The importance of pre-operative CT imaging in posterior malleolus fixation and clinical outcomes

C. de Wet, R. Hackney, R. Clayton, S. Middleton

Background: 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.

Methods: 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.

Results: 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. 1 patient (1.5%) underwent revision for failure. 14% patients developed radiographic changes of osteoarthritis (89% Kellgren and Lawrence grade 1, 11% grade 3).

Conclusion: 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%.