Principles of plastic surgery

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Definition

The term plastic surgery is derived from the Greek ‘to shape or mould’ and refers to that field of surgery which reconstructs defects caused by trauma, cancer removal, burns or disease processes. These deformities may be congenital or acquired, cosmetic or functional. The basis of reconstruction is the science and art of moving tissues, most commonly flaps of skin and subcutaneous tissue, from one site to another. This demands a knowledge of skin and muscle blood supply as well as the skill and experience to anticipate the behaviour of tissues subjected to these processes, especially their laxity, mobility and healing capacities.

History and development of plastic surgery

In approximately 600 bc the Hindu surgeon Shushruta described a technique for nose reconstruction using a long tongue of forehead skin based between the eyebrows that was twisted around to reach the nose tip. Rediscovered during the British occupation of India, it became known as the Indian rhinoplasty. The Italian method of rhinoplasty (Tagliacozzi, 16th century) involved a staged operation where a tube of skin and fat was lifted up from the medial surface of the upper arm and inset into the nasal defect. Development of techniques for reconstruction occurred rapidly from the 19th century onwards. Flaps to the face were described and split skin grafting and full-thickness skin grafts were developed. The need to repair war injuries led to the development of the tube pedicle. The groin flap with its axial vascularisation from a single artery and vein rather than the traditional random pattern was described and paved the way for long, narrow flaps with wide arcs of rotation, which could in many cases obviate the need for a tube pedicle. Microsurgeons who had perfected microvascular anastomosis of small vessels permitting replantation of amputated parts and toe transfers, investigated the microvascular transfer of flaps. The axial vessels feeding such flaps could be isolated, divided and re-anastomosed at the site of the defect. This form of flap transfer became known as a free flap and revolutionised plastic surgery. Musculocutaneous flaps such as the latissimus dorsi and the transverse rectus abdominis myocutaneous (TRAM) flaps were developed and have become the mainstay for breast reconstruction.

Wound healing

Effective wound healing is the basis of all surgery. When wounds do not heal the reason is generally obvious, and is usually associated with inadequate blood supply to the area. Haematoma, excessive tension, foreign body and irradiation all predispose to ischaemic necrosis and wound breakdown. This in turn leads to infection. Reducing infection by the recent innovation of vacuum applied to sponge dressings (vacuum-assisted wound healing) has been shown to dramatically speed healing of contaminated, chronic wounds, such as bed sores, by decreasing oedema, reducing bacterial count, debriding dead tissue and producing a moist environment for epithelialisation.

Recent research is directed towards maximising wound healing and minimising scar formation. Transforming growth factor-β (TGF-β) has been implicated in scar states, such as hypertrophic scar and Dupuytren's contracture. The absence of TGF-β in the early foetus may explain the relative reduction of scarring that occurs in foetal wounds. TGF-β blocking agents are now being developed to reduce adult scarring.

Principles of wound suture

The aim of suturing is to approximate wound edges meticulously in layers so that dead space is eliminated and minimal scar is required to bridge the gap. Damaged skin margins should be resected. Sutures should be placed vertically through the tissues to approximate the full depth of the wound and should be the least number and least calibre required to maintain closure. They should be close to the wound edge and be removed before cross-hatching marks can occur. Subcuticular sutures will avoid cross-hatching, but will not necessarily prevent stretching. More problems occur through removal of sutures too soon than leaving them too long. Elderly people scar less than the young, but are slower to heal, hence sutures should be left in longer. As a general rule, facial sutures should be removed at approximately 1 week and sutures elsewhere at 10 days. Where tissue is missing, suturing under tension may lead to suboptimal scarring, often inducing hypertrophic reaction that will resolve to a wide, stretched scar. Alternatively, tension may result in distortion of local anatomy, especially in the face, causing ectropion or asymmetry. Primary skin grafting or flap repair may obviate the problem, but these techniques create scars in their own right and ultimately it is experience and aesthetic sense that determines the correct procedure.

