Autologous Cartilage Chip Transplantation Improves Repair Tissue Composition Compared With Marrow Stimulation

Background: Repair of chondral injuries by use of cartilage chips has recently demonstrated clinical feasibility. Purpose: To investigate in vivo cartilage repair outcome of autologous cartilage chips compared with marrow stimulation in full-thickness cartilage defects in a minipig model. Study Design: Controlled laboratory study. Methods: Six Gottingen minipigs received two 6-mm chondral defects in the medial and lateral trochlea of each knee. The two treatment groups were (1) autologous cartilage chips embedded in fibrin glue (ACC) (n = 12) and (2) marrow stimulation (MST) (n = 12). The animals were euthanized after 6 months, and the composition of repair tissue was quantitatively determined using histomorphometry. Semiquantitative evaluation was performed by means of the International Cartilage Repair Society (ICRS) II score. Collagen type II staining was used to further evaluate the repair tissue composition. Results: Significantly more hyaline cartilage was found in the ACC (17.1%) compared with MST (2.9%) group (P < .01). Furthermore, the ACC group had significantly less fibrous tissue (23.8%) compared with the MST group (41.1%) (P < .01). No significant difference in fibrocartilage content was found (54.7% for ACC vs 50.8% for MST). The ACC group had significantly higher ICRS II scores for tissue morphological characteristics, matrix staining, cell morphological characteristics, surface assessment, mid/deep assessment, and overall assessment (P < .05). The ACC-treated defects had significantly more collagen type II staining (54.5%) compared with the MST-treated defects (28.1%) (P < .05). Conclusion: ACC transplant resulted in improved quality of cartilage repair tissue compared with MST at 6 months postoperatively. Clinical Relevance: Further studies are needed to investigate ACC as a possible alternative first-line treatment for focal cartilage injuries in the knee.