Primary knee replacement

Knee replacement, also known as knee arthroplasty, is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve pain and disability. It is most commonly performed for osteoarthritis and also for other knee diseases such as rheumatoid arthritis and psoriatic arthritis.

In patients with severe deformity from advanced rheumatoid arthritis, trauma, or long-standing osteoarthritis, the surgery may be more complicated and carry higher risk. Osteoporosis does not typically cause knee pain, deformity, or inflammation and is not a reason to perform knee replacement

Other major causes of debilitating pain include meniscus tears, cartilage defects, and ligament tears. Debilitating pain from osteoarthritis is much more common in the elderly.

Knee replacement surgery can be performed as a partial or a total knee replacement. In general, the surgery consists of replacing the diseased or damaged joint surfaces of the knee with metal and plastic components shaped to allow continued motion of the knee.

The operation typically involves substantial postoperative pain, and includes vigorous physical rehabilitation. The recovery period may be 12 weeks or longer and may involve the use of mobility aids (e.g. walking frames, canes, crutches) to enable the patient's return to preoperative mobility. It is estimated that approximately 82% of total knee replacements will last 25 years.

Medical uses:

X-ray of total knee replacement, anteroposterior view (left) and lateral view (right). The incision for knee replacement surgery

Knee replacement surgery is most commonly performed in people with advanced osteoarthritis and should be considered when conservative treatments have been exhausted.

Total knee replacement is also an option to correct significant knee joint or bone trauma in young patients. Similarly, total knee replacement can be performed to correct mild valgus or varus deformity. Serious valgus or varus deformity should be corrected by osteotomy. Physical therapy has been shown to improve function and may delay or prevent the need for knee replacement. Pain is often noted when performing physical activities requiring a wide range of motion in the knee joint.

Knee Replacement Revision Surgery:

Although today’s implants are designed to last many years, it’s possible that at some point in the future — typically 15 to 20 years or more — your prosthetic will break or wear out. If you’re overweight or you engage in high-impact activities such as running or court sports, the device may fail sooner.

When a knee replacement no longer functions correctly, revision surgery is often required. During this procedure, a surgeon replaces the old device with a new one.

Revision surgery isn’t something to take lightly. It’s more complicated than a primary (or initial) total knee replacement (TKR) and entails many of the same risks. Nevertheless, it’s estimated that more than 22,000 knee revision operations are performed in the United States each year. Over half of these procedures take place within two years of the initial knee replacement.

Revision surgery is more complicated than initial surgery:

It’s important to note that a revision knee replacement doesn’t provide the same lifespan as the initial replacement (usually about 10 years rather than 20). The accumulated trauma, scar tissue, and mechanical breakdown of components lead to diminished performance. Revisions are also more susceptible to complications.

A revision procedure is typically more complex than the original knee replacement surgery because the surgeon must remove the original implant, which would have grown into the existing bone.

In addition, once the surgeon removes the prosthesis, there is less bone remaining. In some instances, a bone graft — transplanting a piece of bone transplanted from another part of the body or from a donor — might be required to support the new prosthesis. A bone graft adds support and encourages new bone growth.

However, the procedure requires additional preoperative planning, specialized tools, and greater surgical skill. The surgery takes longer to perform than a primary initial knee replacement.

If a revision surgery is necessary, you’ll experience specific symptoms. Indications of excessive wear or failure include:

  • Diminished stability or reduced function in the knee
  • Increased pain or an infection (which usually occurs soon after the initial procedure)
  • A bone fracture or outright device failure

In other cases, bits and pieces of the prosthetic device may break off and cause tiny particles to accumulate around the joint.

Reasons for a revision:

Short-term revisions: infection, implant loosening from failed procedure, or a mechanical failure

An infection will usually present itself within days or weeks of surgery. However, infection can also occur many years after surgery.

Infection following knee replacement can cause severe complications. It’s generally caused by bacteria that settle around the wound or within the device. Infection can be introduced by contaminated instruments or by people or other items within the operating room.

Because of extreme precautions taken in the operating room, infection rarely occurs. However, if an infection takes place, it can lead to a buildup of fluids and potentially a revision.

If you notice any unusual swelling, tenderness, or fluid leakage, contact your surgeon immediately. If your surgeon suspects that there’s a problem with your existing artificial knee, you’ll be asked to undergo an examination and assessment. This involves X-rays and possibly other imaging diagnostics such as a CT or MRI scan. The latter can provide important clues about bone loss and determine whether you’re a suitable candidate for a revision.

