Residual penile curvature correction by modeling during penile prosthesis implantation in Peyronie’s disease patients

With the advent of new surgical techniques to treat Peyronie’s disease with concomitant erectile dysfunction, there remains a question of whether manual modeling (MM), an older technique, still has a place in the treatment algorithm within penile prosthesis (PP) surgery. While the implantation of a PP often corrects moderate to severe curvature, penile curvature can remain greater than 30°, even when concurrent MM is performed during prothesis implantation. There are new variations of the MM technique that have been recently utilized in the intraoperative and postoperative setting to achieve penile curvature less than 30° when the implant is fully inflated. The inflatable PP, regardless of the specific model of choice, is preferred over the noninflatable PP when utilizing the MM technique. MM should be the first line of treatment for persisting intraoperative penile curvature after the placement of a PP due to its long-term efficacy, noninvasive approach, and significantly low risk of adverse effects.


INTRODUCTION
Peyronie's disease (PD) is a connective tissue disorder affecting the tunica albuginea of the penis that results in the formation of plaque.This plaque may cause penile curvature, painful erections, and also lead to erectile dysfunction (ED) [1].Nonsurgical management is the first-line therapy for acute phase PD without ED, which is qualified by penile pain, duration of less than 6 months, and evolving curvature [2].Collagenase clostridium histolyticum intralesional injection, where available, is currently the only FDA-approved nonsurgical therapy [3].However, surgical management for severe or refractory PD is the mainstay in treatment [2].Implantation of an inflatable penile prosthetic (IPP) or a malleable penile prosthetic (MPP) is the first-line therapy for patients with PD and medication-refractory ED [4,5].
IPP implantation alone can be curative of PD.Garaffa et al. noted that only 29% of patients required additional curvature procedures after penile prosthetic (PP) placement [6,7].PP placement without manual modeling (MM) can be used to correct penile curvature in patients who have less than a 30°curvature, as the PP alone acts an internal tissue expander to correct the penile curvature over time [7].However, residual curvature may exist after PP placement, and adjunctive intraoperative maneuvers may be necessary to reduce the curvature within normal limits.
If penile curvature exceeds 30°after an IPP implant, MM is the standard of care [7].MM is performed by forcibly bending the inflated erect penis in the direction opposite to the curvature for 90-second intervals for as many cycles as needed to achieve a penile curvature below 15° [6].If MM fails to reduce penile curvature below 30°, more invasive techniques, such as relaxing incision(s), plication, incision/excision, and grafting, may be necessary [8].In order of increasing complexity, these maneuvers may include MM, tunica plication, plaque incision(s), or plaque excision with grafting [2,9].Herein, we discuss the best strategies for penile straightening at the time of IPP placement and establish the role of MM in the surgical management of PD with concomitant ED.

Literature search
A systematic review of the English (only peer-reviewed articles) literature was performed on PubMed to investigate the role of MM in the surgical correction of PD with concomitant ED.Keywords including Peyronie's disease, penile prosthesis, manual modeling, curvature, implantation, penile, erectile dysfunction, IPP, and MPP were used to specify searches.Studies included were not restricted to any time frame.

