Infection In Implants And Devices

Definition

An implant-associated infection is defined as the host response to one or more microbial pathogens on/in an indwelling implant or device.

Background

The use of surgically implanted devices has markedly increased in the past 2 decades because their use has significantly improved the quality of life for many of the recipients. Advances in implant design, improvement in surgical technique and perioperative prophylaxis have made implant surgery a runaway success. Implant surgery is typically associated with improvement /restoration of function and nowadays, the implants are comfortable, functional and cosmetically acceptable.

However, implant surgery can be associated with a variety of complications, the most dreaded being infection on or around the device/implant. Development of device-related infections begins with colonization of the foreign material by micro-organisms, followed by biofilm formation. In this surface-associated form, the micro-organisms (especially bacteria) becomes altered. In conjunction with the physical protective layer provided by the biofilm, they often render antimicrobial therapy ineffective when used alone. Because the microorganisms are able to reside on the hardware, they proliferate and cause local damage, such as loosening of implanted devices, wound dehiscence, or disruption of the implant (e.g.prosthetic heart valves), as well as systemic manifestations, such as fever or embolic phenomenon.

This overview focuses on infections related to various neurosurgical, cardiac, and orthopaedic devices.

Clinical

The onset and clinical manifestations of device-related infections vary with the pathogen involved, as well as the component of the device which is affected.

Pain, redness and swelling over the device or implant is often the first complaint if the implant and device is situated near the skin surface. Systemic symptoms like fever, myalgia may ensue. The function of implant and device will gradually become impaired e.g. infected knee or hip implants will cause pain and instability on walking. In infected prosthetic heart valves, the patient may feel increasingly tired and have poor effort tolerance or even heart failure.

Diagnosis

These infections often represent a diagnostic challenge. In addition, there may be lack of a consensus definition of what constitutes an infection and its severity. There is a paucity of well-designed, large studies addressing optimal methods of investigation and management.

Good and reliable diagnostic microbiologic specimens are paramount in tailoring the antimicrobial therapy.

Treatment 

Management of patients with implant infections is complex. Antibiotics usually have to be given for a prolonged period of time (4-8 weeks) depending on the depth and extent of infection. Frequently, patients are managed with hospitalization, prolonged courses of antibiotics, and surgical interventions, all of which can negatively impact on the patients’ quality of life. There is also the problem of increased medical costs as a result of device and implant infections. In selected patients, outpatient intravenous antibiotic therapy may be used to reduce the period of hospitalization.

Surgical removal of the device may be necessary. In some limited types of device-related infections, radical salvage therapy may be warranted. In addition, certain patients are not candidates for, or may not want any further surgical interventions. In such cases, long term suppressive antimicrobial therapy may be required.

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