Biomechanics of Urinary Stress Incontinence Surgery – Theory of the Non-Permanently Acting Suburethral Supportive Structure

This biochemical study of the lower urinary tract as it relates to urinary continence and incontinence is based on the morphotopographic results of radiological, autopsy and surgical investigations in the period 1966–1968. The process of urinary continence is simply explained by the application of universal hydromechanical laws, which demonstrated that continence during straining results from compression of the urethra over a suburethral resistant structure. Compression occurs during dorsocaudal physiologic displacement of the urethrovesical complex in conditions of increased intra-abdominal pressure. The theory of a non-permanently acting suburethral support is based on these results and represents the essential principle of urinary stress incontinence surgery, namely, that surgery should create a suburethral resistance over which the proximal urethra is compressed during increased intra-abdominal pressure.  Such suburethral resistance may be created via the vaginal or the abdominal routes, using autogenous or heterogeneous tissue. A critical analysis of different surgical techniques and how they achieve the demands of this theory is presented. In this context two orginal surgical procedures incorporating the best biomechanical features are elaborated: slinglike colposuspension via the abdominal route, and suburethral duplication of the anterior vaginal wall by the vaginal route. The aim of this paper is to present the biomechanical study of urethrovesical phenomena playing a role in urinary continence and the pathogenesis and surgery of stress incontinence in light of our theory. Our personal experience with 1836 surgical procedures between 1968 and the end of 1997, encompassing 1056 slinglike colposuspensions and 780 suburethral duplications of the vagina, gives practical support to our concepts.     

Role of the pelvic floor in Bladder neck opening and closure II: Vagina

The aim of the study was to examine the role of vaginal stretching during bladder neck opening and closure. The study group comprised 12 patients with GSI and 4 controls. The position of the bladder neck relative to the vagina was assessed in the resting, straining and ‘squeezing’ positions using video-radiological studies. Radio-opaque dye was instilled into the bladder, vagina, rectum and levator plate. Vascular clips applied to the midurethral, bladder neck and bladder base parts of the anterior vaginal wall assisted in determining differential movements of these parts of the vagina during bladder neck opening and closure. The suburethral vagina (hammock) was shown to stretch downwards and forwards during straining, and downwards and backwards during micturition. The bladder neck, upper part of the vagina and the rectum were stretched backwards and downwards in an identical manner during straining and micturition, apparently in response to backward contraction of the levator plate and downward angulation of its anterior lip. All organs were stretched upwards and forwards during ‘squeezing’. The findings support the hypothesis that, during stress and micturition, selective pelvic floor contractions stretch the vagina against intact pubourethral and uterosacral ligaments to assist opening and closure of the urethra and bladder neck. EDITORIAL COMMENT: The authors propose a new theory for the mechanism of micturition and continence. The new ‘Integral Theory’ describes the role of the vagina and three pelvic floor muscles, the levator plate, the anterior portion of the pubococcygeus (PCM) and the longitudinal muscles of the anus (LMA) in the opening and closing of the urethra. Unlike the ‘hammock hypothesis’, proposed by Delancey, the authors believe it is the forward movement of the vagina around its attachment to the pubourethral ligaments via contraction of the PCM that closes off the urethra, and not increased abdominal pressure transmission to the proximal urethra. Their proposed mechanism for incontinence is laxity of the vaginal hammock and decreased forward motion, and less compression of the urethra. This theory is also in contrast to Shafik’s ‘common sphincter’ concept of continence, which stresses the importance of the puborectalis and external urethral sphincter as the main mechanism for continence, with no significance given to the role of the anterior vaginal wall or its attachment and movement around the pubourethral ligament. This new integral theory is based on findings of muscle movements using cadaveric dissection, video X-ray studies, digital palpation, EMG and dynamic urethral pressure measurements. This is an interesting theory which again emphasizes the role of the pelvic floor muscles, not only in their support function but also in their role of active movements of the viscera within the bony pelvis.     

