An osteochondral allograft is a piece of tissue taken from a diseased donor to replace damaged cartilage that lines the ends of bones in a joint. A section of cartilage and bone is removed, shaped to precisely fit the defect and then transplanted to reconstruct the damage.
The articulating surfaces of all the joints in the body are lined by a soft tissue called articular cartilage, which cushions the ends of bones. This allows easy gliding of the bones during movement of the joint. Injury and wear-and-tear can damage the cartilage, making it rough and sometimes expose the underlying bone. This leads to painful rubbing of the bones of the joint and disability.
Osteochondral allograft is indicated for:
- Large area of damage, within 15 to 35 mm
- Having symptoms of pain, swelling and catching
- Localized, full-thickness injury
- Patients under 50 years of age
- Active patients with high physical demand
- Associated with lesions such as
- Osteochondritis dissecans (lack of blood supply separates a segment of bone from its surrounding)
- Avascular necrosis (death of bone tissue)
The implantation of osteochondral allografts is usually performed through an open incision, under general or spinal anesthesia. An incision is made to expose the joint defect. The size of the defect is then measured and a portion of the cartilage and underlying bone is removed.
A fresh allograft taken from a diseased donor is sterilized, prepared in the laboratory and tested for probable disease transmission. It is then trimmed with an oscillating saw to match the size of the prepared defect.
The allograft is then gently press-fit into the defect created in the recipient bone.
It can be further stabilized with metallic screws and pins.
The incision is closed and dressing applied to the joint.
Following the surgery, a brace may be applied for the first 2 weeks. Your surgeon will prescribe medication to reduce pain. You will be instructed to use crutches and limit bearing weight for 6 to 8 weeks. Early movement is encouraged, and you will be gradually introduced to physical therapy, which will be continued for 8 to 12 weeks.
You may be able to return to your activities in 6 to 12 months.
Advantages & disadvantages
When compared to osteochondral autografts (tissue taken from another part of your body), osteochondral allografts help reconstruct large three-dimensional articular defects and overcome the possibility of defect at the donor site.
However, osteochondral allograft is associated with a higher risk of immune-mediated graft rejection and disease transmission from the diseased donor and the transplantation of the graft is a more invasive procedure when compared to osteochondral autografts. It is also difficult to obtain fresh donor specimens with the required cartilage thickness.
Risks and complications
As with all surgical procedures, the transplantation of osteochondral allografts may be associated with certain risks and complications such as:
- Implantation failure
- Blood clots