Correlation between vaginal stiffness index and pelvic floor disorder quality-of-life scales

Non-invasive biomechanical assessment of the prolapsed vaginal wall: an explorative pilot study on cutometry and indentometry

The clinical assessment of pelvic organ prolapse (POP) and associated treatment strategies is currently limited to anatomical and subjective outcome measures, which have limited reproducibility and do not include functional properties of vaginal tissue. The objective of our study was to evaluate the feasibility of using cutometry and indentometry for non-invasive biomechanical assessment of the vaginal wall in women with POP. Both techniques were applied on the vaginal wall of 20 women indicated for surgical correction of POP stage two or higher. The primary outcome was the measurement success rate. Measurements were considered successful if biomechanical parameters were generated after a maximum of three attempts. Secondary outcomes included acquisition time, number of attempts to obtain a successful measurement, and biomechanical parameters. Measurements were successfully performed on the anterior vaginal wall of 12 women with cystocele and the posterior vaginal wall of eight women with rectocele. The success rate was 100% for both techniques and acquisition time was under 1 minute for all 20 measurements. Tissue fast elasticity of the posterior vaginal wall (rectocele) was significantly higher than that of the anterior vaginal wall (cystocele) and negatively correlated with age (r = - 0.57, P < 0.05). In women with POP, measuring the biomechanical properties of the vaginal wall using cutometry and indentometry is technically feasible. Objective evaluation of biomechanical properties may help to understand the pathophysiology behind surgical outcomes, providing an opportunity for the identification of patients at risk for (recurrent) prolapse, and individualized treatment decisions.

Design, inverted vat photopolymerization 3D printing, and initial characterization of a miniature force sensor for localized in vivo tissue measurements

Background

Tissue healthiness could be assessed by evaluating its viscoelastic properties through localized contact reaction force measurements to obtain quantitative time history information. To evaluate these properties for hard to reach and confined areas of the human body, miniature force sensors with size constraints and appropriate load capabilities are needed. This research article reports on the design, fabrication, integration, characterization, and in vivo experimentation of a uniaxial miniature force sensor on a human forearm.

Methods

The strain gauge based sensor components were designed to meet dimensional constraints (diameter ≤3.5mm), safety factor (≥3) and performance specifications (maximum applied load, resolution, sensitivity, and accuracy). The sensing element was fabricated using traditional machining. Inverted vat photopolymerization technology was used to prototype complex components on a Form3 printer; micro-component orientation for fabrication challenges were overcome through experimentation. The sensor performance was characterized using dead weights and a LabVIEW based custom developed data acquisition system. The operational performance was evaluated by in vivo measurements on a human forearm; the relaxation data were used to calculate the Voigt model viscoelastic coefficient.

Results

The three dimensional (3D) printed components exhibited good dimensional accuracy (maximum deviation of 183μm). The assembled sensor exhibited linear behavior (regression coefficient of R²=0.999) and met desired performance specifications of 3.4 safety factor, 1.2N load capacity, 18mN resolution, and 3.13% accuracy. The in vivo experimentally obtained relaxation data were analyzed using the Voigt model yielding a viscoelastic coefficient τ=12.38sec and a curve-fit regression coefficient of R²=0.992.

Conclusions

This research presented the successful design, use of 3D printing for component fabrication, integration, characterization, and analysis of initial in vivo collected measurements with excellent performance for a miniature force sensor for the assessment of tissue viscoelastic properties. Through this research certain limitations were identified, however the initial sensor performance was promising and encouraging to continue the work to improve the sensor. This micro-force sensor could be used to obtain tissue quantitative data to assess tissue healthiness for medical care over extended time periods.

