Influence of radial clearance on Tresca stress in Al<sub>2</sub>O<sub>2</sub>-on-Al<sub>2</sub>O<sub>3</sub> bearings for total hip prosthesis evaluated using finite element analysis.

Abstract

Ceramic materials have gained prominence as advanced alternatives to metals and polymers in total hip prosthesis, owing to their superior wear resistance, chemical inertness, and minimal ion release. Among ceramic biomaterials, aluminum oxide (Al₂O₂) is particularly favored for its exceptional hardness, high compressive strength, and excellent tribological performance, outperforming other candidates such as zirconium dioxide (ZrO₂) and silicon nitride (Si₂N₄). However, the inherently brittle nature of ceramics necessitates careful stress analysis to mitigate fracture risks in ceramic-on-ceramic bearing systems. This study investigates the influence of radial clearance as a key geometric parameter on the mechanical safety of Al₂O₂-on-Al₂O₃ bearings by analyzing Tresca stress distributions under physiologically representative loading conditions. A 2D axisymmetric finite element model was developed to simulate the internal stress behavior of the bearing components during a full gait cycle. Six radial clearance values, ranging from 0.03 to 0.3 mm, were systematically evaluated to determine their effect on internal shear stress patterns. The simulation results demonstrate that a radial clearance of 0.03 mm yields the lowest Tresca stress, indicating a more favorable stress distribution and reduced risk of shear-induced fracture. Conversely, larger clearances were associated with elevated shear stresses, which could compromise the mechanical integrity of the ceramic components over time. These findings highlight the importance of precise control over radial clearance during the design and manufacturing of ceramic-on-ceramic hip implants. The study provides foundational insights for optimizing implant geometry to enhance the structural reliability and clinical longevity of ceramic-bearing total hip prostheses.