POSTGRAD. MED. J. (I964), 40, 266

SKIN COVERJ. N. BARRON, F.R.C.S.(ED.)

Plastic Surgeon, Odstock Hospital, Salisbury

Functional AnatomyTHE skin of the hand is a beautiful example of theadaptation of a structure to the functions which itcarries out. It is of course an integument in whichthe complex hand mechanisms are contained, butit is elaborated in various ways to allow the manyhand activities to take place. The volar skin isthick and relatively inelastic, bending occurringonly at well defined sites, the flexion creases, whichare seen in the palm and fingers. This volar skinis thick because it is protective and must withstandthe constant trauma of daily life. The texture ofthe volar skin produces a 'high hysteresis' effectand the grasp is very much enhanced by the fingerand palm print patterns.The dorsal skin is thinner, more mobile and

elastic. It contains hair follicles and is paved by acomplex system of creases which allows movementin all directions. Apart from its protective qualities,hand skin has another important attribute, that ofsensation. The sense of touch is the eye of theblind man and a study of peripheral nerve injurieshighlights the importance of this function.

Tactile stimuli are usually appreciated throughthe pulps of the fingers and of these the thumb,index and middle pulps are the most important.Temperature is generally appreciated more easilythrough the dorsal skin where rapid transmissionof thermal stimuli is possible. The subcutaneoustissues also play an important part in hand functionand their structure is related to the tasks they arecalled upon to carry out. The shape and consist-ency of the pulp substance is important as it ispart of an accurate prehensile mechanism, anddisturbance of its anatomy can produce seriousdisability.

Similarly the attachment of the volar skin tothe fingers by its various ligaments helps tostabilize the grip and in the palm the attachmentsto the palmar fascia are there for the same reason.

It will be seen that hand skin is responsible forvery important functions which in themselves arehighly specialized, and it is evident therefore thatthe surgery of this tissue should, as always, bebased on a full appreciation of its physiology.Pathology of Injury

Mechanical trauma applied to the hand can be

in the form either of crush or of cut, or a mixtureof the two. In hand surgery it is important toassess with accuracy the nature of the injury, asthis will often give a clue as to the subsequentbehaviour of the wound and of the surroundingtissues. A laceration made with a sharp instrumentwill heal more readily than a similar wound createdby a crushing agency. Cellular damage is confinedto the wound surface and there is minimal tissuedisturbance. A crush injury inflicts more wide-spread damage, progressive tissue breakdown,thrombosis and oedema. From this train of eventsrecovery is inevitably slow.Any estimate of the extent of primary surgery in

hand injuries will depend upon an accurate know-ledge of the cause. The greater amount of crush,the smaller the scope for reconstructive procedures,whereas a clean-cut wound can be a favourable sitefor primary tendon and nerve, muscle and jointcapsule repair. Skin injuries can be classified asthose without skin loss and those with skin loss.

Injuries Without Skin LossA cardinal rule in hand surgery is that no wound

should be allowed to remain open for longer thanis absolutely necessary. This means that clean-cut lacerations should be closed by primary suture.If there is associated crush, loose suturing or awound pack and elevation may be indicated untilthe tissue reaction has subsided. Lacerationsproducing partial avulsion of skin flaps should beregarded with suspicion especially if the skin flapsare distally based. If the crush element is small,skin suture is justifiable, but necrosis should bewatched for in the ensuing days. If flap avulsionis part of a crush injury, careful examination ofthe displaced tissue will probably show thatthrombosis already exists and the flap can eitherbe converted into the Wolfe graft by excision ofall the subcutaneous tissues or it can be excisedin toto and the defect covered with a free skingraft. It is better thus than to risk necrosis andinfection (Figs. I and 2).

Preparation of wound edges need not beradical. Frayed tissues should be excised, butformal wound excision is unnecessary in the hand.Suturing should be done with great accuracy asfree skin movement is a feature of hand function.

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May I964 BARRON: Skin Cover 267

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FIG. i.-Avulsion injury with distally based skin flaps.

Injuries With Skin LossThese cases can be grouped into those with

skin loss only, and those in which there is skin andsubcutaneous tissue loss. Furthermore it isimportant to realize that there are differentqualities of skin and of subcutaneous tissue. Therule concerning rapid wound closure should beadhered to and therefore one of the graftingtechniques will often be required. The bestrepairs are obtained by replacing lost tissues withsimilar tissues, and from these considerationsderive the surgical procedures in current use forthe management of this type of injury.

