This is a cross-sectional study. All patients older than 18 years treated for rectal cancer, Low Anterior Resection (LAR), LAR preceded by Short Course Radiotherapy (SCRT), LAR preceded by Chemoradiotherapy (CRT), or CRT alone, in our hospital between January 2014 and December 2018 were eligible for selection. Exclusion criteria were abdomino- perineal resection (APR), Hartman resection, patients with a diverting colostoma neurological comorbidity (spinal lesion or cerebrovascular accident (CVA)) or muscle disease (Multiple Sclerosis (MS)), local relapse and metastasis in a distant organ.
Seventy-six of two hundred twenty eight patients were eligible to participate in this study and invited to participate.
All participants completed five questionnaires containing 24 questions for women and 24 questions for men, the LARS score, the Vaizey score, the International Prostate Symptom Score (IPSS), the International Consultation on Incontinence Questionnaire Urinary Incontinence Short Form (ICIQ-UI SF) , the International Index of Erectile Function (IIEF-5) questionnaire (only for men) and Item 34 in the EORTC-QLQ-CR 29 questionnaires about sexual functioning in women (only for women).
For EMG- assessment of the pelvic floor muscles we use the Multi Array Probe Leiden, the MAPLe® (Novuqare Pelvic Health B.V. CE 0344). The MAPLe® is a probe for EMG registration of the pelvic floor musculature (PFM) with a matrix of 24 electrodes enabling the measurement of EMG activity from the different sides and layers of the PFM(3).
Participants were asked to perform three consecutive tasks according to a standardized protocol: one-minute rest, ten maximum voluntary contractions (MVC’s), and three endurance contractions. Mean raw EMG values per electrode (24 in total) were calculated for tone at rest, for mean MVC and mean endurance contraction.
Correlations between the LARS score and the EMG values consecutively calculated per specific layers of the pelvic floor muscles, the m.puborectalis and m.sphincter ani externus, and per specific nerves, n.pudendus, n.levator ani. In these analyses we take into account to calculate separately the EMG values of rest, MVC’s and endurance contractions.
From these correlations p-values were obtained.
A sample size of 46 achieves 80% power to detect a difference of -0.40000 between the null hypothesis correlation of 0.00000 and the alternative hypothesis correlation of 0.40000 using a two-sided hypothesis test with a significance level of 0.05000.
In order to correct for multiple testing, correlation between EMG values of the pelvic floor and the IPSS score, Vaizey score, ICIQ, IIEFF we used a significance level of 0.00500.