Is pseudarthrosis after spinal instrumentation caused by a chronic infection?
To assess whether a chronic bacterial infection is present in a subset of patients with pseudarthrosis after instrumented spinal fusion.
This was a prospective diagnostic study including adult patients with previous instrumented spinal fusion. Patients underwent revision surgery for either pseudarthrosis or other causes (e.g. implant removal, curve progression or junctional kyphosis) (control group). Five separate biopsies were randomly collected, intraoperatively, from the pseudarthrosis site and cultivated under both aerobic (5 days) and anaerobic (14 days) conditions. If cultivation was positive in at least 2/5 tissue samples, the biopsy was sectioned and stained using peptide nucleic acid fluorescence in situ hybridization (PNA-FISH). Confocal laser scanning microscopy was used to examine the sections and visualize bacterial aggregates.
The study included 32 pseudarthrosis and 32 control patients. Cultivation yielded bacteria in at least 1/5 biopsies in 52% of patients with no difference between the groups (p = 1.0). Bacteria of the same species was found in at least 2/5 samples in seven pseudarthrosis patients and four controls (p = 0.509). Propionibacterium acnes was found in 8 of these 11 samples. Microscopy demonstrated tissue-embedded bacterial aggregates in two of these patients but with no inflammatory cells indicating an active infection. The presence of bacteria was not associated with the number of previous spinal procedures or the pre-revision fusion length (p ≥ 0.503).
Pseudarthrosis after instrumented spinal surgery was not significantly associated with the presence of bacteria at the pseudarthrosis site. Positive cultivation results are common after spinal instrumentation, but our results indicate that they rarely represent an organized infection.
KeywordsPseudarthrosis Non-union Spinal instrumentation Adult spinal deformity Infection
Søren Ohrt-Nissen received an institutional research grant from K2 M outside the submitted work. Thomas Bjarnsholt received a grant from The Lundbeck Foundation outside the submitted work.
Compliance with ethical standards
Conflict of interest
Benny Dahl received consultant fees outside the submitted work from K2 M.
Approval from the Ethical committee (H-6-2014-024) and the Danish Data Protection Agency (2007-41-1506) was obtained prior to the study.