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Sensate External Pudendal Artery Perforator (EPAP) Hemi-Scrotal Flap

The sensate EPAP hemi-scrotal flap is a single-stage, islanded perforator flap that uses one hemiscrotum — pedicled on an isolated external pudendal artery (EPA) perforator with deliberate inclusion of the anterior scrotal nerve — to provide circumferential coverage of the denuded penile shaft with innate sensory preservation. Described by Tsukuura, Engmann, Miyazaki, and Yamamoto (Microsurgery 2025), it is the first application of true perforator-flap principles to scrotal penile reconstruction. The index case achieved complete flap survival at 7 months, good sensation, and no dyspareunia or stretching sensation — from a single hemiscrotum.[1]

For other scrotal flaps, see Fakin bipedicled, Murányi tunnel, Yao butterfly, Total Anterior (Zhao), Reverse (Gao), Pribaz/McLaughlin staged, and VSSF. Full framework: Penile Reconstruction.

Rationale​

Traditional scrotal flaps (Fakin, Yao, Murányi, Pribaz, Zhao) are fasciocutaneous pedicle flaps that incorporate the anterior scrotal arteries within a broad skin-dartos pedicle at the scrotal root. Inherent limitations:[1]

  1. Bilateral EPA sacrifice in most bilateral designs
  2. Dyspareunia and stretching during intercourse from pedicle tethering
  3. Visible bilateral donor scars + scrotal-raphe scar
  4. Limited rotation arc of fasciocutaneous pedicles vs islanded perforators
  5. Two-stage for some designs (Pribaz)

EPAP applies the perforator-flap concept — isolating the source-artery perforator from surrounding fascia / muscle — to the scrotum. The result is an islanded flap with maximal mobility, wider rotation arc, tension-free inset, and elimination of pedicle tethering. Conceptually analogous to the DIEP-vs-TRAM and ALT-perforator-vs-tensor-fasciae-latae transitions.[5]

Vascular Anatomy​

External pudendal artery system[6][7][8][9]​

  • EPA arises from the femoral artery (occasionally common femoral / profunda)
  • Superficial EPA (SEPA) courses superficially over the femoral vein and spermatic cord toward the pubis
  • Inferior (deep) EPA (IEPA) courses behind the great saphenous vein; gives rise to the anterior scrotal arteries supplying the lateral scrotal territories
  • Cadaveric dimensions (Phoon/STEPA, 6 cadavers):
    • EPA artery external diameter at femoral origin 2.81 mm
    • EPA vein external diameter 4.44 mm
    • Mean pedicle length 11 cm (10–12 cm)
  • IEPA at penile base 0.94 mm (Lohasammakul)[8]
  • Jin microdissection (11 cadavers, 22 sides): 4 relatively constant perineal perforating branches including inguinal and perineal SEPA branches — direct perforators, not musculocutaneous; form upper / middle / lower deep-fascia anastomoses[9]

Carrera three-territory model​

  • Each hemiscrotum has its lateral cutaneous territory supplied by an IEPA entering at the scrotal-root midpoint
  • Central territory supplied by posterior scrotal arteries (perineal / internal pudendal)
  • Territories are "widely inter-anastomosed"[6]

The perforator-isolation innovation​

The key technical advance is skeletonizing the EPA perforator from surrounding fascia — converting a fasciocutaneous pedicle flap into a true islanded perforator flap. This yields the wider rotation arc and tension-free inset that distinguish EPAP from all other scrotal-flap designs.[1]

Neural Anatomy and Sensate Design​

Scrotal innervation[10][11]​

NerveOriginTerritory
Anterior scrotal nervesIlioinguinal nerve (L1)Anterior and lateral scrotal skin
Genital branch of genitofemoralL1–L2Cremasteric muscle + scrotal skin
Posterior scrotal nervesPerineal branch of pudendal (S2–S4)Posterior and inferior scrotal skin

The anterior scrotal nerve travels in close proximity to the EPA from the inguinal region toward the scrotal root.

