Comparison of the Dynamic Cut-Out Failure Modes of Common Proximal Femoral Fixation Devices Using a Mesh-Free...

Area of Science:

• Orthopedic biomechanics
• Biomaterials engineering
• Surgical device performance analysis

Background:

• Internal fixation of intertrochanteric fractures commonly fails due to migration and cut-out.
• Understanding device performance under physiological loading is crucial for improving patient outcomes.

Purpose of the Study:

• To compare the performance of four common internal fixation devices (DHS, Gamma3, PFNA-II, TFNA) under dynamic loading.
• To evaluate the accuracy of mesh-free simulations in predicting bone foam failure patterns and device cut-out.

Main Methods:

• Benchtop testing of four hip implants in polyurethane bone foam models under static and dynamic gait-simulating loads.
• Mesh-free computational simulations of physical tests using an experimentally validated porous foam material model.
• Analysis of implant migration, cut-out resistance, and bone foam damage volumes.

Main Results:

• Blade-type implants showed better initial resistance to migration than screw-type implants under dynamic loading.
• No significant difference in overall performance was observed between devices as dynamic loading progressed.
• Simulations accurately predicted physical test outcomes (concordance correlation coefficients > 0.858).
• Simulated dynamic loading revealed substantial differences in bone damage volumes between devices, even with similar cut-out forces.

Conclusions:

• While blade implants offer initial migration resistance, no device demonstrated clear long-term superiority in this model.
• Computational simulation of material damage provides a valuable method for differentiating implant performance and guiding clinical selection.
• Accurate simulation can reveal differences in bone tissue damage not apparent from simple load-to-failure metrics.