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 TITLE:   PRINCIPLES OF LOCAL SKIN FLAP RECONSTRUCTION
 SOURCE:  Dept. of Otolaryngology, UTMB, Grand Rounds
 DATE:    April 14, 1993
 RESIDENT PHYSICIAN:     Robert Hoffman, MD
 FACULTY:                Karen Calhoun, MD
 DATABASE ADMINISTRATOR: Melinda McCracken, M.S.
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 "This material was prepared by resident physicians in partial fulfillment
 of educational requirements established for the Postgraduate Training
 Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and
 was not intended for clinical use in its present form.  It was prepared
 for the purpose of stimulating group discussion in a conference setting.
 No warranties, either express or implied, are made with respect to its
 accuracy, completeness, or timeliness.  The material does not necessarily
 reflect the current or past opinions of members of the UTMB faculty and
 should not be used for purposes of diagnosis or treatment without
 consulting appropriate literature sources and informed professional
 opinion."
 
 
 Skin Flap Physiology:
 
    Anatomy - The skin consists of three basic layers: the epidermis,
 dermis and subcutaneous fatty layer.  The epidermis is composed of five
 distinct layers: stratum corneum, stratum lucidum, stratum granulosum,
 stratum spinosum, and stratum germinativum.  The dermis lies beneath the
 epidermis and contains primarily collagen fibers, elastic fibers and
 ground substance.
 
    Vascular supply to skin Segmental vessels originate from the
 embryologic aorta.  Characteristics include a perfusion pressure close to
 the aorta's, location deep to muscle and a common association with a nerve
 and vein.
 
   Perforator vessels are branches of segmental vessels and provide
 nutritional support to muscle.  Musculocutaneous arteries pass through the
 overlying muscle whereas direct cutaneous or septocutaneous arteries
 travel through fascia septa dividing muscle.
 
   The cutaneous portion of direct cutaneous arteries run parallel to skin
 surface providing nutrition to a large area of skin.  Direct cutaneous
 arteries are accompanied by a pair of veins and run superficially to
 muscular fascia.  Musculocutaneous arteries leave the muscle and directly
 penetrate the subcutaneous tissue to supply a smaller region of skin.
 Both direct cutaneous and musculocutaneous arteries empty into a diffuse,
 interconnecting vascular network called the dermal and subdermal plexi.
 This network provides a redundancy in the vascular supply to the skin with
 the formation of collaterals at the periphery.  Arterioles act as preshunt
 and precapillary sphincters which regulate the flow through the vascular
 network.
 
    Skin physiology - The rate of blood flow through the skin is the most
 variable in the body.  The two vascular patterns found in skin, the
 nutrient capillary network and arteriovenous shunts, are integral in
 performing the two functions of cutaneous circulation.  The distribution
 of cutaneous blood flow is regulated by precapillary and pre- shunt
 sphincters.  The precapillary sphincter responds to local hypoxemia and
 increased metabolic by products.  Under these conditions the sphincters
 open increasing the amount of nutritive blood flow.  The preshunt
 sphincters regulate the changes in blood flow that affect thermoregulation
 and systemic blood pressure.  Release of norepinephrine by sympathetic
 fibers closes these sphincters diverting blood away from the skin and
 preserving heat.
 
 Physiology of acutely raised flaps - A number of changes detrimental to
 skin survival occur when a local flap is raised.  The changes are due to
 vascular changes, nerve section and free radical formation.
 
   Vascular - The most obvious change that occurs when a flap is raised is
 the partial interruption of the vascular supply.  This results in a
 decreased local perfusion pressure.  The further from the base of the flap
 the more pronounced the decrease in pressure.  Low pressure blood supply
 via the subdermal plexus can be enough to maintain nutritional
 requirements.  Nutritional blood flow ceases and flap necrosis occurs when
 the perfusion pressure drops below the critical closing pressure of the
 arterioles in the subdermal plexus.  In surviving flaps the reduced blood
 flow gradually increases.  Neovascularization of the flap begins 3 to 7
 days after flap transposition.  In the presence of an angiogenic stimulus
 (ischemia) new capillaries arise from small venules in the recipient site
 and migrate toward the stimulus.  Some capillaries join preexisting flap
 vessels (inosculation), but the majority of revascularization appears to
 involve direct ingrowth of recipient vessels into the flap.  Venous
 outflow is also impaired after flap elevation.  Complete venous occlusion
 in the early postelevation period is more damaging to flap survival than
 inadequate arterial supply.
 
