Maturation process of regenerated tissues after single-stage simultaneous autologous particulated cartilage implantation and open wedge high tibial osteotomy for articular cartilage defects with medial osteoarthritis of bilateral knees: a case report

BACKGROUND: Open wedge high tibial osteotomy (OWHTO) is an effective treatment option for young and middle-aged active patients with medial unicompartmental knee osteoarthritis (OA). In addition, particulated cartilage implantation has been developed as a simple procedure for cartilage regeneration. Thus, to improve the OWHTO outcomes, a single-stage, simultaneous bilateral knee arthroscopic particulated cartilage implantation with OWHTO was performed. CASE PRESENTATION: A 60-year-old male patient presented with severe bilateral knee pain, with grade 2 varus knee OA of the Kellgren–Lawrence classification. Primary arthroscopic evaluations based on the International Cartilage Repair Society grading system showed grade 3c articular cartilage defects of 1.5 cm in diameter at the center of the bilateral medial femoral condyles. Following bilateral OWHTO, the healthy cartilage tissue was harvested from the lateral wall of the unilateral femoral intercondylar notch and minced with the cartilage processor. Then, subchondral drillings and cartilage fragment implantations into the bilateral defects were performed arthroscopically. One year postsurgery, second-look arthroscopy findings revealed that the defects were filled with cartilage-like tissues. The maturation process of the regenerated tissues was confirmed with T2 mapping magnetic resonance imaging during the 3-year follow-up period. The patient could walk without a cane, and all Knee Injury and Osteoarthritis Outcome Score parameters were improved without any correction loss in 3 years. CONCLUSIONS: This is the first report to evaluate the maturation process of the implanted particulated cartilage tissue with T2 mapping magnetic resonance imaging for 3 years. The effect of chondral resurfacing procedure with OWHTO remains unclear; however, the implantation of arthroscopic particulated cartilage fragments is a single-stage and less-invasive procedure. This treatment could regenerate cartilage-like tissue in the present case. Therefore, this additional procedure could potentially improve the long-term outcomes of OWHTO.