Comparative evaluation of physical characteristics of different inflatable penile prostheses

Penetrative anal intercourse may require high axial loading forces

BACKGROUND

Despite increases in the lifetime prevalence of anal intercourse, little is known about the safety of inflatable penile prosthesis use during anal intercourse or the forces required for anal penetration.

AIM

We sought to determine the force required for anal penetration.

METHODS

A digital force gauge device was secured to a silicone phallus with a length and girth representative of the average male phallus in the United States and inserted into the anal canal of 6 male participants for a total of 5 measurements per participant. The maximum axial forces on insertion were recorded. Participants then completed a survey eliciting demographic information and past experience with receptive anal intercourse.

OUTCOMES

The outcome measure was the force recorded during insertion of a force gauge device into the anal canal.

RESULTS

The median maximal force recorded on anal penetration was 26.5 N (2.7 kg; range: 16.1-51.7 N or 1.64-5.27 kg). Participants who engaged in receptive anal intercourse more than once per month tended to use lesser median maximal forces (25.7 N or 2.62 kg) than participants who engaged less frequently in receptive anal intercourse (41.6 N or 4.24 kg).

CLINICAL IMPLICATIONS

Compared with the forces required for vaginal penetration, anal penetration forces may cause additional mechanical stress to the phallus.

STRENGTHS AND LIMITATIONS

While the study is limited primarily in its small sample size and in the use of a single device for anal penetration with a set size and rigidity, the resulting findings presented here are to our knowledge the first reported data pertaining the force required for anal penetration.

CONCLUSION

As the forces required for anal penetration exceeded those for vaginal penetration, clinicians may need to carefully counsel patients on the safe use of an inflatable penile prosthesis for anal intercourse.

History of penile implants: from implants made of bone to modern inflatable penile implants

Penile prostheses are implantable devices used to definitively treat erectile dysfunction when previous forms of treatment have failed. The first example of a penile implant dates to 1935, when a rib was inserted in a neo-phallus reconstructed after a traumatic amputation. Since then, alternative artificial devices were adopted as penile prosthetic implants. The evolution of prosthetic devices had a dramatic thrust in 1973 when the first inflatable penile prosthesis was worldwide presented. Thanks to advances in device materials, design, surgical implant techniques, and perioperative management, nowadays inflatable penile prostheses are one of the most adopted definitive therapy for patients with drug-refractory erectile dysfunction or refusing alternative forms of treatments. Moreover, the clinical indications for inflatable penile prosthesis have also expanded, including female-to-male transmen or men underwent penile reconstruction due to congenital aphallia or traumatic or surgical penile amputation. In order to summarise the process behind the development and evolution of penile prosthesis, we aimed at performing a historical review of the currently available literature to provide an easy and comprehensive overview of the topic. The understanding of the historical process behind the evolution of inflatable penile prostheses will drive further innovation to increase efficiency and the rate of patients satisfaction.

Safety and Efficacy of Inflatable Penile Prostheses for the Treatment of Erectile Dysfunction: Evidence to Date

Erectile dysfunction (ED) is a common problem, and prevalence rates are expected to rise as life expectancy increases worldwide. In more severe cases of ED, penile prosthesis implantation has been an excellent option for patients. Over the past few decades, significant design improvements have been made to the penile prosthesis and modifications to surgical technique to improve clinical outcomes. The purpose of this review is to summarize the safety and efficacy of FDA-approved penile implants in the US market. Design modifications have greatly improved the safety and reliability of the implant. Development of improved surgical techniques has decreased intraoperative injuries and reservoir-related complications. With its high overall satisfaction rates and low risk of complications, the inflatable penile prosthesis remains an excellent option for patients with erectile dysfunction.

Small Diameter Penile Implants: A Survey on Current Utilization and Review of Literature

Background

Inflatable penile prostheses (IPPs) with smaller diameter cylinders have been in use for over 30 years, yet the literature is sparse on their utilization patterns amongst prosthetic surgeons.

Aim

To understand current usage of small diameter penile implants (SDPI) among prosthetic surgeons.

Methods

IRB approval was obtained to conduct a survey of prosthetic surgeons. A 23-question online survey was distributed via email to physician members of the Sexual Medicine Society of North America (SMSNA) and Society of Urologic Prosthesis Surgeons (SUPS). The survey included questions regarding surgeon experience and volume, frequency of SDPI utilization, indications for SDPI, surgical strategy in the setting of SDPI (approach, use of concordant modeling/grafting), reservoir and pump management, and perceived infection risk and patient satisfaction.

