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Closing the gap: skin grafts and flaps
WOUND MANAGEMENT
Closing the gap: skin grafts and flaps
Tissue loss commonly occurs as a result of: trauma e burns, blast, degloving infection e necrotizing fasciitis, septicaemia tumour e either due to excision or radiotherapy vascular e venous or arterial disease or injury, pressure sores. As a result of these mechanisms, such wounds may contain devitalized, contaminated or frankly infected surfaces. The first stage of closing the gap in such wounds is to turn this unhealthy wound into a fresh clean wound by the process called debridement. Some wounds will require or benefit from coverage with the patient’s own tissue, and this can be in the form of skin grafts or flaps. Deciding which reconstructive technique is best suited requires an overall assessment of the whole patient and the wound; one must take into account site, size, depth and cleanliness of the wound, as well as patient co-morbidities, mobility, lifestyle, occupation and of course patient preference. The ‘reconstructive ladder’ below provides a structure that runs through simple to complex methods of wound management. However, not all patients or wounds are suitable for all of these options and therefore it requires skill and knowledge to work out which may be most appropriate: wound healing by secondary intention (i.e. dressings) primary wound closure skin grafting e split-thickness or full-thickness local flaps that are used to cover an adjacent or close-by defect regional flaps free flaps involve transfer of a block of tissue from one area to another site, requiring anastomosis of blood vessels for perfusion. The aim of this article is to provide information on skin grafts and flaps as reconstructive options.
Heather Le Cocq Paul RW Stanley
Abstract Wounds occur via a multitude of causal mechanisms, and vary greatly in their nature. Therefore, reconstructing such defects requires meticulous consideration of the patient and wound. Conservative measures are sometimes sufficient for healing, but some wounds will benefit from surgical reconstruction. Knowledge of the human vascular network, in particular within the fascia, subcutaneous tissue and skin, permits an understanding of the use of one’s own tissue to help heal another body site. Skin grafts are simple thin sections of tissue that lack their own blood supply, and are transferred from one site on the body to another. Flaps, however, are composite blocks of tissue that contain their own blood supply and can be moved locally, regionally, distantly or freely to the desired site. This article reviews the use of skin grafts and flaps in aiding wound closure.
Keywords Flaps; free tissue transfer; skin grafts; take; wounds
Introduction The integument of the body is composed from without to within by skin, subcutaneous fat, fascia, muscle and bone. Blood vessels supplying the integument begin as large ‘named’ vessels deep within the tissues and approach the surface by branches passing through fascial septae or through muscles as fasciocutaneous and musculocutaneous ‘perforating’ vessels respectively, dividing and getting smaller as they approach the surface. At various levels the vessels arborize to form rich plexuses of vessels, getting progressively smaller as they approach the surface. Vascular plexuses are located in the: subepidermis dermis subdermis prefascia subfascia. The epidermis has no blood vessels within it and is nourished by diffusion from the dermal arcades and subepidermal plexus (Figure 1).
Skin grafts Grafts are thin sections of tissue which lack their own blood supply and are taken from one area (donor site) and applied to another area (recipient site). The earliest known use of skin grafts was 3000 years ago. Hauben1 in a historical overview described how in the times of the Indian tilemaker caste, thieves would be punished by nasal amputation, which was subsequently skin grafted from the buttock region. Use of split skin grafts in the treatment of burns was reported by Brown and McDowell in 1942.2 Past experimental work with skin grafts in mice has provided the basis for the immunological understanding of tissue transplantation. Grafts commonly consist of one tissue, but occasionally contain a mixture, such as skin and cartilage from the ear for nasal ala reconstruction e these are known as composite grafts. Grafts used from and to the same person are autografts. They may also be used between the same species (allograft) or even between different species (xenograft). In this article we focus on skin grafts, and their use as autografts. To ‘take’, skin grafts require that the recipient wound has a ‘graftable’ bed e skin grafts will not take on exposed bone, tendon or cartilage, but they can be placed on periosteum, paratenon or perichondrium. This is because skin grafts need to acquire a new blood supply from the recipient bed. Skin grafts are used to speed up wound closure, and to provide some degree of protection from trauma as well as being a barrier to infection.
Heather Le Cocq MBBS BSc MRCS RAuxAF is a Specialist Registrar in Plastic Surgery at Castle Hill Hospital, Cottingham, Hull, UK. Conflicts of interest: none declared. Paul RW Stanley MBBS FRCS FRCS(Plast) is a Consultant Plastic Surgeon at Castle Hill Hospital, Cottingham, Hull, UK. Conflicts of interest: none declared.
