THE IMPORTANCE OF PREOPERATIVE CT IMAGING IN POSTERIOR MALLEOLUS FIXATION AND CLINICAL OUTCOMES

The treatment of ankle fractures with associated posterior malleolar fractures remains controversial. The aim of this retrospective study was to establish the importance of pre-operative CT imaging to identify fracture morphology and characterise die-punch fragment size and position. We aim to present clinical outcomes including infection, rates of revision and incidence of radiographic evidence of post-operative arthritis. We reviewed 323 consecutive patients from a trauma database of all ankle fractures managed in a trauma and orthopaedic department between January 2019 and December 2020. A total of 66 patients had posterior malleolus fractures. Imaging was reviewed using CareStream and data recorded using Excel. The mean age of patients was 52 years (range, 15–86 years). There was a 3:1 female to male preponderance. The majority of fractures were Lauge-Hansen SER (79%) with the remainder being 18% PER and 3% SAD. The posterior malleolar fragment was fixed in 70% of patients. 91% were fixed through a posterolateral approach using either a locking plate (65%), 1/3 tubular plate (7%), or posterior to anterior screws (20%). 9% were fixed using anterior to posterior screws. Die-punch fragments were identified in 88% with a mean size of 8mm (range, 2–19mm). The majority were largest on the axial (36%) or sagittal (33%) plane. Only one patient (1.5%) had a post-operative infection requiring further surgery. 6% patients had metalwork removal due to irritation. One patient (1.5%) underwent revision for failure. 14% patients developed radiographic changes of osteoarthritis (89% Kellgren and Lawrence grade 1; 11% grade 3). Die-punch fragments are common and therefore the use of pre-operative CT imaging is necessary to allow their identification to allow anatomic reduction. Utilising a posterior approach to fix these fractures comes with a low risk of infection (1.5%) and low rates of failure (1.5%).