Skin Grafts in Hand SurgeryWhen skin is tansplanted as a single tissue, the

technique used is that of free grafting. Skin andsubcutaneous tissue together will not survive as afree graft and must therefore be transplanted on avascular pedicle.

Free GraftsThe indication for a free graft is a skin loss

injury with intact subcutaneous tissue. There arefour types of free skin grafts: the Wolfe (fullthickness) graft, thick split-skin graft, thin split-skin graft and the pinch graft. The thicker graftsare used in the repair of volar surfaces and thethinner grafts in the dorsum. Donor sites com-monly used for Wolfe grafts are antecubital fossa,upper arm and postauricular areas. Larger graftsare cut from the chest or abdomen. The thicksplit-skin graft is usually cut with a dermatomefrom the thigh or abdomen and is used for re-surfacing large areas. The thin split-skin graft(Thiersch graft) is the most viable of the freegrafts and can therefore be used under moreadverse circumstances. It is used for instance forresurfacing burns, and when healing is complete itcan be exchanged for a thicker and more durable

1.

FIG. 2.-Severe crush injury of the hand.

skin cover. Emergency cover of avulsion injuriesis often best obtained with a Thiersch graftbecause of the importance of early healing. If itbecomes unsatisfactory because of contracture orof indifferent texture it can always be replaced asan elective procedure. It is noteworthy that thinsplit-skin grafts can be made to 'take' over limitedareas of exposed tendon and on open finger joints.They form therefore a useful manceuvre in thefield of emergency reconstructive surgery andoften a simple procedure of this sort can eliminatethe necessity for amputation. The pinch graft,now mainly outmoded, has an application in handsurgery. It is convenient to use in treating asuperficial finger tip skin loss where the pulpsubstance is intact.

Technical ConsiderationsThe essential feature of any free grafting tech-

nique is immobilization of the skin to the woundsurface. This is attained by suturing the graftmargins around the wound edge with fine material.A moulded wool dressing is then applied over

the graft and this is maintained by an outercompressive fixation such as a crepe bandage orelastoplast. Immobilization of adjacent joints maybe a necessary ingredient of the dressing and thisshould be contrived to be as simple as possible(Figs. 3, 4 and 5).Burns

This disabling injury may be caused by heat,electricity or chemicals. Heat may be applied bycontact with hot metals, with flame or withliquids, the clinical picture being different in eachcase. Electrical burns may be due to tissuecoagulation from the passage of current or maybe a direct heat effect. Chemical burns may bedue either to acid or alkali.

Diagnosis of burn depth is difficult, but often

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268 POSTGRADUATE MEDICAL JOURNAL May I964

FIG. 3.-Granulating wound ready for grafting.

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FIG. 4.-Skin graft applied. Wool mould tied securelyin place. Lastonet fixation to surrounding skin.

critically important because the removal of killedtissue must precede any repair process. The mostaccurate estimate of burn depth can be made fromthe knowledge of the burning agent and by sensorytests for touch and pinprick over the burned area.Anesthesia in burned skin indicates the likelihoodof full thickness loss. Removal of slough at theearliest moment is the rule. This means that inelectrical, chemical and hot metal contact burns,excision and grafting can be carried out in thefirst few days as the areas are localized and depthdiagnosis can be accurately made. Flame burnsand scalds are more difficult as they are usuallymore widespread and contain a mixture of degreeof burning. In these cases, however, slough removalshould be assisted surgically before the third weekand skin grafts applied either at that time or a fewdays later.When early slough removal is possible, thick

split-skin grafts can be used as the wound is free

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FIG. 5.-Final fixation of graft by means of crepebandage secured with elastoplast cross straps.

FIG. 6.-Severe burn of dorsum of hand and fingers.Mixed partial and full thickness loss. Note wide-spread cedema.

of infection, but later if the surface becomescontaminated it may be wise to use a thinner graftin order to obtain early wound cover. This thingraft can be replaced later by a more suitabletype of skin.There are two schools of thought regarding the

management of burns, one which favours occlusivedressings and the other an open regime. Onbalance, the open method has advantages whereverit can be used, because early and persistent move-ment in a position of elevation is important tomaintain function and this can be difficult if thehand is encased in a massive dressing.Minor burns and those treated on an out-

patient basis will require to be dressed andingenuity must be exercised to see that thedressings while being occlusive allow the fullestpossible range of movement (Fig. 6).

