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Singapore Flap Urethroplasty

The Singapore flap — also known as the pudendal thigh fasciocutaneous flap (PTF) related to, but not synonymous with, the broader internal pudendal artery perforator (IPAP) flap family — is a sensate fasciocutaneous flap from the labiocrural / groin-crease fold first described by Wee and Joseph at Singapore General Hospital in 1989 for vaginal reconstruction.[1] Its application to urethroplasty is a limited-evidence extension of a well-established perineal-reconstructive workhorse, with the published urological experience represented here by a case report, a mixed-indication flap series and one phalloplasty cohort.[2][3][4]

For the flap itself — nomenclature, vascular anatomy (perforator counts, Colles' fascia relationships, sensory innervation), surgical technique, vulvovaginal / RVF / vulvar-oncologic / Fournier's / pediatric / burn-contracture applications, and the broader complication and head-to-head literature — see Singapore / Pudendal Thigh Flap in foundations. This page is intentionally limited to the urethroplasty application.

For the gluteal-fold variant used predominantly for vulvar oncologic and male perineal / scrotal reconstruction, see Lotus Petal Flap. For the urethroplasty alternative when local penile and perineal options are exhausted, see Propeller Flap Urethroplasty.

Published Urological Applications​

The following reports illustrate the limited urethral experience; they are not an exhaustive systematic review:

1. Tzarnas 1994 — first reported urethroplasty use​

The earliest reported urological application of the pudendal thigh fasciocutaneous flap was for a traumatic posterior urethral stricture after vaginoplasty (gender-affirming surgery). The anatomic constraints of the reassigned perineum precluded standard urethroplasty options, and the pudendal thigh flap was used to bridge the defect. The stricture was successfully corrected with an inconspicuous donor-site scar.[2]

2. Monstrey 2001 — posterior urethral defects in a scarred perineum​

In the largest dedicated Singapore-flap series (31 flaps across vaginal, vulvar, RVF, and urethral indications), Monstrey reported the technique in 2 patients with posterior urethral defects in heavily scarred perineums where local tissue was insufficient.[3] Both flaps survived completely with excellent functional outcomes; some hair growth was noted within the flaps — a recognized concern when fasciocutaneous tissue is used as urethral lining.

3. Wu 2022 — neourethral reconstruction in pedicled ALT phalloplasty​

Wu reported 49 patients receiving pedicled ALT penile reconstruction for micropenis, trauma or iatrogenic defects; this was not a gender-affirming phalloplasty cohort. Eleven were listed as receiving a pudendal-thigh neourethra.[4]

The abstract reports 38.5% urethral complications for that subgroup, but this percentage does not reconcile with the stated denominator of 11. The exact subgroup rate remains unresolved and should not guide comparative counseling. Techniques were selected according to patient characteristics, so the cohort does not establish that a pudendal-thigh flap has the lowest complication risk. All patients reportedly voided standing after necessary revisions.[4]

Why a Singapore Flap for Urethroplasty​

When local penile and perineal tissue is exhausted, scarred, or anatomically reorganized (post-GAS, post-pelvic-trauma, post-radiation), the Singapore flap brings several urethroplasty-relevant advantages:

  • Sensate — retains cutaneous innervation from the perineal nerves, important for genital reconstruction.[1][3]
  • Tissue from outside the immediate zone of injury — donor site is a non-operated groin / labiocrural fold.[2][3]
  • Superficial perineal arterial supply from the internal pudendal system. All 31 flaps survived in Monstrey's mixed-indication series; this is not a generalizable urethral success rate.[3]
  • Thin and pliable — adapts to perineal urethral and neourethral defects without excessive bulk.
  • Primary donor-site closure, scar hidden in the natural groin fold.[3]

Limitations Specific to Urethroplasty​

  • Hair-bearing skin — the flap may carry hair follicles, with downstream risk of stone formation, infection, and intraluminal hair when used as urethral lining.[3]
  • Best suited for posterior / perineal urethral defects, not long anterior penile strictures — the arc of rotation and dimensions limit anterior reach.
  • No comparative data vs BMG or penile fasciocutaneous flaps for urethroplasty.
  • Small, heterogeneous cohorts — native-urethral repair and neourethral construction should not be pooled as one effectiveness estimate.
  • Three-territory vascular anatomy — larger flaps may have a precarious apex; for technical mitigation (delay procedure, IPAP perforator-based design), see the foundations Singapore flap page.

Where It Fits in the Urethroplasty Algorithm​

The Singapore flap is not a primary urethroplasty option. It is reserved for:

  • Posterior urethral defects in a scarred or anatomically altered perineum when local rotation flaps are not available — including post-GAS strictures.[2][3]
  • Neourethral reconstruction within pedicled-ALT phalloplasty when anatomy and reconstructive needs favor separate urethral tissue; comparative risk superiority is unproven.[4]
  • Salvage scenarios with concurrent perineal soft-tissue defects requiring resurfacing alongside urethral reconstruction.

For first-line operative options, see Distal Penile Circular Fasciocutaneous Flap (McAninch), Buccal Mucosa Graft, and the Master Decision Framework.

References​

1. Wee JT, Joseph VT. A new technique of vaginal reconstruction using neurovascular pudendal-thigh flaps: a preliminary report. Plast Reconstr Surg. 1989;83(4):701-709. doi:10.1097/00006534-198904000-00018.

2. Tzarnas CD, Raezer DM, Castillo OA. A unique fasciocutaneous flap for posterior urethral repair. Urology. 1994;43(3):379-381. doi:10.1016/0090-4295(94)90084-1.

3. Monstrey S, Blondeel P, Van Landuyt K, et al. The versatility of the pudendal thigh fasciocutaneous flap used as an island flap. Plast Reconstr Surg. 2001;107(3):719-725. doi:10.1097/00006534-200103000-00011.

4. Wu Q, Yang Z, Ma N, Wang W, Li Y. Urethra reconstruction and revision urethroplasty in pedicled anterolateral thigh flap penile reconstruction. Ann Plast Surg. 2022;89(2):201-206. doi:10.1097/SAP.0000000000003100.