The structure of the human subchondral plate

Area of Science:

• Orthopedic research
• Joint anatomy
• Biomaterials science

Background:

• Understanding the subchondral bone and cartilage interface is crucial for joint health.
• Degenerative joint diseases affect the integrity of articular cartilage and underlying bone.

Purpose of the Study:

• To investigate the anatomical relationship between human subchondral bone and articular cartilage.
• To characterize the tidemark's morphology and its association with cartilage lesions.

Main Methods:

• Human shoulder, hip, and knee specimens were processed using papain digestion, decalcification, or bleach maceration.
• Scanning electron microscopy (SEM) was employed for detailed anatomical analysis.
• Papain selectively removed cartilage to the tidemark, while decalcification exposed the bone-calcified cartilage interface.

Main Results:

• Papain digestion revealed a highly variable tidemark contour, with irregularities correlating with degenerative lesions, especially in peripheral, non-weight-bearing zones.
• Collagen fibrils of articular cartilage did not interdigitate with those of the subchondral bone.
• Subchondral bone was generally thin, avascular, and smooth, with rare perforations through it or the calcified cartilage.

Conclusions:

• The tidemark's variability suggests a complex interaction between cartilage degeneration and joint anatomy.
• The lack of collagen interdigitation highlights distinct structural properties of cartilage and bone.
• Bleach maceration is unsuitable for detailed SEM analysis of this interface.