Placement of incisions

Incisions are used to excise skin lesions and to gain access to deeper structures. In either case their design should be directed towards minimising and disguising scars. Fine scars in or parallel to facial crease lines (Langer's lines), especially in older patients, may be almost imperceptible. Not only do they give the illusion of crease lines, but they remain narrow because they are transverse to the direction of the facial muscles and hence minimise the tension across the scar. Lesions such as naevi, birthmarks and skin cancers should be excised in an elliptical form with their axis in the direction of Langer's lines; that is, the line of least tension or maximum laxity. Although in the trunk and limb Langer's lines are more obscure, the same principle applies.

Incisions should not transgress cavities or flexion creases. Because all linear scars contract, an incision in such sites will heal with webbing and tenting of skin across the hollow and cause contracture or limitation of full extension across joints. Incisions should therefore curve around the concavity or be closed in a fashion that achieves lengthening or relaxation of the line. Such a technique is z-plasty.

The z-plasty closure

Z-plasty closure is most commonly employed to release scar contractures. Along the course of the incision back cuts are made on either side into the adjacent skin at 60° and parallel with each other. The length of the back cuts equals the length of the original incision so that a z-shaped incision now pertains (Z-plasty. (A) Design of z-plasty. Length of limbs AB = BC = CD, with BC representing the scar to be reoriented. Angles ABC = BCD = 60° in this design. The AD crosses the scar at 90° and outlines the new central axis of the ‘ez’ f following flap transposition. (B) Incisions and elevation of triangular flaps. A parallelogram-shaped defect is formed. (C) With release of the scar contracture, the tension within the skin lengthens the wound at the expense of width. (D) Flaps transpose automatically with release of scar. Scar is now re-oriented perpendicular to original position.A). The two triangular flaps so created are lifted and interdigitated with each other so that the incision line now forms a new z, with its central axis transverse to the original line of the incision (Z-plasty. (A) Design of z-plasty. Length of limbs AB = BC = CD, with BC representing the scar to be reoriented. Angles ABC = BCD = 60° in this design. The AD crosses the scar at 90° and outlines the new central axis of the ‘ez’ f following flap transposition. (B) Incisions and elevation of triangular flaps. A parallelogram-shaped defect is formed. (C) With release of the scar contracture, the tension within the skin lengthens the wound at the expense of width. (D) Flaps transpose automatically with release of scar. Scar is now re-oriented perpendicular to original position.B,D). When used to release contractures, excision of the longitudinal scar along the central line of the z causes immediate springing apart of the incision in a longitudinal direction (Z-plasty. (A) Design of z-plasty. Length of limbs AB = BC = CD, with BC representing the scar to be reoriented. Angles ABC = BCD = 60° in this design. The AD crosses the scar at 90° and outlines the new central axis of the ‘ez’ f following flap transposition. (B) Incisions and elevation of triangular flaps. A parallelogram-shaped defect is formed. (C) With release of the scar contracture, the tension within the skin lengthens the wound at the expense of width. (D) Flaps transpose automatically with release of scar. Scar is now re-oriented perpendicular to original position.C). This causes the elevated flaps to automatically transpose into each other's defect, as the axis of the parallelogram lengthens from a transverse to a vertical one. This manoeuvre effectively imports lax tissue laterally into the longitudinal axis and obviously can only work if there is lateral tissue available. Z-plasties not only lengthen scars but also redirect them. This has an important application in camouflaging long scars, especially in the face.

Z-plasty. (A) Design of z-plasty. Length of limbs AB = BC = CD, with BC representing the scar to be reoriented. Angles ABC = BCD = 60° in this design. The AD crosses the scar at 90° and outlines the new central axis of the ‘ez’ f following flap transposition. (B) Incisions and elevation of triangular flaps. A parallelogram-shaped defect is formed. (C) With release of the scar contracture, the tension within the skin lengthens the wound at the expense of width. (D) Flaps transpose automatically with release of scar. Scar is now re-oriented perpendicular to original position.

Scars including hypertrophic scars (keloid)

Scars are the trademark of the surgeon. Scars can be minimised but not eliminated. Whenever the skin is breached to the level of the deep dermis there will be a scar forever. The site of the scar determines its nature, rather than how it was created or who repairs it. The eyelid skin may almost leave invisible scars, but rarely elsewhere. The prepectoral region is the worst area in the body for scarring, producing a predictable hypertrophic response commonly seen following midsternal splitting for cardiac surgery. The scar becomes red, raised, hard and welted, and patients complain of intense itch and tearing. The scar base widens and over the course of a year or so gradually softens, flattens, becomes paler and symptom-free, but the patient is left with a permanent, wide, welted scar. This is largely incurable, in that attempts to excise it only reproduce the circumstances that led to its formation in the first place.

