Histological analysis of surgical samples and a proposed scoring system for infections in intervertebral discs

Bacterial growth in patients with low back pain and Modic changes: protocol of a multicentre, case-control biopsy study

INTRODUCTION

Bacterial infection and Modic changes (MCs) as causes of low back pain (LBP) are debated. Results diverged between two randomised controlled trials examining the effect of amoxicillin with and without clavulanic acid versus placebo on patients with chronic LBP (cLBP) and MCs. Previous biopsy studies have been criticised with regard to methods, few patients and controls, and insufficient measures to minimise perioperative contamination. In this study, we minimise contamination risk, include a control group and optimise statistical power. The main aim is to compare bacterial growth between patients with and without MCs.

METHODS AND ANALYSIS

This multicentre, case-control study examines disc and vertebral body biopsies of patients with cLBP. Cases have MCs at the level of tissue sampling, controls do not. Previously operated patients are included as a subgroup. Tissue is sampled before antibiotic prophylaxis with separate instruments. We will apply microbiological methods and histology on biopsies, and predefine criteria for significant bacterial growth, possible contamination and no growth. Microbiologists, surgeons and pathologist are blinded to allocation of case or control. Primary analysis assesses significant growth in MC1 versus controls and MC2 versus controls separately. Bacterial disc growth in previously operated patients, patients with large MCs and growth from the vertebral body in the fusion group are all considered exploratory analyses.

ETHICS AND DISSEMINATION

The Regional Committees for Medical and Health Research Ethics in Norway (REC South East, reference number 2015/697) has approved the study. Study participation requires written informed consent. The study is registered at ClinicalTrials.gov (NCT03406624). Results will be disseminated in peer-reviewed journals, scientific conferences and patient fora.

TRIAL REGISTRATION NUMBER

NCT03406624.

Lumbar Intervertebral Disc and Discovertebral Segment. Part 2: An Imaging Review of Pathologic Conditions With Anatomic Correlation

The lumbar intervertebral disc is a complex anatomic structure that can be affected by a number of distinct pathologic processes. Categories of the disease include degenerative changes, subclinical or overt trauma, infectious lesions, inflammatory insults, metabolic disease, and tumors. Abnormalities affecting the intervertebral disc may assume atypical appearances or alterations may as well mimic pathologic processes related to degeneration that can be asymptomatic. Although the imaging findings of degenerative diseases of the vertebral column have been emphasized extensively, the assembly of pathologic conditions associated with the discovertebral segment has not received adequate attention. This manuscript reviews and illustrates a range of abnormalities affecting the discovertebral segment, providing a detailed analysis of postmortem material, in the realm of a close anatomic-imaging correlation. Knowledge of the characteristic morphology and patterns of abnormal conditions affecting the intervertebral disc and discovertebral segment can help radiologists narrow the differential diagnosis in a broad spectrum of disease processes.

Degenerate-disc infection study with contaminant control (DISC): a multicenter prospective case-control trial

BACKGROUND

A bacterial cause of disc degeneration has evoked several controversies and, if true, would lead to a major shift in treatment paradigm. Earlier studies analyzing the relationship of bacterial disc infection within a degenerative cohort featured prolonged cultures susceptible to contamination. The degenerate-disc infection study with contaminant control (DISC) trial aims to investigate this theory further by examining infection rates using a non-degenerative control cohort in comparison to a degenerative internal control cohort and a sham cohort (sampling only sterile paraspinal tissue). To our knowledge, the current study is the largest evaluating the growth of organisms (or possible contamination rate) in paraspinal tissue if prolonged cultures are performed. Protocols on methodology have been previously published.

PURPOSE

(1) To investigate the infection rates across cohorts (degenerative vs. nondegenerative control; paraspinal and/or disc controls vs. combined sampling cohorts) using stringent standardized aseptic surgical technique and laboratory processing. (2) To compare our findings to that of the literature and make a statement in support and/or against a possible contamination theory to positive cultures.

STUDY DESIGN

Multicenter, multisurgeon case-control trial.

PATIENT SAMPLE

In all, 812 surgical samples were retrieved across a 3.5-year period (2013-2016) including 25 trauma controls (nondegenerative), 550 "disc and paraspinal" samples (degenerative cases with internal control), 190 disc-only samples (degenerative cases without internal control), and 46 paraspinal only controls (sham group).

OUTCOME MEASURES

Growth and/or Contamination rate (%) per cohort. Chi-square of growth in disc versus paraspinal samples as a means of examining the distribution of false positive and contaminant growth. The impact of previous injections and/or surgery on positive disc or paraspinal growth. Correlation of Modic changes with positive growth rates analyzed with the Kruskal-Wallis Test. The distribution of species in positive samples were also analyzed.

METHODS

The DISC trial is registered under Australian and New Zealand clinical trials registry-ACTRN12616000541404. Institutional ethics review was obtained (HREC northern sector 13/218) at the primary center and further centers (n=6) were recruited. Patients undergoing spinal surgery with discectomy were eligible for trial entry with tissue specimens obtained using strict aseptic technique for microbiological examination. All specimens were handled with sterile instruments only and by a fresh instrument to a sterile pot that was closed immediately. Separate pots were used for the disc and paraspinal tissue respectively with similar stringent processing during microbiological assessment. A cohort of the degenerative cases at one single institution also underwent an additional histopathological examination.

