial deltoid ligament injuries, where the deep posterior tibiotalar ligament (dPTTL) remains intact, are common. 2 , 4 - 6 , 9 It has been proposed to classify such injuries as SER4a. 4 In clinical practice, this injury is identified by an unstable radiographic stress test but a stable weightbearing radiograph.…”