Viscoelastic properties measurement of the prolapsed anterior vaginal wall: a patient-directed methodology

A feasibility study of three-dimensional ultrasound imaging of the vagina under distension

BACKGROUND

The distension properties of the vagina are critical to its function including support of surrounding organs, childbirth, and intercourse. It could be altered by many pathophysiological processes like pregnancy, radiotherapy, and reconstruction surgery. However, there are no clinically available diagnostic tools capable of quantifying the distension properties of the vagina.

PURPOSE

A proof-of-concept study was designed to assess the feasibility of a novel three-dimensional (3D) ultrasound imaging technique that allows quantitative evaluation of the vagina under distension.

METHODS

Patients with symptomatic pelvic organ prolapse (POP) were recruited for the study. An ultrathin, oversized bag was inserted into the vagina and filled with water using a modified urodynamics system. The instilled water volume and intravaginal pressure were continuously recorded. At maximum vaginal capacity, 3D transintroital ultrasound of the distended vagina and surrounding pelvic structures was performed. Exams were performed in duplicate for each patient, two hours apart (round A and round B). Following the development of a 3D surface model of the distended vagina from each scan, several measurements were obtained, including cross-sectional area, anteroposterior (AP) length and lateral width in the plane of minimum hiatal dimensions (PMHD), AP and lateral diameter at the pubic symphysis (PS) level, maximum and minimum diameter, and maximum vertical length. To assess repeatability between measurements in two rounds, the coefficient of variation (CV) and the intraclass correlation coefficient (ICC) were calculated for each measurement. Correlations between physical measurements including the pelvic organ prolapse quantification (POP-Q) system and vaginal diameter measurements, and obtained metrics were also assessed.

RESULTS

Sixteen patients with POP (average age 69 years) completed both rounds of imaging. There was sufficient echogenicity on 3D transintroital ultrasound of the distended vaginal wall to establish boundaries for 3D surface models of the vagina. Overall, all metrics had good or excellent reliability (ICC = 0.77-0.93, p < 0.05; CV = 3%-18%) except maximum diameter, which demonstrated only moderate reliability (ICC = 0.67, p = 0.092). Strong correlations were found between physical exam measurements including D point of POP-Q, introitus diameter and lateral diameter at apex, and maximum vaginal capacity, maximum vertical length, lateral diameter at PS, minimum diameter, and distended PMHD measurements. The results demonstrated that this system could generate 3D models of the shape of the distended vagina and provide multiple metrics that could be reliably calculated from automated analyses of the models.

CONCLUSIONS

A novel system for evaluation of the distension properties of the vagina was developed and preliminary evaluation was performed. This system may represent a technique for evaluation of the biomechanical and structural properties of the vagina.

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.

A Randomized, Placebo-Controlled Trial Evaluating the Single and Combined Efficacy of Radiofrequency and Hybrid Fractional Laser for Nonsurgical Aesthetic Genital Procedures in Post-Menopausal Women

BACKGROUND

The efficacy of interventions that provide long-term relief of genitourinary symptoms of menopause has not been determined.

OBJECTIVES

The authors sought to evaluate radiofrequency and hybrid fractional laser (HFL) treatments for menopausal vulvovaginal symptoms.

METHODS

Thirty-one postmenopausal women completed all treatments and at least 1 follow-up. Outcomes included the Vulvovaginal Symptom Questionnaire (VSQ), Vaginal Laxity Questionnaire (VLQ), Urogenital Distress Short Form, Incontinence Impact Questionnaire (IIQ), Female Sexual Function Index (FSFI), laxity measurements via a vaginal biometric analyzer probe, and gene expression studies.

RESULTS

Mean VSQ score decreased 2.93 (P = 0.0162), 4.07 (P = 0.0035), and 4.78 (P = 0.0089) among placebo, dual, and HFL groups 3 months posttreatment and decreased to 3.3 (P = 0.0215) for dual patients at 6 months. FSFI scores increased in the desire domain for placebo and dual groups and in arousal, lubrication, orgasm, satisfaction, and pain domains for the HFL group 3 and 6 months posttreatment. An increase of 1.14 in VLQ score (P = 0.0294) was noted 3 months and 2.2 (P = 0.002) 6 months following dual treatment. There was also a mean decrease of 15.3 (P = 0.0069) in IIQ score for HFL patients at 3 months. Dual, HFL, and RF treatments resulted in statistically significant decreases in collagen I, elastin, and lysyl oxidase expression.