SURGERY 29:10
502
Ó 2011 Elsevier Ltd. All rights reserved.
WOUND MANAGEMENT
Cross-section of the ‘integument’ of the body, showing blood supply Epidermis
Subdermal plexus
Subepidermal plexus Sweat gland
3
21
Dermis Hair follicle Fat
Prefascial plexus Subfascial Muscle plexus Musculocutaneous perforator Septocutaneous perforator
1. Thin split-skin graft 2. Standard split-skin graft 3. Full-thickness skin graft
Figure 1 Schematic of human integument.
Split-thickness versus full-thickness skin grafts A split-thickness skin graft (SSG) consists of the epidermis and part of the dermis. Due to part of the dermis (and therefore various adnexal skin appendages) being left behind, this donor site is expected to heal completely with dressings. A fullthickness skin graft (FTSG) takes the full thickness of the epidermis and dermis, and this donor site is therefore closed primarily leaving behind a linear scar. SSGs tend to fare better than FTSGs on slightly unfavourable beds. Once the graft is harvested, it undergoes primary contraction due to the elastin component of the dermis. This is more pronounced in FTSGs (shrinks by w40%) than SSGs (w10%). Over time (w6e18 months), secondary contraction occurs but this is within the recipient site rather than the graft itself. However, the thicker the graft, the less the site contracts. SSGs are more susceptible to trauma and tend to pigment more. As FTSGs maintain the adnexal skin structures such as hair follicles, sweat gland and sebaceous glands, they are capable of hair growth, sweating and oil secretion.3 Although there are exceptions, the donor site of an SSG generally heals rapidly and can be used again as a donor site after 1e2 months. An FTSG often gives a colour match and texture that is more similar than an SSG to the normal skin. FTSGs are often used to cover facial and scalp defects for skin cancers, or for congenital hand surgery. SSGs are used for the lower limb, and for large areas where great surface areas of graft are needed e for example burns, trauma and large oncological excisions.
SURGERY 29:10
Harvesting skin grafts SSGs are harvested with either an air-powered dermatome, or an electrical or battery-operated dermatome (Figure 2). Hand-held knives are rarely used any more as they tend to produce a more variable graft with rough edges. The principle is the same: a blade is set at an adjustable level behind a roller. Generally the thickness varies from 0 mm to 1 mm with 0.2 mm representing a ‘thin’ graft and 0.4 mm to 0.5 mm a ‘thick’ graft. The commonest donor sites are the thigh or gluteal region, but any part of the body including soles of the feet, and scalp can be used in patients where uninjured skin is minimal e for example in a major burn. The actual process of harvesting requires a smooth, flat surface to be presented to the surgeon, and then a steady movement with a constant pressure as the skin is taken. A slightly larger graft than the defect should be taken as the thinner the graft the more it shrinks (10e40%). The outer surface of the SSG is ‘rough’ giving it a ‘matt’ appearance. The deep surface has been cut smoothly with the knife or dermatome and so has a ‘shiny’ appearance. The skin graft is therefore applied to the donor site shiny side down. FTSGs are taken from areas of the body that ideally are a good match for the recipient, are in a cosmetically acceptable location, and where there is a little excess of thin skin such that direct closure can be attained. Common areas used are preauricular, postauricular, supraclavicular and upper eyelids for facial areas. Other sites include the forearm, volar wrist crease, antecubital fossa and groin.
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Ó 2011 Elsevier Ltd. All rights reserved.
WOUND MANAGEMENT
Figure 2 Harvesting a split skin graft with a Zimmer dermatome.
Figure 3 Graft in place on a wound, using glue to fix. Note graft has been ‘meshed’.
Meshing Meshing is the process of creating multiple small perforations within a SSG, described by Tanner et al.9 in 1964 by use of a machine. There are several benefits to this: it increases the surface area of the graft, potentially up to 12 times it allows the graft to drape well over surfaces with an irregular contour it allows the escape of seroma or blood, preventing lifting of the graft it increases the edges capable of re-epithelialization. On the negative side, the long-term appearance of a meshed graft will always be evidence that it was meshed. Also, the areas under the perforations heal by secondary intention, thereby perpetuating wound contraction.