Main Outcome Measure

SDPI were utilized by the vast majority of respondents in certain clinical situations such as corporal fibrosis or anatomically small corpora, and surgeons have had a favorable experience with these as a final destination implant or as a place-holder until reimplantation with a normal diameter device.

Results

Fifty individuals responded to the survey, 48 of whom routinely utilized SDPI. The most common indication for SDPI placement was corporal fibrosis from prior infection, followed by anatomically small corpora and priapism. The most common maximal dilation diameter was 10 mm (47%), an additional 23% of respondents utilized SDPI with 11 mm dilation. 75.4% of respondents sometimes or always intended to upsize to standard diameter cylinders in the future. 68.8% of surgeons routinely counseled patients on the possibility of reduced grith and rigidity with SDPI. Patient satisfaction was perceived to be comparable to standard diameter cylinders in 56.3% of respondents, while the remaining 43.6% believed it to be lower than traditional cylinders. Utilization of SDPI can be an important tool for prosthetic surgeons faced with difficult cases due to corporal fibrosis or small corpora. This survey provides new insight into patterns of SDPI utilization by surgeons. A limitation of the study is that patient satisfaction is indirectly addressed through surgeons’ perception and experience, further research will be necessary to include patient questionnaires regarding device satisfaction.

Conclusion

SDPI are necessary in certain scenarios that preclude the use of normal diameter cylinders. These implants may offer satisfactory erections, but can also be upsized to standard diameter cylinders in the future.

Campbell SP, Kim CJ, Allkanjari A et al. Small Diameter Penile Implants: A Survey on Current Utilization and Review of Literature. Sex Med 2022;10:100458.

Clinical Recommendations From the European Society for Sexual Medicine Exploring Partner Expectations, Satisfaction in Male and Phalloplasty Cohorts, the Impact of Penile Length, Girth and Implant Type, Reservoir Placement, and the Influence of Comorbidities and Social Circumstances

INTRODUCTION

To date, several aspects of inflatable penile prosthesis (IPP) surgical procedure have been poorly studied.

AIM

The aim of this study was to review the evidence associated with IPP implantation and provide clinical recommendations on behalf of the European Society for Sexual Medicine (ESSM). Overall, 130 peer-reviewed studies and systematic reviews, which were published from 2007-2018 in the English language, were included.

METHODS

MEDLINE and EMBASE were searched for randomized clinical trials, meta-analyses, and open-label prospective and retrospective studies.

MAIN OUTCOME MEASURE

The panel provided statements exploring patients and partner expectations, satisfaction in male and phalloplasty cohorts, the impact of penile length, girth and implant type, reservoir placement, the influence of comorbidities, and social circumstances. Levels of evidence were provided according to the Oxford 2011 criteria and graded as for the Oxford Centre for Evidence-Based Medicine recommendations.

RESULTS

In the preoperative setting, it is fundamental to identify and interact with difficult patients with the intention of enhancing the surgeon's ability to establish the surgeon-patient relationship, reduce physical and legal risk, as well as enhancing patient satisfaction. To address this need, the mnemonic Compulsive, Unrealistic, Revision, Surgeon Shopping, Entitled, Denial, and Psychiatric ("CURSED") has been suggested to identify patients who are at high risk of dissatisfaction. The current recommendations suggest improving glycemic control in patients with diabetes. Available evidence suggests evaluating transplant recipients with the criteria of Barry, consisting of stable graft function for >6 months, avoidance of intra-abdominal reservoir placement, and low-dose immunosuppression. HIV status does not represent a contraindication for surgery. Smoking, peripheral vascular disease, and hypertension may be associated with an increased risk of revision surgery. Patients with spinal cord injury may receive IPP. Patients aged ≥70 years, as well as obese patients, can be offered IPP. The IPP implantation can be performed in patients with stable Peyronie's disease. Ectopic high submuscular reservoir placement can be considered as an alternative method.

CLINICAL IMPLICATIONS

There is a relevant lack of high-level data and definite conclusions in certain areas remain difficult to draw.

STRENGTH & LIMITATIONS

All studies have been evaluated by a panel of experts providing recommendations for clinical practice. Because of lack of sufficient prospective data, some of the included studies are retrospective and this could be stated as a limitation.