CONCLUSIONS

Several self-reported improvements were noted, particularly among HFL, dual, and placebo groups 3 and 6 months posttreatment. Objective biopsy analysis illustrated decreased gene expression, suggesting that treatments did not stimulate new extracellular matrix production.

LEVEL OF EVIDENCE: 2

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.

Investigation of Murine Vaginal Creep Response to Altered Mechanical Loads

The vagina is a viscoelastic fibromuscular organ that provides support to the pelvic organs. The viscoelastic properties of the vagina are understudied but may be critical for pelvic stability. Most studies evaluate vaginal viscoelasticity under a single uniaxial load; however, the vagina is subjected to dynamic multiaxial loading in the body. It is unknown how varied multiaxial loading conditions affect vaginal viscoelastic behavior and which microstructural processes dictate the viscoelastic response. Therefore, the objective was to develop methods using extension-inflation protocols to quantify vaginal viscoelastic creep under various circumferential and axial loads. Then, the protocol was applied to quantify vaginal creep and collagen microstructure in the fibulin-5 wildtype and haploinsufficient vaginas. To evaluate pressure-dependent creep, the fibulin-5 wildtype and haploinsufficient vaginas (n = 7/genotype) were subjected to various constant pressures at the physiologic length for 100 s. For axial length-dependent creep, the vaginas (n = 7/genotype) were extended to various fixed axial lengths then subjected to the mean in vivo pressure for 100 s. Second-harmonic generation imaging was performed to quantify collagen fiber organization and undulation (n = 3/genotype). Increased pressure significantly increased creep strain in the wildtype, but not the haploinsufficient vagina. The axial length did not significantly affect the creep rate or strain in both genotypes. Collagen undulation varied through the depth of the subepithelium but not between genotypes. These findings suggest that the creep response to loading may vary with biological processes and pathologies, therefore, evaluating vaginal creep under various circumferential loads may be important to understand vaginal function.

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.

Efficacy of injecting platelet concentrate combined with hyaluronic acid for the treatment of vulvovaginal atrophy in postmenopausal women with history of breast cancer: a phase 2 pilot study

OBJECTIVE

Approximately 50% to 70% of breast cancer survivors are affected by one or more symptoms of vulvovaginal atrophy (VVA). For those who cannot take hormone therapy, autologous platelet-rich plasma combined with hyaluronic acid (A-PRP-HA) may provide a new alternative therapy for the treatment of VVA in postmenopausal women with history of breast cancer.

METHODS

We enrolled 20 postmenopausal breast cancers survivors with VVA and a score of <15 on the Gloria Bachman Vaginal Health Index (VHI) comprised of five items including: vaginal pH, elasticity, fluid volume (secretions), epithelial integrity, and moisture.We administered intramucosal injections of A-PRP combined with HA (Regenkit) and performed clinical evaluations at 0, 1, 3, and 6 months. Primary endpoint: evaluation of vulvovaginal mucosa changes using the VHI; secondary endpoint: evaluation of dyspareunia and sexual dysfunction based on the Female Sexual Distress (FSD) score.

RESULTS

All participants (20 women) showed improvement in the clinical symptoms of vaginal dryness and dyspareunia. The VHI score showed a significant increase at 6 months, going from a total baseline score (pretreatment) of 10.7 ± 2.12 to 20.75 ± 4.8 (P < 0.0001) at 6 months. Improvement in hydration and vaginal epithelial integrity was reported. A VHI score of > 15 showed a successful treatment outcome. The FSD score decreased significantly during the study, from a baseline score of 36.35 ± 2.53 pretreatment to 30.15 ± 2.47 6 months after treatment, representing improvement of 17% (P < 0.0001, respectively). No adverse events were reported.

CONCLUSIONS

The injection of A-PRP-HA appeared to be a promising method to improve the trophicity and hydration of vaginal mucosa for the treatment of VVA in postmenopausal breast cancer survivors with contraindications to hormone therapy.

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.