prospective

1. Patient enrollment:~ We plan to prospectively enroll at least 400 patients with lumbar disc herniation indicated for lumbar microdiscectomy~2. Preoperative data collection:~ Baseline epidemiological, radiological and clinical data including survey questionnaires will be collected from each patient.~3. Peri-operative tissue collection:~ Peri-operatively collected tissue samples of the herniated intervertebral disc will be immediately sent for histological examination.~4. Microbiological examination:~ The presence, quantification, phylotyping of C.acnes and other bacteria, including virulence factors and antimicrobial susceptibility in the collected disc tissue will be examined by a microbiologist.~5. Post-operative follow-up visits:~Post-operative clinical status will be assessed using questionnaires at follow-up visits at 6 weeks, 6, and 12 months after surgery

retrospective

All patients in retrospective cohort have completed epidemiologic, MRI or CT, microbiological, and clinical data. The epidemiological data include age, gender, disc herniation relapse, epidural steroid injection before the surgery, body mass index (BMI), the lumbar segment of herniation, type of herniation, and physical workload. The clinical data include microbiological findings from perioperatively collected disc tissue, preoperative spinal MRI, preoperative and postoperative pain intensity according to the visual analog scale (VAS), and functional disability for low back pain quantified by the Oswestry Disability Questionnaire (ODQ). In this part of the project, microbiological findings will be studied together with radiological changes in preoperative MRI and clinical status before and after surgery.