18.3.8 - Ovine knee cartilage differs in structural and functional properties across articular surfaces
- B. Nelson (Fort Collins, US)
- B. Nelson (Fort Collins, US)
- M. Risch (Fort Collins, US)
- J. Easley (Fort Collins, US)
- E. McCready (Fort Collins, US)
- K. McGilvray (Fort Collins, US)
- K. Troyer (Fort Collins, US)
- J. Johnson (Fort Collins, US)
- J. Kisiday (Fort Collins, US)
Abstract
Purpose
Articular cartilage is a critical joint tissue. Once damaged, it has limited repair potential and large efforts have gone towards investigating emerging repair strategies. Sheep are commonly used because of their ability to translate results to human orthopedic conditions, although it is not known if variation in structural and functional properties exist across the surface. Therefore, the purpose of this study is to characterize cartilage heterogeneity as a function of location in adult ovine stifles by measuring mechanical performance (creep behavior), biochemical properties (GAG content), and thickness across the femoral condylar and trochlear surfaces.
Methods and Materials
In ten stifle (knee) joints, cartilage regions of interest (ROIs) were generated within each femoral trochlea (8 ROIs) and condyle (6 medial, 6 lateral). Each cartilage ROI was evaluated with macroindentation testing, dimethylmethylene blue assay and µCT scan to determine percent creep, GAG content and cartilage thickness, respectively. Results of each variable were mapped based upon anatomical locations and compared using a mixed model ANOVA. Significance was defined as P<0.05.
Results
For percent creep (Figure 1), ROIs within each knee location were significantly different (lateral condyle: P<0.0001; medial condyle: P<0.0001; trochlea: P=0.0004). Percent creep on the medial femoral condyle was significantly lower than the femoral trochlea and lateral condyle (both P<0.0001). For GAG content (Figure 2), there were significant differences between ROIs within the following knee locations: lateral condyle (P<0.0001), medial condyle (P=0.01) and trochlea (P<0.0001). When evaluated collectively, differences in GAG content between knee locations were not detected. Medial femoral condyle cartilage was significantly thicker than the femoral trochlea and lateral condyle (P<0.0001).
Conclusion
Cartilage mechanical properties, biochemical composition and thickness vary across distal femoral joint surfaces. Clinicians and researchers working with ovine cartilage should recognize this potential variability and standardize cartilage sites accordingly to obtain accurate results based on study goals.