Osteochondral Allograft Bending

Osteoarthritis (OA) is a degenerative joint disease which results in the degradation and loss of articular cartilage. This disease affects over 30 million US adults with prevalence continuing to increase [1, 2]. The current standard of care for advanced OA is artificial joint replacement, which has proven to be highly successful. A major limitation of artificial joint replacements, however, is the lifespan of the implant. This especially becomes an issue for younger patients living with post- traumatic osteoarthritis (PTOA) whose life expectancy exceeds that of an artificial joint replacement. PTOA refers to the onset of osteoarthritis after impact or injury to the joint, such as intraarticular fractures, meniscal tears, ligament tears, or joint dislocation, and accounts for approximately 10% of the US population living with knee OA [3].

Osteochondral allografts (OCAs) provide a promising alternative to artificial joint replacements. Fresh human donor tissue can be harvested and preserved in tissue banks before the transplantation process, replacing small articular cartilage defects up to large osteochondral lesions with OCAs [4]. Though the use of fresh OCAs has shown good clinical results [4], the prevalence of this surgical technique is limited by the need for size and curvature matching between donor and recipient anatomy, especially given the relatively short shelf-life of OCAs.

We propose a novel surgical approach in which an intact donor patellar osteochondral allograft is used to resurface the entirety of an osteoarthritic host patella. In order for this surgical procedure to be a viable option, we have designed a new type of bendable OCA (BOCA), which introduces the ability to safely bend the cartilage during surgery such that it conforms to the local curvature of the transplantation site. This can be achieved by milling grid-patterned grooves in the bone of the OCA so that the grooves just reveal the zone of calcified cartilage. The introduction of grooves could allow the articular layer to adaptively bend with evolving flexion during surgery, changing its local curvature and conforming to the recipient joint anatomy without incurring damage. The width, spacing, and number of grooves determine the amount of allowable bending and control of local curvature. Bone cement, which is initially malleable and deformable before it hardens, can be added at selected spots between the allograft and remaining native bone. The knee can be articulated through various flexion angles while the bone cement hardens, eventually anchoring the allograft in its bent and conformed position. The use of BOCAs can eliminate the need for careful curvature matching between the allograft and the recipient joint. This can increase the number of available allografts for transplantation and provide a more readily accessible OA treatment as an alternative to total joint replacements.

We have successfully demonstrated the cutting of grooves in osteochondral allografts harvested from the human distal femoral trochlea, and bending of these grooved OCAs to match the curvature of the trapezium articular surface in the thumb carpometacarpal (CMC) joint, for the treatment of OA in that joint. We designed, manufactured, and patented a new surgical tool for the allograft bending and have initiated a clinical trial for this surgery.

[1] CDC (website), https://www.cdc.gov/arthritis/basics/osteoarthritis. htm. [2] CDC & Arthritis Foundation, National Public Health Agenda for OA, 2010. [3] Brown, T.D. et al., J. of Ortho. Trauma, 20:739-744, 2006. [4] De Caro, F. et al., Arthro.: J. of Arthro. & Related Surgery, 31:757-765, 2015.