2007 Abstract : 15

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Author(s): Mir H. Ali, MD, PhD*, Todd Kowalski, Elie Berbari, MD, Douglas Osmon MD, James Steckelberg, MD, and Paul M. Huddleston, MD; Mayo Clinic, Rochester, MN

Title: Spinal Fusion Rate in Patients with Early-Onset Spine Implant Associated Infections

Purpose: Spinal instrumentation is an established method of achieving spinal fusion. Early-onset infection and its subsequent effects on arthrodesis and outcomes are unclear. The goal of this study was to determine the clinical outcome of early infection.

Methods: We identified all patients with instrumented spinal fusions performed between 1994 and 2002. Twenty nine patients developed early-onset spinal implant associated infection. The medical records, imaging, laboratory results, microbiology, and pathology were reviewed. The cumulative probability of spinal fusion was assessed by using the Kaplan- Meier survival method. The Log Rank test for equality of survival was used to compare the outcome.

Results: 29 patients were treated with surgical debridement, implant retention, and antimicrobial therapy.Patients averaged 2.2 ?? 1.3 surgical debridements, 33 ?? 12 days of intravenous antibiotics, and 353 ?? 29 days of oral suppressive therapy. 72% (21/29) of patients demonstrated successful treatment from this regimen; 28% (8/29) of patients required additional surgical debridement and/or modification of antimicrobial therapy. The one and two-year estimate of spinal fusion for the 29 patients was 35% (95% CI: 20% - 54%) and 96% (95% CI: 87%-99%) respectively. Despite successful arthrodesis at 2 years, 44% of patients were significantly disabled by paraspinal pain and 41% continued to require opiates. Among the variables that affected fusion rate, patients with prior spinal radiation therapy had a delayed fusion rate. Patients with prior spinal radiation therapy were significantly more likely to develop a delayed fusion compared with those who had no radiation therapy: 41% (95% CI: 24%-63% vs. 17% ( 95% CI : 4%-54%; p=.02). Variables that did not affect fusion rate were: smoking, diabetes mellitus, end stage renal disease, and a history of prior spine surgery.

Discussion: Early-onset spinal implant associated infections are associated with a high morbidity and best treated with early debridement, implant retention, and antibiotic therapy. Wound healing and inflammatory laboratory values should be followed closely to monitor treatment success. Time to arthrodesis is significantly prolonged in patients with prior spinal radiation.