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Tissue expansion: a reconstructive revolution or a cornucopia of complications?
British Jourd of Plastic Surgery (1990), 43.344-348 IQ 1990 The Trustees of British Association of Plastic Surgeons
Tissue expansion: a reconstructive cornucopia of complications?*
revolution or a
M. R. MASSER Salkbury, Wiltshire
“Is it a revolt?” inquired Louis XVI, just 200 years ago. “No, Sire; it is a revolution” replied the Due de la Rochefoucauld-Liancourt. Inability to recognise a revolution cost King Louis his head. It has always been the mark of a statesman to be able to recognise a revolutionary situation from within its evolving vortex. This also holds true for a surgeon. Whereas the political revolution may neither be inevitable nor have a profound impact on future generations, it is the industrial revolution, derived from the practical applications of science, that shapes the lives of so many of the human race. The twentieth century has seen developments in medical science and technology which, as a source of public interest, now displace the ceaseless advances in engineering that facilitate them. Peoples of the affluent countries, spared of repression, hunger and uncontrolled infection, turn increasingly to the medical profession for newer and more complete answers to their individual problems. Criteria for success have changed. In the Western World, a doubling of national medical expenditure may now have a zero or marginal effect on life expectancy. Plastic surgery is concerned with, above all, the correction and restoration of form. Political revolutionaries, as their heirs in Eastern Europe must now painfully recognise, are by no means offered “the blank sheet of infinite possibility”. This was an observation by Professor Michael Oakshott in his famous essay on political education, but is the possibility to be more of a reality for us, backed by science and encouraged by public demand? For thousands of years it must have been apparent to many that the solution for a particular defect or unsightly anomaly might be surgical, although such an intervention would never be made. The recent developments in tissue expansion are best seen in the context of the history of the specialty. Punitive rhinectomy in India was practised for so long and on so many victims, leading to so * Kay-Kilner
Prize Essay 1989
conspicuous a disfigurement that it is not surprising that a complicated and painful surgical treatment was finally developed and accepted. The idea of the forehead rhinoplasty was daring and original but it certainly did not represent the onset of a reconstructive revolution. Centuries passed before the range and number of procedures could initiate that logarithmic increase, a part of which we are now experiencing. This is because so much of medicine advances in concert and is dependent upon other sciences, as well as upon the wealth and social change derived from industry. Enrico Fermi recognised that for nuclear fission, which had always occurred, to detonate a chain reaction, the number and the density of atoms must exceed critical values. The effect was shattering and quite revolutionary. Expanding urban populations with widespread education, and the vast concentrations of trauma brought about by mechanised warfare, finally caused Plastic Surgery to emerge. The effect was less dramatic but it did mark the beginning of progressive changes in surgery, in medical attitudes and in public aspirations. The idea of the split thickness skin graft must have been the most valuable single innovation in surgical reconstruction. Dependant upon anaesthesia, special instruments and new skills, this procedure has gained increasing application during the last 100 years. Severe problems of scar contracture in the face and neck, large fistulae, exposed bone and the advent of radiotherapy demanded the transfer of distant soft tissue flaps. For over half a century after the Great War, the multi-staged tubed pedicle flap provided a solution for most of these cases. The skilled handling of this randomly vascularised and revascularised tissue became synonymous with the new specialty of Plastic Surgery. The limitations of the tubed pedicle technique were the inappropriate skin quality in the face and scalp and the long time for completion-six months for an exposed tibia and more
344
TISSUE EXPANSION:
A RECONSTRUCTIVE
REVOLUTION
OR A CORNUCOPIA
than twelve for a facial reconstruction. The great complication was tissue necrosis following a delay, a transfer or a revision. Before the first murmur of clinical audit, complications received much less attention than did successful results, but it does seem that even the most experienced surgeons were unable to preserve more than 80% of their flaps to completion and, overall, probably 50% were lost. This may well have represented a uniquely expensive surgical complication rate in spite of the wide acclaim for the method. In the 1960s and 70s the definition of cutaneous vascular territories brought the many named axial flaps with or without fascia, muscle and other tissues. These can be raised to considerable length in one stage and the narrow pedicles allow a wide arc of transposition. They can be used for emergency repairs and when raised under ideal conditions, a failure or major complication rate of less than 1% can be attained. This is comparable with a range of clean elective surgical operations. Most axial flaps can be transferred to more distant sites by a microvascular restoration of the circulation. Initially high failure rates are still being reduced and a figure below 10% may now be attained from a large free flap series. Tissue necrosis does, of course, mean complete loss of the flap although the cost of this is limited by the relatively short time course. The rapid and reliable repair of most defects in most patients had become possible but with so many results the external appearance remained a disappointment. Something new and different would be required: De Bono’s lateral thought concept. Since the earliest times, surgeons have had the opportunity to observe the growth in various regions and structures of the body induced by local forces. The enlargement of a breast from 100 grams to 2000 grams involves a considerable increase in skin surface area but the skin and its blood supply might be regarded as a part of the enlarging gland. In contrast, a giant cyst or a long neglected benign tumour can progressively distend overlying skin without contributing to the circulation. The surgeon in search of flaps from sites where none were hitherto available might have gained an idea for the solution. A further clue came from the ancient ritual practices of earlobe and lip stretching and from neck lengthening. These involve the even application of pressure from external appliances. In the 1950s serial filling of a subcutaneous balloon had been used to increase skin surface area, preparing a space for the cartilage grafts of an ear
OF COMPLICATIONS?
