SLR - July 2020 - Monte J. Schmalhaus

Quantification of Postoperative Posterior Malleolar Fragment Reduction Using 3-Dimensional Computed Tomography (Q3DCT) Determines Outcome in a Prospective Pilot Study of Patients with Rotational Type Ankle Fractures

Reference: Meijer DT, de Muinck Keizer RO, Stufkens SAS, et al. Quantification of Postoperative Posterior Malleolar Fragment Reduction Using 3-Dimensional Computed Tomography (Q3DCT) Determines Outcome in a Prospective Pilot Study of Patients with Rotational Type Ankle Fractures. J Orthop Trauma. 2019;33(8) 

Scientific Literature Review

Reviewed By: Monte J. Schmalhaus, DPM
Residency Program: Kaiser SF Bay Area Foot & Ankle – Oakland, CA

Podiatric Relevance:
Patients with rotational ankle fractures that have a posterior malleolar (PM) fragment generally have poorer outcomes compared to those without. Patient outcomes depend on pattern of injury, fragment size, residual step-off, and postoperative gap. Traditionally, the decision to fixate these fractures is based off the size of the fracture fragment and percent of articular surface involved. Size of the fracture fragment and the percent of articular cartilage involved can be difficult to determine on regular radiographs and lacks true prognostic value. The purpose of this study was to examine patients with a rotational ankle type injury with PM involvement (OTA/AO type 44) and use 3-Dimensional Computed Tomography (Q3DCT) to quantify posterior fragment size (percent of joint surface), residual intra-articular step-off (mm) and postoperative gap (mm2) of the PM and how it relates to patient- and physician- based outcome measures.

Methods: This prospective cohort study included thirty-one patients with rotational ankle type fractures with PM fragments. Q3DCT scans were obtained within 7 days postoperatively to quantify residual step-off and reduction. Radiographs and Foot and Ankle Outcome Score (FAOS) and Short-Form 36 (SF-36) pain and symptom questionnaires were obtained one year postoperatively. PM fractures were classified according to the Haraguchi classification as follows: type 1: n=17, type II: n=7, and type III: n=7. Patients were also classified using the OTA/AO classification as follows: 44A: n=1, 44B: n=26, and 44C: n=4. Eighteen (58 percent) of the thirty-one patients were treated with fixation (direct and indirect) of the PM. 

Results: Average residual postoperative step-off determined by Q3DCT showed a mean of 0.6 mm. Nine (29 percent) patients were considered to have perfect anatomical reduction, 12 (39 percent) patients had 0-1 mm, 8 (26 percent) patients had 1-2 mm, and 2 (6 percent) patients 2-3 mm. Residual step-off was significantly correlated with FAOS symptoms and pain score. No significant correlations were found with SF-36 scores and ankle arthrosis. Residual postoperative gap showed a mean of 12.6 mm2 and showed no correlation with FAOS, posttraumatic arthrosis, or SF-36 scores. Secondary outcomes showed average posterior fragment articular surface size was 12 percent of the joint surface. Posterior fragment size had a moderate correlation with arthrosis but no significant correlations with FAOS and SF-36 scores.

Conclusions: Overall, this study showed patients with rotational type ankle fractures involving the PM showed a significant correlation with residual intra-articular step-off and fracture size with patient reported pain and symptoms as shown on Q3DCT.  Limitations of this study include, relatively short follow up and small amount of patient population operated on by different surgeons. Despite the limitations, this article shows that both fracture size and residual intra-articular step-off – but not gap- as measured by Q3DCT have an impact on patient outcomes in rotational ankle fractures with PM involvement.

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