A Resurfacing-Regenerative Approach to Repair Osteochondral Defects using a Bioprosthetic Device

Osteochondral defects (OCDs), areas of localized joint damage to articular cartilage and underlying subchondral bone, often lead to pain, loss of joint function, and osteoarthritis. Clinical repair is focused on biological grafting procedures, which are innately limited by graft availability and donor site morbidity. We have developed a bioprosthetic implant, combining articular cartilage resurfacing and osseous tissue regeneration, as a new method for OCD repair. These implants – “cartilage-capped, regenerative osteochondral plugs (CC-ROPs)” - combine a multi-network hydrogel (cartilage cap) and osseous scaffold (base). The cartilage cap is prepared from a multi-network, electrostatic hydrogel that gives rise to articular cartilage-like mechanical, hydration, and tribological properties. The osseous scaffold base is prepared from a semi-interpenetrating polymer network (semi-IPN) of poly(ε-caprolactone)-diacrylate (PCL-DA) and poly(L-lactic acid) (PLLA). The scaffold is intrinsically osteoinductive and has a trabecular bone-like modulus as well as robust degradation rates to facilitate bone ingrowth. Formed as cylindrical plugs, CC-ROPs are able to be implanted using existing grafting techniques and be fabricated at a wide range of sizes. CC-ROPs were successfully implanted into rabbit OCDs using an osteochondral graft delivery device with a custom tip to help alignment on the small rabbit condyles. At 10 days, MRI images illustrated the cartilage cap remained intact with the osseous scaffold (i.e., no delamination). It was also confirmed that CC-ROPs did not become displaced post implantation. Formation of new tissue around the periphery of the osseous scaffold was illustrated in microCT and histological analyses. At 12 weeks post-implantation, there were likewise no signs of delamination or fracture of the CC-ROP. Furthermore, no migration of the implant was seen (e.g., cartilage cap surface congruent with surrounding cartilage). Extensive bone tissue formation was seen around the edges and throughout the pores of the osseous scaffold. Performance in rabbit OCDs illustrated the ability of CC-ROPs to immediately provide an articulating surface as well as promote regeneration of osseous tissue, exemplifying the potential to improve the treatment of OCDs.