Summary

This study found that Weber B/SER ankle fractures that appear stable on weightbearing radiographs can be treated successfully with orthoses and weightbearing allowed, resulting in excellent clinical outcomes at two years. Interestingly, a concomitant unstable gravity stress test, which may indicate a partial deltoid ligament rupture, did not influence the outcome.

Abstract

Background

Assessment of potential tibiotalar displacement (stability) should dictate treatment of Weber B/supination-external rotation (SER) fractures. Tibiotalar stability is primarily determined by competence of the deltoid ligament. If intact (SER2), abundant evidence supports functional orthosis treatment. While if ruptured (SER4), operative fixation is necessary to preserve stability. However, evidence suggest that one third to half of these common fractures probably have partial deltoid ligament rupture (classified SER4a), determined by stability evaluation using weightbearing radiographs deemed stable, but with concomitant stress tests deemed unstable. Traditionally, SER 4a fractures have been treated operatively, but some studies have suggested that they may be eligible for nonoperative treatment. It remains unclear whether it is necessary to distinguish between weightbearing stable fractures with (SER4a) and without (SER4a) concomitant stress instability and treat them differently.

We undertook this study to evaluate outcome non-inferiority of weightbearing stable Weber B fractures with concomitant gravity stress radiographs considered unstable (SER4a) and stable (SER2) after a consistent treatment protocol using functional orthoses and weightbearing allowed.

Methods

We performed a prospective, non-inferiority study on 149 patients with stable weightbearing radiographs. Gravity stress radiographs were used to classify fractures as stable (SER2, n=88) or partially unstable (SER4a, n=61). All participants were treated with a functional orthosis and weightbearing allowed and were followed for two years. The primary outcome was the Manchester-Oxford foot and ankle questionnaire (MOxFQ: range 0-100; lower scores indicate fewer symptoms). A non-inferiority margin was prospectively defined as 7,5 points. Secondary outcomes included the Olerud-Molander Ankle Score, assessment of ankle congruence of injured ankles versus uninjured side, treatment-related adverse events, and thromboembolic events.

Results

Primary outcome data were available from 144 out of 149 (96,6%) participants at two years. The between-group difference was 1.0 MOxFQ points in favour of the SER2 group (95% confidence interval -1.4 through 3.4, P = .397). These findings were consistent with non-inferiority. We found no appreciable between-group differences for any other outcome.

Conclusions

In Weber B fractures that are stable on weightbearing radiographs, nonoperative treatment using functional orthoses and weightbearing allowed leads to excellent and non-inferior outcomes comparing patients with concomitant stress test instability (SER4a) and with stress test stability (SER2). These findings suggest that all weightbearing stable Weber B fractures may be treated functionally with orthoses, and identification of gravity stress instability seem redundant.