Correlation of dynamic impact testing, histopathology and visual macroscopic assessment in human osteoarthritic cartilage.

Objective: Improved staging of cartilage degeneration is required, particularly during the early stages. We correlated mechanical properties with histological and macroscopic findings.

Methods: One hundred and twenty cartilage samples were obtained during total knee arthroplasty. Two adjacent plugs were harvested--one for histological classification and one for macroscopic and biomechanical purposes. Dynamic impact testing was performed; normal stress, dissipated energy (∆E), tangent modulus and stiffness were evaluated.

Results: Samples were classified according to six categories of the ICRS histological scale. Mechanical characteristics revealing significant differences between the groups (p < 0.01) were specific damping and related absolute ∆E. A significant correlation was found between the macroscopic score and specific damping, as well as absolute and relative ∆E (p < 0.01). A strong relation was revealed between relative ∆E and cartilage thickness (p < 0.001; R (2) = 0.69).

Conclusions: Only ∆E correlated with the condition of the cartilage--the value increased with decreasing quality-and is the most suitable characteristic. This change appears substantial in initial stages of cartilage deterioration.