The Augmenta Implant: A Cadaver Model of a Novel Anatomic Subdermal Implant for Cosmetic Penile Enhancement.

INTRODUCTION: There are limited options for cosmetic penile enhancement and the correction of structural penile deformities. AIM: We present the Augmenta, an innovative, technologically advanced subcutaneous elastomer-silicone cosmetic penile implant (CPI), as evaluated by objective structural changes in a cadaveric model.
METHODS: Five fresh male cadaver pelves were utilized in this preclinical setting. Placement of a subcutaneous elastomer-silicone CPI was performed via a penoscrotal approach. Penile circumference was measured at the base and distal shaft before and after implant placement. Penile length was measured from the pubic bone to the tip of the glans penis before and after implantation of Augmenta. MAIN OUTCOME MEASURE: Objective outcomes included changes in penile circumference and shaft length in both the flaccid and erect state, both before and after CPI placement.
RESULTS: In 5 cadaver models, implantation of the Augmenta CPI increased flaccid penile shaft base circumference from an average of 8.7 cm to 12.0 cm after implantation (39.1% increase, P < .001). Flaccid distal circumference increased from 7.3 cm to 10.3 cm (41.8% increase, P = .020). During the erect state, penile base circumference increased from an average of 12.5 cm to 13.7 cm (6.3% increase, P = .273), while distal erect circumference changed from an average of 11.3 cm to 12.4 cm (9.7% increase, P = .298). Nonstretched flaccid shaft length increased from an average of 12.1 cm to 14 cm (15.2% increase, P = .073). CLINICAL IMPLICATIONS: The Augmenta CPI could serve as alternative option for men seeking cosmetic penile enhancement. STRENGTHS AND LIMITATIONS: Limitations include a small number of cadavers which do not completely reproduce living physiologic function and the use of a single technical approach. However, a consistent and standardized surgical approach reduces operator-dependent outcomes. Another strength is the use of fresh human cadavers that most closely represent live models.
CONCLUSION: In a cadaveric model, the Augmenta CPI demonstrates enhancements in penile girth in both the flaccid and erect state. The unique honeycomb technology, the embedded polyester mesh, and the antimicrobial hydrophilic coating of the Augmenta CPI may provide an advantage to currently available CPIs. Clinical trials will be needed to demonstrate both the safety and feasibility. Clavell-Hernández J, Tatem AJ, Lipshultz LI, et al. The Augmenta Implant: A Cadaver Model of a Novel Anatomic Subdermal Implant for Cosmetic Penile Enhancement. Sex Med 2021;9:100447.

INTRODUCTION

Men have been intrigued by the idea of a larger penis for centuries. Historic evidence indicates that primitive cave dwellers believed the symbolic values of virility, fertility, strength and power were correlated with penile size., This intrigue has been preserved in the modern era with an interest in the augmentation of penile size in both the flaccid and erect state. Moreover, acquired penile deformities, such as Peyronie's disease and buried penis, that give the perception of a shorter penis have been shown to lower the self-esteem and self-confidence of many male patients., This has led to increased demand in the clinical practices of urologists and sexual medicine specialists for cosmetic procedures to potentially enlarge the penis.

Multiple surgical and nonsurgical treatment options exist for penile enlargement. These include silicone or hyaluronic acid injections, dermal matrix grafts, fat transplantation, penile suspensory ligament release, sliding elongation, and subcutaneous silicone penile implants. These procedures have not been widely accepted by the medical community because of potential complications and historically poor cosmetic outcomes. In response to these shortcomings, we have developed a novel subcutaneous hydrophilic-coated cosmetic penile implant (CPI) known as Augmenta. Augmenta was designed to permit safe anatomic expansion that enhances the natural cosmetic penile appearance without encumbering normal penile movement and function. Here we evaluate the anatomic changes produced by implantation of the newly commercially available Augmenta CPI through the use of anatomic cadaveric models.

METHODS

We secured 5 fresh male cadaveric pelvic specimens, ages 30–67 years (lower abdomen to mid-thigh). Cadavers were recently deceased (less than 48 hours) and were without chemical exposure for tissue preservation, thereby approximating living human tissue. Cadavers with a known history of penile surgery other than circumcision were excluded. Clinical and demographic variables including body mass index were not available for review.

