Partial Knee Replacement

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 smaller incisions and therefore the procedure is not as traumatic to the knee making recovery quicker.

Advantages Disadvantages

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

Severe pain that limits your everyday activities including walking, shopping, visiting friends, getting in and out of chair, gardening, etc.
Pain waking you at night
Deformity- either bowleg or knock knees
Stiffness

Prior to surgery you will usually have tried some conservative treatments such as simple analgesics, weight loss, anti-inflammatory medications, modification of your activities, canes or physical therapy.

Advantages

Smaller operation
Smaller incision
Not as much bone removed
Shorter hospital stay
Shorter recovery period
Blood transfusion rarely required
Better movement in the knee
Feels more like a normal knee
Less need for physiotherapy
Able to be more active than after a total knee replacement

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.

Disadvantages

Not quite as reliable as a total knee replacement in taking away all pain long term results not quite as good as total knee

Candidates for Partial Knee Replacement

Who is suitable?

Ideally should be over 50 years of age
When pain and restricted mobility interferes with your lifestyle
One compartment involved clinically and confirmed on X-ray

Who is not suitable?

Patients with arthritis affecting more than one compartment
Patients with severe angular deformity
Patients with inflammatory arthritis e.g.. rheumatoid arthritis
Patients with an unstable knee
Patients who have had a previous osteotomy
Patients who are involved in heavy work or contact sports

Preparation for surgery

Pre-operation

Your surgeon will send you for routine blood tests and any other investigations required prior to your surgery
You will be asked to undertake a general medical check-up with a physician
You should have any other medical, surgical or dental problems attended to prior to your surgery
Make arrangements for help around the house prior to surgery
Cease aspirin or anti-inflammatory medications 10 days prior to surgery as they can cause bleeding
Cease any naturopathic or herbal medications 10 days before surgery
Stop smoking as long as possible prior to surgery

Day of Surgery

You will be admitted to the hospital usually on the day of your surgery
Further tests may be required on admission
You will meet the nurses and answer some questions for the hospital records
You will meet your anesthetist, who will ask you a few questions
You will be given hospital clothes to change into and have a shower prior to surgery
The operation site will be shaved and cleaned
Approximately 30 minutes prior to surgery, you will be transferred to the operating room

Surgical Procedure

Each knee is individual and knee replacements take this into account by having different sizes 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 applied to your upper thigh to reduce blood loss. Surgery will take approximately two hours.

The Patient is positioned on the operating table and the leg prepped and draped.

A tourniquet is applied to the upper thigh and the leg is prepared for the surgery with a sterilizing solution.

An incision around 7 cm is made to expose the knee joint. Smaller incisions are made if the surgery is done using arthroscopy.

The bone ends of the femur and tibia are prepared using a saw or a burr.

Trial components are then inserted to make sure they fit properly.

The real components (Femoral & Tibial) are then put into place with or without cement.

The knee is then carefully closed and drains usually inserted, and the knee dressed and bandaged.

Post-operation Care

Once stable, you will be taken to the ward. The post-operative protocol is surgeon dependant, but in general your drain will come out at 24 hours and you will sit out of bed and start moving you knee and walking on it within a day or two of surgery. The dressing will be reduced usually on the 2nd 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 orthopedic 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 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 3-5 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 approx. 10 days.

Bending your knee is variable, but by 6 weeks it should bend to 90 degrees. The goal is to obtain 110-115 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 previously discussed 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 rails in your bathroom or to modify your sleeping arrangements especially if they are up a lot of stairs.

You will usually have a 6 week check up with your surgeon, who will assess your progress. You should continue to see your surgeon for the rest of your life 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 the 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.

Risks and Complications

As with any major surgery, there are potential risks involved. The decision to proceed with the surgery is made because the advantages of surgery outweigh the potential disadvantages
It is important that you are informed of these risks before the surgery takes place

Complications can be medical (general) or local complications specific to the Knee

Medical complications

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:

Allergic reactions to medications
Blood loss requiring transfusion with its low risk of disease transmission
Heart attacks, strokes, kidney failure, pneumonia, bladder infections
Complications from nerve blocks such as infection or nerve damage
Serious medical problems can lead to ongoing health concerns, prolonged hospitalization or rarely death