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 preservation of the anterior scrotal nerve — to cover a circumferential penile-shaft skin defect. Tsukuura and colleagues (Microsurgery 2025) reported one patient with an uneventful short-term course, good subjective sensation and color match, and no pain or stretching sensation at 7 months. These observations do not establish comparative sensory or sexual-function superiority.[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
The case authors proposed perforator isolation as an alternative to broader-pedicle scrotal designs. Their comparison is a technical rationale, not a measured head-to-head finding:[1]
- Broad bilateral pedicles may use more scrotal tissue; bilateral EPA sacrifice is not established for every other design
- Pedicle tethering or stretching is a possible concern, not a proven universal cause of dyspareunia
- Donor-scar extent depends on the chosen design
- A potentially different rotation arc, without a measured head-to-head comparison
- Two-stage for some designs (Pribaz)
EPAP applies the perforator-flap concept — isolating the source-artery perforator from surrounding fascia — to the scrotum. This can increase design mobility and allowed inset in the reported case; elimination of tethering and superior patient outcomes remain hypotheses requiring more cases.[1][2]
Vascular Anatomy
External pudendal artery system[3][4][5][17]
- 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 from Phoon's separate free-STEPA study (6 cadavers; not measurements from the pedicled EPAP patient):[17]
- 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)[4]
- Jin microdissection (11 cadavers, 22 sides): 4 relatively constant perineal perforating branches including inguinal and perineal superficial external-pudendal branches — a cadaveric anatomy finding, not proof of a constant patient-level EPAP course[5]
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"[3]
The perforator-isolation innovation
The described technical difference is isolating the EPA perforator from surrounding fascia to island the flap. In one case this permitted transfer and inset; its comparative rotation arc and long-term tension effects have not been measured against other scrotal-flap designs.[1]
Neural Anatomy and Sensate Design
Scrotal innervation[7][8]
| Nerve | Origin | Territory |
|---|---|---|
| Anterior scrotal nerves | Ilioinguinal nerve (L1) | Anterior and lateral scrotal skin |
| Genital branch of genitofemoral | L1–L2 | Cremasteric muscle + scrotal skin |
| Posterior scrotal nerves | Perineal 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 was isolated and preserved in the reported pedicle. Good sensation was described at seven months, without standardized sensory testing or proof that this design outperforms other innervated or non-innervated local flaps.[1]
Septal preservation
Yucel & Baskin described scrotal sensory anatomy, including the septal region. A unilateral design leaves the contralateral hemiscrotum unharvested, but preservation of its sensation was not measured in the EPAP case.[7][1]
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
- A single hemiscrotum can provide coverage when its dimensions and vascularity suffice (9 × 14 cm in the index case)
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 isolated pedicle onto the denuded shaft, checking perfusion and pedicle tension; the cited case does not establish a universal 180° rotation limit
- 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]
| Parameter | Result |
|---|---|
| Patient | 40-year-old male, schizophrenia |
| Etiology | Circumferential penile skin necrosis after replantation for self-inflicted amputation |
| Time from replantation | 12 days |
| Flap dimensions | 9 × 14 cm |
| Donor | Right hemiscrotum |
| Plane | Suprafascial |
| Perforator | EPA perforator (isolated) |
| Nerve preserved | Anterior scrotal nerve (ilioinguinal) |
| Staging | Single-stage |
| Flap survival | Complete in this one case |
| Short-term complications | None |
| Follow-up | 7 months |
| Color match | Excellent |
| Sensation | Good (via anterior scrotal nerve) |
| Pain / stretching | None reported at seven months; dyspareunia was not separately quantified |
| Erectile function | Recovered |
| Donor scar | Inconspicuous (lateral scrotum) |
Key Innovations vs Traditional Scrotal Flaps
- Perforator isolation (islanded design) — technically different from broad-pedicle designs; a comparative reduction in tension or stretching has not been demonstrated.[1]
- Unilateral harvest — one hemiscrotum supplied the index flap, leaving the other unharvested; donor morbidity cannot be compared with Mendel's distinct bilateral-flap cohort.[1][9]
- Deliberate named-nerve preservation — anterior scrotal nerve continuity was documented; the mechanism of sensation recovery in Zhao's separate cohort was not established.[1][10]
- No pain or stretching reported at seven months — encouraging single-case observation, not proof that pedicle isolation eliminates dyspareunia.[1]
Comparison Across All Major Scrotal-Flap Techniques
| Feature | EPAP (Tsukuura) | Fakin | Murányi | Yao | Zhao total | Pribaz staged | Gao reverse | VSSF |
|---|---|---|---|---|---|---|---|---|
| Flap type | Islanded perforator | Fasciocutaneous pedicle | Fasciocutaneous pedicle | Fasciocutaneous pedicle | Fasciocutaneous pedicle | Fasciocutaneous pedicle (staged) | Reverse-flow fasciocutaneous | Local rotation |
| Hemiscrotums used | 1 (unilateral) | Bilateral pedicle territory | Midline tunnel/bilateral pedicles | Bilateral | Entire anterior | Bilateral | Bilateral | Bilateral partial |
| Perforator isolated | Yes | No | No | No | No | No | No | No |
| Named nerve preservation reported | Yes (anterior scrotal) | Not established in this comparison | Not established | Not established | Not established | Not established | Not established | Not established |
