Posterior fragment in ankle fractures: anteroposterior vs posteroanterior fixation

The aim of this study was to compare reduction quality and functional outcome of posterior malleolus fractures treated with indirect reduction and anteroposterior (AP) fixation or with direct reduction via a posterolateral approach and posteroanterior (PA) fixation.

Forty-eight patients with trimalleolar fracture were enrolled in the study. Patients were randomised in two groups: indirect reduction and AP fixation (AP group) and direct reduction and PA fixation (PA group). Inclusion criteria were: posterior fragment involving more than 25% of the articular surface, displacement over 2mm and ankle instability. The quality of reduction was evaluated using postoperative plain radiographs. Residual displacement of the posterior fragment, articular step-off and/or articular surface gap were analysed. The reduction was considered excellent (<1mm), good (1-2mm) or poor (>2mm). Range of motion (ROM) was measured bilaterally, and the difference in dorsiflexion between the injured and uninjured side was considered as dorsiflexion restriction. Demographic data (age, sex), type of fracture (AO/ASIF classification) and complications were noted.

Forty-six patients completed all follow-up examinations. There was no statistically significant difference in age (p = 0.41), sex (p = 0.29) or specific type of fracture (p = 0.83) distribution between the AP and PA groups. All fractures completely healed within 3 months. The overall complication rate was 8.7%. There was no statistically significant difference in complication rate between the two groups (p = 0.71). Radiological evaluation of the ankle showed there was significantly better quality of reduction with direct reduction via a posterolateral approach in the PA group. Excellent reduction was achieved in 79.2% and 45.5% of the PA and AP groups, respectively. The quality of reduction was significantly higher in the PA group compared with the AP group (p = 0.04). The mean restriction of dorsiflexion was lower in the PA group (5.96 ± 0.65°) compared with the AP group (6.45 ± 1.06°), but this difference did not reach statistical significance (p = 0.07).

The direct reduction technique via a posterolateral approach and PA fixation enables higher quality of reduction and better functional outcome in the management of the posterior fragment compared with indirect reduction and percutaneous AP fixation.