#treatment - Knee
- Meniscal tears are very common
- Meniscal cartilages are important shock absorbers in the knee and loss of meniscal tissue increases the risk of future arthritis in the knee
- For patients with a painful knee after loss of a meniscal cartilage, in some cases it may be possible to replace the missing tissue with a new meniscus
- The new meniscus comes from a tissue donor (just like with kidney donors) and is called an ‘allograft’
- Meniscal allograft transplantation is a complex operation
- The results of meniscal transplantation are good, with about 75% of patients achieving a good-to-excellent outcome at 5 years follow-up
The menisci are wedges of crescent shaped elastic cartilage inside the knee, sitting between the bones of the femur (thigh bone) and the tibia (shin bone). There is one meniscal cartilage on the inner side of the knee – the medial meniscus – with another sitting on the outer side of the knee – the lateral meniscus. The meniscal cartilages are placed between the bones of the knee like little elastic potato wedges, acting as shock absorbers.
Meniscal tears are a very common knee injury. In younger people, meniscal tears most commonly occur from sporting injuries, such as a bad football tackle or an awkward skiing fall. As you get older, the meniscal cartilages become gradually more degenerate and lose their elasticity, and they can potentially tear with just minimal trauma (like getting up from kneeling) or even spontaneously.
Tears of the meniscal cartilages can cause knee pain, swelling, clicking, giving way or locking. Unfortunately, the meniscal cartilages have a very poor blood supply, and therefore tears very often fail to heal up on their own.
Meniscal tears that are causing significant persistent symptoms are normally treated by knee arthroscopy (keyhole surgery). A small percentage of tears may be repairable. However, the majority are not, in which case the torn cartilage is trimmed via the keyhole surgery.
As the meniscal cartilages are important shock absorbers in the knee, loss of meniscal tissue leads to increases stresses in the knee joint, with increased wear and tear eventually leading to degeneration and arthritis.
If a patient presents with a painful knee after previous trimming or excision of the meniscus (called meniscectomy), then there are two treatment options that may potentially be possible:
- The Menaflex Collagen Meniscal Implant. This is an engineered scaffold of collagen (which is the main structural component of a meniscus), which can be fixed into the knee to fill a missing defect in a meniscal cartilage. New meniscal tissue grows into the scaffold. However, this option is only suitable in cases where the outer rim of the meniscal cartilage is still intact (click here for further information on the Menaflex Collagen Meniscal Implant).
- For patients where there is no intact peripheral meniscal rim or where the whole meniscus has been lost, meniscal allograft transplantation can be a potential option.
The most common reason for performing a meniscal transplant is when a patient has previously lost a meniscal cartilage in their knee and they have then gone on to develop early degeneration, with pain in the knee and decreased function.
Another potential reason for performing a meniscal transplant is to replace the shock absorber inside the knee and therefore help protect the knee and reduce the likelihood of the knee developing arthritis in the future.
One further potential indication for meniscal transplantation, which is advocated by some surgeons (for example in some centres in the US) is to replace damaged meniscal cartilages in knees that have significant arthritis, as a means of trying to potentially keep the knee going and delay the time that an actual knee replacement becomes necessary.
An allograft is a piece of tissue obtained from a donor – just like kidney/lung/heart donors etc. The donor are screened extremely carefully, and the tissue is tested for bacterial or viral contamination. The tissue is then sterilized using and then frozen and stored.
The first reported cases of meniscal transplantation in human was from Milachowski, a German surgeon, in 1987. Since then, there has been intense interest in and research into the field of meniscal transplantation and replacement. To-date, well over 4000 procedures have been performed in the USA. In Europe, the main centres for meniscal transplantation are Gent, Belgium and De Haag, The Netherlands, with Professor Rene Verdonk having performed over 100 meniscal transplants. In the UK, there are very few surgeons trained in and practicing meniscal transplantation, with Mr Angus Strover from LONDON SPORTS ORTHOPAEDICS (at the London Bridge Hospital) having performed probably more transplants than any other UK surgeon, with his tally to-date exceeding 50.
Meniscal transplantation is a technically demanding operation. It is normally performed under a general anaesthetic. Most transplants can normally be performed arthroscopically-assisted (with the aim of keyhole surgery), and thus the scars are relatively small.
The graft has to be fixed into the knee solidly at the front and the back. This normally involves drilling tunnels into the bone of the tibia (shin bone), into which the ‘meniscal horns’ are fixed (see image). The rest of the meniscus is then stitched around its edge to the inside lining of the knee.
Patients are normally in hospital for 1 or 2 days post-op, before being able to go home, non-weight bearing with crutches and with their leg in a knee brace.
In order for a knee to be suitable for receiving a meniscal transplant, it is important that:
- The knee ligaments must be intact and the joint must be stable. If not, then it may be necessary to perform a ligament (eg ACL) reconstruction as well as the meniscal transplant, in order to stabilise the knee and protect the graft.
- The knee alignment must be normal. If the knee is not normally aligned, then there will be excess pressure on one or other of the side of the knee. These increased forces will put additional pressure on a graft, potentially causing failure. Therefore, malalignment of the leg must be corrected first with a surgical realignment (osteotomy) operation.
- Wear and tear: if there is major wear and tear of the layer of articular cartilage that covers the surface of the knee joint, especially if there are patches of exposed bare bone, then this will abrade the surface of the meniscal graft as the knee flexes (bends) and extends (straightens). Therefore, if there are any significant patches of cartilage damage then these may need to be addressed as well as replacing the meniscal tissue. There are various methods for trying to repair damaged articular cartilage (click here).
It is essential to restrict knee movements and activities directly after the operation, in order to protect the graft whilst it is healing into the knee.
For the 1st 6 weeks after the operation, patients are normally kept non- or minimally weight bearing with 2 crutches, and with their leg in a strap-on hinged knee brace that prevents the knee from bending up more than about 60o.
After 6 weeks, the meniscus should have healed into the knee, but it will still be fragile. The brace and the crutches are discarded, and patients then start intensive physiotherapy treatments in order to regain the full range of knee movements and the muscle strength and reflexes in the knee.
At 3 months, we advise having a repeat arthroscopy (look inside the knee with keyhole surgery). This is to check that the meniscal graft has fully incorporated into the knee. It is normal that at this arthroscopy for there to be either small flaps of tissue that might need to be trimmed, or additional stitches that might be required into the graft.
After this second arthroscopy, patients are allowed to gradually resume normal activities, under the close supervision of their physiotherapist. Patients are not advised to return to sport until a full 6-months after the transplantation operation.
The cells within meniscal tissue are ‘locked in’ inside a dense matrix of tissue, made up of fibres of collagen and large spongy molecules called glycosaminoglycans. This means that the body’s immune cells are unable to get to the cells in the meniscal tissue. Cartilage tissue is therefore referred to as ‘immunoprivilegded’, which is to say that donor cells within the graft tissue do not cause an immune response in the patient’s knee. Therefore, with meniscal transplantation, patients can have receive a graft without the need for it being covered with drugs such as steroids or other potentially nasty immunosuppressives.
The published results of meniscal allograft transplantation to-date are encouraging, with good pain relief and good improvement in function. A recent review showed that over 75% of patients are satisfied with the procedure, with over 90% of patients reporting good-to-excellent results in one study. Studies on meniscal transplantation in animals has demonstrated a reduction in the progression of knee arthritis compared to leaving the knee with no meniscus. However, it will take a number of further years before the results of long term research studies will become available to show just how much meniscal transplantation might protect the human knee from future arthritis.
CLICK HERE to read a patient’s personal experience of undergoing meniscal allograft transplantation
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