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May I964 BARRON: Skin Cover 269

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Fi:[G. 7.-A cross finger flap taken from the dorscum of anadjacent finger and sutured into a pulp defect. Twoweeks later the flap bridge is divided and the insetcompleted.

Pedicle FlapsThe indications for the use of pedicle flaps is to

be found in the injury in which there is loss ofskin and subcutaneous tissue and where vitalstructures are exposed and require a fully bufferedskin cover. The commonest of these injuries istip pulp loss with exposure of bone, tendon orjoint. Adequate pulp repair can be effected byeither the cross finger flap or the thenar flap.These names indicate that the flap is takeneither from the dorsum of an adjacent finger orfrom the thenar eminence. They are both two-stage operations carried out at an interval of twoweeks. At the first stage, a suitable flap is raisedfrom the chosen donor site and the defect repairedwith a free graft. The flap is then sutured into thedigital defect and the finger is immobilized untilit is healed. At the second stage the base of theflap is divided and its inset into the finger iscompleted (Fig. 7). Good contour, cover andsensation can be expected from either of these'procedures. Local flaps are seldom used in thehand as there is very little spare tissue available.Both the rotation and the transposition flap canbe adapted to suitable hand defects, but great careshould be exercised in their design as they are noteasy to use in practice. The 'Z' plasty is a twoflap transposition technique, of value in thecorrection of contracted scars and of webbedhands. These aie often the cause of flexion con-tracture of the fingers and are to be found afterinjury and in Dupuytren's disease.

Major Skin LossMajor losses of skin and subcutaneous tissue call

for transplants from a distance. These are nearlyalways done as elective operations on the healed

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.iii.i. .::.·:R:::'8FIG. 8.-Thoracic flap used to resurface avulsion injury

of the thumb.

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FIG. 9.-Tubed abdominal pedicle used in the recon-struction of an amputated thumb. Note thesensory skin flap dissected up from the palm toprovide sensation in the grasp area of the newstump.

hand after excision of a scar or temporary freegraft. On occasion however primary flap repairsare indicated when it is known that the effects ofthe original injury can be controlled.

Cross Arm FlapThe cross arm flap can be used to resurface

either the volar or dorsal aspect of the hand. Forvolar lesions the flap is taken from the volar aspectof the opposite forearm and for dorsal wounds thedorsal surface of the forearm is used. The twolimbs are immobilized by strapping or by plasterand the second stage is completed within two tothree weeks.

Trunk FlapsAn abdominal or thoracic flap can be used to

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POSTGRADUATE MEDICAL JOURNAL

resurface any dorsal skin loss of the hand. Thedisadvantage is that the abdominal skin is thickerand sensory return is indifferent. Dorsal deglovinginjuries are a special indication for this type ofrepair as a primary operation when exposedtendons and joints need emergency flap cover(Fig. 8).

Tubed PedicleIn reconstructive surgery, the abdominal tubed

pedicle is a method whereby large amounts of skinand subcutaneous tissue can be brought to thehand. It can be used to resurface both the volarand dorsal aspects, but the inadequate sensoryreturn limits its value in volar repair. A frequentindication for the abdominal pedicle is thumbreconstruction, but the volar pulp surface mustlater be replaced by a sensory flap in order toensure a functional result (Fig. 9).

Sensory FlapsSensory flaps are relative newcomers to hand

surgery. They are designed as transposed flapsfrom normally innervated areas to provide an areaof sensation on a volar gripping surface; they canalso be dissected as neuro-vascular island flapsin which an island of innervated skin is raised ona pedicle containing its nerve and vascular supplyand transposed by passing it under an interveningskin bridge to the site requiring re-innervation.By this method a strip of skin from the lateralaspect of the ring finger can be mobilized to thecentre of the palm on its neuro-vascular supplyand then transposed to the pulp of a denervatedthumb.

SummaryHand skin is functionally an important structure.

It is frequently injured and many surgical tech-niques are available for treatment.

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