Automated Volume Measurement of the Syndesmosis Using 3D Weightbearing CT

Abstract

Category: Ankle; Trauma; Other Introduction/Purpose: Recent studies have shown that weight-bearing computed tomography (WBCT) that allows 3D volume measurement of the distal syndesmosis while under physiologic load brings about a higher accuracy in detection of syndesmotic instability, especially if subtle. Since the volume measurement method is complex, time-consuming, and has a noticeable interobserver bias, most clinicians might not still be interested in utilizing it in practice. Automatization of this measurement using computer-assisted methods will not only reduce the interobserver bias but also will be faster and more applicable in practice. This study aimed to develop an automated 3D syndesmosis volume measurement tool using image processing methods and compare the speed and the interobserver bias with human interpreters. Methods: We included 30 patients with subtle syndesmotic instability who had undergone WBCT and were diagnosed intraoperatively. Thirty individuals with otherwise healthy ankles who had WBCT images were allocated to the control group. The volume measurement up to 5cm proximal to the tibial plafond was considered as the most sensitive and specific method to assess syndesmotic stability based on the literature. An algorithm was developed using MATLAB software that could recognize and calculate the syndesmotic volume using WBCT images. The volume measurement method was used by two orthopaedic surgeons for the same population. The time spent by each surgeon and the algorithm was measured. Finally, the values were compared using the t-test; the interobserver correlation coefficient (ICC) was also calculated. P<0.05 was considered statistically significant. Results: The percentage of changes in 3D volume showed a significant difference at 5cm (25.4%; p<0.001), proximal to the tibial plafond. Based on our clinical study, the volume measurement up to 5cm showed a sensitivity of 95.8%, 95%CI:87.8-100, and specificity of 83.3%, 95% CI:68.4-98.2 for detection of syndesmotic instability. The ICC between the clinicians was 75% while using the automated measurement algorithm showed an ICC of 97%. The mean time spent by the clinicians was 268.4+-56.4 and by the algorithm was 2.9+-0.3 seconds (p<0.001, Figure 1). Conclusion: Given the fact that 3D volume measurement of the syndesmosis using WBCT is still a complex technique for most clinicians while it is one of the most accurate diagnostic methods based on recent literature, developing a faster and more accurate method for 3D volume measurement of the syndesmosis leads to a more reliable and easier to use the technique to be used in practice.