Since that time, a variety of mechanisms including compression devices have been employed by which to apply passive external urethral compression with male slings.

The oldest compression device referred to as penile clamp was introduced by J.H. Cunningham in 1910 to provide external urethral compression to stop the leakage [16] and is still in use to date for some male patients with urinary incontinence.

The first artificial sphincter was designed by Frederick Foley in 1947. This was still based upon a fixed urethral compression and provides a circumferential urethral compression by applying an inflatable circular cuff to the male urethra. It was a pneumatic clamp and was inflated and deflated manually by pneumatic piston [17]. Later M. Rosen developed an inflatable urethral compression prosthesis in 1976 [18], and Udo Jonas in 1983 described an internal penile clamp which was implanted at the penoscrotal angle and opened for micturition by external pressure from both sides [19].

In the twentieth century, artificial urinary sphincter has enjoyed popularity as a gold standard procedure for male SUI after the prototype of the current AUS was introduced in 1973 by Brantley Scott. Scott’s original design used a fully implantable system composed of an inflation pump, deflation pump, urethral cuff, and a fluid reservoir [20]. There have been many revisions in the design which led to the current model of artificial urinary sphincter implant, AMS 800 with a pressure-regulating balloon, narrow-backed cuff, and scrotal pump with deactivation button.

The rationale for using male urethral slings for post-prostatectomy incontinence is that, unlike the AUS, it provides a minimally invasive surgical option. They are, however, less expensive than AUS devices, and unlike the AUS, slings provide fixed urethral resistance and/or repositioning that potentially enables better physiologic voiding [21]. It also avoids the need for manipulating the device and to provide an alternative surgical option for patients with mild to moderate incontinence or who refuse to have AUS.

There was resurgence in the interest in male sling again in the twenty-first century. The modern male sling has evolved over the past 15 years. This was brought by the need to capture the larger market share in post-prostatectomy incontinence. There were patients who are not severely incontinent and would defer the traditional AUS implantation. It is also believed that these patients with mild to moderate incontinence would benefit from partial compression of ventral urethra provided by a male sling (Fig. 2).

The new male sling was based again on the concept of mechanical compression of the bulbar urethra against the pubic bone. Bone anchors were used to fix the sling to the pubic rami which obviates the need for blind transfer of sutures suprapubically to achieve bulbourethral compression and eliminates any abdominal incision.

The InVance™ (American Medical Systems, Minnetonka, MN) bone-anchored male sling (BAMS) represented a major improvement in technique, minimizing invasiveness via a purely perineal approach; a silicone-coated polypropylene sling is secured to the descending pubic rami using 5 mm titanium bone screws. A disposable battery-powered inserter is used to insert a total of six bone screws which are pre-attached with #1 Prolene suture. The dissection is carried out laterally toward the pubic rami leaving all the tissue over the urethra. Three screws are placed on each side. A 4 × 7 cm silicone-coated polypropylene mesh alone or in combination with dermis as a composite graft is then anchored to the pubic rami which provided the urethral compression. The sling tension is adjusted either by retrograde urethral pressure method or, if the patient is awake, simply by cough method (Fig. 3).

Unlike the AUS that compresses urethra circumferentially (thereby interfering with the venous blood flow and predisposing to urethral atrophy and even erosion), the bone-anchored male sling only compresses the ventral aspect of the bulbar urethra leaving the dorsal and lateral blood flow intact.

The first data concerning this procedure was reported by Madjar et al. in 2001. They reported a short-term continence rate of 86% in a cohort of 16 patients with no complications [22]. This was later popularized by Comiter [23] and Onur et al. [24].

The author reported their experience in both mild to moderate and severe incontinent patients. It was also found that the patient with mild to moderate incontinence (<5 pads) had a significant better outcome compared with those with severe incontinence (>5 pads). The sling failure correlated well with the type of material and severity of the incontinence [24]. Similarly, in a study by Castle et al. in 38 patients, none of the patients with severe incontinence was cured of their incontinence [25].

Similar results with the InVance bone-anchored sling were reported by Rajpurkar et al. who reported overall success rates of 74% and a patient satisfaction of over 70% at a mean follow-up of 24 months [26].

Long-term results with the InVance bone-anchored sling were reported by Carmel et al. [27]. In that report, 45 patients with post-prostatectomy incontinence underwent InVance sling placement along with regular 2-, 6-, and 12-month and yearly follow-up including pad testing, urodynamics, history, and UCLA/RAND and American Urological Association (AUA) symptom score data for a median follow-up of 36 months: 36% of patients were dry, 40% improved, and 24% reported failure. The vast majority of patients (86%) considered themselves cured or almost cured, and 72% were satisfied or very satisfied with the procedure. Complications were temporary perineal numbing sensation lasting 1–3 months in 22%, temporary urinary retention in 7%, overactive bladder in 4%, and mesh infection resulting in removal in one patient.

