Recently presented research on the Medicare population shows infection
rates between 9% and 12% after primary and revision
instrumented lumbar fusion at up to 10 years and associates
patient comorbidity with an increased
risk for infection.
Using Kaplan-Meier survival and Cox regression analyses to calculate the
rate and risk factors of infection for 15,069 primary and 605 revision
instrumented lumbar fusion cases, Steven M. Kurtz, PhD, and colleagues found
that age, obesity, Charlson index, low socioeconomic status, census region, and
primary and revision region were significantly associated with infection at up
to 10 years follow-up.
Other factors that increased infection risk included the number of
operated segments, surgical approach and the year of index procedure. They
found no significant correlations between infection and other potential risk
factors such as gender, race, smoking history and diabetes.
Our study shows that preoperative and patient-related risk factors
are strong predictors for infection, but clinical factors such as number of
levels and the approach can also play a role in infection risk, Kurtz,
who presented the findings at the
2011 Annual Meeting of the North American Spine Society, said.
Kurtz and colleagues used Medicare 5% administrative data for inpatient,
outpatient and physician carrier claims using procedure codes ICD-9-CM and
CPT-4 to identify patients who underwent lumbar fusion using cages or posterior
instrumentation, according to their abstract. Patients were followed for 12
months prior to surgery to identify any comorbidities present in their medical
At 2-year follow-up, primary procedures had a 6.5% infection risk. At
10-year follow-up, the risk increased to 8.5%. For revision procedures, the
infection risk increased from 9.8% at 2-year follow-up to 12.2% at 10-year
In general, infection risk was higher with revision surgery, with a 1.66
odds ratio for lumbar fusion revision. For surgeries in which nine fused
vertebrae or greater were present, the ratio was 2.39 compared to surgeries
with two to three fused vertebrae. A higher Charlson index was associated with
greater infection risk, with a ratio of 2.48.
Standalone anterior lumbar interbody fusion compared to
posterior lumbar fusion had a ratio of 1.36, while cage-only posterior lumbar
interbody fusion/transforaminal lumbar interbody fusion vs. posterior lumbar
fusion had a 0.73 ratio, Kurtz said during his presentation.
Infection is still one of the largest unsolved problems that we
have to deal with and more effort needs to be expended towards finding out ways
to prevent infection, he said. by Jeff Craven
- Kurtz S, Lau E, Ong K, et al. Infection risk for primary and
revision instrumented lumbar spine fusion in the Medicare population. Presented
at the 2011 Annual Meeting of the North American Spine Society. Nov. 2-5.
- Steven M. Kurtz, PhD, can be reached at Exponent Inc., 3401 Market
St., Suite 300, Philadelphia, PA 19104; 215-594-8851; email:
- Disclosure: No funding was received in support of this
study. Exponent receives institutional support from Medtronic Inc.