Efficient computational method for assessing the effects of implant positioning in cementless total hip replacements

Area of Science:

• Biomechanical Engineering
• Orthopedic Surgery
• Computational Mechanics

Background:

• Initial stability is crucial for cementless total hip replacement (THR) success.
• Implant positioning is a key factor influencing initial stability and osseointegration.
• Micromotion at the bone-implant interface can impede bone ingrowth.

Purpose of the Study:

• To statistically investigate the effect of implant positioning on the initial stability of cementless THR.
• To identify optimal implant orientation angles that minimize micromotion and enhance stability.
• To quantify the sensitivity of THR performance metrics to various implant orientation angles.

Main Methods:

• Utilized mesh morphing and design of computer experiments for automated Finite Element (FE) mesh generation.
• Simulated implant micromotions under joint contact and muscle loading for various femur-implant configurations.
• Employed a Bayesian approach to analyze computed micromotions and determine main effects and sensitivities.

Main Results:

• Antero-posterior implant orientation showed greater sensitivity in affecting micromotion metrics compared to ante-retroversion and varus-valgus angles.
• Increased anterior positioning correlated with higher micromotions and reduced likelihood of bone growth.
• Optimal implant positioning reduced the percentage of implant area with >50 μm micromotion to 1.14% from 14.6% (worst case).

Conclusions:

• Implant positioning critically influences cementless THR initial stability and osseointegration potential.
• Antero-posterior orientation is a primary determinant of micromotion and bone ingrowth.
• The computational framework provides a robust method for optimizing implant placement in THR design.