Knee joint replacement surgery has become a mainstay in the treatment of advanced degenerative arthritis. Because of the painful and debilitating nature of arthritis, more and more people are benefiting from total knee replacement. About 300,000 people undergo total knee replacements each year in the United States, the University of Connecticut Health Center says. The procedure doesn't come without its own set of risks and potential complications, however--some of which can be catastrophic. Prospective patients should be aware of potential problems that could arise.
Infection
Infection is one of the most, if not the most, catastrophic complications of joint replacement of any kind. Of all joints replaced in the United States, the knee is the most frequently replaced. According to the University of Connecticut Health Center, the chance of serious, deep infection in post total knee replacement patients is less than 2 percent. This is a relatively low percentage, thanks to improvements in sterile techniques, air flow in the operating rooms and better use of prophylactic, or preventative, antibiotics. When infection does occur in a knee joint replacement, the microorganisms begin to grow rapidly in numbers, multiplying exponentially. Because the implants are artificial, they possess no blood supply to allow for antibiotic penetration. The implants, and bone cement if used, provide barriers to the antibiotics' effectiveness, thus rendering the medications all but useless.
In cases of severe infection, the most appropriate treatment is the complete removal of all the implanted parts. This is usually followed by placement of antibiotic-impregnated molds made of bone cement. These act as temporary spacers, shaped like the original implants, and allow for slow, sustained release of antibiotics into the joint. They also provide the knee compartment with proper support and reasonable function until it is safe to reimplant new parts.
Blood Clots
Knee joint replacements carry a risk of developing blood clots in the lower portions of the legs, known as deep vein thrombosis. These blood clots have several causes, including tourniquet ischemia during surgery or stoppage of blood flow to the leg by using a pneumatic inflatable constricting device called a tourniquet; relaxation of the large vessels in the lower portion of the body secondary to anesthesia; and postoperative immobility. Once formed, these clots carry with them the potential for dislodging from the vessels in the legs and traveling into the heart and lungs, creating a condition known as pulmonary embolism, which can be serious and, on rare occasions, fatal.
Implant Loosening
One complication that typically occurs weeks to months after surgery is loosening of the prosthetic implants. This occurs for a variety of reasons, including improper insertion of the implants during surgery and improper balancing of ligaments and soft tissues, which can lead to abnormal forces being exerted on the implants. Obesity and postoperative trauma, as seen in falls, can also loosen implants. Loosening can be the result of infection or due to substandard quality of the host bone. Examples of poor bone quality can be found in patients with rheumatoid arthritis and osteoporosis. Implants sometimes also loosen for no apparent reason.
Implants can loosen years after surgery. This typically happens after microscopic plastic particles wear off the spacer of the tibia or shin bone. These microparticles of plastic work their way between the bone and the cement, or the bone and the implant, creating a scenario of bone resorption or dissolution.
Implant Breakage
Knee joint replacements use prosthetic implants that are typically made of high-tech metal and plastic. In severely obese patients, as well as in patients where implantation techniques are substandard, breakage of the plastic spacer, or articular surface, can occur. Plastic tibial articular components can also break if a person falls directly onto the knee. In any case, the broken plastic tibial component must be removed and replaced.
Loss of Motion
Joint stiffness can be an aggravating complication of knee replacement surgery. It can occur in the early rehabilitation phase or months after surgery. The technical term for this type of stiffening is arthrofibrosis: "arthro" meaning joint, and "fibrosis" meaning formation of fibrous scar. Because knee replacement surgery is a major procedure, a fair amount of postoperative inflammation is expected. This inflammation is typically treated with pain medication, cold therapy and physical therapy modalities designed to reduce inflamed tissues and promote better movement.
References
- University of Connecticut Health Center: Total Joint Replacement Conditions and Treatments
- The American Academy of Orthopedic Surgeons: Total Knee Replacement
- Georgetown University Hospital: Complications After Total Hip and Knee Replacement
- eOrthopod.com: Stiff Knee after Knee Replacement; What's the Best Treatment Approach?
- PubMed.gov: Therapy of Arthrofibrosis After Total Knee Arthroplasty