345
reconstruction. Just as revascularised organ allografts and even the reconstructive use of transplanted jejunum had long preceded the clinical application of the free flap, so it was that the tissue expander only slowly came into use in the 197Osmainly for post-mastectomy breast reconstruction-gaining more general acceptance and application in the 1980s. The widespread use of large permanent silicone implants for augmentation mammoplasty certainly gave plastic surgeons the confidence to insert tissue expanders. Similarly, the manufacture of reliable silicone rubber shells by the process of dipping mandrils took place in the existing breast implant factories. Self-sealing membranes have a long industrial history and subcutaneous injection portals had been developed to a high standard for safe long-term central venous access in the 1970s. The possibility was a reality but the concept of growth induction was as completely novel for the plastic surgeons of the 1980s as had been the free flaps and the split skin grafts in earlier times. The potential for further advances in reconstruction was equally great but acceptance by any individual surgeon was becoming dependant upon the costbenefit ratio in that practice. Part of the cost is the price of the apparatus, which may be prohibitive in the less industrialised countries. Most of the rest is time. In all but certain breast operations, two surgical procedures are required. Between them, up to twenty sterile saline injections must be administered. If the injections are made by the specialist, as an outpatient procedure, good control can be maintained and the earliest sign of any complication can be detected. Alternatively, strict training in sterile technique and in recognition of problems, together with a pressure-limiting infusion set, can allow filling of the expanders by the patients at home, with cost saving but, hopefully, no great increase in complications. Major complications may be defined as those which abort the expansion and prevent the intended outcome. Minor complications are those which require treatment, may slow down the programme and incur expense but do not affect the final result. In addition, there are the complications of general or regional anaesthesia, common to other surgical procedures. These can be considered separately. A high complication rate is a major consideration in cost-benefit analysis. For every procedure there is a learning curve. For some surgeons this means good results from the outset but a progressive reduction in time requirement. For others it means an initially
346 high failure rate which can sometimes result in early abandonment of the technique. For those who persist, costs can be reduced by increasing procedural efficiency and by recognising and eliminating those factors which cause complications, The other side of the equation is benefit. If this is defined as a simple goal such as the elimination of a large benign skin lesion and covering the defect, then most existing reconstructive procedures defeat tissue expansion in a simple cost-benefit comparison. Expanders are usually employed when the highest standard of durable or aesthetic result is required and, in these circumstances, there may be no alternative with which to compare. There are several properties which make the expanded flap unique. For a repair of good appearance the most relevant skin flap is likely to be derived from adjacent tissue. This is particularly true in the face and neck but, most of all, in the scalp. The surface area of the donor skin can be reliably doubled but, with greater risk of problems, it can be tripled. In the face and neck, expanders are best inserted in the plane superficial to the frontalis/SMAS/platysma plane so that large, thin resurfacing flaps are generated without disturbing the muscles of facial animation. After an area expansion of over 100x, marked telangiectasia is seen as the flap thickness declines to about 3 mm. With such thinning of fat and with a circulation passing only in the plane of the flap it is not surprising that dermal blood vessels become conspicuous. Telangiectasia is not a complication because it regresses after flap transfer when the deep circulation, perpendicular to the skin, is restored. Since striae are not a recognised problem in the neck and face, the final appearance of these greatly expanded skin flaps is remarkably normal. They do not carry intact peripheral nerve branches with them but, like full thickness skin grafts, they reinnervate from the recipient facial sensory nerves over one to two years. In the scalp, the most important consideration is hair density since the major operative indication is the restoration of natural-appearing, even hair cover. When 50% of the scalp has been lost, expansion of the remainder, together with some elevation of the lateral and neck hairlines, can just provide an adequate appearance when hair shaft diameters are great and follicle densities high. At the same time, expanded scalp flaps will provide a strong, mobile, independently vascularised continuation of the frontalis/galea/ occipitalis system. The incorporation of a sensory nerve, which lengthens with expansion, allows the
BRITISH JOURNAL
OF PLASTIC SURGERY
