# Friction and Cartilage Wear in Hemiarthroplasty: A Systematic Review of Key Influencing Factors

## TL;DR

This review examines how friction and wear in hemiarthroplasty are influenced by factors like material and testing conditions.

## Contribution

The study systematically evaluates whether friction reliably predicts cartilage wear in hemiarthroplasty materials.

## Key findings

- Coefficient of friction (COF) increases with testing time but only partially explains wear variability.
- Contact stress correlates with COF and wear, while velocity and distance effects are inconsistent.
- Predictive models for wear using COF show poor fit, indicating COF alone is an unreliable predictor.

## Abstract

Hemiarthroplasty addresses joint damage confined to one side, preserving native cartilage and bone, but accelerated degeneration of the opposing cartilage can compromise outcomes. This systematic review should clarify whether coefficient of friction (COF) reliably predicts cartilage wear when evaluating hemiarthroplasty bearing materials (HBMs). Thirty in vitro studies reporting both outcomes were identified. Data were extracted on COF, wear, and testing parameters, and wear was standardized using a 0–4 rubric to enable cross-study comparison. Three analytical approaches were applied: linear model fits, Pearson’s correlations, and predictive modeling. Reported COFs increased significantly with testing time, while contact stress and sliding velocity showed variable associations with COF. Predictive models for cobalt–chromium (CoCr), the most studied HBM, showed moderate fit, suggesting that mechanical parameters explain only part of COF variability. For wear, linear models showed poor fit with COF, but correlations indicated positive associations with contact stress. Inconsistent effects of velocity and distance were found. Predictive models explained little variability. Together, these findings suggest that outcomes are strongly influenced by testing conditions, lubricants, and HBM selection, and COF alone is an unreliable predictor of cartilage wear in an experimental setting.