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Infection risk after instrumented lumbar fusion linked to patient comorbidity
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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.
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“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 history.
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 follow-up.
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
Reference:
- 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. Chicago.
- Steven M. Kurtz, PhD, can be reached at Exponent Inc., 3401 Market St., Suite 300, Philadelphia, PA 19104; 215-594-8851; email: skurtz@exponent.com.
- Disclosure: No funding was received in support of this study. Exponent receives institutional support from Medtronic Inc.