Finite Element Analysis of the Biomechanical Effect of Bone Resection Depth in the Distal Tibia after Total Ankle Replacement

Purpose Correct resection of the tibial bone in total ankle replacement (TAR) procedure is crucial for accurate TAR implant positioning and the avoidance of post-operative complications. However, the biomechanical influence of the resection depth of tibial bone for TAR is not clearly understood. Therefore, the objective of this study is to investigate the biomechanical characteristics of the distal tibia with different resection depths after primary TAR. Methods Tibial bone models of eight healthy volunteers (age 27 ± 3.83 years old, 5 Males and 3 females) were constructed and 6 to 16 mm resection depths of each bone were performed under the guidance of senior foot and ankle surgeons. A 4 mm tibial plate was reversed engineering to completely cover the bone resection surface. And finite element analyses were performed to evaluate the biomechanical behavior of these models. 5.2 times of body weight was applied as a worst-case scenario loading condition and element-based material assignment was used for the tibial bone. The resection surface area, resection volume, von Mises stress, and strain at each resection surface were analyzed. Results As bone resection depth increased from 6 to 16 mm, the resection surface area decreased from 1125.25 ± 99.76 mm^2 to 889.27 ± 101.08 mm^2 , while the resection volume increased from 14701 ± 4376.30 mm^3 to 25116 ± 3354.27 mm^3 . The biomechanical simulation results showed average von Mises stress increased from 3.46 ± 1.06 MPa to 3.85 ± 0.43 MPa. The average strain increased with the resection depth, from 5.11 ± 1.577 microstrain to 5.68 ± 1.87 microstrain (reach the highest points at 8 to 10 mm resection depth), then decreased to 4.62 ± 1.26 microstrain. Both the stress and strain were mainly distributed peripherally. Conclusion As the resection depth was increased in the tibia during TAR, the resection surface area decreased but the resection volume and stress at the surface increased. The strain at the resection surface increased first and then decreased which reached a plateau at 8 to 10 mm resection depth. The 8 to 10 mm above the tibial plafond may be the weakest region of bone support in the distal tibia, which should be avoided in the design tibial component for TAR.