3. Revascularization e after 48 hours there exists a fine network of blood vessels within the fibrin layer. There are two main theories as to how this occurs. Inosculation (meeting/kissing of two tubular structures) holds that vessels present within the skin graft communicate and then join with vessels in the recipient bed.7 The second theory is neovascularization, which holds that new vessels form in the recipient bed and then go into the skin graft.6 4. Remodelling e this involves the way the graft gradually over time gains the structure and architecture of normal skin. This includes re-innervation, restoration of adnexal structures and epidermal hyperplasia. With regards to healing, the skin graft gains weight initially due to imbibition. At first white, the graft develops a pinkish hue and capillary refill within a few days. By day 6, lymphatic channels have been established between graft and bed, and so the graft loses weight, returning to its pre-graft level by day 9.4 Collagen replacement starts around day 7 and is almost to normal levels by 42 days. Further vascularization and structural remodelling continues for months. Sensation may begin to reappear at 3 weeks as re-innervation occurs from the graft and wound edges, and can continue to improve over 2 years.8
Dressing The aim of a graft/recipient site dressing is to splint and hold the graft in place such that adherence and imbibition occur, and that both shear and haematoma are prevented. The graft will usually be glued or sutured to the wound edges. A ‘bolster’ or ‘tie-over’ dressing usually containing jelonet at the base is often applied (Figure 3). Sometimes a topical negative pressure therapy device is applied to provide subatmospheric pressure over large areas or difficult contours. On an extremity it may be deemed appropriate to splint with plaster to prevent movement of muscle groups below the graft that may cause shear. Graft dressings are generally left on for 3e6 days.
Causes of graft failure Causes of skin graft failure are as follows: haematoma or seroma (lifts the graft from the bed, preventing take) infection e a bacterial count of more than 105 organisms/g is deemed unsuitable for a graft, although some organisms such as b-haemolytic streptococci need only be present in small numbers to cause graft loss shear e movement of the graft against the bed, hence the need for the graft to be well secured poor recipient bed.
Skin graft take and healing Skin graft ‘take’ consists of four phases: 1. Adherence e as soon as a graft is placed on a good bed, it appears to ‘stick’ e this is due to an immediate fibrin bond between the two 2. Plasmatic imbibition e first 48 hours. It appears to allow the graft to survive the first few days while it lacks a blood supply. Plasma exudes from the recipient site capillaries, providing serum which some believe nourishes the graft.4,5 Others feel it merely keeps the graft moist and causes graft vessels to remain open whilst circulation is being established.6 Clinically, it causes graft swelling and oedema
SURGERY 29:10
Flaps A flap is a block of tissue of varying composition that contains its own blood supply. That blood supply may remain uninterrupted, or can be detached from its bed and then surgically anastomosed to recipient vessels such that they nourish the flap (Figure 4a and b).
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Ó 2011 Elsevier Ltd. All rights reserved.
WOUND MANAGEMENT
3. Source e where the flap comes from in relation to where it will be used to reconstruct. This may be: (a) Local e right next to the defect (b) Regional e same ‘area’ (e.g. shoulder, head and neck) (c) Distant e some way from the defect (e.g. a groin flap onto a hand) (d) Free e flap is completely separated from it’s source and is moved to a distant part of the body where it is surgically anastomosed. 4. Method of transfer e mainly applicable to local flaps. This includes: (a) Rotation e a semicircular-type flap rotates around a pivot point into the defect (b) Transposition e a rectangular, square or triangular flap that moves laterally around a pivot point into the adjacent defect (e.g. rhomboid flap) (c) Interpolation e also moves laterally about a pivot point, but moves into a defect that is not immediately adjacent (e.g. nasolabial flap into tip of nose under intervening skin) (d) Advancement e flap moves forwards into the defect (e.g. V-Y, Y-V). Flaps are used to cover wounds that require tissue with its own blood supply, wounds that require a greater thickness of tissue than skin grafts can give, and wounds where a flap may be felt to give a better cosmetic result than a graft. The type of flap used depends on many factors including general patient factors, local tissue available, and final functional and cosmetic/reconstructive ideals (Figure 5aed).
Earliest flaps consisted of skin and subcutaneous tissue. The original word ‘flappe’ derived from an old Dutch term meaning ‘broad and long and attached at one side’, indicating the blood supply to the flap passes through one side e known as the pedicle. It was found that the flap would survive with adequate blood supply provided the length to breadth ratio was limited. This varies in different areas of the body (e.g. leg 1:1, arm 2:1, etc.). This ratio could be increased by designing the flap along the axis of the subcutaneous vessels. A further observation that the inclusion of deep fascia in the flap would improve the survival of flaps led to fasciocutaneous flaps. Classification There are several ways of classifying flaps: 1. Circulation: (a) Random e no named vessel supplies the flap, it is ‘random’ (b) Axial e involve a named artery, and skin flaps can be subclassified as direct, fasciocutaneous, musculocutaneous and venous. 2. Composition e a flap may be composed of skin and subcutaneous tissue, fascia, muscle, bone, or varying combinations.
