Impact of Initial Immobilization Method on Outcomes in Unstable Weber B Ankle Fractures: A Retrospective Cohort Study.

BACKGROUND

Weber B ankle fractures with medial clear space (MCS) widening on stress radiographs are unstable injuries that may require surgical stabilization. Initial emergency department management varies, with patients receiving a cast or splint after reduction, although concerns for soft tissue complications often limit cast use. It remains unclear whether splint or cast immobilization affects clinical or radiographic outcomes.

METHODS

We retrospectively reviewed 295 patients treated for closed Weber B ankle fractures between January 1, 2017, and February 15, 2025; among them, 96 were determined to have an unstable pattern based on MCS widening on stress radiographs. Inclusion criteria were age ≥18 years, isolated fibular fracture with MCS widening indicating deltoid incompetence, and ankle radiographs at initial, postreduction, and follow-up time points. Patients with bimalleolar or trimalleolar fractures were excluded. We compared MCS values, surgical rates, reduction attempts, and complications across initial immobilization types.

RESULTS

Postreduction MCS was significantly smaller in the cast group compared to the splint group (2.79 ± 0.50 vs 3.41 ± 0.83 mm, P < .01). MCS at follow-up remained lower in the cast group and below the 4-mm threshold commonly used to guide surgical decision making (2.73 ± 0.54 vs 4.14 ± 1.10 mm, P < .01). A greater proportion of casted patients maintained reduction at follow-up (n = 72 vs 19, P = .04), reinforcing the association between initial casting and radiographic stability. There were no statistically significant differences in surgical or complication rates between groups.

CONCLUSION

Initial immobilization with a cast in unstable Weber B ankle fractures was associated with improved postreduction and follow-up radiographic alignment measured by MCS. The absence of increased complication rates among cast patients indicates that the superior radiographic stability with casting is not offset by increased complications, although the study may have been underpowered to detect a difference in safety profiles. Future prospective studies can inform the development of standardized immobilization protocols for unstable Weber B fractures.

LEVEL OF EVIDENCE: Level III, retrospective comparative study.