When the majority of a meniscus has been torn and defunctioned or removed, the remaining articular cartilage is likely to wear at an accelerated rate and develop osteoarthritis, pain and swelling prematurely. This necessitates consideration in the appropriately aged patient with adequate remaining articular cartilage, a stable knee and acceptable alignment of a meniscal transplant using donor tissue from the “Bone & Tissue Bank”.
What is the Meniscus and what is its Role?
The meniscus is a semi lunar wedge shaped fibrocartilaginous structure which plays an important role in many functions of the knee including load transmission, shock absorption, joint stability, cartilage nutrition and lubrication. During normal walking, the knee experiences 4 to 6 times body weight being transferred through it and the meniscal cartilage helps dissipate these forces, shielding the underlying articular cartilage.
When is Meniscal Transplant an Option?
The menisci transmit about 50% of the joint load when the knee is out straight or in extension, and about 90% when it is bent or in flexion. Loss of 20% of a meniscus can lead to a 350% increase in contact forces across the knee. Thus, loss of the meniscus or meniscectomy, increases the peak articular contact stress at least twofold to threefold and is associated with the development of early degenerative changes. The decision to perform a meniscal transplant is a process of exclusion, with the vast majority of patients who undergo meniscal resection not requiring consideration of meniscal transplant.
This surgery is not commonly performed in Australia, with only a few surgeons trained and experienced in the procedure. The patients most likely to benefit from consideration of meniscal transplant are young patients nearing skeletal maturity or older experiencing pain in a meniscus deficient compartment, with a stable knee, normal alignment, minimal articular cartilage damage, and no history of infection or inflammatory arthritis.
What does Meniscal Transplant Surgery Involve?
Meniscus transplants have been performed using artificial or synthetic meniscal materials, but the current gold standard continues to be the use of allografts or donor tissue from human organ donors. These grafts are harvested by Dr Gallagher and a colleague and are sized and then frozen and stored in the Queensland Bone and Tissue Bank under sterile conditions.
The graft is prepared at the time of transplant to include the meniscus and also some underlying bone either as a narrow rectangular keel, or as two small bone plugs where the meniscus fixation points are attached. Patients are screened for transmissible diseases, and whilst a theoretical risk of “graft to host” infection exists, the likelihood is remote, and has not occurred in any of Dr Gallagher’s patients.
There is also a theoretical risk of immune mediated “host vs graft” disease or graft rejection but the meniscus does not appear to incite a large immune response and Dr Gallagher again has no patients which have experienced a frank immunological reaction or rejection.
What to Expect with Surgery?
Once a decision has been made to proceed to meniscal transplant, correct sizing of the meniscal transplant will be calculated based upon some carefully performed plain X-rays and a correction factor for magnification for width and both magnification and a reduction ratio for length depending upon whether it is in the medial or lateral compartment.
The majority of the surgery is performed using keyhole or arthroscopic technique, with two small anterior incisions (less than 1cm). Depending on whether it is a medial or lateral meniscus being transplanted one of the two keyhole portals (on the same side as the graft) is extended by approximately 2cm’s to a total of 3cms to allow for the passage of the meniscal transplant into the knee and an additional incision is made along the side of the knee on the same side, measuring approximately 3 fingerbreadths (usually 5cms) in order to receive safe passage of sutures, to help pull the graft into the knee joint and finally to adequately tension and tie the suture knots under direct visualisation, ensuring that other structures are not ensnared in the knots.
A drain is positioned within the knee and is removed the following morning and the knee is fitted with an extension splint for two weeks, followed by a range of motion brace once the wounds have healed and the post-operative swelling has resolved.
Post Operative Care for Meniscal Transplant
Patients usually stay in hospital 1 or 2 nights after surgery and mobilise protective weight bearing initially with graduated weight bearing and range of motion using crutches for a 2 month period and avoidance of at risk activities (deep squatting under load, high impact, twisting, sudden deceleration) for a 4 month period.
Usually by the 6 month post operative review patients are confident with their knee with a good range of motion, good strength and tone and alleviation of their preoperative pain. Follow up MRI scans are usually performed at 6 months and 1 year post-operatively.
For a consultation with Dr Gallagher or more information on suitability for meniscal transplant make an appointment today.