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Unicondylar knee replacement simply means that only a part of the knee joint is replaced through a smaller incision than would normally be used for a total knee replacement.
Unicondylar knee replacements have been performed since the early 1970′s with mixed success. Over the last 25 years implant design, instrumentation, and surgical techniques have improved markedly making it a very successful procedure for unicompartmental arthritis. Recent advances allow us to perform this through a smaller incision and therefore are not as traumatic to the knee making recovery quicker.
Total knee replacement surgery replaces the ends of the femur (thigh bone) and tibia (shin bone) with plastic inserted between them and usually the patella (kneecap).
Arthritis is a general term covering numerous conditions where the joint surface (cartilage) wears out. The joint surface is covered by a smooth articular surface that allows pain-free movement in the joint.
When the articular cartilage wears out, the bone ends rub on one another and cause pain. There are numerous conditions that can cause arthritis and often the exact cause is never known. In general, but not always, it affects people as they get older (osteoarthritis).
Other Causes Include
In an Arthritic Knee
The decision to proceed with knee replacement surgery is a cooperative one between you, your surgeon, family, and your local doctor.
The benefits following surgery are relief of symptoms of arthritis. These include
Prior to surgery you will usually have tried some conservative treatments such as analgesics, weight loss, anti-inflammatory medications, modification of your activities, canes or physical therapy.
The big advantage is that if for some reason it is not successful or fails many years down the track it can be revised to a total knee replacement without difficulty.
Who is not suitable?
Each knee is individual and knee replacements take this into account by having different prosthetic sizes available for your knee. If there is more than the usual amount of bone loss sometimes extra pieces of metal or bone are added.
Surgery is performed under sterile conditions in the operating room under spinal or general anesthesia. You will be on your back and a tourniquet will be applied to your upper thigh to reduce blood loss. Surgery will take approximately two hours.
When you wake up, you will be in the recovery room with IV’s in your arm, a tube (catheter) in your bladder, and a number of other monitors to check your vitals. You will usually have a button to press for pain medication called a PCA machine (Patient Controlled Analgesia).
Once stable, you will be taken to a room. The post-op protocol is surgeon dependent, but in general your drain will come out at 24 hours and you will sit out of bed and start moving your knee and walking on it within a day or two of surgery. The dressing will be reduced usually on the second post-op day to make movement easier. Your rehabilitation and mobilization will be supervised by a physical therapist.
To avoid lung congestion, it is important to breathe deeply and cough up any phlegm you may have.
Your orthopaedic surgeon will use one or more measures to minimize blood clots in your legs, such as inflatable leg coverings, stockings, and injections into your abdomen to thin the blood and prevent clots or DVT’s, which will be discussed in detail in the complications section.
A lot of the long term results of knee replacements depend on how much work you put into it following your operation.
Usually you will remain in the hospital for 3 to 5 days. Depending on your needs, you will then return home or proceed to a rehabilitation facility. You will need physical therapy on your knee following surgery.
You will be discharged on a walker or crutches and usually progress to a cane at six weeks.
Your sutures are sometimes dissolvable but if not, are removed at approximately 10 days.
Bending your knee is variable, but by 6 weeks it should bend to 90 degrees. The goal is to obtain 110 to 115 degrees of movement.
Once the wound is healed, you may shower. You can drive at about 6 weeks, once you have regained control of your leg. You should be walking reasonably comfortably by 6 weeks.
More physical activities, such as sports may take 3 months to be able to do comfortably.
When you go home you need to take special precautions around the house to make sure it is safe. You may need grab bars in your bathroom or modify your sleeping arrangements especially if they are upstairs.
You will usually have a 6-week checkup with your surgeon, who will assess your progress. You should continue to see your surgeon as recommended to check your knee and take X-rays. This is important as sometimes your knee can feel excellent, but there can be a problem only recognized on X-ray.
You are always at risk of infections especially with any dental work or other surgical procedures where germs (bacteria) can get into your blood stream and find their way to your knee.
If you have any unexplained pain, swelling, or redness or if you feel generally poor, you should see your doctor as soon as possible.
Complications can be medical (general) or local complications specific to the Knee
Medical complications include those of the anesthetic and your general wellbeing. Almost any medical condition can occur so this list is not complete. Complications include:
Infection can occur with any operation. If it occurs, it can be treated with antibiotics but may require further surgery.
Blood Clots (Deep Venous Thrombosis)
These can form in the calf muscles and can travel to the lung (pulmonary embolism). These can be serious and even life threatening. If you get calf pain or shortness of breath at any stage, you should notify your surgeon.
Fractures or Breaks in the Bone
Fractures or breaks can occur during surgery or afterwards if you fall. To repair these, you may require surgery.
Stiffness in the Knee
Ideally, your knee should bend beyond 100 degrees but on occasion, it may not bend as well as expected. Sometimes manipulations are required. This means going to the operating room where the knee is bent for you under anesthesia.
The plastic liner eventually wears out over time, usually 10 to 15 years, and may need to be changed.
Wound Irritation or Breakdown
The operation will always cut some skin nerves, so you will inevitably have some numbness around the wound. This does not affect the function of your joint. You can also experience aching around the scar. Vitamin E cream and massage can help reduce this.
Occasionally, you can get reactions to the sutures or a wound breakdown that may require antibiotics or rarely further surgery.
The knee may look different than it was because it is put into the correct alignment to allow proper function.
Leg Length Inequality
This is also due to the fact that a corrected knee is straighter and is unavoidable.
An extremely rare condition where the ends of the knee joint lose contact with each other or the plastic insert can lose contact with the tibia (shinbone) or the femur (thigh bone).
The Patella (kneecap) can dislocate. This means it moves out of place and it can break or loosen.
There are a number of ligaments surrounding the knee. These ligaments can be torn during surgery or break or stretch out anytime afterwards. Surgery may be required to correct this problem.
Damage to Nerves and Blood Vessels
Rarely these can be damaged at the time of surgery. If recognized they are repaired but a second operation may be required. Nerve damage can cause a loss of feeling or loss of movement below the knee and can be permanent.
Discuss your concerns thoroughly with your orthopaedic surgeon prior to surgery.
Surgery is not a pleasant prospect for anyone, but for some people with arthritis, it could mean the difference between leading a normal life or putting up with a debilitating condition. Surgery can help to restore function to your damaged joints as well as relieve pain.
Surgery is only offered once non-operative treatment has failed. It is an important decision to make and ultimately it is an informed decision between you, your surgeon, family, and medical practitioner.
Although most people are extremely happy with their new knee, complications can occur and you must be aware of these prior to making a decision. If you are undecided, it is best to wait until you are sure this is the procedure for you.