Mesenchymal Stem Cell Implantation in Knee Osteoarthritis: An Assessment of the Factors Influencing Clinical Outcomes

Background: Several clinical studies have reported on cell-based treatment using mesenchymal stem cells (MSCs) for cartilage regeneration in knee osteoarthritis (OA). However, little is known about the factors that influence the clinical outcomes after surgery. Purpose/Hypothesis: This study aimed to investigate the clinical outcomes of MSC implantation in patients with knee OA and assess the factors that are associated with clinical outcomes. The hypothesis was that factors may exist that could influence clinical outcomes. Study Design: Case series; Level of evidence, 4. Methods: A total of 49 patients (55 knees) were retrospectively evaluated after MSC implantation for knee OA. The inclusion criteria were patients who had an isolated full-thickness cartilage lesion and Kellgren-Lawrence OA grade 1 or 2. Clinical outcomes were measured with the International Knee Documentation Committee (IKDC) score, Tegner activity score, and patients' overall satisfaction with the surgery. Statistical analyses were performed to determine the effect of different factors on the clinical outcome. Results: The mean pre- and postoperative IKDC and Tegner activity scores significantly improved from 37.7 6.3 to 67.3 +/- 9.5 (IKDC) and from 2.2 +/- 0.7 to 3.8 +/- 0.7 (Tegner) (P < .001 for both). Twenty-four patients reported their overall satisfaction with the surgery as excellent (43.6%), 17 as good (30.9%), 11 as fair (20.0%), and 3 as poor (5.5%). There were significant differences in clinical outcomes at the final follow-up among the age and lesion size groups (P < .05 for all). Multivariate analyses showed high prognostic significance related to patient age and lesion size, and scatter plots suggested a cutoff age of 60 years and a cutoff lesion size of 6.0 cm(2) for the optimum identification of poor clinical outcomes (P < .05 for both). Conclusion: The clinical outcomes of MSC implantation for knee OA are encouraging. Patient age and lesion size are important factors that affect clinical outcomes; thus, these may serve as a basis for preoperative surgical decisions. Cutoff points exist for the risk of clinical failure in patients older than 60 years and those with a lesion size larger than 6.0 cm(2).