   Nerve section - Both cutaneous and sympathetic nerves are severed in the
 process of flap elevation.  When a sympathetic nerve is divided,
 catecholamines are released from the nerve terminal and the mechanism for
 catecholamine re-uptake is eliminated.  This local hyperadrenergic state
 produces vasoconstriction and decreases total flap blood flow.  It takes
 24 to 48 hours for the catecholamines to be depleted.
 Inflammation/prostaglandins - The surgical trauma associated with an
 acutely raised flap results in an inflammatory response.  Inflammation
 consists of a vascular and cellular response to injury that prepares the
 tissue for the repair process.  With injury, histamine, serotonin, and
 kinins are released into the extracellular compartment, markedly
 increasing the permeability of the capillaries.  Following the primary
 inflammatory response, synthesis of prostaglandins increases.  Through the
 cyclooxygenase pathway, multiple prostaglandins are formed.  Those
 prostaglandins with beneficiary vasodilating and inhibitory platelet
 effects include: PGI2, PGE2, and PGD2.  Those that cause vasoconstriction
 and platelet aggregation include Thromboxanes: A2, and B2.
 
   Free radicals - Return of blood flow to an ischemic flap occurs in about
 12 hours.  When oxygen becomes available with reperfusion, free radicals
 are produced that can cause damage at both the cellular and subcellular
 levels, contributing to post-ischemic tissue necrosis.  The major source
 of free radicals is xanthine oxidase.  This enzyme catalyses the formation
 of uric acid forming the superoxide anion radical (O2-).  This radical can
 cause tissue damage from lipid peroxidation of the cellular membrane and
 denaturation of the intracellular matrix.
       
 Classification of Flaps:
 
    Random cutaneous flaps - The blood supply is derived from the
 musculocutaneous arteries near the base of the flap.  Blood is delivered
 to the tip of the flap via the interconnecting subdermal plexus in the
 pedicle.
 
    Arterial cutaneous flaps - This flap takes advantage of a direct
 cutaneous artery within its longitudinal axis.  Examples include the
 deltopectoral flap (based on anterior perforators of the internal mammary
 arteries) and the midline forehead flap (based on the supratrochlear
 arteries).
 
    Myocutaneous flaps - These are based on distal segmental vessels
 leaving the local vasculature intact.  Examples include the pectoralis
 myocutaneous flap based on the pectoral branch of the thoracoacromial
 artery.
 
 General Principles of Wound Closure:
 
  Skin Biomechanics:
 
    The mechanical behavior of skin is primarily related to its collagen
 and elastin content.  Extension of skin is a mechanical property that is
 time dependent.  Continuing tension produces ongoing lengthening to a
 point.  As skin is stretched, there is an initial easy deformation.  As
 tension increases, the randomly arranged collagen fibers begin to lengthen
 in the direction of the force and deformation becomes more difficult.  At
 some point, the skin will not stretch no matter how much the tension
 increases.  It is at this point where the circulation is compromised and
 blanching and eventual flap necrosis occurs.  An animal study exemplified
 this by showing that any flap with a length:width ratio of greater than
 3:1 died.  Every flap with a ratio of less than 1:1 survived.  Flaps of
 intermediate length that were closed with less than 250 gm of tension
 survived.  Those closed with greater tension died.
  
  Stress Relaxation and Creep:
 
   These are the two viscoelastic properties of skin.  If a constant
 loading or stretching force is applied to skin it will exhibit stress
 relaxation or creep.  Stress relaxation occurs when a constant load
 applied to skin causes it to stretch.  With time, the load required to
 maintain the skin in its stretched position decreases.  Creep occurs when
 a sudden load applied to skin is kept constant.  The amount of extension
 increases with time.  These are important for flap closure and the basis
 for tissue expansion.
 
