2024-01-11 07:00:46
Infection of a prosthetic joint is a relatively common situation that can damage the joint. Find out more…
Last update : January 11, 2024
Prosthetic joint infection is a relatively common complication following joint replacements. The installation of prostheses is a very widespread surgery today, which makes it possible to treat numerous pathologies linked to the bone system.
Most cases involve hip or knee replacements. Although these are interventions with very good results, they can cause complications, like any other surgical technique. Why does this infection occur? What are the symptoms? etc.
What is prosthetic joint infection?
Infection of the prosthetic joint is also known as “periprosthetic infection.” This is a complication that compromises both the joint replacement area and adjacent tissues.
Arthroplasty is the medical name for this procedure. According to information from the University of Navarra Clinic, around 30,000 interventions of this type are carried out in Spain each year. It is a safe intervention that, in most cases, produces a notable improvement in the patient’s quality of life. The joints most likely to be replaced with a prosthesis are the hip and knee.
However, as stated in a publication in Clinical Microbiology Reviews, a minority of patients will experience device failure and require additional surgery at some point in their lives. It is estimated that between 2 and 4% of joint replacement cases end in infection.
The big problem is that it can lead to other serious complications. In addition to causing a high cost for the health system. It is usually derived from the patient’s own bacteriawhich form a gelatinous matrix on the prosthesis.
Indeed, micro-organisms adhere to the surface of the prosthesis. Once there, they multiply and give rise to this matrix, called biofilm. It is a mechanism that defends them from the action of antibiotics, making them more resistant to treatments.
What causes a prosthetic joint infection?
Prosthetic joint infection can be caused by different types of bacteria. As we have pointed out, these adhere to the prosthesis and form a biofilm. To do this, they are organized in layers, one above the other. This explains why those found in deeper layers are more resistant to antibiotics.
However, the prosthesis itself also impairs the function of certain cells of the immune system, such as phagocytes. All these factors favor the progression of the infection and its complexity to treat.
The bacteria generally involved are staphylococci. Within this group, the most common microorganisms are Staphylococcus aureus et Staphylococcus epidermidis. The other agents involved are:
Escherichia coli.
Pseudomonas aeruginosa.
Enterococcus spp.
It may also be a polymicrobial infection. That is to say caused by more than one bacteria. Fungal infections are less common.
Also read: New hip prostheses are created to combat arthritis and pain
What are the types of infection?
Infection of prosthetic joints is generally classified according to the time of evolution. Some authors distinguish between acute and chronic infection. However, as the Prioam Guide explains, it can also be classified as follows:
Early post-surgical infection (PPI). Late chronic infection (CLI). Acute hematogenous (AHA).
Those who distinguish only between acute and chronic infection include acute hematogenous infection in the first group.
Early post-surgical infection or acute infection
Early post-surgical infection is that which occurs in the first month following fitting the prosthesis. Some consider it still considered an acute infection up to three months following surgery.
Several criteria make it possible to identify this type of prosthetic joint infection. There is usually dehiscence and suppuration of the surgical wound. Additionally, when fluid is removed from the joint and examined in the laboratory, the presence of bacteria is often detected.
In such cases, It is important to make early diagnosis and treatment. In this way, the necessity of having to change the prosthesis due to infection can be avoided.
Acute hematogenous infection
Acute hematogenous infection is one that occurs when the focus of the infection is elsewhere in the body. That is, the bacteria may come from another process like pneumonia, urinary tract infection, endocarditis, etc. In fact, it travels with the blood and ends up colonizing the prosthesis.
Chronic prosthetic joint infection
A chronic infection is generally considered when three months have passed since the prosthesis was fitted. It is more complicated to treat than acute cases, because the bacterial biofilm has matured and cannot be eliminated.
This condition progresses gradually and insidiously. The pain lasts for months, although there are no clear signs of infection or fever. In some cases, there may be abscesses and fistulas. In these cases, replacement of the prosthesis is usually necessary.
Associated symptoms
Symptoms of prosthetic joint infection vary depending on whether they are acute or chronic. It is important to note that more or less half of the cases are chronic. For this reason, one of the predominant symptoms is inflammatory pain.
The problem is that joint replacements can cause pain without necessarily causing an infection. Therefore, it is sometimes difficult to reach a correct diagnosis. Added to the pain, there may be a lack of functionality of the joint.
In cases of acute infection, patients often present with fever. The surgical wound does not heal properly and purulent material may ooze from it. The area is often swollen, warm and red.
How is prosthetic joint infection diagnosed?
The diagnosis of this type of infection must be made early. This prevents the infection from becoming chronic and the need to repeat the operation. To be able to do this, it is important to carry out adequate monitoring of the patient and to be attentive to any warning signs.
However, there are a series of complementary tests that can help with the diagnosis. One of them is positron emission tomography. It is a technique that uses a glucose tracer. This molecule is absorbed by the bacteria caused by the infection.
So, thanks to the scanner, you can see the areas where the bacteria are located. Other useful tests include synovial fluid analysis and blood tests. Ultrasound and x-ray may also be helpful.
What treatments are available?
Infection of prosthetic joints requires multidisciplinary treatment. In all types, medical treatment is usually combined with surgery. The doctor relies on reducing pain and administering specific antibiotics to cure the infection.
Surgery can be used to clean and debride tissue. In cases where the infection is chronic, it is likely that a change of prosthesis will be necessary. This can be done in one step or in two steps.
That is to say, the new prosthesis can be placed in the same surgery. The two-step option involves removing the prosthesis, cleaning the area and placing a spacer containing antibiotics. Later, in another procedure, the new prosthesis is placed.
To establish an antibiotic treatment, it is recommended to first identify the germ in question and its sensitivity to said medications. The duration of treatment can be long. In some cases, such as knee replacements, six months of treatment may be recommended.
Remember that prosthetic joint infection can be serious
Finally, although it is not a very common complication, infection of the prosthesis is very feared by surgeons. Indeed, in some cases, this requires another intervention and replacement of the prosthesis.
It is important for patients to know the signs and symptoms in order toquickly identify an infection. Additionally, doctors should make the diagnosis as quickly as possible, as this reduces the likelihood of having to re-operate.
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