Impact-Induced Cartilage Damage Assessed using Polarisation-Sensitive Optical Coherence Tomography

TL;DR

This study uses polarisation-sensitive optical coherence tomography to non-invasively assess immediate and post-impact structural changes in bovine cartilage, revealing potential markers for early degenerative changes and tissue response.

Contribution

It introduces a novel application of PS-OCT for evaluating impact-induced cartilage damage and recovery, highlighting its potential for clinical diagnostics.

Findings

Degenerate cartilage shows significant birefringence changes after impact.

Surface irregularity and optical attenuation are potential diagnostic markers.

Rehydration reduces birefringence reliability, indicating optical recovery.

Abstract

Significance: Non-invasive determination of structural changes in articular cartilage immediately after impact and rehydration provides insight into the response and recovery of the soft tissue, as well as provides a potential methodology for clinicians to quantify early degenerative changes. Approach: A custom-designed impact testing rig was used to deliver 0.9 J and 1.4 J impact energies to bovine articular cartilage. A total of 55 (n=28 healthy, n=27 mildly degenerate) cartilage-on-bone samples were imaged before, immediately after, and 3 hours after impact. PS-OCT images were analysed to assess changes relating to surface irregularity, optical attenuation, and birefringence. Results: Mildly degenerate cartilage exhibits a significant change in birefringence following 1.4 J impact energies compared to healthy samples which is believed to be attributable to degenerate cartilage being unable to fully utilise the fluid phase to distribute and dampen the energy. After rehydration, the polarisation-sensitive images appear to `optically-recover' reducing the reliability of birefringence as an absolute metric. Surface irregularity and optical attenuation encode diagnostically relevant information and may serve as markers to predict the mechanical response of articular cartilage.