Assessment of subchondral bone microdamage quantification using contrast-enhanced imaging techniques

Area of Science:

• Biomechanical Engineering
• Veterinary Medicine
• Materials Science

Background:

• Subchondral bone (SCB) microdamage is prevalent in athletic animals and humans due to high-impact loading.
• Microdamage significantly alters bone's biomechanical properties, necessitating accurate quantification methods.
• Existing methods for microdamage quantification in SCB are limited, especially compared to trabecular bone.

Purpose of the Study:

• To assess lead uranyl acetate (LUA) staining and contrast-enhanced microcomputed tomography (μCT) for detecting and quantifying SCB microdamage.
• To determine the specificity of LUA to microdamage and the accuracy of damaged bone volume metrics.
• To establish a reliable method for quantifying microdamage in SCB, crucial for understanding joint physiology.

Main Methods:

• SCB specimens from racehorse metacarpus were used, with and without hyaline articular cartilage (HAC).
• Specimens were subjected to ex vivo uniaxial compression or preserved for in vivo damage.
• LUA staining (modified protocol) followed by μCT and backscattered scanning electron microscopy (SEM) imaging for quantification.

Main Results:

• A modified LUA protocol enhanced label penetration into SCB.
• LUA specifically labeled microdamage, including diffuse, linear, and oblique cracks, excluding those with mineral infills.
• μCT-based labeled bone volume fraction (LV/BV) was higher without HAC; a corrected metric (LV/BV BS⁻¹) was proposed for accurate quantification.

Conclusions:

• The combination of HAC removal and a modified LUA staining protocol provides effective staining of damaged SCB.
• This technique accurately quantifies microdamage in racehorse SCB, offering a valuable tool for research.
• The developed method facilitates future investigations into the impact of microdamage on joint health and physiology.