Knee Replacement Surgery

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Knee replacement surgery involves replacing an injured or diseased joint with an implant to relieve pain and improve movement. However, some knee implants can cause complications and fail early.

The knee is the largest, most complex joint in the body. It is also the most stressed. When the knee joint is damaged, people can experience pain and decreased range of motion. This can make it difficult to perform daily tasks like standing, climbing stairs or walking. In cases like these, a doctor may recommend knee replacement surgery. Knee replacement surgery, also called arthroplasty, involves replacing the damaged weight-bearing parts of the knee joint with an artificial implant called a prosthesis.

The first knee replacement surgery was done in 1968. Since then, more advanced surgical techniques and implants have made this surgery one of the most successful procedures in medicine. In 2010, almost 700,000 people had knee replacement surgery, and this number is projected to grow each year. There are several reasons why someone might need to have knee replacement surgery. The most common reason is arthritis that damages the cartilage and bones in the joint.

Some common knee problems that might necessitate surgery include:
Osteoarthritis is age-related wear and tear on the knee joint and usually occurs in people older than 50.
Rheumatoid arthritis causes the immune system to attack the membranes in the knee and creates damage and cartilage wear.
Traumatic arthritis results from a serious knee injury (fracture, ligament damage, meniscus tear). This weakens the joint.
Avascular necrosis (AVN) is a condition that affects teenagers and young adults. The bones in the knee become soft, causing the bone and cartilage to wear down. This usually resolves during adulthood, but in some cases the wear on the bone is extensive and arthritis sets in.
Abnormal formation or alignment, sometimes called being “knock-kneed” or “bow-legged,” creates high stress on joint and causes abnormal wear.

While the majority of people experience an improvement in range of motion and quality of life from knee replacement surgery, some people may experience complications  such as infection or loosening of the implant. Loosening can occur if the wrong implant is used or if the prosthesis is faulty. Manufacturers have recalled defective knee implants because of loosening. Many people who have had these implants and suffered problems have chosen to file lawsuits. Some companies involved in these suits or recalls include Zimmer, Stryker and Smith & Nephew.

Surgery

Knee replacement surgery can involve one or more damaged knee surfaces. The three major knee surfaces are the lower end of the thigh bone (femur), upper end of the shin bone (tibia) and the knee cap (patella). At the ends of these bones, there is cartilage. In between the femur and tibia, there are small c-shaped pads called menisci. The menisci absorb shock and cushion the joint. If any of these parts becomes damaged or worn, moving the knee becomes painful and difficult. Knee replacement surgery creates new surfaces on the bones using metal components and replaces cartilage with smooth plastic. For this reason, some doctors may refer to the procedure as a knee “resurfacing” because only the surfaces of the bones are replaced.  In some cases, more of the bone made need to be replaced if it is too damaged for the surgeon to spare. The damaged bone is then cut and replaced. Extra bone may also need to be cut to fit specific prosthesis models.

When someone considers surgery, the orthopaedic surgeon will evaluate the potential surgical candidate’s medical history, and the knee’s motion, general health and stability. The doctor will also perform an X-ray or MRI to determine the condition of the ligaments, cartilage and bone in the joint. If the person is a candidate for surgery, the doctor will also explain all of the different surgical procedures, their risks, benefits and potential disadvantages.

Knee replacement surgery usually takes 1 to 2 hours, and general anesthesia is used. In some cases, the surgeon may use a robotic arm system that can help more accurately determine the damaged area and align the implants. This type of surgery is called computer-assisted surgery (CAS). Surgeons can obtain a 3-D model of the patient’s joint that allows them to align the implant more accurately.

There are several types of knee replacement devices (prostheses), including total implants and partial implants. Depending on the patient’s age, weight and activity level, the model will vary. Doctors will recommend a partial or total knee replacement surgery depending on the number of surfaces that are damaged. A specific model of prosthetic may also be recommended depending on the amount of damaged bone and cartilage that needs to be replaced.

Total Knee Replacement Surgery

A doctor usually recommends total knee replacement surgery if all three of the joint’s compartments are damaged. This procedure replaces the end of the tibia, femur and the back side of the patella. During a total knee surgery, the surgeon makes an incision that is between 8 and 12 inches to expose the knee joint. The bottom of the femur is resurfaced and fitted with a metal piece (femoral head). Depending on the condition of the bone, the surgeon may have to cut more of the damaged bone off the femur. Next, a small piece of bone is cut from the top of the tibia and a flat, weight-bearing metal piece is screwed into the top (tibial plate). Then, a flat piece of medical-grade plastic (menisci replacement plate) is placed in between these two pieces to absorb shock and allow the knee to glide smoothly. The back side of the patella facing the end of the femur is also resurfaced and fitted with a small plastic button.

Some medical centers like Rush University Medical Center  in Chicago perform minimally invasive surgery for a total knee replacement with only a 3- to 4- inch incision. Surgeons cut less muscle and tissue, which leads to less blood loss, increased range of motion and a shorter hospital stay. Many people go home the same day. This procedure is not as widely used as traditional surgery because there is a higher risk for poor implant placement. Only specialized medical centers typically offer this surgical option.

Generally, total knee replacement surgery will include these basic steps:
1. Damaged cartilage is removed, along with a small amount of bone from the tibia and femur.
2. Damaged bone surfaces are replaced with metal components, and cartilage is replaced by medical-grade plastic.
3. Depending on the case, some surgeons may resurface the under side of the kneecap (patella) with a plastic disk.
4. A piece of smooth, medical-grade plastic is placed in between the metal parts to facilitate ease of movement.

Partial Knee Replacement Surgery

When a person has a partial knee replacement, the doctor only resurfaces one or two compartments of the knee. The surgeon spares as much of the healthy tissue and bone as possible, and this may help retain range of motion, encourage more natural function and decrease healing time. However, the other parts of the knee may become arthritic at a later date, and another surgery to resurface those portions of the knee might be required.

