Proximity of percutaneous tibial nerve stimulation needle insertion to surrounding anatomic structures: a cadaveric study.

BACKGROUND: Percutaneous tibial nerve stimulation is a third-line treatment for overactive bladder and urgency urinary incontinence. During the procedure, a needle is inserted cephalad to the medial malleolus and posterior to the tibia. In recent years, permanent implants and leads have been developed for insertion into the medial ankle via a small incision. There are many important structures present in the medial compartment of the ankle, including the great saphenous vein, saphenous nerve, tibial nerve, posterior tibial vessels, and tendons of the posterior compartment leg muscles. OBJECTIVE: The primary objective of this study was to identify the proximity of the percutaneous tibial nerve stimulation needle placed per Food and Drug Administration-approved device instructions to nearby important anatomic structures. The secondary objectives were to identify the proximity of the tibial nerve to the needle site, identify clinically relevant ankle anatomic structures, and confirm the tibial nerve and posterior tibial vasculature by histologic analysis. STUDY DESIGN: Detailed medial ankle dissections were performed bilaterally on 10 female lightly embalmed anatomic donors (cadavers) obtained from the Willed Body Program at the University of Louisville. A pin was inserted at the percutaneous tibial nerve stimulation needle site, and the medial ankle was minimally dissected so the surrounding anatomic structures were visible but not disrupted. The shortest distance from the pin to the selected structures of the medial ankle region was measured. On completion of each dissection and set of measurements, tissue was harvested for histologic examination. The distances between the pin and each structure were assessed using means and standard deviations. A paired t test was used to assess the difference in the locations between the left and right ankles. Statistical analysis was performed on left-sided, right-sided, and combined measurements. An 80% prediction interval was found to represent the expected range of values for the measurement of a new cadaver or patient, and the 95% confidence interval of the mean was computed to characterize the average distance across all cadavers or patients. RESULTS: The medial ankle of 10 adult female lightly embalmed cadavers were examined bilaterally. Dissections were completed from October 2021 to July 2022. Of note, 80% prediction intervals for the tibial nerve, the posterior tibial artery or vein, and the flexor digitorum longus tendon had a lower range of 0.0 mm from the pin and extending to 12.1, 9.5, and 13.9 mm, respectively. Moreover, 2 of the structures were found to be asymmetrical between the right and left ankles. The great saphenous vein was further from the pin on the left (20.5 mm [standard deviation of 6.4 mm] on the left vs 18.1 mm [standard deviation of 5.3 mm] on the right; P=.04). The calcaneal (Achilles) tendon was further from the pin on the right side (13.2 mm [standard deviation of 6.8 mm] vs 7.9 mm [standard deviation of 6.7 mm]; P=.04). Tibial neurovascular structures were confirmed with microscopic analysis. CONCLUSION: The anatomic structures within the medial ankle lie unexpectedly close to the percutaneous tibial nerve stimulation needle site as noted per Food and Drug Administration-approved device instructions. There is a possibility that some medial ankle structures are not symmetrical. It is crucial that practitioners understand medial ankle anatomy when performing percutaneous tibial nerve stimulation or permanent device insertion.

Postoperative Opioid Filling Patterns in Women Undergoing Midurethral Sling Placement.

OBJECTIVE: To evaluate postoperative opioid filling patterns for patients undergoing isolated midurethral sling placement. METHODS: Patients undergoing midurethral sling placement from 2005 to 2016 were identified in the Truven Health MarketScan database. We determined whether sling placement was an isolated procedure or performed in conjunction with other benign gynecologic procedures. All outpatient prescription drug claims for opioids were extracted from 28 days before surgery to 28 days after surgery. We identified the number of prescriptions filled and calculated morphine milligram equivalents (MMEs) in the allotted perioperative windows. The proportion of patients with opioid prescription claims and cumulative MMEs were compared for multiple versus isolated procedures using χ2 and Wilcoxon tests, respectively. RESULTS: The cohort included 153,631 patients, with 79,069 (51.5%) having an isolated procedure and 74,562 (48.5%) having multiple benign procedures. Seventy-two percent of the patients undergoing isolated midurethral sling placement received at least 1 opioid prescription in the study period compared with 79% of those undergoing combined procedures (P < 0.001). The median cumulative MMEs for isolated midurethral sling and midurethral sling + multiple procedures were 150 and 225 MMEs, respectively (P < 0.001). Across the years under study, the proportion of patients filling opioid prescription claims increased, but the median cumulative MME was unchanged. CONCLUSIONS: Patients undergoing isolated midurethral sling placement filled a median of 150 cumulative MMEs, and the proportion of patients filling perioperative opioid prescriptions increased over the study period.