Total Ankle/Total Talus Replacement – Retrospective Comparison of Surgeon Decision Relative to Three-Dimensional Joint Health Assessment

Category: Ankle Arthritis; Hindfoot Introduction/Purpose: Recently, there has been a gradual rise in the utilization of patient-specific metallic implants within foot and ankle orthopedics, with the total ankle/total ankle replacement (TATTR) serving as a prime example. A critical decision made by surgeons in conjunction with the TATTR procedure involves the potential arthrodesis of the subtalar joint. This decision hinges upon numerous factors encompassing surgeon preference, radiographic indications, and clinical evaluations. However, no study has compared surgeon decision to the true joint health. The primary aim of this study was to determine if surgeon decision correlated with true three-dimensional joint health. It was hypothesized that arthrodesis of the subtalar joint with the TATTR procedure would be correlated with measures of sinus tarsi impingement or reduced joint space evident on 3D imaging. Methods: In this retrospective study, a 172 TATTR dataset was analyzed. Each patient underwent a bilateral computed tomography (CT) scan. Cases were semi-automatically segmented, and cases involving extensive anatomical damage were excluded. To assess joint health, a semi-automated distance mapping algorithm was written in MATLAB. Specific surfaces of the subtalar joint were manually selected. This included the posterior and middle/anterior talocalcaneal facets on the talus, and the sinus tarsi, anterior, middle, and posterior facets on the calcaneus. Distance mapping was performed by projecting a vector perpendicular from one bone triangulation until it intersected with its opposing triangulation. For detailed analysis, the sinus tarsi and posterior facet were divided into four and nine regions, respectively. Statistical analysis involved calculating the difference in means and Welch's t-test to assess significance. For visual analysis, rank plots were generated to determine if there was a clear distinction in joint spacing for fused and articulating procedures. Results: A total of 46 TATTR cases were included. No significance was found between groups for the four large regions (sinus tarsi, anterior, middle, and posterior facet), but when analyzing by specific regions, significance was found on the lateral portion of the posterior sinus tarsi as well as at both the medial portion of the anterior and middle sections of the posterior facet. When analyzing on rank plots for the posterior facet (anterior/medial), a clear cutoff was found around 2mm of joint space width (Figure 2). Table 1 summaries these results, and figures 1, 2, and 3 demonstrate our findings visually. Conclusion: In this study, surgeon decision to fuse the subtalar joint along with a TATTR procedure was compared to 3D imaging data of the pre-operative joint. Our findings indicate that patients in the fused+TATTR group, there was a noticeable anterior/medial downward shift of the talus. Moreover, our initial assumption regarding sinus tarsi impingement in fused cases was validated, as there was a significant reduction in sinus tarsi JSW. Future following of individualized surgeon decision could begin to establish trends in surgeon decision. Utilizing this tool prior to surgery in conjunction with the surgeon’s clinical decision-making process could potentially enhance patient outcomes.