Implant Specifications

Here we introduce a novel and technologically advanced subcutaneous elastomer-silicone device that can be surgically implanted for male penile cosmetic enhancement. Augmenta is registered with the U.S. Food and Drug Administration (FDA), has received premarket notification and is awaiting FDA 510k clearance for its use in the cosmetic correction of penile soft tissue deformities. The implant is currently manufactured by Huck Medical Technologies (Jacksonville, TX). The device is available in 24 standard sizes and 175 approved custom variations. Implant models vary in length, inner circumference (core or natural girth), outer circumference (augmented girth), and urethral gap width, with each containing a wall thickness that tapers circumferentially (Table 1; Figure 1). The implant has a “cut-to-fit” design that represents as a solid, nonhoneycomb, silicone at the base, measuring 2.5 or 3.0 cm, depending on the implant length (Figure 1). There are 5 different available cut-to-fit lengths, including 6–8 cm, 8–10.5 cm, 10.5–13 cm, 13–15.5 cm, and 15.5–18 cm. The final chosen implant length can be customized by trimming the un-tapered proximal silicone margin to ensure optimal fit (Figure 1). Implant weights for standard-sized implants range from 16.9 g to 80.7 g.

Table 1

Augmenta CPI size specifications

Specification	Augmenta CPI device
Inner circumference (IC)	55–130 mm
Outer circumference (OC)	85–160 mm
Urethral gap (UG)	15–30 mm
Total length (L)	6.0–18.0 cm

CPI = cosmetic penile implant.

Figure 1

The Augmenta CPI's sizes vary in length, inner circumference, outer circumference, and urethral gap width. The proximal silicone margin can be trimmed and customized to ensure optimal fit.

Augmenta's wall thickness tapers circumferentially from a maximum thickness at the dorsal midline to a minimum thickness at the distal and ventral edges (Figure 2). The implant also features a unique “Honeycomb Technology” characterized by sub-centimeter pockets that comprise the under surface of the device throughout its body, designed to reduce the weight of the implant and optimize device elasticity and compressibility. Additionally, the implant possesses multiple polyester mesh tabs embedded within the ventral-most margins of device. This unique feature permits the use of absorbable sutures to secure the implant, minimizing device migration and rotation until tissue ingrowth into the mesh is complete (Figure 2b,c).

Figure 2

The implant's wall thickness tapers circumferentially. A. Lateral view of the implant. B. Posterior view of the implant showing maximum thickness at the dorsal midline. C. Anterior view of the implant showing minimum thickness at the distal and ventral edges.

Surgical Approach

Five cadavers underwent CPI placement through a penoscrotal approach. All placements were performed by a group of high-volume prosthetic surgeons, with one surgeon standardizing the protocol for each procedure. Even though the procedure can also be performed via an infrapubic approach, the penoscrotal approach was used for implantation in this study and comprised either a longitudinal or diamond-shaped incision made at the penoscrotal junction which excises excess skin produced by scrotal webbing (ventral phalloplasty). Circumcision is not a pre-operative requirement for this operation. Dartos tissue was dissected until the bilateral corpora were identified. Soft tissue dissection and intussusception of the penis was then performed to invert the penile shaft through the penoscrotal incision (Figure 3a). The subcutaneous tissue overlying the penile shaft was then dissected from underlying Buck's fascia. Blunt and sharp dissection was carried out proximally toward the preserved suspensory ligament. Care was taken to avoid disruption of Buck's fascia along the dorsolateral margins of the corpora cavernosa minimizing risk of injury to the underlying penile neurovascular bundle. After the pendulous penile shaft was successfully intussuscepted, the coronal sulcus was carefully defined with sharp dissection, allowing ventro-lateral suturing of the distal margin of the implant to Buck's fascia (Figure 3b).

Figure 3

A. Intussusception of the penis via a penoscrotal incision with proximal dissection toward the suspensory ligament which is preserved. B. The coronal sulcus is defined to allow proper suturing of the implant's distal margin to Buck's fascia on the ventro lateral aspect of the distal penile shaft.

