• The ability to measure the changes in complex geometry in real time should aid efforts to develop strategies to prevent pelvic floor injury.

• Limitations• Modest number of subjects participated• Rate of stretch ratio was not quantified.• Measurement resolution remains to be improved.• Post-processing of the measurement was required.

• Method allows objective documentation of the dynamic, multi-dimensional changes of the perineal surface during the 2nd-stage of labor.

Time Course of Diametric Changes (Fig. x)• Major change concentrated in the final pushing phase• Diametric changes and the pushing pattern are in phase

Surface Deformation (Fig. x)• The deformation during the final push is up to twice that of

earlier pushes in the 2nd-stage of labor• Principal stretches are concentrically distributed• Helpful in differentiating local stretch magnitude and direction• Spatial resolution of the measurement was adequateDevice design

• A pre-calibrated pair of webcams connected to a laptop• No external power required• Hospital electrical safety inspection passed• Recording and analyzing software written in C++ (OpenCV library) and

Matlab, respectively.

Intrapartum measurement• University of Michigan IRB approval obtained• Two primiparous women (20 & 32 yo)• Recorded during the entire 2nd-stage• Device located at the foot of the bed• Ink-dotted markers placed on the perineum and vulva

Types of measurement• Anterior-posterior (AP) and lateral (LA) diameters of the vaginal opening• Perineal surface deformation - Principal stretch magnitude and direction

• Present a novel intrapartum measurement system which features objective yet accurate measurements based on computer vision technology.

• Document the details of the movement of the perineal surface deformation during late 2nd-stage of labor.

• Vaginal delivery is the single modifiable risk factor for the levator ani muscle (LA) injury, and then pelvic organ prolapse and urinary incontinence later in lives. (Dietz and Lanzarone, 2005; Kearney et al., 2006)

• However, objective real-time measurements of the pelvic floor deformation during the late 2nd-stage of labor are lacking.

• The specific factors and cascade of events that lead to the LA injury are still unknown.

• Direct verification of biomechanical computer simulations is not possible, so indirect methods are indicated.

Highlight and replace this text with your own titleThree-Dimensional Measurement of the Stretch and Displacement of the Perineum during Labor using Stereophotogrammetry

1Jinyong Kim, MS, 2Lisa Kane Low,PhD, CNM, FACNM, 3John O. L. DeLancey, MD, and 1James A. Ashton-Miller, PhD1Department of Mechanical Engineering, 2School of Nursing, 3Department of Obstetrics & Gynecology, University of Michigan, Ann Arbor, Michigan, USA

Acknowledgements: NIH Grants P50 HD044406, UL1RR024986

Introduction

Aims

Methods

Conclusions

Discussion

2012 AUGS Annual Scientific Meeting

Results

Email: jinyongk@umich.edu, kanelow@umich.edu, delancey@umich.edu, jaam@umich.edu

(a) Prior to recording, ink-based markers were placed on the perineum (indicated here with yellow dots). Antero-posterior (AP) and lateral (LA) diameters were defined as distances of the four points around the vaginal opening. (b) Triangular meshes from undeformed configuration at the beginning of the 2nd-stage (solid line) and deformed configuration during a push (dash line), are used to calculate the magnitude and direction of the most domi-nant components of the deformation (red arrow, often referred to as the principal stretch and direction). (c) Temporal changes in AP and LA diameters (top) and principal stretches of the four tri-angularly meshed regions on the perineum (bottom) during the final ten minutes (Min) of the 2nd-stage of labor. Six pushing ef-forts (vertical lines) were observed from this particular subject during this recording period.

The graphic user interface of the post-processing software. Two views from each of the cameras were provided along with other information regard-ing the three-dimensional coordinates of the mark-ers, diameters, amount of perineal descent, and principal stretches/spatial directions.

Picture of the measurement system, which consists of a webcam assembly connected to a laptop.

Directions of principal stretch are superimposed on the triangular mesh during final push. The directions are concentric to the vaginal opening.