scalp flap to provide protective sensation over the cranium. When a local flap has been transposed, the scar extends only around three sides of the flap and some way into the donor area. When a simple advancement has been possible, the final scar is but a single line. Sufficient expansion prior to flap transfer facilitates closure without any tension and this contributes to the narrowest scars. When these aspects of reconstruction by tissue expansion have been considered, there may be no equally satisfactory alternative. The cost can only be balanced against utility: the product of the improvement in the quality of life and the expectancy in years. This is the justification for an elaborate means of providing the best result in a young patient. When the decision has been made to use expansion, the considerations are those of planning how to obtain this optimum result with the lowest cost in time and complications. Tissue expander systems can leak, but the frequency and extent of this is entirely a function of design, manufacture and subsequent handling. Sterile isotonic saline is universally used as the hydraulic fluid so that a small leakage represents only a minor or insignificant complication. Such small leaks occur from the filling portals, several makes of which were not designed according to self-sealing principles. For minimising losses, they depend upon the use of needles finer than 22 gauge and avoidance of tearing at the injection site. At the time of the first injection, some serum will surround the whole system and this may run out of the injection site after the needle has been withdrawn. It can be confused with a system leak unless a coloured dye has been introduced into the expander. Inadvertent puncture of the tubing or of the expander shell-the latter especially when the filling portal is integral rather than remote-always necessitates reoperation and replacement of all or a part of the system. Silicone tubing will often tear when stretched after its surface has been scored by instruments. The poorer expanders, designed without stress testing, may fracture as a result of the fatigue imposed by constant motion. The sites of weakness can be predicted and are most often adjacent to areas of excess rigidity, such as backing plates, thick joins of tubing to shell and excessive thickness of the tube wall. Connectors within the tubing or between the tube and the portal provide valuable versatility in portal placement and limitation of dissection but they do represent another source of failure. The connectors may be incapable
TISSUE EXPANSION:
A RECONSTRUCTIVE
REVOLUTION
OR A CORNUCOPIA
of withstanding tension or pressure, but they are also potential sites for tube damage. Tube occlusion through kinking occurs when the internal diameter is too great, but narrow tubes are easily blocked by any particles such as arise from the accidental introduction of blood. Much consideration has been given to the location and closure of the wound used for the insertion of the device. Remotely placed radial incisions are certainly not stressed by the filling of the expander but such a design will usually result in a blind dissection and an unnecessary additional scar. A more convenient incision line is along one of the edges of the proposed flap so that the scar will be subsequently incorporated. This closure will be near to or even overlying the edge of the expander shell, but wound breakdown can be reduced well below the 5% level. Closure requires suture in two distinct layers with a fine absorbable synthetic material, removal of any skin sutures-if used-within 5 days, before sinuses can form, and limitation of the filling pressure. Such an expander can be first filled after only 7 days, for at a pressure of only 20 mm mercury there is no danger of breakdown. From porcine experiments we know how progressive stressing of the wound results in the highest tensile strength. As with all the earlier generations of reconstructive flaps, the start of a major complication in flap expansion or transfer is likely to be a zone of necrosis. Critical ischaemia and aseptic infarction in a decubitus ulcer usually starts in proximity to the bony prominence, with only secondary skin breakdown. It seems that the same process can take place over a tissue expander. Perfusion declines rapidly at pressures above the local aterial diastolic and ceases above systolic, but transcutaneous oxygen tensions fall steadily with increasing pressure from low levels. Blanching of the skin indicates full thickness zero perfusion in that area, but for the thick flap one must merely assume deep ischaemia in the capsule and adjacent tissue when the pressure is excessive. Folding or knuckling of the silicone shell beneath a thin flap can result in local pressure necrosis. The solution lies in early recognition, external manipulation, overinflating, deflating and reinflating or occasionally in open repositioning. A rigid backing plate on a convex surface, such as the cranium, is likely to result in local pressure damage. The junction between tube and shell should be on the deep surface of the expander shell, although one can imagine the same damage occurring to underlying structures. The
OF COMPLICATIONS?
