Occult infection in pseudarthrosis revision after spinal fusion

Abstract

BACKGROUND CONTEXT: Pseudarthrosis after attempted spinal fusion is yet not sufficiently understood and presents a surgical challenge. Occult infections are sometimes observed in patients with pseudarthrosis and no inflammatory signs of infection. The prevalence of such occult infection and its association with patient demographics and inflammatory markers are largely unknown. PURPOSE: To determine the prevalence of unexpected low-grade infection in spinal pseudarthrosis revision surgery, and to evaluate whether such infection is associated with patient demographics and inflammatory markers. STUDY DESIGN: Retrospective observational study. PATIENT SAMPLE: One-hundred-and-twenty-eight patients who underwent thoracolumbar revision surgery due to presumed aseptic pseudarthrosis after spinal instrumentation. OUTCOME MEASURES: Culture-positive infections or noninfectious pseudarthrosis. METHODS: Samples were routinely taken for microbiological examination from all adults (n=152) who underwent revision surgery for presumed aseptic thoracolumbar pseudarthrosis between 2014 and 2019. A full intraoperative microbiological workup (at least three intraoperative tissue samples) was done for 128 (84%) patients, and these patients were included in further analyses. Patient characteristics, medical history, inflammatory markers, and perioperative data were compared between those with and without microbiologically-confirmed infection based on samples obtained during pseudarthrosis revision. RESULTS: The microbiological workup confirmed infection in 13 of 128 cases (10.2%). The predominant pathogen was Cutibacterium acnes (46.2%), followed by coagulase-negative staphylococci (38.5%). The presence of infection was associated with the body mass index (30.9 §4.7 kg/m 2 [infected] vs. 28.2 §5.6 kg/m 2 [controls], p=.049), surgery in the thoracolumbar region (46% vs. 18%, p=.019), and a slightly higher serum C-reactive protein level on admission (9.4 §8.0 mg/L vs. 5.7 §7.1 mg/L, p=.031). Occult infection was not associated with age, sex, prior lumbar surgeries, number of fused lumbar levels, American Society of Anesthesiologist score, Charlson Comorbidity Index, presence of diabetes mellitus, and smoking status. CONCLUSIONS: Occult infections were found in 10% of patients undergoing pseudarthrosis revision after spinal fusion, even without preoperative clinical suspicion. Occult infection was associated with higher body mass index, fusions including the thoracolumbar junction, and slightly higher C-reactive protein levels. Intraoperative microbiological samples should be routinely obtained to exclude or identify occult infection in all revision surgeries for symptomatic FDA device/drug status: Not applicable.

The Risk of Nonunion in Smokers Revisited: A Systematic Review and Meta-Analysis

“…54,55 Interestingly, recent retrospective analysis of 128 patients undergoing thoracolumbar fusion due to presumed aseptic pseudarthrosis found positive intraoperative culture rates of 10%. 56 Underlying occult infections, however, were not associated with smoking status or number of fused levels, among other parameters. Although the study design of the present meta-analysis excluded infectious causes of pseudarthrosis from analysis, it is likely that at least some of these studies included patients with underlying occult infection, as protocols for intraoperative culture were not uniformly reported.…”

Indolent Infection After Lumbar Interbody Fusion: An Under-recognized Cause of Pseudarthrosis, Which Can Be Successfully Treated With Anterior Revision Fusion

“…7,12,14,[21][22][23] C acnes is likely an under-recognized cause of pseudarthrosis of the lumbar spine due to the need for multiple intraoperative cultures, extended culture time for positive results, and nonstandard hospital methodologies for the aseptic workup. 6 Steinhaus et al 13 recently examined presumed aseptic revision spinal surgeries and found both male sex and a diagnosis of pseudarthrosispredicted positive cultures, which were most commonly positive for C acnes. Shifflet et al also examined presumed aseptic revision surgery and found that in cases with positive cultures, C acnes grew in 48.9% and CoNS in 11.1%.…”

“…The average time to positive culture for C acnes was 6.1 days, reinforcing the need for extended incubation of cultures even in presumed aseptic cases. 14 Burkhard et al 6 found that 10.2% of cases were culture positive in revisions for presumed aseptic pseudarthrosis, with the results of C acnes 46.2% and CoNS 38.5% of the time. In patients without clinical signs of infection, Hu and Lieberman 22 found that C acnes was the most frequently identified pathogen of all the implants removed, comprising 46.7% of these infected implants.…”

“…10,11 Pseudarthrosis secondary to C acnes infection is often presumed to be aseptic because of its delayed presentation and often normal infectious laboratory values, including complete blood count, C-reactive protein, and erythrocyte sedimentation rate. 6,7,12,13 Because of the low virulence and slow growth of C acnes, prolonged incubation time, usually 2 weeks at minimum, is required for its identification as the source of fusion failure. 14 If pseudarthrosis secondary to infected lumbar interbody fusion is suspected, 1 proposed treatment strategy is revision anterior lumbar interbody fusion (ALIF).…”

“…5 However, recent reports have described infection as a common etiology for pseudarthrosis, particularly Cutibacterium acnes (C acnes) and coagulase-negative Staphylococcus (CoNS). [6][7][8][9] C acnes, formerly known as Propionibacterium acnes, is a gram-positive, anaerobic rod bacteria that is native to the hair follicles of the face, neck, and back. 10,11 Pseudarthrosis secondary to C acnes infection is often presumed to be aseptic because of its delayed presentation and often normal infectious laboratory values, including complete blood count, C-reactive protein, and erythrocyte sedimentation rate.…”