4. Sample Size Calculation
CPSP
CHRONIC PAIN
Sample size calculation was performed using PASS 15.0 (Stata Corp. LP, College Station, Texas, USA), which relied on the chronic pain incidence at 3 months after surgery. According to our preliminary results of 38 cases (19 cases in the CPVB group and 19 cases in the CWI group), we found that the incidence of CPSP at 3 months was approximately 10.5% in the CPVB group and 42.1% in the CWI group. Using a two-proportion test with a power of 90% (