Cartilage Injury and Repair
Articular Cartilage Damage and Treatment
Articular cartilage is a unique tissue in our joints 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 someone has a localized area of a full thickness cartilage or a full thickness cartilage and bone defect, this represents 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 also have intact ligaments so there is no instability. It is important that the patient has a normal amount of meniscus present to provide cushioning to the joint. Lastly, 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 cartilage resurfacing procedures.
Description of Osteoarticular Allografts
An osteoarticular allograft is a piece of bone and cartilage that has been obtained from a young donor and is implanted into a full-thickness cartilage defect. The graft needs to be implanted via an open incision that allows access to the joint. 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 for a full thickness osteochondral defect to the femoral condyle particularly. 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.
38 year-old female with large full-thickness medial femoral condyle cartilage defect (left) following previous failed microfracture procedure performed elsewhere. Intraoperative photo of large osteochondral allograft implant through open incision (right).
Post-Operative Protocol for Osteoarticular Allografts
Patients who receive a fresh osteoarticular allograft need to be non-weightbearing for 6-8 weeks after surgery. In patients with a single donor plug, they are allowed to work on a stationary bike oat zero resistance 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. XRs are obtained to verify sufficient healing of the donor graft. Once adequate healing is confirmed, weight bearing is progressed until fully weight bearing. Impact activities need may be initiated at between 6-9 months after surgery.
What are the criteria that must be followed for one to have a successful osteoarticular allograft surgery?
There are several factors that should be worked up for every patient to ensure the maximum success rate after an osteoarticular allograft transplant. First, the patient should have normal or correctable alignment. This is because if they are malaligned with the weightbearing going into the compartment for the planned osteoarticular allograft, the success rate in the peer-reviewed literature has been shown to be much less. In addition, one should have a good “cushion” of meniscus in that same compartment. The meniscus is important as a shock absorber, and if one does not have a meniscus or has a significant loss of meniscus, the cartilage in that compartment and the donor graft will wear out much faster. Another factor to look at is whether knee stability is present. If one has an unstable knee, the outcomes of a fresh osteoarticular allograft are also less successful. Therefore, if one has ligament instability, the ligament instability should be corrected, most commonly at the time of the fresh osteoarticular allograft procedure, to maximize the patient’s outcome. Finally, the cartilage on the opposing surface of the donor fresh osteoarticular allograft should also be normal or nearly normal. If one has significant wear of the opposing surface, the osteoarticular allograft procedure has a much lower chance of working. Thus, the basic workup for determining if one is a good candidate for a fresh osteoarticular allograft includes the alignment, assessment of ligament stability, assessment of the amount of meniscus in the same compartment, and also the opposing cartilage surface condition.