347
juvenile cranium tends to flatten in response to scalp expansion but after flap transfer, convexity is restored. In contrast, the depressed ribs resulting from subpectoral expansion in breast reconstruction are maintained and even worsened by the subsequent use of a prosthesis. An ill-placed injection portal can result in skin breakdown over the dome. Sites overlying bone, especially the mastoid, are notorious. Flap necrosis, unrelated to pressure, is a function of flap design. During initial insertion, safe limits of skin or fascial undermining must be observed. The expander produces a continued delay effect. Advancement flaps are therefore reliable, but transposition flaps must have anatomy which would result in survival had no more than a deep delay been carried out, although the flap length can be greater but only in proportion to the linear expansion ratio. In many parts of the body the most valuable and dramatically effective flaps may be intrinsically unsafe transpositions of giant skin flaps, very thin and with only random circulation. These can be made safer by delay procedures at the end of the expansion process, dividing skin and subdermal vessels along the transposition incision lines but leaving the intact capsule. Previously irradiated or scarred soft tissue has reduced elasticity and reduced growth potential. When expanded flaps are attempted in these areas, ischaemia and breakdown are so common as to transform complication statistics and to incur excessive costs. It may be safer and more effective to pre-expand a reliable free flap donor site and then to transfer this tissue to undamaged blood vessels adjacent to the scarred recipient site. When it occurs, sepsis very often turns out to be a major complication causing failure of the planned treatment, yet, with due care, the infection rate following insertion of a silicone expander should be no greater than that following a breast implant or a hip prosthesis. The aim should be a sepsis rate of less than 0.5%. The factors contributing to infection can be identified and avoided. Open wounds, ulcers or abrasions near to the expander risk lymph-borne bacterial invasion, and sepsis in other parts of the body makes for a risk of haematogenous spread to a vulnerable site where a large foreign body is in contact with relative tissue hypoxia. Dissection and haemostasis under direct vision, followed by vacuum drainage, will minimise haematoma, and the balancing of intraluminal pressure against interstitial colloid osmotic pressure avoids subsequent seroma. Deep zones of pressure necrosis, not manifesting as flap breakdown, may nonetheless
348 form the focus for sepsis. The stitch abscess, which in many operations is a nuisance, is likely in these cases to be the start of a major complication. There are other less frequent but avoidable problems which do necessitate reoperation. Too slow an initiation and rate of expansion can result in early contraction of a thickening fibrous capsule. Ill-placement of a portal can result in its rotation and loss of access. Both require surgical revision. Effects on peripheral nerves are inevitable consequences of tissue expansion. The intention may be specifically to lengthen a major nerve such as the median in the forearm or it may be to lengthen an innervated flap such as in the scalp or forearm. In other cases, nerves in the vicinity of the expander are incidentally tensioned or compressed by the applied pressure. In the early stages of expansion a nerve with good conduction can cause pain when subjected toonly 40 mm mercury and so the pressure must be further reduced. Pain need not be an obligatory symptom of expansion. Later these middle range pressures cause some loss of conduction through neurapraxia and there is less discomfort. Lengthened nerves can certainly regain conduction and so it is likely that axonotmesis only results from excess pressure-even when temporary and localised. Suckled by the plentiful horn of Amalthea, young Zeus grew to be an omnipotent deity. The mythical cornucopia was a portent of the late twentieth century products of applied science. A little of that succour is available to all in the industrialised world. When complication rates are high and misfortune plentiful, the cornucopia is the satyrical horn of
BRITISH JOURNAL
OF PLASTIC SURGERY
cuckoldry and the hapless patient is made the cuckold of the clinically errant surgeon, Although high tissue expansion failure rates in the order of 3040% have been reported, we now know that with some of the precautions, briefly alluded to above, the major complication rate can be held below 5% and total complications below 10% during large series of complex reconstructions. This is compatible with the acceptance of a successful technique in plastic surgery, and can ensure the all-important low ratio of cost-utility. With such minimised inpatient stay and constrained costs, further development may continue. If plastic surgery is undergoing revolution then that is only as- a part of the medical revolution which is itself so dependent upon social, industrial and scientific change. Tissue expansion techniques in their present form must now be seen as part of the evolving medical applications of morphogenetic induction and can hardly be excluded from that minor revolution. There is simultaneously a philosophical change. Now, for the first time in history we can present our patients and, through politics, the electorate in general with a great range of treatment options. In the individual case and for large groups taken together, benefits must now be balanced against cost. The potential for quantity and quality of supply is great. Tissue expansion has helped to make reconstructive work into the true surgical cornucopia. The Author Michael R. Maser, Surgery, Odstock
FRCS, MRCP, Senior Registrar Hospital, Salisbury, Wiltshire.
