Functional Assessment of Human Articular Cartilage Using Second Harmonic Generation (SHG) Imaging: A Feasibility...

Area of Science:

• Biomedical Engineering
• Optical Imaging
• Orthopedics

Background:

• Contact-based arthroscopic tools face limitations in narrow joint spaces.
• Second harmonic generation (SHG) laser imaging provides a non-invasive, non-contact alternative.
• Systematic validation of SHG measures for cartilage quality assessment is lacking.

Purpose of the Study:

• To investigate the feasibility of SHG microscopy-derived image measures for objective cartilage quality evaluation.
• To correlate SHG imaging parameters with established mechanical testing assessments of cartilage quality.

Main Methods:

• Human tibial plateaus were analyzed using indentation stiffness (E_inst) and streaming potential quantitative parameters (QP).
• SHG microscopy was employed to derive image-based measures, including volumetric fraction of organised collagenous network (Φ_col) and coefficient of variation of SHG intensity (CV_SHG).
• Correlation and logistic regression analyses were used to evaluate the correspondence between electromechanical properties and SHG measures.

Main Results:

• Φ_col showed strong correlations with E_inst (ρ=0.97) and QP (ρ=-0.89).
• CV_SHG exhibited weaker correlations with E_inst and QP (|ρ|=0.52-0.58).
• Φ_col and E_inst were the most sensitive predictors of cartilage quality, outperforming cell viability and tissue thickness.

Conclusions:

• SHG-based image measures, particularly Φ_col, provide an objective and effective approach for assessing cartilage quality.
• This method correlates strongly with cartilage electromechanical properties, supporting its use in developing advanced SHG-based arthroscopy.
• Traditional measures like cell viability and tissue thickness are poor predictors of cartilage quality compared to SHG-derived parameters.