The Effects of Lesion Size and Location on Subchondral Bone Contact in Experimental Knee Articular Cartilage Defects in a Bovine Model

Purpose: To determine how femoral condyle chondral defect size and location influence subchondral bone contact within the defect. Methods: Full-thickness, circular chondral defects (0.2 to 5.07 cm(2)) were created in 9 healthy bovine knees. Knees were loaded to 1,000 N, and subchondral bone contact area measurements were recorded with a Tekscan sensor and I-Scan software (Tekscan, Boston, MA). A MATLAB program (The MathWorks, Natick, MA) was designed to compute defect area and the area within the defect showing subchondral bone contact. One-sample t tests with Bonferroni correction were performed for medial and lateral defects at each defect size to determine when statistically significant (P < .05) contact occurred; the smallest defect size exhibiting significant contact was considered a threshold area. Results: The threshold at which significant subchondral bone contact occurred was different for medial and lateral defects. Contact within all defects was not observed below a defect area of 0.97 cm(2). The threshold at which significant (P < .05) contact occurred was 1.61 cm(2) and 1.99 cm(2) for lateral and medial condyle defects, respectively. Conclusions: Subchondral bone contact within experimental femoral condyle chondral defects is dependent on defect size and intra-articular location. In our bovine model, lateral condyle defects have significant subchondral bone contact at a smaller defect size than medial defects. Clinical Relevance: Current algorithms use size as a primary factor in management of chondral defects of the knee. Although the consequences of subchondral bone contact on femoral condyle articular cartilage defect progression are unknown, the results of this study supplement current algorithms and suggest consideration of defect location, in addition to size, in the management of chondral defects of the knee.