Total Knee Replacement
Why Do I Need a Knee Replacement?
The most common indication for knee replacement is the effect of arthritis. The most common form of arthritis is osteoarthritis. The development of osteoarthritis can be caused by many factors, including genetics, trauma, leg alignment and certain metabolic conditions.
Rheumatoid arthritis is another form of arthritis that is caused by the dysfunction of the immune system, which leads to destruction of the cartilage surfaces. Patients with this condition may need total knee arthroplasty. In either case, the destruction of the normally smooth surfaces of the knee and related inflammation result in significant pain and disability. There are many options for treatment depending on the severity of the symptoms.
When conservative options fail, the knee replacement surgery can be considered.
Goals of the Procedure
The primary goal of Total Knee Replacement (TKR) is pain relief. Once this can be achieved all other goals can fall into place. These include improved knee motion and strength.
The goals are achieved in the majority of patients who undergo TKR.
Following surgery, there is a fairly rigorous period of rehabilitation, which can take three months. Patients are assisted with this recovery by a team of health professionals.
What is Total Knee Replacement (TKR)?
Total Knee Replacement refers to a procedure that involves resurfacing of the "worn" portion of the knee. The diseased surfaces are removed and replaced with specially designed components that provide a smooth low friction surface to restore function. The femur (thigh bone), tibia (leg bone) and patella (knee cap) are resurfaced. Bone preservation cuts are made in the collateral ligaments, while muscle and tendons are left intact. Current techniques should lead to less pain and earlier restoration of function.
Total Knee Replacement (TKR)
In total knee replacement surgery, the diseased surfaces are prepared; alignment abnormalities are corrected and ligaments are balanced. Once this is completed the new surfaces are applied to the ends of the bone. The femoral component is metallic and is similar in shape, contour and size of the end of the femur (thigh bone). The tibial component goes on the top of the prepared tibia (leg bone), which can have a metallic base with polyethylene surface or be made of only polyethylene. The undersurface of the patella (knee cap) is covered with another polyethylene component.
Therefore, once completed, the knee replacement surfaces involve a metal on plastic joint articulation. The components are attached to the bone with "bone cement," which is a specialized polymer (polymethylmethaacrylate). There are systems that allow for insertion of components without bone cement but these are less commonly used due to the high success rate of cemented components.
Alternatives to Total Knee Arthroplasty
- Activity modification - some patients are able to adjust activities enough that symptoms are minimized and they are satisfied with these changes
- Braces - not all patients can benefit from this option. Special knee braces can alter forces on the knee. These braces can help in patients who have isolated single compartment. They can be uncomfortable to wear.
- Arthroscopy - this procedure is a relatively minor procedure done in an outpatient setting. Cleaning out (debridement) of arthritic cartilage tears and smoothing rough spots in the knee through small incisions can provide relief. Relief of symptoms vary from patient to patient.
- Osteotomy - this surgical procedure involves making a cut into the bone and taking out a wedge of bone (closing wedge) or making cut and distracting (opening wedge). It is based on changing the alignment of the knee in order to alter the forces on the most involved compartment. Rehabilitation can be prolonged, and patient selection is very important. It can prevent the need for knee replacement surgery or delay it.
- Unicompartmental Arthroplasty (partial knee replacement)
- Arthrodesis - this procedure involves fusing the knee joint. It is rarely done currently but can still be used as a salvage procedure with failed knee replacement (i.e. infections)
- Anesthesia - the choice of anesthesia is based on many factors including patient preference, medical condition of patient and surgeon preference. St. Vincent’s has implemented Continuous Anesthesia to help ease pain from joint surgery. The newly implemented Continuous Regional Block Program at St. Vincent’s Medical Center is having a positive impact on the patient-care experience after orthopedic surgery. Patients who select this form of pain management are better able to handle the first sessions of physical therapy recommended soon after surgery, which have traditionally been painful.
- Blood clots - this is a relatively common complication of extremity surgery. Blood clots can form in the large veins of the leg and cause pain, swelling and extend or break off and travel to the lung (pulmonary embolus). The risk is minimized as much as possible with a combination of early activity, mechanical compression devices and blood thinning medications.
- Infection - total knee replacement infection is rare. The incidence is minimized by antibiotics given before and after surgery. Careful handling of the soft tissues and operating room techniques are also important factors in preventing this problem. Infections can be treated with irrigation and debridement (washout of the knee joint), removal with immediate reinsertion of a new replacement or delayed reinsertion (approximate 6 weeks) along with intravenous antibiotics. Certain medical problems can place patients at higher risk of getting an infection and fighting infection.
- Injury to blood vessel or nerve - TKR is a major surgical procedure. There are blood vessels and nerves that are at risk in the back of the knee. Care is taken to protect these structures during the surgery.
- Blood transfusion - blood counts are checked before surgery and monitored afterwards. Starting (preoperative) blood count, surgical blood loss, extensiveness of the surgery and underlying medical problems determine the need for blood transfusion. It is less likely following knee replacement surgery but it may be necessary. Patients can predonate their own blood, so that it would be available if necessary.
- Persistent pain - despite the fact that TKR is a very successful surgical procedure, there are situations where patients can have persistent pain after surgery. Workup of this problem can include blood tests, and other special studies to determine the source.
Total knee arthroplasty is a very successful surgery. However, the replacement has limitations. The polyethylene is the weak link. Failure of the knee replacement can occur from loosening, wearing out of the polyethylene, osteolysis and/or component breakage. Loosening can occur as an isolated problem from relative motion between component and the bone.
Osteolysis which is a resortion of the bone around the component can result in particles produced as the polyethylene wears out. There have been extensive studies done to produce specialized polyethylene that can resist wear as well as other component modifications to influence the amount of wear particles produced by the knee replacement. However, this problem still exists.
Revision Total Knee Replacement
When the total knee arthroplasty fails, treatment is usually surgical. The extensiveness of this surgical procedure depends on the reason for failure. Polyethylene exchanges are relatively less involved procedures that patients can expect recovery quicker. Full revision surgery for all components can be very extensive and challenging. Bone integrity plays a significant role in determining the plan for this surgery.
More specialized and larger components tend to be needed due to the bone loss. Bone grafting or metal augments may be necessary. Rehabilitation can also be more challenging for the patient. However, the results can be very satisfying with significant pain relief.
Open and download our Total Knee Replacement Booklet
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