Continuous variables will be analyzed using independent t-test or Mann Whitney U test as per the distribution of the data for continuous variables. Categorical variables will be analyzed using Chi-square test or Fisher's exact test. P-value < 0.05 will be considered statistical significant. Risk factors of ISP will be analyzed using univariate and multivariate binary regression with robust estimates to calculate odds ratio (OR) and their 95% confidence interval. A manual stepwise forward logistic regression will be used to extract univariate independent variables. A p value ≤ 0.2 by univariate analysis will be used as the criterion for choosing variables to be included in the model for multivariate analysis. A p value <0.05 is considered statistically significant. Cut-off points of the independent variables, including age group and duration of surgery, are estimated by the method of maximum likelihood to achieve best discrimination between patients with and without ISP.