> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/education/snomed-ct-education-editorial-guide/readme/authoring/domain-specific-modeling/substance/substance-naming-and-modeling-conventions/guidelines-for-specific-substance-types/flap-substances.md).

# Flap substances

<mark style="color:$danger;">**This Editorial Guide is used for Education Purposes Only. It is used in the Authoring Courses and Certifications. It is based on the January 2026 Editorial Guide.**</mark>

## Overview

This section includes concepts that represent flap substances used in flap surgery. The concepts in this subhierarchy are used to define:

Flap composition

* For example,
  * bone, skin, muscle, myocutanous, osteocutaneous

Flap blood supply

* For example,
  * Free flap: A completely detached flap transferred with its own blood supply intact is known as a free flap. A free flap is re-attached at the recipient site, which is a highly skilled technique, often involving microsurgical anastomosis of the blood vessels
  * Pedicle flap: A pedicle flap is transferred still attached to its original blood supply (the pedicle)

Flap substances exist for free flaps and pedicle flaps (<<261238005 |Free flap (substance)| and << 261235008 |Pedicle flap (substance)|) and reflect the fact that whether a flap is free or pedicle is also a function of its blood supply (i.e. completely unattached from its original blood supply, or still attached via a vascular pedicle).

## Modeling

<table data-header-hidden><thead><tr><th width="213.6953125"></th><th></th></tr></thead><tbody><tr><td><strong>Parent concept</strong></td><td>Most distal appropriate descendant of 256683004 |Flap (substance)|</td></tr><tr><td><strong>Semantic tag</strong></td><td>(substance)</td></tr><tr><td><strong>Definition status</strong></td><td>Primitive</td></tr></tbody></table>

Flap substances comprising composite multiple flap tissues are siblings (and not subtypes) of the various single tissue flap substances from which they are composed.

Flap substances should not include the procedure method, such as whether a flap is local or distant, or if a flap is rotated or advanced.

## Naming

The concepts in this subhierarchy must not be conflated with either the donor procedure site or the site that the procedure acts upon.

{% hint style="warning" %}
**Exceptions**

Flaps that include the named specific muscle site are to remain as a refinement in the flap substances; for example, 840353005 |Transverse rectus abdominis myocutaneous flap (substance)|.
{% endhint %}

For substances representing skin flaps, the FSN and PT contains ‘skin flap’ with an acceptable synonym of ‘cutaneous flap’.

For osteocutaneous flaps, terming for FSN and PT is ‘osteocutaneous flap’ with an acceptable synonym of ‘osseocutaneous flap’.

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