Clinical and urodynamic evaluation of the polypropylene (marlex) sling for genuine stress incontinence

Ten women undergoing a polypropylene suburethral sling procedure for treatment of genuine stress incontinence were assessed pre- and post-operatively by standard urodynamic methods and by urethral pressure profile measurements at rest and on stress. Eight patients were subjectively and seven objectively cured of stress incontinence. A significant reduction in urine flow rate was found although this appeared to be of little relevance to the successful outcome of surgery. An increase in resting urethral profile length was seen in both successful and unsuccessful cases. The former also had an improvement in maximum urethral closure pressure on stress due to improvement in pressure transmission in the proximal three quarters of the functional urethral length. The urethra appeared relocated in a retropubic position following successful and unsuccessful operations. It is likely that failure was associated with periurethral fibrosis causing failure of pressure transmission despite adequate elevation.     

Mechanism of Postoperative Urinary Continence

Stress incontinence used to be attributed mostly to urethral hypermobility, and consequently most surgical techniques focused on the region of the bladder neck and proximal urethra. This article reviews our knowledge about the mechanism of postoperative urinary continence based on anatomic, imaging and urodynamic studies. Reduction of urethral mobility, as measured by cotton swab testing or imaging studies, is not the only reason why continence surgery succeeds. Imaging techniques are of limited value for elucidating the continence mechanism because radiologic landmarks and criteria are not reproducible. Urodynamically, the increased pressure transmission after successful continence surgery is attributed to the retropubic repositioning of the urethra, its compression against the anterior vaginal wall, and improved transmission of intra-abdominal pressure during stress. The role of the ‘functional’ urethral obstruction remains to be studied. In incontinent patients with hypermobility of the bladder neck and proximal urethra continence can be achieved by surgical correction. However, stress incontinence is possible in the absence of urethral hypermobility, and standard surgical techniques can fail to restore continence in these patients.     

Stress incontinence investigated with urodynamics 30 years ago

An article published in 1961 is reviewed. It reported on the simultaneously measured pressures in the urethra and bladder of both healthy women and women afflicted by stress incontinence. It was found that the difference between the two pressures was crucial for the preservation of continence. If pressure in one section of the urethra was higher than in the bladder, urine could not enter that section and closure was maintained. In patients with stress incontinence it was noted that when the difference in pressure, closure pressure, was lowered to zero during coughing, leakage would be noted. This was due to low urethral muscle tone causing a low resting closure pressure, as well as to an incomplete transmittance of abdominal pressure to the upper urethra. An operation for stress incontinence causes the upper urethra to be more fully exposed to increases in intra-abdominal pressure, so that physical activity has less effect on closure pressure.     

Observations on the function of the female urethra: III: An overview with special reference to the relation between urethral hypermobility and urethral incompetence

AIMS: To analyze the relation between urethral hypermobility and urethral incompetence, and to summarize the interdependence between maximum urethral closure pressure (MUCP), urethral hypermobility, and urethral incompetence. PATIENTS AND METHODS: A group of 255 patients was selected from a large bank of cases. Inclusion criteria were age 20 years or above, no neurological disease, stable bladder, and no previous incontinence surgery or hysterectomy. The degree of hypermobility (cysto-urethrocele) and the degree of urethral incompetence (abdominal leak point pressure (ALPP)) were determined. Statistical analyses between urethral hypermobility and incompetence were performed with Spearman's correlation and the Jonckherre-Terpstra test. RESULTS: The Spearman's rank correlation test showed a statistically significant relation between urethral hypermobility and the degree of urethral incompetence (P = 0.0049). CONCLUSIONS: The statistically significant relation between urethral incompetence and hypermobility suggests that urethral incompetence will increase as the degree of urethral hypermobility does. Optimal conditions for urinary continence include a high maximum urethral closure pressure, absence of hypermobility, and a low degree of urethral incompetence. This last factor is assured by a strong support underneath the urethra permitting compression of the latter during straining. Failure of the urethral closure mechanism is highly probable with a diminished maximum closure pressure accompanied by urethral hypermobility often associated with a high degree of urethral incompetence. Clinically significant urinary incontinence may appear in many intermediate circumstances between these two extreme states, but stress urinary incontinence is essentially an activity-related phenomenon.     

