Current and emerging treatment options for Peyronie’s disease

Abstract

Peyronie’s disease (PD) is a condition of the penis, characterized by the presence of localized fibrotic plaque in the tunica albuginea. PD is not an uncommon disorder, with recent epidemiologic studies documenting a prevalence of 3–9% of adult men affected. The actual prevalence of PD may be even higher. It is often associated with penile pain, anatomical deformities in the erect penis, and difficulty with intromission. As the definitive pathophysiology of PD has not been completely elucidated, further basic research is required to make progress in the understanding of this enigmatic condition. Similarly, research on effective therapies is limited. Currently, nonsurgical treatments are used for those men who are in the acute stage of PD, whereas surgical options are reserved for men with established PD who cannot successfully penetrate. Intralesional treatments are growing in clinical popularity as a minimally invasive approach in the initial treatment of PD. A surgical approach should be considered when men with PD do not respond to conservative, medical, or minimally invasive therapies for approximately 1 year and cannot have satisfactory sexual intercourse. As scientific breakthroughs in the understanding of the mechanisms of this disease process evolve, novel treatments for the many men suffering with PD are anticipated.

Keywords:

• oral therapy
• intralesional treatment
• topical therapy
• extracorporeal shockwave therapy
• traction devices
• plication
• incision and grafting
• penile prosthesis

Introduction

Peyronie’s disease (induratio penis plastica; PD) is a condition of the penis, characterized by the presence of localized fibrotic plaques in the tunica albuginea and affecting 3.2–8.9% of the adult male population.^1–3 The true prevalence of PD may be even higher as many patients are reluctant to discuss their condition with a physician or may not seek medical help if the symptoms are not disabling.⁴ At present, most authorities support the hypothesis that PD generally arises from repetitive (micro)trauma to the erect penis during sexual activities. However, not all penile trauma leads to the development of PD. Abnormal wound healing appears to be more common in men with PD and there is evidence for a genetic predisposition.⁵ Furthermore, studies have shown that risk factors for atherosclerosis and endothelial dysfunction such as hypertension, dyslipidemia, diabetes mellitus, and smoking are more common in men with PD.^6–8

The underlying etiology of PD appears to be an imbalance between profibrotic and antifibrotic substances. Profibrotic substances include transforming growth factor β-1 (TGF-β1), fibrin, plasminogen activator inhibitor-1, and tissue inhibitors of metalloproteinases, and are found to be overexpressed or aberrantly expressed.⁹ Antifibrotic substances include matrix metalloproteinases, which are a class of molecules responsible for collagen degradation.¹⁰ The wound healing cascade begins with exposure of platelets to collagen and the release of chemoattractant molecules such as TGF-β1, platelet-derived growth factor, tumor necrosis factor-α, interleukin-1, and fibrin, which act as a matrix for repair.⁹ Inhibition of the fibrinolytic system or an inability to degrade the intravasated fibrin leads to its persistence in the tunica and continues to exert a proinflammatory response.¹¹ This response ultimately leads to the formation of a palpable plaque secondary to the excessive deposition of collagen and extracellular matrix, with disorganization of collagen fibers and loss of elastic fibers.¹¹ There are other theories on plaque formation which include cytokine and/or growth factor overexpression and free radical production.¹²

PD usually presents in men aged 40–70 years and has two phases. The acute phase, lasting for 6–18 months, is often characterized by the development of penile curvature and onset of pain with erection. The acute phase is followed by a chronic phase, characterized by negligible penile pain, and the establishment of a stable penile abnormality.⁶ Patients presenting with PD can exhibit any single or combination of penile plaque, curvature, pain, and erectile dysfunction (ED). Plaques are typically located on the dorsal or lateral aspect of the penis, causing an upward or lateral defection during erection. As many patients are embarrassed by or unaware of their PD, they are unlikely to mention the topic unless specifically questioned by a treating physician.¹³ PD is generally a progressive disorder that uncommonly resolves completely. It is difficult to predict an individual’s prognosis at the initiation of the disease. Only penile pain, if present, resolves spontaneously within the first year in the majority of patients.¹⁴ In most circumstances, PD progressively worsens over time, as reported in 48% of men with PD in a recent study.¹⁵ Two-thirds of patients with PD are likely to have risk factors for arterial disease and therefore will develop ED over the long term.⁸ Treatment options are chosen based upon disease severity, patient preference, and surgeon’s training. Options include oral medications, intralesional injection therapy, plication procedures, incision and grafting, and placement of a penile prosthesis with or without manual modeling or other ancillary straightening techniques.²