An operator-independent artificial finger can differentiate anterior vaginal wall indentation parameters between control and prolapse patients

In this study, the reproducibility and validity of an automated artificial finger for evaluating properties of vaginal wall tissue was assessed. The effect of angle and rate of indentation on displacing the anterior vaginal wall (AVW) was studied in control and prolapse patients. Following IRB approval, an automated artificial finger equipped with a calibrated piezoresistive sensor at its tip was used to induce 3-second AVW deformation sequences (10°, 15°, and 20° indentation). Measurements were taken in patients in supine position, either awake in clinic or under anesthesia in the operating room (OR). The real time voltage output of a sensor (linearly proportional to the reaction force) was recorded for each motion profile to calculate key parameters: baseline voltages, amplitude changes over indentation intervals, and slopes of indentation curves. 23 women (9 controls and 14 prolapse) were studied, 6 in clinic and 17 in OR. No differences in mean reproducibility was noted across groups. There was a significant difference in sensor output based on selected motion profile parameters between different degrees of indentation for all women (p < 0.001) and in baseline voltage between age-matched and non-age-matched controls (p < 0.02). From these findings, we can conclude that indentation reaction properties of prolapsed and non-prolapsed AVW can be objectively measured using an operator-independent artificial finger with significant differences between patient groups.

Anisotropy of the Passive and Active Rat Vagina Under Biaxial Loading

Pelvic organ prolapse, the descent of the pelvic organs from their normal anatomical position, is a common condition among women that is associated with mechanical alterations of the vaginal wall. In order to characterize the complex mechanical behavior of the vagina, we performed planar biaxial tests of vaginal specimens in both the passive (relaxed) and active (contracted) states. Specimens were isolated from virgin, female Long-Evans rats (n = 16) and simultaneously stretched along the longitudinal direction (LD) and circumferential direction (CD) of the vagina. Tissue contraction was induced by electric field stimulation (EFS) at incrementally increasing values of stretch and, subsequently, by KCl. On average, the vagina was stiffer in the CD than in the LD (p < 0.001). The mean maximum EFS-induced active stress was significantly higher in the CD than in the LD (p < 0.01). On the contrary, the mean KCl-induced active stress was lower in the CD than in the LD (p < 0.01). When comparing the mean maximum EFS-induced active stress to the mean KCl-induced active stress, no differences were found in the CD (p = 0.366) but, in the LD, the mean active stress was much higher in response to the KCl stimulation (p < 0.001). Collectively, these results suggest that the anisotropic behavior of the vaginal tissue is determined not only by collagen and smooth muscle fiber organization but also by the innervation.

Biomechanical properties of vaginal tissue in women with pelvic organ prolapse

BACKGROUND/AIMS

To compare biomechanical properties of vaginal tissues between women with and without pelvic organ prolapse (POP) and investigate factors that may influence these properties.

METHODS

Forty patients submitted to POP surgery and 15 non-POP cadavers were evaluated. The tissue was excised from anterior and posterior middle third vagina. The biomechanical properties considered were stiffness (E) and maximum stress (S), and they were evaluated by means of uniaxial tension tests.

RESULTS

POP patients were associated with higher values of E (13.1 ± 0.8 vs. 9.5 ± 0.7 MPa; p < 0.001) and S (5.3 ± 0.5 vs. 3.2 ± 0.9 MPa; p < 0.001) in the anterior vaginal wall compared to the posterior wall. In contrast, non-POP women presented lower values of E (6.9 ± 1.1 vs. 10.5 ± 1.0 MPa; p = 0.01) and S (2.6 ± 0.4 vs. 3.5 ± 0.4 MPa; p = 0.043) in the anterior wall. The occurrence of POP was the only independent predictor of higher values of E and S in anterior vaginal samples (p = 0.003 and p = 0.008, respectively). Women with severe anterior vaginal prolapse presented higher levels of E and S in the anterior sample compared to those with lower POP stages (p = 0.001 and p = 0.01; respectively).

CONCLUSION

Women with POP present significant changes of biomechanical properties in the vagina.

Strength of round and uterosacral ligaments: a biomechanical study

PURPOSE

To investigate the tensile biomechanical properties of round and uterosacral ligaments.

