Open reduction and fixation does not improve short-term outcome of medium-sized posterior fragments in AO type B ankle fractures: one-year results of the POSTFIX randomized controlled trial

Aims Guidelines for treatment of posterior malleolar fragments (PMFs) in trimalleolar fractures are scarce, mainly based on retrospective studies, and show varying advice. The need for fixation of smaller (< 25%) PMFs remains particularly controversial. This study aims to evaluate the superiority of fixation of medium-sized PMFs versus no fixation of the fragment. Methods A multicentre randomized controlled trial was conducted between January 2014 and January 2022 in two Dutch level 1 trauma centres (protocol registration: NCT02596529). Patients presenting with an AO-44-B3 fracture with a medium-sized (5% to 25%) PMF were 1:1 randomized online between open reduction and internal fixation (ORIF) (FIX) versus no fixation (NO-FIX) of the fragment. A total of 41 patients were allocated online to FIX via the posterolateral approach and 40 patients to NO-FIX. The primary outcome was functionality measured by the American Academy of Orthopaedic Surgeons (AAOS) questionnaire one year postoperatively. Secondary outcomes were osteoarthritis (OA) measured on radiographs and the Olerud and Molander ankle score, visual analogue scale pain, and EuroQol five-dimension questionnaire during follow-up. Quality of reduction was assessed by step-off on postoperative CT scan and radiograph. Complications were recorded. Results After one-year follow-up, no difference (p = 0.141) in AAOS was found after FIX (median 90 (IQR 68 to 95)) and NO-FIX (median 93 (IQR 85 to 97)). OA (≥ grade 2) was present in four (17%) of the cases after FIX and five (20%) after NO-FIX (p = 0.763). After one year, median pain scores were 20 (IQR 5 to 40) versus 10 (IQR 5 to 25) (p = 0.032), and perceived general median health scores were 80 (IQR 60 to 89) versus 83 (IQR 71 to 90) (p = 0.596) after FIX and NO-FIX, respectively. Postoperative step-off > 1 mm on CT scan was present in 56% after FIX versus 71% after NO-FIX (p = 0.193). Complication rates were 18% versus 5% (p = 0.071) after FIX and NO-FIX, respectively. Conclusion ORIF of medium-sized posterior fragments in AO type B trimalleolar fractures does not prompt superior functional or radiological results after one-year follow-up. Longer follow-up is needed to evaluate intermediate or long-term effects. Cite this article: Bone Joint J 2025;107-B(4):461–469.