Assessment of urethral support using MRI-derived computational modeling of the female pelvis.

INTRODUCTION AND HYPOTHESIS: This study aimed to assess the role of individual anatomical structures and their combinations to urethral support function. METHODS: A realistic pelvic model was developed from an asymptomatic female patient's magnetic resonance (MR) images for dynamic biomechanical analysis using the finite element method. Validation was performed by comparing simulation results with dynamic MR imaging observations. Weaknesses of anatomical support structures were simulated by reducing their material stiffness. Urethral mobility was quantified by examining urethral axis excursion from rest to the final state (intra-abdominal pressure = 100 cmH2O). Seven individual support structures and five of their combinations were studied. RESULT: Among seven urethral support structures, we found that weakening the vaginal walls, puborectalis muscle, and pubococcygeus muscle generated the top three largest urethral excursion angles. A linear relationship was found between urethral axis excursions and intra-abdominal pressure. Weakening all three levator ani components together caused a larger weakening effect than the sum of each individually weakened component, indicating a nonlinearly additive pattern. The pelvic floor responded to different weakening conditions distinctly: weakening the vaginal wall developed urethral mobility through the collapsed vaginal canal, while weakening the levator ani showed a more uniform pelvic floor deformation. CONCLUSIONS: The computational modeling and dynamic biomechanical analysis provides a powerful tool to better understand the dynamics of the female pelvis under pressure events. The vaginal walls, puborectalis, and pubococcygeus are the most important individual structures in providing urethral support. The levator ani muscle group provides urethral support in a well-coordinated way with a nonlinearly additive pattern.

The Single-Incision Sling to Treat Female Stress Urinary Incontinence: A Dynamic Computational Study of Outcomes and Risk Factors.

Dynamic behaviors of the single-incision sling (SIS) to correct urethral hypermobility are investigated via dynamic biomechanical analysis using a computational model of the female pelvis, developed from a female subject's high-resolution magnetic resonance (MR) images. The urethral hypermobility is simulated by weakening the levator ani muscle in the pelvic model. Four positions along the posterior urethra (proximal, midproximal, middle, and mid-distal) were considered for sling implantation. The α-angle, urethral excursion angle, and sling-urethra interaction force generated during Valsalva maneuver were quantitatively characterized to evaluate the effect of the sling implantation position on treatment outcomes and potential complications. Results show concern for overcorrection with a sling implanted at the bladder neck, based on a relatively larger sling-urethra interaction force of 1.77 N at the proximal implantation position (compared with 0.25 N at mid-distal implantation position). A sling implanted at the mid-distal urethral location provided sufficient correction (urethral excursion angle of 23.8 deg after mid-distal sling implantation versus 24.4 deg in the intact case) with minimal risk of overtightening and represents the optimal choice for sling surgery. This study represents the first effort utilizing a comprehensive pelvic model to investigate the performance of an implanted sling to correct urethral hypermobility. The computational modeling approach presented in the study can also be used to advance presurgery planning, sling product design, and to enhance our understanding of various surgical risk factors which are difficult to obtain in clinical practice.

Objective Quantification of Detrusor Overactivity Using Spectral Measures of Cystometry Data.

OBJECTIVE: To develop scalable objective methods for differentiating patients with and without detrusor overactivity (DO) using quantitative Fast Fourier Transform (FFT)-based measures and routinely captured cystometry data. METHODS: Retrospective cystometry data were collected as prevoid vesical and abdominal pressure signals from 18 DO and 10 SUI (non-DO) cystometry recordings. Data were filtered and divided into two equal-duration segments, Early and Late Fill, representing the first and second halves of filling. FFT was applied, followed by subtraction of abdominal spectra from vesical spectra. Spectral Power (SP) and Weighted Average Frequency (WAF) measures were calculated for each segment spectra within 1-6 cycles min-1. RESULTS: Compared to non-DO, the mean SP was significantly higher in DO patients for both Early and Late Fill segments. WAF was significantly lower in DO patients for both segments. Changes in spectral pressures appeared to be linked to the presence of detrusor contractions (DCs) and were especially visible when DCs were present in the Early Fill segments of cystometry. CONCLUSION: FFT-based spectral measures derived from routinely captured cystometry data are significantly different between DO and non-DO patients. This preliminary method is clinically scalable and can be further developed to facilitate the detection of DO, classify disease phenotype, and capture therapeutic efficacy.

Data Gap in Sacral Neuromodulation Documentation: Call to Improve Documentation Protocols.

