How does a prosthetic joint infection become infected?
When a patient has an operation, they become more at risk of bacterial infection. Bacteria often form in areas where the skin is broken, and a patient is particularly at risk during a prosthetic joint operation, such as hip or knee replacement surgery. On such internal prosthetic joints, blood or antibiotics cannot reach the area in the same concentration as in the natural tissues of the body, and specialised bacteria can then settle and develop an infection.
What types of infections can occur in a prosthetic joint, and what symptoms are present?
There are aggressive and less aggressive types of bacteria. Infections are classified depending mainly on the relation between the time the infection occurs and the time the prosthesis is implanted. They can be classified as:
- Acute infections: those that occur in the first month after implantation.
- Subacute infections: which are those that occur between the first month and the first year.
- Late infections or haematogenous: which are when a prosthesis that has been working perfectly for years, develops an infection when the patient has pneumonia, or a surgical procedure in the colon or bladder, which causes bacteria to disseminate, reach and infect the prosthesis.
How is it diagnosed?
The diagnosis is complex since there is no simple and unique test with which to identify the infection.
Usually, it is a set of clinical signs and symptoms that need to be interpreted through laboratory tests, analysis, imaging tests such as a resonance or an X-ray or nuclear scintigraphy – and most particularly examination of cultures.
To confirm the diagnosis of infection, it is necessary to integrate all these tests since the specialised bacteria that cause infections seem to be dead or appear to be in a stationary or larval phase.
What are the treatments for prosthetic joint infections?
Treatment for an infected prosthesis depends on several factors:
- The type of microorganism that causes it - if it is very aggressive or not.
- The condition of the patient - if the patient is debilitated by diseases or not, in which case it is not necessary to operate but to prescribe antibiotics.
- The time elapsed since the implantation of the prosthesis and the infection.
- Whether the prosthesis is fixed or not.
On most occasions, it is necessary to remove the prosthesis because specialised bacteria create shields or barriers on the prosthesis and antibiotics do not reach them. It would be necessary to give antibiotics in doses so high, they would be toxic to the patient.
The prosthesis is removed and after a cycle of antibiotics administered either intravenously or orally, and when it is considered that the infection has been eliminated, a new prosthesis can be implanted so that the patient gets back their quality of life and the full function of the joint.