Hypothesis / aims of study
Two decades have passed since sacral neuromodulation (SNM) was approved by the Food and Drug Administration (FDA) for urinary urge incontinence, with the addition of the tined lead in 2002. Yet a paucity of data exists on the safety of the tined lead, specifically the rate of lead breakage during revision or explant. Phase 2 of the InSite trial had a primary goal of evaluating the long term safety and efficacy of the tined lead, however, makes no mention of lead breakage rate. To date no rate of lead breakage has been published in any large study. In 2010, an educational brief was provided by the manufacturer quoting a 1% rate of lead breakage. This estimation was based on 45 cases reported to the manufacturer out of an estimated 4,482 leads explanted. The manufacturer also recommends removing the lead from a counter incision at the introducer site over the sacral foramen, as opposed to from the generator site, to minimize risk of lead breakage. Our institution has previously reviewed 5 year data regarding lead breakage rate, and noted a rate of 18% with risk factors of time since implant and diabetes. The purpose of this study was to extend this retrospective review, further define rate and risk factors for lead breakage, and evaluate the significance of surgical technique on this rate.
Study design, materials and methods
We retrospectively reviewed lead explants from 2006 to 2018. Patients with a non-tined lead, surgery due to infection, failed stage 1 lead explant, and missing information were excluded. Analysis of patient demographics included age, BMI, gender, and diabetes. Clinical factors analyzed included time since implantation, use of synergy dual leads, history of greater than one prior revision, and reason for explant including: loss of efficacy, elevated impedance, pain at SNM site, recent fall/trauma, need for MRI, or undesirable change in stimulation. Surgical techniques reviewed included cannulating the old lead with a straight stylet prior to lead removal, and removal from an incision over the sacral foramen vs removal of the lead from the generator site. Statistical analysis was completed using Mann-Whitney U test, Chi-square or Fisher Exact test was used as appropriate. A logistic regression analysis was performed for lead breakage including age, gender, diabetes, time since impact and other variables. P values of < 0.05 was considered statistically significant.
283 patients met study eligibility requirements. Patients were predominantly female (93%), non diabetic (85%), with mean age of 53 ± 16, mean BMI 29.3 ± 7.8, and mean time since implantation of 2.8 ± 2.1 years. The majority had the original lead placed at our institution with only 15% referred from an outside institution. The total number of leads broken was 23, for a rate of 8.1%. The only significant difference between lead intact to lead breakage groups was time since implantation (p<0.001). On univariate analysis the following clinical factors were predictive of lead breakage: male gender, diabetes, time since implantation, history of fall/trauma, and surgeon. On multivariate, only gender (OR 8.2 95% CI 2.6-25.5) and time since implantation (OR 0.675 95% CI 0.555-0.821) remained significant (p<0.001) . Surgical technique used for lead removal was not significant.
Interpretation of results
Upon review of all lead explants at a single institution since 2006 our overall rate of lead breakage was 8.1%. There was a 67% increased risk for leak breakage if time since lead implant was 4.5 years compared to 2.2 years. Males had an 8.2 times higher risk of lead breakage than females.