  Facial Lines:
 
   An important consideration in facial reconstruction is the concept of
 relaxed skin tension lines (RSTL).  The dominant force in the creation of
 these lines is the contractile action of the underlying facial muscles.
 Therefore, these lines lie perpendicular to the longitudinal axis of the
 facial muscle fibers.  This axis correlates with the lines of maximal
 extensibility.  Secondary forces which contribute to the RSTLs include the
 pull of gravity, the orientation of collagen bundles, and the underlying
 bony contour.  Closure of wounds along the RSTLs allows for closure with
 the least tension and fine scars that are easily camouflaged.
 
 General Principles:
 
   The initial issue to address in choosing a reconstructive approach is
 not which flap to use, but whether a flap repair should be considered at
 all.  It is helpful to decide initially whether a flap has any benefits as
 compared with a fusiform side to side closure.  The advantage of the
 latter is simplicity.  The aesthetic result is a straight or curved line
 and the risk of complications (ischemia, contour difficulties) is minimal.
 Therefore, for each flap considered, there is a need to establish specific
 indications and advantages over primary lenticular closure.  In making the
 decision, two criteria must be evaluated: 1) whether there is sufficient
 laxity to close the wound in a fusiform side to side fashion without
 either excessive tension or anatomic distortion and 2) whether cosmetic
 units, boundaries, and relaxed skin tension lines are respected by the
 incision line of fusiform closure or violated?  If closure tension,
 structural distortion or unsightly scars are anticipated from a fusiform
 closure, a flap should be considered as one of the alternative
 reconstructive options.
 
   In cutting a flap, the thickness of that portion of the flap that will
 fill the wound should be appropriate to the depth of the defect.  The
 minimal requirement is the inclusion of a thin layer of subdermal fat so
 that the subdermal plexus is included in the vascular network.  If the
 flap is make too thick, debulking will probably be necessary later.  The
 pedicle may, however, have a thicker base to include larger caliber
 vessels.  It is important to undermine beneath and around the flap as well
 as around the defect.  As a general rule, undermining should be carried
 out 1 - 2 cm beyond the wound edge.  This helps reduce the size of the
 defect, helps to distribute the tension at the would closure and allows
 the skin to give and stretch.
 
 Planning Surgical Approaches:
 
   The face can be broken down into various aesthetical anatomic units.
 Reconstruction should attempt to replace an entire unit or subunit.  If a
 defect involves more than one area, each one may be repaired separately
 using a different flap or graft.  It is important to attempt a match in
 color, texture and thickness and to respect the relaxed skin tension lines
 in closure.
 
   Forehead - This area is made of relatively thick skin and tight
 underlying musculature, frontalis contraction leads to prominent
 horizontal skin lines.  Procerus and corrugator contraction causes
 vertically oriented creases in the glabella and brow areas.  Tissue
 expansion plays a role in closure of large defects.  Important landmarks
 that should be preserved include the anterior hair line and brow position.
 Vertical incisions are best made in the midline.
 
   Brow - When hair-bearing brow is lost the defect is quite deforming.  It
 is important to replace hair and restore brow position.  This can be done
 with free punch or strip grafts of hair bearing scalp.  These should be
 implanted parallel with the remaining brow hairs.  Never shave the
 eyebrows.
 
   Eyelid - The eyelid may be divided in anterior and posterior divisions.
 The anterior division consists of the skin and orbicularis oculi muscles.
 The posterior division is make up of the tarsal plate and conjunctiva.
 The skin of the upper and lower lids is extremely thin lacks subcutaneous
 fat, and is tightly bound to the underlying muscle.  The eyelids must be
 mobile and firm.  The lower lid is supported medially and laterally by the
 canthal tendons.  Large lower lid defects of the anterior aspect can be
 repaired with a cheek rotation flap provided good support can be provided.
 This support must be preserved during reconstruction to prevent ectropion.
 The lacrimal drainage system must also be protected or alternative
 created.  Defects of the medial canthal region can be allowed to heal by
 secondary intention or by full thickness skin graft.  Full-thickness
 defects of up to one third of the width of the lid can be repaired with
 primary layered closure only.  Full- thickness skin grafts from the other
 eyelids are by far the best reconstructive option for superficial eyelid
 defects.
 