Nonsurgical treatment of PD

Numerous nonsurgical treatment options have been utilized since PD was first descriptively named in 1743. The majority of studies evaluating oral medications lack controls or an adequate number of subjects, are of short duration, and focus on reduction of deformity as the critical measurement of outcome.¹⁶ Despite various reports in the literature of deformity stabilization and/or reduction outcomes, recent guidelines indicate that the available evidence shows generally no significant benefit from oral therapies for reducing penile deformity.^16,17 However, the standard of care still involves an initial trial of either oral or intralesional treatment at first presentation.¹³ An accepted goal of medical therapy is to shorten the acute phase of PD in order to stabilize the plaque or diminish disease progression.¹⁸

Oral therapy

Vitamin E (tocopherol)

Vitamin E is a fat soluble natural antioxidant that theoretically plays a role in DNA repair.¹³ Its antioxidant properties have been hypothesized to inhibit nitric oxide synthesis as well as oxygen free radical-induced fibrosis in human cavernosal cells.¹⁹ Despite double-blind, placebo-controlled, randomized studies showing no significant improvement, tocopherol remains the most common nonsurgical therapy because of its safety, availability, and low cost.^20,21

Potassium para-aminobenzoate (Potaba®)

Potassium para-aminobenzoate was first introduced in 1959 as an oral therapy for PD after it was shown to decrease collagen production in vitro when added to fibroblast cells.²² Its hypothesized mechanism of action involves the enhancement of three endogenous antifibrotic processes: oxygen uptake, glycosaminoglycan secretion, and monoamine oxidase activity.²³ Two double-blind, placebo-controlled, randomized studies evaluating the efficacy of Potaba have been published. Shah et al in 1983 reported improvement of symptoms, particularly pain, when compared to placebo; however, these findings were not statistically significant.²⁴ In a more recent study in 2005, Weidner et al published results that demonstrated significant stabilization of preexisting penile deviation and reduction of plaque size, but no significant reduction of pain or preexisting curvature.²⁵ Potaba is currently a first-line therapy for PD because of its tolerability and availability.²³

Colchicine

The mechanism of action of colchicine remains unknown but it is hypothesized to reduce lactic acid production, which decreases uric acid deposition and decrease collagen synthesis.¹³ Akkus et al demonstrated a reduction in plaque size, degree of curvature, and pain symptoms in response to colchicine therapy.²⁶ In another uncontrolled study, Kadioglu et al demonstrated that the efficacy of colchicine increases when used in specified patient groups without any vascular disease risk factors, presenting in the first 6 months of disease, a degree of curvature less than 30 degrees, and without ED.²⁷ A recent nonrandomized study demonstrated that using tocopherol with colchicine in the early stages of PD reduced plaque size, curvature, and pain.²⁸ A recent study by Akman et al retrospectively evaluated patients that were treated with colchicine in the acute phase of PD. They found that the predictive factors for curvature alterations in PD patients were mild deformities mainly in those with lateral curvature, which mostly shifted to the dorsal side after treatment.²⁹ However, another double-blind placebo-controlled study by Safarinejad demonstrated no difference in pain relief, plaque size, or penile curvature.³⁰ Further studies are necessary to clarify the beneficial effects of colchicine in the treatment of PD. The side effects include nausea, vomiting, and diarrhea.¹³

Tamoxifen

Tamoxifen is a nonsteroidal antiestrogen. Its mechanism of action is unknown but it is hypothesized to modulate TGF-β1, which reduces fibrosis.¹³ Two uncontrolled studies, Apaydin et al in 1998³¹ and Ralph et al in 1992,³² reported a decrease of plaque size, penile deviation, and pain. However the results of a double-blind, placebo-controlled randomized study done by Teloken et al reported that the effect on curvature, plaque size, and pain was not significant.³³ In the absence of a demonstrable benefit, this drug is not routinely recommended for the treatment of PD.

