Subchondral drillings for articular cartilage defects usually result in fibrocartilage repair, which is inferior biomechanically compared to hyaline cartilage. We postulate that intra-articular injections with autologous marrow-derived stem cells (MSC) and hyaluronic acid (HA) can improve the quality of repair cartilage.

We tested this hypothesis in a goat model by creating an articular cartilage defect in the stifle joint and conducted subchondral drillings. The animals were divided into three groups: Group A (control) no injections, Group B (HA) weekly injection of 1 ml sodium hyaluronate for three weeks, Group C (HA+MSC) similar to Group B but with 2 mls autologous MSC in addition to HA. MSC were obtained by bone marrow aspiration, centrifuged, and divided into aliquots, which were cryopreserved. Fifteen animals were equally divided between the groups and sacrificed at 24 weeks after surgery where the joint was harvested and examined macroscopically and histologically.

Of the 15 animals, two had died in Group A and one was excluded from Group C due to an infection. In Group A, repair constituted mainly of scar tissue, while in Group B, there was less scar tissue, with small amounts of proteoglycan and collagen II at the osteochondral junction. In contrast, repair cartilage from Group C animals demonstrated almost complete coverage of the defect with evidence of hyaline cartilage regeneration. Histology as assessed by Gill scoring was significantly better in Group C with one-way ANOVA giving an F-statistic of 10.611 with a p-value of 0.004, which was highly significant.

Post-operative intra-articular injections of autologous MSC in combination with HA following subchondral drillings into chondral defects resulted in better cartilage repair.