Here is the design of a clinical trial:

Official Title: Randomized, Double-blind, Placebo-controlled, Multicenter Efficacy Study of the Gelstix™ Device to Treat Chronic Discogenic Low Back Pain

Included conditions:
- Degeneration of Lumbar Intervertebral Disc

Study Armgroups:
- {'label': 'Gelstix', 'type': 'EXPERIMENTAL', 'description': 'The intradiscal insertion of the GelStix™ Nucleus Augmentation Device.', 'interventionNames': ['Device: GelStix™ Nucleus Augmentation Device']}
- {'label': 'Placebo', 'type': 'PLACEBO_COMPARATOR', 'description': 'Intradiscal saline solution (1 mL NaCl 0.9%) injection.', 'interventionNames': ['Other: Placebo']}

Interventions:
- {'type': 'DEVICE', 'name': 'GelStix™ Nucleus Augmentation Device', 'description': 'Intradiscal Gelstix insertion', 'armGroupLabels': ['Gelstix'], 'otherNames': ['Hydrogel']}
- {'type': 'OTHER', 'name': 'Placebo', 'description': 'Intradiscal saline injection', 'armGroupLabels': ['Placebo'], 'otherNames': ['Saline, NaCl 0,9%']}

Primary Outcomes:
- {'measure': 'Change in Lumbar Pain intensity measured on Numeric Rating Scale', 'description': "Pain intensity will be assessed employing an 11-point (i.e. 0-10) NRS with 0 meaning 'no pain' and '10' meaning 'worst possible pain'. Three times daily pain scores will be assessed for five consecutive days around the intended measurement time.", 'timeFrame': 'The mean NRS scores on the pain diary will be measured at baseline, and at one week, and one, three, six (primary outcome) and twelve months.'}

Please estimate the sample size based on the assumption: 
80% power, alpha of 5% (two-tailed), 20% expected drop-out rate
Sample size
        Twenty-eight patients per group will be required to have 80% power to detect a minimally clinically relevant difference of 1.5 points on the NRS between groups, with an estimated SD of 2, based on the pooled SD of NRS scores of similar patients in the RCT of Kallewaard et al,29 and testing with an alpha of 5% (two tailed). With an expected drop-out rate of about 20%, a total of 72 patients will be randomised.