People who experience fluid buildup around their artificial knee usually undergo an aspiration procedure to remove the fluid. The doctor sends the fluid to a lab to determine the type of infection and whether a revision surgery or other treatment steps are in order.

Long-term revisions: pain, stiffness, loosening due to wear of mechanical components, dislocation: Long-term wear and loosening of the implant can occur over years.

Various sources have published statistics on the long-term revision rates for knee replacement. According to the U.S. Department of Health and Human Services Agency for Healthcare Research and Quality (AHRQ), and by observing TKR patients over an eight-year period ending in 2003, the long-term revision rate is 2 percent for five or more years.

Based on a meta-analysis of worldwide joint registry databases, published in 2011, the revision rate is 6 percent after five years and 12 percent after ten years.

Healthline’s analysis of approximately 1.8 million Medicare and private pay records found that the rate of revision for all age groups within five years from surgery is about 7.7 percent. The rate increases to 10 percent for those age 65 and older.

The data on long-term revision rates varies and depends on numerous factors, including the ages of those observed. The chances for a revision are lower for younger people. You can reduce future problems by maintaining your weight and avoiding activities that place undue stress on the joint, such as running, jumping, court sports, and high-impact aerobics.

During a process called aseptic loosening, the bond between the bone and the implant breaks down as the body attempts to digest the particles. When this event takes place, the body also begins to digest bone, which is known as osteolysis. This can lead to a weakened bone, fracture, or problems with the original implant. Aseptic loosening doesn’t involve an infection.

Revision surgery for infection:

Typically, a revision required because of infection involves two separate operations: Initially, the orthopedist removes the old prosthesis and inserts a polyethylene and cement block known as a spacer that has been treated with antibiotics. Occasionally, they’ll make cement molds like the original prosthesis and insert antibiotics in that and implant it as the first stage.

During the second procedure, the surgeon removes the spacer or molds, reshapes and resurfaces the knee, and then implants the new knee device. The two procedures usually take place about six weeks apart. Inserting the new device typically requires 2 to 3 hours in surgery, compared to 1 1/2 hours for a primary knee replacement.

If you require a bone graft, the surgeon will either take bone from another part of your own body or use bone from a donor, usually obtained through a bone bank. The surgeon might also install metal pieces such as wedges, wires, or screws to reinforce the bone for the implant or fasten the implant to the bone. A revision requires the surgeon to use a specialized prosthetic device.

Knee revision surgery complications:

Complications that may follow knee revision surgery are similar to those for knee replacement. They include:

  • Deep vein thrombosis
  • Infection in the new implant
  • Implant loosening, which your at higher risk of if you’re overweight
  • Dislocation of the new implant, the risk of which is twice as high for revision surgery as for an initial TKR
  • Additional or more rapid loss of bone tissue
  • Bone fractures during the operation that could occur if the surgeon must use force or pressure to remove the old implant
  • Difference in leg length resulting from shortening of the leg with the new prosthesis
  • Formation of heterotopic bone, which is bone that develops at the lower end of the femur following surgery (Joint infections after surgery increase risk for this.)
Morbidity and mortality rates As with primary knee replacement, the 30-day mortality rate following knee revision surgery is low, between 0.1 percent and 0.2 percent, according to Healthline’s analysis of Medicare and private pay records. The estimated complications rates are:
  • Deep venous thrombosis: 1.5 percent
  • Deep infection: 0.97 percent
  • Loosening of the new prosthesis: 10 to 15 percent
  • Dislocation of the new prosthesis: 2 to 5 percent

Recovery and rehabilitation

Afterwards, you’ll undergo a similar recovery and rehabilitation process as someone who receives a primary knee replacement. This includes medication, physical therapy, and the administration of blood thinners to prevent clots. You’ll initially require an assistive walking device such as a cane, crutches, or walker, and you’ll likely be in physical therapy for three months or longer.

As with the original knee replacement, it’s important to stand and walk as quickly as possible. Pressure, compression, or resistance is needed for the bone to grow and properly bond with the implant.

The length of recovery after revision knee surgery varies in comparison to a person’s first knee replacement. Some individuals take longer to recover from revision surgery, while others recover more rapidly and experience less discomfort than during the initial TKR.

If you think you may require a revision, speak to your doctor and review your condition to understand whether you’re a good candidate for the surgery.

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