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

BACKGROUND: In a recent study, we documented that partially unstable Weber B/SER4a fracture types reach union with preserved normal ankle congruence after treatment with a functional orthosis and weightbearing allowed. In the present article, we present a case series of weightbearing stable bimalleolar fractures treated nonoperatively that extends our previously published research. METHODS: We included 5 patients with primarily nondisplaced bimalleolar ankle fractures that were stable on weightbearing radiographs. Participants were treated with a walking boot or cast with weightbearing allowed. We also provide a qualitative anatomical analysis of fracture morphology on computed tomographic scans. RESULTS: Median medial clear space (MCS) of fractured ankles after union were 2.4 mm (range, 1.5-3.1). Qualitative descriptions of fracture morphology showed that all fractures were oblique starting at the intercollicular groove of the medial malleolus and extended anteriorly and proximally. CONCLUSION: MCS measurements after fracture union of nonoperatively treated weightbearing stable bimalleolar fractures seemed consistent with normative data of ankle congruence in our previous study. We consistently recorded oblique fracture patterns involving the anterior colliculus, leaving the origin of posterior deep deltoid ligament intact. We present our material as an argument for the existence of a bony (bimalleolar) equivalent to the ligamentous SER4a fracture. LEVEL OF EVIDENCE: Level IV, prospective case series.