The proper management is to await nature's resolution. Time is a scar's best friend and revisional surgery should be postponed, generally for 6–12 months to assess nature's final result. Silicone gel pressure pads or judicious use of cortisone injection may hasten what nature will eventually do. Cortisone injection is best reserved for symptomatic scars as it risks worsening the cosmetic result by excessive thinning of the scar tissue, leading to transparent, wide, concave scars often with telangiectasia. Scars elsewhere in the body are relatively predictable. The face generally heals with fine scars; neck and ears less so. Ear lobe piercing not uncommonly results in hard, keloid-like lumps often misdiagnosed as cysts. The shoulders and deltoid region, upper back and knees are also notorious for hypertrophic reaction and stretching. The middle and lower back always leave depressingly wide, stretched scars but they are rarely hypertrophic. The upper abdomen frequently passes through a reactive, thickened phase eventually settling to a wide, flat scar; the lower abdomen much less so. Transverse abdominal scars are better than vertical ones. Limb scars are intermediate in their reaction to injury, while hand and foot scars are generally fine. Scars on the sole however can present a unique problem owing to intense hyperkeratotic reaction that can be intractable. This is presumed to be a function of pressure and tension.

Revisional surgery cannot make scars invisible nor can any other technique. All surgery is designed to camouflage the scar so that it is mistaken for a natural line. Theoretically, long scars can be broken up by multiple shorter scars, partly directed into the crease lines by z-plasty (see above). This is particularly useful if the scar crosses natural crease lines. Pigmented, lumpy or wide scars can be excised and sutured to be flatter and narrower, but as stated previously the outcome is related to the site and nature of the skin. Multiple patches of scar can be excised as one and closed in a linear fashion. Stepped, indented and pin-cushion scars can be excised and closed with multiple z-plasties to restore smooth contour. Redness of a scar is worsened by surgery. Time will fade scars, but occasionally laser may speed the process of capillary obliteration.

Tissue transfer

Tissue transfer generally involves skin grafts and flaps to cover a skin defect.

Grafts

A graft is a piece of tissue that is totally detached from the body and after reapplication comes back to life. Its survival depends on revascularisation from its bed. Avascular beds (e.g. bare tendon, bone, ligament, irradiated tissue, ischaemic ulcers) will prevent graft take. Fluid collection between the graft and its bed, such as haematoma, seroma or pus, will prevent revascularisation and traditionally a pressure dressing is applied to the graft to maximise adhesion to the bed. Grafts survive the first few hours by plasmatic imbibition; that is, diffusion of nutrients from the bed. Within hours inosculation occurs, where the transected capillary ends in the graft physically link with those in the bed to achieve end-to-end vascular connections. Blood flow through these is seen by 24 hours. True angiogenesis follows with the establishment of a new vascular pattern and blood flow within the graft.

Classification of grafts

SPLIT SKIN GRAFTS

A split skin graft is shaved with a knife at a dermal level that includes elements of the epidermis and dermis proportional to its thickness. The split skin graft donor site heals spontaneously because dermal elements remain and permit regeneration. The graft quality depends on its thickness, but hair and sweat gland function is not usually transferred. Sensation returns to the graft by ingrowth from its bed. Split skin grafts are indicated where large areas of skin are required, such as burns or degloving injuries or where the graft bed has relatively poor vascularisation, and a thin graft has the best potential for survival. There are several deficiencies of split skin grafts, including graft contracture, poor contour and colour match, and problems with donor site healing. Split skin grafts can be meshed; that is, multiple perforations applied by passing it through a special roller. This allows expansion of the graft for a greater area of cover. Also the perforations permit fluid through the graft to prevent separation from its bed.