RESULTS

There was an expected significant difference in gender and age associated with the non-degenerative control group (due to trauma patients) compared with other cohorts. There was a higher percentage of positive-growth in the control group in comparison to the disc and paraspinal and disc only groups across positive disc growth (48% vs. 27% vs. 17%, p<.001). A similar infection rate was observed in the paraspinal samples across the equivalent controls (44% vs. 36% vs. 37%, p=.739). There was a significant difference in the proportions of positive growth with a large proportion of false positives (growth in both disc and paraspinal samples; p<.001). There was no difference in true positive growth between the case and control groups (16.0 vs. 7.7%, p=.112). These trends were preserved across all cohorts and when stratifying by spinal segment (cervical or lumbar). There was no correlation between Modic changes and positive disc culture growth (p=.398, n=144 samples). Cutibacterium (formerly Propionibacterium) acnes was the most dominant pathogen isolated, representing between 50% and 70% of positive disc and paraspinal specimens, followed by staphylococcal species.

CONCLUSIONS

Our study failed to find a difference in true infection rates between the nondegenerative and degenerative disc populations. These findings are suggestive of a contamination theory and against a common infective etiology in the setting of discogenic back and neck pain. We believe the rationale for antibiotic therapy in the management of discogenic back pain warrants further evidence to establish efficacy.

Abnormal Conditions of the Diskovertebral Segment: MRI With Anatomic-Pathologic Correlation

OBJECTIVE. The purpose of this article is to review the appearance of various abnormalities that affect the lumbar intervertebral disk and diskovertebral segment through anatomic-pathologic correlation in cadavers. CONCLUSION. Familiarity with the pathologic conditions in and around the intervertebral disk is important in recognizing such conditions as a potential source of symptoms. We revisit the principal role of MRI in evaluating these abnormalities and excluding other sources of significant clinical manifestations.

Degenerate-disc Infection Study with Contaminant Control: Discussion on the Research Methods

OBJECTIVE

The role of bacterial infection in the causation of disc degeneration and its consequences is controversial. The current evidence is limited to underpowered studies, with the majority of such studies having only an internal contaminant arm, and only one study having a control arm with a non-degenerate disc population. The Degenerate-disc Infection Study with Contaminant Control (DISC) study includes a control arm and an internal contaminant control to resolve these shortcomings.

METHODS

The study is designed as a case-control study: cases are patients undergoing surgery for degenerated disc pathology and controls are patients undergoing surgery for non-degenerate pathology, such as trauma, scoliosis or tumor cases.

RESULTS

This study is part of a multi-centric trial involving six spine centers with 15 spine surgeons contributing. The DISC study methodology, rationale and controversies are presented here. The predominant issue is how to interpret contamination. We present our algorithm for the DISC study to address this. For disc samples that are positive concurrently with positive paraspinal tissue sample, the result will be interpreted as contamination. For positive disc samples with a negative paraspinal tissue culture result, the interpretation of this result will be infection. If cultures for both disc sample and paraspinal tissue sample are negative, then the result is interpreted as non-infected. If the disc culture is negative but paraspinal tissue culture is positive, then it is treated as a contaminant.

CONCLUSIONS

Future large-scale studies are required with a good control arm, a contamination arm, and histopathological correlations.

One-stage posterior debridement and fusion combined with irrigation and drainage for the treatment of postoperative lumbar spondylodiscitis

Objective

The aim of this study was to evaluate the clinical outcomes of one-stage posterior debridement, interbody fusion, and instrumentation, combined with irrigation and drainage, for treating lumbar spondylodiscitis.

Methods

The study included 23 patients (13 male and 10 female, mean age: 45 years) who had posterior debridement, interbody fusion, and instrumentation, followed by continuous closed irrigation and drainage for lumbar postoperative spondylodiscitis. The visual analog scale, Oswestry disability index, and lumbar lordosis angle were assessed before and after surgery to evaluate the clinical outcome.

Results

The mean follow-up time was 27 (24–36) months. All patients tolerated the procedure well, and there were no instances of spondylodiscitis recurrence, though a dorsal dermal sinus developed in one patient after surgery. Infection was eliminated, as evidenced by the normalization of the erythrocyte sedimentation rates and C-reactive protein levels. The mean visual analog scale scores were significantly decreased after the operation. The mean lumbar lordosis angle before surgery was 21.61 ± 6.88° and the angle at the final follow-up was 31.61 ± 4.24°. The mean Oswestry disability index scores improved significantly both after the operation and at the follow-up visits (p < 0.05). Bone union was confirmed in all patients at a mean of 8.6 months post-operation, though this was not achieved until 2 years post-operation in one patient. All 3 patients who had neurological deficits showed great improvement at the last follow-up.

Conclusion

Surgical management using one-stage posterior debridement, interbody fusion, and instrumentation, followed by continuous closed irrigation and drainage, might be an effective treatment option for lumbar postoperative spondylodiscitis.

Level of evidence

Level IV, Therapeutic study.