Association of Posterior Malleolar Comminution and Preoperative Tibiotalar Subluxation/Dislocation With Functional Outcomes After Surgical Treatment of Trimalleolar Ankle Fractures.

BACKGROUND: Posterior malleolar injury features associated with function after trimalleolar ankle fracture remain incompletely defined. PURPOSE: To evaluate associations of posterior malleolar comminution and preoperative tibiotalar subluxation/dislocation with postoperative outcomes. STUDY DESIGN: Retrospective comparative study. METHODS: Fifty-eight adults surgically treated for unilateral trimalleolar ankle fractures between February 2021 and June 2025 were reviewed. Preoperative radiographs and CT were assessed for morphology, comminution, and tibiotalar congruity. Comminution was defined as two or more additional fragments accompanying the main posterior malleolar fragment. Final follow-up outcomes were FADI, AOFAS Ankle-Hindfoot score, VAS pain, and ankle range of motion. Multivariable linear regression assessed adjusted associations. RESULTS: Median follow-up was 24 months (range, 12-144). Comminution was associated with lower median FADI (79.5 versus 95; p = 0.001), lower AOFAS (79 versus 93; p = 0.001), and higher VAS (4 versus 2; p = 0.001). Plantarflexion distributions differed (p = 0.040), whereas dorsiflexion did not (p = 0.052). After adjustment for age, sex, injury energy, syndesmotic fixation, and preoperative tibiotalar incongruity, comminution remained associated with lower FADI (β = -4.494; p = 0.001), lower AOFAS (β = -4.497; p = 0.003), and higher VAS (β = 0.668; p = 0.001). Preoperative incongruity was also associated with poorer outcomes. CONCLUSIONS: Posterior malleolar comminution and preoperative tibiotalar subluxation/dislocation were associated with function and pain after adjustment. Comminution may reflect local fracture complexity and articular fragmentation rather than external trauma energy. CT assessment should consider fracture complexity and joint congruity in addition to conventional morphology and fragment size. LEVEL OF CLINICAL EVIDENCE: III.