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Bilobed Flap

The bilobed flap is a double transposition flap consisting of two lobes that share a common pivot point. It recruits tissue from an area of greater laxity through a sequential relay: the primary lobe fills the defect, the secondary lobe fills the primary lobe's donor site, and the secondary donor site is closed primarily.[1][2] The flap is best known for nasal reconstruction. The bilobed principle has been adapted to urologic and urogynecologic reconstruction through regional-flap modifications, particularly the bilobed pudendal artery perforator (PAP) flap and the bilobed gracilis myocutaneous flap.

Geometric Principle​

The bilobed flap was originally described by Esser (1918) with two equal-sized lobes at 90° and 180° from the defect. Zitelli's nasal-flap modification (1989) reduced the total arc of rotation to approximately 90–100°, with each lobe pivoting about 45° from the preceding one, to reduce standing cutaneous deformity (SCD, or "dog ear") and pincushioning.[3][4]

Key design elements​

ElementDetail
Pivot pointGeometric center around which both lobes rotate. Pivot placement is a key determinant of flap mechanics in a geometric analysis of the nasal bilobed flap: altering the SCD size or orientation shifts the pivot point and changes the effective arc of rotation[5]
Primary lobeFills the defect. In Xue's modified nasal design, its width equals the defect diameter and its length is 10% greater than the pivot-to-distal-defect distance; these are nasal-design measurements.[6]
Secondary lobeNarrower than the primary lobe (two-thirds of its width in Xue's modified nasal design); fills the primary-lobe donor site; the smaller size allows primary closure of the secondary donor site[6]
Standing cutaneous deformity (SCD)Triangle of redundant tissue excised at the base to allow rotation. Mathematical modeling shows that altering SCD length or orientation changes the pivot location, requiring compensatory adjustment of the rest of the design[5]
Total arc of rotation~90–100° (Zitelli) vs. 180° (Esser) — reduces tissue distortion and secondary motion[3][4]

A triangle template method facilitates flap design: an equilateral triangle is constructed with one vertex at the center of the defect and the opposite side serving as the base of the secondary lobe, which places the pivot correctly.[7]

Why bilobed differs from single-flap transpositions​

The bilobed flap distributes the tension of closure across two sequential transpositions instead of concentrating it in a single flap (as in the rhomboid / Limberg flap). It suits areas where tissue laxity is asymmetrically distributed. The secondary lobe can be oriented toward the zone of greatest laxity while the primary lobe is directed toward the defect.[1]

Urologic Applications​

Bilobed gracilis myocutaneous flap — perineal and genital reconstruction​

A urologic adaptation of the bilobed principle is the bilobed gracilis flap, developed by Vyas and Pomahac (2010) and refined by Weinstein et al. (2020).[8][9]

Rationale. The traditional gracilis myocutaneous flap has a known limitation: when harvested with a vertical skin paddle, distal-tip necrosis is a well-documented complication because of inconsistent perforator anatomy. Orienting the paddle transversely gives a reliable alternative with a shorter rotational arc, but the skin paddle is smaller when primary closure is desired. Vyas and Pomahac designed the bilobed paddle to address both problems (technique description with two illustrative cases):[8]

  • A larger transverse primary lobe (with a shorter arc of rotation) is transposed into the perineal or genital defect
  • A shorter vertical secondary lobe is inset into the transverse donor site instead of into the wound bed, which incorporates the transverse and longitudinal dimensions of the gracilis muscle's nearly circular angiosome
  • The design allows harvest of a larger total skin paddle than a single transverse or vertical paddle

Clinical experience.

  • Weinstein et al. (2020) reported 6 bilobed gracilis flaps (5 oncologic perineal defects, 1 Fournier's gangrene). Chemotherapy, radiation and compromised abdominal donor sites characterized the oncologic patients; applicability to the Fournier patient is limited. The bilobed gracilis provided soft-tissue bulk for deep, irregularly contoured defects where the VRAM flap was unavailable.[9]
  • In this six-flap report, the authors proposed use for moderate-to-large perineal or genital defects, defects requiring substantial soft-tissue bulk, and patients with limited abdominal donor sites.[9]

This flap is relevant in urologic practice for reconstruction after abdominoperineal resection, pelvic exenteration and Fournier's gangrene, settings where the VRAM flap may be unavailable.

