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Fig. 2.5 Cheek subunits
2 Facial Units andSubunits
Nose
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Nose
The nose is a complex structure and lends itself to being divided into further subunits, separated by less discrete borders. It is typically divided into nine subunits;
columella, tip, dorsum and paired sidewalls, ala and nasal facets (Fig.2.6).
The complex three-dimensional shape is supported by a bony and cartilaginous
framework. The overlying skin is of varying thickness and mobility, and the deep
surface is lined by mucous membrane. The concept of “subunit” reconstruction was
initially popularised for the nose and often involves altering the size, shape and
depth of the defect to reconstruct a “full subunit” so that the scars lie in the most
advantageous positions and deceive the eye. There are exceptions to these guidelines and these, along with the other aspects will be discussed further in the chapter
on nasal reconstruction.
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Fig. 2.6 Nasal subunits
2 Facial Units andSubunits
Lips
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Lips
The upper and lower lips have prominent aesthetic and social connotations and form
a distinct facial aesthetic unit. The lip unit is dened by the base of the nose superiorly, nasolabial fold laterally and mentolabial fold inferiorly. The lip aesthetic unit
can be divided into the cutaneous upper lip, cutaneous lower lip and the vermillion
subunits. The upper lip can be further divided into a philtrum and two lateral subunits (Fig.2.7).
The lip is a composite structure made up of skin, muscle and mucosa. The muco-
cutaneous junction is dened by the vermillion border and represents a very important facial landmark. The RSTLs are oriented radially around the oral stoma and are
vertical in the central region and oblique in the lateral aspects.
Lip reconstruction needs to address both aesthetics and function. Satisfactory
function requires the presence of intact sensory and motor nerves and restoration of
the orbicularis oris muscle sphincter.
Ideally tissue mobilised from within the lip complex provides the best match.
Incisions should be placed parallel to the perioral rhytides for simple excisions. It is
extremely important not to distort the vermillion border, and its precise approximation is mandatory. Flaps mobilised from the adjacent areas should ideally have their
incisions along the aesthetic borders (base of nose, vermillion, nasolabial and mentolabial folds). Consideration should be given to modifying the defect, to place the
scar in the most advantageous position.
The specic reconstructive options will depend on a multitude of factors, includ-
ing the presence of full and partial thickness defects. These will be discussed in
greater detail in the session on lip reconstruction.
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Fig. 2.7 Lip subunits
2 Facial Units andSubunits
Chin
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Chin
The chin unit is dened by the mentolabial fold superiorly and laterally and the
lower border of the mandible inferiorly (Fig.2.8). The RSTLs are arranged in a
curvilinear pattern, and scars are ideally designed to lie parallel to these.
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Fig. 2.8 Chin subunits
2 Facial Units andSubunits
Pinna
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Pinna
The pinna is a structure made up of a complex three-dimensional cartilaginous
framework and draped by skin on the lateral and medial aspects. The goal of reconstruction is to try and preserve the shape, size and position of the pinna. Knowledge
of the different parts of the pinna is essential for reconstruction (Fig.2.9).
The pinna lies between horizontal lines drawn from the superior orbital rim and
the nasal spine. It protrudes from the scalp at an angle of 25°–35°.
The skin on the lateral surface is thin and densely adherent to the underlying
cartilage, whereas the posterior skin in thick and more mobile. The auricular cartilage is supple and can be easily deformed by wound tension and scar contracture.
Scars can be camouaged in the many undulations of the pinna. Local ap reconstruction often results in a decreased height of the pinna, but when the shape is
maintained, is surprisingly inconspicuous.
The specic aspects of ear reconstruction will be discussed in the session on ear
reconstruction.
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Tr
Anti-tragus
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iangular Fossa
Cymba concha
Tragus
Cavum concha
2 Facial Units andSubunits
Scapha
Helix
Anti-helix
Lobule
Fig. 2.9 Pinna—Landmarks
Eyelids
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Eyelids
Eyelids perform many important functions, which include protection of the eye and
maintaining an adequate tear lm. The aesthetic eyelid unit is dened by the lower
margin of the eyebrow, lateral and inferior orbital rims and the nasojugal fold. A
sound understanding of anatomy and function is essential for eyelid reconstruction
and should only be attempted by an appropriately trained clinician.
The eyelids are complex multi-layered structures supported by cartilaginous tar-
sal plates. The free lid margin contains eyelashes and secretory glands, and the
extension of the tarsal plates forms the medial and lateral canthal tendons.
Reconstruction could be more easily understood if the eyelids were considered
to consist of an anterior lamella composed of skin and orbicularis oculi and a pos-
terior lamella composed of conjunctiva, tarsal plate, orbital septum and the lid
retractors. The orbital septum is occasionally considered the middle lamella, and the
“grey line” along the lid margin represents the junction between the anterior and
posterior lamellae.
The eyelid aesthetic unit can be further subdivided from a reconstructive point of
view into upper lid, lower lid, medial canthus and lateral canthus subunits (Fig.2.10).
The skin of the eyelid is the thinnest in the body, and the RSTLs around the eye-
lids are horizontally oriented. However, excision parallel to the RSTLs, especially
in the lower lid, runs the risk of eyelid retraction and ectropion. It is therefore preferable to orient excisions to be perpendicular to the lid margins unless there is signicant skin redundancy. Excisions along the RSTL in the adjacent lateral and
medial canthus, eyebrow and glabella regions can be performed and will provide
relatively unobtrusive scars.
Full-thickness defects require reconstruction of both the anterior and posterior
lamella, in which case it is mandatory that at least one of the reconstructed lamella
should contain its own blood supply.
There are many factors to be considered before a decision is made to reconstruct
an eyelid defect and these will be described in more detail in the session on eyelid
reconstruction.
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