Free tissue transfer With the advent of microsurgery, it was found that blocks of tissue with a sufficiently large pedicle (1e2 mm) could be detached from the donor site and successfully transferred to the recipient site and anastomosed to local recipient vessels of a similar diameter. These flaps are called free flaps and their movement free tissue transfer. As microsurgical techniques, equipment and magnification have improved, the number of potential flaps based on vascular anatomy has escalated, including anastomosis of sub-millimetre perforating vessels. This has led to terminology based on vascular anatomy rather than geometry, for example a deep inferior epigastric artery perforator (DIEP) flap. In all flaps, blood supply is crucial to flap survival e however, it is in free tissue transfer where flap monitoring is so important, primarily because a sudden failure of the anastomosed vessels to flow can cause the whole flap to die and yet potentially this can be avoided by rapid pick-up of a problem and a subsequent speedy return to theatre for exploration of the flap and vessels. Anastomosis of vessels requires a microscope and a set of fine surgical instruments. Suitable patient and flap choice, good preparation of the vessels, excellent surgical technique and patient comfort (ie warm, pain-free and good urine output) are instrumental in the outcome of free tissue transfer. The flap should be monitored regularly and by the same person/people. The doctor on-call should see the flap ideally within theatre, in recovery and therein after that. When monitoring a free flap, one should look for a normal colour, capillary refill, tissue turgor, temperature and red bleeding on pinprick. Other methods of monitoring free flaps include Doppler recordings whereby a probe is placed around one
Figure 4 (a) Buttock wound after melanoma excision, and buttock flap marked out; (b) buttock flap rotated into defect.
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Ó 2011 Elsevier Ltd. All rights reserved.
WOUND MANAGEMENT
Figure 5 (a) Exposed knee prosthesis; (b) raising a gastrocnemius flap; (c) rotating gastrocnemius flap into position; (d) covering the gastrocnemius flap with split skin graft.
of the vessels and through a cutaneous exit point is attached to a Doppler machine which transmits the sound of the vessel. Laser Doppler, transcutaneous oxygen saturation and near infra-red spectroscopy may also be used.
wisdom, knowledge and experience with patient factors and preference when planning a reconstructive procedure, aided by a good rapport with the patient. A
Other forms of wound cover Although somewhat outside the scope of this article title, there are now other ways of either temporizing or covering wounds due to significant advances in research over the last two decades. Topical negative pressure devices apply mechanical suction to wounds through a dressing that may increase blood flow, encourage angiogenesis and granulation tissue formation, and reduce oedema, wound exudate and bacterial load. This can therefore minimize or even completely heal a wound with time, or convert an ungraftable bed into a graftable one. Skin substitutes have also fared and developed well, and these may be epidermal or dermal. Keratinocytes may be cultured and then applied as a sheet or a spray to large wounds. Dermal substitutes now come in many different formulations and may be used to provide a sound base to a wound that incorporates strength as well as elastic properties.
REFERENCES 1 Hauben DJ, Baruchin A, Mahler D. On the history of the free skin graft. Ann Plast Surg 1982; 9: 242. 2 Brown JB, McDowell F. Massive repairs with thick split-skin grafts; emergency “dressing” with homografts in burns. Ann Surg 1942; 115: 658. 3 Thornton JF, Gosman AA. Skin grafts and skin substitutes and principles of flaps. SRPS 2004; 10: 1. 4 Weinzweig J. Plastic surgery secrets plus. Mosby Elsevier, 2010. 5 Pepper FJ. Studies on the viability of mammalian skin autografts after storage at different temperatures. Br J Plast Surg 1954; 6: 250. 6 Converse JM, Smahel J, Ballantyne Jr DL, Harper AD. Inosculation of vessels of skin graft and host bed: a fortuitous encounter. Br J Plast Surg 1975; 28: 274. 7 Clemmesen T. Experimental studies on the healing of free skin autografts. Danish Med Bull 1967; 14(suppl 11). 8 Stone C. Plastic surgery facts. Greenwich Medical Media Ltd, 2001. 9 Tanner JC, Vandeput J, Olley JF. The mesh skin graft. Plast Reconstr Surg 1964; 34: 287.
