An Automated Hand-Held Elastometer for Quantifying the Passive Stiffness of the Levator Ani Muscle in Women

AimDesign and develop an automated, hand-held instrument (elastometer) to assess in vivo passive stiffness of the pelvic floor muscle. Materials and MethodsThe elastometer system consisted of a hand piece, real-time controller, and laptop computer. A cable connected the hand-piece to the controller, which communicated with a laptop computer via an ethernet connection. Force sensitivity calibration and displacement accuracy were determined experimentally using a spring load and an Instron mechanical tester. A test re-test series quantified the in vivo repeatability (within a procedure) and reproducibility (between procedures after a 5min delay) of passive stiffness in volunteers (n=20). Stiffness was determined from the gradient of the force-displacement curve for each cycle. ResultsThe force-aperture spring measurements from the elastometer showed consistent (r(2)=1.0000) agreement with those measured by the Instron. The difference between spring stiffness as measured by the elastometer and the Instron (388.1N/m cf. 388.5N/m, respectively) was negligible. The intra-class correlation coefficient for repeatability within procedures was 0.986 95% CI (0.964-0.994) n=20, and reproducibility between procedures ICC 0.934 (95% CI 0.779-0.981) n=12. Bland-Altman analysis determined a bias of 0.3 and 18.5N/m, for repeatability and reproducibility respectively. Neither bias is likely to be clinically significance. ConclusionThe elastometer demonstrated very good repeatability and accuracy in the measurement of force/displacement during in vitro testing. There was a high degree of repeatability and reproducibility in stiffness measurements in a test re-test series. Our results demonstrate the elastometer is accurate and reliable and thereby suitable for larger clinical trials. Neurourol. Urodynam. 34:133-138, 2015. (c) 2013 Wiley Periodicals, Inc.