in Plastic
Tissue expansion: a reconstructive cornucopia of complications?*
revolution or a
M. R. MASSER Salkbury, Wiltshire
“Is it a revolt?” inquired Louis XVI, just 200 years ago. “No, Sire; it is a revolution” replied the Due de la Rochefoucauld-Liancourt. Inability to recognise a revolution cost King Louis his head. It has always been the mark of a statesman to be able to recognise a revolutionary situation from within its evolving vortex. This also holds true for a surgeon. Whereas the political revolution may neither be inevitable nor have a profound impact on future generations, it is the industrial revolution, derived from the practical applications of science, that shapes the lives of so many of the human race. The twentieth century has seen developments in medical science and technology which, as a source of public interest, now displace the ceaseless advances in engineering that facilitate them. Peoples of the affluent countries, spared of repression, hunger and uncontrolled infection, turn increasingly to the medical profession for newer and more complete answers to their individual problems. Criteria for success have changed. In the Western World, a doubling of national medical expenditure may now have a zero or marginal effect on life expectancy. Plastic surgery is concerned with, above all, the correction and restoration of form. Political revolutionaries, as their heirs in Eastern Europe must now painfully recognise, are by no means offered “the blank sheet of infinite possibility”. This was an observation by Professor Michael Oakshott in his famous essay on political education, but is the possibility to be more of a reality for us, backed by science and encouraged by public demand? For thousands of years it must have been apparent to many that the solution for a particular defect or unsightly anomaly might be surgical, although such an intervention would never be made. The recent developments in tissue expansion are best seen in the context of the history of the specialty. Punitive rhinectomy in India was practised for so long and on so many victims, leading to so * Kay-Kilner
Prize Essay 1989
conspicuous a disfigurement that it is not surprising that a complicated and painful surgical treatment was finally developed and accepted. The idea of the forehead rhinoplasty was daring and original but it certainly did not represent the onset of a reconstructive revolution. Centuries passed before the range and number of procedures could initiate that logarithmic increase, a part of which we are now experiencing. This is because so much of medicine advances in concert and is dependent upon other sciences, as well as upon the wealth and social change derived from industry. Enrico Fermi recognised that for nuclear fission, which had always occurred, to detonate a chain reaction, the number and the density of atoms must exceed critical values. The effect was shattering and quite revolutionary. Expanding urban populations with widespread education, and the vast concentrations of trauma brought about by mechanised warfare, finally caused Plastic Surgery to emerge. The effect was less dramatic but it did mark the beginning of progressive changes in surgery, in medical attitudes and in public aspirations. The idea of the split thickness skin graft must have been the most valuable single innovation in surgical reconstruction. Dependant upon anaesthesia, special instruments and new skills, this procedure has gained increasing application during the last 100 years. Severe problems of scar contracture in the face and neck, large fistulae, exposed bone and the advent of radiotherapy demanded the transfer of distant soft tissue flaps. For over half a century after the Great War, the multi-staged tubed pedicle flap provided a solution for most of these cases. The skilled handling of this randomly vascularised and revascularised tissue became synonymous with the new specialty of Plastic Surgery. The limitations of the tubed pedicle technique were the inappropriate skin quality in the face and scalp and the long time for completion-six months for an exposed tibia and more
344
TISSUE EXPANSION:
A RECONSTRUCTIVE
REVOLUTION
OR A CORNUCOPIA
than twelve for a facial reconstruction. The great complication was tissue necrosis following a delay, a transfer or a revision. Before the first murmur of clinical audit, complications received much less attention than did successful results, but it does seem that even the most experienced surgeons were unable to preserve more than 80% of their flaps to completion and, overall, probably 50% were lost. This may well have represented a uniquely expensive surgical complication rate in spite of the wide acclaim for the method. In the 1960s and 70s the definition of cutaneous vascular territories brought the many named axial flaps with or without fascia, muscle and other tissues. These can be raised to considerable length in one stage and the narrow pedicles allow a wide arc of transposition. They can be used for emergency repairs and when raised under ideal conditions, a failure or major complication rate of less than 1% can be attained. This is comparable with a range of clean elective surgical operations. Most axial flaps can be transferred to more distant sites by a microvascular restoration of the circulation. Initially high failure rates are still being reduced and a figure below 10% may now be attained from a large free flap series. Tissue necrosis does, of course, mean complete loss of the flap although the cost of this is limited by the relatively short time course. The rapid and reliable repair of most defects in most patients had become possible but with so many results the external appearance remained a disappointment. Something new and different would be required: De Bono’s lateral thought concept. Since the earliest times, surgeons have had the opportunity to observe the growth in various regions and structures of the body induced by local forces. The enlargement of a breast from 100 grams to 2000 grams involves a considerable increase in skin surface area but the skin and its blood supply might be regarded as a part of the enlarging gland. In contrast, a giant cyst or a long neglected benign tumour can progressively distend overlying skin without contributing to the circulation. The surgeon in search of flaps from sites where none were hitherto available might have gained an idea for the solution. A further clue came from the ancient ritual practices of earlobe and lip stretching and from neck lengthening. These involve the even application of pressure from external appliances. In the 1950s serial filling of a subcutaneous balloon had been used to increase skin surface area, preparing a space for the cartilage grafts of an ear
OF COMPLICATIONS?
