To our knowledge this is the first expanded analysis of the AMS™ 700 CXR penile prosthesis. The advent of narrow IPP cylinders has alleviated but certainly not eliminated the challenge of IPP placement in this difficult population. Our study confirms that the CXR cylinders can be successfully placed in corporal fibrosis patients, with acceptable surgical outcomes. Despite the majority of patients being dissatisfied with penile length and girth, most patients reported acceptable rigidity allowing them to return to being sexually functional.
Pre-operative Considerations
While pre-operative counseling is a critical part of any prosthetic case, it is even more crucial in the setting of corporal fibrosis.6 Patients should understand that the goal of IPP placement is to restore the ability to have penetrative intercourse, not to restore original penis length and girth. We also emphasize the difficulty of cylinder placement in this setting. Patients are advised that they may require a larger – or multiple – incisions to allow corporal dilation and cylinder placement.
All patients at our institution are offered pre-operative therapy with a vacuum erectile device. Negative pressure therapy has been shown to increase corporal blood flow and suppress pro-fibrotic factors.7,8 It may also help reduce corporal shortening and allow maximal cylinder length implantation at the time of surgery.9 In some cases, it may even allow the implantation of standard-size cylinders, obviating the need for narrow cylinders altogether.10 This protocol also directly involves the patient in their pre-operative preparation and helps build a working relationship with their surgeon. In our anectodal experience, by increasing patient “buy-in”, we find patients to subjectively be more engaged in their care and, by extension, more aware of the challenge that corporal fibrosis presents. However, compliance with a pre-operative vacuum erectile therapy protocol is challenging given the high cost of quality vacuum erectile devices and the time commitment required by the patient. While we demonstrate that more patients who used a vacuum erectile device were overall satisfied-neutral in our cohort, this association was not statistically significant (p = 0.10).
Intra-Operative Challenges
Multiple advanced surgical maneuvers have been described to facilitate cylinder placement in the setting of corporal fibrosis.11 Prior studies have shown that proximal fibrosis may be even more pronounced after infection; creation of more proximally located corporotomies may facilitate dilation of these hostile proximal corporal bodies.12-14 In severe cases, extended corporotomies – sometimes extending over half the length of the corpora – may be necessary to allow excavation of the fibrotic cavernosum under vision. When distal fibrosis is severe (as is often the case in ischemic priapism), additional distal corporotomies may be made to allow seating of the cylinder tips appropriately in the glans.12-14
In our own practice, we prefer to start with a longitudinal penoscrotal incision, which allows easier access to the mid- and distal corpora than a transverse incision. We also utilize planned extended corporotomies (3 paired sets of corporotomy sutures rather than 1) in all of these challenging cases to facilitate access to the scarred corpora and allow for corporal excavation as needed. Our threshold is low for using distal corporotomies to decrease the risk of (or to manage) a distal crossover event. Facelift (reverse cutting) scissors are helpful in corporal excavation and may be used to start a channel that can be further widened with the use of Rossello cavernotomes. When blunt dilators are not sufficient, we prefer specialty tools such as the Carrion-Rossello® cavernotomes to allow creation of a functional channel.14
Given the difficulty – and sometimes impossibility – of corporal dilation, it is not surprising that nearly a quarter of patients in our study had corporal measurements that were discordant by over a centimeter. Our goal is to have at least one of the corporal bodies fully dilated both proximally and distally to allow adequate support for the penis and maximize penile length. In cases where one corporal body is not able to be fully dilated, the cylinder is sized to the shorter side, and the length difference made up by using discordant rear tip extenders (Figure 2A).
We have found that using longer RTEs facilitates proper proximal seating of the implant, as this allows the tubing to exit more distally through the corporotomy (Figure 2B). Long RTEs were used more commonly in the CXR group than in those receiving other IPP cylinders. Prior studies have reported on the increased risk of complications with IPP implantation in cases of tissue fibrosis, including corporal perforation, urethral injury, implant infection, and cylinder malposition and erosion.12-14 Determining the true incidence of these complications is difficult given the limited size of published case series and variety of strategies employed during salvage penile implant surgery. In our cohort, a little over 10% of patients experienced complications, including a 6% rate of infection. Two patients also experienced cylinder crossover, which is a testament to the difficulty of dilation in these cases. There were no cases of erosion in our cohort.