   Cheek - Reconstruction of the region defined by the zygomatic arch to
 mandibular margin and preauricular crease to melolabial fold contains many
 options and much flexibility.  The cheek skin is intermediate in thickness
 and varies considerably in different locations on the face.  It is
 thinnest in the preauricular area and thickest at the melolabial folds.
 This skin quite elastic and malleable and provides great flexibility in
 flap design.  Skin grafts are rarely used in this region because of the
 poor cosmetic results.  The RSTLs are particularly important and helpful
 in the selection and design of local flaps are the most commonly used
 flaps.  In general, rotation or transposition flaps are the most commonly
 used methods of local flap closure.  Large cervicofacial flaps can provide
 tremendous amounts of tissue for reconstruction.
 
   Nose - The nose is the central focal point of the face, and as such, any
 deformity here is devastating to the patient.  The nose represents a
 particular challenge to the reconstructive surgeon.  Frequently,
 structural framework has been lost along with the overlying soft tissue.
 The aesthetic subunit principle is especially relevant to nasal
 reconstruction.  Small defects near the nasal tip or dorsum may lend
 themselves to repair with full-thickness skin grafts, especially those
 from the melolabial fold, or with perichondrial cutaneous grafts from the
 auricle.  Alar and columellar defects may be repaired with composite
 grafts taken from the auricle.  Alar defects may be repaired with
 superiorly based melolabial flaps, and a variety of rotation and
 advancement flaps may be used for defects of the nasal dorsum.  The
 "workhorse" of nasal reconstruction is the midline forehead flap.  This
 flap is useful for a wide array of nasal defects including the total loss
 of nasal soft tissue.  The structural framework of the nose can be
 constructed using cartilage (septal or conchal) or bone grafts (calvarial
 or iliac spine), although both have some limitations.  The nose also lends
 itself well to prosthetic replacement in those patients who do not desire
 reconstruction.
 
   Lip and perioral area - The lips are important from both an aesthetic
 and functional standpoint.  Free mobility, muscle function, and intact
 sensation are important for the mouth to remain functional and competent.
 This is an area in which mucosal (vermillion) and cutaneous surfaces
 adjoin.  Each of these tissues should be reconstructed separately as
 needed, because the reconstructive demands of each are very different.  In
 addition, the reconstructive options for the two surfaces are quite
 distinct.  The vermillion can be replaced with advancement flaps or grafts
 of oral mucosa and on occasion with tongue flaps.  A defect or
 misalignment of the vermillion- cutaneous junction is quite visible.
 Therefore every attempt should be made to carefully reconstitute this
 important relationship with exacting symmetry.  The philtrum with its
 ridges and furrows is a very important landmark to preserve or
 reconstruct.  The skin of the lips is moderately thick and tightly
 attached to the underlying orbicularis oris muscle.  Since there is very
 little tissue resistance to the spread of malignancy in this area, many
 cutaneous tumors invade the muscle early in their growth.  therefore most
 excisional defects include both skin and muscle.
 
   As much as one third of the width of the lower lip (as measured before
 excision) can be repaired with only a primary, layered closure.  Larger
 defects (up to two thirds of the width) can usually be repaired with a
 cross-lip flap (for example, Abbe flap) or an Estlander flap where the
 lateral commissure is involved.  Subtotal or total loss of the lip usually
 requires a flap such as the Karapandzic flap or more extensive cheek
 flaps.  Skin grafts are of little value in the perioral area.  Y-V and V-Y
 advancement flaps or Z-plasty interposition flaps are often useful in
 correcting small residual deformities around the philtrum and the nasal
 columella.  When the vermillion border is perfectly aligned, it provides
 an excellent line in which to place and camouflage incisions.  The
 alalabial crease provides an excellent camouflage as well, as do the
 multiple vertical RSTLs of the lips.  Occasionally, large regional
 myocutaneous flaps are required for extensive defects.
 