Conclusion In conclusion, there are many different ways of covering a soft tissue defect, and the art and science of this lies in blending
SURGERY 29:10
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Ó 2011 Elsevier Ltd. All rights reserved.
Closing the gap: skin grafts and flaps
Tissue loss commonly occurs as a result of: trauma e burns, blast, degloving infection e necrotizing fasciitis, septicaemia tumour e either due to excision or radiotherapy vascular e venous or arterial disease or injury, pressure sores. As a result of these mechanisms, such wounds may contain devitalized, contaminated or frankly infected surfaces. The first stage of closing the gap in such wounds is to turn this unhealthy wound into a fresh clean wound by the process called debridement. Some wounds will require or benefit from coverage with the patient’s own tissue, and this can be in the form of skin grafts or flaps. Deciding which reconstructive technique is best suited requires an overall assessment of the whole patient and the wound; one must take into account site, size, depth and cleanliness of the wound, as well as patient co-morbidities, mobility, lifestyle, occupation and of course patient preference. The ‘reconstructive ladder’ below provides a structure that runs through simple to complex methods of wound management. However, not all patients or wounds are suitable for all of these options and therefore it requires skill and knowledge to work out which may be most appropriate: wound healing by secondary intention (i.e. dressings) primary wound closure skin grafting e split-thickness or full-thickness local flaps that are used to cover an adjacent or close-by defect regional flaps free flaps involve transfer of a block of tissue from one area to another site, requiring anastomosis of blood vessels for perfusion. The aim of this article is to provide information on skin grafts and flaps as reconstructive options.
Heather Le Cocq Paul RW Stanley
Abstract Wounds occur via a multitude of causal mechanisms, and vary greatly in their nature. Therefore, reconstructing such defects requires meticulous consideration of the patient and wound. Conservative measures are sometimes sufficient for healing, but some wounds will benefit from surgical reconstruction. Knowledge of the human vascular network, in particular within the fascia, subcutaneous tissue and skin, permits an understanding of the use of one’s own tissue to help heal another body site. Skin grafts are simple thin sections of tissue that lack their own blood supply, and are transferred from one site on the body to another. Flaps, however, are composite blocks of tissue that contain their own blood supply and can be moved locally, regionally, distantly or freely to the desired site. This article reviews the use of skin grafts and flaps in aiding wound closure.
Keywords Flaps; free tissue transfer; skin grafts; take; wounds
Introduction The integument of the body is composed from without to within by skin, subcutaneous fat, fascia, muscle and bone. Blood vessels supplying the integument begin as large ‘named’ vessels deep within the tissues and approach the surface by branches passing through fascial septae or through muscles as fasciocutaneous and musculocutaneous ‘perforating’ vessels respectively, dividing and getting smaller as they approach the surface. At various levels the vessels arborize to form rich plexuses of vessels, getting progressively smaller as they approach the surface. Vascular plexuses are located in the: subepidermis dermis subdermis prefascia subfascia. The epidermis has no blood vessels within it and is nourished by diffusion from the dermal arcades and subepidermal plexus (Figure 1).
Skin grafts Grafts are thin sections of tissue which lack their own blood supply and are taken from one area (donor site) and applied to another area (recipient site). The earliest known use of skin grafts was 3000 years ago. Hauben1 in a historical overview described how in the times of the Indian tilemaker caste, thieves would be punished by nasal amputation, which was subsequently skin grafted from the buttock region. Use of split skin grafts in the treatment of burns was reported by Brown and McDowell in 1942.2 Past experimental work with skin grafts in mice has provided the basis for the immunological understanding of tissue transplantation. Grafts commonly consist of one tissue, but occasionally contain a mixture, such as skin and cartilage from the ear for nasal ala reconstruction e these are known as composite grafts. Grafts used from and to the same person are autografts. They may also be used between the same species (allograft) or even between different species (xenograft). In this article we focus on skin grafts, and their use as autografts. To ‘take’, skin grafts require that the recipient wound has a ‘graftable’ bed e skin grafts will not take on exposed bone, tendon or cartilage, but they can be placed on periosteum, paratenon or perichondrium. This is because skin grafts need to acquire a new blood supply from the recipient bed. Skin grafts are used to speed up wound closure, and to provide some degree of protection from trauma as well as being a barrier to infection.
Heather Le Cocq MBBS BSc MRCS RAuxAF is a Specialist Registrar in Plastic Surgery at Castle Hill Hospital, Cottingham, Hull, UK. Conflicts of interest: none declared. Paul RW Stanley MBBS FRCS FRCS(Plast) is a Consultant Plastic Surgeon at Castle Hill Hospital, Cottingham, Hull, UK. Conflicts of interest: none declared.
