Simultaneous changes in the mechanical properties, quantitative collagen organization, and proteoglycan concentration of articular cartilage following canine meniscectomy

The mechanical properties and microstructure of articular cartilage from th e canine tibial plateau were studied 12 weeks after total medial meniscecto my. The organization of the birefringent collagen network was measured with quantitative polarized light microscopy to determine the thickness and the degree of organization of the superficial and deep zones. The zonal concen tration of sulfated glycosaminoglycan was quantified with digital densitome try of safranin-O staining. Equilibrium compressive and shear properties, a s well as dynamic shear properties, were measured at sites adjacent to thos e of microstructural analysis. The results evinced significant loss of cart ilage function following meniscectomy, with decreases of 20-50% in the comp ressive and shear moduli. There was no evidence of alterations in the degre e of collagen fibrillar organization, although a complete loss of the surfa ce zone was seen in 60% of the samples that underwent meniscectomy. Menisce ctomy resulted in a decreased concentration of sulfated glycosaminoglycan, and significant positive correlations were found between the equilibrium co mpressive modulus and the glycosaminoglycan content. Furthermore, the shear properties of cartilage correlated directly with collagen fibrillar organi zation measured at the superficial zone of corresponding sites. These findi ngs demonstrate that meniscectomy leads to impaired mechanical function of articular cartilage, with significant evidence of quantitative correlations between cartilage microstructure and mechanics.