What are the different types of flaps used for hypospadias repair?

Flaps Used for Hypospadias Repair

For hypospadias repair, the primary flap options include transverse preputial island flaps (either onlay or tubularized), penile fasciocutaneous flaps, and two-stage flap techniques, with onlay island flaps demonstrating superior outcomes by avoiding diverticulum formation while maintaining low fistula rates.

Primary Flap Techniques

Transverse Preputial Island Flaps

The transverse preputial island flap represents the workhorse technique for proximal hypospadias repair and can be configured in two ways 1, 2:

• Onlay island flap: Applied as a patch onto an intact urethral plate, this technique preserves the native urethral plate and demonstrates a 10% complication rate for mid to posterior hypospadias 2. The onlay approach results in smaller fistulas when they occur and notably prevents diverticulum formation entirely 1.

• Tubularized island flap: Created by tubularizing the flap after urethral transection, this technique shows a 36% overall complication rate with a 14% fistula rate 1. A critical limitation is the development of diverticula in approximately 12% of cases, which does not occur with onlay repairs 1.

The onlay technique is superior when the urethral plate is well-developed and exhibits minimal chordee after skin release, as it avoids the diverticulum formation seen with tubularization 1, 2.

Penile Fasciocutaneous Flaps

Penile circular fasciocutaneous flaps, first described by McAninch, are utilized for complex anterior urethral strictures and can be applied to long multi-segment strictures in hypospadias-related cases 3. The American Urological Association guidelines recommend these flaps for reconstruction of panurethral strictures exceeding 10 cm, often in combination with oral mucosal grafts 3.

Critical caveat: When hypospadias is associated with lichen sclerosus, genital skin flaps have a 100% failure rate and should never be used 3. Only nongenital tissue grafts (buccal mucosa, bladder mucosa) are appropriate in this context 3.

Two-Stage Flap Techniques

Standard Two-Stage Approach

The two-stage flap repair involves 4, 5:

1. First stage: Mobilization of preputial or dorsal penile skin to the ventral surface (Retik technique) 4
2. Second stage (after minimum 6 months): Tubularization with multilayered closure 4

Traditional two-stage flap repairs historically showed diverticulum rates of 20-63%, which led some surgeons to abandon the technique 4.

Modified Two-Stage with Tubularized Incised Plate

Incorporating a midline incision into the two-stage flap repair (similar to Snodgrass technique) eliminates diverticulum formation entirely while maintaining a 14% fistula rate 4. This modification involves:

• Preliminary midline incision on the neo-urethral plate during the second stage 4
• Tubularization followed by multilayered closure 4
• Results in 80% satisfactory outcomes with zero diverticula or strictures 4

Technical Considerations for Flap Selection

When to Preserve the Urethral Plate

Preservation of the urethral plate is a fundamental principle that extends to mid and posterior hypospadias when the plate is well-developed and chordee is minimal after skin release 2. This approach:

• Reduces complications from 36% to 10% compared to tubularized techniques 1, 2
• Applies to 38% of mid to posterior hypospadias cases that would traditionally require more extensive reconstruction 2

Flap Coverage Principles

Modern hypospadias surgery incorporates deepithelialized dartos flap coverage as a major technical advance 5. This provides:

• Vascularized tissue layer between urethroplasty and skin 5
• Reduced fistula formation 5

Common Pitfalls to Avoid

1. Never use genital skin flaps in lichen sclerosus-associated hypospadias: All 12 patients treated with pedicled penile skin flaps in one series failed, requiring further surgery 3.

2. Avoid tubularization when the urethral plate is intact: Tubularized repairs create larger fistulas requiring more complex repair and cause diverticula that onlay repairs do not 1.

3. Do not use hair-bearing skin: This results in urethral calculi, recurrent UTI, and urinary obstruction 3.

4. Avoid single-stage tubularized urethroplasty for complete urethral replacement: This approach has high restenosis rates and should be avoided 3.

Adjunctive Tissue Options

For complex cases requiring additional tissue beyond standard flaps 3, 6:

• Buccal mucosa grafts: First-line choice for grafts, superior patient satisfaction 3
• Bladder mucosa: Alternative graft source 3
• Rectal mucosa: Less commonly used alternative 3
• Tunica vaginalis: Can provide coverage when primary closure impossible 3

The modern hypospadiologist must be proficient with both vascularized flaps and free grafts, selecting technique based on urethroplasty length, degree of ventral curvature, and surgeon experience 6.