CT-Based Calculation Model Assists Precise Treatment for Anterior and Posterior Ankle Bony Impingement.

Objective: Ankle arthroscope is the preferred tool for ankle surgeons to treat ankle impingement. However, there is no relevant report on how to improve the accuracy of arthroscopic osteotomy through preoperative planning. The aims of this study were to investigate a novel method to obtain the bone morphology in anterior and posterior ankle bony impingement through computed tomography (CT) calculation model, use this method to guide surgical decision-making, and compare the postoperative efficacy and actual bone cutting volume with conventional surgery.

Methods: This retrospective cohort study includes 32 consecutive cases with anterior and posterior ankle bony impingement by arthroscopy from January 2017 to December 2019. Mimics software was utilized to calculate the bony morphology and measure the volume of the osteophytes by two trained software engineers. The patients were divided into the precise group (n = 15) and the conventional group (n = 17) according to whether obtain and quantify the osteophytes' morphology with CT based calculation model preoperative. All patients were evaluated clinically using visual analog scale (VAS) score, American Orthopaedic Foot and Ankle Society (AOFAS) score, active dorsiflexion and plantarflexion angle before and after surgery at both 3 months and 12 months postoperatively. We obtained the shape and volume of bone cutting through Boolean calculation. Clinical outcomes and radiological data were compared between the two groups.

Results: The VAS score, AOFAS score, active dorsiflexion angle and plantarflexion angle were significantly improved in both groups postoperatively. In comparison of the VAS score, AOFAS score, and active dorsiflexion angle, the precise group were higher than the conventional group in the follow-up at 3 and 12 months postoperatively with statistical difference. The difference between the virtual bone cutting volume and the actual bone cutting volume of the anterior edge of distal tibia in the conventional group and precise group were 244.20 ± 147.66 mm and 76.53 ± 168.51 mm , respectively, there was statistical difference between the two groups (t = -2.927, p = 0.011).

Conclusion: Using a novel method of obtaining and quantifying the bony morphology with CT-based calculation model for anterior and posterior ankle bony impingement can help guide surgical decision-making preoperatively and assist precise bone cutting during the operation, which can improve the efficacy and evaluate the accuracy of osteotomy postoperatively.