345
reconstruction. Just as revascularised organ allografts and even the reconstructive use of transplanted jejunum had long preceded the clinical application of the free flap, so it was that the tissue expander only slowly came into use in the 197Osmainly for post-mastectomy breast reconstruction-gaining more general acceptance and application in the 1980s. The widespread use of large permanent silicone implants for augmentation mammoplasty certainly gave plastic surgeons the confidence to insert tissue expanders. Similarly, the manufacture of reliable silicone rubber shells by the process of dipping mandrils took place in the existing breast implant factories. Self-sealing membranes have a long industrial history and subcutaneous injection portals had been developed to a high standard for safe long-term central venous access in the 1970s. The possibility was a reality but the concept of growth induction was as completely novel for the plastic surgeons of the 1980s as had been the free flaps and the split skin grafts in earlier times. The potential for further advances in reconstruction was equally great but acceptance by any individual surgeon was becoming dependant upon the costbenefit ratio in that practice. Part of the cost is the price of the apparatus, which may be prohibitive in the less industrialised countries. Most of the rest is time. In all but certain breast operations, two surgical procedures are required. Between them, up to twenty sterile saline injections must be administered. If the injections are made by the specialist, as an outpatient procedure, good control can be maintained and the earliest sign of any complication can be detected. Alternatively, strict training in sterile technique and in recognition of problems, together with a pressure-limiting infusion set, can allow filling of the expanders by the patients at home, with cost saving but, hopefully, no great increase in complications. Major complications may be defined as those which abort the expansion and prevent the intended outcome. Minor complications are those which require treatment, may slow down the programme and incur expense but do not affect the final result. In addition, there are the complications of general or regional anaesthesia, common to other surgical procedures. These can be considered separately. A high complication rate is a major consideration in cost-benefit analysis. For every procedure there is a learning curve. For some surgeons this means good results from the outset but a progressive reduction in time requirement. For others it means an initially
346 high failure rate which can sometimes result in early abandonment of the technique. For those who persist, costs can be reduced by increasing procedural efficiency and by recognising and eliminating those factors which cause complications, The other side of the equation is benefit. If this is defined as a simple goal such as the elimination of a large benign skin lesion and covering the defect, then most existing reconstructive procedures defeat tissue expansion in a simple cost-benefit comparison. Expanders are usually employed when the highest standard of durable or aesthetic result is required and, in these circumstances, there may be no alternative with which to compare. There are several properties which make the expanded flap unique. For a repair of good appearance the most relevant skin flap is likely to be derived from adjacent tissue. This is particularly true in the face and neck but, most of all, in the scalp. The surface area of the donor skin can be reliably doubled but, with greater risk of problems, it can be tripled. In the face and neck, expanders are best inserted in the plane superficial to the frontalis/SMAS/platysma plane so that large, thin resurfacing flaps are generated without disturbing the muscles of facial animation. After an area expansion of over 100x, marked telangiectasia is seen as the flap thickness declines to about 3 mm. With such thinning of fat and with a circulation passing only in the plane of the flap it is not surprising that dermal blood vessels become conspicuous. Telangiectasia is not a complication because it regresses after flap transfer when the deep circulation, perpendicular to the skin, is restored. Since striae are not a recognised problem in the neck and face, the final appearance of these greatly expanded skin flaps is remarkably normal. They do not carry intact peripheral nerve branches with them but, like full thickness skin grafts, they reinnervate from the recipient facial sensory nerves over one to two years. In the scalp, the most important consideration is hair density since the major operative indication is the restoration of natural-appearing, even hair cover. When 50% of the scalp has been lost, expansion of the remainder, together with some elevation of the lateral and neck hairlines, can just provide an adequate appearance when hair shaft diameters are great and follicle densities high. At the same time, expanded scalp flaps will provide a strong, mobile, independently vascularised continuation of the frontalis/galea/ occipitalis system. The incorporation of a sensory nerve, which lengthens with expansion, allows the
BRITISH JOURNAL
OF PLASTIC SURGERY