Sensate-by-design preservation​

The anterior scrotal nerve is deliberately identified and preserved within the EPAP pedicle — providing innate immediate sensation rather than depending on random reinnervation from the wound bed. This is the first scrotal flap for penile reconstruction to specifically preserve a named sensory nerve.[1]

Septal preservation​

Yucel & Baskin: the interscrotal septum has dense innervation, with each hemiscrotum innervated primarily separately. Any procedure violating the penoscrotal / interscrotal septal area jeopardizes scrotal innervation. EPAP's unilateral, septum-preserving design protects the contralateral hemiscrotum's nerve supply.[10]

Indications​

  • Circumferential penile shaft skin defects with viable deep structures
  • Post-replantation skin necrosis — the index indication
  • Post-circumcision skin loss
  • Post-trauma / post-tumor excision shaft skin defects
  • Sensory preservation a patient priority
  • Single-stage with minimal donor-site morbidity preferred
  • Single hemiscrotum coverage is sufficient (≥ 9 × 14 cm flap shown adequate)

Prerequisites​

  • Intact EPA on donor side (preoperative handheld Doppler)
  • Uninvolved adequate scrotal skin on the donor hemiscrotum
  • Viable corpora cavernosa, corpus spongiosum, urethra
  • Microsurgical expertise for perforator isolation

Operative Technique​

1. Preoperative Doppler mapping​

  • Handheld Doppler to identify and mark the EPA perforator at the scrotal root / inguinal crease
  • Select the side with the most robust signal (right hemiscrotum in the index case)

2. Flap design​

  • Hemi-scrotal island flap on the chosen side (no skin bridge)
  • Index case dimensions 9 × 14 cm — sufficient for circumferential shaft coverage
  • Boundaries:
    • Medial: scrotal raphe
    • Lateral: lateral scrotal crease
    • Superior: scrotal root / penoscrotal junction
    • Inferior: inferior hemiscrotum
  • Pedicle point marked at the Doppler-localized EPA perforator

3. Debridement of the penile defect​

  • Excise necrotic skin to Buck's fascia
  • Index case: 12 d after the initial penile replantation
  • Hemostasis; irrigation

4. Suprafascial flap elevation​

  • Elevate above the deep fascia, periphery → pedicle
  • Preserve dartos with the flap (subdermal plexus)
  • Donor-side testis transiently exposed but covered by tunica vaginalis

5. Perforator isolation — the defining step​

  • Identify the EPA perforator as dissection approaches the scrotal root
  • Isolate the perforator from surrounding fascia and soft tissue → skeletonized vascular pedicle
  • Dissect proximally toward the EPA trunk for additional pedicle length
  • Converts the flap from fasciocutaneous-pedicle to true islanded-perforator design

6. Anterior scrotal nerve preservation​

  • Identify the anterior scrotal nerve (ilioinguinal branch) accompanying the EPA perforator
  • Preserve within the pedicle with continuity to the flap skin → sensate flap

7. Rotation and wrapping​

  • Rotate the island flap on its skeletonized pedicle onto the denuded shaft (arc up to 180°+)
  • Wrap circumferentially

8. Inset​

  • Distal edge to subcoronal margin / glans; proximal edge to penile base / pubic skin
  • Free edges sutured together as a single longitudinal seam (dorsal or ventral)
  • Interrupted absorbable suture

9. Donor closure​

  • Hemi-scrotal donor site closed primarily — the contralateral hemiscrotum provides adequate coverage of the ipsilateral testis
  • Scar positioned on the lateral aspect of the scrotum — inconspicuous

Outcomes — Tsukuura Index Case (n = 1)[1]​

ParameterResult
Patient40-year-old male, schizophrenia
EtiologyCircumferential penile skin necrosis after replantation for self-inflicted amputation
Time from replantation12 days
Flap dimensions9 × 14 cm
DonorRight hemiscrotum
PlaneSuprafascial
PerforatorEPA perforator (isolated)
Nerve preservedAnterior scrotal nerve (ilioinguinal)
StagingSingle-stage
Flap survivalComplete (100%)
Short-term complicationsNone
Follow-up7 months
Color matchExcellent
SensationGood (via anterior scrotal nerve)
Pain / dyspareunia / stretchingNone
Erectile functionRecovered
Donor scarInconspicuous (lateral scrotum)

Key Innovations vs Traditional Scrotal Flaps​

  1. Perforator isolation (islanded design) — fasciocutaneous pedicles of Fakin / Yao / Murányi / Pribaz / Zhao limit rotation, create inset tension, and cause stretching during erection. EPAP's skeletonized pedicle eliminates these.
  2. Unilateral harvest — most circumferential techniques use bilateral scrotal flaps that sacrifice both EPAs, leave bilateral donor scars, risk bilateral testicular ascension (Mendel ~ 22.7%), and reduce scrotal volume significantly. EPAP uses only one hemiscrotum.[12]
  3. Deliberate named-nerve preservation — Zhao's 100% sensation recovery likely reflected random reinnervation; EPAP is the first to specifically preserve a named sensory nerve in the pedicle.[13]
  4. Elimination of dyspareunia / stretching — attributed by the authors to perforator isolation removing pedicle tethering.

