Sacral neuromodulation (SNM) plays a critical role in the management of patients with lower urinary tract disorders. Accurate entry marking on skin for foramen needle placement is a crucial step in achieving optimal lead placement. Identifying, accurately marking S3 foramen can sometimes be challenging due to various anatomical factors. This can often lead to increased X-ray exposure, multiple needle insertion, prolonged surgery. Precise electrode placement at the optimal point of the S3 enhances surgical success, allowing for higher efficacy at lower stimulation currents, thereby extending battery life. We evaluate effectiveness of patient-specific 3D modeling-based surgical planning in SNM test phase. By utilizing the patient’s radiological data, we aim to assess its impact on S3 foramen localization, operative time, X-ray exposure, and other relevant parameters.

16 patients (4 male, 12 female) diagnosed with neurogenic (excluding complete spinal cord injury), non-neurogenic voiding dysfunction were included. All patients successfully underwent first stage of SNM by one surgeon. All patients underwent sacral-specific computed tomography (CT) imaging. With Mimics software, 3D modeling of the sacrum-surrounding tissues was performed. Before surgery, each patient was informed about the first stage of SNM through surgical planning session. Patient age, gender, indication, comorbidities, medication use, the frequency of clean intermittent catheterization (CIC), 3D modeling time were evaluated. Intraoperative parameters were analyzed, including operative time (min.), number of needle insertions, time to locate the S3 foramen (min.), presence of the bellow sign and toe reflex, and the placement site of the tined lead (right/left). In 3D images (Fig.1), following anatomical measurements were obtained: distance between the tip of the coccyx and the S3 foramen (mm), between the tip of the coccyx and the needle entry point (mm), between the needle entry point and the S3 foramen (mm), needle insertion angle (degrees), S3 foramen diameter (mm), S3 foramen depth (mm), between the midline and the needle entry point (mm). In surgery, these measurements were marked on the patient in a modified prone position (Fig.2), needle insertion was performed based on these measurements without the use of A-P X-ray imaging. The procedure included: sedation, patient positioning, marking of 3D modeling measurement points, local anesthesia and needle placement, reflex verification (4 to 1 mAmp), directional guide and introducer sheath placement, tined lead placement, preparation of the battery pocket, lead tunneling and individual electrode testing (3-2-1-0). We assessed impact of 3D modeling-based surgical planning on intraoperative parameters.

Mean age was 45.4 years (24–77). 8 had neurogenic voiding dysfunction, 8 had non-neurogenic voiding dysfunction. 3D modeling was performed for all patients, with a mean modeling duration of 110 min. (75–145). Mean operative time (min.), 44.5 (32-54), mean number of needle insertion, 1.2 (1-2), mean time to find the S3 foramen (min.), 0.8 (0.6- 1.0), presence of the bellow sign- toe reflex, 16 (all), the placement site of the tined lead (2 right/14 left) were detected. The mean distance between the tip of the coccyx and the S3 foramen (mm),70.3 (51.0- 85.8), between the tip of the coccyx and the needle entry point (mm), 93.0 (67.9- 103.7), between the needle entry point and the S3 foramen (mm), 43.3 (32.6- 51.2), mean needle insertion angle (degree), 61.7 (60.4- 67.7), S3 foramen diameter (mm), 6.1 (4.3-8.9), S3 foramen depth (mm), 3.0 (1.4-4.8), between the midline and the needle entry point (mm), 22.1 (17.7- 23.1) were measured.

We found reduction in the number of needle insertions, needle insertion time, overall operative time with use of 3D modeling. 3D modeling based surgical planing can effectively optimize the surgical process, potentially saving time, enhancing operational efficiency.

3D modeling  can be future modality that can enhance the SNM process with high success.