STATISTICAL ANALYSIS
The Generalized Estimating Equations method was used to evaluate the association between the variables and pain or complications. The estimates were calculated by maximum likelihood in order to avoid bias on the difference in the number of PLB for each patient. Observations within a given patient were not independent and intra-patient correlation and variation were introduced into the analysis using a mixed generalized linear model.
The Chi-square or Fisher’s exact tests were used to compare categorical variables and the Mann-Whitney test for numerical variables. Statistical analysis was performed using the SAS for Windows version 9.4 system. The level of statistical significance adopted in the analysis was 5%.