A methodology for the quantitative assessment of articular cartilage histomorphometry

Objective: Traditionally, histological analysis of cartilage and cartilage repair has been performed qualitatively. While new techniques and grading systems have attempted to improve the quantitative nature of histological assessment, the advent of computer-based analysis systems have enabled development of more quantitative methodologies for cartilage repair. The objective of this study was to develop such a methodology for a more quantitative assessment of cartilage repair using a color-based image analysis system. Design: Repair parameters were defined to describe the degree of cartilage restoration: repair dimensions, degree of attachment, surface roughness and repair location. This technique was experimentally applied to a cartilage repair study using cultured perichondrial cells implanted in a polylactic acid matrix in the rabbit femoral condyle. Specimens were examined and compared with the contralateral normal knee. Results: Results showed increases in cartilage height, repair area, and surface roughness over controls for both 6 and 12 weeks. Surface elevation was significantly decreased at 6 weeks over 12 weeks. The percentage of repair improved between 6 and 12 weeks. Results were compared with a traditional grading system and demonstrated close correlation. Intraobserver and interobserver precision analysis were performed and demonstrated the reproducibility of the quantitative results by and between individuals. Conclusions: The methodology was deemed successful for a more objective analysis of cartilage with the added advantage of providing measured parameters that can assist in making comparisons between different studies using the same methodology.