An artificial urinary sphincter (AUS) is a life-changing intervention for men with moderate to severe urinary incontinence. The quality of life improvement has been well described in the literature and are clinically apparent. However, surgical implant and long-term use of an AUS also has multiple risks, the most serious of which is cuff erosion. The only management option for urethral AUS erosion is device explant with repeat placement following a period of observation. Identifying risk factors for AUS erosion and finding strategies to reduce erosion events will help patients receive the benefits of AUS placement while minimizing the risks.

The state of our current knowledge on risk factors and protective maneuvers for AUS urethral erosion is limited to relatively small retrospective series and review of prospectively maintained databases. While some of the data are conflicting and ambiguous, clear trends for risk factors are emerging.

Risk Factors for AUS Erosion

Patient comorbidities including peripheral vascular disease, diabetes mellitus and smoking, all of which decrease microvascular supply to the urethra, have been identified as risk factors for erosion in retrospective studies. Unfortunately, the effect size has been poorly defined and is generally a secondary consideration in the literature to patient surgical and radiation histories.

Prior open urethral surgery has been identified as a risk factor for erosion. Specifically, prior AUS erosion or infection and a history of urethroplasty are predictors of erosion.^1,2 Cuff size, particularly the smallest (3.5 cm) cuff, has also been linked with urethral cuff erosion, and small cuffs are largely avoided in patients with a history of radiation. Results are mixed in nonradiated patients, but there is evidence a 3.5 cm cuff increases the risk of erosion in patients who have been treated with pelvic radiation.^1-3

A history of pelvic radiation, independent of cuff size or placement, is associated with a shorter overall device survival and increased risk of erosion for both an initial and second AUS. In a retrospective review of AUS erosion events, it was shown that the time to erosion was significantly shorter in patients who had been treated with pelvic radiation than those who had not (1.00 vs 3.15 years).⁴ This was corroborated by a recent study, in which it was found that the time to explant of an initial AUS and second AUS was shorter in patients who had undergone pelvic radiation than those who had not. AUS explantation secondary to infection or erosion (vs device malfunction) was higher in patients who had received prior radiation.⁵

Risk Factors for AUS Erosion Are Cumulative

In a multi-institutional study, it was hypothesized that a history of pelvic radiation, recalcitrant bladder neck contracture requiring repeat transurethral interventions, prior urethroplasty, UroLume® stent placement and prior AUS erosion or infection were all risk factors for erosion.¹ The investigators found that when patients had an increasing number of these risk factors, erosion was more likely. Specifically, patients with zero risk factors had a 2.61% likelihood of AUS explant over the study period, while patients with 3 risk factors had a 25% likelihood.

Similar results were found in a single institution study.² When patients had a single risk factor for erosion (history of pelvic radiation, urethroplasty or prior AUS), there was a 34% chance of failure vs a 75% chance when all 3 risk factors were present.

The cumulative effect of risk factors also holds true for a second AUS after initial device complication. The 5- and 10-year revision-free survival of a second AUS falls off precipitously from 83.1% and 73.9% when patients have no risk factors to 63.9% and 44.9% when patients have both a history of pelvic radiation and prior urethroplasty.⁵

The Role of Transcorporal Placement

Men who have had a cuff erode have permanent damage to the urethra that affects the safety and durability of a second device. Transcorporal placement of an AUS, where the tunica albuginea of the corpora cavernosum is interposed between the cuff and thin dorsal urethra, is the most widely adopted approach to mitigate the risk of repeat AUS erosion. This technique is often reserved for the most challenging AUS placements and is used in men with concurrent severe erectile dysfunction. This is particularity advantageous when the urethra is fixed and/or there is a significant concern for compromised blood supply.

A recent study evaluated data from a large single-surgeon series where the transcorporal technique was used for vulnerable urethras, where vulnerable was defined as a history of anti-incontinence procedure or prior urethral reconstruction.⁶ The study noted that the majority of erosions using both the standard and transcorporal technique occur ventrally. This could be interpreted in 2 ways, ie the transcorporal technique was successful at protecting the dorsal urethra in at-risk patients, or the transcorporal technique is superfluous as most erosions occur ventrally, in contrast to the notion that the dorsal urethra is thinnest and thus most vulnerable. The authors concluded that the benefit of a transcorporal approach for at-risk patients was not convincingly shown in their retrospective cohort. When preexisting erectile dysfunction is present, there is little morbidity to a transcorporal approach, and the technique certainly has not been observed to increase risks or compromise continence rates.

Summary of Recommendations

Convincing risk factors for AUS erosion include a history of AUS erosion, prior urethroplasty and pelvic radiation. Small (3.5) cm cuffs should be used with caution and avoided in patients with a history of radiation therapy. It is unclear if a transcorporal technique mitigates the risk of device erosion as it is often reserved for the highest risk patients and only studied retrospectively. Randomized prospective studies are needed in this space to confirm these retrospectively defined risk factors, direct our use of the transcorporal approach and confirm best practice and counsel of our patients.