L-carnitine

L-carnitine’s mechanism of action is not fully understood but it is hypothesized to increase mitochondrial respiration, which decreases free radical formation.³⁴ Biagiotti and Cavallini performed a double-blind, randomized study in 2001 that compared acetyl-L-carnitine with tamoxifen, which was previously shown to have no benefit over placebo, and demonstrated that acetyl-L-carnitine was more effective in reducing pain and disease progression.³⁵ Cavallini et al in 2002 compared the efficacy of oral propionyl-L-carnitine or tamoxifen combined with intralesional verapamil injections. They demonstrated that the combination of propionyl-L-carnitine and verapamil was efficacious and suggested it as the treatment of choice for advanced PD.³⁶ Another doubleblind, placebo-controlled, randomized study by Safarinejad et al in 2007 found that oral propionyl-L-carnitine treatment was not superior to placebo.²⁰ It is possible that an insufficient dose of this agent was used in light of a recent review suggesting that the minimum dose necessary for an effect was at least 3–3.5 g per day.³⁷ The drug has a relatively safe profile, with reported side effects of mild euphoria and gastrointestinal upset.³⁴

Pentoxifylline

Pentoxifylline is a nonspecific phosphodiesterase inhibitor with a hypothesized mechanism of action of upregulating cyclic adenosine monophosphate and decreasing type I collagen production, which remedies the abnormal collagen phenomenon.³⁴ Valente et al in 2003 collected data from in vivo and in vitro models that demonstrated decreased levels of profibrotic factors and plaque size after treatment with pentoxifylline.³⁸ Other studies document that pentoxifylline reduced calcium content in the plaque and collagen fiber deposition and altered elastogenesis by antagonizing the effects of TGF-β1.^39–41 Safarinejad et al conducted a doubleblind, placebo-controlled, randomized study that reported a significant effect of pentoxifylline therapy on reducing penile curvature and plaque volume particularly in patients in the early stages of established PD.⁴² These somewhat promising results with pentoxifylline need further confirmation. This drug is associated with relatively mild side effects, most commonly nausea, dizziness, and headache.³⁴

Phosphodiesterase type 5 (PDE5) inhibitors

PDE5 inhibitors have been shown to decrease oxidative stress-associated inflammatory changes, as observed in the pathophysiology of PD. Its mechanism of action results in an increase of cavernosal smooth muscle levels of cyclic guanosine monophosphate. PDE5 inhibitors, when given continuously over long periods, induce an elevation of nitric oxide and cyclic guanosine monophosphate which act as antifibrotic agents to reduce collagen deposition, profibrotic factor release, oxidative stress, and myofibroblast numbers.¹¹ Levine and Latchamsetty demonstrated that sildenafil was a safe, effective, and well-tolerated first-line therapy for PD patients with ED.⁴³ In another study by Levine et al, sildenafil reduced the incidence of postoperative ED in patients who underwent surgical correction of PD using pericardial grafting after plaque incision. However these results were not statistically significant.⁴⁴ Valente et al performed a study in a rat model with a PD-like plaque induced by TGF-β1, demonstrating that sildenafil caused a reduction in plaque size.³⁸ Ferrini et al performed a similar rat model study with a PD-like plaque elicited by TGF-β1 or fibrin injection into the tunica albuginea. Long-term oral treatment with vardenafil slowed and reversed the early stages of the PD-like plaque in this rat model.⁴⁵ Chung et al reported septal scar resolution and improved International Index of Erectile Function-5 questionnaire symptom scores in a study with low-dose daily tadalafil.⁴⁶ Palmieri et al concluded that extracorporeal shockwave therapy (ESWT) in addition to 5 mg of tadalafil once daily produced significant improvement in erectile function and quality of life for patients with PD and ED.⁴⁷ Further studies are mandated before any of these methods of treatment can be recommended.

The oral pharmacotherapies as evaluated by randomized controlled trials are summarized in Table 1.

