Weightbearing Radiographs Reliably Predict Normal Ankle Congruence in Weber B/SER2 and 4a Fractures: A Prospective Case-Control Study

Abstract

Background: In Weber B/SER2-4 ankle fractures, assessment with weightbearing radiographs to ascertain stability of the ankle mortise has been advised. However, no previous studies report whether this method leads to preservation of normal ankle congruence. The purpose is to evaluate equivalence of ankle congruence of injured ankles after fracture union, vs the uninjured side, for stable SER2 and partially unstable SER4a fracture types. Methods: We conducted a prospective case-control study designed as an equivalence trial to evaluate if weightbearing radiographs predict whether stable/SER2 and partially unstable/SER4a Weber B ankle fractures reach union with preserved normal tibiotalar congruence and without a concomitant increase of treatment failure. A total of 149 patients with a Weber B fracture stable on weightbearing radiographs were recruited into the trial. All participants were treated with a functional orthosis and weightbearing allowed. Results from gravity stress radiographs classified ankles as SER2 or SER4a fracture types. We defined an equivalence margin in medial clear space difference of 1.0 mm. We also evaluated the reliability of obtaining measurements from weightbearing radiographs. Results: No differences in medial clear space between the injured and uninjured ankles were observed after fracture union for the SER2 group (mean difference 0.1 mm, 95% confidence interval [CI] −0.3, 0.0; P = .056), or the SER4a group (mean difference 0.0 mm (95% CI −0.1, 0.1; P = .797). No between-group differences were observed (mean difference 0.0 mm, 95% CI −0.2, 0.2; P = .842). These findings were consistent with equivalence. CIs for the intraclass correlation coefficients indicated excellent reliability. Conclusions: Assessment of stability of Weber B SER2/4a ankle fractures, with weightbearing radiographs, also predicts preservation of normal ankle congruence in those deemed stable, with no difference between SER2 and SER4a fracture types. Further, excellent reproducibility of the method of obtaining medial clear space measurements was demonstrated. Level of Evidence: Level III, case-control.

Weightbearing Stable Bimalleolar Ankle Fractures—Bony Equivalents to the Ligamentous Weber B/SER4a Fracture Type? A Prospective Case Series

“…Stability evaluation procedure using weightbearing radiographs were consistent with that described for the original study. 5 Participants were treated with a walking boot (AirCast AirSelect Standard, DJO Global Inc) or a below-the-knee cast for 6 weeks from baseline stability testing and were instructed to load the ankle as tolerated. All participants were scheduled for follow-up appointments at 2, 6, and 12 weeks after injury.…”

“…Method of obtaining MCS measurements was consistent with that described in the original article. 5 Secondary outcomes included loss of congruence and delayed fracture healing and were recorded as therapy failures. Fracture healing was assumed if callus formation was present on radiographs with concurrent pain-free palpation over the fracture site.…”

“…5 In the present article, we report on weightbearing stable bimalleolar fractures that were identified on the basis that they were excluded from our original study main cohort because they had a medial fracture. 5…”

“…5 In the present article, we report on weightbearing stable bimalleolar fractures that were identified on the basis that they were excluded from our original study main cohort because they had a medial fracture. 5 The primary objective was to develop a theoretical framework, using radiographic data, for why certain bimalleolar fractures appear stable during weightbearing. We conducted a prospective case series exploring if weightbearing stable bimalleolar ankle fractures that were treated nonoperatively heal with preserved tibiotalar congruence.…”

What’s New in Foot and Ankle Surgery

“…Gregersen and Molund 32 compared the tibiotalar congruence of an injured ankle with that of the contralateral, uninjured ankle in 149 patients. Those deemed stable (SER2 [supination external rotation]) or partially unstable (SER4a [gapping with stress but congruent on weight-bearing radiographs]) were allowed to be weight-bearing as tolerated in a functional orthosis.…”