FULL-THICKNESS GRAFTS

Full-thickness grafts include all layers of the skin down to the level of the dermal fat. No skin element remains in the bed and therefore the donor defect must be closed. This usually limits the permissible size and sites to regions where there is sufficient loose skin to allow direct suture closure, for example, the groin crease, wrist crease and postauricular region. Full-thickness grafts contract little and retain their colour and texture so that the site can be selected to match the defect. Grafts from behind the ear are particularly valuable in the face for eyelid and nasal bridge reconstruction. Full-thickness grafts revascularise by the same process as split skin grafts.

MUCOSA

Buccal cheek, septal, tongue, vermilion and vaginal tissue can be used as full-thickness grafts for specific reconstruction.

CARTILAGE

Cartilage is normally avascular and survives by diffusion of nutrients. When grafted it generally retains its shape and volume, but is inert. Its surface becomes incorporated into surrounding tissues by vascular ingrowth. It is used for nasal and ear reconstructions and the usual sources include rib, concha and septum.

BONE

Bone grafts act as a scaffold for ingrowth of new bone from the adjacent intact bone bed. Cancellous grafts include stem cells and growth factors, especially bone morphogenic proteins that stimulate osteoblasts. Cortical bone adds strength and stability until living replacement is complete. In long bones, compressive forces then mould the bone stress lines according to Wolf's law, so that strength is restored. Sources of cancellous bone include iliac crest and lower radius; cortical bone grafts are usually fibula or cranial bone.

TENDON

Tendon is essentially avascular and survives grafting almost in toto. Finger flexor tendon grafts within their flexor sheath are nourished by synovial diffusion. Blood supply, initially at least, is confined to the repair sites proximally and distally, where capillary ingrowth is accompanied by scar adhesions. Gradually an intrinsic blood supply probably develops within the core of tendon.

NERVE

When a nerve is grafted, the axons are resorbed (Wallerian degeneration) but the Schwann cells, which are the key to axonal regeneration, survive along with the perineurial and endoneurial tubes. The Schwann cell changes phenotype initially to a macrophage-like scavenger cell and then converts to a myelin-producing cell once new axon sprouts appear in the graft. When myelination is complete the Schwann cell reverts to its stable supportive role. Thick nerve grafts, such as nerve trunks, undergo central necrosis when grafted because of insufficient revascularisation. Thin grafts only are clinically useful; for example, sural or medial cutaneous nerve of the forearm. These can be cut into multiple segments and laid side by side to match the volume of larger nerves. They are then known as cable grafts and have been shown to be revascularised within 4 days.

COMPOSITE GRAFTS

Any combination of structures can theoretically be grafted, but the thicker the graft the less likely the vascular bed will be able to penetrate it before necrosisoccurs. The most common and most valuable composite grafts include skin and cartilage from the ear for nasal rim repair, and mucosa and cartilage from the nasal septum for eyelid reconstruction.

Flaps

A flap is a piece of tissue, usually skin and subcutaneous fat, which is transferred from one site to another but at all times retains its own blood supply. Unlike a graft it is independent of the vasculature of its bed and it is often indicated for reasons of poor vasculature where skin grafts will not take, for example, over bare tendon or bone, irradiated tissue or chronic scars. Other merits of flaps over grafts, especially in the face, include their close approximation to the qualities of the defect in terms of colour, texture and, particularly, thickness and contour. Cosmetically, therefore, flaps are generally superior to grafts, except for eyelid, inner canthal and nasal bridge defects where full-thickness grafts from behind the ear are ideal. Successful flap transfer is based on a knowledge of skin, blood supply in the various parts of the body and an understanding of the intrinsic properties of the skin with respect to mobility, elasticity and healing potential.

Classification of flaps

ACCORDING TO METHOD OF TRANSFER

Local flaps: For local flaps, tissue immediately adjacent to the defect to be reconstructed is mobilised as a flap and inset into the defect. The secondary defect can usually be closed directly without grafting. These flaps are typically used in the face and head and neck region. They are a single-stage procedure.

