Comparative Matched-Pair Analysis of the Injection Versus Implantation of Mesenchymal Stem Cells for Knee Osteoarthritis

Background: The mesenchymal stem cell (MSC)–based tissue engineering approach has been developed to address the problem of articular cartilage repair in knee osteoarthritis (OA). However, the most effective method of MSC application has not yet been established. Purpose: To compare the injection and implantation of MSCs in patients with knee OA in terms of clinical and second-look arthroscopic outcomes. Study Design: Cohort study; Level of evidence, 3. Methods: Among 182 patients treated with arthroscopic surgery using MSCs for knee OA from October 2010 to August 2012, patients treated with an injection of MSCs in combination with platelet-rich plasma (injection group; n = 20) were pair-matched with patients who underwent MSC implantation on a fibrin glue scaffold (implantation group; n = 20) based on sex, age, and lesion size. Clinical outcomes were evaluated using the International Knee Documentation Committee (IKDC) score and Tegner activity scale, and cartilage repair was assessed arthroscopically with the International Cartilage Repair Society (ICRS) grading system. Results: The mean (±SD) IKDC and Tegner activity scores significantly improved from 38.5 ± 9.2 to 55.2 ± 15.0 and from 2.5 ± 1.2 to 3.5 ± 1.2, respectively, in the injection group and from 36.6 ± 4.9 to 62.7 ± 14.1 and from 2.3 ± 0.9 to 3.6 ± 1.1, respectively, in the implantation group at the time of second-look arthroscopic surgery (mean, 12.6 months postoperatively) ( P < .001 in all cases). At final follow-up (mean, 28.6 months postoperatively), the mean IKDC and Tegner activity scores in the implantation group had improved further to 64.8 ± 13.4 and 3.9 ± 1.0, respectively ( P < .001 and P = .035, respectively), while no significant improvements were found in the injection group ( P = .130 and P = .655, respectively). At final follow-up, there was a significant difference in the mean IKDC score between groups ( P = .049). Significant correlations between the number of administered MSCs and the postoperative clinical outcomes were found only in the injection group. Significant correlations between the clinical outcomes and the ICRS grades were found in both groups. The ICRS grades were significantly better in the implantation group ( P = .041). In the injection group, 2 of the 20 lesions (10%) were grade I (normal), 5 (25%) were grade II (near normal), 8 (40%) were grade III (abnormal), and 5 (25%) were grade IV (severely abnormal). In the implantation group, 6 of the 20 lesions (30%) were grade I, 7 (35%) were grade II, 4 (20%) were grade III, and 3 (15%) were grade IV. Conclusion: Utilizing the described method, MSC implantation for knee OA resulted in better clinical and second-look arthroscopic outcomes than an MSC injection.