Table 1 Efficacy of oral therapy evaluated by randomized trials

Treatment	Study	Mode of study	Effect
Vitamin E (tocopherol)	Safarinejad et al^Citation20	Placebo-controlled, double-blind	No significant difference
Potaba®	Shah et al^Citation24	Placebo-controlled, double-blind	No significant difference
	Weidner et al^Citation25	Placebo-controlled, double-blind	Decreased plaque size in treatment arm
Colchicine	Safarinejad^Citation30	Placebo-controlled, double-blind	No significant difference
Tamoxifen	Teloken et al^Citation33	Placebo-controlled, double-blind	No significant difference
L-carnitine	Biagiotti and Cavallini^Citation35	Double-blind	Decreased plaque size, curvature, and penile pain
Pentoxifylline	Safarinejad et al^Citation42	Placebo-controlled, double-blind	Decreased penile curvature and plaque volume in early chronic Peyronie’s disease

Intralesional injection therapy

Corticosteroids

The mechanism of action of corticosteroids was hypothesized to inhibit phospholipase A2 and suppress immune response.⁴⁸ Historically, the first documented use of intralesional corticosteroids for PD was reported by Bodner et al in 1954, which noted a decrease in plaque size and penile pain following therapy.⁴⁹ Follow-up studies demonstrated that corticosteroid injections had no therapeutic benefit,^50,51 as seen in the single-blinded, placebo-controlled, randomized study performed by Cipollone et al in 1998, which showed no statistically significant benefit.⁵² Lack of evidence for benefit and side effects such as local tissue atrophy, fibrosis, and immune suppression currently limit the clinical use of this option. Therefore corticosteroid injections are not currently recommended as an intralesional therapy for PD.²³

Collagenase

Collagenase, also classified as specific matrix metal loproteinase-1, 8, and 13, degrades interstitial collagens, specifically type II collagen.¹³ The therapeutic potential of collagenase was initially introduced more than two decades ago in both in vitro and in vivo studies by Gelbard et al.^53,54 These researchers utilized highly purified clostridial collagenases to test their effect on various human tissues in vitro, including human pericardium, human corpus cavernosum, tunica albuginea, and PD plaques. These experiments with collagenase resulted in a remarkable reduction in the size of the PD plaque, along with microscopic fraying and dispersal of collagen bundles, when compared with plaques injected with normal saline. Moreover, elastic fibers, vascular smooth muscle, and axonal myelin sheaths were not affected by collagenase application.⁵³ In the following period, the investigators performed an in vivo pilot study that injected intralesional collagenase in 31 men with PD.⁵⁴ After 4 weeks of treatment, 65% of patients exhibited objective improvement, 93% reported elimination of pain, and intercourse was restored in 75% of patients. Additionally, the researchers noted that penile plaques were either significantly altered or disappeared in four patients and reduced by 20%–100% in 16 others. Studies have reported that immunoglobulin G antibodies to collagenase were higher in men with PD versus healthy men, implying that intralesional collagenase has a documented benefit.⁵⁵ A double-blind, placebo-controlled, randomized study demonstrated a significant response with collagenase injections in patients with small plaques and minor penile deformity.⁵⁶ Although not placebo-controlled, a recent study employing two intralesional collagenase injections within 24–72 hours over three injection cycles demonstrated improvement with decreases in both plaque size and penile curvature in men with PD.⁵⁷ Collagenase can be used in both the acute and chronic phases of PD. Because of its potential efficacy, intralesional collagenase has just completed phase III clinical trials in men with PD. Collagenase is associated with minimal adverse side effects such as injection site pain, ecchymosis, and rarely corporal rupture.^13,23

Verapamil

Verapamil is a calcium channel antagonist that augments collagenase activity, increases cytokine expression associated with early inflammation and wound formation, and inhibits in vitro fibroblast proliferation in PD plaques.^58,59 Levine et al in 1994 reported that intralesional verapamil injection resulted in a significant reduction in penile curvature.⁶⁰ Additional uncontrolled studies have reported a decrease in penile pain, curvature, deformity, an increase in girth and rigidity, improved erectile function, and subjective softening of the plaque.^61,62 Rehman et al performed the only randomized placebo-controlled study in 1998 with verapamil injection therapy and demonstrated that there was no statistically significant change in penile curvature reduction.⁶³ Because only one study evaluating the efficacy of verapamil included a placebo arm, more controlled studies are required. Verapamil remains a relatively safe and inexpensive form of therapy with minor adverse effects such as nausea, lightheadedness, penile pain, and ecchymosis.²³

