Unicondylar Knee Replacement

Unicondylar Knee Replacement

Introduction

Unicondylar/unicompartmental knee replacement simply means that only a part (one of three parts) 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. One of the more notable advances has been robotic assistance with partial knee replacements. Since only a part of the knee is being replaced, it is important for that implant to articulate perfectly with the remainder of the native joint. Dr. Patel often uses robotic assistance for his partial knee replacements to allow for the most precise and accurate placement.

Arthritis

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

  • Trauma (fracture)
  • Increased stress e.g., overuse, overweight, etc.
  • Infection
  • Connective tissue disorders
  • Inactive lifestyle- e.g., obesity, as additional weight puts extra force through your joints which can lead to arthritis over a period of time
  • Inflammation, e.g., rheumatoid arthritis

In an Arthritic Knee

  • The cartilage lining is thinner than normal or completely absent. The degree of cartilage damage and inflammation varies with the type and stage of arthritis
  • The capsule of the arthritic knee is swollen
  • The joint space is narrowed and irregular in outline; this can be seen in an X-ray image
  • Bone spurs or excessive bone can also build up around the edges of the joint

The combinations of these factors make the arthritic knee stiff and limit activities due to pain or fatigue.

Diagnosis

  • The diagnosis of osteoarthritis is made on history, physical examination & X-rays
  • There is no blood test to diagnose osteoarthritis (wear & tear arthritis)

Advantages & Disadvantages

The decision to proceed with knee replacement surgery is a cooperative one between you, Dr. Patel, 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, injections, 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

Dr. Patel 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. You will have a pre-operative visit prior to surgery to discuss these special accommodations as well as instructions on continuing medications.

Day of Surgery

  • This is typically performed as an outpatient procedure and you will go home within hours of surgery
  • 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
  • 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 1.5 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 robotic assistance.

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 irrigated and closed, and the knee dressed and bandaged.

Post-Operation Care

Once stable, you will be discharged home. You will sit out of bed and start moving you knee and walking on day 1 of surgery. The dressing will be removed usually on the 5th 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 DVTs.

Bending your knee is variable, but by 2 weeks it should bend to 90 degrees. The goal is to obtain 120-135 degrees of movement.

More physical activities, such as sports previously discussed may take 3 months to be able to do comfortably.

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 Dr. Patel 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 well-being. 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

Local Complications

  • Surgical site infection
  • Blood clots (deep venous thrombosis)
  • Fractures or breaks in the bone
  • Stiffness in the knee
  • Wearing of implants
  • Wound irritation or breakdown
  • Cosmetic appearance
  • Leg length inequality
  • Dislocation
  • Patella problems
  • Ligament injuries
  • Damage to nerves and blood vessels

Discuss your concerns thoroughly with Dr. Patel prior to surgery.

Summary

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 be regarded as part of your treatment plan as it may 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, Dr. Patel, 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.