How is an Infected Hip Prosthesis treated?

• Infections in hip prostheses have an incidence of 1% to 3%.
• Pain and reduced mobility will be taken into account when deciding on treatment for hip prosthesis infection.
• Treatment for hip prosthesis infection will involve either preservation of the prosthesis or, conversely, replacement of the prosthesis.

Infected hip prostheses have an incidence of between 1% and 3%, with a higher percentage in revision (non-primary) hip prostheses.

The choice of whether to keep the prosthesis or replace it with a new one varies depending on the patient's characteristics and which option is the best in terms of: less surgical aggression, sensitivity to antibiotic treatment and fewer side effects.

Normally, the option with the best results is the total reimplantation of the hip prosthesis, after eliminating the infection. This intervention can be done in one or two stages, so it is very important to know the patient's history in order to decide on the best treatment.

The goal of treatment (surgical or non-surgical) for hip replacement infection is to cure the infection, eliminate the pain caused by the infection and restore joint function with minimal sequelae.

The reason why a hip prosthesis becomes infected is the presence of bacteria. People live with these microorganisms on a daily basis, as they are part of the environment: they are on our skin, on our clothes, on everyday objects and, therefore, on surgical material, and it is in the operating theatre where infections originate most of the time.

The probability of a hip prosthesis becoming infected is 1% - 3%

However, the fact that a prosthesis becomes infected does not mean that the surgical room has not been properly disinfected or that the specialist has performed malpractice. It is important to know that bacteria not only fight for their natural space, but are also capable of multiplying on foreign surfaces, such as prostheses.

The material they are made of is inert and is not irrigated by our blood, so our defences cannot act properly. In fact, when antibiotic treatment is used to treat the infection, in many cases it is not enough because the doses do not arrive in the correct way.

Therefore, depending on the time at which the infection of the prosthesis occurs, with respect to the time of the hip surgery, we can distinguish three types:

• Acute infection: appears within the first 3 weeks and its cause is usually bacterial.
• Subacute infection: can appear between 6 and 24 months after hip arthroplasty.
• Late infection: it appears after years, due to procedures other than hip arthroplasty (dental surgery, colonoscopy, etc.). Patients who suffer from it present with inflammatory symptoms typical of bacterial infection.

Although the probability of a hip prosthesis becoming infected is very low, it is important to know that it can happen and that, depending on the type of infection, the specialist will indicate one or another treatment.

When the infection of the hip prosthesis is acute, i.e. less than 3 - 4 weeks old, the specialist may recommend healing, trying to preserve the implant.

However, in most cases it will be necessary to perform the appropriate surgical debridement. So, here are the different options for preserving the infected hip prosthesis, without the need to replace the implant.

Suppressive treatment

When a specialist speaks of suppressive treatment for an infected hip replacement, he or she is referring to antibiotic treatment. The aim is to reduce the symptoms associated with the infection of the hip prosthesis and to preserve joint function.

This technique is indicated in patients with a short life expectancy, given the high surgical risk. In addition, it will be necessary for the patient to show no systemic infection and still maintain implant stability. Otherwise, this treatment may be discouraged, and surgical removal of the hip prosthesis may be necessary.

As this is an oral antibiotic treatment, it is important that the patient is tolerant and committed to the doses.

However, this treatment is not always recommended, as bacteria tend to be highly resistant to antibiotics. Nevertheless, suppressive treatment with medication allows prolonged control of the infection and maintenance of joint function.

Debridement with retention of the prosthesis

This treatment consists of thorough debridement of the infected tissue surrounding the joint and replacement of the moving parts of the implant (polyethylene and femoral head). The remaining components are left in place and the patient is treated with antibiotics.

Debridement can eradicate the infection and preserve joint function of the prosthesis.

This treatment is less aggressive than removal of the prosthesis, but it is true that certain requirements must be met for the specialist to indicate debridement with retention:

• Implant with stability and good joint function
• Acute infection, detected before 3 weeks after hip arthroplasty
• The bacterium or micro-organism responsible for the infection must be sensitive to the combination of antibiotics indicated by the specialist.
• Good immune system
• Absence of fistula, osteitis or severe soft tissue involvement.

In cases where the requirements for this type of hip infection treatment are not met, the implant will be removed and replaced.

The removal and replacement of an infected hip prosthesis is a procedure that requires the expertise of a specialist in Orthopaedics. It requires greater hospital resources than primary and revision prostheses.

The removal and replacement of the prosthesis can be divided into one or two stages. The best option is the one with the least surgical aggression. However, it is not always possible to perform the procedure in a single intervention.

Replacement of a hip prosthesis in a single intervention

One-time removal and replacement of the hip prosthesis involves the complete removal of the implanted elements in a single operation. This method has a number of advantages over the two-stage method (two interventions). Not only is the recovery time shorter, but the cost is also much lower.

The effectiveness rate of removal and replacement of the infected hip prosthesis over time is 80-90 %.

Although the medical indications are not clear, specialists agree that the patient who undergoes this procedure must meet the following requirements:

• Infection less than two weeks old
• Soft tissues in good condition
• Bacteria causing infection, susceptible to antibiotic treatment
• Good and stable health status

The replacement of an infected prosthesis in one time (in one single intervention), consists of:

• Thorough cleaning of the tissue (debridement).
• Fitting a new prosthesis

In such cases, it is important to know the bacteria that caused the infection and its sensitivity to antibiotics in order to be able to use a cementation with a specific antibiotic.

Replacement of a two-stage hip prosthesis

Two-stage hip replacement is the treatment of choice in cases of chronic or late hip prosthesis infection. It is also performed in cases of fungal infection, highly virulent bacteria, polymicrobial infections, underlying inflammatory diseases, immunocompromised patients or reinfection after reimplantation.

The conditions for a patient to undergo a two-stage (two operations) operation for an infected hip prosthesis are:

• Systemic manifestation of infection
• Infection without detection of the causative bacteria
• Positive tests for microorganisms resistant to antibiotic treatment
• Presence of a fistula

Thus, the two-stage replacement of an infected prosthesis consists of:

• Cleaning, debridement and resection of the devitalised tissues.
• Removal of the infected prosthesis, together with the cement, but preserving the bone.
• Placement of a cement spacer with antibiotics.
• Administration of the appropriate antibiotic, as indicated by intraoperative samples.

Although there is no evidence to define the interval between one time and the next, it usually takes 2-4 months before the infectious condition is considered cured. After this period, the following procedure is performed:

• Re-implantation of a new hip prosthesis.

The healing rate with the two-stage technique is 90 % - 97 %.

Rehabilitation is the same whether the prosthesis is replaced in one or two stages, but always taking into account the characteristics of each patient.

Normally, postoperative check-ups are carried out at 3, 6 and 9 weeks. Then at 3 and 6 months and, finally, they are done every year.

If you have a diagnosed case of hip prosthesis infection and you want to know the surgical assessment of the Specialist, Operarme offers you a first consultation free of charge.