Interferons

Interferons are cytokines that play a regulatory role in the inflammatory response of the immune system. Interferon-α-2b inhibits the proliferation of fibroblasts, increases collagenase activity, decreases collagen production, and has been used in a number of studies for intralesional injection treatment of P D. ¹⁸ Initial in vitro studies demonstrated the inhibitory role of interferon-α and interferon-β on collagen production in fibroblasts derived from Peyronie’s plaques.⁶⁴ Since then, several studies confirmed the beneficial effect in men with PD.^65–68 Two single-blind, placebo-controlled studies showed a statistically significant benefit of interferon-α-2b with improvements in penile curvature, plaque size and density, penile pain on erection, erectile function, and penile hemodynamics. This therapy is associated with minor side effects such as sinusitis, minor penile swelling with ecchymosis, and flu-like symptoms of fever, chills, and arthralgia.^69,70 The use of over-the-counter anti-inflammatory agents prior to intralesional injection can abrogate the flu-like such effect.

Randomized controlled intralesional therapy studies are summarized in Table 2.

Table 2 Efficacy of intralesional therapy evaluated by randomized trials

Treatment	Study	Mode of study	Effect
Corticosteroids	Cipollone et al^Citation52	Placebo-controlled, single-blind	No significant difference between treatment and placebo
Collagenase	Gelbard et al^Citation56	Placebo-controlled, double-blind	Decreased curvature and plaque size
Verapamil	Rehman et al^Citation63	Placebo-controlled, single-blind	No significant difference between treatment and placebo
Interferons	Judge et al^Citation69	Placebo-controlled, single-blind	Significant improvement in penile curvature, plaque size, penile pain, and erectile function
	Hellstrom et al^Citation70	Placebo-controlled, single-blind

Topical therapy and iontophoresis

Aminopropionitrile, hydrocortisone, and verapamil are topical medications with varying results in the treatment of PD.^71–74 Iontophoresis is the utilization of electrokinetic transport of charged molecules for the enhancement of transdermal drug delivery to diseased tissue, particularly plaques in PD.⁷⁵ Martin et al demonstrated that topically administered verapamil gel was not present in the tunica albuginea at excisional surgery the next day,⁷³ but was detected to a small degree in PD plaques after iontophoresis.⁷⁶ In spite of initial successful reports with iontophoresis of dexamethasone and verapamil,^77–79 recent double-blind placebo-controlled randomized trials failed to demonstrate statistically significant improvements in penile curvature. Greenfield et al suggest iontophoresis in patients whose major complaint is pain or those who have mild penile curvature and do not wish to undergo intralesional therapy or surgical correction of their penile curvature.⁸⁰

Extracorporeal shockwave therapy (ESWT)

Penile ESWT has been proposed as a possible nonsurgical PD treatment, but few reports have reported any beneficial effects.^81,82 Most studies did not observe any significant improvement in penile curvature.^83–85 An exploratory meta-analysis in 2004 by Hauck et al did not reveal any significant benefits of ESWT on improvement of penile curvature or plaque size.⁸⁶ Two double-blind, placebo-controlled, randomized trials have been published. Chitale et al did not observe any significant benefit of ESWT on PD.⁸⁷ Palmieri et al demonstrated that ESWT appears to expedite pain resolution compared to the natural course of the disease.⁸⁸ Currently, ESWT is not recommended as a treatment for PD because it has not been shown to improve or even stabilize the plaque or penile curvature.⁸⁹

Penile traction devices

Gradual expansion of tunica tissue by traction exerted by a penile extender device induces new connective tissue formation.⁹⁰ Preliminary studies conducted by Levine et al and Gontero et al have demonstrated nonsignificant curvature reduction and increased penile length.^91,92 Further long-term controlled studies are necessary. Raheem et al suggested that vacuum pump therapy may have similar effects on improving penile curvature and pain symptoms.⁹³

Surgical options for PD

The ideal candidate for surgical intervention for PD is a patient whose plaque has stabilized (normally at least 12 months since diagnosis) and penile curvature prevents satisfactory sexual intercourse. Attempts at medical management are attempted initially but, with more severe curvature – normally greater than 60 degrees – surgery may be considered as a primary treatment. Concomitant ED is always evaluated when deciding on surgical options for patients with severe PD.⁹⁴

A proposed treatment algorithm for PD is provided in Figure 1.

