Optimal Lead Positioning in Sacral Neuromodulation: Which Factors Are Related to Treatment Outcome?

Two-Staged Sacral Neuromodulation for the Treatment of Nonobstructive Urinary Retention: A Multicenter Study Assessing Predictors of Success

OBJECTIVES

The aims of this study were to 1) determine the success rate of the tined lead test phase in patients with nonobstructive urinary retention (NOUR), 2) determine predictive factors of a successful test phase in patients with NOUR, and 3) determine long-term treatment efficacy and satisfaction in patients with NOUR.

MATERIALS AND METHODS

The first part was a multicenter retrospective study at two centers in The Netherlands. Patients with NOUR received a four-week tined lead test phase. Success was defined as a ≥50% reduction of clean intermittent catheterization frequency or postvoid residual. We analyzed possible predictors of success with multivariable logistic regression. Second, all patients received a questionnaire to assess efficacy, perceived health (Patient Global Impression of Improvement), and treatment satisfaction.

RESULTS

This study included 215 consecutive patients (82 men and 133 women) who underwent a tined lead test phase for the treatment of NOUR. The success rate in women was significantly higher than in men, respectively 62% (83/133) and 22% (18/82, p < 0.001). In women, age per ten years (odds ratio [OR] 0.74, 95% CI: 0.59-0.93) and a history of psychiatric illness (OR 3.92, 95% CI: 1.51-10.2), including posttraumatic stress disorder (PTSD), significantly predicted first stage sacral neuromodulation (SNM) success. In men, age per ten years (OR 0.43, 95% CI: 0.25-0.72) and previous transurethral resection of the prostate and/or bladder neck incision (OR 7.71, 95% CI: 1.43-41.5) were significant predictors of success. Conversely, inability to void during a urodynamic study (for women, OR 0.79, 95% CI: 0.35-1.78; for men, OR 3.06, 95% CI: 0.83-11.3) was not predictive of success. Of the patients with a successful first stage, 75% (76/101) responded to the questionnaire at a median follow-up of three years. Of these patients, 87% (66/76) continued to use their SNM system, and 92% (70/76) would recommend SNM to other patients.

CONCLUSIONS

A history of psychiatric illness, including PTSD, in women with NOUR increased the odds of first stage SNM success 3.92 times. A previous transurethral resection of the prostate and/or bladder neck incision in men increased the odds of success 7.71 times. In addition, a ten-year age increase was associated with an OR of 0.43 in men and 0.74 in women, indicating a 2.3- and 1.3-times decreased odds of success, respectively.

Comparison of surgical techniques for optimal lead placement in sacral neuromodulation: a cadaver study

Background

Sacral neuromodulation (SNM) is a common treatment for patients with urinary and faecal incontinence. A close contact of the tined lead electrode with the targeted nerve is likely to improve functional outcome.

The aim of this study was to compare the position of the SNM lead in relation to the sacral nerve by comparing different implantation techniques.

Methods

This cadaver study was conducted at the Division of Anatomy of Vienna's Medical University in October 2020. We dissected 10 cadavers after bilateral SNM lead implantation (n = 20), using two different standardized implantation techniques. The cadavers were categorized as group A (n = 10), representing the conventional guided implantation group and group B (n = 10), where SNM implantation was conducted with the novel fluoroscopy-guided “H”-technique. The primary goal was to assess the distance between the sacral nerve and the lead placement.

Results

The electrodes were inserted at a median angle of 58.5° (46–65°) in group A and 60° (50–65°) in group B, without reaching statistical significance. In 8 cadavers, the lead entered the S3 foramen successfully.

The median distance of the lead to the nerve did not show a significant difference between both groups (E0: Group A: 0.0 mm vs. Group B: 0.0 mm, p = 0.969; E1: Group A: 0.0 mm vs. Group B: 0.5 mm p = 0.754; E2: Group A: 2.5 mm vs. Group B: 2.5 mm p = 1.000; E3: Group A: 3.5 mm vs. Group B: 4.0 mm p = 0.675). In 2 cases (20%) of the conventional group A, the lead was misplaced and located at the gluteal muscle.

Perforation of the presacral fascia was observed in one lead placement in group A and in two placements in group B.

Conclusions

Both standardized implantation techniques may ensure close electrode proximity to the targeted nerve. Misplacement of the electrode was more often observed with the conventional implantation technique.

Predictive Factors in Sacral Neuromodulation: A Systematic Review

INTRODUCTION

Sacral neuromodulation (SNM) is an effective treatment in patients with overactive bladder syndrome or nonobstructive urinary retention when conservative treatment fails. Several factors that could impact outcome with SNM have been studied. This systematic review investigated these predictive factors and their relevance for clinical practice.

METHODS

Systematic review according to the PRISMA guidelines was conducted. This review is registered in the PROSPERO register (CRD42015016256).

