Methods for the defining mechanisms of anterior vaginal wall descent (DEMAND) study

Variations in structural support site failure patterns by prolapse size on stress 3D MRI

INTRODUCTION AND HYPOTHESIS

Our objective was to develop a standardized measurement system to evaluate structural support site failures among women with anterior vaginal wall-predominant prolapse according to increasing prolapse size using stress three-dimensional (3D) magnetic resonance imaging (MRI).

METHODS

Ninety-one women with anterior vaginal wall-predominant prolapse and uterus in situ who had undergone research stress 3D MRI were included for analysis. The vaginal wall length and width, apex and paravaginal locations, urogenital hiatus diameter, and prolapse size were measured at maximal Valsalva on MRI. Subject measurements were compared to established measurements in 30 normal controls without prolapse using a standardized z-score measurement system. A z-score greater than 1.28, or the 90th percentile in controls, was considered abnormal. The frequency and severity of structural support site failure was analyzed based on tertiles of prolapse size.

RESULTS

Substantial variability in support site failure pattern and severity was identified, even between women with the same stage and similar size prolapse. Overall, the most common failed support sites were straining hiatal diameter (91%) and paravaginal location (92%), followed by apical location (82%). Impairment severity z-score was highest for hiatal diameter (3.56) and lowest for vaginal width (1.40). An increase in impairment severity z-score was observed with increasing prolapse size among all support sites across all three prolapse size tertiles (p < 0.01 for all).

CONCLUSIONS

We identified substantial variation in support site failure patterns among women with different degrees of anterior vaginal wall prolapse using a novel standardized framework that quantifies the number, severity, and location of structural support site failures.

Defining mechanisms of recurrence following apical prolapse repair based on imaging criteria

BACKGROUND

Prolapse recurrence after transvaginal surgical repair is common; however, its mechanisms are ill-defined. A thorough understanding of how and why prolapse repairs fail is needed to address their high rate of anatomic recurrence and to develop novel therapies to overcome defined deficiencies.

OBJECTIVE

This study aimed to identify mechanisms and contributors of anatomic recurrence after vaginal hysterectomy with uterosacral ligament suspension (native tissue repair) vs transvaginal mesh (VM) hysteropexy surgery for uterovaginal prolapse.

STUDY DESIGN

This multicenter study was conducted in a subset of participants in a randomized clinical trial by the Eunice Kennedy Shriver National Institute of Child Health and Human Development Pelvic Floor Disorders Network. Overall, 94 women with uterovaginal prolapse treated via native tissue repair (n=48) or VM hysteropexy (n=46) underwent pelvic magnetic resonance imaging at rest, maximal strain, and poststrain rest (recovery) 30 to 42 months after surgery. Participants who desired reoperation before 30 to 42 months were imaged earlier to assess the impact of the index surgery. Using a novel 3-dimensional pelvic coordinate system, coregistered midsagittal images were obtained to assess study outcomes. Magnetic resonance imaging-based anatomic recurrence (failure) was defined as prolapse beyond the hymen. The primary outcome was the mechanism of failure (apical descent vs anterior vaginal wall elongation), including the frequency and site of failure. Secondary outcomes included displacement of the vaginal apex and perineal body and change in the length of the anterior wall, posterior wall, vaginal perimeter, and introitus of the vagina from rest to strain and rest to recovery. Group differences in the mechanism, frequency, and site of failure were assessed using the Fisher exact tests, and secondary outcomes were compared using Wilcoxon rank-sum tests.

RESULTS

Of the 88 participants analyzed, 37 (42%) had recurrent prolapse (VM hysteropexy, 13 of 45 [29%]; native tissue repair, 24 of 43 [56%]). The most common site of failure was the anterior compartment (VM hysteropexy, 38%; native tissue repair, 92%). The primary mechanism of recurrence was apical descent (VM hysteropexy, 85%; native tissue repair, 67%). From rest to strain, failures (vs successes) had greater inferior displacement of the vaginal apex (difference, -12 mm; 95% confidence interval, -19 to -6) and perineal body (difference, -7 mm; 95% confidence interval, -11 to -4) and elongation of the anterior vaginal wall (difference, 12 mm; 95% confidence interval, 8-16) and vaginal introitus (difference, 11 mm; 95% confidence interval, 7-15).

CONCLUSION

The primary mechanism of prolapse recurrence following vaginal hysterectomy with uterosacral ligament suspension or VM hysteropexy was apical descent. In addition, greater inferior descent of the vaginal apex and perineal body, lengthening of the anterior vaginal wall, and increased size of the vaginal introitus with strain were associated with anatomic failure. Further studies are needed to provide additional insight into the mechanism by which these factors contribute to anatomic failure.

The establishment of a 3D anatomical coordinate system for defining vaginal axis and spatial position

BACKGROUND AND OBJECTIVE

Pelvic organ prolapse (POP), the herniation of the pelvic organs toward the vaginal opening, is a common pelvic floor disorder (PFD) whose etiology is poorly understood. Traditional methods for evaluating POP are often constrained to external vaginal examination, limited to 2D, or have poor reproducibility. We propose a reliable 3D anatomic coordinate system for standardized 3D assessment of pelvic anatomy using magnetic resonance imaging (MRI).

METHODS

The novel 3D anatomic reference system is based on six bony landmarks of the pelvis manually identified in MRI: the ischial spines and the superior and inferior pubic points of the left and right pubic symphysis. The origin of this system is defined as the midpoint of the ischial spines. The reproducibility and applicability of the pelvic coordinate system were evaluated by (1) implementing it in a new method to quantify vaginal position and axis (angulation) in 3D space from MRI segmentations of the vagina and (2) computing the intraclass correlation (ICC) on coordinate system and vaginal measures. The MRI analysis was performed by four non-medically trained observers on five pelvic MRI datasets on approximately five separate occasions.

RESULTS

Overall, all bony landmarks had excellent intra-observer reliability and inter-observer reliability (ICC>0.90); intra-observer reliability was moderate-to-good among the vaginal position parameters (0.5<ICC≤0.90) and moderate for the vaginal axis angles (0.50<ICC≤0.75); inter-observer reliability was moderate in the vaginal position coordinates and vaginal axis measures. On average, within-observer differences in the vaginal position and angle measures relative to the overall mean were <1 mm and <1°, respectively.

CONCLUSIONS

The proposed anatomic coordinate system and vaginal analysis approach allow quantitative assessment of pelvic anatomy that is robust to the experience level of the observer. The application of these methods in radiographic studies will give new insight into the underlying anatomic changes involved in the pathogenesis of POP and other PFDs and help better understand their etiology.