NCT03406624

Epigenetic and Molecular Biomarkers in Chronic Low Back Pain and Modic Changes

• Status: Completed
• Phase: —
• Study type: Observational
• Enrollment: 200 (actual)
• Sponsor: Oslo University Hospital · Academic / Other
• Sex: All
• Age: 18 Years
• Healthy volunteers: Not accepted

Summary

In the present study the investigators aim to examine the presence of bacteria in the disc and Modic Changes (MCs) (bone). A prospective study with 1-year follow-up of two patient populations undergoing elective spinal surgery (spinal fusion or disc herniation surgery) will be conducted. Patients previously operated on at index level will also be included, and evaluated as sub-groups. The following tissues are collected: dermis, sub-fascial tissue, nucleus pulposus, annulus fibrosus, and endplates. Endplate and anular biopsies are only performed in patients undergoing fusion surgery. In addition, air samples from the operating theatre during surgery are collected as negative controls. All tissue samples undergoing culturing should be processed within 4 hours of sampling. The time for sampling and culture processing is noted for each sample. Details are available in a published Method article. For each tissue sample, bacterial growth is recorded and identified at species level. Initially, the microbiologist grades the plates as "no growth", "possible contamination", and "significant growth". Possible contamination means that the bacteria may be derived from the environment and can be introduced at any step from the sample is taken to the analyses in the laboratory. The investigators will perform direct 16S rDNA nanopore sequencing on all frozen tissue samples and air samples. Other broad metagenomic methods may be considered, e.g., Illumina sequencing. Since Cutibacterium acnes is considered the main pathogen in this setting, the investigators will also use a specific quantitative PCR on all samples. In addition, the investigators will use whole genome sequencing on C. acnes isolates for phylogenetic analyses to compare isolates found in different samples from the same patient. Based on cultivation alone, samples will be graded as "significant growth", "possible contamination" or "no growth". Before unblinding, in preparation for the sensitivity analyses, "possible contamination" will be classified into a final categorization of "possible significant growth" or "no growth" based on PCR". In cases of a culture-negative nanopore-positive biopsy, the sample is classified as no growth when we find the same bacterial species in the air control sample as in the biopsy. Since the study was designed and the method article was prepared, nanopore sequencing technology has become available and incorporated into the present analysis. Although not part of the original protocol, nanopore sequencing was applied to the samples to complement the diagnostic approach. The results derived from nanopore sequencing will be included as part of prespecified sensitivity analyses to evaluate the robustness of the main finding. These analyses allow assessment of whether the inclusion of sequencing-based detection influences the overall estimates and conclusions, while maintaining the original study design. The microbiologists, the pathologist, statistician and clinicians are blinded until end of study. Blood-samples are collected to characterize gene expression patterns and related markers.

Detailed description

Planned analyses The investigators will perform the following analyses, with terms based on final categorization above: Primary analyses: I. Dependent variable (outcome): positive = significant growth, negative = no growth or possible significant growth. Main explanatory variable (group): MC1 vs. control II. Dependent variable (outcome): positive = significant growth, negative = no growth or possible significant growth. Main explanatory variable (group): MC2 vs. control For each of the primary analyses (I and II), we will perform the following sensitivity analyses: 1. st sensitivty analysis: Dependent variable (outcome): positive = significant growth or possible significant growth, negative = no growth and 16S rDNA nanopore sequencing positive. 2. nd sensitivity analysis: Dependent variable (outcome): positive = significant growth, possible significant growth or 16S rDNA nanopore sequencing positive, negative = no growth Exploratory analyses: The investigators will perform exploratory analyses using the following as main explanatory variables (using the same dependent variable as the primary analysis): I - MC1 and MC2 in previously operated vs. control II - Large MCs vs. control (significant growth from disc, yes/no). Large MCs are defined as MCs with volume ≥ 25 % of vertebral body volume or height \> 50 % of vertebral body height. III - MC1 and MC2 vs. control in fusion group (significant growth from vertebral body biopsy, yes/no). Vertebral body biopsies are not performed in the disc herniation group. For each of these three exploratory analyses, the investigators will consider to perform similar sensitivity analyses as for the primary analyses, depending on the results of those. Statistics and power: The main aim of this study is to investigate if the proportions of patients with significant bacterial growth from perioperative disc biopsies differ between cases (MC1 patients or MC2 patients) vs controls without MCs. The null hypothesis is that there is no difference between cases and controls. The alternative hypothesis is that there is a difference. The sample size calculation is based on previously published data and a pre-specified relevant difference in proportions of bacterial growth among cases vs. controls The investigators calculated the sample size using a two-sided Pearson's chi-squared test. For the primary analysis, with two primary endpoints, the investigators aim to achieve 80 % power to detect a difference in bacterial growth in 25 % of cases with MC1 or MC2 vs. 5% of controls. Due to multiple testing the investigators use Bonferroni correction (alfa 0.025). The investigators therefore plan to analyze at least 60 cases with MC1, 60 cases with MC2 and 60 controls. The MC2 sample is likely to become larger than n = 60, since the investigators recruit MC1 and MC2 patients consecutively and MC2 is more common than MC1. The primary endpoint will be analyzed with a logistic regression model with bacterial growth (positive/negative) as the outcome and group (MC1 or MC2 vs. control) as the main explanatory variable. After fitting the model, the model-predicted marginal probabilities of positive bacterial findings will be estimated for both groups. The effect measure will be the difference between the two probabilities, and will be reported with a 95 % confidence interval and a P-value for the null hypothesis of a zero difference. The standard error of the difference will be estimated using the delta method. The exploratory and sensitivity analyses will be carried out with the same model, after replacing outcome and main explanatory variable as appropriate. The subgroup analysis of previously operated will be carried out by adding previously operated as an interaction term between groups, and previously operated as covariates in the logistic model. A significant coefficient for the interaction term will indicate a subgroup effect.

Conditions

• Low Back Pain

Interventions

Type	Name	Description
PROCEDURE	Biopsy	Biopsies will be taken from disc and / or endplates during elective lumbar fusion surgery or disc herniation surgery (endplate biopsy is omitted in disc herniation surgery)

Timeline

• Start date: 2018-01-29
• Primary completion: 2026-04-03
• Completion: 2026-04-03
• First posted: 2018-01-23
• Last updated: 2026-04-14

Locations

4 sites across 1 country: Norway