Patellofemoral Osteochondral Allograft Transplantation

Patellofemoral (PF) cartilage defects are common. They may result from instability, incongruity between the patella and trochlea, repetitive overload (microtrauma), or direct impact (macrotrauma). If exhaustive conservative management fails to resolve symptoms of disabling anterior knee pain with activities of daily living, surgical treatment may be considered. There are 3 main indications for osteochondral allograft transplantation: cartilage defects that are associated with extensive abnormalities of the subchondral bone or frank bone loss that are expected to compromise surface procedures such as autologous chondrocyte implantation; cartilage defects that are associated with severe trochlear dysplasia; and PF osteoarthritis in young patients who are not candidates for arthroplasty. Osteochondral allograft transplantation is performed using 1 of the 2 following techniques, depending on the location and extent of cartilage damage being addressed. The dowel or press-fit technique utilizes a cylindrical reamer and coring reamer system to fashion a dowel and recipient site with a diameter ranging from 15-35 mm. The shell technique is an alternative, which addresses very large defects in which the chondral defect area is removed along with bone with a saw using the same plane(s) as for prosthetic resurfacing (total knee arthroplasty or PF arthroplasty). Careful assessment of PF kinematics and anatomy (or pathokinematics and pathoantatomy) are the key to optimizing success. In light of these factors, associated procedures (such as tibial tuberosity osteotomies, medial PF ligament reconstruction, or lateral retinacular lengthening) are very common in PF cartilage repair, especially with bipolar grafts. With attention to detail and technique, successful outcomes may be achieved in many patients.