The Artificial Knee Joint: the Operation, Treatment Steps and Consequences
Treatment of knee-joint arthrosis
The progression of the disease can be slowed, and a tolerable state achieved for the patient, via changes in the patient's lifestyle, drug therapy, physiotherapeutic treatment or orthopedic devices. The elimination of pain is in the foreground here.
The first important point is to combat the irritation the internal joint membrane and thus the pain. Various medications, such as non-steroid anti-rheumatic drugs (NSAR) or cortisone, can be administered. Parallel to drug therapy, physical measures, e.g. cold or heat treatments or electrotherapy, can be used.
In this context a very important role is assigned to physiotherapy which preserves joint mobility and strengthens the muscles. The joint must be moved in a selective manner which does not place too much stress on it. In addition to the physiotherapeutic exercises, you can also take part in sports which do not place excessive strain on the joints, such as swimming or cycling.
In some cases, the patient's symptoms can be alleviated by a minor surgical procedure. For example, a destroyed meniscus can be removed during arthroscopic surgery and, if necessary, the cartilage can be smoothened somewhat. In patients with a leg deformity such as knock knees or bowlegs, correcting the leg axis can stop the one-sided strain on the knee and lessen pain.
New techniques - such as composite grafts containing both bone and cartilage or modification of the cartilage with genetic engineering - offer promise in mild cases. However, they are not suitable for most arthroses which occur with advancing age. Diagnostic investigation is carried out by arthroscopy ( i.e. endoscopic joint examination).
Treatment of knee joint arthrosis with an artificial knee joint
When all of the conservative measures described above no longer help to alleviate the pain, and the patient's mobility and ability to walk - and thus ultimately his or her quality of life - are severely compromised, i.e. when the joint is severely damaged, your physician will recommend the implantation of an artificial knee joint. The main reason for undergoing this operation is to enjoy freedom from pain again and to regain good mobility. A second aim is the correction of leg deformities. A large number of patients have already experienced the enormous advantages offered by an artificial hip joint. It took medical engineers a bit longer to develop a successful artificial knee joint. This is because the knee joint is somewhat more complex than the hip joint. Nevertheless, the results attained with the artificial knee joint are now nearly as good as those achieved with the artificial hip joint. A successful knee joint replacement operation takes away your pain and gives you good mobility in the knee joint again. The only limitation is the no longer complete range of motion, e.g. it may be somewhat uncomfortable for you to kneel or to sit on your heels. These are limitations you will scarcely notice during daily life. However, artificial joints can never achieve the perfection of the original joint.
Special features of the LCS artificial knee
The model «LC knee» from DePuy was developed by Dr. F.F. Buechel and Dr. M. Pappas in New Jersey (USA) in 1977 and has been implanted more than 100,000 times since then. Today it is the most sold artificial knee joint with movable sliding bearings. The difference between the LCS artificial knee joint and other knee implants is that the plastic insert between the femur and the tibia, as well as the plastic insert on the patella, can be moved. This guarantees that the implant materials will be worn down to a minimal extent and, at the same time, will remain anchored in the body for a maximum period of time. The abbreviation LCS stands for «low contact stress».
Materials
The LCS knee for patients with a metal allergy consists of an extremely strong cobalt-chrome-molybdenum alloy containing a small amount of nickel. Allergies can be virtually excluded. The plastic parts are made of ultra-high-molecular-weight polyethylene (UHMWPE).
Despite the high incidence of contact allergies against jewelry metals, genuine allergies to metals are fortunately very rare. For patients with a known or reliably demonstrated allergy to nickel, cobalt or chrome, the LCS knee is available with a surface coating of titanium nitride. This version contains exclusively non-allergenic materials.
What happens during a knee joint replacement operation?
During a knee joint replacement operation, the damaged bone and remaining cartilage are superficially removed.
The remaining bones are shaped so that the parts of the artificial knee joint fit securely. The ligaments in the knee joint are generally left intact in order to preserve a rolling-sliding movement sequence that is as natural as possible. The upper end of the tibia is covered with a metal place anchored in the bone by a specially formed short stem. On top of this metal place, either one movable plastic bearing covering the entire surface or two independent plastic sliding bearings are placed. Friction between the femoral and tibial components of the artificial knee joint is thus minimized. Following appropriate pretreatment of the femur, a metal implant in the shape of a healthy femur is placed on the thigh bone. The back side of the kneecap (patella) can be replaced by a plastic patella, which them slides on the metal plate on the femur during movement of the knee joint.
As a rule the operation is performed to promote bony ingrowth into the specially structured surface of the implant components, a process which anchors the artificial joint in the bone. This is an example of cementless fixation. It is also entirely possible, however, to fix the parts of the artificial knee joint to the bone with a special cement.
Depending on the degree to which your knee joint has been destroyed, your physician will decide whether replacement of the total knee joint or only part of the knee joint (with a unicondylar implant) is necessary. Sometimes the surgeon cannot make this decision until the operation has already begun and he or she can look into the knee.
Depending on the size of your knee joint, moreover, there are various sizes of artificial knee joints available. The modular LCS system offers additional possibilities for enlarging the implant to adapt it to the degree of destruction found in the knee.
Risks and possible complications of an artificial knee joint
Every operation, no matter how minor, poses a certain risk. A distinction is made between a general risk of surgery and a specific risk related to the artificial knee joint.
The general risks of surgery include thromboses and embolisms. The surgical team attempts to prevent these as far as possible by administering anticoagulants during the operation. Infections and injuries to blood vessels and nerves are very rare, thanks to advances in medicine and the extensive experience gained with knee joint operations.
The special problems associated with knee joint replacement include adhesions in the knee joint; these can occur if the knee is not exercised sufficiently during the first several days after the operation. If improved mobility cannot be achieved despite intensive physiotherapy, a brief anesthesia can be administered - i.e. pain eliminated - and the knee joint moved cautiously through the entire range of motion to free the adhesions. This procedure is known as mobilization under anesthesia. When performed by an experienced physician, it is not associated with any major risks.
In very rare cases, calcific deposits are detected in the muscles which can cause a limitation of movement. If the artificial knee joint is loaded sensibly and not overloaded, and if there is good muscular guidance and firm bone, the artificial joint can be expected to have a long life.
The experienced gained with artificial knee joints to date shows that a good 90% of the patients are still satisfied with their new knee joint approximately 10 years after the operation.
Should premature loosening of the artificial joint occur for any reason, it is necessary to replace the artificial joint. This is easier if the implant belongs to a modular system. Possibly only one implant component will have to be replaced or - as has been described above - an expanded implant inserted. However, the exchange of an artificial joint is associated with a greater risk than the initial implantation.
Regular follow-up examinations and x-ray follow-up are vital in order to detect implant loosening in time.
If an implant exchange operation is performed in time, the chances that the second artificial knee joint will heal are distinctly better; this is because damage to the bone caused by a loosened artificial knee joint can be prevented by early re-operation.
You should not over-emphasize the risks. Nevertheless, every patient should be informed about his or her risks; older patients, in particular, have higher risks. The most feared complication of an artificial knee joint is infection. By administering antibiotics before the operation and in some cases after the operation as well, and carrying out the operation in special aseptic operating rooms, surgeons have succeeded in lowering the rate of infection to below 1%.
Should you suffer a broken bone near the knee joint as a result of an accident, select a hospital which has experience with knee implants if possible - ideally, experience with the system implanted in your case. For this reason, always carry your knee-joint implant pass with you.