Increased conformity offers diminishing returns for reducing total knee replacement wear

Area of Science:

• Biomedical Engineering
• Orthopedic Surgery
• Materials Science

Background:

• Wear is a primary failure mode for total knee replacements (TKRs), significantly limiting their longevity.
• Optimizing TKR component conformity could reduce wear, but the ideal conformity levels and planes remain under-investigated.
• Differential conformity between medial and lateral compartments offers potential for simultaneous wear reduction and kinematic optimization.

Purpose of the Study:

• To computationally investigate the impact of varying sagittal and coronal conformity on TKR wear.
• To determine the optimal conformity strategies for minimizing wear in total knee replacements under simulated gait conditions.

Main Methods:

• Utilized a computational model simulating a Stanmore knee simulator and a validated wear model.
• Created and tested various TKR geometries with differing medial and lateral sagittal and coronal conformity levels.
• Employed a two-phase approach: broad exploration followed by focused investigation on sensitive parameters.

Main Results:

• Sagittal conformity, but not coronal conformity, significantly affected predicted wear volume in the initial phase.
• Increased sagittal conformity non-linearly decreased predicted wear volume, with diminishing returns at higher conformity levels.
• Moderate to high sagittal conformity demonstrated the most significant wear reduction benefits.

Conclusions:

• TKR design efforts to minimize wear should prioritize sagittal conformity over coronal conformity.
• Implementing moderate to significant sagittal conformity in both medial and lateral compartments is recommended for enhanced TKR longevity.