Measurements of the stretched penile length from the pubic bone to the coronal sulcus, and circumference of the penile shaft were obtained. An appropriately sized implant was selected and secured around the intussuscepted penile shaft. The mesh tabs of the distal implant margin were first secured with 3-0 monofilament suture, ventral and lateral to the dorsal neurovascular bundle. Similarly, absorbable sutures were then used to secure the mid- and proximal margins of the implant on the ventral aspect of the corpora approximately 1 cm lateral to the urethra (Figure 4a). Once the implant was secured along its entire ventral length, the penis was then returned to its natural anatomical position and the subcutaneous tissues and skin were closed in layers using absorbable suture (Figure 4b). An artificial erection was induced by injecting normal saline, with an 18-gauge needle placed through the side of the silicone implant, into the corporal body. This was performed at the end of the implantation.

Figure 4

A. Absorbable monofilament sutures are placed approximately 1 cm lateral to the urethra to anchor and secure the implant. B. Once secured, the penis is returned to its natural anatomical position prior to closure.

Measurable outcomes included changes in flaccid penile length, stretched flaccid length, erect length (saline injection-induced artificial erection), penile shaft base circumference, and distal shaft circumference.

RESULTS

A total of 5 Augmenta CPIs were placed via a penoscrotal approach. Penile shaft length in each cadaver will vary by differences in the prepubic soft tissue anatomy. To minimize this variability, a single researcher obtained all measurements for penile length. This measurement was made from the anterior surface of the inferior pubic bone to the distal tip of the glans penis, both with and without stretching the penile shaft. Nonstretched flaccid length increased from an average of 12.1 ± 1.1 cm to 14.0 cm ± 1.7 cm (15.2% increase, P = .073; Figure 5). Stretched flaccid penile shaft length remained unchanged following CPI implantation, with an average of 13.8 ± 1.2 cm and 13.75 ± 0.9 cm pre- and postimplantation, respectively. Unexpectedly, and although not statistically significant, we did note an increase in erect penile length from an average 12.8 ± 1.3 cm to 13.6 ± 1.8 cm (9.7% increase, P = .458).

Figure 5

A. Nonstretched penile length prior to cosmetic implant placement. 5. Nonstretched penile length after cosmetic implant placement.

Girth measurements were obtained by verifying the penile shaft circumference at the base and distal shaft during the flaccid and erect state. Flaccid base circumference increased from an average of 8.7 ± 1.1 cm to 12 ± 1.1 cm after CPI implantation (39.1% increase, P < .001), while flaccid distal penile shaft circumference increased from 7.3 ± 1.3 cm to 10.3 ± 1.7 cm (41.8% increase, P = .020). During the erect state, base circumference increased from an average of 12.5 ± 1.8 cm to 13.7 ± 1.3 cm (6.3% increase, P = .273) while distal shaft circumference increased from an average of 11.3 ± 0.8 cm to 12.4 ± 1.8 cm (9.7% increase, P = .298). These findings are summarized in Table 2.

Table 2

Mean penile measurements (cm) before and after CPI placement (n = 5)

	Preoperatively	Postoperatively	Difference (%)	P Value
Nonstretched FL	12.1	14.0	1.9 (15.2)	.073
Stretched FL	13.8	13.75	-0.05 (1.2)	.942
Erect length	12.8	13.6	0.8 (9.7)	.458
Flaccid BC	8.7	12.0	3.3 (39.1)	<.001
Flaccid DC	7.3	10.3	3.0 (41.8)	.020
Erect BC	12.5	13.7	1.2 (6.3)	.273
Erect DC	11.3	12.4	0.9 (9.7)	.298

BC = base circumference; CPI = cosmetic penile implant; DC = distal circumference; FL = flaccid length.

DISCUSSION

Penile cosmetic enhancement has long been a challenge for urologic surgeons. Injectable materials, including liquid silicone, polyacrylamide, hyaluronic acid, and mineral-oil all carry a risk of foreign body reaction, swelling, penile distortion and granuloma formation., Autologous fat grafting decreases the risk of foreign body reaction and has been shown to provide penile length and girth enhancement. Unfortunately, studies have also shown that the autologous fat graft will lose up to 80% of its volume over time and subsequently require multiple procedures to achieve a desired result., In contrast, as with other commercially available CPIs, the Augmenta implant requires only a single procedure to provide a consistent and natural-appearing result.

