Using Antibiotic Spacers with an Infected THA
There is very little that is more devastating to a joint replacement surgeon and his or her patient than an infected prosthesis.
That sentiment was expressed by David G. Nazarian, MD, from the University of Pennsylvania in Philadelphia, at ICJR’s Winter Hip & Knee Course, where he addressed the use of antibiotic spacers in an infected total hip arthroplasty (THA).
Although some surgeons are proponents of a 1-stage revision for infection, Dr. Nazarian prefers a 2-stage revision, which has a better success rate than a 1-stage revision in THA (91% vs. 82%, respectively).
Preformed spacers are typically used in the first stage of the revision, and Dr. Nazarian said they elute their antibitoics well. The downside is that the antibiotic dose is generally not as high as surgeons want. Fortunately, antibiotics can be added to the cement.
Dr. Nazarian and his colleagues prefer to add 2.4 to 2.8 grams of tobramycin and 1 to 4 grams of vancomycin per bag of cement. More than 4 to 8 grams will weaken the cement, and more than 8 grams renders the cement nearly unusable, Dr. Nazarian said.
With patients who have good remaining bone stock, Dr. Nazarian uses an antibiotic spacer with a metal exoskeleton and a 43 mm head. He has found an acetabular component with a 44 mm inner diameter to use with this head size.
This configuration, of course, is not as strong as a standard prosthesis, but it allows good range of motion and a lower dislocation rate. During this explant phase, the patient should be on 10% to 50% weight-bearing to protect the implant.
Following the first stage of the procedure, Dr. Nazarian prescribes intravenous antibiotics for 6 weeks, followed by oral antibiotics. He does not advocate a “drug holiday” – which he acknowledges is controversial – unless the serology is increasing and the patient needs to be off antibiotics so the site can be aspirated.
Dr. Nazarian noted that heterotopic bone growth is common and should be excised during the first stage. Following surgery, he prescribes anti-inflammatory drugs or 1 dose of radiation at 700 rads.
In a patient with more significant proximal bone loss, Dr. Nazarian uses a long stem, off-the-shelf cemented prosthesis with a 36 or 40 mm head and high-dose antibiotic cement. Because of diminished soft tissue support, this prosthesis is prone to dislocation. The patient and bone should be protected during this period.
Dr. Nazarian completes the reconstruction 3.5 to 4 months later.
Click the image above to watch Dr. Nazarian’s presentation.