Subunit-Based Intraflap Debulking Technique for Secondary Contouring After Free Flap Reconstruction

Authors: Yoo K-E, Lee K-T

Affiliation: Samsung Med Center, Sungkyunkwan School of Medicine, Seoul, Korea

Journal: Microsurgery, 2026

PMID: 42231540

Key takeaways

• Intraflap incisions placed along anatomic subunit boundaries allow direct access to central flap bulk while limiting unnecessary peripheral dissection.

• In 22 selected cases, there were no wound-healing complications, infections, hematomas, seromas, or reoperations.

• Most patients were successfully treated through a single intraflap incision, although 6 required addition debulking procedures.

Background

Secondary debulking is frequently needed when a free flap remains thicker than adjacent native tissue. Conventional margin-based approaches can require dissection through already-thin peripheral flap tissue to reach central fullness, particularly near the original pedicle.

Objective

Evaluate the safety and clinical utility of a subunit-based intraflap debulking technique in which incisions are placed across the flap along natural anatomic boundaries to directly address central bulk.

Methods

• Design: Retrospective, single-center case series using a prospectively maintained database.

• Study period: December 2021 to August 2025.

• Population: 22 patients with free flaps spanning multiple anatomic subunits who subsequently underwent intraflap secondary debulking.

• Mean age: 59 years.

• Mean BMI: 25.1 kg/m².

• Anatomic distribution:

  • Lower extremity: 10

  • Upper extremity: 8, including 7 finger and 1 arm

  • Head and neck: 4, including 2 nose and 2 lip

• Muscle flaps with skin grafts and pedicled flaps were excluded.

• Debulking was performed at least 3 months after the index reconstruction, at a median of 10 months (range, 3 to 39 months).

• Incisions were designed along anatomic subunit borders. Redundant skin and underlying fat were excised in a cone-shaped fashion, with additional direct defatting as needed.

• The pedicle was not actively sought or preserved during revision.

• Primary outcomes were wound dehiscence, delayed healing, seroma, hematoma, infection, and reoperation.

• No power calculation or comparative statistical analysis was reported.

Results

• Zero patients developed wound dehiscence, delayed healing, seroma, hematoma, infection, or required reoperation.

• Median time to total suture removal was 14 days (range, 7 to 23 days).

• Most cases were treated through a single intraflap incision.

• 6/22 patients required more than one debulking procedure, using separate incisions along different subunit boundaries.

• All patients reported satisfaction with the aesthetic result, although no validated patient-reported outcome instrument was used.

• In the facial examples, debulking along natural boundaries such as the nasolabial fold restored contour while positioning the final scar within an existing anatomic transition.

Conclusion

The authors conclude that subunit-based intraflap debulking performed more than 3 months after free flap reconstruction may be a safe and effective secondary contouring option in selected patients. The approach provides direct access to central bulk while helping restore natural anatomic boundaries.

Strengths

• Simple, technically intuitive solution to the difficult problem of central flap bulk.

• Uses the revision scar constructively by placing it along a natural anatomic boundary.

• Complete absence of wound-healing complications is reassuring regarding the principal safety concern.

Limitations

• Small, retrospective, uncontrolled, single-surgeon series.

• No objective contour measurements, blinded aesthetic assessment, or validated satisfaction instrument.

• Outcomes were not analyzed by anatomic region.

• Only one patient had radiotherapy at the flap site, so the effect of radiation on healing and contouring outcomes could not be meaningfully assessed.

Clinical relevance

The practical value of this technique is that it allows the surgeon to address central bulk directly while placing the resulting scar where a natural boundary should exist. This is especially attractive in reconstruction of areas where contour transitions matter as much as thickness, including the nose, lip, hand, foot, and ankle.

Editorial notes

This is a clever and interesting technical paper. The most important contribution is not simply another way to remove fat from a flap, but a different way of thinking about secondary contouring: use the anatomic subunit boundary as both the access point and the final scar.

The series supports that this can be done safely in mature free flaps, even without deliberately identifying or preserving the original pedicle. What it does not establish is whether 3 months is the optimal timing, whether vascular independence from the pedicle can be assumed in every flap, or whether this approach is superior to margin-based debulking or liposuction. Given the potential consequence of flap ischemia, even a very low incidence of perfusion-complications could be enough to discourage widespread adoption. A 22-patient series with no complications is reassuring, but it cannot define that risk.

The facial examples are particularly instructive because they demonstrate the broader reconstructive principle. Good secondary contouring is not simply about making a flap thinner. It is about restoring the normal creases, transitions, convexities, and boundaries that define the reconstructed region.