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Critical Size Defect in Adult Articular Cartilage: A Preclinical Study.
Ernst B Hunziker1, Nahoko Shintani1, Marius J B Keel2,3
1Department of Plastic and Hand Surgery, Inselspital, Bern University Hospital, Bern, Switzerland.
Cartilage
|February 26, 2026
Summary
Partial-thickness defects (PTDs) in adult articular cartilage do not heal spontaneously, even small ones. Mesenchymal tissue formation occurs in very narrow PTDs but does not lead to true repair.
Area of Science:
- Orthopedics
- Regenerative Medicine
- Biomedical Engineering
Background:
- Articular cartilage lesions, like those from osteoarthritis, can be partial-thickness defects (PTDs) if they don't reach subchondral bone.
- PTDs are generally considered non-healing, though minor defects may show some repair.
- A hypothesis proposed a critical PTD size below which spontaneous healing occurs.
Purpose of the Study:
- To investigate the existence of a critical PTD size for spontaneous healing in adult articular cartilage.
- To determine if PTDs below a certain width can self-repair.
Main Methods:
- Adult pigs were used to create PTDs of varying widths, from minimal cuts to 0.5 mm.
- Defects were analyzed at 1 and 3 months post-surgery using light microscopy and histomorphometry.
- The study assessed spontaneous healing and tissue formation within the defects.
Main Results:
- No PTDs healed via repair cartilage, indicating all are of critical size.
- Significant mesenchymal tissue (MT) formation was observed in defects 50-100 μm wide, but only at 1 month.
- Joint loading caused tissue deformation, leading to potential pseudo-closure of small defects, masking them from above.
Conclusions:
- There is no critical width below which partial-thickness defects undergo spontaneous repair.
- Mesenchymal tissue formation in narrow defects does not constitute true healing.
- Understanding PTD behavior is crucial for developing effective cartilage repair strategies.
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