METHODS

Tissue samples were obtained from 15 female cadavers without pelvic organ prolapse. Uniaxial tensile tests were performed to obtain stiffness and maximum stress of round and uterosacral ligaments. Correlations were calculated using the Pearson correlation coefficient. Statistical differences between groups were tested using Student's paired and unpaired t test.

RESULTS

There was a great variability in the measurements of stiffness and maximum stress in pelvic ligaments. The round ligaments demonstrated stiffness of 9.1 ± 1.6 MPa (mean ± SEM) (ranging from 2 to 25.6 MPa) and maximum stress of 4.3 ± 0.7 MPa (ranging from 1.2 to 11.5 MPa). The stiffness of the uterosacral ligaments was 14.1 ± 1.4 MPa (ranging from 5.7 to 26.1 MPa) with maximum stress of 6.3 ± 0.8 MPa (ranging from 2.2 to 11.9 MPa). There was a strong positive correlation between stiffness and maximum stress in female pelvic ligaments (ρ = 0.851; p < 0.001). The uterosacral ligaments demonstrated higher stiffness and maximum stress compared to the round ligaments (p = 0.006 and p = 0.034; respectively). Age, body mass index and menopausal status were not associated with the biomechanical proprieties of round and uterosacral ligaments. Nulliparous women had lower uterosacral stiffness (15.5 ± 1.3 vs. 10 ± 1.8 MPa; p = 0.033) and maximum stress (8.2 ± 0.9 vs. 4.2 ± 1.1 MPa; p = 0.028) compared to parous women.

CONCLUSION

The uterosacral ligaments are significantly more resistant than round ligaments. Parturition seems to enhance the stiffness and maximum stress of the ligaments.

Impact of sacral colpopexy on in vivo vaginal biomechanical properties

OBJECTIVE

The purpose of this study was to determine if sacral colpopexy has an impact on in vivo vaginal biomechanical properties.

STUDY DESIGN

Thirty-five participants who underwent sacral colpopexy were enrolled in this prospective clinical trial. In vivo vaginal biomechanical properties, including elasticity, viscoelasticity, and vaginal stiffness index, as well as symptom severity questionnaires (pelvic floor distress inventory-short form) and Pelvic Organ Prolapse Quantification (POP-Q) examination, were performed preoperatively and 6 weeks postoperatively.

RESULTS

Thirty-two participants completed the study. Six weeks after sacral colpopexy participants demonstrated a decrease in prolapse related symptoms (POPDI-6 score, 39.8 vs 9.0, P < .00001) and 97% demonstrated anatomical cure of their prolapse. At 6 weeks follow-up participants demonstrated an increase in elasticity (2.26 vs 3.43, P < .00001), viscoelasticity (1.55 vs 4.08, P < .000001), and vaginal stiffness index (108.65 vs 164.50, P < .01).

CONCLUSION

These findings suggest that sacral colpopexy increases in vivo vaginal biomechanical properties, as well as decreasing anatomical and symptom-related severity of pelvic organ prolapse.

Depression and heart disease: therapeutic implications

The consequences of depression and coronary artery disease (CAD) were reviewed in the literature. The comorbidity of depression and CAD results in an increased cardiovascular mortality. We reviewed possible explanations for this increased morbidity, which include: toxicity of tricyclic antidepressants that can cause cardiac arrhythmias, abnormalities in platelet function leading to increased platelet aggregation due to abnormalities in serotonin in the platelet (an abnormality that possibly causes depression in the central nervous system), diffuse atherosclerosis causing central nervous system abnormalities including depression (vascular depression), as well as the possibility that depressed patients are less compliant with their medications and physician-directed health recommendations. Recent reports of selective serotonin reuptake inhibitors (SSRIs) causing a reduced cardiovascular mortality may be related to serotonin platelet abnormalities in depressed patients that are effectively treated by SSRIs (SADHART and ENRICHD trial). It is possible that these trials reveal a mechanism of depression that also effects platelet function and can be improved with SSRI therapy, suggesting a preferential therapeutic pathway for the treatment of depressed patients with CAD.