The relationship between estimates of puborectalis muscle shear modulus made with shear wave elastography and electromyography in healthy men

Abstract

Aims:This study aimed to: (i) describe a method to estimate shear modulus of the male puborectalis muscle using shear wave elastography (SWE); (ii) investigate the relationship between changes in shear modulus and electromyography (EMG) of the left and right puborectalis muscle; (iii) investigate whether measures made at rest differ before and after a maximal voluntary contraction; and (iv) investigate whether rest measures are consistent over repeated submaximal contractions. Materials and Methods:Eleven males with no history of pelvic symptoms participated. Puborectalis muscle SWE was recorded using a transperineal ultrasound. Puborectalis EMG was recorded with a custom electrode stabilized to the anal mucosa with suction. Measures were made during rest and contractions at 10, 20, 30, 50 and 75% of maximal voluntary contraction (EMG). Correlation between normalized EMG and shear modulus data over contraction intensities was calculated (left; right). Amplitude of each measure at rest was compared before and after maximum voluntary contraction and before each submaximal contraction. Results:Group data showed strong linear correlations between shear modulus and EMG for the left r2=0.71 [SD 0.16; 95% CI 0.61−0.81], and right r2=0.56 [0.33; 0.35−0.76] puborectalis and there was no difference in the correlation between sides (p = 0.17), or between rest values of EMG or shear modulus before and after maximal and submaximal contractions (all p>0.31). Conclusions:This study confirms the viability of SWE for measurement of the puborectalis muscle in men and validity of changes in SWE as an estimate of shear modulus/stiffness of this muscle. Healthy men returned to rest values after contraction at different intensities.