Biomechanical comparison of frame configuration screw fixation and conventional plate fixation for Sanders type iii fractures: a finite element analysis

Sanders type III calcaneal fractures typically require surgical intervention. While open reduction and internal fixation (ORIF) provides robust stabilisation, it is associated with a high incidence of surgical site complications. Closed reduction with percutaneous screw fixation (CRPF) presents a lower risk of complications, but consensus on the optimal screw configuration remains elusive. In this study, a novel frame configuration screw fixation (FCSF) method is proposed, and its biomechanical properties are compared with those of conventional plate fixation through finite element analysis. CT images of the calcaneus from a healthy volunteer were acquired. Software was used to construct Sanders type III calcaneal fracture models, an ORIF model, and two FCSF models. The material properties and contact modes were assigned. Forces of 350 N and 700 N were applied to compare the stress and displacement across the different models. Under 350 N/700 N loads, the ORIF group exhibited peak implant stresses of 80.36 MPa/161.41 MPa, peak calcaneal fracture fragment stresses of 36.08 MPa/72.34 MPa, and peak calcaneal fracture fragment displacements of 0.5133 mm/1.0286 mm. Under identical loads, FCSF A and B exhibited peak internal plant stress values of 75.15 MPa/149.03 MPa and 85.92 MPa/170.79 MPa, respectively. The peak stress values in the calcaneal fracture fragment were 25.92 MPa/51.80 MPa and 30.39 MPa/60.86 MPa. The peak calcaneal fracture fragment displacements were 0.0896 mm/0.1788 mm and 0.1021 mm/0.2042 mm, respectively. FCSF outcomes comparable to those of ORIF in the treatment of Sanders type III fractures were observed, indicating that FCSF provides sufficient biomechanical stability. The configuration with a transverse screw positioned above the inner and outer longitudinal screws is the more ideal fixation approach. This study offers biomechanical support for minimally invasive screw fixation of the calcaneus.