CONCLUSION

This ESSM position statement provides recommendations on optimization of patient outcome by patient selection, and individualized peri- and intra-operative management. ESSM encourages centers to collaborate and to create prospective, multicenter registries in order to address this topic of increasing importance. Osmonov D, Christopher AN, Blecher GA, et al. Clinical Recommendations from the European Society for Sexual Medicine Exploring Partner Expectations, Satisfaction in Male and Phalloplasty Cohorts, the Impact of Penile Length, Girth and Implant Type, Reservoir Placement, and the Influence of Comorbidities and Social Circumstances. J Sex Med 2020;17:210-237.

Biomechanical Comparison of Inflatable Penile Implants: A Cadaveric Pilot Study

BACKGROUND

Throughout the last decade there has been a growing interest in the biomechanical differences between inflatable penile prostheses (IPPs) and their significance with regard to the patient experience.

AIM

To present our findings assessing the biomechanical properties of IPPs with and without rear tip extenders (RTEs).

METHODS

This is a biomechanical study of the 3 most commonly used IPPs (AMS CX, AMS LGX, and Coloplast Titan) as assessed by column compression, modified cantilever deflection, and 3-point bending methods. The IPPs were surgically placed into 3 fresh cadavers via an infrapubic technique by a single large-volume implanter. A biomechanical evaluation of the properties of each IPP inside the fibroelastic tunica albuginea was assessed in blinded testing, and analyses were based on industry standard methods for assessment.

OUTCOMES

Maximum axial load; kink formation; horizontal stiffness; and resistance to 3-point flexure testing were measured.

RESULTS

At maximum inflation, all 3 implants had similar performance. Differences appear to be most affected by fill pressures. In fact, only the AMS LGX at less than maximum inflation (LTMI) was unable to consistently withstand the roughly 0.9 kg (2 lbs) of pressure for column load testing mimicking vaginal intromission. The Coloplast Titan showed slightly better rigidity than the AMS LGX and CX devices in horizontal load testing, and, with 3-point flexure testing, the CX showed the best rigidity in the shortest phallus (A). Overall, the Titan showed slightly better rigidity in the longest phallus (C) and the phallus with mild Peyronie's disease (B).

CLINICAL TRANSLATIONS

Penile implants with circumferential expansion had higher rigidity on biomechanical testing and should be considered in a patient's decision during selection of a penile implant.

STRENGTHS AND LIMITATIONS

Strengths include blinding of the biomechanical testing and analyses, surgical procedures performed by a highly experienced surgeon, and that this is the "closest to" in vivo evaluation (inside the tunica albuginea) of penile implant function and properties to date. Weaknesses are that this study was performed in cadavers and not in live patients. It also has a small sample size, including the use of only 3 cadavers, and there was no correlation of performance to patient satisfaction.

CONCLUSION

The results of this study support the conclusion that all devices are capable of functionally restoring erectile capacity. However, we observed that, in general, the 2 circumferentially expanding penile prosthesis showed greater resistance in biomechanical testing when compared with longitudinal and circumferential expanding devices. This should be considered as a guide during device selection for a patient undergoing penile prosthesis. Wallen JJ, Barrera EV, Ge L, et al. Biomechanical Comparison of Inflatable Penile Implants: A Cadaveric Pilot Study. J Sex Med 2018;15:1034-1040.

Biomechanical Studies of the Inflatable Penile Prosthesis: A Review

INTRODUCTION

The penile prosthesis remains the primary surgical treatment for refractory erectile dysfunction. Over the decades, inflatable penile prostheses' mechanical reliability, patient satisfaction, safety, and functional erectile restoration have greatly improved. During this time, many studies of biomechanical properties of the prosthesis have been conducted to better understand their biomimicry to the erect human phallus.

AIM

To review all current literature on the biomechanical properties of the penile prosthesis, including prosthesis biomechanical function, and variability in model-related performance.

METHODS

A Medline PubMed search was used to identify all articles of interest related to subjects involving the penile prosthesis and its related biomechanical properties. The following were included in the search for articles of interest: "biomechanics," "mechanics," "mechanical properties," "axial rigidity," "penile implant," and "penile prosthesis." Articles were further screened for content and English language.

MAIN OUTCOME MEASURE

Here we perform a literature review of the bio-mechenical function, performance, and patient satisfaction of penile implants.

