Comparison of Different Methods of Semiquantitative Assessment and Subjective Scores for Retropatellar Articular Cartilage Evaluation in Advancing Osteoarthritis.

Background: cartilage layer thickness, composition of the extracellular matrix (ECM), geometry and configuration of retropatellar cartilage partially differ significantly from those found at other locations and are essential for patellofemoral biomechanics.

Material and methods: 119 serial medial and lateral patella facet samples of patients undergoing implantation of a total knee endoprosthesis of areas showing mild (Group A, macroscopically ICRS Grade 1b) respectively advanced (Group B, macroscopically ICRS Grade 3a/3b) (38 each) osteoarthritis according to the histological-histochemical grading system (HHGS) were compared with 22 healthy biopsies by means of immunohistochemistry and histology investigations. We quantified our results on the gene expression of collagen type I and II and aggrecan with real-time (RT)-PCR rsp using colourimetry for proteoglycan content. The digitized images of histology and immunohistochemistry staining with Safranin O, Alcian blue, PAS, Masson Goldner, immunostaining, e.g. for collagen I and II were also analyzed with Photoshop software.

Results: The most significant decrease in staining intensity was revealed for Safranin-O staining in Group B at the lateral patellar facet, and the most relevant increase was for Col I staining at the same site. The lateral patella site in Group B also showed the highest increase in the ratio of expression indices for the genes Col1A1 and the reference gene following the equation 2-ΔCt with a quotient of 29.6.

Conclusions: 1. Comparisons of our retropatellar cartilage analysis with femoral and tibial studies utilizing similar techniques show significant differences. 2. Cartilage layer thickness, ECM composition, geometry and configuration are essential for patellofemoral biomechanics. 3. Consequently, there is a need for diversified approaches towards retropatellar surface during TKA as well as for advanced cartilage restoration techniques.