SURGERY 29:10
502
Ó 2011 Elsevier Ltd. All rights reserved.
WOUND MANAGEMENT
Cross-section of the ‘integument’ of the body, showing blood supply Epidermis
Subdermal plexus
Subepidermal plexus Sweat gland
3
21
Dermis Hair follicle Fat
Prefascial plexus Subfascial Muscle plexus Musculocutaneous perforator Septocutaneous perforator
1. Thin split-skin graft 2. Standard split-skin graft 3. Full-thickness skin graft
Figure 1 Schematic of human integument.
Split-thickness versus full-thickness skin grafts A split-thickness skin graft (SSG) consists of the epidermis and part of the dermis. Due to part of the dermis (and therefore various adnexal skin appendages) being left behind, this donor site is expected to heal completely with dressings. A fullthickness skin graft (FTSG) takes the full thickness of the epidermis and dermis, and this donor site is therefore closed primarily leaving behind a linear scar. SSGs tend to fare better than FTSGs on slightly unfavourable beds. Once the graft is harvested, it undergoes primary contraction due to the elastin component of the dermis. This is more pronounced in FTSGs (shrinks by w40%) than SSGs (w10%). Over time (w6e18 months), secondary contraction occurs but this is within the recipient site rather than the graft itself. However, the thicker the graft, the less the site contracts. SSGs are more susceptible to trauma and tend to pigment more. As FTSGs maintain the adnexal skin structures such as hair follicles, sweat gland and sebaceous glands, they are capable of hair growth, sweating and oil secretion.3 Although there are exceptions, the donor site of an SSG generally heals rapidly and can be used again as a donor site after 1e2 months. An FTSG often gives a colour match and texture that is more similar than an SSG to the normal skin. FTSGs are often used to cover facial and scalp defects for skin cancers, or for congenital hand surgery. SSGs are used for the lower limb, and for large areas where great surface areas of graft are needed e for example burns, trauma and large oncological excisions.
SURGERY 29:10
Harvesting skin grafts SSGs are harvested with either an air-powered dermatome, or an electrical or battery-operated dermatome (Figure 2). Hand-held knives are rarely used any more as they tend to produce a more variable graft with rough edges. The principle is the same: a blade is set at an adjustable level behind a roller. Generally the thickness varies from 0 mm to 1 mm with 0.2 mm representing a ‘thin’ graft and 0.4 mm to 0.5 mm a ‘thick’ graft. The commonest donor sites are the thigh or gluteal region, but any part of the body including soles of the feet, and scalp can be used in patients where uninjured skin is minimal e for example in a major burn. The actual process of harvesting requires a smooth, flat surface to be presented to the surgeon, and then a steady movement with a constant pressure as the skin is taken. A slightly larger graft than the defect should be taken as the thinner the graft the more it shrinks (10e40%). The outer surface of the SSG is ‘rough’ giving it a ‘matt’ appearance. The deep surface has been cut smoothly with the knife or dermatome and so has a ‘shiny’ appearance. The skin graft is therefore applied to the donor site shiny side down. FTSGs are taken from areas of the body that ideally are a good match for the recipient, are in a cosmetically acceptable location, and where there is a little excess of thin skin such that direct closure can be attained. Common areas used are preauricular, postauricular, supraclavicular and upper eyelids for facial areas. Other sites include the forearm, volar wrist crease, antecubital fossa and groin.
503
Ó 2011 Elsevier Ltd. All rights reserved.
WOUND MANAGEMENT
Figure 2 Harvesting a split skin graft with a Zimmer dermatome.
Figure 3 Graft in place on a wound, using glue to fix. Note graft has been ‘meshed’.
Meshing Meshing is the process of creating multiple small perforations within a SSG, described by Tanner et al.9 in 1964 by use of a machine. There are several benefits to this: it increases the surface area of the graft, potentially up to 12 times it allows the graft to drape well over surfaces with an irregular contour it allows the escape of seroma or blood, preventing lifting of the graft it increases the edges capable of re-epithelialization. On the negative side, the long-term appearance of a meshed graft will always be evidence that it was meshed. Also, the areas under the perforations heal by secondary intention, thereby perpetuating wound contraction.
