The uterine suspensory tissue (UST), which includes the cardinal (CL) and uterosacral ligaments (USL), plays an important role in resisting pelvic organ prolapse (POP). We describe a technique for quantifying the in vivo time-dependent force-displacement behavior of the UST, demonstrate its feasibility, compare data from POP patients to normal subjects previously reported, and use the results to identify the properties of the CL and USL via biomechanical modeling. Fourteen women with prolapse, without prior surgeries, who were scheduled for surgery, were selected from an ongoing study on POP. We developed a computer-controlled linear servo actuator, which applied a continuous force and simultaneously recorded cervical displacement. Immediately prior to surgery, the apparatus was used to apply three “ramp and hold” trials. After a 1.1 N preload was applied to remove slack in the UST, a ramp rate of 4 mm/s was used up to a maximum force of 17.8 N. Each trial was analyzed and compared with the tissue stiffness and energy absorbed during the ramp phase and normalized final force during the hold phase. A simplified four-cable model was used to analyze the material behavior of each ligament. The mean ± SD stiffnesses of the UST were 0.49 ± 0.13, 0.61 ± 0.22, and 0.59 ± 0.2 N/mm from trial 1 to 3, with the latter two values differing significantly from the first. The energy absorbed significantly decreased from trial 1 (0.27 ± 0.07) to 2 (0.23 ± 0.08) and 3 (0.22 ± 0.08 J) but not from trial 2 to 3. The normalized final relaxation force increased significantly with trial 1. Modeling results for trial 1 showed that the stiffnesses of CL and USL were 0.20 ± 0.06 and 0.12 ± 0.04 N/mm, respectively. Under the maximum load applied in this study, the strain in the CL and USL approached about 100%. In the relaxation phase, the peak force decreased by 44 ± 4% after 60 s. A servo actuator apparatus and intraoperative testing strategy proved successful in obtaining in vivo time-dependent material properties data in representative sample of POP. The UST exhibited visco-hyperelastic behavior. Unlike a knee ligament, the length of UST could stretch to twice their initial length under the maximum force applied in this study.
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February 2014
Research-Article
In Vivo Properties of Uterine Suspensory Tissue in Pelvic Organ Prolapse
Jiajia Luo,
Jiajia Luo
1
Biomechanics Research Laboratory,
Department of Mechanical Engineering,
University of Michigan,
Ann Arbor, MI 48109;
Department of Mechanical Engineering,
2350 Hayward Street
,GG Brown Building 3212
,University of Michigan,
Ann Arbor, MI 48109;
1Corresponding author.
Search for other works by this author on:
Tovia M. Smith,
Tovia M. Smith
Department of Obstetrics and Gynecology,
University of Michigan
,Ann Arbor, MI 48109
;Pelvic Floor Research Group,
University of Michigan,
Ann Arbor, MI 48109
University of Michigan,
Ann Arbor, MI 48109
Search for other works by this author on:
James A. Ashton-Miller,
James A. Ashton-Miller
Biomechanics Research Laboratory,
Department of Mechanical Engineering,
Department of Mechanical Engineering,
University of Michigan
,Ann Arbor, MI 48109
;Pelvic Floor Research Group,
Ann Arbor, MI 48109
University of Michigan
,Ann Arbor, MI 48109
Search for other works by this author on:
John O. L. DeLancey
John O. L. DeLancey
Department of Obstetrics and Gynecology,
University of Michigan
,Ann Arbor, MI 48109
;Pelvic Floor Research Group,
University of Michigan,
Ann Arbor, MI 48109
University of Michigan,
Ann Arbor, MI 48109
Search for other works by this author on:
Jiajia Luo
Biomechanics Research Laboratory,
Department of Mechanical Engineering,
University of Michigan,
Ann Arbor, MI 48109;
Department of Mechanical Engineering,
2350 Hayward Street
,GG Brown Building 3212
,University of Michigan,
Ann Arbor, MI 48109;
Tovia M. Smith
Department of Obstetrics and Gynecology,
University of Michigan
,Ann Arbor, MI 48109
;Pelvic Floor Research Group,
University of Michigan,
Ann Arbor, MI 48109
University of Michigan,
Ann Arbor, MI 48109
James A. Ashton-Miller
Biomechanics Research Laboratory,
Department of Mechanical Engineering,
Department of Mechanical Engineering,
University of Michigan
,Ann Arbor, MI 48109
;Pelvic Floor Research Group,
Ann Arbor, MI 48109
University of Michigan
,Ann Arbor, MI 48109
John O. L. DeLancey
Department of Obstetrics and Gynecology,
University of Michigan
,Ann Arbor, MI 48109
;Pelvic Floor Research Group,
University of Michigan,
Ann Arbor, MI 48109
University of Michigan,
Ann Arbor, MI 48109
1Corresponding author.
Contributed by the Bioengineering Division of ASME for publication in the Journal of Biomechanical Engineering. Manuscript received September 6, 2013; final manuscript received November 26, 2013; accepted manuscript posted December 3, 2013; published online February 5, 2014. Editor: Victor H. Barocas.
J Biomech Eng. Feb 2014, 136(2): 021016 (6 pages)
Published Online: February 5, 2014
Article history
Received:
September 6, 2013
Revision Received:
November 26, 2013
Accepted:
December 3, 2013
Citation
Luo, J., Smith, T. M., Ashton-Miller, J. A., and DeLancey, J. O. L. (February 5, 2014). "In Vivo Properties of Uterine Suspensory Tissue in Pelvic Organ Prolapse." ASME. J Biomech Eng. February 2014; 136(2): 021016. https://doi.org/10.1115/1.4026159
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