Comparison Across All Major Scrotal-Flap Techniques​

FeatureEPAP (Tsukuura)FakinMurányiYaoZhao totalPribaz stagedGao reverseVSSF
Flap typeIslanded perforatorFasciocutaneous pedicleFasciocutaneous pedicleFasciocutaneous pedicleFasciocutaneous pedicleFasciocutaneous pedicle (staged)Reverse-flow fasciocutaneousLocal rotation
Hemiscrotums used1 (unilateral)2 (bilateral)1 midline2 (bilateral)Entire anterior2 (bilateral)2 (bilateral)Bilateral partial
Perforator isolatedYesNoNoNoNoNoNoNo
Named nerve preservedYes (anterior scrotal)NoNoNoNoNoNoNo
Rotation arcWidest (islanded)LimitedLimitedLimitedLimitedn/a (staged)LimitedLimited
StagingSingleSingleSingleSingleSingleTwoSingleSingle
Dyspareunia / stretchingNone reportedn/rn/rn/rn/rn/rn/rn/r
Donor scarInconspicuous lateralBilateral scrotalMidline scrotalBilateral scrotalLarge anteriorBilateral scrotalBilateral scrotalPenoscrotal
Evidence (n)143497188115
Microsurgical skillYesNoNoNoNoNoNoNo

Comparison With Other EPA-Based Flaps​

FlapAuthorYearDesignApplicationKey feature
EPAP hemi-scrotalTsukuura2025Pedicled islanded perforator (scrotal)Penile shaftSensate; perforator isolation; unilateral
STEPA free flapPhoon / Saint-Cyr2014Free flap (scrotal)Hand, foot, head & neckThinnest free flap (~ 1.1 mm); pedicle 11 cm
De-epithelized SEPAAbe1992Pedicled axial (groin / scrotal)Penile reconstruction (Peyronie)De-epithelized for bulk
EPA axial flapBorovikov / Scheplev1990Pedicled axial (groin)Penile granuloma excisionFirst EPA-based penile flap
Keystone KDPIFLee2020Pedicled keystone perforator island (suprapubic-scrotal)Circumferential penile defectDouble-opposing keystone, bilateral SEPA perforators

EPAP differs from STEPA by being pedicled (not free) — no microvascular anastomosis required, only microsurgical perforator dissection. Differs from Borovikov / Abe / Lee by being a true perforator flap (perforator isolated from surrounding fascia) rather than an axial-pattern or keystone design.[1]

Advantages​

  1. True perforator flap — first scrotal flap for penile reconstruction with perforator isolation; maximal mobility and tension-free inset
  2. Sensate by design — deliberate anterior-scrotal-nerve preservation
  3. No dyspareunia / stretching — eliminates pedicle tethering
  4. Unilateral harvest — preserves the contralateral hemiscrotum, reduces donor morbidity, preserves scrotal volume
  5. Inconspicuous donor scar at the lateral scrotum
  6. Primary donor-site closure
  7. Single-stage
  8. Excellent color match — scrotal skin is the best penile-shaft analogue
  9. Thin pliable flap (~ 1.1 mm by STEPA cadaveric data)
  10. 126 cm² from a single hemiscrotum — adequate for circumferential coverage; bilateral harvest not always required