Development of manual modeling
Dr. Brantley Scott, the inventor of the IPP, first used the MM technique to correct penile curvature after an IPP placement [10]; however, the original PP cylinders did not provide enough rigidity while inflated to withstand the high-pressure forces required for modeling [11,12].It was Wilson and Delk who initially published the MM technique in 1994, wherein 138 PD patients underwent placement of a three-piece IPP with MM [11,13,14].
After placement of the cylinders, closure of the corporotomies, placement of the reservoir, and connection of all components, the prosthesis is inflated to the maximum distention.The tubing outlets connecting both of the PP cylinders to the pump are clamped with rubber shods to prevent back pressure from damaging the pump mechanisms.The shaft of the penis is forcefully bent contralaterally to the penile curve for 90 seconds.The PP device is then inflated to reassess penile curvature after modeling.If penile curvature is still below 30°after one cycle of MM, then one additional MM session is performed for 90 seconds.After a total of two 90-second modeling sessions, the prosthesis is deflated completely.The assistant pulls on the distal guide sutures protruding from the glans as the surgeon reinflates the prosthesis to achieve a rigid erection.This deflation and reinflation reseats the cylinders within the corpora and allows the surgeon to evaluate the curvature of the penis (Fig. 1) [15].
Ninety percent (n = 124) of these patients claimed they were successful with using their prosthesis during sexual intercourse.MM alone was unsuccessful in 11% (n = 8) of these patients.Distal perforation, corporal cavernosal rupture, and erosion occurred in 4 patients [11].
In a different single-center study in 2010, Levine et al. noted a 79% success rate for IPP placement with MM.Nineteen percent had a residual curvature greater than 20°.Eighty-four percent reported postoperative satisfaction.The most common complaint was the loss of penile length [14].Mulhall et al. determined that if the preoperative penile curvature was less than 30°, no additional straightening maneuvers were required.Twelve and a half percent required straightening if the preoperative penile curvature was 31°-45°, 75% required straightening if the preoperative penile curvature was 46°-60°, and 100% required intraoperative adjuvant straightening maneuvers if the preoperative penile curvature was greater than 60° [16].
MM, however, is not successful in every case, as demonstrated in a single-center trial conducted by Kadioglu et al.Straightening of the penis was accomplished by IPP implantation alone in 35% (n = 21) of patients.An additional 30% (n = 30) had successful straightening by MM.Thirty-three and one-third percent (n = 20) were unsuccessful in MM alone and underwent successful incision of the plaque and grafting.Patient satisfaction scores were also tracked during this study.For the MM only group, 83% rated their satisfaction level as excellent, 5.5% rated their satisfaction as satisfactory, and 11.1% rated their satisfaction as poor [17].
Wilson et al. followed PD patients who received MM during IPP placement for up to 12 years.Of the 104 PD patients who received an IPP implant with MM, there were 24 (23.1%)cases of IPP failure of any type.Of those failures, 5 became infected, 5 failed for iatrogenic causes, and 13 patients underwent mechanical revisions.Remarkably, patient dissatisfaction was extremely low, with only 1 patient expressing dissatisfaction in a long-term follow-up.Importantly, there was no statistical difference between the modeling and nonmodeling group in infections, failure due to iatrogenic causes, and mechanical revisions.PD patients who received IPP with modeling did not have a difference in long-term device failures requiring revision, as compared to patients who received IPPs without modeling.Additionally, none of the 104 patients needed reoperation for additional straightening.This paper establishes a long-term safety profile for MM, as modeling appears to provide permanent straightening without an increase in revisions [15].
Novel techniques have been introduced as adjuvant treatment options for residual penile curvature after an IPP placement.Tausch et al. described an intraoperative decision-making algorithm that involved plication sutures before an IPP placement with high (95%) patient satisfaction scores [18].Chung et al., who utilized penile plication prior to IPP placement, documented significant improvement to an average of less than 5°of penile curvature.Of 18 patients who completed a 11-month postoperative questionnaire, 15 reported that their penile curvature was adequate for sexual intercourse and reported an improvement in their overall condition [19].The scratch technique, which was also described, provided a postoperative straight penis with a reduced chance of urethral perforations [20].These newer techniques may be more efficacious for cases of severe penile curvature, as compared to MM.
