Mega-OATS of the knee without specialised instrumentation: a low-cost option for large cartilage defects in a resource-restrained environment

BACKGROUND: A 26-year-old patient presented to a specialised knee clinic in a public hospital with ongoing pain after having sustained a soccer injury six years prior. A large osteochondral defect of the distal medial femoral condyle was diagnosed. Due to resource limitations, fresh allograft or a large osteochondral autograft transplantation system (Mega-OATS) workbench was unavailable. CASE REPORT: A Mega-OATS cartilage transplantation was done, using the patient's posteromedial femoral condyle as donor tissue, and transplanted to the defect in the distal femoral condyle, a technique that has been well documented and followed up. At six weeks postoperatively, an MRI showed early incorporation of the graft tissue. Clinical outcomes were excellent at one year follow-up with the EQ-5D 5L score 11111, the Knee Injury and Osteoarthritis Outcome Score (KOOS-PS) 100%, and the Lysholm score also 100%. Radiographs at one year confirmed an unchanged graft position and showed no signs of osteoarthritis. DISCUSSION: Large osteochondral lesions in the knee (> 4 cm2) are challenging to treat, and the most commonly used modalities are fresh osteochondral allograft (OCA) or autologous chondrocyte implantation (ACI). Mega-OATS of the knee has previously been described but is not commonly used due to the requirement of a specialised and expensive workbench, and fear of morbidity at the donor site. CONCLUSION: Mega-OATS of the knee is possible without a specialised workbench or tools and had good clinical outcomes at two-year follow-up of the patient. Level of evidence: Level 5