Articular cartilage is a unique tissue in joint that is constantly subjected to stress and is very vulnerable to traumatic injury or degenerative conditions. This is especially true in large weight-bearing joints such as the knee. When a teenage, young adult, or middle-age adult has a localized area of a full thickness cartilage or a full thickness cartilage and bone defect, this is in effect a localized area of osteoarthritis.
In patients with large defects, or in defects involving the bone, an effective treatment for the cartilage deficiency is a fresh osteoarticular allograft. These allografts are obtained from young donors who had the same size knee as the affected patient.
The workup for determining if a patient is a candidate for a fresh osteoarticular allograft is very important. Alignment must be assessed to make sure they are not putting extra stress on the affected compartment, the patient should have intact ligaments so there is no instability (or be able to have a concurrent ligament reconstruction), and it is important to determine that the patient has a normal amount of meniscus present to provide cushioning to the joint so that the joint is not overloaded. In addition, it is important that there not be cartilage lesions on the opposing articular cartilage surface, “a bipolar lesion”, because these types of lesions do not do as well with any type of cartilage resurfacing procedure. Another important piece of the workup is obtaining sizing x-rays of the knee such that the appropriate size donor graft can be obtaining in the future.
Description of Osteoarticular Allografts
The fresh osteoarticular allograft needs to be implanted via an open incision that allows access to the joint. In most locations of the knee, these incisions can be small, which helps to avoid any quadriceps muscle shutdown. However, there are times when they are in difficult to access locations where the incisions must be larger to make sure the graft can be properly placed.
One of the keys for success of osteoarticular allografts is transplanting a refrigerated allograft within the first 15-28 days postoperatively. It takes 14 days for assessment of the grafts to make sure there are no viral or bacterial contaminants. We strive to implant the grafts as soon as possible once they have passed testing to try and provide the most viable cells to the patient.
Fresh osteoarticular allografts have been found to result in significant functional and clinical improvement after an average follow up of three years, in our patient who have been treated for a full thickness osteochondral defect to the femoral condyle, with similar outcomes to historical reports in other centers for patients treated with fresh osteoarticular allograft implants.
It is very important that a careful assessment be made as to whether a patient is a candidate for this surgery. In addition, while this procedure is not felt to be a cure for arthritis, many patients can get 10 years or more of significant improved outcomes with this surgery. In effect, this is a “biologic resurfacing” procedure and it is important to recognize that not all patients can return back to full impact activities after the surgery.
Patients who receive a fresh osteoarticular allograft need to be non-weightbearing for 8 weeks after surgery. During this time, they are in a continuous passive motion (CPM) device for 8-10 hours per day. In patients with a single donor plug, they are allowed to work on a stationary bike once the surgical incision is adequately healed (usually at about two weeks after surgery). Physical therapy is initiated immediately after surgery to work on quadriceps muscle reactivation, knee motion, and to control swelling.
At 8 weeks postop, radiographs are obtained to verify sufficient healing of the donor graft. Once adequate healing is confirmed, patients are progressed on a partial weight bearing program, advancing at ¼ body weight per week until they are fully weight bearing. The use of a stationary bike with resistance and leg presses at ¼ body wright are also initiated.
Patients may fully wean off crutches at 3 months postop and progress in proprioceptive and agility exercises. Impact activities need to be approved by the surgeon and may be initiated at between 6-9 months after surgery.