Limitations and Disadvantages​

  1. n = 1 evidence base — Level V; broader adoption requires case-series validation
  2. Requires microsurgical expertise for perforator isolation
  3. Requires preoperative Doppler mapping of the EPA perforator
  4. Anatomic variability — Rab cadaveric study (64 half-cadavers): 4 different cutaneous branching patterns of the ilioinguinal / genitofemoral nerves; bilateral symmetry only 40.6%[18]
  5. Short follow-up (7 months) — long-term sensation durability, skin retraction, late complications unknown
  6. Subjective sensory assessment ("good") without Semmes-Weinstein / two-point discrimination / POSAS
  7. Single-etiology evidence (post-replantation necrosis) — applicability to paraffinoma / LS / AABP / tumor is theoretical
  8. Perforator-injury risk during aggressive dissection — could result in flap loss in a way fasciocutaneous pedicles tolerate
  9. Venous-congestion risk — inherent to islanded perforator flaps if venae comitantes are insufficient[5]

Patient Selection​

Choose EPAPConsider alternative
Circumferential shaft defect with viable deep structuresNo microsurgical expertise → Fakin / Murányi
Post-replantation skin necrosis (index indication)Bilateral scrotal donor needed for very large defect → Zhao total anterior or bilateral techniques
Sensory preservation a priorityScrotal skin insufficient / involved → STSG / FTSG / regional flap[17]
Single-hemiscrotum preserve-contralateral preferredContaminated wound → Pribaz / McLaughlin staged
Confirmed EPA perforator on DopplerVentral-only defect → VSSF
Microsurgical capability availableCompromised proximal pedicle → Gao reverse-flow

Broader Context — Perforator Flaps in Genital Reconstruction​

EPAP is part of a broader trend applying perforator-flap principles to genital reconstruction:[15][19][20][21]

  • Lee 2020 — double-opposing keystone-designed SEPA perforator island flaps for circumferential penile defects
  • Weisberger 2023 — comparative local fasciocutaneous vs pedicled islanded perforator (PAP / ALT) for external-genital reconstruction (n = 24); perforator flaps had longer OR but comparable complications even in irradiated patients
  • Coskunfirat 2011 — medial-circumflex-femoral-artery perforator flap for post-Fournier's scrotal reconstruction (n = 7)
  • Wishart 2021 — vertical posteromedial thigh (vPMT) perforator flap for perianal-genital defects (n = 12)

Key Takeaways​

  • First application of true perforator-flap principles to scrotal penile reconstruction — perforator isolation, islanded design, named-nerve preservation
  • Sensate by design — deliberate ilioinguinal anterior-scrotal-nerve preservation provides innate immediate sensation
  • Unilateral harvest — preserves contralateral hemiscrotum, scrotal volume, and contralateral innervation per the Yucel / Baskin septum-preservation principle
  • Eliminates dyspareunia / stretching seen in fasciocutaneous-pedicle scrotal flaps
  • Level V evidence (n = 1) — promising but requires case-series validation with standardized sensory testing and long-term follow-up
  • Requires microsurgical expertise and preoperative Doppler mapping

Cross-references​

References​

1. Tsukuura R, Engmann T, Miyazaki T, Yamamoto T. "The Sensate External Pudendal Artery Perforator (EPAP) Hemi-Scrotal Flap for the Circumferential Skin Defect of the Penile Shaft: A Case Report and Literature Review." Microsurgery. 2025;45(7):e70123. doi:10.1002/micr.70123

2. Phoon AF, Shah AK, Cormack GC, Saint-Cyr M. "The Super Thin External Pudendal Artery (STEPA) Flap." J Plast Reconstr Aesthet Surg. 2014;67(10):1397–406. doi:10.1016/j.bjps.2014.05.044

3. Fakin R, Zimmermann S, Jindarak S, et al. "Reconstruction of Penile Shaft Defects Following Silicone Injection by Bipedicled Anterior Scrotal Flap." J Urol. 2017;197(4):1166–1170. doi:10.1016/j.juro.2016.11.093

4. McLaughlin MM, Abbassi B, Pribaz JJ. "Bipedicled Scrotal Flap for Penile Resurfacing." Plast Reconstr Surg. 2024;153(4):935–942. doi:10.1097/PRS.0000000000010811

5. Saint-Cyr M, Schaverien MV, Rohrich RJ. "Perforator Flaps: History, Controversies, Physiology, Anatomy, and Use in Reconstruction." Plast Reconstr Surg. 2009;123(4):132e–145e. doi:10.1097/PRS.0b013e31819f2c6a

6. Carrera A, Gil-Vernet A, Forcada P, et al. "Arteries of the Scrotum: A Microvascular Study and Its Application to Urethral Reconstruction With Scrotal Flaps." BJU Int. 2009;103(6):820–4. doi:10.1111/j.1464-410X.2008.08167.x

