Hip and knee joint replacement surgeries are one of the most successful surgeries in the history of modern medicine. The surgeries relieve the pain and disability caused by arthritis not amicable by conservative management options. But like all surgeries, there is are risks of a number of complications after any hip or knee joint replacement surgery. The infection of the artificial joint is one of the dreaded complications of joint replacement.
The risk of infection after joint replacement surgery is roughly about 1% (1 in 100). The chances of infection are significantly higher in the case of revision surgery. The infection may develop in the tissues around the artificial joint or over the wound.
The infection may occur immediately in the hospital or after the patient goes home. Joint replacement infections may also develop years after the procedure.
Active infection at the time of surgery is a significant risk factor for the development of artificial joint infection. The active infection may be present in the blood known as septicemia. The patient may also have an active infection in the local tissues such as skin, subcutaneous tissue, or deeper tissues. A history of prior local surgery or local infection increases the risk of infection.
Patients on immunosuppressant medications have an increased risk of prosthetic joint infection. Immunosuppressant medications decrease the body’s ability to fight back infections. This may lead to common microorganisms causing infection of the artificial joint.
Immunosuppressant drugs include chemotherapy drugs, corticosteroids, and disease-modifying drugs such as methotrexate. These drugs are often used in transplant recipients and cancer treatment.
Certain medical conditions decrease the body’s ability to fight infections. The diseases include uncontrolled diabetes mellitus, chronic kidney disease, liver failure, malnutrition, and HIV infection with low CD4 counts. Affected patients are at a higher risk of infection after joint replacement surgery.
Inflammatory medical conditions such as rheumatoid arthritis, psoriasis, and ankylosing spondylitis also increase the chances of prosthetic joint infection. Patients with a history of alcohol intake, smoking, iv drug abuse, and poor dental hygiene are at a greater risk of infection.
The bacteria residing normally in the skin is the most common cause of artificial joint infection. The microorganism may make it’s way to the joint through a sinus tract to the joint capsule. The dehiscence/giving away of the surgical wound may expose the deeper tissues to the external environment.
At times the microorganisms may infect the joint during the surgery. Strict precautions are taken to prevent intraoperative joint space infection. The infection may also occur by micro-organisms traveling through the blood. The organisms may get in the blood through infection anywhere in the body, dental procedures, ulcers, wound complications, etc.
Multiple local surgeries or a history of invasive procedures such as colonoscopy increase the chance of blood bacteremia.
Time of Infection
Acute or immediate infections occur within less than 90 days after the surgery. Commonly they occur within the first 3-6 weeks after the surgery. The infection is generally confined to the joint space only. The interface of the artificial component and the bone is usually not involved.
The infection occurring after 90 days is usually defined as a chronic infection. The infection may occur even years after the procedure. There is often a biofilm development. The development of biofilm also does not happen in the first 4 weeks.
The biofilm is produced by the infecting micro-organism. The biofilm acts as a barrier for the body’s defense mechanisms against infection.
The most common symptoms of prosthetic joint infection are persistent pain and stiffness of the involved joint. In acute infections, there may be additional symptoms of swelling, drainage of the joint, and joint tenderness. The symptoms may include low-grade fever and malaise.
Chronic infections may have very subtle presentations. The common symptoms are worsening of pain over a period of time. The patient may also experience progressive deterioration of the function of the involved joint.
The diagnosis of joint replacement infection involves a myriad of investigations involving radiological, blood, and joint aspirations. A complete assessment of the patient joint and health conditions is made by the consulting orthopedic surgeon.
The management of prosthetic joint infections is mostly surgical. The type of surgical management depends on multiple factors. Factors such as patient’s health, time since the joint replacement, and the severity of the infection may dictate the management.
The above images show a modular tibial component that may be used in a revision knee replacement for an infected primary knee replacement. The modular component allows attachment of a stem and bone augments. The stem ensures rigid fixation and distribution of forces acting on the tibial base plate. The metaphyseal cone shown in the image has a coating mimicking the trabecular bone that allows biological fixation. Metal bone augments may be used to fill in the bone gaps encountered intraoperatively.