Here is the design of a clinical trial:

Official Title: An Open-Label Randomized Controlled Study of the Efficacy of Surgical Treatment in Patients With Single Level Lumbar Spinal Stenosis Using Minimally Invasive Decompression and Fusion and Traditional Open

Included conditions:
- Lumbar Spinal Stenosis
- Intervertebral Disc Degeneration

Study Armgroups:
- {'label': 'Minimally invasive TLIF', 'type': 'OTHER', 'description': 'Patients will undergo a single level decompression and fusion using a minimally invasive technique. Followed posterior screw fixation is mandatory.', 'interventionNames': ['Procedure: lumbar fusion']}
- {'label': 'Open TLIF', 'type': 'OTHER', 'description': 'Patients will undergo a single level decompression and fusion using an open traditional technique. Followed posterior screw fixation is mandatory.', 'interventionNames': ['Procedure: lumbar fusion']}

Interventions:
- {'type': 'PROCEDURE', 'name': 'lumbar fusion', 'description': 'Transforaminal Lumbar Interbody Fusion will be performed using minimally invasive approach or traditional open technique.', 'armGroupLabels': ['Minimally invasive TLIF', 'Open TLIF']}

Primary Outcomes:
- {'measure': 'Change from baseline in Oswestry Disability Index (ODI)', 'description': 'To observe the change of ODI as compared to baseline through follow-up terms. min - 0, - the best result, patient is active; max - 50 - the worst result, patient is not physically active', 'timeFrame': '3 months'}

Please estimate the sample size based on the assumption: 
One-sided Mann-Whitney U test, significance level p=0.05, power 80%, 20% dropout rate
Sample size
        Under non-inferiority design, the sample size was calculated for ODI difference between the values before intervention and 3 months after. Assuming mean of ODI difference is 39 and SD of ODI difference is 19.3 in both groups (based on our own published data (18.8 at 1-year follow-up,27 19.3 at 3-month follow-up28), the non-inferiority margin Î´=12, for a one-sided Mann-Whitney U test with a critical significance p=0.05âand test power is 80%, it is enough to allocate 38 patients. Considering the 20% loss, the total sample size will be 96 patients, 48 in each group.
        The exact number of patients might be adjusted based on actual dropout rate achieved by the time of interim analysis.