Prosthesis Infection: Periprosthetic Infection of the Joint Prosthesis

The technique of implanting artificial joints (endoprostheses) has steadily improved over the past few decades. The implantation of artificial joints, such as

• the hip,
• the shoulder, or
• the knee

is now considered a routine procedure, particularly at specialized clinics. The rapid increase in joint replacement surgeries in recent years can be attributed to improved techniques. However, the general aging of the population and the desire to remain mobile well into old age are also leading to an ever-increasing number of endoprosthesis implantations. 

Despite modern technology, infections can still occur in the area of endoprostheses. Such an infection of the affected bones and joints, including the surrounding tissue, continues to pose a challenge. Depending on its course, it may be an acute infection or a chronic periprosthetic infection, each presenting with different clinical manifestations.

Infection of the prosthesis typically occurs during surgery or during the wound healing process. Depending on the location, the infection rate ranges from 0.5 to 2 percent.

A prosthetic infection is associated with a significant reduction in quality of life for those affected. It requires long, costly hospital stays and various treatment efforts.

An acute prosthetic infection is characterized by a pronounced feeling of illness. Those affected feel tired and exhausted and suffer from fever and chills. In the area of the prosthesis, there is

• redness,
• pain,
• swelling, and/or
• excessive warmth.

Various signs of inflammation can be detected in the blood. Laboratory parameters such as CRP and imaging techniques such as X-rays are typically used to assess the situation and indicate a possible infection. Medical professionals refer to this as sepsis (also known as blood poisoning): This is a serious systemic infection affecting the entire body.

A gradual onset is one of the most important characteristics of a chronic prosthetic infection. Often, the relevant symptoms do not manifest until some time has passed, making early detection difficult. Pain in the affected joint and increasing loosening of the prosthesis are the most important indicators.

Bacteria are usually responsible for infections that occur during surgery or the wound-healing phase. These are often caused by a known pathogen such as staphylococci, which can be detected through microbiological testing. Due to poor hygiene or the absence of other essential protective and preventive measures, these pathogens can enter the wound site.

Alternatively, bacteria can spread via the bloodstream from sites of inflammation in other parts of the body. Possible triggers here include, for example,

• skin infections,
• urinary tract infections, and
• lung infections.

To accurately classify a given prosthetic infection, physicians use three categories. The classification of a prosthetic infection into one of these categories depends on the timing of its onset.

• First category: The infection occurs within three months of the procedure. Bacteria (Staphylococcus aureus and Gram-negative bacteria) are usually the cause. They enter the body during surgery.
• Second category: Delayed manifestation of an infection acquired during surgery, primarily caused by coagulase-negative staphylococci. The inflammation becomes apparent approximately three to 24 months after surgery.
• Third category: Infections that do not lead to the first signs of illness until about two years later. The cause is usually hematogenous spread, i.e., infections in other parts of the body. Here, too, staphylococci are the predominant causative agents. One exception is urinary tract infections caused by Escherichia coli bacteria, among others.

If you are experiencing one or more of the symptoms described above, you should consult your doctor. If a prosthetic infection is present, only prompt treatment can prevent your condition from worsening, which could have potentially serious consequences.

During an initial consultation—known in medical terminology as a medical history—your doctor will ask you questions about your symptoms, your medical history, and more. The medical history helps provide an initial assessment of the condition. The diagnosis of an infection is then confirmed through intraoperative sampling and subsequent microbiological analysis to enable targeted treatment.

This is followed by a physical examination and radiological evaluation. Important findings are also provided by

• a blood test,
• a puncture of the affected joint,
• tissue biopsies, and
• an analysis of the prosthetic material.

To identify potential triggers as accurately as possible, the doctor often also examines the surrounding area, namely

• heart,
• lungs,
• teeth, etc.

If symptoms of inflammation are also evident here, a direct link to the prosthesis infection is likely.

Your primary care physician or the physician responsible for your joint replacement is your first point of contact for any issues with your prosthesis. In general, specialists in

• orthopedics,
• trauma surgery,
• internal medicine, and
• infectious diseases

are well-versed in this condition. If in doubt, they will refer you to experienced physicians with the appropriate specialization.

At the heart of the treatment plan is surgery aimed at replacing the prosthesis. This means that the infected prosthesis must be removed and a new one implanted.

The second component of a promising treatment for prosthetic infections is long-term antibiotic therapy. This antibiotic treatment involves the targeted administration of antibiotics, with the duration of therapy determined on an individual basis. In addition to medical treatment, supplemental surgical therapy is often necessary.

The so-called two-phase method generally promises better results. In the first step, the infected prosthesis is removed.

This is followed by a six-week course of antibiotic therapy, accompanied by joint stabilization using antibiotic-impregnated spacers.

Only then is the new prosthesis implanted. This procedure is concluded with a further course of antibiotic treatment lasting six weeks.

The risk of a prosthetic infection taking an unfavorable course is particularly high in cases of staphylococcal infections. For patients with a stable prosthesis, conservative treatments may be sufficient under certain circumstances, provided that targeted antibiotic therapy is administered.

Even in cases of septic prosthesis loosening, the prospects for a complication-free recovery are rather low. Even a minimal infection is sufficient to cause this. Treatment here also follows the “two-stage” approach described above, consisting of a combination of

• prosthesis removal,
• joint reconstruction,
• antibiotic therapy, and
• followed by implantation of a new prosthesis.

If necessary, a bone graft may also be required to compensate for the loss of bone mass caused by the loosening.

In summary, it should be noted that although prosthesis infections are rare, they must be taken very seriously due to their potentially severe consequences.

The most important preventive measures include

• strict hygiene,
• sterility,
• a healthy diet, and
• immediate medical consultation in the event of a bacterial infection, such as in the mouth or teeth.