Open reduction and internal fixation of the posterior malleolus fragment frequently restores syndesmotic stability.

AIM: Comparison of unfixed, CRIF, and ORIF of the posterior malleolus fragment (PMF) regarding the frequency of trans-syndesmotic fixation and quality of reduction in trimalleolar (equivalent) fractures.

MATERIAL AND METHODS: Retrospective registry study. Patients with a trimalleolar (equivalent) ankle fractures were identified within the departments' fracture database. General demographics, treatment details, and fracture specific details (CT-scans) were assessed. Patients were grouped per the PMF treatment: not addressed, CRIF, ORIF.

RESULTS: 236 patients (53.0 ± 18.3 (range: 18-100) years), 58.1% female were eligible. The mean size of the PMF was 21.4 ± 10.4% (range: 2.7-55.9%), 71.6% were ≤25% of the tibial plafond. PMF fixation: Untreated 48.3%, CRIF 18.6%, ORIF 33.1%. ORIF of the PMF significantly (p < 0.001) reduced the frequency of trans-syndesmotic fixation (25%) compared to CRIF (61%) or untreated PMF (63%) with no significant influence of the PMF size (≤25%/>25%). ORIF resulted in a significantly (p < 0.001) better quality of reduction (1.2 ± 1.1 mm (range: 0-5 mm)) compared to CRIF (2.5 ± 2.1 mm (range: 0-8 mm)) and untreated PMF (2.5 ± 2.3 mm (range: 0-20 mm)). Neither the frequency of trans-syndesmotic fixation nor the quality of reduction differed significantly between untreated PMF and CRIF.

CONCLUSION: All posterior malleolus fragments, independent of their size, should be treated by ORIF, as this restores syndesmotic stability significantly more often than untreated PMF or CRIF.