   Chin - Reconstruction of defects in the chin region is made difficult by
 the great thickness of subcutaneous tissue that is frequently lost or
 injured.  The projection of the underlying bone can easily be modified
 with either implants or with genioplasty techniques.  If possible, one
 should avoid crossing the prominent sublabial crease with incisions or
 flaps because this leads to webbing across the concavity.  The multiple
 circumferential RSTLs around the chin are helpful in planning incision
 placement.  The best results are usually obtained with adjacent tissue
 flaps, particularly of the rotational type.  Flaps of adjacent neck skin
 should be avoided whenever possible.
 
 Skin Grafts:
 
   Split thickness skin grafts - These are used almost solely to cover
 large defects or those where there is concern about tumor recurrence.  The
 graft usually gives poor color match and cosmetically inferior.
 
   Full thickness skin grafts - These play a role in reconstruction because
 they offer good color and thickness match in some areas.  The skin of the
 face varies considerably in thickness in various areas, so ideally, the
 thickness of the skin graft should be chosen to match the thickness of the
 skin defect as closely as possible.  There are several good donor sites
 for FTSGs.  These include the supraclavicular region, melolabial fold,
 pre- and postauricular skin and upper eyelid skin taken during
 blepharoplasty.  Three facial areas are particularly open to these grafts:
 1) tip of the nose with skin from the post auricular area or posterior
 skin of the ear lobule. 2) the lateral surface of the auricle and 3) the
 eyelids.  Eyelid skin should be replaced with eyelid skin whenever
 possible.
 
 Advancement Flaps This method of tissue movement involves sliding tissue
 forward for defect closure or augmentation.  The advancement flap provides
 the advantage of altering the position and location of a portion of the
 scar that might result from fusiform closure.  Closure of a circular
 defect leads to Burow's triangles or standing cones.  A rectangular
 advancement flap allows displacement of the scars of the standing cone
 correction to a site distant from the original defect.  The longer the
 flap, the greater the distance the standing cone correction scar can be
 moved from the defect.  If the flap is long enough, it may allow for
 primary closure.  Thus, the primary indication for an advancement flap is
 to alter scar location.  The flap should be planned such that the scar
 crosses as few cosmetic subunits as possible.  This flap does not alter
 the closure tension generated by a comparable fusiform closure.  It should
 therefore not be used if excessive tension is anticipated or structural
 distortion occurs secondary to the tension.
 
   There are several variations in advance flap design.  The common factor
 of these flaps is the location management of the standing cones.  The
 simplest type of movement is the V-Y advancement.  The skin is lifted as a
 V, moved forward, with direct closure of the posterior defect.  The Y-V
 flap shortens a defect along the long axis of the flap while expanding
 tissue laterally.  The classic rectangle advancement flap displaces both
 standing cones away from the wound.  An A to T closure allows the standing
 cones to be displaced medially and laterally.  A bilateral rectangle
 displaces the standing cones to the four corners of the flap.
 
   The rectangular advancement flap works well for defects involving the
 eyebrow and forehead.  Closure lines can often be placed in preexisting
 creases or along cosmetic boundaries.  This is useful in closure of the
 medial cheek and lateral side wall of the nose.  In the midface area they
 should be designed to conform to natural contours, furrows and lines in
 that particular area.  Closure lines are well hidden at the nose- cheek
 junction and the melolabial crease.
 
 Rotation Flaps Rotation flaps are semicircular flaps that rotate skin
 around a pivot point into a triangular defect.  Typically, the diameter of
 the flap should be at least twice the width of the defect.  By
 manipulating the design of the rotation flap, a defect is transformed in
 shape and location.  This changes both the direction and magnitude of
 wound closure tension.  A rotation flap should be considered when fusiform
 closure or modifications of an advancement flap would create excessive
 wound closure tension or distortion of local anatomic landmarks.  The flap
 is designed by triangulation the defect making the shortest side the base
 of a triangle.  The base then forms a portion of the circumference of a
 circle and the flap is constructed so that its leading tip will rotate
 around the circumference of the circle on which the triangular defect
 lies.  In situations where sufficient flap rotation is not possible, a
 back cut is necessary.  With a back cut, an incision is made toward the
 center of the circle to allow for further rotation.  Extension of a flap
 beyond 90 degrees does not give any mechanical advantage in closure.  It
 may however, be beneficial in tissue draping prior to closure.  The flap
 should be designed to conform to facial anatomic lesions.  The melolabial
 fold, preauricular crease and subciliary lines can all function as the
 outer circumference incisions.  A disadvantage of this flap is that the
 scars may appear excessive relative to the size of the original defect.
 