Since the 1960s, silicone implants have been successfully used by plastic surgeons for cosmetic soft tissue enhancement. There are, however, no robust data regarding the use of silicone implants for cosmetic penile enhancement. The Penuma silicone sleeve CPI, created in 2004, has recently gained attention in the United States and is available in 3 sizes of 14, 16, and 18 cm in length, weighing 42, 50, and 60 g, respectively. This implant is surgically inserted through an infrapubic incision and is secured with nonabsorbable suture to a separate piece of polypropylene mesh along the dorsum of the distal subcorona. In 2018, Elist et al retrospectively evaluated outcomes of 400 patients who had undergone placement of the silicone sleeve CPI. Their study revealed an increased penile mid-shaft girth from an average of 8.5 ± 1.2 cm to 13.4 ± 1.9 cm (P < .001) and increased flaccid penile shaft length from an average of 9.1 ± 0.7cm to 11.3 ± 0.4 cm 3 months after implantation. Patient satisfaction was reported as high in 81% of respondents. The most commonly reported complications were seroma (4.8%), scar formation (4.5%) and device-related infection (3.3%).

The Augmenta CPI is designed to fit each patient specifically. After measuring multiple patients in the office setting, we obtained averages and standard deviations of adult male penile stretched length and mid-shaft flaccid girth to create standard device sizes. There are 24 standard sizes and 175 approved custom variations that vary in length, inner circumference (core or natural girth), outer circumference (augmented girth), and the width of the urethral gap. (Table 1; Figure 1). There are 5 different available "cut-to-fit" lengths, including 6–8 cm, 8–10.5 cm, 10.5–13 cm, 13–15.5 cm, and 15.5–18 cm. The "cut-to-fit" proximal portion of the implant allows the surgeon to trim the implant to the specific stretched length of each patient to avoid malposition and optimize cosmetic outcomes.

We maintain that a successful CPI should conform to the existing penile anatomy and provide, with limited risk of complication, a natural-appearing penile enhancement without compromising normal anatomical and physiological movement. Augmenta's “Honeycomb Technology” is comprised of internal pockets comprising the inner surface of the implant body. This feature provides a structural rigidity gradient within the implant that permits modification of device elasticity throughout its length. With this development, the Augmenta CPI can uniquely vary not only its weight and firmness, but the location along each implant where such weight and rigidity will be distributed, simply by changing the depth and septations of the honeycomb pockets that comprise its structure. Thus, the implant can be made both lighter and softer by increasing the depth and volume of these pockets and by reducing the thickness of the honeycomb septae. This creates a gradient effect along the implant which allows the penis to compress and bend with the natural movement of the flaccid penis while allowing the penis to expand in both length and girth during a natural erection.

Our results revealed a 39.1% average increase in penile base circumference during the flaccid state after implantation and a 6.3% average increased circumference during the erect state. There was a 15.2% average increase in penile length during the flaccid state. Unexpectedly and although not statistically significant, we did note a slight gain in average erect penile length, from 12.8 ± 1.3 cm before implantation to 13.6 ± 1.8 cm after implant placement, representing a 9.7% average postimplantation erection augmentation (P = .458). We understand that measurements during an artificial erection may sometimes be difficult to standardize given that these are obtained with the presence of a tourniquet that may alter dimensions and that the volume of saline injected to produce a given erection can differ. These findings require further verification through future clinical trials.

Augmenta CPI contains multiple soft polyester mesh tabs that are embedded within the underside of the implant at its most ventral margins. This unique feature allows the surgeon to use absorbable sutures to secure the implant in the desired location, well away from the dorsal neurovascular bundle and lateral to the urethra. Subsequent tissue ingrowth into the mesh is expected to reduce the risk of implant migration, malposition, and skin erosion. Ventral fixation also minimizes the risk of injury to the dorsal neurovascular bundle should the implant ever require later removal. Moreover, the penoscrotal surgical approach facilitates ventral placement of the implant lateral to the urethra, by permitting direct inspection that minimizes the risk of injury or obstruction of the urethra during implantation. Should a patient later desire an inflatable penile prosthesis to correct future erectile dysfunction, this can also be safely implanted utilizing a standard penoscrotal approach.

