Reliability of Perineal Complex Stiffness Assessed Using Ultrasound Shear Wave Elastography

Abstract

The perineal complex (PC) transmits loads across the pelvic floor, stabilizing pelvic organs. Its mechanical properties may inform pelvic floor disorders yet remain unquantified in vivo. This study aimed to determine the analysis-stage intra- and inter-rater reliability of ultrasound-derived shear wave velocity (SWV) across three postures (supine, standing, deep squat) and two imaging planes (sagittal, subdivided into superficial and deep zones; and transverse) in 27 nulliparous females. SWV was extracted offline. Intra-rater reliability was excellent across all postures and images (ICC 0.968-0.995). Inter-rater reliability was excellent in the superficial zone and transverse plane (ICC 0.951–0.989) and good in the deep zone (ICC 0.864–0.882). Deep-zone signal dropout reduced usable trials in standing. Posture modulated stiffness, with deep squat increasing SWV and optimizing deep-zone image quality. Offline SWV analysis of the PC is highly reproducible and potentially sensitive to posture-related differences, though deep-zone acoustic attenuation remains a primary feasibility constraint.