   An extension of the rotation flap is the cervicofacial rotation flap.
 This flap is useful when there extensive tissue defects in the cheek,
 lower eyelid, or buccal area.  An incision along the melolabial fold
 functions as a back cut that facilitates flap rotation and advancement.
 The superolateral edge of the flap should curve above the lateral canthus
 to allow for good support of the lower lid and help to prevent the
 development of an ectropion.  The incisions follows the preauricular
 crease down to and around the lobule.  At this point, two options or
 available to provide additional tissue for reconstruction.  One utilizes a
 flap of postauricular skin as a bilobed flap.  Alternatively, the incision
 can course down into the neck following a gentle curve with a natural
 crease.  Care should be taken not to injure the facial nerve during
 elevation of the flap.
 
    Defects of the nasal tip are repaired well by an appropriately designed
 rotation or dorsal nasal flap.  Incisional lines reside at the nasofacial
 junction, leaving the interior of the aesthetic subunit of the nose
 reasonably well unviolated.  A back cut usually needed in the glabella
 region for closure.  Lateral upper lip wounds may also be closed with a
 rotation flap using the melolabial crease.  Other areas where this may be
 used include the upper forehead and the cheek.
 
    Transposition Flaps:
 
   These flaps are transposed into a defect with primary closure of the
 donor site.  A transposition flap allows one to tap into skin laxity
 distant from the site of the defect.  Unlike a rotation flap, the laxity
 may be quite distant from the primary wound and the size of the flap need
 not be unreasonably large.  If designed appropriately, the closure of the
 primary site may be nearly tension free.  Although termed a transposition
 flap because the flap transposes or jumps over tissue intervening between
 the donor site and the defect, the motion is really rotation.  The flap
 swings around a fixed pivot point at the flap pedicle.  Because of design
 differences, transposition pedicles are narrower than the broad bases of
 rotation flaps and move in a freer fashion.  These flaps can change
 tension vectors in a way similar to rotation flaps.  However, they are
 usually smaller and are less restrained in their movement.  On the other
 hand, transposition flaps, because of the geometric design, create more
 unusual scars that are more difficult to hide within cosmetic junctions.
 Examples include:
 
   Rhombic Flaps - This transposition flap has many applications in the
 reconstruction of the head and neck.  This classic flap consists of a
 rhomboid defect with two 60 degree and two 120 degree angles.  The lesion
 is oriented such that the 120 degree angle is placed where the excess of
 skin lies.  The site of the donor defect should lie in the long axis of a
 line of minimal tension.  In designing the flap, a line bisecting the two
 120 degree angles is extended.  This line should be equal in length to the
 sides of the rhomboid.  From the outer point of this line, another line is
 drawn at 60 degrees parallel to the side of the rhomboid defect.  It's
 length again equals that of the side of the rhomboid.  After the initial
 rhomboid is drawn, there are four potential flaps from which to choose.
 Clearly, the flap which produces the least tension, has the best color and
 thickness match and does not alter local anatomic subunits is the donor
 site of choice.  Once closed, the site of major tension is at the donor
 site.  Long defects can be broken into two rhomboids and closed with two
 separate rhomboid flaps.  Large circular defects can be converted into a
 hexagon.  Rhomboid flaps can be planned on the 120 degree angles.  This
 provides a choice of six donor sites for closure
 
   Dufourmentel Flap - This flap is a modification of the rhomboid flap.
 It can be used for rhomboids that do not have the 60 and 120 degree
 angles.  Diagonals are drawn through the defect site.  On the wide angle,
 the short diagonal and one side are extended outward.  The angle formed by
 these is bisected by a line that equals a side length.  From the outer end
 of this line draw another line of equal length parallel to the long
 diagonal.  Closure is similar to rhomboid flap once the flaps are raised.
 