3. Revascularization e after 48 hours there exists a fine network of blood vessels within the fibrin layer. There are two main theories as to how this occurs. Inosculation (meeting/kissing of two tubular structures) holds that vessels present within the skin graft communicate and then join with vessels in the recipient bed.7 The second theory is neovascularization, which holds that new vessels form in the recipient bed and then go into the skin graft.6 4. Remodelling e this involves the way the graft gradually over time gains the structure and architecture of normal skin. This includes re-innervation, restoration of adnexal structures and epidermal hyperplasia. With regards to healing, the skin graft gains weight initially due to imbibition. At first white, the graft develops a pinkish hue and capillary refill within a few days. By day 6, lymphatic channels have been established between graft and bed, and so the graft loses weight, returning to its pre-graft level by day 9.4 Collagen replacement starts around day 7 and is almost to normal levels by 42 days. Further vascularization and structural remodelling continues for months. Sensation may begin to reappear at 3 weeks as re-innervation occurs from the graft and wound edges, and can continue to improve over 2 years.8
Dressing The aim of a graft/recipient site dressing is to splint and hold the graft in place such that adherence and imbibition occur, and that both shear and haematoma are prevented. The graft will usually be glued or sutured to the wound edges. A ‘bolster’ or ‘tie-over’ dressing usually containing jelonet at the base is often applied (Figure 3). Sometimes a topical negative pressure therapy device is applied to provide subatmospheric pressure over large areas or difficult contours. On an extremity it may be deemed appropriate to splint with plaster to prevent movement of muscle groups below the graft that may cause shear. Graft dressings are generally left on for 3e6 days.
Causes of graft failure Causes of skin graft failure are as follows: haematoma or seroma (lifts the graft from the bed, preventing take) infection e a bacterial count of more than 105 organisms/g is deemed unsuitable for a graft, although some organisms such as b-haemolytic streptococci need only be present in small numbers to cause graft loss shear e movement of the graft against the bed, hence the need for the graft to be well secured poor recipient bed.
Skin graft take and healing Skin graft ‘take’ consists of four phases: 1. Adherence e as soon as a graft is placed on a good bed, it appears to ‘stick’ e this is due to an immediate fibrin bond between the two 2. Plasmatic imbibition e first 48 hours. It appears to allow the graft to survive the first few days while it lacks a blood supply. Plasma exudes from the recipient site capillaries, providing serum which some believe nourishes the graft.4,5 Others feel it merely keeps the graft moist and causes graft vessels to remain open whilst circulation is being established.6 Clinically, it causes graft swelling and oedema
SURGERY 29:10
Flaps A flap is a block of tissue of varying composition that contains its own blood supply. That blood supply may remain uninterrupted, or can be detached from its bed and then surgically anastomosed to recipient vessels such that they nourish the flap (Figure 4a and b).
504
Ó 2011 Elsevier Ltd. All rights reserved.
WOUND MANAGEMENT
3. Source e where the flap comes from in relation to where it will be used to reconstruct. This may be: (a) Local e right next to the defect (b) Regional e same ‘area’ (e.g. shoulder, head and neck) (c) Distant e some way from the defect (e.g. a groin flap onto a hand) (d) Free e flap is completely separated from it’s source and is moved to a distant part of the body where it is surgically anastomosed. 4. Method of transfer e mainly applicable to local flaps. This includes: (a) Rotation e a semicircular-type flap rotates around a pivot point into the defect (b) Transposition e a rectangular, square or triangular flap that moves laterally around a pivot point into the adjacent defect (e.g. rhomboid flap) (c) Interpolation e also moves laterally about a pivot point, but moves into a defect that is not immediately adjacent (e.g. nasolabial flap into tip of nose under intervening skin) (d) Advancement e flap moves forwards into the defect (e.g. V-Y, Y-V). Flaps are used to cover wounds that require tissue with its own blood supply, wounds that require a greater thickness of tissue than skin grafts can give, and wounds where a flap may be felt to give a better cosmetic result than a graft. The type of flap used depends on many factors including general patient factors, local tissue available, and final functional and cosmetic/reconstructive ideals (Figure 5aed).
Earliest flaps consisted of skin and subcutaneous tissue. The original word ‘flappe’ derived from an old Dutch term meaning ‘broad and long and attached at one side’, indicating the blood supply to the flap passes through one side e known as the pedicle. It was found that the flap would survive with adequate blood supply provided the length to breadth ratio was limited. This varies in different areas of the body (e.g. leg 1:1, arm 2:1, etc.). This ratio could be increased by designing the flap along the axis of the subcutaneous vessels. A further observation that the inclusion of deep fascia in the flap would improve the survival of flaps led to fasciocutaneous flaps. Classification There are several ways of classifying flaps: 1. Circulation: (a) Random e no named vessel supplies the flap, it is ‘random’ (b) Axial e involve a named artery, and skin flaps can be subclassified as direct, fasciocutaneous, musculocutaneous and venous. 2. Composition e a flap may be composed of skin and subcutaneous tissue, fascia, muscle, bone, or varying combinations.
