Variations of the Posterolateral Tubercle of the Talus: Geometric Analysis, Angular Safe Zones, and Implications for Talar Fixation Using a Three-Dimensional Simulation Model

Objective. To investigate the prevalence of posterolateral tubercle variants and characterize the simulated safe zones and screw insertion angles for posterior-to-anterior talar screw fixation using individual 3D models from a Northeastern Thai skeletal collection. Materials and Methods. A total of 1,106 dry tali from 553 skeletons (301 males and 252 females), aged 22–106 years, were classified according to posterolateral tubercle type. Safe zones for posterior-to-anterior (PA) screw fixation were determined for the left and right tali in both sexes using 3D simulation models, and the widest possible screw insertion angles were simulated. Results. The posterolateral tubercle was classified into three types: Type 1 (almost absent, 1.36%), Type 2 (normal, 45.48%), and Type 3 (enlarged, 53.16%). In selected individual male talus models, the illustrated safe-zone configurations ranged from 20% to 50% on the left and from 30% to 60% on the right. In selected individual female talus models, the illustrated safe-zone configurations ranged from 20% to 70% on the left and from 20% to 50% on the right. Conclusion. The enlarged posterolateral tubercle was the most prevalent variant in the Northeastern Thai skeletal sample. The selected individual models illustrated differences in simulated safe-zone configurations and insertion angles according to side and sex. These findings may provide anatomical reference information for preoperative planning of screw fixation involving the posterolateral region of the talus.