scalp flap to provide protective sensation over the cranium. When a local flap has been transposed, the scar extends only around three sides of the flap and some way into the donor area. When a simple advancement has been possible, the final scar is but a single line. Sufficient expansion prior to flap transfer facilitates closure without any tension and this contributes to the narrowest scars. When these aspects of reconstruction by tissue expansion have been considered, there may be no equally satisfactory alternative. The cost can only be balanced against utility: the product of the improvement in the quality of life and the expectancy in years. This is the justification for an elaborate means of providing the best result in a young patient. When the decision has been made to use expansion, the considerations are those of planning how to obtain this optimum result with the lowest cost in time and complications. Tissue expander systems can leak, but the frequency and extent of this is entirely a function of design, manufacture and subsequent handling. Sterile isotonic saline is universally used as the hydraulic fluid so that a small leakage represents only a minor or insignificant complication. Such small leaks occur from the filling portals, several makes of which were not designed according to self-sealing principles. For minimising losses, they depend upon the use of needles finer than 22 gauge and avoidance of tearing at the injection site. At the time of the first injection, some serum will surround the whole system and this may run out of the injection site after the needle has been withdrawn. It can be confused with a system leak unless a coloured dye has been introduced into the expander. Inadvertent puncture of the tubing or of the expander shell-the latter especially when the filling portal is integral rather than remote-always necessitates reoperation and replacement of all or a part of the system. Silicone tubing will often tear when stretched after its surface has been scored by instruments. The poorer expanders, designed without stress testing, may fracture as a result of the fatigue imposed by constant motion. The sites of weakness can be predicted and are most often adjacent to areas of excess rigidity, such as backing plates, thick joins of tubing to shell and excessive thickness of the tube wall. Connectors within the tubing or between the tube and the portal provide valuable versatility in portal placement and limitation of dissection but they do represent another source of failure. The connectors may be incapable
TISSUE EXPANSION:
A RECONSTRUCTIVE
REVOLUTION
OR A CORNUCOPIA
of withstanding tension or pressure, but they are also potential sites for tube damage. Tube occlusion through kinking occurs when the internal diameter is too great, but narrow tubes are easily blocked by any particles such as arise from the accidental introduction of blood. Much consideration has been given to the location and closure of the wound used for the insertion of the device. Remotely placed radial incisions are certainly not stressed by the filling of the expander but such a design will usually result in a blind dissection and an unnecessary additional scar. A more convenient incision line is along one of the edges of the proposed flap so that the scar will be subsequently incorporated. This closure will be near to or even overlying the edge of the expander shell, but wound breakdown can be reduced well below the 5% level. Closure requires suture in two distinct layers with a fine absorbable synthetic material, removal of any skin sutures-if used-within 5 days, before sinuses can form, and limitation of the filling pressure. Such an expander can be first filled after only 7 days, for at a pressure of only 20 mm mercury there is no danger of breakdown. From porcine experiments we know how progressive stressing of the wound results in the highest tensile strength. As with all the earlier generations of reconstructive flaps, the start of a major complication in flap expansion or transfer is likely to be a zone of necrosis. Critical ischaemia and aseptic infarction in a decubitus ulcer usually starts in proximity to the bony prominence, with only secondary skin breakdown. It seems that the same process can take place over a tissue expander. Perfusion declines rapidly at pressures above the local aterial diastolic and ceases above systolic, but transcutaneous oxygen tensions fall steadily with increasing pressure from low levels. Blanching of the skin indicates full thickness zero perfusion in that area, but for the thick flap one must merely assume deep ischaemia in the capsule and adjacent tissue when the pressure is excessive. Folding or knuckling of the silicone shell beneath a thin flap can result in local pressure necrosis. The solution lies in early recognition, external manipulation, overinflating, deflating and reinflating or occasionally in open repositioning. A rigid backing plate on a convex surface, such as the cranium, is likely to result in local pressure damage. The junction between tube and shell should be on the deep surface of the expander shell, although one can imagine the same damage occurring to underlying structures. The
OF COMPLICATIONS?