Optimal modeling: updated method to eliminate curvature during IPP implantation A recent publication reported that "optimal modeling" should be applied to moderate to severe penile curvatures to potentially circumvent the need for more complex and time-consuming procedures [2].Optimal modeling is performed by forcibly bending the inflated erect penis in the direction opposite to the curvature while maintaining glandular pressure to prevent urethral injury.This practice is different from the original modeling technique published by Wilson et al. in 1994, as optimal modeling utilizes as many 90-second cycles as is necessary.Optimal modeling also includes applying significant manual pressure to the distal urethra at the fossa navicularis to prevent the feared complication of urethral perforation.Modeling is performed in 90second intervals for as many cycles as needed to achieve a curvature less than 15° [11].Lucas et al. corroborated this technique in a study in which 40 PD patients had a preoperative mean curvature of 47.8°and a postmodeling mean curve of 10.6°, with no urethral nor prosthetic complications [6].
The utilization of an IPP may be more efficacious than a MPP implant for the treatment of PD.In a 2011 study, Garaffa et al. documented that modeling significantly improved straightening when performed on an IPP (84%) rather than with a MPP (54%) [7].In addition, an IPP may be preferred due to its close replication of normal penile function, with states of being flaccid and erect when the patient chooses.Therefore, the optimal modeling technique should, in theory, use an IPP to improve outcomes.In contrast, MPP implants may have the unintended consequence of deviation of the glans penis.Ghanem et al. conducted a study in which 20 patients with PD underwent a MPP placement.While the authors concluded that MPPs are safe and effective for the treatment of PD with concomitant ED, there were 7 (35%) cases with persistent deviation of the glans penis.Two of the 16 patients (12.5%) who returned for a follow-up visit reported dissatisfaction due to the deviation of the glans penis [21].
The choice of IPP models makes no difference in outcomes in regard to straightening of the penis for PD patients undergoing prosthesis surgery.Chung et al. compared the AMS 700 CX (Boston Scientific, Marlborough, MA) and Coloplast Titan (Coloplast Corp., Minneapolis, MN) three-piece implants with MM.They observed no Fig. 1 Penile curvature of 90°was appreciated prior to IPP implant (left picture).Placement of an IPP corrects penile curvature to 45°( middle picture).After two 90-second modeling cycles, there was a 10°bend in the erect penis (right picture).Reproduced with permission (Steven K. Wilson, Surgical Techniques: Modeling Technique for Penile Curvature, Journal of Sexual Medicine, Volume 4, 2007, Elsevier).statistically significant difference between the two IPP in terms of mechanical revision (6% revision rate in both devices), cylinder failure rates, and patient satisfaction (Table 1) [22].
The two piece is a favorable IPP option for patients with significant retropubic scarring from previous surgical procedures and for patients who have limited manual dexterity.Levine et al. determined from a validated questionnaire that the satisfaction and rigidity of the two-piece AMS Ambicor (Boston Scientific, Marlborough, MA) was comparable to its three-piece counterpart.Since the two-piece PP holds a lower water reservoir volume when deflating and inflating the device, there is hesitation from the Urology community to utilize the two-piece IPP, as it is considered to have less rigidity and less flaccidity compared to a three-piece IPP [23].In a different study, Levine et al. demonstrated that the Ambicor two-piece IPP had similar rates of complications and overall satisfaction compared to the three-piece IPP (Coloplast & Boston Scientific) [14].
Home modeling has the potential to ameliorate residual curvature after surgery.In a study of 92 patients who underwent IPP implantation with MM, Moncada et al. explored the efficacy of home modeling for patients with a postoperative curvature below 45°.Four weeks after IPP surgery, patients were instructed to follow the home modeling protocol every day for 6 months.This protocol consisted of fully inflating the IPP then gently bending the penis in the opposite direction of the curvature and holding this stretched position for 30 seconds before deflating the IPP.This 20-minute cycle was performed 3 times a day.After 6 months, 94.7% (n = 72) of those who followed the protocol had a penile curvature below 10°.Therefore, home modeling, in conjunction with MM during surgery, is an efficacious technique to reduce penile curvature without the need of more invasive or revisionary surgeries [24].

DISCUSSION
Implantation of a PP has become the gold standard of care for men with PD and concomitant ED.While the implant action of PPs is often curative for PD and ED, intraoperative adjuvant procedures may be necessary.If the penile curve is greater than 30°after an IPP placement, a modeling procedure should be the next step by the implanting surgeon.If the curvature remains over 30°, then a relaxing incision(s) and incision/excision of a solidified plaque may be necessary.In the rare case that the plaque defect is greater than 2 cm, penile grafting is warranted.However, MM has been documented to improve severe penile curvature and should be utilized first to avoid more invasive, time-consuming procedures, such as plication, incision/excision, and grafting.

Table 1 .
Success rates of manual modeling and satisfaction rates among patients receiving an IPP..J. Conlon et al. 23.Levine LA, Estrada CR, Morgentaler A. Mechanical reliability and safety of, and satisfaction with the Ambicor inflatable penile prosthesis: results of a 2 center study.J Urol. 2001;166:932-7.24.Moncada I, Krishnappa P, Ascencios J, Lopez I, Martinez-Salamanca JI.Home modeling after penile prosthesis implantation in the management of residual curvature in Peyronie's disease.Int J Impot Res.2021;33:616-9.
a No statistical difference.W