Dimensional analysis of the endometrial cavity: how many dimensions should the ideal intrauterine device or system have?

Abstract

BackgroundThe geometrical shape of the human uterus most closely approximates that of a prolate ellipsoid. The endometrial cavity itself is more likely to also have the shape of a prolate ellipsoid especially when the extension of the cervix is omitted. Using this information and known endometrial cavity volumes and lateral and vertical dimensions, it is possible to calculate the anteroposterior (AP) dimensions and get a complete evaluation of all possible dimensions of the endometrial cavity. These are singular observations and not part of any other study.MethodsThe AP dimensions of the endometrial cavity of the uterus were calculated using the formula for the volume of the prolate ellipsoid to complete a three-dimensional picture of the endometrial cavity.ResultsCalculations confirm ultrasound imaging which shows large variations in cavity size and shape. Known cavity volumes and length and breadth measurements indicate that the AP diameter may vary from 6.29 to 38.2 mm. These measurements confirm the difficulty of getting a fixed-frame intrauterine device (IUD) to accommodate to a space of highly variable dimensions. This is especially true of three-dimension IUDs. A one-dimensional frameless IUD is most likely to be able to conform to this highly variable space and shape.ConclusionThe endometrial cavity may assume many varied prolate ellipsoid configurations where one or more measurements may be too small to accommodate standard IUDs. A one-dimensional device is most likely to be able to be accommodated by most uterine cavities as compared to two- and three-dimensional devices.

Three-dimensional measurement and analysis of morphological parameters of the uterus in infertile women

“…Currently, research on the ECA is scarce. Goldstuck obtained the ECV using 3D US and then studied the ECA (range, 6.29 to 38.2 mm), which was derived from the ellipsoid formula (6). As stated above, the endometrial cavity does not exhibit a regular ellipsoid shape.…”

“…To date, few authors have reported measurements of endometrial cavity anteroposterior diameter (ECA). Goldstuck studied the ECA, which was derived from the ellipsoid formula (6); however, the results of their study were not exact, because the shape of the uterine cavity is not an ellipse. The endometrium is central to female reproductive physiology (7).…”

Expulsion of a Spontaneously Broken Arm of a T- Shaped IUD: a Case Report

“…The absence of a frame is particularly advantageous in these women. Frameless IUD, contains a very small copper, is smaller than any other IUD and better tolerated with less effect on the amount of blood loss [10][11][12][13].…”

3D-Printing of Drug-Eluting Implants: An Overview of the Current Developments Described in the Literature

“…Goldstruck et al [ 124 ] described high variability in size and shape of the endometrial cavity. This points out how difficult it is for an IUD to match such highly variable dimensions.…”