Similarly, a recent French multicenter study described treatment success and predictors of failure among 84 patients treated for incontinence with InVance male slings. In this study, at a mean of 20 months, 45% of patients were dry, 26% improved, and 29% had treatment failure. Univariate analysis identified three features as predictors of treatment failure: severe urinary incontinence, urodynamic instability, and a history of bimodal therapy for prostate cancer including radiation therapy. Failure rate was 67% if two or more of these factors were present versus 25% if one or none was present (P = .013). Bimodal therapy was the sole independent predictor of failure in multivariate analysis in this study [28].

The author reported their 5-year experience in 87 patients in 2007 and showed only 52.8% were cured and another 25.2% significantly improved of their incontinence, while 21.8% failed the sling procedure [29].

Fischer et al. used a risk analysis model to predict success in 62 men treated for post-prostatectomy incontinence with bone-anchored slings and found that among several factors: time from treatment causing incontinence, age, abdominal leak point pressure, pad weight testing, maximum bladder capacity, detrusor overactivity, International Prostate Symptom Score (IPSS), and urinary distress inventory (UDI-6)], only preoperative pad weight of less than 423 g/day was a predictor of success. Patients with less than 423 g/day leakage had a 71% chance of success and were six times more likely to have success as defined by perception of very much or much better on Patient Global Impression of Improvement (PGI-I) questionnaires [30].

In another study by Comiter, reported complications with bone-anchored male sling were transient retention in 2%, overactive bladder in 5%, mesh erosion in 2%, and infection in another 2%. There was a slightly higher rate of perineal pain in 15% [31].

Whereas bone-anchored male slings function by fixed urethral compression, transobturator slings were subsequently developed based on the concept of proximal relocation of the sphincteric urethra. It was introduced in 2007, the original concept based upon a minimally invasive approach similar to the female mid-urethral transobturator tape (TOT) sling. Rehder and Gozzi described a novel technique for placement of a polypropylene tape beneath the bulbar urethra using the transobturator approach in a series of four cadaveric as well as 20 human male patients [32].

Whereas this sling only compresses urethra minimally, its main mechanism of action relies upon relocation of proximal urethra. It is hypothesized that inefficacious coaptation of the urethral sphincter complex resuls from subluxation of the posterior urethral support [33]. Therefore, a transobturator sling which elevates and relocates the urethra will ultimately prevent proximal urethral descent and improve the coaptation. Following appropriate sling tensioning, the bulbar urethra is relocated proximally by a distance of 2–3 cm into the high-pressure zone in the pelvis, thus functioning as a physiologic “backstop” during straining [34].

The middle part of the tape was fixed distally to the bulb and proximally to the perineal body, and when tension was applied to the ends of the tape, the proximal anterior urethra was relocated proximally by a distance of 3–4 cm, effectively lengthening the membranous urethra. Baseline and postoperative video urodynamics in the clinical series confirmed that at rest, the bladder neck and posterior urethra were more occluded, and the bladder neck was closed and more elevated than at baseline. Additionally, postoperative video urodynamics demonstrated a more elongated membranous urethra during micturition, having increased from a mean of 3 mm to a mean of 17.2 mm following placement of the tape. Urethral pressure profilometry in the same series demonstrated an improvement of supine mean urethral closing pressure at rest from 13.2 cm H₂O preoperatively to 86.4 cm H₂O postoperatively [32].

The rationale for treating post-prostatectomy male incontinence by transobturator tape is based on the theory that post-prostatectomy men with partially intact external sphincteric complexes may develop incontinence due to urethral hypermobility, resulting in urethral subluxation or perineal descent from the pelvis, possibly associated with coexistent levator laxity; hence, proximal relocation of the sphincteric urethra may result in improved continence [32].

The newest version in male sling is the addition of a quadratic sling from Coloplast Corp. It is designed to provide a broad area of urethral compression and to achieve proximal relocation of the membranous urethra. Quadratic fixation is achieved with both transobturator (TO) and prepubic (PP) components. By combining the mechanisms of action of the bone-anchored and the transobturator retroluminal slings, the quadratic device can increase urethral resistance to a greater degree more than either a purely perineal or TO approach. On tightening both arms sequentially, this additive effect has been shown to cause a cumulative increase in RLPP [35, 36]. Because of this feature, it has been proposed to be effective in more severe post-prostatectomy incontinence as compared to other male slings.

Some adjustable slings have also been introduced, but only one of those slings (Remeex) is approved by the FDA in the United States. These slings are again based on the concept of urethral compression.

The Argus sling consists of silicone foam pad placed under the bulbar urethra, attached to silicone columns that are transferred through retropubic or transobturator space and fixed over the rectus fascia using silicone washers [37].