RESULTS

Seventy-eight studies (of which 11 abstracts) were included. Females, younger patients, and a tined lead procedure tend to be predictive in successful SNM outcome. Factors that did not influence SNM outcome were prior back surgery, surgery for stress urinary incontinence, affective symptoms, and duration of complaints. Reduced detrusor contractility is associated with a lower success rate. The level of evidence of most studies (graded according to the Centre for Evidence-Based Medicine) was 3b.

CONCLUSION

Even though this systematic review investigated predictive factors (gender, age, type of procedure, type of lead, and detrusor contractility), no general consensus on predictive factors could be made. Most studies are small, retrospective, and involve a heterogeneous population. Therefore, prospective research in larger specific patient groups remains necessary to find predictors of SNM outcome.

Application of ultrasound during electrode implantation for sacral neuromodulation in patients with neurogenic bladder secondary to spinal cord disease: a retrospective study

PURPOSE

To compare the use of intraoperative ultrasound with X-ray fluoroscopy during sacral neuromodulation lead electrode placement in patients with neurogenic bladder secondary to spinal cord disease.

METHODS

We reviewed the medical records of 52 patients who underwent sacral neuromodulation (SNM) lead electrode implantation under fluoroscopy or ultrasound guidance from July 2016 to July 2019. The operating time, number of electrode contacts with stimulus responses, minimum voltage that causes a stimulus response, and rate of standard lead electrode placement were used to assess the differences between the two methods. All patients were evaluated by recording bladder diaries, postvoid residual volumes before and during the testing period. Permanent SNM implantation is acceptable if symptoms improve by at least 50%.

RESULTS

The operating time decreased from 87.1 ± 25.19 min in the X-ray group to 68.2 ± 25.20 min (p < 0.05) in the ultrasound group. The number of electrode contacts with stimulus responses, rate of standard lead electrode placement, and implantable pulse generator (IPG) placement rate were not significantly different between the two groups (p > 0.05). There was no radiation exposure during the operation in the ultrasound group. No incisional infections, hematomas, or other critical complications were reported in either groups.

CONCLUSION

Ultrasound can be applied to safely place lead electrode for sacral neuromodulation and leads to no radiation exposure to the patient, surgeon, and operating room staff and a shortened operating time while maintaining the same efficacy as X-ray.

Standardized fluoroscopy-guided implantation technique enables optimal electrode placement in sacral neuromodulation: a cadaver study

BACKGROUND

Sacral neuromodulation (SNM) is an established treatment option for patients with faecal incontinence. The location of the stimulating electrode is considered to be essential for treatment success. The purpose of this study was to evaluate the position of SNM electrodes after using a standardized fluoroscopy-guided implantation technique.

METHODS

For this cadaver study, SNM electrodes were implanted bilaterally in 5 lower body specimens. The lower edge of the sacroiliac joint and the medial edge of the sacral foramina were marked using fluoroscopy to draw an 'H' with the crossing points identifying S3. After electrode placement the pelvis was dissected to describe the exact position of the SNM electrodes.

RESULTS

The electrodes were inserted at an angle with a median degree measure of 60° (range 50-65°) to the skin, with a median distance of 9 mm (range 0-13 mm) from the S3 marking. All electrodes entered the third sacral foramen. The median distance of the electrodes to the sacral nerve was 0 mm (range 0-3 mm) for the most proximal, 0.5 mm (range 0-5 mm) for the second, 2.25 mm (range 0-11 mm) for the third and 1.75 mm (range 0-16 mm) for the most distant electrode. There was neither a significant difference in the proximity of the electrodes to the nerve between the right and left side (proximal to distal electrode: p = 0.18, p = 0.16, p = 0.07, p = 0.07) nor between male and female cadavers (p = 0.25, p = 0.21, p = 0.66, p = 0.66).

CONCLUSIONS

A standardized fluoroscopy-guided implantation technique enables a close contact between electrode and nerve. This can potentially result in an improved clinical outcome.

Sacral Neuromodulation: Determining Predictors of Success

OBJECTIVE

To determine predictors of success for sacral neuromodulation in women with overactive bladder, urinary retention, and fecal incontinence.

METHODS

A retrospective chart review was performed on women who underwent a staged sacral neuromodulation implantation between 2007 and 2018. Clinical and procedural characteristics were recorded. Presence of intraoperative motor responses in either all 4 or <4 electrodes were used to group women. Endpoints included completion of stage II implant, tined lead revision, and patient-reported success.

RESULTS

In 198 women with a mean age of 62.9 years (SD+/- 14.7), completion of stage II implant occurred in 92.4% of women, and 83.3% of these women reported success at the first postoperative visit. Continued success at 6 months was reported in 70.3%. Lead revision was noted in 23.0%. Age >65 years (odds ratio [OR] = 0.2, 95% confidence interval [CI] = 0.06-0.8) and prior onabotulinumtoxinA (onaBoNT-A) (OR = 0.2, 95% CI = 0.06-0.9) were negative predictors for completion of stage II implant on multivariable analysis. Also, prior pelvic floor physical therapy was a significant negative predictor of postoperative patient-reported success on multivariable analysis (OR = 0.25, 95% CI = 0.1-0.6). There were no differences seen in women who had motor responses with either all 4 electrodes or <4 electrodes in any endpoint (P > .05).