Related but distinct — bilateral scrotal flap designs​

Modified bilateral scrotal flaps, described as "butterfly" configurations, use a pedicled flap from each side of the scrotal midline for penile-skin defects. They are two opposing flaps and differ from the shared-pivot, sequential two-lobe transposition defined above.[10][11]

  • 7-patient series: bilateral scrotal flaps achieved significant increases in flaccid and erectile penile length, with only 2 cases of minor partial necrosis managed conservatively[10]
  • 22-patient series (including buried penis and foreign-body injection): bilateral pedicled scrotal flaps had 27.3% late surgical revision. Among the 12 questionnaire respondents, median global satisfaction was 8/10 and erection-hardness 3.5/4. Skin retraction occurred in 27.3%, but not every revision was attributed to retraction.[11]

A separate retrospective series of eight patients with Fournier-related total scrotal skin loss used a bilobed pudendal-thigh flap, with one lobe covering the defect and the other the first lobe's donor site. One patient had a 2-cm wound separation on postoperative day 5, closed by suturing; follow-up ranged from 7 to 19 months.[18] The authors caution that debridement may damage the pudendal perforators supplying the flap.[18]

Urogynecologic Applications​

Bilobed pudendal artery perforator (PAP) flap — vulvar and perineal reconstruction​

Yun et al. (2010) described the bilobed PAP flap, designed for the anatomy of the perineum.[12]

Here PAP means pudendal artery perforator, as in Yun's paper. In other reconstructive literature PAP may mean profunda artery perforator, a different donor territory.[12][13]

Anatomic rationale. The perineum consists of two functionally distinct triangles, the urogenital triangle (anterior) and the anal triangle (posterior), which differ in tissue characteristics and function. For defects spanning both triangles, Yun and colleagues proposed a bilobed design to orient tissue into each component; their series also used six unilobed flaps and did not compare the two designs.[12] The authors state that the bilobed design offers:[12]

  • An improved arc of rotation; the two lobes can be independently oriented to cover wide, irregularly shaped defects
  • Increased flap mobility, which allows coverage of deep defects
  • Preservation of the functional characteristics of each triangle; each lobe can be tailored to match its recipient tissue

Clinical results (15 female patients):[12]

  • Indications: 7 vulvar cancer, 7 extramammary Paget's disease, 1 rectovaginal fistula
  • 9 bilobed flaps and 6 unilobed flaps, selected based on defect location and shape
  • Flap sizes ranged from 3 × 4 cm to 13 × 12 cm
  • All 15 pudendal artery perforator flaps (9 bilobed, 6 unilobed) survived during the mean 4.6-month follow-up.[12]
  • All reconstructed areas achieved good functional and aesthetic conditions

Yun's authors selected a bilobed or a unilobed PAP configuration according to defect location and shape, including defects crossing the urogenital and anal triangles.[12]

Perineal body reconstruction after obstetric injury​

Jandali et al. (2010) described bilateral pedicled bilobed flaps for reconstruction of cloacal-like defects after fourth-degree obstetric lacerations:[14]

  • Fourth-degree lacerations can destroy the anterior anal sphincter and thin the perineum / rectovaginal septum, causing fecal incontinence and sexual dysfunction
  • The technique combines anterior anal-sphincter repair with perineal body reconstruction using bilateral bilobed flaps
  • The authors describe bilobed flaps as a way to supply bulk for the perineal body and rectovaginal septum (technique report; no outcome data are reported in the abstract)

For cloacal-like defects after fourth-degree obstetric laceration, Jandali et al. described bilateral bilobed flaps combined with anterior anal-sphincter and perineal-body repair.[14]

Vulvar reconstruction algorithms​

The Toulouse Algorithm (Ricotta et al., 2025) is a location-based proposal for vulvar cancer reconstruction that favors perforator flaps when feasible.[13]