Suburethral duplication of the vaginal wall — An original operation for urinary stress incontinence in women

The ideal surgery for urinary stress incontinence should be represented by operations producing increases in urethral closure pressure only when the intra-abdominal pressure is elevated. Guided by this principle the author proposes an original vaginal operation creating a suburethral duplication of the anterior vaginal wall, together with Halban's fascia, located under the proximal urethra just below the bladder neck. Over this supportive duplication the urethra is compressed during its dorsocaudal physiologic displacements. The technical details and indications of the procedure are fully described. In the period from 1974 to 1991, at the Department of Obstetrics and Gynecology, Medical Faculty, Skopje, 481 operations were performed. In this series, 74 patients had pre- and postoperative urodynamic evaluations. At 2 years 93.3% were continent without demonstrable obstruction. The simple technique and the use of autologous tissue, together with the lack of major complications and low recurrence rate, are the best advocates for the surgical procedure.Editorial Comment: This article presents a vaginal approach to the correction of stress incontinence which utilizes the well known principle of differential support of the urethrovesical junction rather than the bladder. A suburethral bar is created using the vaginal wall. Urodynamic studies were done pre- and postoperatively on 71 patients, who were followed for 2 years. These studies demonstrated a 93.3% success rate, using the absence of urine loss with a full bladder during stress as the criterion for cure. Urethral closure pressure was also found to be increased. This is the same technique as proposed Goebell in 1910 and Ingleman-Sundberg in 1947, who utilized other structures to create a differential resistance between the proximal urethra and the base of the bladder. This is an interesting procedure and will wait for others to validate its success.     

Suburethral sling procedure for genuine stress incontinence and low urethral closure pressure. A continued experience

Forty-eight patients with genuine stress incontinence and low urethral closure pressure have undergone a suburethral sling procedure using polytetrafluoroethylene. Forty-five of the 48 patients have been followed up beyond 3 months, allowing assessment of postoperative complications. Ten patients required intermittent self-catheterization, 6 continuing beyond 3 months secondary to obstructed voiding or vesical dysfunction. Six slings were removed due to graft infection and/or vaginal mucosa erosion. All patients who were continent prior to removal remained so afterwards. Two slings were loosened secondary to obstructed voiding (1 patient experienced improved voiding, the other continued intermittent catheterization). Sixty-two per cent (28/45) of the patients followed, developed at least one documented urinary tract infection. Thirty-four of the 45 patients followed, underwent postoperative multichannel urodynamic testing. Ten patients (29%) demonstrated postoperative detrusor instability (5 were new onset, 5 were persistent). Six improved with medication and bladder retraining drills. Twenty-eight of the 34 patients tested (82.4%) were objectively cured of genuine stress incontinence. In spite of the complications noted, this suburethral sling procedure offers a high success rate and is a viable alternative in treating patients with genuine stress incontinence and low urethral closure pressure. Modifications in surgical technique have been made to reduce postoperative complications in the future.     

Dynamic suburethral suspension with pedicled external oblique aponeurosis in the management of female urinary incontinence.

PURPOSE: Despite excellent postoperative continence with pubovaginal sling procedures, the resultant morbidities of de novo urgency and urinary obstruction due to sling tension remain valid concerns. The feasibility and outcome of dynamic suburethral suspension using bilateral strips of external oblique aponeurosis left attached medially to the anterior rectus sheath and joined beneath the urethra under no tension were determined. MATERIALS AND METHODS: Between May 1995 and April 1998, 25 women with stress urinary incontinence were evaluated and underwent a dynamic suburethral suspension procedure. All patients were followed annually with a 10-point questionnaire by an independent registered nurse who analyzed the results, complications and satisfaction outcome. RESULTS: At a mean followup of 26 months all patients (100%) were cured of stress incontinence. Associated urge incontinence due to detrusor overactivity persisted in 3 patients postoperatively and, thus, the overall postoperative cure/dry rate was 88% for the study group. Of the 18 patients with preoperative urgency 12 (66%) were cured postoperatively. De novo urgency developed in 1 patient after surgery. No patient had prolonged urinary retention. Overall 92% of the patients were satisfied with the outcome of surgery. CONCLUSIONS: This dynamic suburethral suspension procedure cured stress incontinence in the majority of patients with no resultant urinary obstruction. The mechanism of action is believed to work by providing a viable suburethral "backboard" of support and by dynamic lifting of the proximal urethra cradled by the fascial loop precisely at the time of abdominal strain. Pronounced urge incontinence due to detrusor overactivity is unlikely to benefit from suspension procedures.     