CONCLUSION

Patient age >65 and history of prior onaBoNT-A were associated with failure to complete stage II implant. Women with prior pelvic floor physical therapy were less likely to report success after sacral neuromodulation. Motor responses in <4 electrodes during lead testing did not impact patient-reported success.

Variation in bony landmarks and predictors of success with sacral neuromodulation

INTRODUCTION AND HYPOTHESIS

We assessed variations in sacral anatomy and lead placement as predictors of sacral neuromodulation (SNM) success. Based solely on bony landmarks, we also assessed the accuracy of the 9 and 2 protocol for locating S3.

METHODS

This is a retrospective cohort study performed from October 2008 to December 2016 at the University of North Carolina at Chapel Hill. Fluoroscopic images were used to assess sacral anatomy and lead location. Success was defined as >50% symptom improvement after stage I and clinical response at most recent follow-up.

RESULTS

Of 249 procedures, 209 were primary implants and 40 were revisions among 187 (89.5%) women and 22 (10.5%) men. Success rate was 83.3% for primary implants and 89.4% for revisions. Success was associated with shorter implant duration (21.3 ± 22.2 vs 33.6 ± 25.8 months), higher body mass index (30.3 ± 7.8 vs 27.6 ± 6.1 kg/m²), and straight vs curved lead (90.5% vs 80.5%) (all p = .05), but not with sacral anatomy or lead placement. In assessing the 9 and 2 protocol, mean distance from coccyx to S3 did not equal 9 cm: 7.4 ± 1.0 vs 7.2 ± 0.8 cm (p = .26), while mean distance from midline to S3 did equal 2 cm: 1.9 ± 0.4 vs 2.0 ± 0.7 cm (p = .37).

CONCLUSIONS

Variations in sacral anatomy and lead placement did not predict SNM success. The 2-cm protocol was verified while the 9-cm protocol was not, although neither was predictive of success, which may obviate the need to mark bony landmarks prior to fluoroscopy.

Application of an individualized and reassemblable 3D printing navigation template for accurate puncture during sacral neuromodulation

OBJECTIVE

To evaluate the feasibility and safety of an individualized and reassemblable three-dimensional (3D) printing navigation template for making accurate punctures during sacral neuromodulation (SNM).

METHODS

From July 2016 to July 2017, 24 patients undergoing SNM were enrolled. Conventional X-ray guidance was used in the control group, which included 14 patients, while the 3D printing template was used in the experimental group, which included 10 patients. The number of punctures, the average puncture time, the exposure to X-ray, the adjustment time during the operation and the testing of the SNM device, the infection and haemorrhage rate, and the implantable pulse generator (IPG) implantation rates were compared between the two groups.

RESULTS

In total, 24 patients successfully underwent stage I. When comparing the control group and the experimental group, the number of punctures were 9.6 ± 7.7 and 1.5 ± 0.7, respectively; the average puncture times were 35.4 ± 14.6 and 4.1 ± 2.2 min, respectively; and the X-ray exposure levels were 8.37 ± 4.83 mAs and 2.34 ± 0.54 mAs, respectively. No postoperative complications were reported in either group. The IPG implantation rates were not different between the two groups.

CONCLUSION

The 3D printing template for SNM can help us to perform accurate and quick punctures into the target sacral foramina, reduce X-ray exposure, and shorten the operation time. For patients with obesity, sacral variation, sacral bone fractures or losses and for patients who are unable to tolerate the prone position during operation, use of the 3D printing template is recommended.

International Continence Society best practice statement for use of sacral neuromodulation

AIMS

Sacral neuromodulation (SNM) is an accepted therapy for a variety of conditions. However, despite over 20 years of experience, it remains a specialized procedure with a number of subtleties. Here we present the recommendations issued from the International Continence Society (ICS) SNM Consensus Panel.

METHODS

Under the auspices of the ICS, eight urologists, three colorectal surgeons and two urogynecologists, covering a wide breadth of geographic and specialty interest representation, met in January 2017 to discuss best practices for neuromodulation. Suggestions for statements were submitted in advance and specific topics were assigned to committee members, who prepared and presented supporting data to the group, at which time each topic was discussed in depth. Best practice statements were formulated based on available data. This document was then circulated to multiple external reviewers after which final edits were made and approved by the group.

RESULTS

The present recommendations, based on the most relevant data available in the literature, as well as expert opinion, address a variety of specific and at times problematic issues associated with SNM. These include the use of SNM for a variety of underlying conditions, need for pre-procedural testing, use of staged versus single-stage procedures, screening for success during the trial phase, ideal anesthesia, device implantation, post-procedural management, trouble-shooting loss of device function, and future directions for research.

CONCLUSIONS

These guidelines undoubtedly constitute a reference document, which will help urologists, gynecologists, and colorectal surgeons optimize their use of SNM for refractory urinary urgency and frequency, UUI, NOR, and FI.