For these reasons, much effort has been directed towards developing ways of potentially replacing lost meniscal cartilage tissue.
If the whole meniscal cartilage has been lost, then the only real option at present is to perform meniscal allograft transplantation. This is a procedure where the missing meniscal cartilage is replaced with donor tissue, which is screened and sterilised much in the same way as other donor tissues such as for kidney transplants. The difference, however, with meniscal transplants is that the cells within the cartilage tissue are embedded in a thick and relatively impenetrable elastic tissue, which means that the patient’s immune cells do not react to the new donor tissue. This means that meniscal allografts can be transplantated into patients’ knees without the need for nasty immunosuppressive drugs, and with no significant risk of rejection.
The surgical procedure of meniscal transplantation has gained significant popularity in the US, with over 4000 meniscal transplants having already been performed to-date. Meniscal transplantation has been demonstrated to provide good pain relief, with success rates in excess of 80% at 5-years follow-up. Again, the real proof of this procedure will be the degree to which degenerative changes in the knee may be delayed or avoided in the long term.
Very few centres in the UK are currently offering meniscal transplantation as a surgical option, largely due to the technical and logistical complexities involved. However, the team of knee surgeons in The London Knee Clinic has now performed over 30 transplants.
The Menaflex Collagen Meniscal Implant
For those patients who have lost significant amounts of meniscal cartilage tissue, but in whom there has not been complete loss and the outer rim is still intact, there is now a new surgical option that has very recently become available to patients in the UK.
The Menaflex collagen meniscal implant is a scaffold made from collagen, which is a natural substance made of numerous fibres and bundles, and which is the major constituent of normal meniscal tissue. The implant is highly porous and acts as a scaffold, allowing a patient’s cells to grow into it so that the missing meniscal tissue regrows.
The Menaflex collagen meniscal implant was developed in the US by a team including Dr Richard Steadman, from Vail, Colorado – one of the world’s leading knee surgeons. The first meniscal implant procedures were performed in the US in 1993 as part of a feasibility study. The good results led to multicentre studies starting in the US and Europe in 1997. In the year 2000, the positive results in Europe led to CE certification for the medial implant, and subsequently the lateral implant also received approval and is now in clinical use. To-date, more than 1,700 patients worldwide have had collagen meniscal implants successfully inserted into their knees.
The clinical studies to date have demonstrated the following:-
The meniscal implant is biocompatible (ie it does not cause tissue reactions and is not rejected).
More than 70% of the patient’s missing meniscal tissue regrows into the new scaffold.
Patients receiving the meniscal implant ended up with higher activity levels compared to similar patients undergoing partial meniscectomy.
Strict adherence to an appropriate rehabilitation programme is vital after Menaflex meniscal implant surgery. Even though the discomfort from the operation is likely to subside quite quickly, after just a few days, it is still essential to protect the knee and limit activities in order to allow the meniscal implant to ‘take’ – ie, to allow the tissues of the knee to begin to grow into the implant from its edge (which keeps it secure in position) and for the tissue to grow into the actual scaffold, which gives the new meniscal tissue its strength. Therefore, activities need to be carefully restricted initially, with a slow supervised return to limited specific exercises under the close supervision of a physiotherapist. Vitally, patients should not return to sport until 6 months post-op.
The Menaflex collagen meniscal implant has only very recently been introduced into the UK by Hospital Innovations, a Cardiff based company. The procedure is being introduced under strict and careful guidelines. Only experienced surgeons specialising in knee surgery and who have been specifically trained in the technique are currently allowed access to the implant in the UK. It is envisaged that the results in the UK will mirror those already seen in Europe and the US. However, it has been agreed by the UK Meniscal Study Group that thorough and careful detailed clinical evaluation for all patients undergoing this surgery is essential.
The possibility of using genetic engineering to regrow one’s own damaged meniscal tissue in-situ is still a long way off, but genuine and exciting progress in the area of meniscal surgery is being made, and the axiom of “meniscal preservation where possible, meniscal replacement where indicated” most certainly holds true.