Role of autologous bladder-neck slings: a urogynecology perspective

The concept of the autologous pubovaginal sling involves supporting the proximal urethra and bladder neck with a piece of graft material, achieving continence either by providing a direct compressive force on the urethra/bladder outlet or by reestablishing a reinforcing platform or hammock against which the urethra is compressed during transmission of increased abdominal pressure. Pubovaginal slings using a biological sling material (whether autologous, allograft, or xenograft) can be used successfully to manage primary or recurrent stress incontinence. This article addresses the indications for the use of an autologous bladder-neck sling, describes the surgical techniques, and discusses outcomes and technical considerations.     

The urethral pressure profile under stress: A comparison of profiles on coughing and straining

In terms of urethral pressure measurements the distinction between stress-incontinent and continent women is perhaps best made by examining the urethral response to stress. Profiles may be performed during the repeated intraabdominal pressure rises due to coughing, or the sustained effect of straining; the relationship between the two has not previously been defined. This comparative study involves 120 patients with a variety of urinary symptoms in whom stress profiles were performed both on coughing and on straining. Parameters of the cough profile were found to be more repeatable than those of the strain profile. and also related more closely to the severity of incontinence. Calculation of pressure transmission ratios from cough profiles also proved more useful. since they allow the acute and sustained components of the urethral response to stress to be readily distinguished.     

Surgery for female stress urinary incontinence with transobturator tape

The aim of suburethral transobturator suspension is to cure the women stress urinary incontinence. The concept underlying this apparatus is based on several points: it reproduces the urethral fascia; it complies with Delancey's concept; it consists of a tension-free band through the soft structures of the obturator fossa; it is a perineal surgery. This surgery needs specific devices: a synthetic tape and a specific tool to introduce it, the tunnelling device. Respecting some technical landmarks are mandatory to ensure successful intervention: the vaginal incision must include all the thickness of the vaginal wall; the trans-obturated endpoint must be located at the level of the mid urethra; the tunnelling device must have a close contact with the ischiopubic bone; the finger inside the incision protects the urethra and drives the tunnelling device inside the vaginal incision.     

The pathophysiology of stress urinary incontinence in women and its implications for surgical treatment

Stress urinary incontinence is a symptom that arises from damage to the muscles, nerves, and connective tissue of the pelvic floor. Urethral support, vesical neck function, and function of the urethral muscles are important determinants of continence. The urethra is supported by the action of the levator ani muscles through their connection to the endopelvic fascia of the anterior vaginal wall. Damage to the connection between this fascia and muscle, loss of nerve supply to the muscle, or direct muscle damage can influence continence. In addition, loss of normal vesical neck closure can result in incontinence despite normal urethral support. Although the traditional attitude has been to ignore the urethra as a factor contributing to continence, it does play a role in determining stress continence since in 50% of continent women, urine enters the urethra during increases in abdominal pressure, where it is stopped before it can escape from the external meatus. Perhaps one of the most interesting yet least acknowledged aspects of continence control concerns the coordination of this system. The muscles of the urethra and levator ani contract during a cough to assist continence, and little is known about the control of this phenomenon. That operations cure stress incontinence without altering nerve or muscle function should not be misinterpreted as indicating that these factors are unimportant.     

