Posterior malleolar ankle fractures - an effort in improving outcomes

A. Kaye, J. Widnall, J. Redfern, J. Alsousou, A. Molloy, L. Mason

Background: There is an increasing acceptance that the clinical outcomes following posterior malleolar fractures are less than satisfactory. In our previous multicenter study (Powell, BOFAS 2016) we showed that the Olerud-Molander Ankle Score (OMAS) was 79 for unimalleolar fractures and 65 for bi malleolar fractures, however it dropped significantly to 54 in trimalleolar fractures. In creating a treatment guiding classification, we report our results in a system change in management of posterior malleolar fractures in our unit.

Method: All fractures were classified according to Mason and Molloy classification (BOFAS 2015, FAI 2017) based on CT scans obtained pre-operatively. This dictated the treatment algorithm. Type 1 fractures underwent syndesmotic fixation. Type 2A fractures underwent ORIF through a posterolateral incision, and type 2B and 3 fractures underwent ORIF through a posteromedial incision. The patient remained NWB for 6 weeks postoperative. Data was collected from December 2014 to July 2017.

Results: Patient related outcome measures were obtained in 50 patients with at least 6 month follow up (mean 18 months). According to Mason and Molloy classification there were 17 type 1, 12 type 2A, 10 type 2B and 11 type 3. The mean OMAS for type 1 was 75.9 (Range 30-100, SD 18.4), type 2A 75.0 (range 35-100, SD 21.3), type 2B 74.0 (range 55-100, SD 13.7) and type 3 70.5 (Range 35-100, SD 17.1). An increase in OMAS of 4 is clinically significant.

Conclusion: We have been able demonstrate an improvement in OMAS for all posterior malleolar fractures with the treatment algorithm applied using the Mason and Molloy classification. Compared to our previous study we have successfully increased our OMAS scores to what would be expected from unimalleolar fractures. Mason and Molloy type 3 fractures have marginally poorer outcomes, which correlates with a more significant injury, however this does not reach statistical significance.