Introduction to Osteochondral Allografts

OCAs are donated human tissue grafts that are composed of subchondral bone and viable cartilage cells. The outermost layer of cartilage, articular hyaline cartilage, is composed of chondrocytes that are essential for cartilage to form and function properly. Under normal circumstances, articular cartilage can handle typical wear over time. In some cases, cartilage can become so damaged that it cannot repair itself. These cartilage lesions will persist indefinitely causing pain and typically progressing to joint degeneration or osteoarthritis ^1,4,5,8,11.

Fresh OCAs have been utilized as a treatment option for cartilage defects in all major joints of the human body to include the knee, ankle, shoulder, hip and elbow. Transplantation of these grafts has been performed for approximately three decades and multiple studies have shown that it can be an effective treatment option for adults who have large chondral and osteochondral defects in the knee ^3,9. Still, treatment of cartilage in the patellofemoral, femoral condyle and tibial plateau regions of the knee can present challenging obstacles for orthopaedic surgeons ^4,5.

Initially, OCAs were used to treat defects that arose from trauma or because of tumors. The indications have expanded to include chondral and osteochondral lesions due to osteochondritis dissecans (OCD), osteonecrosis, defects of an unknown origin, inflammatory conditions and select cases of osteoarthritis (OA) ^2,6. In general, treatment becomes more difficult as the size of the lesion becomes larger and also when the subchondral bone is involved. Allografts allow for the resurfacing of larger and deeper diseased or absent subchondral bone defects that other surgical measures would not be able to achieve ^1,4,8,10. They are especially utilized in procedures where the lesion is too large to undergo an osteoarticular transfer system (OATS) or microfracture procedure or the patient has not responded to other prior conservative or surgical management. On average, patients with cartilaginous lesions of the knee have already undergone 1.7 of these other treatment procedures before undergoing an OCA transplantation ⁴.

OCA use has become more commonplace in reconstruction and revision surgeries because unlike autografts, they are not associated with donor-site morbidity and also allow for shorter operative time and decreased surgical site pain ^1,7,10.

While there are surgeons who have had success with the procedure, the Level of Evidence in current literature is low. Most articles on the subject are retrospective case series ³. In order to gain a better understanding of this current treatment option, an observational registry is proposed to follow patients over several sites with defects in the knee pre-operatively through long-term follow-up. In doing this, a better assessment of the patient factors, surgical techniques and overall survivorship of OCAs can be undergone. Information yielded about optimal outcomes may benefit future patients.