Chondral Defects Cause Kissing Lesions in a Porcine Model

To assess the development of kissing lesions 12 months after the generation of full-thickness chondral defects.

Eight minipigs were randomized into 2 groups: the Φ8.5 mm full-thickness chondral defect group (8.5FT group) and the Φ6.5 mm full-thickness chondral defect group (6.5FT group). The Φ8.5 mm or Φ6.5 mm full-thickness chondral defects were prepared in the medial femoral condyle. Knee magnetic resonance imaging (MRI) was performed before sacrifice. India ink staining was performed to macroscopically assess kissing lesions. Histologic staining (hematoxylin-eosin [HE], safranin O/fast green, toluidine blue staining) and immunohistochemistry (collagen I, collagen II, collagen X, MMP-3) were performed. Microcomputed tomography analysis was completed to assess subchondral bone alterations.

Obvious kissing lesions were observed on the tibial plateau. Knee MRI demonstrated high cartilage signal intensity in the medial femoral condyle and opposite tibial plateau. HE staining demonstrated cartilage fibrillation and prominent cell death. The depletion of safranin O, toluidine blue staining, and collagen II was observed in the kissing lesion areas. The kissing lesion areas demonstrated increased collagen I, Collagen X, and MMP-3 expression. The 8.5FT group showed a significantly lower mean trabecular number (2.80 1/mm) than the control group (3.26 1/mm). The 6.5FT group showed a significantly increased mean trabecular thickness (0.54 mm) and a decreased mean trabecular number (2.71 1/mm) compared to the control group (0.32 mm; 3.26 1/mm).

Obvious kissing lesions were observed on the tibial plateau. Knee MRI demonstrated high cartilage signal The presented findings support the development of kissing lesions caused by full-thickness chondral defects.