Cell-seeded Autologous Chondrocyte Implantation (cs-ACI) - A Simplified Implantation Technique with Maintained Clinical Outcomes

OBJECTIVES: The objective of this study was to investigate whether outcomes and failure rate of a simplified ACI technique (cs-ACI) were comparable to those of the more complicated traditional technique of a chondrocyte suspension injected under membrane cover (cACI). METHODS: Patients were treated with cACI prior to February 2010. After this date the senior author switched to the cs-ACI technique for all patients. For the cs-ACI technique, cultured chondrocytes were seeded in the OR onto a collagen membrane, which was subsequently placed into the cartilage defect and secured with a running suture and/or fibrin glue. Thirty-nine patients treated with the cs-ACI technique fulfilled the inclusion requirements of minimum 2 year follow-up and complete data set. A comparison group was composed of 45 patients treated prior to the switch date with standard ACI (cACI) in which a suspension of cultured chondrocytes was injected into a debrided chondral defect underneath a sutured collagen cover. Prospectively collected data were retrieved from our IRB-approved database. Both groups followed an identical post-operative protocol. The outcomes were measured with the 12-Item Short-Form Health Survey (SF-12), International Knee Documentation Committee (IKDC) score, Knee injury and Osteoarthritis Outcome Score (KOOS), Lysholm knee scale, and Tegner activity scale. We defined failure as any graft removal of more than 25% of the original defect size, for example through revision with allograft or arthroplasty. Mann-Whitney U tests were used to compare mean scores between groups preoperatively and at the latest follow-up; chi-square test was used to detect differences between groups. Graft survivorship was calculated by the Kaplan-Meier method, and distributions were compared using the log rank test. RESULTS: Group demographics were not significantly different, except for defect size (Table 1) and average follow-up: 4 years in the cACI group and 2.5 years in the cs-ACI group. Significant improvements were seen in all scores except Tegner from the pre-operative baseline to the latest follow-up for both groups; however, no significant difference was found between groups at the latest follow-up. Failure rate at 2 years was not significantly different, while total failure rate over the entire study period was significantly lower in the cell-seeded group (cs-ACI) (5% versus 24%). The difference in Kaplan-Meier survivorship (Figure 1) failed to reach significance. CONCLUSION: Both ACI techniques demonstrated statistically significant and clinically meaningful improvements in patient reported outcomes that were not different between groups. Follow-up time was shorter in the cell-seeded technique, as patients in this group were treated more recently. The absolute failure rate was significantly lower in the simplified, cell-seeded technique with 5% versus 24% with the traditional technique. However, this should be interpreted in context of the shorter follow-up time and smaller defect size in the cell-seeded group, both favoring a lower failure rate. Overall, this study demonstrated that a simplified ACI technique maintained the same patient reported outcomes of a more complicated traditional technique without increases in failure.