Abstract

Background/Objectives: Fracture of ceramic femoral heads in total hip arthroplasty is a rare but catastrophic complication requiring urgent revision surgery. Most finite element studies are limited to static loading and do not capture dynamic behavior under impact conditions from stumbling or falling. The objective was to determine impact fracture thresholds of alumina (Al2O3) and yttria-stabilized zirconia (ZrO2, Y-TZP) femoral heads using explicit dynamic finite element analysis. Methods: A parametric explicit dynamic analysis was performed using LS-DYNA (version 960) on an axisymmetric model of a 32 mm ceramic femoral head articulating with a ceramic liner within a Ti-6Al-4V acetabular shell. Ceramic behavior was described by the Johnson–Holmquist JH-2 damage model, validated against published impact and retrieval data. Bone stock viscoelasticity was a Winkler foundation (stiffness 50–500 N/mm, damping 0–1.0 N·ms/mm). Impact velocity ranged from 0.01 to 0.45 mm/ms, consistent with implant telemetry during stumbling. Fracture criteria were plastic strain, principal stress, and energy inflection. A sensitivity analysis of estimated ZrO2 parameters was performed. Results: For Al2O3, the critical fracture velocity was 0.08 mm/ms under rigid fixation and 0.05 mm/ms with a viscoelastic foundation. The ZrO2 head did not fracture at any velocity tested; at V ≥ 0.20 mm/ms, the neck deformed plastically while the head remained intact. Foundation stiffness and damping had no influence on outcome. Conclusions: These findings indicate inertia-dominated fracture mechanics for Al2O3 at realistic velocities, and suggest a material-dependent shift in critical failure location toward the taper junction for ZrO2, a tendency warranting experimental confirmation.

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