Urodynamic appraisal of the Marshall-Marchetti test in women with stress urinary incontinence

To determine the reliability of the Marshall-Marchetti test as a diagnostic and prognostic preoperative screening test for stress urinary incontinence, the changes observed in urethral pressure profiles under resting and stressful situations were recorded and compared following varying degrees of elevation of the urethra and the urethrovesical junction. The characteristic similarity of changes was evident in the functional profile length, urethral closure pressure, and cough pressure profile of the urethra during performance of the Marshall-Marchetti test and intentional urethral occlusion. This study clearly invalidated the Marshall-Marchetti test by objectively demonstrating that the Marshall-Marchetti test restored continence under stress of coughing by occluding the urethra and the urethrovesical junction.     

Which placement of the tension-free vaginal tape is more important for urinary continence: midurethral position or bladder neck? Consideration from a case report

The tension-free vaginal tape (TVT) is a well-established surgical procedure for the treatment of female urinary stress incontinence. Midurethral position was thought not to be necessary to achieve continence. But in our study, a patient with stress urinary incontinence was treated with a TVT suburethral sling. The symptoms of stress urinary incontinence still exist after the TVT procedure. With physical treatment and anti-inflammatory treatment, no relief was found. At the 50-day follow-up, the symptoms of stress incontinence worsened. Transperineal three-dimensional ultrasound revealed that the sling migrated from the midurethra to the bladder neck. With adjustment of the sling, the symptom of stress incontinence was improved and no complication was observed at the 6- and 12-month follow-up. Sling migration should be considered in a patient who presents with recurrent stress incontinence at the earlier postoperative period. We think that the midurethral position is necessary to achieve continence.     

Electrical stimulated graciloplasty in the male goat: An animal model for urethral pressure measurement

The feasibility of dynamic urinary graciloplasty as a treatment for incontinence is currently investigated. Therefore an animal model is developed to improve the technique of dynamic urinary graciloplasty. This article is a report of the urethral pressure measurements in the male goat. This study compares the graciloplasty around the bulbous urethra with the graciloplasty around the bladderneck. The male goat as an animal model of urethral pressure measurements is discussed. Under anaesthesia in ten male goats the penile shaft outside the pelvis was dissected. Urethral pressure profilometry was performed. The bulbous urethra was dissected and a split sling graciloplasty was performed around the bulbous urethra. The contralateral gracilis was used for bladderneck graciloplasty. Urethral pressure profilometry was done without and with electrical muscle stimulation. The highest native urethral pressure was 136 cm water at the pelvic outrance. Without stimulation the bladderneck graciloplasty pressure was 97 cm water. The bulbous urethra graciloplasty pressure was 122 cm water. These pressures were not significantly different from the pelvic outrance pressure. With stimulation the highest bladderneck and bulbous urethra graciloplasty pressures were 183 cm water and 294 cm water respectively. The stimulated bulbous urethra graciloplasty pressure was significantly higher than the highest native urethral pressure. In conclusion, the male goat is a suitable animal model for urethral pressure measurement. The highest native urethral pressure is located at the pelvic outrance. A nonstimulated graciloplasty acts like a sling with regard to generated urethral pressure. With stimulation sphincterlike activity of the graciloplasty can be observed. In male goats the graciloplasty around the bulbous urethra is superior to the bladderneck graciloplasty. © 1996 Wiley-Liss, Inc.     

Role of sling integrity in the restoration of leak point pressure in the rat vaginal sling model

