The new KineSpring implant from Moximed
– the latest advance in the management of osteoarthritis of the knee .....
Knee wear and tear / degeneration / arthritis can cause debilitating pain, stiffness and disability. Severe arthritis in older patients can be treated very effectively by total knee replacement. However, knee replacement surgery is a major undertaking, being a fairly large operation with not-insignificant pain and with a relatively slow and long recovery. Also, artificial knees never feel as good as a normal knee, plus there are potential risks associated with the surgery.
CLICK HERE for further information about knee replacement surgery.
Importantly, the younger a patient is when they have a knee replacement, the more they will use it (greater loads and more movement cycles), and hence the faster the rate of wear. On top of this, younger patients live longer, and so the artificial joint will be subjected to more years worth of wear. Hence, a knee replacement is more likely to wear out and need replacing within the patient's lifetime if the patient is young. To quantify this: if a knee replacement is put in in someone in their 70s then there is only a 5% chance that it will fail within the patient's lifetime. If a knee replacement is put in in a patient in their 50s then there is a 50% chance of it failing within the patient's lifetime. If a knee replacement fails then it can be removed and a new knee replacement can be inserted - a 'Revision Knee Replacement'. However, revision knee replacement is a more complex and more difficult operation that a primary (the first) knee replacement, and revision surgery has greater potential surgical risks, lower patient satisfaction and functional outcome scores, and revision joints tend not to last as long as a primary joint. Therefore, revision surgery should always be avoided where possible -- and the best way to avoid ever needing to have a revision knee replacement is to delay the time when you have your first (primary) knee replacement. Therefore, smaller alternative surgical solutions that offer a more 'biological' approach and that are 'bone-sparing' are often an attractive alternative for the younger patients.
For those patients who have less severe damage in their knee, a thorough tidy-up of the joint by knee arthroscopy can give significant improvement in symptoms, with improvement in function, and can help people keep their knees going for longer, delaying the time when knee replacement might become necessary.
CLICK HERE for further information about knee arthroscopy.
The dilemma comes when we are confronted with patients with severe degenerative/arthritic damage in their knee but who are still 'young' (too young to want a full knee replacement). Often, the underlying reason why a patient may have developed early/premature arthritis in their knee is that they might have damaged the joint previously, for example with a meniscal cartilage tear that necessitated removal of the meniscal cartilage shock absorber in the joint. For younger patients with early arthritis secondary to meniscal loss, we are now able to improve their symptoms, improve their function, keep their knees going for longer and delay the time when they might end up needing a knee replacement --- by replacing the missing meniscus by meniscal allograft transplantation.
CLICK HERE for further information about meniscal transplantation.
In truly severe cases where there is significant articular cartilage loss as well as meniscal deficiency, then we are even able to replace missing articular cartilage by articular cartilage grafting using the Chondrotissue Graft.
CLICK HERE for further information about Chondrotissue Grafting.
When we combine meniscal transplantation with articular cartilage grafting using Chondrotissue Grafts, then this is referred to as ‘Biological Knee Replacement’ (a term coined by Dr Kevin Stone, of the Stone Clinic in San Francisco). Biological Knee Replacement (reconstruction) has been shown to be effective in younger patients at keeping their knees going and delaying the ultimate need for knee replacement surgery. However, this is a large and very complex operation, with very slow and restrictive rehab required, and it takes patients often a full 9 months to fully get over the operation. Also, this is very much a salvage procedure, and the reconstruction does not give the patient a brand new normal knee – I always advise my patients with a Biological Reconstruction to always avoid heavy/impact/twisting exercise, and the procedure does not allow patients to go back to sport at all.
CLICK HERE for further information about 'Biological Knee Replacement/Reconstruction'
One further problem with Biological Reconstructions is that to be suitable for the procedure the joint needs to be stable and well aligned. If there is any kind of instability in the joint due to a ligament deficiency, then the ligament (e.g. the ACL) can be reconstructed relatively easily. However, early arthritis frequently affects mainly just one compartment/side in the knee – when the cartilage in one side of the joint wears thin and wears away, this reduces the gap between the bones on that side of the knee (the joint space). When the joint space reduces more on one side (inner/medial or outer/lateral) of a knee then the knee will gradually become increasingly bent (malaligned).