347
juvenile cranium tends to flatten in response to scalp expansion but after flap transfer, convexity is restored. In contrast, the depressed ribs resulting from subpectoral expansion in breast reconstruction are maintained and even worsened by the subsequent use of a prosthesis. An ill-placed injection portal can result in skin breakdown over the dome. Sites overlying bone, especially the mastoid, are notorious. Flap necrosis, unrelated to pressure, is a function of flap design. During initial insertion, safe limits of skin or fascial undermining must be observed. The expander produces a continued delay effect. Advancement flaps are therefore reliable, but transposition flaps must have anatomy which would result in survival had no more than a deep delay been carried out, although the flap length can be greater but only in proportion to the linear expansion ratio. In many parts of the body the most valuable and dramatically effective flaps may be intrinsically unsafe transpositions of giant skin flaps, very thin and with only random circulation. These can be made safer by delay procedures at the end of the expansion process, dividing skin and subdermal vessels along the transposition incision lines but leaving the intact capsule. Previously irradiated or scarred soft tissue has reduced elasticity and reduced growth potential. When expanded flaps are attempted in these areas, ischaemia and breakdown are so common as to transform complication statistics and to incur excessive costs. It may be safer and more effective to pre-expand a reliable free flap donor site and then to transfer this tissue to undamaged blood vessels adjacent to the scarred recipient site. When it occurs, sepsis very often turns out to be a major complication causing failure of the planned treatment, yet, with due care, the infection rate following insertion of a silicone expander should be no greater than that following a breast implant or a hip prosthesis. The aim should be a sepsis rate of less than 0.5%. The factors contributing to infection can be identified and avoided. Open wounds, ulcers or abrasions near to the expander risk lymph-borne bacterial invasion, and sepsis in other parts of the body makes for a risk of haematogenous spread to a vulnerable site where a large foreign body is in contact with relative tissue hypoxia. Dissection and haemostasis under direct vision, followed by vacuum drainage, will minimise haematoma, and the balancing of intraluminal pressure against interstitial colloid osmotic pressure avoids subsequent seroma. Deep zones of pressure necrosis, not manifesting as flap breakdown, may nonetheless
348 form the focus for sepsis. The stitch abscess, which in many operations is a nuisance, is likely in these cases to be the start of a major complication. There are other less frequent but avoidable problems which do necessitate reoperation. Too slow an initiation and rate of expansion can result in early contraction of a thickening fibrous capsule. Ill-placement of a portal can result in its rotation and loss of access. Both require surgical revision. Effects on peripheral nerves are inevitable consequences of tissue expansion. The intention may be specifically to lengthen a major nerve such as the median in the forearm or it may be to lengthen an innervated flap such as in the scalp or forearm. In other cases, nerves in the vicinity of the expander are incidentally tensioned or compressed by the applied pressure. In the early stages of expansion a nerve with good conduction can cause pain when subjected toonly 40 mm mercury and so the pressure must be further reduced. Pain need not be an obligatory symptom of expansion. Later these middle range pressures cause some loss of conduction through neurapraxia and there is less discomfort. Lengthened nerves can certainly regain conduction and so it is likely that axonotmesis only results from excess pressure-even when temporary and localised. Suckled by the plentiful horn of Amalthea, young Zeus grew to be an omnipotent deity. The mythical cornucopia was a portent of the late twentieth century products of applied science. A little of that succour is available to all in the industrialised world. When complication rates are high and misfortune plentiful, the cornucopia is the satyrical horn of
BRITISH JOURNAL
OF PLASTIC SURGERY
cuckoldry and the hapless patient is made the cuckold of the clinically errant surgeon, Although high tissue expansion failure rates in the order of 3040% have been reported, we now know that with some of the precautions, briefly alluded to above, the major complication rate can be held below 5% and total complications below 10% during large series of complex reconstructions. This is compatible with the acceptance of a successful technique in plastic surgery, and can ensure the all-important low ratio of cost-utility. With such minimised inpatient stay and constrained costs, further development may continue. If plastic surgery is undergoing revolution then that is only as- a part of the medical revolution which is itself so dependent upon social, industrial and scientific change. Tissue expansion techniques in their present form must now be seen as part of the evolving medical applications of morphogenetic induction and can hardly be excluded from that minor revolution. There is simultaneously a philosophical change. Now, for the first time in history we can present our patients and, through politics, the electorate in general with a great range of treatment options. In the individual case and for large groups taken together, benefits must now be balanced against cost. The potential for quantity and quality of supply is great. Tissue expansion has helped to make reconstructive work into the true surgical cornucopia. The Author Michael R. Maser, Surgery, Odstock
FRCS, MRCP, Senior Registrar Hospital, Salisbury, Wiltshire.
in Plastic