RESULTS

Axial rigidity helps determine the ability of an erect penis to complete vaginal intromission and pelvic thrusting without buckling. Recent cadaveric data show that at maximum inflation, Coloplast and American Medical Systems (AMS) implants had comparable performance. Variability was seen at various lower fill pressures, where more severe buckling was observed. Coloplast Titan showed a tendency toward better resistance to longitudinal and horizontal forces. The AMS CX device showed similar performance to the Titan, and the AMS LGX device was shown to be most sensitive to fill pressure variation. Additionally, rear tip extenders (RTEs) appear to negatively affect axial loading, especially in settings of larger implants.

CONCLUSION

Current research suggests that circumferentially expanding devices, such as AMS CX and Coloplast Titan, show better resistance to longitudinal (penetration) and horizontal (gravity) forces and, unlike the AMS LGX device, are less sensitive to device fill pressure. Additionally, RTEs have been shown to negatively impact axial loading, especially in larger cylinder inflatable penile prostheses >20 cm in length. Madiraju SK, Wallen JJ, Rydelek SP, et al. Biomechanical Studies of the Inflatable Penile Prosthesis: A Review. Sex Med Rev 2019;7:369-375.

Implementation of length expanding inflatable penile prosthesis is not sufficient to prevent postsurgical penile shortening

A single armed, prospective, two-center study was conducted with an aim of evaluating the effectiveness of the AMS 700 LGX cylinders in maintaining or increasing penile length postimplantation. The LGX has the unique ability to expand in length with inflation. Only 23.1% (6) of the patients were able to maintain stretched penile length. We now recommend leaving the implant inflated 60%-80% in the immediate postoperative setting for approximately 6 weeks. Then we teach pump training with deflation at around 6 weeks, prior to a maximum inflation protocol daily. Further studies would be required to validate if these interventions have significantly increased the number of patients who maintain or gain stretched penile length.

Penile Size Restoration With Nondegloving Approach for Peyronie's Disease: Initial Experience

INTRODUCTION

The sliding technique (ST), commonly done with a subcoronal circumcising incision with penile degloving, has been used to restore penile size in patients with severe Peyronie's disease (PD) and erectile dysfunction, but with a potential risk of ischemic injury to the glans penis.

AIM

To provide detailed surgical techniques regarding the nondegloving ventral incision and report our initial experience with this approach to perform the ST and penile prosthesis placement in patients with severe PD.

METHODS

This was a retrospective review of patient outcomes after penile prosthesis placement with penoplasty for severe PD and erectile dysfunction from January 2015 to December 2017.

MAIN OUTCOME MEASURES

Primary outcomes included straightening rates, penile measurement, along with immediate and late complications. Secondary outcomes include operative time and overall patient satisfaction.

RESULTS

12 Patients had significant penile atrophy and/or curvature >60 degrees and underwent inflatable penile prosthesis placement with grafting procedure. Significant penile atrophy was determined by a combination of the patient's subjective report and the surgeon's objective assessment through stretched penile length. 7 (58.3%) of those patients underwent ST, of which the last 5 had the procedure performed through a nondegloving ventral incision. Mean degree of curvature prior to ST was 66 degrees (45-90 degrees). Mean penile length gain was 2.6 cm (2.0-3.0 cm). At a mean follow-up of 15.5 months (3-31 months), only 1 patient had minimal residual curvature of 15 degrees. There were no vascular complications.

CLINICAL IMPLICATIONS

This nondegloving technique theoretically maintains blood flow continuity to the glans penis by preserving the continuity of the skin, dartos fascia, and neurovascular bundle.

STRENGTHS & LIMITATIONS

Strengths of this study include the novel nature of this approach, no incidence of vascular complications, and adaptability to other grafting procedures during penile prosthesis placement. Limitations include the use of 5-item International Index of Erectile Function scores to assess preoperative erectile function on PD, small population, longer incision, and a possible steep learning curve.

CONCLUSION

While ischemic complications of ST and penile prosthesis implantation are rare, there are reports of ischemic injury in patients undergoing a subcoronal circumcising incision with penile degloving. The non-degloving technique with ventral incision provides for an alternative method for ST and penile prosthesis placement to maintain dartos and skin continuity to the glans penis while still allowing for adequate surgical exposure. Clavell-Hernández J, Wang R. Penile Size Restoration With Nondegloving Approach for Peyronie's Disease: Initial Experience. J Sex Med 2018;15:1506-1513.