Distant flaps: Where no local flap is available, tissue from a distance must be transferred. Flaps from the groin or abdomen are typically used to resurface large skin defects, especially of the hand. The flap is sutured around the circumference of the defect, effectively joining the hand to the abdomen. This posture is maintained until sufficient blood supply has grown into the flap from the periphery on the hand side to allow safe detachment from the abdomen. Usually a minimum of 3 weeks is required before detachment. Other distant flaps include cross finger, cross leg, cross arm and the Tagliacozzi method of nose reconstruction. These are two-staged operations and may include an intermediate delay to reinforce the vascular connection at the recipient site. Where the defect cannot be directly brought to the flap site, such as with head and neck and lower limb defects, the multistaged tube pedicle of Gillies was originally used. Initially, a tube of skin and fat is created on the abdomen and after a period of approximately 2 months one end is detached and joined to the wrist as a carrier. The flap would remain in this position for a further 2 months, when it could be totally detached from the abdomen and transferred to the final destination still attached to the wrist. After a further period of time it could be disconnected from the wrist and inset into the final defect. Because of the impracticality of this today, the free microvascular flap has effectively superseded the tube pedicle.

Free flaps: The flap is totally detached from the body after dissecting out its blood vessel pedicle. The flap is directly transferred to the site of election and the artery and vein are anastomosed to recipient vessels in the region. All flaps that have a single identifiable vascular pedicle supply, namely, axial pattern flaps, myocutaneous or fasciocutaneous flaps (see below) can be transferred as free flaps. Free flaps vastly widen the options of available tissue for a more sophisticated reconstruction. Thin, thick, hair-bearing, innervated or composite flaps can be chosen to better match the defect.

ACCORDING TO VASCULAR BASIS OF THE FLAPS

Random pattern: All small flaps are essentially randomly vascularised, especially in the face, neck and trunk. Larger flaps, particularly if they incorporate the deeper layers, may capture a specific vertically oriented vascular perforator or subfascial horizontally directed vessel that permits much greater flexibility of flap design.

Axial: A known artery (e.g. the superficial circumflex iliac artery of the groin flap) passes along the axis of the flap; similarly, the supraorbital vessels supply the Indian rhinoplasty flap. Such flaps can be developed as island flaps; that is, as an isolated paddle of skin based purely on its blood vessel pedicle, greatly facilitating flap mobility.

Myocutaneous: The skin blood supply is dependent on attachment to its underlying muscle and both the skin and muscle must be raised as a flap to retain its blood supply (e.g. latissimus dorsi and TRAM flaps). These flaps are also commonly transferred as island pedicle flaps.

Fasciocutaneous or septocutaneous: When the blood supply arises from perforators from the deep compartment vessels and emerges via the fascioseptal layers to supply the overlying skin. Limb skin is typically vascularised in this manner.

Prefabricated flaps: Occasionally, large skin flaps are required with unique colour, texture and character to reconstruct specific defects, especially in the face and head and neck region (e.g. nose or forehead). Flaps can be purpose-designed by a process known as prefabrication, using the ability to transfer multiple tissues in stages to create a composite flap.

