Elasticity of the Cervix in Relation to Uterus Position

Abstract

Strain elastography allows the evaluation of tissue elasticity. Background/Objectives: Tissue elasticity depends on the content and distribution of collagen fibers and is shaped by the applied tensile forces that may differ in uteri with a different angle of flexion of the corpus on the cervix. The objective was to investigate whether the angle of uterine flexion is related to cervical tissue elasticity. Methods: The anterior angle between the longitudinal axis of the uterus corpus and that of the cervix was measured in 275 non-pregnant young women by transvaginal ultrasonography and considered both as an absolute value or categorized as ≤150°, between >150° and ≤210°, and >210°. Strain elastography was used to assess tissue elasticity by placing the probe in the anterior vaginal fornix. Tissue elasticity was evaluated in the middle of the anterior cervical compartment (ACC), in the middle of the posterior cervical compartment (PCC), in the middle portion of the cervical canal (MCC), and at the internal cervical os (ICO). In a sagittal plane MCC was evaluated across the cervical canal, and ACC and PCC at a distance equal between the cervical canal and the outer anterior or posterior part of the cervix. MCC, ACC and PCC were evaluated at equal distance between the ICO and the external cervical os. Elasticity was expressed as a color score ranging from 0.1 (low elasticity) to 3 (high elasticity). Results: The angle of uterine flexion show a negative linear relation with the elasticity of the ACC (p = 0.001) and MCC (p = 0.002) and a positive relation with the elasticity of the PCC (p = 0.054). In comparison to uteri with an angle of flexion of <150°, those with an angle of flexion of >210° had lower elasticity of the ACC (p = 0.001) and MCC (p = 0.001) and higher elasticity of the PCC (p = 0.004). The ACC/PCC and PCC/MCC elasticity ratios were also significantly different (p = 0.001). Conclusions: The angle of uterine flexion is associated with changes in cervix elasticity. Retroflexion is associated with stiffer ACC and MCC and a more elastic PCC. Differences in tissue elasticity suggest structural changes of the cervix that may have implication in variate obstetric and gynecological conditions.

Keywords: cervix; cervix structure; elastography; retroflexion; retroversion; stiffness; uterine flexion.

Figure 1

Ultrasonographic image of a retroflexed uterus in a sagittal (a) and transverse scan (b). The interrupted lines indicate uterus measures. L: longitudinal uterus measure; AP: anterior-posterior uterus measure; CAP: cervix antero-posterior diameter; CL: cervix length; ICO: internal cervical os; ECO: external cervical os; Angle: angle of uterine flexion; Probe: ultrasound probe; T: transverse uterus measure.

Figure 2

Elastography image of the cervix of an anteflexed uterus showing a stiffer posterior than anterior (cervical compartment stiffer (blue) than an anterior (cyan/green) cervical compartment. Probe: transvaginal elastography probe; ICO: internal cervical os; ACC: anterior cervical compartment; MCC: middle cervical canal; PCC: posterior cervical compartment; ECO: external cervical os.

Figure 3

Mean (SD) values of tissue elasticity of the anterior cervical compartment (ACC), posterior cervical compartment (PCC), middle cervical canal compartment (MCC), internal cervical os (ICO), and their elasticity ratio, observed in uteri with an angle of flexion ≤150° or >210° * p = 0.004; ** p = 0.001.

Figure 4

Schematic representation of the elasticity of different cervical areas observed in anteflexed (left) and retroflexed (right) uteri. ACC: anterior cervical compartment; PCC: posterior cervical compartment; MCC: middle cervical canal compartment; ICO: internal cervical os. Elasticity increases with the intensity from blue up to pink.