With regards to infection, we use the same perioperative antibiotic prophylaxis (1st generation cephalosporin and aminoglycoside) as in virgin cases. We have also begun to utilize commercially available dilute chlorhexidine irrigation (Irrisept, by Irrimax Corporation, Gainesville, Florida) which has been shown to decrease bacterial and fungal colonization of implants in early ex vivo studies.15 Further studies will be needed to see the real-world impact of this new irrigation on infection rates.
Patient-Reported Outcomes
Long-term patient satisfaction has historically been difficult to assess after penile prosthesis, primarily due to lack of extended follow-up. Moreover, questionnaires such as the International Index of Erectile Function (IIEF) and the Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS) are not validated for use after penile prosthesis.15-18 As such most studies – like ours – use non-validated surveys to assess patient satisfaction.
Overall satisfaction in our study was mixed, with only 6 out of the 19 patients (31.5%) reporting being either “very satisfied” or “satisfied” with their implant. In comparison the PROPPER Trial (Prospective Registry of Outcomes with Penile Prosthesis for Erectile Restoration) reported 913/1050 patients (87%) as being “very satisfied” or “satisfied” with any other AMS 700 ™ inflatable implant at one year follow up. Over half of patients surveyed were dissatisfied with penile length and girth after CXR implantation. Among surgeons who routinely place small diameter cylinders, most state that they specifically counsel patients on the possibility of decreased penile girth and rigidity when narrow diameter cylinders are required.19 We found that although patients are dissatisfied with size after CXR, most are satisfied with the rigidity provided. Regardless, we extensively counsel these patients pre-operatively to set expectations with regards to size and functionality of narrow implants.
Given the ability of penile prosthesis cylinders to act as tissue expanders, it is reasonable to consider whether narrower cylinders can be revised to their standard counterparts.20 In a survey of prosthetic urologists, three-quarters of respondents stated they sometimes or always intend to upsize narrow cylinders in the future, while a quarter never plan to upsize.19 The ability to upsize seems to partially rely on the initial insult: mean corporal length improvements of previously infected patients have been reported to increase by 2.2cm by a year after narrow cylinder placement.21 Interestingly, priapism patients did not show a significant increase in length but did show an increase in dilation diameter enough to allow replacement with standard-diameter cylinders.
Despite patients being counseled that they may consider delayed device upsizing, none of the patients in our study has yet elected to pursue this. However, they are advised that any revision is associated with risk of device infection and other complication. We have found that the fibrosis in these patients is so thick that even a narrow device seems to provide adequate shaft girth, even after less than a dozen pumps. Our patients prefer to keep their CXR device in situ as long as it is cycling well and sufficient for penetration. If they experience mechanical failure, they are advised that we will attempt a device upsize at that time.
Limitations
While there are some comparisons made between narrow and standard diameter implants, the main purpose of this study is a descriptive rather than comparative analysis of our experience with the AMS 700 CXR™ prostheses. This study is limited by its retrospective nature and relatively small sample size. Nonetheless, it represents the largest series to date evaluating outcomes after penile prosthesis implantation with narrow cylinders. Given our position as a tertiary referral center (and the nature of penile prosthesis surgery), our study is also limited by lack of long-term follow-up. Some patients elect to follow-up with local urologists and outcomes may not have been adequately captured. Unfortunately, surveys were not performed in a standardized fashion at the time of follow-up visit, and we were not able to contact all patients for phone survey. In addition, the patients within the control group were not surveyed. Multi-center studies using a standardized and validated survey, such as the Satisfaction Survey for Inflatable Penile Implant (SSIPI), would be helpful to provide a more generalized look at patient satisfaction after narrow cylinder implantation.22