Erectile function is an important goal for many transmasculine patients who undergo neophallus reconstruction.^1,2 Penile prosthesis placement post phalloplasty provides neophallus rigidity for penetrative intercourse but is a complex procedure with high risk of complications. Since currently available prostheses are designed for cisgender penises, transgender male anatomy—with lack of tunica albuginea, less reliable blood supply and diminished sensation—increases the challenges associated with placement.³ Penile prosthetic surgery is performed at least 9–12 months following phalloplasty, allowing for neurotization and increased vascularization of the flap to decrease the risk of complications.^1,2,4–6

Patient preference, surgeon experience and preoperative assessment of neophallus length and girth determine which implant should be placed. The semirigid implants, such as the Coloplast Genesis^® and Boston Scientific Spectra™, are easier to insert but are less preferred due to persistent rigidity and concerns for pressure necrosis and anchor site detachment.^2,4 The Ambicor™ is a 2-piece inflatable penile prosthesis that can be advantageous in patients with prior abdominal or groin surgery, but it lacks a proximal solid silicone component for pubic bone anchoring.⁷ Three-piece inflatable penile prostheses, including the Coloplast Titan^® and AMS 700™, require a pouch-like neoscrotum to house the pump component. Overall, the Titan is favored because of improved rigidity, a smoother profile pump, and a solid proximal aspect of the cylinder that facilitates anchoring.⁴ Inflatable penile prostheses are more often desired as the ability to deflate the device improves comfort and aesthetics.^3,6,7

Several approaches for placement exist, including infrapubic, penoscrotal, parascrotal, and dorsal penile.^1,2 Our preferred approach is outlined in Figure 1. Prior phalloplasty anatomy influences the approach as avoidance of the neourethra and neurovascular supply is of upmost importance.⁶ For example, if the neophallus vascular supply is inferolateral as in a pedicled anterolateral thigh flap or any free flap phalloplasty connected to the superficial femoral artery system, then an infrapubic approach is safe. Parascrotal incisions are more often used when neophalluses are vascularized via the deep inferior epigastric vascular system. Preoperative CT angiograms and/or intraoperative Doppler evaluation can help localize the vascular supply to determine the safest approach.

Figure 1. Infrapubic approach to penile prosthesis placement.

Hegar or Brooks dilators are used to create space for the implant. Single cylinder placement is more common.⁶ If a single cylinder is planned, then dilation proceeds in the dorsal midline to avoid urethral injury (Fig. 2). If 2 cylinders are required, 2 separate dilations dorsolateral to the urethra are necessary. Maintaining a 1 cm distance between the distal edge of the cylinder and the glans tip can decrease the risk of erosion.^2,4 Distal cushioning with the addition of a graft cap on the cylinder may also help, but adding graft material may increase the risk of infection.^1,4

Figure 2. Midline dilation performed with metal dilator in the neophallus.

Figure 3. Postoperative image of 3-piece inflatable prosthesis placed via an infrapubic approach.

Figure 4. Sub-optimal penile prosthesis placement leading to poor aesthetics and function.

Proximal fixation is required to provide stability with erections and penetration.^2,4,5 Strategies for fixation include bone drilling and suturing, with or without neotunical graft sheaths or rear tip extenders. Neotunical sheaths or rear tips can be attached to the pubic symphysis, pubic ramus, or ischial tuberosities.^1,4 The proximal cylinder is then inserted into the sheath or the rear tip extender, although the erection may be less stable with rear tip extenders.⁴ For implants with solid proximal cylinders, the sheath can be sewn directly onto the cylinder and then secured to the bone anchor site.

For inflatable prostheses, the pump is placed in the neoscrotum. The reservoir can be placed in the Space of Retzius, the iliac fossa, or a submuscular pocket. Patients with perineal scrotums or hostile abdomens would not be good candidates for inflatable implants. Postoperatively, the device is left partially inflated to prevent pseudocapsule contraction. Activation may occur as early as 2 weeks, but the use of the device for penetration should not occur before 6 weeks.⁴ Figure 3 shows a postoperative image of a 3-piece inflatable prosthesis placed via an infrapubic approach.

Overall revision rates range considerably from 20%–80%, with fewer complications over time as surgeon experience increases (Fig. 4).^1–3,6,7 Neurovascular supply injury is fortunately a rare, but serious, event that has not been well documented in the literature.¹ Up to 20% of patients have been reported to develop infections likely secondary to factors that decrease barriers and impair wound healing.^1,3,4,6,7 Rates of erosion are as high as 33%.¹ Migration can occur due to lack of a sheath around the prosthesis or insufficient anchoring, with rates between 3%–30%.^1,4,6 Earlier device failure has been noted in this population as well, with 5-year survival rates of 78% compared to 87%–93% in cisgender men.^1,8

Although patient reported outcomes are limited and a validated measurement tool is lacking, overall satisfaction rates are reported between 88%–92% with 51%–85% of patients engaging in penetrative intercourse.^2,5,6,8 Preoperative counseling is crucial to manage expectations and minimize postoperative dissatisfaction.

Design updates that may improve outcomes include a wide rear tip for proximal fixation, a glans like distal tip for better aesthetics, and a single larger cylinder for improved rigidity.^9,10 The ZSI 100 FtM malleable and ZSI 475 FtM inflatable implants were designed with these specifications in mind.¹⁰ The ZSI 475 FtM implant appears to have fewer complications and be better tolerated than the ZSI 100 FtM implant.¹⁰ In a small cohort of transgender men who received ZSI 475 FtM implants, 92.8% reported satisfaction with the device and 85.7% reported ability to engage in penetrative intercourse.¹⁰

While these devices are commercially available, neither is currently approved by the U.S. Food and Drug Administration and some of the design optimizations, although designed to optimize the FtM implant, can create additional surgical complications. The wider distal portion of the cylinder and shaft requires more aggressive dissection of the neophallus channel with resultant increased probability of neurovascular injury. The larger flat base for anchoring requires wider dissection under the pubic symphysis, which could lead to adductor or gracilis muscle and tendon injury.

Optimization of devices and techniques in masculinizing genital gender affirmation surgery is essential for continued improvements in transgender care as more patients pursue penile prosthesis placement after phalloplasty.