Here is the design of a clinical trial:

Official Title: Spinal Cord Stimulation System in the Treatment of Chronic Pain

Included conditions:
- Pain
- Chronic Pain
- Back Pain
- Spinal Cord Stimulation
- Nervous System Diseases

Study Armgroups:
- {'label': 'Experimental', 'type': 'EXPERIMENTAL', 'description': "Subjects' PINS spinal cord stimulator randomized to this arm is on always", 'interventionNames': ['Device: PINS Spinal Cord Stimulator']}
- {'label': 'Control', 'type': 'SHAM_COMPARATOR', 'description': "Subjects' PINS spinal cord stimulator randomized to this arm is off for a week", 'interventionNames': ['Device: PINS Spinal Cord Stimulator']}

Interventions:
- {'type': 'DEVICE', 'name': 'PINS Spinal Cord Stimulator', 'description': 'Subjects will be implanted with PINS spinal cord stimulator', 'armGroupLabels': ['Control', 'Experimental']}

Primary Outcomes:
- {'measure': 'The difference of Visual-analogue scale (VAS) between the experimental group and the control group', 'description': 'Pain will be evaluated in the different groups according to the Visual-analogue scale (VAS) varying from 0 to 10 with a higher score indicating a higher level of pain.', 'timeFrame': '13 weeks'}

Please estimate the sample size based on the assumption: 
80% power to detect the significant difference using a two-sided, two-sample t test at a significance level (alpha) of 0.025. The first class error level (alpha) is 0.025 for unilateral test and 0.05 for bilateral test. The second class error level (beta) is 0.2. The maximum possible loss rate is 10%.
Sample size and power calculations
        The primary comparison is the difference between EG and CG in terms of VAS score in the withdrawal period. According to the results of the study [25], the clinically important outcome of VAS score is 20âmm at most, which does not vary with gender, age, cause, or severity of pain [26, 27]. A sample size of 48 (24 per arm) achieves 80% power to detect the significant difference using a two-sided, two-sample t test at a significance level (alpha) of 0.025. We assumed the true difference between the means to be 0 and a standard deviation of the outcome of 2.6. Thus, the sample size calculation formula was:
        
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				\begin{document}$$ n=\frac{2{\left({Z}_{1-\alpha /2}+{Z}_{1-\beta}\right)}^2{\delta}^2}{{\left(\left|D\right|-\Delta  \right)}^2} $$\end{document}n=2Z1âÎ±/2+Z1âÎ²2Î´2Dââ2
        where |D| is the expected mean difference of the two groups, â is the superiority threshold value (0, here),Â Z is the quantile of the standard normal distribution, Î± is the first class error level for the statistical test (0.025, here for unilateral test; 0.05 for bilateral test if need), and Î² is the second class error level for the statistical test (0.2, here). The calculated sample size per group through this calculation is 21. Considering that the maximum possible loss rate is 10%, the total sample size is 24 pairs (NÂ =â48) [24].
        These 48 cases will use the G122R rechargeable IPG combined with percutaneous leads (PINS, Inc., Beijing, BJ, China). For the non-rechargeable model G122 and paddle lead, other 6 participants will be recruited for each condition (3 cases for each). No statistical requirements are needed for these 6 cases. In summary, the final sample size is 54 (24 pairs plus extra 6).
        To implement within-group comparisons, data will be analyzed with t tests and Ï2 tests for continuous variables and categorical variables, respectively. The Kolmogorov-Smirnov test or parametric tests will be performed with the data of normal distributions. Rank-sum test will be used for the non-parametric data. The factors that affect curative effects will be analyzed with a multinomial logistic regression method. A p value <â0.05 will be considered as statistically significant. A validated statistical software package will be used for the analyses of the study results (for example, SAS).