Figure 1 Algorithm for treatment of Peyronie’s disease.

Abbreviations: U/S, ultrasound; VED, vacuum erection device.

Penile plication

For a patient with less severe penile curvature, one option includes shortening the side directly opposite to the curvature to equalize in length both sides of the penis. The ideal candidate for this is a man with adequate penile length, curvature less than 60 degrees, good preoperative erectile function, and no hourglass defect.⁹⁵ In one study, patients underwent penile plication and greater than 80% of participants agreed that their residual curvature was decreased to less than 20 degrees and their rigidity was equivalent or better than before the procedure. The intuitive common complaint with this procedure is loss of penile length. Such men had their penile length measured before and after the procedure, with a surprising overall length change of +0.6 cm.⁹⁶

Tunica albuginea plication can be performed using a variety of techniques. The Yachia procedure involves degloving the penis and making a longitudinal incision in the tunica albuginea opposite the plaque.⁹⁷ The edges are then brought together horizontally using sutures which shorten the unaffected side and overall straightening of the penis.⁹⁸ The Essed–Schroeder technique doesn’t involve entry or violation of the venoocclusive mechanism; instead sutures are placed in the tunica albuginea and tightened to effectively plicate and straighten the penis.^97,99 Overall, success rates of plication procedures range from 70%–100% with rates of patient satisfaction typically over 80%.^96,100–109

Data published about plication techniques are summarized in Table 3.

Table 3 Data published on plication techniques

Author	Date of Publication	Patient #	Procedure Type	% Straight	% with ED	Diminished Sensation%	Mean follow up duration (months)
Ralph et al^Citation103	1995	359	Nesbit	89	2	2	Not reported
Daitch et al^Citation101	1999	183	Modified corporoplasty	89	4	Not reported	24.1
Gholami et al^Citation104	2002	132	16-dot plication technique	85	3	Not reported	31
Syed et al^Citation105	2003	50	Nesbit	90	Not reported	21	84
Savoca et al^Citation106	2004	218	Nesbit	86.3	13	11	89
Rolle et al^Citation107	2005	50	Nesbit	100	0	Not reported	Not reported
Bella et al^Citation108	2006	23	Minimally invasive plaque excision	91	Not reported	4	25
Greenfield et al^Citation109	2006	68	Tunica albuniea plication (modified Nesbit)	99	7.3	4	29
Taylor et al^Citation96	2008	90	Tunica plication	93	12	36	72

Incision and grafting procedures

A more invasive approach involves incising the plaque to release penile curvature and using a graft to augment the missing tunica albuginea. Patients with extensive curvature (greater than 60 degrees), multiple areas of plaque, or those without adequate penile length are candidates for incision and grafting. Similar to penile plication, the penis is degloved exposing Buck’s fascia. The fascia is then entered, avoiding the dorsally located neurovascular bundles. Peyronie’s plaques have a firm texture due to fibrotic changes and can be easily distinguished from the surrounding tunica albuginea. An artificial erection is induced and over the area of the plaque a Y-type or H-type incision is made for tunical release. The tunical defect is then measured and a graft is constructed 10% larger to accommodate possible graft contracture during the healing process.¹¹⁰ The graft is sutured into the defect in a watertight manner and Buck’s fascia is then reapproximated. A final artificial erection is induced to assess for potential vascular leakage. The circumcision is closed in a routine fashion with a mild compression dressing. Most procedures are done on an outpatient basis.

