Finite element analysis of the mechanical strength of a new hip Spacer

Investigation of mechanical behavior on the cement hip spacer geometry under finite element method and compression load test

Background and objective

Antibiotic cement spacers (CS) are standard treatment for periprosthetic hip infection. However, complications such as cement spacer fracture and spacer dislocation remain common after surgery. The aim of this study is to investigate the influence of CS geometry design on mechanical strength through finite element analysis and compression load testing.

Methods

The CS model was generated using the three-dimensional engineering program, and an aluminum molding block was created. The mechanical behavior was analyzed using finite element method (static structural version 2022R1). A compression load test was employed to evaluate both fatigue failure and the ultimate failure load.

Results

The femoral neck area experiences the highest Von Mises stress (36.32 MPa) with lowest safety factor (1.37). The femoral head shows the most significant deformation. The designed CS is capable of withstanding repetitive loads of 35-50 kg for a total 600,000 cycles. The ultimate load to failure was 4354 N. The fracture analysis reveals a vertical sharing type at the femora neck and transverse-short oblique type at the proximal stem.

Conclusion

The designed CS can withstand the majority of daily activities with 50 % partial weight bearing for patients weighing 70-100 kg. The femoral neck area experiences the highest stress and shear strain. To optimize the geometric design of the CS, the increase in femoral neck-shaft angle and maximizing the femoral neck diameter should be consider.