What is a prosthetic infection?
Infection of a prosthesis is one of the worst complications that a patient who has undergone arthroplasty can suffer. The patient, who has undergone surgery with the aim of improving pain and function in his damaged joint, ends up in a much worse situation than before the operation, with the logical frustration that this entails. Prosthetic infection involves the invasion of the surface of prosthetic implants by pathogenic microorganisms, usually bacteria.
Why do prosthetic infections occur?
This is a type of infection based on the ability of certain bacteria to adhere to the surface of the prosthesis, multiply and form a structure called a biofilm. Infection occurs after the arrival of pathogens (bacteria) to the implant and this takes place, in most cases, during the surgical procedure; less frequently it occurs through the bloodstream from remote foci of infection (hematogenous prosthetic infection). Prosthesis infection is never due to “prosthesis rejection”, as we often hear our patients say, nor is it caused by an “operating room virus”, since in 99% of the cases, the infection is bacterial. The existence of such a biofilm is responsible for prosthetic infection being a difficult entity to diagnose and treat.
Is it frequent?
The risk of infection after implantation of a first joint prosthesis, in healthy patients, has been established at around 1-3%. This can be much higher (more than 15-20%) in patients with certain underlying diseases (diabetes, rheumatoid arthritis, previous infections, etc.) or in patients undergoing prosthesis replacement. Infection is considered to be the leading cause of knee prosthesis failure (25% of knee prosthesis failures are due to infection) and the third leading cause of hip prosthesis failure (15% of hip prosthesis failures are due to infection). In other joints, such as the shoulder or ankle, the figures can be much higher.
What symptoms alert the patient to these infections?
In cases of chronic prosthetic infection, pain is the main symptom manifested by the patient. Often the patient does not understand that his prosthesis is infected, since he has “never had a fever” and has not experienced other signs that we normally associate with infection. The absence of typical signs and symptoms of infection is a characteristic of prosthetic infection. Outflow of purulent material is rare, but is definitive of chronic prosthetic infection. Lack of mobility or early loosening of the prosthesis are also classic signs associated with infection. But as we say, pain is the main symptom and the existence of an infection should always be ruled out in any patient with a painful prosthesis.
What should the patient with prosthesis infection do?
The diagnosis and treatment of prosthetic infections is complex and should only be undertaken by experts in the field. The objective is, of course, to achieve the best results in the shortest possible time, avoiding subjecting patients to unnecessary diagnostic tests and multiple surgical interventions. Let us not forget that in complex cases of prosthetic infection, the limb and/or the patient’s life may be at risk. Treatment of infection is always surgical; only surgery can eradicate a prosthetic infection. In most cases surgical removal of the infected prosthetic components will be necessary. Obviously, after removal of the infected prosthesis, implantation of a new, infection-free prosthesis is mandatory to achieve proper function and pain relief. This can be done with a one-stage prosthetic replacement protocol (removal of the infected implant and placement of a new implant during the same surgery) or with a two-stage prosthetic replacement (the patient is temporarily implanted with a spacer containing antibiotics until the infection is controlled and a new prosthesis can be safely implanted). Both procedures are effective if indicated in the right patient. A detailed assessment, case by case, is essential to be able to offer each patient the best solution for his or her particular case. In expert hands, a definitive cure of the prosthetic infection is achieved in more than 85% of patients.
Example cases:
- Osteomyelitis: 32-year-old patient with chronic osteomyelitis of the tibia (type IIIBlocal) after an open fracture 8 years ago. The patient had undergone surgery 7 times without healing. We achieved eradication of the infection after removal of all the infected-necrotic bone by saucerization and drilling; the dead space was obliterated with a bone substitute with antibiotics. To achieve healing, reconstruction of the skin defect is mandatory, which is performed with a microsurgical anterolateral fasciocutaneous anterolateral thigh (ALT) microsurgical free flap.
- Prosthetic infection, one-time replacement: 87-year-old patient with a chronic prosthetic infection in his right hip prosthesis due to a sensitive Staphylococcus aureus. In the image on the left we can see the productive fistula that the patient presented and that is definitive of chronic infection. Despite his advanced age, the patient was considered a candidate for surgery in time. In the surgical image, the implantation of the new prosthesis and the use of local antibiotic beads. After 2 years the patient continues to be free of infection and with very good joint function.
- Prosthetic infection, two-stage replacement: 77-year-old patient with a chronic infection by multidrug-resistant Staphylococcus epidermidis after replacement of a right knee prosthesis. In this case we chose to perform a two-stage prosthetic revision. In the surgical image (1st time), we observe the bad aspect of the tissues after the removal of the implants and the final result after debridement. Subsequently, an articulated cement spacer with antibiotic is temporarily implanted. Once the infection is considered to be eradicated, the patient is operated again (2nd time) to implant the definitive prosthesis. In the X-ray the good result after 4 years of surgery with no signs of recurrence of infection.
For more information contact a specialist.