Gender dysphoria refers to an inner mental unrest resulting from an incongruity between the assigned biological sex and the mentally experienced sex. The generally accepted treatment for gender dysphoria aims to bring a person's physical characteristics in line with his or her perceived gender identity. This gender-affirming treatment consists of a combination of psychological counselling, hormonal therapy and, if desired, genital gender-affirming surgery (GGAS), which involves the removal of the biological reproductive organs and in some cases (part of) the biological sex organs. These can be replaced by surrogate sex organs of the desired sex while maintaining urological and sexual function. In transgender men, metoidioplasty or phalloplasty are performed. A national survey of transgender adults in the United States has shown that 22% of transgender men have had or clearly state they want gender affirming surgery in the form of phalloplasty, while 27% state this for metoidioplasty. In phalloplasty, anatomically sized external genitalia (penis with or without urethra, scrotum, and perineum) are created using on the one hand a donor skin flap (usually from the forearm, upper leg or inguinal region), and on the other hand tissues from the original genitals. In metoidioplasty, the goal is to create anatomically looking but undersized external genitalia in which the clitoris forms the base of a micro-penis. The neophallus created in the case of phalloplasty is by itself usually insufficient for penetrative sexual intercourse, due to the lack of erectile structures. However, previous research suggests that one of the main reasons transgender male individuals choose for phalloplasty over metoidioplasty is the ability to penetrate a sexual partner. This was also one of the original goals of phalloplasty.

In order to be able to proceed to penetrative sexual intercourse, one option can be the implantation an internal erectile prosthesis or the use of an external device or epithesis. Internal protheses form at this point the main method of attaining penile rigidity after phalloplasty. Both malleable and inflatable options are available today. However, these devices, just as the primary GGAS procedures, carry a high risk of complications. Previous research with prostheses originally designed for cisgender men has shown that up to 22% of prostheses was explanted for various reasons including infection, erosion and malfunction within 20 months. Another study showed that only 62% of patients still had their prosthesis in place after 4 years. More recent publications with a prosthesis specifically designed for phalloplasty patients (ZSITM 475 FtM, Zephyr Surgical Implants, Switzerland, Europe) have shown explantation rates of 19% and 23% at 9 and 18 months respectively. The lack of reliable, and durable erectile devices leads to the fact that a large proportion of patients either chooses for phalloplasty but never goes on the placement of an erectile prothesis or completely abandons the idea of GGAS under the form of phalloplasty at this point in time. As underlined in a recent qualitative study, transgender men may very well be concerned about the complication rates and likely need for additional surgeries associated with the surgical treatments they seek to diminish their gender dysphoria, specifically in penile implant surgery. This is further aggravated by the fact that penile implant surgery is associated with higher complication in a transgender population than in a cisgender population. Penile prostheses were originally designed for an older cisgender male population with treatment resistant erectile disfunction wishing to regain the capacity of penetrative sexual intercourse. No data exists on what the durability of penile implants are in a younger and more sexually active population. Furthermore, the placement of a prosthesis is particularly more difficult after phalloplasty as there are no cavernosal bodies with surrounding tunica albuginea that can be used as scaffold for anchoring of the prosthesis to the pubic bone and preventing it from erosion through the skin. Therefore, alternative options for transgender and gender non-conforming patients after phalloplasty are needed. Although some may be surgical, it may be interesting for some individuals to have non-surgical options as well.

When considering penile epitheses, multiple types are commercially available. One of such devices is a penile lifter or splint and is marketed as the ElatorTM or the ErektorTM for cisgender patients with erectile dysfunction after prostate cancer. These devices consist of two rigid rings connected by rigid metal rods. The biggest of two rings is placed around the base of the phallus. The second ring is connected to the metal rods and is placed behind the coronal ridge. By connecting the rods to the ring at the base of the penis, tension and therefore rigidity between the two rings is created. With the device in place, men can then penetrate their partner and remove it again after intercourse.

Penile splints were originally designed in the beginning of the 20th century for various reasons of erectile disfunction. Loewenstein was the first to produce a study on his personal re-interpretation of this device in 1941. Originally, these devices have been designed for cisgender men with erectile dysfunction, but social media and patient conversations suggest that post-phalloplasty patients have been experimenting with them. Feedback from transgender patients using this device can be found on the website of the product manufacturers, but also on social media sites such as Tumblr, Youtube, and private Facebook channels. They may form a potential alternative to internal prostheses in transgender patients not wishing to undergo further surgery after phalloplasty or in patients that have experienced problems after implantation. A recent study piloting the use of the ElatorTM in 10 post-phalloplasty transgender participants and their partners has suggested that the feasibility of continued use of the epithesis lies around 30%. However, the low patient inclusion rate and substantial loss of follow-up during this preliminary study may very well have biased final results. Nevertheless, important lessons on patients' concerns and expectations as well as anatomical reflections are to be learned from this study. Therefore, our center has been keeping close contact with the team of Dr. Boskey in designing this study protocol.

The current study aims to extend the knowledge on these external devices by comparing them to the implantation of an internal penile prosthesis in post-phalloplasty transgender patients.