   Melolabial flaps - These are useful for defects of the lower nose and
 lips.  they may be inferiorly or superiorly based.  The flap is centered
 on the melolabial fold and has a good blood supply.  The blood supply in a
 melolabial flap is not actually based on a specific vessel found in the
 flap, but rather on a directionly oriented subdermal plexus that courses
 parallel to the melolabial crease, thus making it a random flap with a
 directional orientation to the blood flow.  After being elevated, the flap
 is transposed medially to reconstruct the alae or upper lip.  The flap may
 also be folded on itself either transversely or longitudinally to rebuild
 the alar margin.  Broad, superiorly based flaps can effectively
 reconstruct large defects of the upper lip.  The secondary deformity
 generally lies in a very favorable location along the melolabial crease or
 the nasofacial groove.  The primary difficulty with superiorly based flaps
 is their tendency to thicken as a result of lymphedema.
 
   Glabellar flap - These flaps are actually a combination of a rotation
 and transposition flap.  This flap takes advantage of the relatively
 abundant tissue in the glabellar area and is particularly useful for
 defects in the medial canthal region as well as the upper portion of the
 nasal dorsum.  It cannot however reach nasal tip or ala defects.
 
    Bilobed flaps - A bilobed flap is a combination of a rotation and a
 transposition flaps.  The bilobed flap consists of a primary lobe and a
 secondary lobe that share a common pedicle.  An advantage of the bilobed
 flap is that the pedicle is rotated only 90 degrees.  The primary lobe is
 roughly twenty percent smaller than the original defect and the secondary
 lobe is approximately one half the size of the original defect.  The angle
 between the flaps varies from 45 to 90 degrees.  This procedure
 distributes the tension of closure fairly equally around the defect.  The
 bilobed flap is useful when a transposition flap is indicated but the
 defect site for the primary flap cannot be easily closed.  They are also
 useful to close defects in areas where tissue must be borrowed from more
 than one direction to allow repair without distortion and when it is
 necessary to transpose tissue over an anatomical landmark such as an ear.
 Bilobed flaps are commonly used for small defects of the dorsum of the
 nose and for lateral cheek defects.  The major disadvantages of the flap
 are the length of the incisions, occasional dog ears, and the webbing that
 sometimes develops when the cheek-flap is used to resurface a nasal
 defect.
 
 Complications:
 
 Almost all complications of local flaps result from errors in judgement,
 planning, and execution.  Flap loss is a serious complication that almost
 always results from design or technical error.  Reasons for flap failure
 include: using a small flap to fill a big hole, hematoma, damaging the
 blood supply, making the flap extend outside its blood supply, suturing
 the wound under tension, failing to use a back cut, or making a pedicle
 too short.  Care must be taken to preserve the branches of the facial
 nerve especially the frontal and submandibular branches.
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                             BIBLIOGRAPHY
 
 Bailey BJ, Calhoun KH. Basic principles of plastic surgery in the head and
 neck. In Paparella MM, et al, editors: Otolaryngology, Philadelphia, 1991,
 W.B. Saunders Company.
 
 Dzubow LM. Flap dynamics. J Dermatol Surg Oncol; 1991;17:116-130.
 
 Goding GS. Skin flap physiology. In Cummings CS, et al, editors:
 Otolaryngology head and neck surgery, St Louis, 1993, Mosby-Year Book.
 
 Hoffmann JF, Cook TA. Reconstruction of facial defects. In Cummings CS, et
 al, editors: Otolaryngology head and neck surgery, St Louis, 1993,
 Mosby-Year Book.
 
 Jackson IT: Local flaps in head and neck reconstruction, St.  Louis, 1985,
 The CV Mosby Co.
 
 Larrabee WF. Design of local skin flaps. Facial plastic and reconstructive
 surgery. Instructional courses - American Academy of Otolaryngology - Head
 and Neck Surgery. Volume 3, 1990.
 
 Salasche SJ. Complications of flaps. J Dermatol Surg Oncol;
 1991;17:132-140.
 
 Shumrick DA, Savoury LW. Local Flaps. In Paparella MM, et al, editors:
 Otolaryngology, Philadelphia, 1991, W.B. Saunders Company.
 
 Younger RAL. The versatile melolabial flap. Otolaryngol Head Neck Surg
 1992;107:721-726.
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