Penile Allotransplantation: Pushing the Limits

Donor and Recipient Nerve Axon Counts in Gender-affirming Radial Forearm Phalloplasty: Informing Choice of Nerve Coaptations

A key component of success of a nerve transfer is the innervation density, which is directly affected by the donor nerve axonal density and donor-to-recipient (D:R) axon ratio. Optimal D:R axon ratio for a nerve transfer is quoted at 0.7:1 or greater. In phalloplasty surgery, there are currently minimal data available to help inform selection of donor and recipient nerves, including unavailability of axon counts.

Methods

Five transmasculine people who underwent gender-affirming radial forearm phalloplasty had nerve specimens processed with histomorphometric evaluation to determine axon counts and approximate donor-to-recipient axon ratios.

Results

Mean axon counts for recipient nerves were 6957 ± 1098 [the lateral antebrachial (LABC)], 1866 ± 590 [medial antebrachial (MABC)], and 1712 ± 121 [posterior antebrachial cutaneous (PABC)]. Mean axon counts for donor nerves were 2301 ± 551 [ilioinguinal (IL)] and 5140 ± 218 [dorsal nerve of the clitoris (DNC)]. D:R axon ratios using mean axon counts were DNC:LABC 0.739 (0.61-1.03), DNC:MABC 2.754 (1.83-5.91), DNC:PABC 3.002 (2.71-3.53), IL:LABC 0.331 (0.24-0.46), IL:MABC 1.233 (0.86-1.17), and IL:PABC 1.344 (0.85-1.82).

Conclusions

The DNC is the more powerful donor nerve with greater than two times the axon count of the IL. The IL nerve may be under-powered to re-innervate the LABC based on an axon ratio consistently less than 0.7:1. All other mean D:R are more than 0.7:1. DNC axon counts may be excessive for re-innervation of the MABC or PABC alone with D:R of more than 2.5:1, potentially increasing risk of neuroma formation at the coaptation site.

Functional and surgical outcomes after phalloplasty in cis men

PURPOSE

Evaluate the surgical outcomes along with a comprehensive assessment of functional outcomes in cis men (non-trans) who underwent phalloplasty.

METHODS

All consecutive cis men who underwent phalloplasty from 2008 to 2018 for penile insufficiency due to various causes were included. These underwent phalloplasty by either a radial forearm free flap (RFFF) or suprapubic phalloplasty (SPP). Data were collected from medical files. A questionnaire was sent a minimum of 1 year after surgery to each patient to evaluate sexual function and self-esteem, satisfaction with genitals, and urinary function.

RESULTS

Among the 19 patients included, 12 underwent RFFF and 7 SPP; 25% of those who had RFF and 14.3% of those with SPP had a Clavien-Dindo ≥ 2 complication. A total of 16 patients had a urethroplasty procedure, 50.0% of whom had a Clavien-Dindo ≥ 2 complication. Penile prostheses were implanted in 14 patients; 64.3% of whom had a complication. Seven patients answered the questionnaire (36.8%); the relationship satisfaction score was 89.5/100 and the confidence score was 100/100. Among the 5 patients who had a sexual relationship, all reported having a lot of pleasure during sexual intercourse and reached orgasm at least "regularly". At least 66.7% of the patients were "satisfied" or "very satisfied" about the size and the appearance of genitals. Among the 5 patients who answered questions regarding urinary function, 60.0% had standing micturition, and 80.0% reported being comfortable in public toilets.

CONCLUSION

Despite the high frequency of complications and the need for revision surgery, phalloplasty seems to allow a satisfying psychosexual and urinary functions for cis men suffering from penile insufficiency.

Ethical stakes of penile transplantation: A literature review

BACKGROUND

Vascularized composite allotransplantation has become an alternative reconstruction technique for patients with a severe loss of substance. Today, five human penile transplantations have been reported. The objective of this literature review is to offer an updated overview of the technical and ethical questions surrounding penile transplantation compared with conventional phalloplasty.

MATERIAL AND METHODS

A systematic review was conducted of the literature from 2000 to 2020. A search of PubMed was performed using the keywords: "penile transplantation," "penis transplantation," and "penile vascularized composite allotransplantation." The criteria for the analysis were the type of study, surgical techniques, and ethical concerns.

RESULTS

Thirty-six articles were selected. These articles include reviews, case report, editorials, and preclinical studies. The first article was published in 2003, but the number of articles has increased after the second human transplantation in South Africa in 2014. Surgical techniques and the medication management specific to each team were successful in the 5 transplant cases, but several complications were noted.

CONCLUSION

Two decades of successful penile transplantations have proven the technique to be a viable solution to treat a penile amputation, allowing for a better esthetic and sensitive outcome paired with the possibility of natural urinary and erectile functions. Psychological impact of penile transplantation, selection of patients, complications of immunosuppressive therapies, and surgical technicity are the biggest penile transplantation challenges. Further experimental studies are necessary to produce standardized protocols to safely include penile transplantation in the conventional treatment of a penile amputation.

Vascularized composite allotransplantation of the penis: current status and future perspectives

Given the multifunctional role of the penis in daily life, penile loss can be a physically and emotionally devastating injury. Options to restore penile loss have traditionally relied on autogenous free flap, local flaps, and skin grafts. These techniques provide satisfactory outcomes but carry high rates of urologic and prosthesis-related complications. Vascularized composite allotransplantation may offer a novel solution for these patients through reconstruction with true penile tissue. Still, penile transplants pose ethical, logistical, and psychosocial challenges. These obstacles are made more complex by the limited cases detailed in published literature. A review of the literature was conducted to assay current practices for penile reconstruction. Most modern complex penile reconstructions utilize autogenous pedicled or free tissue flaps, which may be harvested from a variety of donor sites. A total of five penile transplants have been described in the literature. Of these, four report satisfactory outcomes. The advent of genital allotransplantation has recently broadened the landscape of treatment for penile loss. Reconstruction using true penile tissue through vascularized penile allotransplantation has the possibility to engender increased penile function, sensation, and overall quality of life.

A pilot retrospective CT angio study of the internal pudendal arteries in male bodies, for the purpose of penis transplantation to trans men

Literature reports four successful cases where penile transplantation has been performed for cis men. To date, no penis transplantation has ever been attempted for trans men. Modern surgical techniques for penis reconstruction for (trans) men with gender incongruence present multiple drawbacks, and sometimes fail to meet patients' expectations. Penis transplantation could represent an alternative solution. With the aim of planning penis transplantation to trans men, a previous study from our same group suggested a surgical technique for explantation of penis and associated vessels, nerves and urethra en-bloc from a cadaver: further radiographic imaging of vascular anatomy was recommended. To measure length and diameter of the internal pudendal arteries at three set points in biological males, in order to confirm its viability for transplantation. A retrospective examination of existing CT images visualizing the internal pudendal arteries in 12 bodies, assigned male at birth, was performed. Diameters were measured in three points: 1. the take off of the artery; 2. distal to its rectal branch; and, 3. at the bifurcation of the two terminal branches of the artery, i.e. the bulbourethral artery and the dorsal artery of the penis. Mean diameters of the selected points were 2.4 mm, 1.9 mm, and 1.5 mm on both sides. Mean lengths of internal pudendal arteries were 111.2 mm on the left, and 120.1 mm on the right side. Diameters of the internal pudendal artery is sufficient for arterial anastomosis at all measured points. Lengths are sufficient to reach recipient vessels.