Ricotta and colleagues reserve musculocutaneous flaps for selected situations where perforator options are unsuitable. Ricotta and colleagues' algorithm offers no bilobed comparison or evidence of equivalent coverage across defects.[13] A separate 2024 meta-analysis of 49 studies in 1,840 women undergoing vulvoperineal reconstruction after oncologic resection found no statistically significant difference in overall short-term complications between perforator (n = 276) and nonperforator (n = 1,564) groups. It did not test bilobed geometry, and patient-reported quality-of-life data were scarce.[16]

Hong et al. (2017) described multiple separate pedicled perforator flaps for extensive perineal defects: 37 flaps in 16 patients (mean 2.31 flaps per patient), with no flap losses or donor-site complications in that series.[15]

Comparison with Other Geometric Flap Techniques​

FeatureBilobedRhomboid (Limberg)Z-plastyV-Y advancement
MechanismDouble transposition via two sequential lobesSingle transposition into a rhomboid defectTransposition of two triangular flapsAdvancement into a defect
Arc of rotationVaries by flap and defect; approximately 90–100° in the Zitelli nasal design[3][4][8][12]~60°VariableNone (linear advancement)
Key advantageRecruits tissue from zone of maximal laxity via relaySimple, predictable geometryScar reorientation up to 90°No transposition; perforator-based
Tension distributionAcross two transpositionsConcentrated at single closureRedistributed along new axisAlong advancement vector
Best forAsymmetric tissue laxity; multi-compartment defectsSmall–moderate defects with adequate adjacent tissueCircumferential contracturesTissue advancement into a defect
Urologic nichePerineal / genital reconstruction (bilobed gracilis)Epispadias-exstrophy, scrotal reconstructionHypospadias revision, phimosisPenile lengthening, Fournier's
Urogynecologic nicheVulvoperineal defects spanning both triangles; perineal-body reconstructionSmall posterior vulvar defectsTransverse vaginal septum, vaginal constrictionVulvovaginal oncologic defects

When to Reach for the Bilobed Flap in GU Reconstruction​

  • Defects that are irregularly shaped or span multiple anatomic compartments (urogenital and anal triangle), or where tissue laxity is asymmetrically distributed.[9][12]
  • The usual flap is unavailable (prior VRAM harvest, hostile abdomen, ostomy adjacent to the planned skin paddle).[9]
  • Reported bilobed configurations:
    • Bilobed PAP flap. Vulvoperineal defects spanning both triangles.[12]
    • Bilobed gracilis. Deep pelvic or perineal defects requiring bulk after APR, exenteration or Fournier's gangrene.[8][9]
    • Bilateral bilobed perineal flaps. Perineal-body reconstruction after fourth-degree obstetric injury.[14]

Limitations: more complex design and execution than single-lobed transposition flaps; requires careful pivot-point planning; the secondary lobe must be oriented toward adequate tissue laxity for primary closure.[1][5]

Technical Pearls​

  • Plan the pivot point first, then design both lobes outward from it. Changing the SCD length or orientation moves the pivot and requires redesign of the rest of the flap (nasal geometric model).[5][7]
  • Make the secondary lobe narrower than the primary (two-thirds of the primary width in Xue's modified nasal design). Zitelli's modification of Esser's original two-equal-lobe geometry was introduced to reduce pincushioning and standing deformity.[3][4][6]
  • Orient the secondary lobe toward the zone of greatest tissue laxity and not toward an aesthetic axis. The secondary donor site is what closes primarily, so its laxity determines whether the design works.
  • Use the triangle-template method for design discipline, especially when learning the flap.[7]
  • In bilobed gracilis, harvest the transverse paddle as the primary lobe and the vertical paddle as the secondary lobe, which preserves the reliable proximal angiosome for the recipient site.[8][9]
  • In bilobed PAP, map perforators with handheld Doppler before incision to guide the lobe design. If oncologic resection is performed, reassess the signal before finalizing the flap design, as described for a related gluteal-fold flap based on internal pudendal perforators.[17]

See Also​

References​

1. Miller CJ. "Design Principles for Transposition Flaps: The Rhombic (Single-Lobed), Bilobed, and Trilobed Flaps." Dermatol Surg. 2014;40(Suppl 9):S43–S52. doi:10.1097/DSS.0000000000000115

