Introduction: Incomplete removal of calcified cartilage appears to be associated with suboptimal repair tissue attachment. Furthermore, histologic evaluation of arthroscopically debrided chondral lesions demonstrated that removal of calcified cartilage was not obvious using standard arthroscopic equipment. The purpose of this study was to compare chondral healing with and without removal of calcified cartilage in experimentally created chondral defects.

Methods: Twelve mature horses underwent bilateral arthroscopy of the femorotibial joints. A 1cm2 chondral lesion was made on the weight bearing surface of both medial femoral condyles. Randomly, in each horse one lesion had complete removal of the calcified cartilage layer (CCL) using curettes, and the CCL was left intact on the contralateral side. All defects were subjected to subchondral bone microfracture. At 12 months, all horses were euthanized and all femorotibial joints were harvested. MR imaging was performed in a 1.5 Tesla clinical MRI scanner. Analysis of variance was to analyze data.

Results: Gross and histomorphometric observations confirmed significantly (p< 0.05) better repair tissue at 12 months after surgery in defects where the CCL had been removed compared to defects where the CCL remained intact. MRI results revealed subjectively thinner and more incomplete repair tissue filling defects where the CCL remained intact compared to when it had been removed.

Conclusions: Based on gross, MRI and histologic findings, this study suggests that care should be taken in debridement of clinical cartilage lesions to assure complete removal of calcified cartilage.

Summary: Removal of the calcified cartilage layer significantly improves the healing of chondral defects.