When the damage is on the inner/medial side of the knee and the knee goes outwards (i.e. the shin is angled inwards) and the patient becomes ‘bow legged’ – this is referred to as a Varus deformity. When the joint damage is predominantly in the outer/lateral side of the knee, the knee tends to drift inwards (the shin angles outwards) and the patient becomes ‘knock kneed’ – this is referred to as a Valgus deformity. Medial knee arthritis is a lot more common than lateral arthritis, and hence varus deformities are the most common.
If a knee is malaligned, the more bent the joint is the more load will actually be being placed onto the damaged side of the joint, which simply aggravates and hastens the degenerative process in the joint. A meniscal allograft transplant and/or a Chondrotissue articular cartilage graft should not be put into a malaligned joint as the malalignment will significantly increase the risk of graft failure and a poor outcome.
For joints that have a large amount of malalignment, where a correction of 10o or more is required, then the operation of choice is to perform what is called a ‘realignment osteotomy’. This is where either the femur (thigh bone) or tibia (shin bone) are cut, the bone is straightened to straighten the knee and then the cut bone is fixed with a metal plate and screws. Realignment osteotomy is a fairly large operation that requires quite slow and restrictive post-op rehab, and which carries with it various risks, including the risk of infection or non-union (failure of the cut bone to actually heal).
CLICK HERE for further information about Realignment Osteotomy
Up until very recently, the real dilemma was ‘what to do for those patients who are younger and who have early arthritis, who have a varus malalignment for medial knee arthritis but whose malalignment is less than 10o, and hence not actually bad enough to justify a realignment osteotomy’? The answer to this question is now the KINESPRING offloader from Moximed!
The KineSpring is a shock absorbing load sharing spring that is fixed in the knee between the femur and the tibia on the medial side, which offloads a significant proportion of the weight/forces from the medial side of the joint, up to a maximum of 13kg. Studies have demonstrated that the KineSpring implant significantly reduces loads in the medial compartment, which reduces pain, thereby improving function. The aim of the Kinespring is not to reverse the arthritic damage in the joint but simply to improve patients’ symptoms and therefore help them keep going for longer, delaying the time when more major more invasive surgery, such as a knee replacement, might become necessary.
The KineSpring Medial Offloading Knee Implant
The KineSpring implant is surgically implanted
onto the medial/inner side of the knee, deep
inside/under the soft tissues.
Pre-operative X-ray showing early arthritis
on the inner (medial) side of the knee,
with medial joint space narrowing.
Post-operative X-ray with the KineSpring
prosthesis surgically implanted, showing
the spring 'cranking open' and offloading
the medial compartment.
There are a number of advantages with the KineSpring vs the more traditional (old fashioned) concept of a realignment osteotomy:-
1) First, surgical implantation of a KineSpring implant is easier, less invasive and quicker than an osteotomy, which is a bigger ‘nastier’ operation.
2) The rehab after a KineSpring implant is much easier and quicker than that required after an osteotomy. With an osteotomy, the patient is kept on reduced weight bearing with crutches and with their knee in a hinged brace for the first 6 to 8 weeks, before proper rehab can then start. With the KineSpring, full weight bearing is commenced ASAP after the surgery and patient mobilisation is far easier and more rapid.
3) Although realignment osteotomy improves patients’ symptoms and delays the need for knee replacement surgery, the subsequent results of knee replacement surgery are actually worse and the surgery itself is more difficult if an osteotomy has already been performed previously. The KineSpring, however, does not cut or damage the bone at all, and hence it does not adversely affect the results of subsequent joint replacement.
For some younger patients with premature medial arthritis who might potentially need subsequent soft tissue reconstructive surgery (e.g. meniscal transplantation +/- articular cartilage grafting), implantation of the KineSpring may buy them additional time before actually needing the biological reconstruction, as well as improving the loading profile in the medial side of the knee, making the medial compartment a better and more appropriate environment for graft implantation.
The main potential disadvantage of the KineSpring implant is that it is new, and therefore the clinical results so far are only relatively short-term. Although the early results appear to be highly favourable, we will only really know for sure what the long-term outcomes are in a further 5 to 10 years’ time. In the meantime, all patients receiving a KineSpring implant within our practice will be kept on a specific register, to follow their outcomes, and in addition there are currently excellent high quality clinic trials ongoing in both Europe and the U.S., the results of which are eagerly anticipated.
Mr McDermott has been fully trained in the use of the KineSpring implant, and we are happy to announce that the KineSpring is now available to our patients within our practice.
For further information about the KineSpring CLICK HERE to see Moximed’s KineSpring website
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