2. Mehta JS, Olver JM. "Infraglabellar Transnasal Bilobed Flap in the Reconstruction of Medial Canthal Defects." Arch Ophthalmol. 2006;124(1):111–115. doi:10.1001/archopht.124.1.111

3. Yong JS, Christophel JJ, Park SS. "Repair of Intermediate-Size Nasal Defects: A Working Algorithm." JAMA Otolaryngol Head Neck Surg. 2014;140(11):1027–1033. doi:10.1001/jamaoto.2014.2258

4. Bennett A, Peters V, Meade A, Thornton J. "A Comprehensive Review of Bilobed Flaps in Nasal Reconstruction: Technique, Outcomes, and Considerations." J Craniofac Surg. 2024;35(7):2146–2149. doi:10.1097/SCS.0000000000010466

5. Pelster MW, Maher IA. "One-Sized Bilobed Flap Does Not Fit All Standing Cones: A Mathematical Analysis of the Standing Cone in Bilobed Flap Dynamics." Arch Dermatol Res. 2023;315(3):401–407. doi:10.1007/s00403-022-02361-z

6. Xue CY, Li L, Guo LL, Li JH, Xing X. "The Bilobed Flap for Reconstruction of Distal Nasal Defect in Asians." Aesthetic Plast Surg. 2009;33(4):600–604. doi:10.1007/s00266-009-9336-x

7. Man LX, Chang B. "A Simple Method of Designing a Bilobed Flap Using a Triangle Template." Dermatol Surg. 2004;30(10):1345–1348. doi:10.1111/j.1524-4725.2004.30408.x

8. Vyas RM, Pomahac B. "Use of a Bilobed Gracilis Myocutaneous Flap in Perineal and Genital Reconstruction." Ann Plast Surg. 2010;65(2):225–227. doi:10.1097/SAP.0b013e3181c9c434

9. Weinstein B, King KS, Triggs W, Harrington MA, Pribaz J. "Bilobed Gracilis Flap: A Novel Alternative for Pelvic and Perineal Reconstruction." Plast Reconstr Surg. 2020;145(1):231–234. doi:10.1097/PRS.0000000000006341

10. Yao H, Zheng D, Xie M, et al. "A Modified Bilateral Scrotal Flap for Penile Skin Defect Repair." J Vis Exp. 2022;(189). doi:10.3791/64017

11. 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

12. Yun IS, Lee JH, Rah DK, Lee WJ. "Perineal Reconstruction Using a Bilobed Pudendal Artery Perforator Flap." Gynecol Oncol. 2010;118(3):313–316. doi:10.1016/j.ygyno.2010.05.007

13. Ricotta G, Russo SA, Ferron G, Meresse T, Martinez A. "The Toulouse Algorithm: Vulvar Cancer Location-Based Reconstruction." Int J Gynecol Cancer. 2025;35(4):100065. doi:10.1016/j.ijgc.2024.100065

14. Jandali S, Noone RB, Pearson PY, Noone RB. "Perineal Reconstruction With Bilateral Bilobed Flap for Cloacal-Like Defect After Childbirth." Ann Plast Surg. 2010;64(1):62–64. doi:10.1097/SAP.0b013e31819ae0a6

15. Hong JP, Kim CG, Suh HS, et al. "Perineal Reconstruction With Multiple Perforator Flaps Based on Anatomical Divisions." Microsurgery. 2017;37(5):394–401. doi:10.1002/micr.30152

16. Wendelspiess S, Kouba L, Stoffel J, et al. "Perforator versus Non-Perforator Flap-Based Vulvoperineal Reconstruction-A Systematic Review and Meta-Analysis." Cancers (Basel). 2024;16(12):2213. doi:10.3390/cancers16122213

17. Thiele JR, Weber J, Neeff HP, et al. "Reconstruction of Perineal Defects: A Comparison of the Myocutaneous Gracilis and the Gluteal Fold Flap in Interdisciplinary Anorectal Tumor Resection." Front Oncol. 2020;10:668. doi:10.3389/fonc.2020.00668

18. Abaci M, Baran Ö. "Reconstruction of Scrotal Skin Defects Using Bilobed Pudendal Flap." J Cutan Aesthet Surg. 2022;15(4):400–404. doi:10.4103/JCAS.JCAS_233_20