Free tissue transfer With the advent of microsurgery, it was found that blocks of tissue with a sufficiently large pedicle (1e2 mm) could be detached from the donor site and successfully transferred to the recipient site and anastomosed to local recipient vessels of a similar diameter. These flaps are called free flaps and their movement free tissue transfer. As microsurgical techniques, equipment and magnification have improved, the number of potential flaps based on vascular anatomy has escalated, including anastomosis of sub-millimetre perforating vessels. This has led to terminology based on vascular anatomy rather than geometry, for example a deep inferior epigastric artery perforator (DIEP) flap. In all flaps, blood supply is crucial to flap survival e however, it is in free tissue transfer where flap monitoring is so important, primarily because a sudden failure of the anastomosed vessels to flow can cause the whole flap to die and yet potentially this can be avoided by rapid pick-up of a problem and a subsequent speedy return to theatre for exploration of the flap and vessels. Anastomosis of vessels requires a microscope and a set of fine surgical instruments. Suitable patient and flap choice, good preparation of the vessels, excellent surgical technique and patient comfort (ie warm, pain-free and good urine output) are instrumental in the outcome of free tissue transfer. The flap should be monitored regularly and by the same person/people. The doctor on-call should see the flap ideally within theatre, in recovery and therein after that. When monitoring a free flap, one should look for a normal colour, capillary refill, tissue turgor, temperature and red bleeding on pinprick. Other methods of monitoring free flaps include Doppler recordings whereby a probe is placed around one
Figure 4 (a) Buttock wound after melanoma excision, and buttock flap marked out; (b) buttock flap rotated into defect.
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WOUND MANAGEMENT
Figure 5 (a) Exposed knee prosthesis; (b) raising a gastrocnemius flap; (c) rotating gastrocnemius flap into position; (d) covering the gastrocnemius flap with split skin graft.
of the vessels and through a cutaneous exit point is attached to a Doppler machine which transmits the sound of the vessel. Laser Doppler, transcutaneous oxygen saturation and near infra-red spectroscopy may also be used.
wisdom, knowledge and experience with patient factors and preference when planning a reconstructive procedure, aided by a good rapport with the patient. A
Other forms of wound cover Although somewhat outside the scope of this article title, there are now other ways of either temporizing or covering wounds due to significant advances in research over the last two decades. Topical negative pressure devices apply mechanical suction to wounds through a dressing that may increase blood flow, encourage angiogenesis and granulation tissue formation, and reduce oedema, wound exudate and bacterial load. This can therefore minimize or even completely heal a wound with time, or convert an ungraftable bed into a graftable one. Skin substitutes have also fared and developed well, and these may be epidermal or dermal. Keratinocytes may be cultured and then applied as a sheet or a spray to large wounds. Dermal substitutes now come in many different formulations and may be used to provide a sound base to a wound that incorporates strength as well as elastic properties.
REFERENCES 1 Hauben DJ, Baruchin A, Mahler D. On the history of the free skin graft. Ann Plast Surg 1982; 9: 242. 2 Brown JB, McDowell F. Massive repairs with thick split-skin grafts; emergency “dressing” with homografts in burns. Ann Surg 1942; 115: 658. 3 Thornton JF, Gosman AA. Skin grafts and skin substitutes and principles of flaps. SRPS 2004; 10: 1. 4 Weinzweig J. Plastic surgery secrets plus. Mosby Elsevier, 2010. 5 Pepper FJ. Studies on the viability of mammalian skin autografts after storage at different temperatures. Br J Plast Surg 1954; 6: 250. 6 Converse JM, Smahel J, Ballantyne Jr DL, Harper AD. Inosculation of vessels of skin graft and host bed: a fortuitous encounter. Br J Plast Surg 1975; 28: 274. 7 Clemmesen T. Experimental studies on the healing of free skin autografts. Danish Med Bull 1967; 14(suppl 11). 8 Stone C. Plastic surgery facts. Greenwich Medical Media Ltd, 2001. 9 Tanner JC, Vandeput J, Olley JF. The mesh skin graft. Plast Reconstr Surg 1964; 34: 287.
Conclusion In conclusion, there are many different ways of covering a soft tissue defect, and the art and science of this lies in blending
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