VARIOUS FLAPS USED FOR CLOSURE OF SKIN DEFECTS

V-Y advancement type flaps are very useful for cheek and forehead defects and can be designed in the axis of crease lines. This flap, which is designed as a V with its apex furthest from the defect, involves cutting circumferentially around it into the fatty tissue (V-Y advancement flap. (A) Design of flap. Triangular flap designed with apex away from defect and in area of laxity. (B) Incision and mobilisation of flap on subcutaneous tissue pedicle. The mobility of this tissue allows advancement of flap into defect. (C) Flap sutured into position and secondary defect closed directly behind the advanced flap.A). It survives on perforators coming up through the subcutaneous fat, which is highly mobile tissue, and allows the skin flap to be advanced into the defect (V-Y advancement flap. (A) Design of flap. Triangular flap designed with apex away from defect and in area of laxity. (B) Incision and mobilisation of flap on subcutaneous tissue pedicle. The mobility of this tissue allows advancement of flap into defect. (C) Flap sutured into position and secondary defect closed directly behind the advanced flap.B). The secondary defect is pinched together sideways as a Y (V-Y advancement flap. (A) Design of flap. Triangular flap designed with apex away from defect and in area of laxity. (B) Incision and mobilisation of flap on subcutaneous tissue pedicle. The mobility of this tissue allows advancement of flap into defect. (C) Flap sutured into position and secondary defect closed directly behind the advanced flap.C). In the temple, preauricular, lateral canthal and neck area, transposition flaps of the Limberg type are most versatile. The defect is marked out as a parallelogram. The shortest diagonal is extended the same length beyond the flap into the area of maximum laxity. The incision is then redirected the same length backwards parallel to the side of the defect (Transposition flap (Limberg flap). (A) Design of flap. Lesion/defect is marked as parallelogram, with flap designed adjacent (see text). (B) Flap elevated and transposed. (C) Flap sutured into defect and secondary defect closed directly.A). The flap is transposed into the defect and in so doing the secondary gap closes as this is in the area of laxity (Transposition flap (Limberg flap). (A) Design of flap. Lesion/defect is marked as parallelogram, with flap designed adjacent (see text). (B) Flap elevated and transposed. (C) Flap sutured into defect and secondary defect closed directly.B, C). For defects which have no immediate adjacent skin redundancy a rotation flap is required. This is typically used in the scalp. The defect is triangulated and its apex is extended in the form of a large semicircular arc (Rotation flap. (A) Design of flap. Lesion/defect triangulated and flap designed as semicircular arc from apex of defect. (B) Flap incised, elevated and rotated into defect. (C) Flap sutured into position with secondary defect closed directly.A). This flap is undermined and rotated so that the apex of the flap adjacent to the defect advances to close it (Rotation flap. (A) Design of flap. Lesion/defect triangulated and flap designed as semicircular arc from apex of defect. (B) Flap incised, elevated and rotated into defect. (C) Flap sutured into position with secondary defect closed directly.B). The secondary deficiency usually closes directly (Rotation flap. (A) Design of flap. Lesion/defect triangulated and flap designed as semicircular arc from apex of defect. (B) Flap incised, elevated and rotated into defect. (C) Flap sutured into position with secondary defect closed directly.C).

V-Y advancement flap. (A) Design of flap. Triangular flap designed with apex away from defect and in area of laxity. (B) Incision and mobilisation of flap on subcutaneous tissue pedicle. The mobility of this tissue allows advancement of flap into defect. (C) Flap sutured into position and secondary defect closed directly behind the advanced flap.

Transposition flap (Limberg flap). (A) Design of flap. Lesion/defect is marked as parallelogram, with flap designed adjacent (see text). (B) Flap elevated and transposed. (C) Flap sutured into defect and secondary defect closed directly.

Rotation flap. (A) Design of flap. Lesion/defect triangulated and flap designed as semicircular arc from apex of defect. (B) Flap incised, elevated and rotated into defect. (C) Flap sutured into position with secondary defect closed directly.

Tissue expansion

Tissue expansion involves progressive stretching of immediate adjacent tissue until enough is created to advance it directly into the defect. Scalp defects are an ideal indication as the technique reproduces the unique hair-bearing skin. It involves implanting one or more tissue expanders, empty silicone balloons, underneath the skin adjacent to the defect to be closed. Progressively over approximately 2 months, the expander, which has a valve port, is injected percutaneously with saline until sufficient volume is obtained. At this point the expander is removed and the redundant expanded skin is advanced to close the defect.

Cosmetic surgery

Operations for correction of cosmetic deformities, both congenital and acquired, have evolved since early in the 20th century. To some extent most plastic surgery includes an aesthetic ideal. Purely cosmetic procedures are technically demanding and successful outcomes require a thorough training in basic plastic surgery principles. Patient's motives and expectations may be unrealistic and not match the technical possibilities that surgery can offer. Alternatively, in this market-driven field, unscrupulous and often untrained practitioners may promote operations in an unrealistic light so that the limitations of surgery are down-played.

The most rewarding, commonly performed cosmetic operation is reduction mammaplasty. Large breasts are a source of physical discomfort, severe back and neck ache, and of psychological embarrassment. Operation is generally predictable and offers dramatic relief of symptoms. Scars, although extensive, are well disguised and accepted by the patient. Other cosmetic operations that can be of great psychological benefit are rhinoplasty, the setting back of prominent ears, augmentation mammaplasty and suction lipectomy for isolated fat reduction. Anti-ageing procedures, such as facelift, blepharoplasty, browlift and laser resurfacing, are in a different age group. Although they can be very beneficial, they are associated with a higher risk for patient dissatisfaction.
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