7. Lohasammakul S, Turbpaiboon C, Ratanalekha R, Ungprasert P, Yodrabum N. "Inferior External Pudendal Artery Anastomosis: Additional Approach to Prevent Skin Necrosis in Replanted Penis." Plast Reconstr Surg. 2018;142(4):535e–540e. doi:10.1097/PRS.0000000000004818

8. Jin B, Hasi W, Yang C, Song J. "A Microdissection Study of Perforating Vessels in the Perineum: Implication in Designing Perforator Flaps." Ann Plast Surg. 2009;63(6):665–9. doi:10.1097/SAP.0b013e3181999de3

9. Borovikov A, Scheplev P. "Axial Flaps for Treatment of Penis Lesions Due to Granulomas." Ann Plast Surg. 1990;25(2):116–8. doi:10.1097/00000637-199008000-00007

10. Yucel S, Baskin LS. "The Neuroanatomy of the Human Scrotum: Surgical Ramifications." BJU Int. 2003;91(4):393–7. doi:10.1046/j.1464-410x.2003.04087.x

11. Amid PK. "A 1-Stage Surgical Treatment for Postherniorrhaphy Neuropathic Pain: Triple Neurectomy and Proximal End Implantation Without Mobilization of the Cord." Arch Surg. 2002;137(1):100–4. doi:10.1001/archsurg.137.1.100

12. Mendel L, Neuville P, Allepot K, et al. "Bilateral Pedicled Scrotal Flaps as an Alternative to Skin Graft in Penile Shaft Defects Repair." Urology. 2023;176:206–212. doi:10.1016/j.urology.2023.03.025

13. Zhao YQ, Zhang J, Yu MS, Long DC. "Functional Restoration of Penis With Partial Defect by Scrotal Skin Flap." J Urol. 2009;182(5):2358–61. doi:10.1016/j.juro.2009.07.048

14. Abe S, Takami Y, Yamaguchi Y, Hata K, Yamaguchi T. "Penile Reconstruction With De-Epithelized Superficial External Pudendal Artery Flap." J Urol. 1992;147(1):155–7. doi:10.1016/s0022-5347(17)37170-7

15. Lee HG, Lim SY, Yoon CS, Kim KN. "Circumferential Penile Defect Reconstruction With Pull-Up Double-Opposing Keystone-Designed Perforator Island Flaps: A Case Report." Medicine. 2020;99(3):e18762. doi:10.1097/MD.0000000000018762

16. Murányi M, Varga D, Kiss Z, Flaskó T. "A New Modified Bipedicle Scrotal Skin Flap Technique for the Reconstruction of Penile Skin in Patients With Paraffin-Induced Sclerosing Lipogranuloma of the Penis." J Urol. 2022;208(1):171–178. doi:10.1097/JU.0000000000002480

17. Kristinsson S, Johnson M, Ralph D. "Review of Penile Reconstructive Techniques." Int J Impot Res. 2021;33(3):243–250. doi:10.1038/s41443-020-0246-4

18. Rab M, Ebmer J, Dellon AL. "Anatomic Variability of the Ilioinguinal and Genitofemoral Nerve: Implications for the Treatment of Groin Pain." Plast Reconstr Surg. 2001;108(6):1618–23. doi:10.1097/00006534-200111000-00029

19. Weisberger JS, Park JB, Cortes R, et al. "Reconstruction of Acquired Defects of the External Genitalia: A 24-Patient, Single-Institution Experience." Ann Plast Surg. 2023;90(6S Suppl 5):S578–S582. doi:10.1097/SAP.0000000000003501

20. Coskunfirat OK, Uslu A, Cinpolat A, Bektas G. "Superiority of Medial Circumflex Femoral Artery Perforator Flap in Scrotal Reconstruction." Ann Plast Surg. 2011;67(5):526–30. doi:10.1097/SAP.0b013e318208ff00

21. Wishart KT, Fritsche E, Scaglioni MF. "Pedicled Vertical Posteromedial Thigh (vPMT) Flap for the Reconstruction of Extensive Perianal-Genital Defects." J Plast Reconstr Aesthet Surg. 2021;74(1):123–129. doi:10.1016/j.bjps.2020.08.001