Different screw configurations for treating Sanders type IIB intra-articular calcaneal fractures: a finite element analysis

BACKGROUND AND OBJECTIVE: Percutaneous screw fixation (PSF) technique is widely used in treating displaced intra-articular calcaneal fractures (DIACFs), the optimal screw configuration remains controversial. In this study, a finite element analysis (FEA) was conducted to compare the biomechanical properties of five different screw configurations in the fixation of Sanders type ⅡB calcaneal fractures, aiming to provide a reference for clinical strategy selection. METHODS: In this study, models of five different screw configurations for the fixation of Sanders type IIB calcaneal fractures were constructed. After assigning material properties and applying stress, the maximum displacement and von Mises stress distribution of bone fragments and implants in each group were recorded and compared through FEA. RESULTS: After loading, the maximum displacement and von Mises stress of the bone fragments in the five models were recorded as follows: Model 1 (0.369 mm, 39.803 MPa), Model 2 (0.335 mm, 42.283 MPa), Model 3 (0.297 mm, 39.079 MPa), Model 4 (0.315 mm, 33.770 MPa), and Model 5 (0.415 mm, 41.095 MPa). The maximum displacement and stress of the screws were recorded as: Model 1 (0.286 mm, 34.439 MPa), Model 2 (0.277 mm, 35.489 MPa), Model 3 (0.233 mm, 60.152 MPa), Model 4 (0.247 mm, 38.725 MPa), and Model 5 (0.330 mm, 46.806 MPa), Model 3 exhibiting the best mechanical performance, while Model 5 showed the least favorable performance. CONCLUSIONS: FEA results demonstrate that the use of multiple sustentaculum tali screws and a "kickstand" screw to enhance fixation of the posterior articular surface, along with longitudinal screws inserted superior to the Achilles tendon insertion contributed to stability. The longitudinal screws inserted from the calcaneal tuberosity provide relatively poor stability. Additionally, reinforcing the fixation of the medial column of the calcaneus enhances stability.