Responsible development of any prosthetic device involves meticulous design that considers not only anatomic and physiologic conditions but also anticipates the potential need for device removal. The embedded polyester mesh tabs in the Augmenta CPI are expected to permit tissue ingrowth within several weeks following placement. This process is anticipated to occur only at the most ventral margin of the pendulous penile shaft at the level of Buck's fascia where the interrupted embedded mesh is secured. These are secured with absorbable sutures common to all penile prosthetic procedures. Implant removal can therefore be facilitated through a penos-scrotal incision ventrally, avoiding dissection of tissue planes associated with the dorsal neurovascular bundle. Moreover, the strategic placement of the anchoring mesh tabs of the Augmenta CPI similarly avoids dissection involving the urethra more medially or the deeper corporal bodies. The hydrophilic coating covering the entire surface of the implant should also minimize scar tissue formation or adhesions to the overlying skin hence, facilitating device removal and mitigating cosmetic complications associated to device explanation.

Prosthetic infection remains the most devastating complication of any penile implant surgery. Prior to antibiotic coated implants, the incidence of infection in first-time inflatable penile prosthesis cases ranged from 3% to 5% in patients without risk factors and up to 8% in diabetics.12, 13, 14 This increased risk of infections led penile prosthesis manufacturers to create infection-resistant coated penile implants which have since decreased the infection risk to less than 3%, even among high risk patients.14, 15, 16, 17 Polyvinylpyrrolidone is a lubricious hydrophilic substance that, when coating a prosthetic device, decreases bacterial adhesion to the implant and permits absorption of aqueous antibiotic solution immediately prior to surgical implantation. A meta-analysis comparing the effectiveness of infection-resistant coated inflatable penile prostheses showed a significant advantage in preventing postoperative infection when compared to noncoated implants. To date, the Augmenta is the only CPI with a hydrophilic coating that can be dipped in antibiotic solution.

Men with structural penile abnormalities, such as those with buried penis or hourglass deformity from Peyronie's disease, are expected to also benefit from the Augmenta CPI. Successful treatment of patients with Peyronie's disease depends not only on objective physical modifications, but also on the patient's personal satisfaction and perceived enhancement from the surgical result. Reed-Maldonado et al presented the extra-tunical grafting procedure for patients with penile indent and hourglass. In their procedure, a cadaveric fascia graft was wrapped around the shaft over the indentation of the tunica albuginea to create a smooth and uniform "surface." Similar to the extra-tunical grafting technique, the Augmenta CPI can be used to cover hourglass and indent deformities of the penis. The Augmenta CPI is also expected to keep the penis on its maximal stretched flaccid length and could theoretically help resurface the penis in some men with a buried penis. This could be further investigated in future clinical trials in these patient populations.

The current study has several notable limitations. This report utilized a small number of cadavers. Moreover, a cadaveric model does not completely reproduce living anatomic or physiologic function. Despite our attempt to mimic living tissues by utilizing fresh cadavers, it is unclear if our findings will translate to both immediate and durable outcomes in living human subjects. Future clinical trials and additional clinical experience with postoperative monitoring will clarify this understanding. Additionally, we performed assessment of only a single technical approach. Alternative techniques may be associated with different outcomes. Despite these limitations, we feel that our study has several strengths. We used a consistent surgical approach, standardized by a single surgeon, which limited operator-dependent outcomes variability. Our use of fresh human cadaveric tissues most closely approximated the live model and provided the anatomic representation of the expected cosmetic outcome.

CONCLUSION

There is an increased demand for procedures that enhance penile cosmesis. The Augmenta subcutaneous elastomer-silicone CPI's uniquely features a structural elasticity/rigidity gradient-producing Honeycomb Technology and embedded soft polyester mesh which may provide multiple clinical advantages to currently available injectable materials and alternative CPIs. Augmenta's bacterial-resistant hydrophilic coating has the potential to reduce implant infection risk, approximating the modern inflatable penile implants that treat erectile dysfunction. Future clinical trials will better characterize the overall safety and efficacy of the Augmenta CPI in producing penile cosmetic enhancement and as a solution for the correction of penile deformities.

STATEMENT OF AUTHORSHIP

Jonathan Clavell-Hernández: Methodology, Investigation, Formal Analysis and Data Curation, Writing – Original Draft, Writing – Review and Editing; Alexander J Tatem: Methodology, Investigation, Writing – Review and Editing; Larry I Lipshultz: Investigation, Writing- Review and Editing, Supervision; Run Wang: Investigation, Writing- Review and Editing, Supervision; Robert J Cornell: Conceptualization, Methodology, Investigation; Writing – Original Draft, Writing- Review and Editing, Resources, Supervision, Project Administration.