Osteochondral allografts are commercially available from tissue banks with oversight by the Food and Drug Administration. All tissue is harvested within 24 hours of donor death with ideal donors aging from 15 to 40 years old. Chondrocytes must remain viable for there to be any chance of successful transplantation. The clinical success of transplant is dependent on several factors, which ensure an intact extracellular matrix, viable chondrocytes, and incorporation of host bone.[12][13][14][5]

Allografts can be stored fresh, frozen, or cryopreserved. Each storage technique has different effects on the biomechanical and biochemical properties of the cartilage graft. Fresh storage has been shown to have the highest level of chondrocyte viability,[15] and storage at room temperature significantly improves the viability of osteochondral grafts. Donors are tested for HIV, hepatitis B, hepatitis C, and human T-lymphotropic virus (HTLV) prior to harvesting.[5][16][17]

The size and location of the chondral defect determine which osteochondral allograft transplantation technique is most appropriate. Small solitary defects can be filled with a single plug that is matched exactly to the size and shape of the defect, providing complete coverage of the chondral deficiency and integration with the surrounding tissues. Below is a discussion of some of the more common methods employed by surgeons to address articular surface defects.

It should be noted that due to the rather soft nature of articular cartilage, transplanting the cartilage alone without some aspect of its accompanying bony support is not possible since securing it in place is problematic if not impossible without some reliable form of shear resistant fixation.

Larger lesions may require a more significant arthrotomy of the joint to fully visualize the defect to ensure that the entire zone of injury is appropriately addressed. Having a healthy rim of cartilage available along the edges of the graft is essential for appropriate integration into the patient's tissue.[18]

The Snowman technique, or mosaicplasty technique, is one method to address larger chondral lesions, allowing for coverage of a bigger area than is allowed by single plugs. In this technique, a single plug is placed with a standard reaming technique and held in place with wire fixation. A second plug is subsequently reamed, overlapping with the first allowing for a confluence of the two plugs, covering a larger articular surface area.[19] In this manner, the area can be filled much like abutting small round tiles into each other to cover a larger floor surface area.

The Shell technique is ideal for the treatment of asymmetrical cartilage defects and defects that are difficult to access with standard arthrotomies, such as defects of the posterior femoral condyle. In this technique, the entire affected recipient site can be removed en bloc, and a size-matched donor bone is cut and contoured to cover the recipient lesion, covering the defect as a "shell" of protection.[5]

The small fragment allograft technique alternatively may be used in defects of the tibial plateau where the entire meniscotibial unit is replaced by a donor unit and stabilized with screw fixation.[5]

Finally, while this article addresses the osteochondral allograft transplantation methods, there are newer technologies wherein articular cartilage scaffolds or membranes can be sewn or adhered into the articular surface defects found within the knee. Those techniques show promise in many situations and will likely, in some instances, replace the need to transplant an auto or allograft osteochondral segment.

As with any surgical procedure pain, bleeding, damage to surrounding anatomic structures, and infection are a risk, albeit low compared to many surgeries in the hands of a skilled arthroscopist. Outside of the general complications associated with any surgical procedure, graft failure is of the greatest concern. While patients who undergo osteochondral allograft transplantation for traumatic or idiopathic injuries have a reported graft survival of 100%, cartilaginous defects caused by post-traumatic arthritis, osteonecrosis, or osteochondrosis have a lower rate of graft survival.[5] Ultimately, the underlying cause of the index deficit should be considered. If the cause of a patient's cartilaginous defect is due to an anatomic or medical derangement, failure to address the cause of the deficiency will inevitably lead to failure of the procedure and potential exacerbation of the joint insufficiency.

Articular cartilage defects often result in pain and discomfort that seriously affect a patient's quality of life. When non-surgical management fails, osteochondral autograft or allograft transplantation is a reasonable solution to provide patients with hope for a better quality of life. With joint pain reduced or eliminated, patients may return to normal activity while avoiding more invasive or elevated risk profile procedures such as total knee arthroplasty. Prolonging an active lifestyle is important and can lead to overall better physical and mental health.

Management of painful joint pathology requires an interprofessional approach that includes the patient in his care and supports a return to activities that may be limited by his or her disease process. Non-surgical management is the first-line treatment for a painful joint, and physicians and therapists must communicate and work together to help patients find solutions to their pain limitations. When non-operative measures fail, surgery may be considered.

Any time surgery is undertaken, medical practitioners must have a good surgical team in place. Surgical techs, nurses, and surgeons must work together seamlessly in the operating room to provide the patient with the highest likelihood of a successful outcome. The surgeon must then communicate with the physical therapist, who is vital to providing the patient with the appropriate post-operative protocol to ensure a safe return to function post-operatively. [Level 5]