Correlation between modified Oxford grading scale and pelvic floor surface electromyography in assessment of pelvic floor muscle function in female patients with stress urinary incontinence

Objective: To investigate the characteristics of modified Oxford grading scale (MOS) and pelvic floor surface electromyography (sEMG) based on Glazer protocol in patients with stress urinary incontinence (SUI), and analyze the correlation between the two methods. Methods: This study was a cross-sectional survey. A total of 212 subjects in May 2019 were enrolled and divided into SUI group (n=61) and non-SUI group (n=151) based on the commonly used 3 incontinence questions (3IQ). MOS test and sEMG parameters were measured by the same rehabilitator. The sEMG parameters included the mean and variation coefficient in the prerest phase, the maximum and relaxation time of 5 rapid contractions, the mean and variability of EMG in 10 s tonic contraction phase, the mean and variability of EMG in 60 s endurance contraction phase, and the mean and variability of EMG in postrest phase. The differences of the above parameters between SUI group and non-SUI group were compared, the logistic regression and Spearman method were used to analyze the correlation between MOS and sEMG parameters. Results: The prevalence of SUI was 28.8%(61/212) in community, body mass index and delivery mode were the risk factors (all P<0.05). The MOS of the SUI group and the non-SUI group were 3 (2,3) and 3 (3,4), respectively, with significant difference (Z=-2.58, P=0.010). Among the sEMG parameters of SUI group and non-SUI group, the maximum values of phasic contractions were 23.12 (13.65, 37.89), 30.68 (20.28, 47.02) μV, the mean of tonic contractions were 14.32 (9.62, 21.49), 17.65 (12.05, 26.35) μV, and the mean of endurance contractions were 12.78(7.88, 18.76), 16.55(11.13, 22.40) μV, respectively, with statistical significance (Z=-2.34, -2.37, -3.20, all P<0.05). The multivariate logistic regression revealed that both the variation coefficient of tonic contractions (OR=157.86, 95%CI: 1.99-12 595.51, P<0.05) and the amplitude of endurance contractions(OR=1.11, 95%CI: 1.03-1.19, P<0.05) were correlated with SUI. The tonic contractions amplitude had the tendency to be related to SUI (OR=0.95, 95%CI: 0.09-1.00, P<0.05). In all subjects, MOS was correlated with the maximum value of rapid contractions, average value of tonic contractions and average value of endurance contractions (r=0.516, 0.503, 0.464, all P<0.05). In SUI group (r=0.510, 0.442, 0.385, all P<0.05), and non-SUI group (r=0.495, 0.524, 0.488, all P<0.05), MOS was correlated with the above parameters. Conclusions: MOS and sEMG based on Glazer protocol indicate that the contractility of pelvic floor muscle decreases in SUI patients. The results of sEMG and MOS are consistent, which can be used for quantitative evaluation of pelvic floor muscle function in SUI patients.