Mechanical Characterization of Ring Pessary Folding

Abstract

Purpose

Understanding the mechanical properties of current pessaries is important to improve on existing designs and innovate on novel solutions. Our objective was to mechanically characterize the force required to compress ring pessaries into a folded shape. We hypothesized that the force required to fold ring pessaries would scale inversely with the diameter squared.

Methods

We conducted a compression test on ring pessaries to analyze their folding behavior using a mechanical universal testing system. Ring pessaries size #1 through #7 (diameters 50.1–86.7 mm) were placed in the testing platform in a vertical orientation with the bending axis in the horizontal plane. An axial load was applied to induce deformation.

Results

With application of an axial force, all pessaries first showed in-plane deformation followed by out-of-plane buckling. Increasing force resulted in a transition between in-plane deformation and out-of-plane buckling, during which the pessary began to fold, analogous to classic Euler buckling of columns. This transition was reflected in the loading curve as a sharp change in slope between the initial strain-softening region and a subsequent nearly horizontal plateau region. The force at the transition point ranged from 4.4 N for a size #7 pessary to 23.5 N for a size #1 pessary. The relationship between force and diameter at the transition point appeared to approximate a 1/L2 dependence, where L is the pessary diameter.

Conclusions

Pessary mechanics show buckling and folding behavior with a dependence on pessary architecture. The force required to fold ring pessaries scales inversely with the pessary diameter squared.

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Availability of Data and Material

All data will be made available per request.

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Funding

This project was partially funded by Penn Health-Tech at University of Pennsylvania.

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Affiliations

Authors

Contributions

CXH: project development, data analysis, manuscript writing/editing. MC: data collection, data analysis, manuscript writing/editing. HY: data analysis, manuscript writing/editing. EM: manuscript writing/editing. LAA: project development, manuscript writing/editing. JRR: project development, data analysis, manuscript writing/editing.

Corresponding author

Correspondence to Christopher X. Hong.

Ethics declarations

Conflict of interest

Christopher X. Hong is a consultant/advisor for Cosm Medical Corp., Toronto, ON, Canada. All other authors disclose no conflicts of interest.

Ethical Approval

This study did not meet the criteria for human subject research and was thus exempt from Institutional Review Board review.

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Hong, C.X., Cioban, M., Yasuda, H. et al. Mechanical Characterization of Ring Pessary Folding. J. Med. Biol. Eng. 41, 343–349 (2021). https://doi.org/10.1007/s40846-021-00618-y

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Keywords

  • Fitting
  • Pessary
  • Pelvic organ prolapse
  • Mechanical testing