Quantifying birefringence in the bovine model of early osteoarthritis using polarisation-sensitive optical coherence tomography and mechanical indentation

TL;DR

This study demonstrates that polarisation-sensitive optical coherence tomography (PS-OCT), combined with mechanical indentation, can detect and quantify early osteoarthritic changes in cartilage by measuring birefringence differences.

Contribution

The paper introduces a novel method combining PS-OCT with mechanical indentation to quantify early cartilage degeneration, advancing non-invasive osteoarthritis detection.

Findings

PS-OCT detects significant birefringence differences between healthy and early osteoarthritic cartilage

Mechanical indentation enhances the visibility of birefringent patterns in cartilage

Quantitative birefringence measurement correlates with cartilage health status

Abstract

Recent studies have shown potential for using polarisation sensitive optical coherence tomography (PS-OCT) to study cartilage morphology, and to be potentially used as an in-vivo, non-invasive tool for detecting osteoarthritic changes. However, there has been relatively limited ability of this method to quantify the subtle changes that occur in the early stages of cartilage degeneration. An established mechanical indenting technique that has previously been used to examine the microstructural response of articular cartilage was employed to fix the bovine samples in an indented state. The samples were subject to creep loading with a constant compressive stress of 4.5 MPa and, when imaged using PS-OCT, enabled birefringent banding patterns to be observed. The magnitude of the birefringence was quantified using the birefringence coefficient (BRC) and statistical analysis revealed that PS-OCT is able to detect and quantify significant changes between healthy and early osteoarthritic cartilage (p<0.001). This presents a novel utilization of PS-OCT for future development as an in-vivo assessment tool.