Treatment of infected orthopedic devices

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Rheumawire

Apr 1, 2004

Treatment of infected orthopedic devices

Houston, Texas - Infections associated with orthopedic devices often

result in serious disabilities, but they are difficult to diagnose and

to manage. Some of the issues involved are outlined in a detailed review

in the April 1, 2004 issue of the New England Journal of Medicine [1].

In the review, Dr Rabih Darouiche (Baylor College of Medicine, Houston,

TX) discusses the treatment of infections associated with all kinds of

surgical implants, including orthopedic devices. In the US, infections

occur in around 2% of joint prostheses and 5% of fracture-fixation

devices, which include intramedullary nails, external-fixation pins,

plates, and screws.

Diagnosing an infection in a joint prosthesis can be difficult. Blood

cultures are negative in most cases, and even a culture of fluid from a

prosthetic joint space, obtained by percutaneous aspiration, has a

sensitivity of less than 50%. Nuclear scans can yield false-positive

results up to a few months after surgical placement of orthopedic

devices, the author notes, so computed tomography (CT) and magnetic

resonance imaging (MRI) scans are more reliable in diagnosing infection.

About two thirds of infections of surgical implants are caused by

Staphylococcus aureus or coagulase-negative staphylococci. Systemic

antibiotics are selected on the basis of the susceptibility profile,

Darouiche comments. For infected joint prostheses, options include a

quinolone (eg, ciprofloxacin) plus rifampicin, given intravenously for

at least the first 2 weeks, or a beta-lactam plus rifampicin or

trimethoprim plus sulfamethoxazole.

Most implants infected with S aureus or candida require surgical

removal, Darouiche continues. Implants infected by the less virulent

coagulase-negative staphylococci may not require removal and may respond

to prolonged antibiotic therapy, and this course of action may also be

warranted in patients who are at high risk for intraoperative or

postoperative complications.

If a decision is made to remove the infected implant, complete

extraction of all components is essential, if surgically feasible,

regardless of the type of infecting organism, he notes.

Treatment of an infected joint prosthesis can follow 1 of the following

4 routes:

Debridement plus retention of the prosthesis.

Removal of the implant without replacement.

One-stage replacement.

Two-stage replacement.

Two-stage replacement results in higher cure rates, yields better

function than 1-stage replacement, and is the preferred practice in the

US, Darouiche comments. In the first stage, the infected implant is

removed and replaced with an antimicrobial carrier (which may be

biodegradable [polylactic acid or polyglycolic acid] or nonbiodegradable

[polymethyl methacrylate]). After the patient completes a 6-week course

of systemic antibiotics, a new joint prosthesis is inserted. In patients

who have undergone multiple surgical procedures for the treatment of

infection with particularly virulent organisms, arthrodesis may be

necessary.

Infections of fracture-fixation devices that involve bone are treated

with 6 weeks of systemic antibiotics, whereas superficial infections may

need only 10 to 14 days of therapy. Further management depends on the

type of device, whether or not bone union has occurred, and the

patient's underlying condition. In certain cases, a prolonged course of

systemic antibiotics may salvage the infected fracture-fixation devices

without surgery.

However, infection of intramedullary nails is often associated with

nonunion of the bone, the author comments, and requires removal of the

infected nail, insertion of external-fixation pins, and if necessary,

subsequent insertion of a replacement nail. Infection of

external-fixation pins usually consists of a single procedure to remove

the infected pins, and if bone union has not occurred, either insertion

of new pins at a distant site or fusion of the bones.

External-fixation pins are more likely than intramedullary nails to

become infected, notes Darouiche, but the treatment of infections of

intramedullary nails is more expensive than infections with

external-fixation pins (average costs $25 000 vs $5 000).

Zosia Chustecka

Source

1. Darouiche RO. Treatment of infections associated with surgical

implants. N Eng J Med 2004; 350:1422-1429.

I'll tell you where to go!

Mayo Clinic in Rochester

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s Hopkins Medicine

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