1. Introduction
Stress urinary incontinence (SUI) is a common problem that affects about a third of adult women, with onset at an average age of 45 years (1). It is defined as involuntary loss of urine with increasing intra-abdominal pressure as may occur during coughing, sneezing and physical activity (2), and is a cause of significant medical, social, and economic burdens (3-6). Risk factors for the development of SUI are well known and include age, genetic predisposition, menopause, obesity, and diabetes mellitus (7). Pelvic floor muscle dysfunction is strongly associated with the development of SUI, as it contributes to bladder prolapse, hypermobility of the bladder neck and impaired function of the urethral sphincter (2).
Treatment modalities for SUI include physical therapy, vaginal incontinence pessary, urethral bulking agent injections, and surgical repair (4). The cumulative incidence, or lifetime risk, of surgery for SUI is 13.6% (8). Midurethral sling placement (MUS) is considered the gold standard surgical solution for SUI, during which a polypropylene sling is inserted under the mid-urethra. The main routes for sling placement are the retropubic approach (sling curves around the pubic bone and exits through two suprapubic incisions) and transobturator approach (TOT) where the sling is directed through the obturator foramen to the inguinal folds (3).
MUS success rates are high (9), yet they carry risk for complications including pelvic organ injury and postoperative pain. The retropubic approach is more commonly linked to bladder perforation, injury to the intestines and large blood vessels. Complications of the transobturator approach on the other hand, include vaginal wall perforation, postoperative moving disability, and groin pain.
There is a paucity of evidence regarding the association between MUS and lower extremity dysfunction (10). Important anatomical structures in the vicinity of the sling route that could potentially be injured during surgery include: the deep external vascular bundle that is located near the groin; the deep femoral artery that crosses the obturator foramen; the obturator nerve with its two divisions (anterior and posterior) that exit the pelvis through the obturator canal; and the obturator-accessory nerve (11). Adequate function of hip muscles is beneficial in maintaining urinary continence. Hip replacement surgeries for patients with osteoarthritis for example, have been shown to alleviate incontinence symptoms, owing to their thigh muscles strengthening effect (12). This could be due to the anatomical relation between the obturator internus muscle and the levator ani muscle, the latter responsible for maintaining proper position of the bladder neck (13).
Based on the increasing prevalence of SUI surgeries, the potential for intraoperative injury to surrounding neuromuscular structures, and the importance of the hip musculature for daily functioning, we have sought to further evaluate the association between TOT procedures and various indices of hip joint pain and function.