Lateral Talar Subluxation Measurements in Nonoperatively Managed Weber B Ankle Fractures

Background: Lateral talar subluxation (LTS) was introduced as a measurement tool for evaluating isolated Weber B ankle fractures, with LTS >4 mm on gravity stress (GS) radiographs possibly indicating need for surgery. This study reviews LTS measurements in nonoperatively managed isolated Weber B fibula fractures to further investigate the validity of this previously stated cutoff.

Methods: The senior authors previously reported outcomes of a novel algorithm for nonoperative management of isolated Weber B ankle fractures. Outcome scores reported include American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot, Olerud-Molander (OMA), Foot and Ankle Ability Measure for activities of daily living (FAAM/ADL), and visual analog scale (VAS) scores. All patients achieved union of their fracture. LTS was measured on GS radiographs of both injured and contralateral uninjured extremities.

Results: Forty-two patients were included with minimum 1-year follow-up. Average age was 49 years (range 19-72). Mean measurements on injury GS radiographs were as follows: medial clear space (MCS) 4.45 mm (SD = 0.93), superior clear space (SCS) 3.46 mm (SD = 0.70), and LTS 2.33 mm (SD = 1.57, range 0-4.7 mm), with 35 (83.3%) patients having injury LTS ≤4 mm. Mean measurements on contralateral (uninjured) GS radiographs were as follows: MCS 3.39 mm (SD = 0.63), SCS 3.15 mm (SD = 0.50), and LTS 1.30 mm (SD = 1.28, range 0-4.8 mm). There was no statistically significant difference in all outcome measures based on amount of LTS (<2 mm, 2-4 mm, >4 mm).

Conclusion: Most patients had injury LTS ≤4 mm, although those with LTS >4 mm had excellent outcome scores. LTS measurements on normal ankles reveal a large range. LTS may be a useful adjunct in evaluating isolated Weber B ankle fractures but the 4-mm cutoff may not be entirely reliable. Further studies are required to validate LTS as a decision-making tool.

Level of evidence: Level IV, case series.