Depending on the number of surfaces damaged, there are three general types of partial knee surgery:
Unicompartmental surgery replaces one side (compartment) of the knee.
Bicompartmental surgery replaces both sides (compartments) of the knee.
Patellofemoral surgery replaces the end of the thigh bone with a metal piece and resurfaces the back of the kneecap (patella).

Each of these procedures requires a different prosthesis and surgical technique. For a partial knee replacement, the incision is much smaller than for a total knee replacement and is usually only about 3 to 4 inches. After making the incision, the surgeon will first make sure that the damage can be corrected with a partial procedure. If that’s the case, the damaged parts of the bone are then capped with metal pieces, and a plastic piece is inserted between the two metal components.

Recovering from Surgery

After the procedure, the patient can expect to be given antibiotics for about a day after surgery and medication (anticoagulants) to control pain and prevent blood clots. A drain to stop fluid from building up around the knee may be inserted. Some people may have a urinary catheter to minimize the need to stand after the procedure. To help retain flexibility and range of motion, some surgeons will recommend a continuous passive motion machine (CPM) that will slowly bend and straighten the knee joint while keeping it supported.

While each individual is different, short-term recovery is usually between 2 and 3 months. After this time, people can typically walk without an aid or use over-the-counter pain medications instead of stronger prescription medications. Long-term recovery takes about 6 to 12 months. For most people, the knee is sufficiently healed after long-term recovery, and they can resume normal activities. The time it takes to recover enough to return to work depends on the individual and their job. A person who works in an office and spends most of their day sitting at a desk can probably return to work sooner. If the job is more physically demanding, doctors may recommend more healing time before returning to work.

Managing knee pain following surgery is important for a good recovery, and doctors will give advice on controlling and living with any discomfort. Recovery also involves physical therapy and a home exercise routine to strengthen the joint and ensure that the knee’s range of motion is as good as it can be. Rehabilitation after surgery will likely last several months.

After recovery, some people may notice that their new joint is not as flexible as their old knee. This is normal because an implanted joint is not as flexible as a healthy knee joint. Some of the factors that influence range of motion after surgery include age and how flexible the joint was prior to the operation.

Complications Following Surgery

Just like any surgical procedure, knee replacement surgery can have complications. Complications are more likely to occur when having a total knee replacement than a partial knee replacement. Some of these complications occur because of the surgery itself. Others occur because of a faulty implant. If the person has chronic illnesses, the risk of complications increases. For example, a person with sleep apnea — a sleep disorder that causes a person to have pauses in breathing while asleep — has a higher in-hospital mortality risk following joint replacement surgery. If the person has revision surgery, the risk of complications rises.

Common complications include:
Blood clots Nerve damage
Poor joint mobility Different leg lengths

More serious complications like joint infection occur in less than 2 percent of patients. Infection is considered one of the most serious complications that can occur after surgery. When organisms enter the wound during surgery, they can attach to the prosthesis and are difficult to kill with antibiotics. Symptoms of early joint infection include pain and swelling in the joint, a leaking wound and fever. The implant may have to be removed to cure treat the infection. Other serious conditions such as heart attack or stroke occur rarely. Complications can also arise if the implant fails and causes loosening of the joint.

Revision Surgery

Following knee replacement surgery, a second surgery might be required to adjust or replace the implant if it fails. This corrective surgery is called revision surgery.  In 2010, there were 67,100 knee revisions performed in the United States. Revision surgery is more complicated and difficult to perform than original (primary) surgery and usually takes about three hours. This procedure also takes more planning, and special implants and tools are required. The implants used in revision surgery have thicker, longer stems to provide more stability and compensate for weaker ligaments and increased bone loss.

The number of people requiring this procedure continues to rise as more people receive knee implants each year. About 67,000 people required knee replacement revision surgeries in the Unites States in 2010, a 5 percent increase from 2009.  More than 600,000 had primary knee replacement surgery in 2010. Projected hospital costs for total knee revision surgeries are expected to exceed $2 billion by 2030. Because primary knee replacement surgeries are expected to grow by 673 percent to 3.48 million procedures annually by 2030, revision surgery is also expected to grow by 601 percent.

  • In 2010, there were 67,000 knee replacement revision surgeries.
  • In 2030, 3.48 million knee replacements are projected to be completed.
  • In 2006, the average cost of revision surgery was $74,000.
  • Revision surgery has a higher rate of complications than primary surgery.
Complications arising from defective implants that may require revision surgery include:
Bone Fracture Component breaking
Dislocation Joint instability
Joint pain Joint swelling
Loosening of implant Misaligned component

Implants can fail because of a patient’s active lifestyle or because of normal wear and tear. The average life span of an implant is 15 to 20 years, which means people who receive a new knee when they are young and active will require revision surgery at some point, often sooner than 15 years. However, implants can also fail due to a faulty design that causes loosening and abnormal wear. For example, some uncemented knee implants are designed for the bone to “grow” into the space and prevent loosening. Because of poor design, the bone may not fuse properly with the implant and loosening may occur. This can cause pain and instability, and bone fractures can occur.

Because knee implants are regulated under the Food and Drug Administration’s (FDA) 510(k) program, manufacturers are not required to conduct tests on them before releasing them to the public. As a result, surgeons and patients may be unaware that a device may not work properly until it has already been implanted.

A second surgery to remove a faulty implant can be costly, and the procedure for a revision surgery takes longer and has the potential for more complications. After identifying their implants as defective or faulty, many people elect to file lawsuits or claims against the manufacturers to cover the cost of surgery, the pain and discomfort of recovery, and loss of wages.

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