PURPOSE: We tested the hypothesis that cutting the sling at its suburethral section does not cancel its anti-incontinence effect. We also examined the long-term effects of the sling on bladder function in a recently validated rat model of vaginal sling. MATERIALS AND METHODS: Stress urinary incontinence was created in 60 female Sprague-Dawley rats by the previously established method of bilateral pudendal nerve transection. Under anesthesia 20 animals received a vaginal sling, 20 received a vaginal sling in which the suburethral portion of the sling was cut immediately after placement and 20 received a sham vaginal sling. Six weeks after the procedures leak point pressure was determined and a cystometrogram was done using anesthesia in each animal via a previously implanted suprapubic catheter. Kruskal-Wallis and pairwise separate rank multiple comparison tests were performed with a significance level of 0.05. RESULTS: The cut and intact slings increased leak point pressure similarly and these values were significantly higher than that of the sham sling (24.9 and 27.9 cm H2O, respectively, vs 20.7, p <0.0001). Peak micturition pressure was not significantly different among the 3 groups, indicating absent bladder outlet obstruction in the sling groups. Bladder compliance was significantly decreased 6 weeks after placement of a cut or intact sling compared with the sham sling (p = 0.007 and 0.05, respectively). CONCLUSIONS: An intact suburethral portion is not a requirement for sling effectiveness in the rat model of stress urinary incontinence. However, the sling procedure decreases bladder compliance. This may explain the observed voiding dysfunction associated with sling procedures.     

Urethral erosion of tension-free vaginal tape presenting as recurrent stress urinary incontinence

The suburethral sling with tension-free vaginal tape (TVT) has become a popular treatment for stress urinary incontinence. Erosion of the mesh into the urethra is rare, usually presenting with hematuria, pain, voiding dysfunction or urge incontinence. A patient with stress incontinence was treated with a TVT suburethral sling. One month later, symptoms of recurrent stress incontinence developed. Cystourethroscopy revealed urethral mesh erosion. Surgical removal involved cystourethroscopic-assisted transurethral resection of the mesh, followed by vaginal dissection and periurethral withdrawal. Urethral mesh erosion should be considered in a patient who presents with atypical symptoms after being treated with a suburethral sling. It is important to obtain a detailed history and have a high clinical index of suspicion for erosion. Careful and comprehensive urethroscopy, in addition to cystoscopy, should be a mandatory part of the TVT procedure. Further study is needed to determine the optimal technique for mesh removal.Abbreviations TVT Tension-free vaginal tape     

Clinical applications of the comprehensive theory of urinary incontinence

Currently, urinary incontinence cannot be treated without taking into consideration the comprehensive theory of urinary incontinence. According to this theory, stress incontinence, urge incontinence and alterations in bladder emptying result from alterations in the elements of suburethral support, ligaments and muscles of the pelvis floor. Alterations in the forces applied by muscles and ligaments to the fascia adjacent to the vaginal wall and the urethra cause the vesical neck and the urethra to open or close. Alterations in the forces applied to the vagina can also cause premature activation of the micturition reflex, triggering involuntary contractions of the detrusor muscle. Knowledge of the anatomic substrate of the upper, intermediate and lower layers of the pelvic floor and of the main pubourethral, urethropelvic and uterosacral ligamentous elements is essential before any surgical approach of incontinence can be attempted. Depending on the location of the fascial or ligamental muscle lesion and of the sensitivity of the local nerve endings, stress incontinence, urge incontinence, altered bladder emptying or combinations of these conditions can develop. There are 6 basic defects which should be systematically investigated: defect in the suburethral support ("Hammock"), tethered vagina syndrome, distended pubourethral ligaments, distended uterosacral ligaments and support of the vaginal apex, lesions of vaginal insertion of pubococcygeal muscles, lesions of the striated muscles of the pelvic floor levator plate.     

Leiomyoma of the female urethra: urodynamic changes after surgical intervention

Leiomyoma of the urethra is a relatively rare condition often presenting as an anterior vaginal wall mass or a mass that protrudes from the urethral meatus. We report on the urodynamic changes after vaginal surgery to remove a suburethral leiomyoma, which protruded from the vaginal orifice resulting in dysuria and dyspareunia. Urodynamic studies before the operation revealed a high detrusor pressure, low maximum flow rate with an elevated post-void residual urine on voluntary voiding, and high resting urethral resistance. Removal of the mass with proper reconstruction of paraurethral support restored normal detrusor pressure, maximum flow rate, and post-void residual, resulting in amelioration of her voiding difficulty and dyspareunia. The operative procedure did not affect leak point pressure and she is free from stress urinary incontinence.