Postoperatively, patients may be advised to use a penile stretching device on a daily basis, possibly with oral medications such as a low-dose PDE5 inhibitor.^13,91,111 The use of a PDE5 inhibitor hypothetically increases penile blood flow. Patient satisfaction ranges from 35%–75% with the main complaints postoperatively being decreased penile length and new onset ED.⁹⁵

The type of graft used often depends on the surgeon’s preference. Saphenous vein, buccal mucosa, acellular porcine dermal matrix, pericardium, and small intestine submucosa are just some of the many available grafts. Buccal mucosa exhibits good elasticity but concerns about oral numbness and mouth tightness demand more long-term follow-up with this approach.^95,112 Small intestine submucosa contains collagen, fibroblast growth factor, and fibronectin, which are vital in the healing process.^113–114 Recurrence (up to 33% within 3 months), hematoma, infection, and penile shortening have brought this graft material into question.¹¹⁵ Preputial dermal flaps were initially promising but high recurrence, presence of inclusion cysts, and poor patient satisfaction have since been reported.¹¹⁶ Pericardial grafts have the benefit of not requiring a harvest site and exhibit substantial tensile strength.¹¹⁷ The pericardium acts as a scaffold that tunica albuginea grows into and with time the graft is enzymatically dissolved.¹¹⁸

Penile prosthesis implantation

Because PD is often associated with ED, preoperative penile vascular studies using color duplex Doppler ultrasound is recommended.^94,110 If a venous leak is identified it is suggested that a PDE5 inhibitor be tried prior to penile prosthesis placement.¹³ In one study, up to 61% of patients with venous leak responded to oral drugs, changing the need for an inflatable penile prosthesis.¹¹⁹ Penile prosthesis has the advantage of both straightening the curvature and providing patients with ED a functional erection. Both malleable and inflatable devices can be used, however higher satisfaction rates are achieved with the inflatable version. The success rate of penile straightening using penile prosthesis for patients with concomitant PD is higher if the curvature is less than 30 degrees. In men with more severe penile curvatures, incision and grafting or plication procedures may be necessary with simultaneous placement of an inflatable penile prosthesis. When comparing inflatable penile prosthesis to incision and grafting, postoperative erectile function domain scores were significantly higher for patients who had undergone inflatable penile prosthesis implantation. While this approach to surgery offers very good outcomes, there are also still risks that need to be fully discussed with the patient. These include infection, device malfunction, repeat operation, and erosion complications.¹²⁰

In patients with minimal curvature (less than 30 degrees), placement of the prosthesis alone results in penile straightening by acting as a tissue expander and softening the plaque over time. Commonly, manual modeling is used in combination with a penile prosthesis to correct mild to moderate curvatures.¹²⁰ Once the prosthesis is inserted, the device is inflated and the surgeon can assess the degree of penile straightening. When the device alone cannot straighten the penis, force is applied to bend the penis in the direction opposite to the curvature.¹¹⁷ This helps to stretch or fracture the plaque and straighten the penis. The success rate with the modeling technique is very high.¹²¹ In patients with bottleneck deformities or with severe curvature (greater than 60 degrees), manual modeling alone is less likely to be effective; in such cases incision in the plaque with or without grafting can be performed as previously described.¹¹⁷

Conclusion

PD is not an uncommon disorder, with recent epidemiologic studies documenting a prevalence of 3–9% of adult men affected. The actual prevalence of PD may be even higher. As the definitive pathophysiology of PD has not been completely elucidated, further basic research is required to make progress in the understanding of this enigmatic condition. Currently, nonsurgical treatments are used for those men who are in the acute stage of PD, whereas surgical options are reserved for men with established PD who cannot successfully penetrate. Future oral treatment options may be directed toward increasing tissue expression of matrix metalloproteinases or inhibition of tissue inhibitors of metalloproteinase activity. This area of research will evolve rapidly as the molecular mechanisms underlying PD are further elucidated. Intralesional treatments are growing in clinical popularity as a minimally invasive approach for the initial treatment of PD. Surgical approaches are considered only when men with PD do not respond to medical or minimally invasive therapies for at least 1 year and when patients cannot have satisfactory sexual intercourse. As scientific breakthroughs in the understanding of the mechanisms of this disease evolve, novel treatments for the many men suffering with PD are anticipated.

Disclosure

The authors report no conflicts of interest in this work.