Complications of knee replacement
General:
Any major surgery (not just knee replacement) carries certain risks. These are: bleeding, venous thrombo-embolism and anesthesia-related or medical-related – like disturbances of blood pressure or blood sugar, chest infection, and rarely, stroke, ischemic heart disease, etc.
Risks specific to knee replacement involve infection, injury to blood vessels or nerves, stiffness, persistent pain after surgery and early wear and aseptic loosening.
Overall, the risks of knee replacement surgery are relatively low. This is because of preoperative optimization of patient’s condition (like control of diabetes, blood pressure, etc) and strict adherence to preoperative, intra-operative and post-operative care plan. In general, operations on extremities carry lesser systemic risks and permit faster post-operative recovery as compared to abdominal or cardio-vascular surgery – as there is no surgical handling of vital organs in the abdomen or chest. In addition, general anesthesia can be avoided. The rate of major complications like infection is around 1-2 percent.
Infection:
Infection of the joint can occur immediately after surgery or at a later date. In the latter case, infection from other parts of the body spreads to the joint through the blood circulation. Poor immunity is a contributory factor. The risk of infection is higher in diabetic patients and those suffering from rheumatoid arthritis.
Preventive measures include pre-operative and post-operative antibiotics, strict discipline in operation theatre and the use of a dedicated clean operation theatre with laminar air flow facilities and body exhaust suits.
Prevention of delayed infection involves proper control of diabetes and other medical conditions. Prophylactic antibiotics & prompt treatment of infection in any part of the body (like teeth, urinary tract, etc.) is essential to prevent it from spreading to the joint.
Treatment of infected joint generally involves reoperation to wash the joint and remove any infected tissues. It may also be necessary to remove the prosthesis and implant a new one later. In severe cases arthrodesis (fusing the bones) is advised.
Venous Thrombo-Embolism (VTE):
Clotting of blood in leg veins can cause swelling and pain in the leg. Propagation and dislodgement of the clot can cause blockage of the blood flow in the lungs – this can range from a mild to a life-threatening event. This is prevented by the use of anti-coagulants (blood thinners), mechanical devices (stockings, foot pumps, etc), epidural anesthesia, proper hydration during surgery and early mobilization of the patient. Treatment of established thrombosis and embolism involves anti-coagulant medication and, very rarely, surgery.
Stiffness following surgery:
Poor recovery of movement can occur in patients who had significant pre-operative stiffness and in those who do not adhere to the physiotherapy/exercise regimen. Treatment is by physiotherapy or manipulation under anesthesia. It should be understood that most artificial joints give a good range, but not the full range, of movements. This is because of design factors and the anatomical peculiarities of each joint.
Persistent pain following surgery:
Slight discomfort at the operation site is common . It subsides within a few weeks or months. This pain is far less as compared to the pain of arthritis. Some patients experience more pain than usual. In the majority of these cases the pain is due to other problems like spondylosis, diabetic neuropathy or poor circulation in the limb. Careful evaluation reveals that the pain is not confined to the knee alone. In addition patient has tingling, numbness or burning sensation which suggests involvement of the nerves. Persistent pain could also be due to a problem in the joint itself – mechanical (like a tight knee, overhanging implant, patello-femoral clunking) or infection. A thorough assessment is required to determine and treat the cause.
Wear and Aseptic Loosening:
Over a period of time, the plastic articulations slowly wear out. The rate of wear is very low and the implant generally lasts around 15-20 years. Polyethylene wear is strictly not a complication but is an expected outcome. It is considered to be a complication when it occurs earlier. Excessive stress like obesity, high impact activities, sports, etc. will lead to early wear.
The fixation of the implant to bone can become loose as a result of mechanical forces or as a reaction to wear debris particles. It is more likely in osteoporotic bone. A variable amount of bone gets resorbed in the process. Wear and aseptic loosening are treated by revising the joint replacement.
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