Is There a Role for Preoperative CT Scans in Evaluating the Posterior Malleolus in Ankle Fracture- Dislocations?

Category: Trauma Introduction/Purpose: Ankle fractures are common injuries and have a wide variety of fracture patterns. There is a high incidence of posterior malleolar fragments with ankle fracture-dislocations. There has been increasing interest in the role of the posterior malleolus in the treatment of ankle fractures. Controversies still exist on the operative indications and best method of fixation for these injuries. The current study evaluates the role of preoperative CT scans in evaluating and treating posterior malleolar fractures in this injury pattern. Methods: At our institution we initiated a protocol of obtaining post reduction computed tomography (CT) scans for all ankle fracture-dislocations with an associated posterior malleolus (PM) fractures to evaluate the fracture pattern and its role in determining operative treatment. The CT scans were evaluated for number of fragments, loose intra-articular fragments or impacted fragments, and displacement. Displacement was measured as the maximum distance noted on axial, sagittal, or coronal images. Information obtained from the CT scans was compared to the preoperative plain radiographs. Also, the authors evaluated the use of CT scans in preoperative planning with respect to positioning and surgical incisions. Results: A total of 51 ankle fracture dislocations with posterior malleolar fractures were evaluated. The size of the PM fracture measured on lateral radiographs was 24.19% compared 25.19%(p=0.75) based on the CT scan. Preoperative CT scans were able to identify loose or impacted intra-articular fragments in 19/51 cases (37%) that were not seen on plain radiographs. Multifragmentary (>2 fragments) PM fractures not appreciated on plain radiographs were found in 18 patients (35%). A total of 20 (39%) fractures were approached using direct posterior surgical exposures. The surgical plan was altered in 31% of patients based on the CT scan. Overall, PM fractures treated with direct reduction had significantly less residual displacement than those treated through indirect reduction techniques (0.4mm v 1.13mm; p=0.04). Conclusion: Posterior malleolar fractures in the setting of ankle fracture-dislocations can have complex patterns. While the overall size of posterior fragment was similar on plain radiographs and CT scan, the CT offered improved evaluation of the pattern in terms of multiple or loose intra-articular fragments. This had a direct impact on the surgical technique and approach. Improved reductions were also seen with direct posterior approaches