2022, Vol. 26 ›› Issue (6): 838-842

Mechanical stability of Sanders II type calcaneal fractures fixed by two internal fixation methods

Wen Mingtao1, Liang Xuezhen1, Li Jiacheng1, Xu Bo1, 2, Li Gang1, 2   

Abstract: BACKGROUND: For Sanders type ii calcaneal fractures, the “L-shaped” incision with locking plate internal fixation often causes complications such as necrosis of the surgical incision flap. The internal fixation with hollow screws after prying and resetting can well avoid this problem, but there is still a lack of evaluation of the effect of internal fixation.  
OBJECTIVE: To compare and study the fixation effect and mechanical stability of the two fixation methods for Sanders II type calcaneal fractures based on the finite element analysis method.
METHODS: One male volunteer (25 years old, height 175 cm, weight 75 kg) was screened, and a full-thickness continuous scan was performed from the middle part of the tibia to the whole foot by tomographic CT scan. Based on CT scan data, a complete three-dimensional finite element analysis model of the calcaneus was established. The Sanders II type calcaneal fracture was simulated, and locking plate fixation (locking plate group) and hollow screw compression fixation (hollow screw group) were performed after prying reduction. The stress distribution, displacement and fracture displacement performance of the two fixation methods were compared under the same constraints and loads on the two sets of models.  
RESULTS AND CONCLUSION: (1) The stress of hollow screw internal fixation was concentrated near the fracture line contact, and maximum Von Mises stress reached 53.948 MPa. The displacement of the horizontal hollow screw was larger than that of the longitudinal screw, and the maximum displacement was up to 0.175 37 mm. The fixed stress and displacement of the locking steel plate were concentrated near the screw hole in the middle of the steel plate. The maximum Von Mises stress reached 129.95 MPa. The fracture line displacement of the hollow screw group (0.015 77 mm) was smaller than that of the locking plate group (0.021 03 mm). (2) The maximum stress of the two sets of internal fixation was lower than the yield strength of the material. (3) The two groups of calcaneal models had the largest displacement near the subtalar joint. (4) It is concluded that hollow screws and locking plate internal fixation for the treatment of Sanders II type calcaneal fractures have good stability. Pry reduction hollow screw internal fixation has the advantages of reducing postoperative complications. It is the recommended method of internal fixation for Sanders II type calcaneal fractures.

Key words:calcaneal fracture, Sanders type II fracture, internal fracture fixation, finite element analysis, biomechanics