PURPOSE: We quantified patient record documentation of sacral neuromodulation (SNM) threshold testing and programming parameters at our institution to identify opportunities to improve therapy outcomes and future SNM technologies. METHODS: A retrospective review was conducted using 127 records from 40 SNM patients. Records were screened for SNM documentation including qualitative and quantitative data. The qualitative covered indirect references to threshold testing and the quantitative included efficacy descriptions and device programming used by the patient. Findings were categorized by visit type: percutaneous nerve evaluation (PNE), stage 1 (S1), permanent lead implantation, stage 2 (S2) permanent impulse generator implantation, device-related follow-up, or surgical removal. RESULTS: Documentation of threshold testing was more complete during initial implant visits (PNE and S1), less complete for S2 visits, and infrequent for follow-up clinical visits. Surgical motor thresholds were most often referred to using only qualitative comments such as "good response" (88%, 100% for PNE, S1) and less commonly included quantitative values (68%, 84%), locations of response (84%, 83%) or specific contacts used for testing (0%). S2 motor thresholds were less well documented with qualitative, quantitative, and anatomical location outcomes at 70%, 48%, and 36% respectively. Surgical notes did not include specific stimulation parameters or contacts used for tests. Postoperative sensory tests were often only qualitative (80%, 67% for PNE, S1) with quantitative values documented much less frequently (39%, 9%) and typically lacked sensory locations or electrode-specific results. For follow-up visits, <10% included quantitative sensory test outcomes. Few records (<7%) included device program settings recommended for therapy delivery and none included therapy-use logs. CONCLUSION: While evidence suggests contact and parameter-specific programming can improve SNM therapy outcomes, there is a major gap in the documentation of this data. More detailed testing and documentation could improve therapeutic options for parameter titration and provide design inputs for future technologies.

Pelvic floor dynamics during high-impact athletic activities: A computational modeling study.

BACKGROUND: Stress urinary incontinence is a significant problem in young female athletes, but the pathophysiology remains unclear because of the limited knowledge of the pelvic floor support function and limited capability of currently available assessment tools. The aim of our study is to develop an advanced computer modeling tool to better understand the dynamics of the internal pelvic floor during highly transient athletic activities. METHODS: Apelvic model was developed based on high-resolution MRI scans of a healthy nulliparous young female. A jump-landing process was simulated using realistic boundary conditions captured from jumping experiments. Hypothesized alterations of the function of pelvic floor muscles were simulated by weakening or strengthening the levator ani muscle stiffness at different levels. Intra-abdominal pressures and corresponding deformations of pelvic floor structures were monitored at different levels of weakness or enhancement. FINDINGS: Results show that pelvic floor deformations generated during a jump-landing process differed greatly from those seen in a Valsalva maneuver which is commonly used for diagnosis in clinic. The urethral mobility was only slightly influenced by the alterations of the levator ani muscle stiffness. Implications for risk factors and treatment strategies were also discussed. INTERPRETATION: Results suggest that clinical diagnosis should make allowances for observed differences in pelvic floor deformations between a Valsalva maneuver and a jump-landing process to ensure accuracy. Urethral hypermobility may be a less contributing factor than the intrinsic sphincteric closure system to the incontinence of young female athletes.

Impact of heads-up display imaging on endoscopic task performance.

BACKGROUND AND PURPOSE: Heads-Up Imaging goggles provide ergonomic advantages to the endourologist. This study was designed to evaluate whether heads-up display impacts task performance for ureteroscopic stone retrieval. MATERIALS AND METHODS: The ability to capture a 5-mm calculus with a Cook N-Circle 2.2F stone basket from an inanimate caliceal model was tested by three experienced and three novice stone-basket operators. Visual display for initial testing for each operator was randomized to the OptiVu HD3 Heads-Up googles or a 20- inch Sony Triniton monitor (TV). Subsequent testing alternated between the two devices. Camera input was provided by the Storz telecam SL-NTSC. The HD3 was set up to align the direction of view with the operator's hands, while the TV was aligned at an angle 45 degrees lateral and 30 degrees superior to the operator's direction of view to approximate the traditional room set-up for an endourologic procedure. Each operator performed five basketing trials with each display set-up. RESULTS: Expert operators retrieved calculi more rapidly (9.2 +/- 5.9 seconds) than novice operators (50.7 +/- 48.9 seconds), irrespective of whether a TV monitor or goggle display was utilized as the imaging modality. No significant differences were noted in task performance between the two imaging modalities for the expert (P = b0.60), novice (P = 0.77), or overall (P = 0.91) groups. CONCLUSION: The Optiview Heads-Up goggle display system does not offer advantages in task performance with specific regard to the ability to capture stone fragments with baskets.