Krasnoff Chloe, Ferrin Peter, Peters Blair R
From the Division of Plastic Surgery, Oregon Health and Science University, Portland, Oreg.
Transgender Health Program, Oregon Health and Science University, Portland, Oreg.
Plast Reconstr Surg Glob Open. 2023 May 10;11(5):e4971. doi: 10.1097/GOX.0000000000004971. eCollection 2023 May.
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.
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.
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).
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.
神经移植成功的一个关键因素是神经支配密度，它直接受供体神经轴突密度和供体与受体（D:R）轴突比例的影响。神经移植的最佳D:R轴突比例为0.7:1或更高。在阴茎成形手术中，目前几乎没有可用数据来指导供体和受体神经的选择，包括轴突计数数据的缺失。
对5名接受性别确认性前臂桡侧阴茎成形术的跨性别男性的神经标本进行组织形态计量学评估，以确定轴突计数和大致的供体与受体轴突比例。
受体神经的平均轴突计数分别为6957±1098（前臂外侧皮神经[LABC]）、1866±590（前臂内侧皮神经[MABC]）和1712±121（前臂后侧皮神经[PABC]）。供体神经的平均轴突计数分别为2301±551（髂腹股沟神经[IL]）和5140±218（阴蒂背神经[DNC]）。使用平均轴突计数计算的D:R轴突比例为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）和IL:PABC 1.344（0.85 - 1.82）。
DNC是更有效的供体神经，其轴突计数是IL的两倍多。基于始终小于0.7:1的轴突比例，IL神经可能不足以重新支配LABC。所有其他平均D:R均大于0.7:1。对于单独重新支配MABC或PABC而言，DNC的轴突计数可能过多，D:R超过2.5:1，这可能增加吻合部位形成神经瘤的风险。
