OPTIMISATION OF OSTEOCHONDRAL ALLOGRAFT TISSUES FOR TRANSPLANT

Tom Link, Karina Wright* and Martyn Snow*

* Denotes joint last author.

Funded by the Orthopaedic Institute

Damage to the cartilage and underlying bone of the knee is a common and serious problem, particularly in young and active people. Cartilage provides a smooth, protective surface that allows joints to move with minimal friction while also helping to absorb impact during everyday activities such as walking and running. Unlike many other tissues in the body, cartilage has very limited ability to repair itself once damaged. When both the cartilage and the bone beneath it are injured, a condition known as an osteochondral defect occurs. These injuries can cause long-term pain, swelling, reduced movement, and may eventually lead to the early development of osteoarthritis.

For large osteochondral defects, one of the most effective treatments is osteochondral allograft transplantation (see picture insert). This procedure involves transplanting healthy cartilage and bone from a deceased donor into the damaged area of the patient’s knee. Osteochondral allografts are the only treatment that can provide an immediate structural repair and, when successful, can restore joint function and delay or prevent the need for joint replacement. In countries such as the United States, this technique has been used successfully for many years and has helped tens of thousands of patients return to daily activity and sport. In the United Kingdom, osteochondral allografts were approved for routine use within the NHS in 2022, increasing access to this treatment for suitable patients.

Unlike the United States, the UK does not currently provide clinical-grade osteochondral grafts. Instead, all grafts used in UK patients are sourced from tissue banks in the United States and transported across the Atlantic. Although these grafts are carefully prepared and stored in special nutrient solutions, early work from this PhD has shown that the tissue arriving in UK clinics can already have reduced cell viability. This is important because the living cartilage cells, known as chondrocytes, play a critical role in maintaining the strength and durability of the graft once it is implanted. These early findings highlight the need for further research to understand why cartilage cell health is reduced during storage and transport to the UK, and how these processes might be improved to preserve graft quality.

Chondrocytes are responsible for maintaining the cartilage structure by producing and repairing the tissue that gives cartilage its strength and resilience. If too many of these cells die before the graft is implanted, the biological quality of the tissue may be compromised, even if it appears intact during surgery. Loss of cell health may therefore reduce the long-term success of the transplant and increase the risk of graft failure or early joint degeneration.

This PhD project investigates how storage and transport conditions affect osteochondral allograft health, with a particular focus on the biological environment within the cartilage. The research examines how factors such as time in storage, transport environment, nutrient availability, and the accumulation of metabolic waste products influence cell survival. By analysing these changes, the project aims to identify mechanisms that contribute to cell death during the graft’s journey from donor to patient.

By improving understanding of how osteochondral tissue changes before implantation, this research aims to inform the development of improved storage and transport strategies. Ultimately, the goal is to help ensure that patients in the UK receive grafts of the highest possible biological quality, improving the reliability of osteochondral allograft transplantation and supporting better long-term outcomes for individuals with severe knee injuries.