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Introduction
CHAPTER 20 Principles of Flap
Dynamics
Cassandra J. Simonetta Jennifer A. Fehlman Ian A. Maher
SUMMARY
Understanding flap dynamics is a prerequisite for the performance of any flap
procedures.
Pivotal, deep, and horizontal restraints all have an important impact on flap
design and execution.
Accounting for fundamental tissue principles and flap dynamics prior to flap
execution permits more successful and cosmetically appealing reconstructive outcomes.
Beginner Tips
Understanding flap dynamics is predicated on an appreciation of the forces that oppose
tissue movement.
Undermining mitigates most deep restraint, while horizontal restraint is addressed by
using a sufficiently lengthy incision that recruits lax skin.
Expert Tips
Horizontal, deep, and pivotal restraints must all be addressed for optimal flap
outcomes.
Obstructive restraint can be addressed prior to flap movement.
On the face, the robust blood supply means that even random pattern flaps may behave
more like axial flaps in terms of viability.
Donโt Forget!
Undermining beyond 1 to 2 cm from the incision line may be counterproductive and
lead to an increased risk of tissue ischemia.
Flap length:width ratios should ideally not be significantly greater than 3:1, at least
when working in poorly perfused areas such as the legs. On the face, where most dermatologic surgery flaps are performed, there is often a forgiving and robust blood supply.
Pitfalls and Cautions
Failing to account for pivotal restraint is one of the most common flap design
challenges. Appropriately oversizing rotation flaps and widely undermining the pivot point may go a long way to mitigating this problem.
Once relocated to the primary defect, flaps should be under minimal tension.
Patient Education Points
Patients should be warned prior to flap closure that they will have an incision
stretching well beyond the initially visible defect.
Explaining that the additional scar length will likely heal with a minimally visible line
may go a long way toward patient reassurance.
Billing Pearls
Flap repair codes (140XX series) include the excision component, so it is not
appropriate to bill both an excision and a flap repair code simultaneously.
Mohs codes may be submitted along with flap repair codes, though they may be subject
to the multiple procedure reduction rule.
When coding a flap, medical necessity is the ultimate arbiter of appropriateness.
CHAPTER 20 Principles of Flap