| Rotation arc | Islanded design; no comparative angle measured | Not compared | Not compared | Not compared | Not compared | n/a (staged) | Not compared | Not compared |
| Staging | Single | Single | Single | Single | Single | Two | Single | Single |
| Pain / stretching | None reported in one case at 7 months | n/r | 3/30 reported pain/tension on erection | n/r | n/r | n/r | n/r | n/r |
| Donor scar | Inconspicuous lateral | Bilateral scrotal | Midline scrotal | Bilateral scrotal | Large anterior | Bilateral scrotal | Bilateral scrotal | Penoscrotal |
| Evidence (n) | 1 | 43 | 49 | 7 | 18 | 8 | 1 | 15 |
| Microsurgical skill | Yes | No | No | No | No | No | No | No |
Comparison With Other EPA-Based Flaps
| Flap | Author | Year | Design | Application | Key feature |
|---|---|---|---|---|---|
| EPAP hemi-scrotal | Tsukuura | 2025 | Pedicled islanded perforator (scrotal) | Penile shaft | Sensate; perforator isolation; unilateral |
| STEPA free flap | Phoon / Saint-Cyr | 2014 | Free flap (scrotal) | Proposed for thin-tissue reconstruction | Cadaveric mean thickness ~1.1 mm; pedicle 11 cm[17] |
| De-epithelized SEPA | Abe | 1992 | Pedicled axial (groin / scrotal) | Penile reconstruction (Peyronie) | De-epithelized for bulk |
| EPA axial flap | Borovikov / Scheplev | 1990 | Pedicled axial (groin) | Penile granuloma excision | Earlier EPA-based penile flap[6] |
| Keystone KDPIF | Lee | 2020 | Pedicled keystone perforator island (suprapubic-scrotal) | Circumferential penile defect | Double-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
- True perforator flap — isolated perforator allowed transfer and inset in one reported patient; comparative mobility remains untested
- Sensate by design — deliberate anterior-scrotal-nerve preservation
- No pain or stretching reported at seven months; long-term sexual outcomes are unknown
- Unilateral harvest — leaves the contralateral hemiscrotum unharvested; donor-morbidity reduction is unproven
- Inconspicuous donor scar at the lateral scrotum
- Primary donor-site closure
- Single-stage
- Good color match in the index patient; texture and hair distribution require individual assessment
- Thin pliable tissue — separate STEPA cadaveric measurements should not be assumed to describe every EPAP flap
- 9 × 14 cm in one hemiscrotum — adequate for that patient's defect; bilateral harvest is not always required
Limitations and Disadvantages
- n = 1 evidence base — Level V; broader adoption requires case-series validation
- Requires microsurgical expertise for perforator isolation
- Requires preoperative Doppler mapping of the EPA perforator
- Anatomic variability — Rab cadaveric study (64 half-cadavers): 4 different cutaneous branching patterns of the ilioinguinal / genitofemoral nerves; bilateral symmetry only 40.6%[13]
- Short follow-up (7 months) — long-term sensation durability, skin retraction, late complications unknown
- Subjective sensory assessment ("good") without Semmes-Weinstein / two-point discrimination / POSAS
- Single-etiology evidence (post-replantation necrosis) — applicability to paraffinoma / LS / AABP / tumor is theoretical
- Perforator-injury risk during aggressive dissection — could result in flap loss in a way fasciocutaneous pedicles tolerate
- Venous-congestion risk — inherent to islanded perforator flaps if venae comitantes are insufficient[2]
Patient Selection
| Choose EPAP | Consider alternative |
|---|---|
| Circumferential shaft defect with viable deep structures | No 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 priority | Scrotal skin insufficient / involved → STSG / FTSG / regional flap[12] |
| Single-hemiscrotum preserve-contralateral preferred | Inadequately controlled infection or unsuitable wound bed → debridement and individualized reconstruction plan |
| Confirmed EPA perforator on Doppler | Ventral-only defect → VSSF |
| Microsurgical capability available | Compromised 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:[11][14][15][16]
- 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
- Reported perforator-isolation approach to scrotal penile coverage, with a named nerve preserved in one case
- Sensory intent — anterior-scrotal-nerve preservation was documented; good subjective sensation was reported at seven months
- Unilateral harvest — leaves the contralateral hemiscrotum unharvested; its sensation and comparative donor morbidity were not measured
- No pain or stretching reported in this case; dyspareunia prevention versus other designs remains untested
- 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
See Also
- Penile Reconstruction — full decision framework
- Bipedicled Anterior Scrotal Flap (Fakin)
- Modified Bipedicle Scrotal Tunnel Flap (Murányi)
- Modified Bilateral Butterfly Scrotal Flap (Yao)
- Total Anterior Scrotal Flap (Zhao)
- Staged Bipedicled Scrotal Flap (Pribaz / McLaughlin)
- Reverse Bilateral Anterior Scrotal Artery Flap (Gao)
- Ventral Slit Scrotal Flap (VSSF)
- Penile Skin Grafting
- Scrotal Reconstruction
- Foundations — Plastic Surgery Principles
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. 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
3. 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
4. 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
5. 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
6. 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
7. 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
8. 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
9. 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
10. 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
11. 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
12. 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
13. 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
14. 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
15. 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
16. 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
17. 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):1397–1406. doi:10.1016/j.bjps.2014.05.044