Citation: Appelbaum, A.H.; Tirandaz, M.; Ricci, G.; Levi D’Ancona, R. Alignment of the Cervix with the Vagina in Uterine Retroversion: A Possible Risk Factor in Uterine Prolapse. Diagnostics 2022, 12, 1428. https://doi.org/10.3390/ diagnostics12061428 Academic Editor: Manuela Ludovisi Received: 12 May 2022 Accepted: 6 June 2022 Published: 9 June 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). diagnostics Article Alignment of the Cervix with the Vagina in Uterine Retroversion: A Possible Risk Factor in Uterine Prolapse Alan H. Appelbaum 1, *, Mehran Tirandaz 1,2 , Giuseppe Ricci 3,4 and Roberto Levi D’Ancona 5 1 Memphis Veterans Affairs Medical Center, 1030 Jefferson Avenue, Memphis, TN 38104, USA; mehran.tirandaz@va.gov 2 University of Tennessee Health Science Center, Memphis, TN 38163, USA 3 Institute for Maternal and Child Health, IRCCS Burlo Garofolo, 34137 Trieste, Italy; giuseppe.ricci@burlo.trieste.it 4 Department of Medicine, Surgery and Health Sciences, University of Trieste, 34127 Trieste, Italy 5 Southern Illinois University School of Medicine, Springfield, IL 62702, USA; rlevi-dancona52@siumed.edu * Correspondence: alan.appelbaum@va.gov; Tel.: +1-757-641-7771; Fax: +1-901-754-5979 Abstract: Multiple observational studies have found an association of uterine prolapse with uterine retroversion. Mechanisms proposed to explain this apparent association assume that the cervix of a retroverted uterus will usually insert at the apex of the vagina, with resultant alignment of the cervix with the vagina. The angle of the axis of the cervix with the axis of the vagina was measured by two readers on 323 sagittal pelvic MRI scans and sagittal reconstructions of pelvic CT scans performed for clinical purposes. One reader observed and recorded the anatomic relations of the uterus that differed by insertion site and version: 44 of 49 retroverted uteri (89.8%) inserted at the vaginal apex, and 13 of 274 anteverted uteri (4.7%) inserted at the vaginal apex. This difference was found to be statistically significant (p < 0.05) by the Chi square test. The urinary bladder, vaginal walls, and rectum were inferiorly related to anteriorly inserted anteverted uteri. Only the vaginal lumen and the rectum at a shallow oblique angle were inferiorly related to apically inserted retroverted uteri. Most retroverted uteri insert at the apex of the vagina. Apically inserted retroverted uteri appear to receive less support from adjacent structures than anteriorly inserted anteverted uteri. Keywords: pelvic anatomy; pelvic floor; prolapse; retroversion; uterus; vagina 1. Purpose Two recent observational studies demonstrated a possible association of uterine pro- lapse with uterine retroversion [1,2]. There are similar studies showing this possible association dating back to the first half of the twentieth century [3,4]. We have found three proposed mechanisms to explain this apparent association. All three assume that the cervix of a retroverted uterus will usually insert at the apex of the vagina, with resultant alignment of the axis of the uterus with the axis of the vagina. One mechanism proposes that this alignment of the uterus with the vagina would allow the uterus to descend and ascend within the vagina with increases and decreases in intra-abdominal pressure. This piston-like action would create mechanical stress on the supporting structures of the uterus, leading to uterine prolapse and other pelvic floor dysfunctions [1,5]. A second mechanism proposes that the alignment of the uterus with the vagina in retroversion would ease passage of the uterus through the vagina when there is widening of the urogenital hiatus and other damage to the supporting structures of the uterus [6,7]. The third mechanism proposes that weakness of the uterosacral ligament allows the uterus to rotate posteriorly, allowing alignment of the uterus with the vagina. This rotation would twist and stress the transverse cervical ligaments, leading to prolapse [8]. Cross-sectional imaging has been successfully used to study the anatomy of the vagina, uterus, and related structures. For example, studies using MRI have been used Diagnostics 2022, 12, 1428. https://doi.org/10.3390/diagnostics12061428 https://www.mdpi.com/journal/diagnostics