MRI anatomical study of the outside-in transobturator suburethral tape procedure.

Background: This study aims to clarify the relationship between the outside-in transobturator suburethral tape and the anatomical structures at the blind passage of the obturator foramen, and to detail the tape position, shape, and the factors on which they are dependent.

Methods: MRI scans were performed on 30 patients operated on with a dermal porcine collagen suburethral tape, indicated for urodynamically proven stress incontinence.

Results: The lateral bladder wall was the closest structure to the tape at the passage of the obturator foramen, whereas vascular injuries appeared to be minimal using the outside-in technique. The distance from tape to bladder neck was correlated with the distance from tape to pubococcygeal line (PCL) (p=0.001), and with urethral length (p=0.049). From the obturator foramen to its passage under the urethra, the tape was U-shaped with a cranio-caudal and antero-posterior orientation. The cranio-caudal tape shape was correlated with the distance between the tape and the PCL (p=0.002), and to the patient's anatomical characteristics: distance between the bladder neck and the pubis (p=0.01), and the urethral length (p=0.01). The antero-posterior shape was correlated with the urethral length (p=0.02).

Conclusion: The lateral bladder wall is the structure most at risk during the outside-in transobturator suburethral tape procedure. The distance from tape to bladder neck is dependent on the vertical position of the tape. The tape shape is dependent on both tape position under the urethra and the patient's anatomical characteristics.