Tendon And Nerve Injuries

When a nerve and/or tendon is injured in association with extensive loss of skin, and it is apparent at the outset that their repair or reconstruction will be required, the management of that aspect of the overall defect has generally to be subordinated to the provision of skin cover.
In order to function properly in the case of a tendon, or for axon regeneration in the case of a nerve, a covering of subcutaneous tissue as well as skin is necessary, and this carries the implication that cover by a flap will be required.

When the skin defect is being reconstructed primarily using a flap, the possibility of carrying out the tendon and/or nerve reconstruction simultaneously theoretically exists, but the decision may well depend on the degree of experience of the surgeon(s) involved. The considerations which would determine such a decision concern the degree of tissue damage and wound contamination present, and whether an adequate primary debridement is possible, whether failure to reconstruct primarily is likely to result in much poorer final function, and whether the posture which may be required of the tendon/nerve reconstruction will preclude the use of the method of providing skin cover considered otherwise appropriate.

The cautious approach is to provide primary flap cover and carry out the tendon/nerve reconstruction as a secondary procedure.
When the initial skin cover has been provided
by a free skin graft, tendon/nerve reconstruction has to await replacement of the graft by a flap. Here again the considerations are essentially the same as those involved in decision making at the acute stage, except that tissue damage and potential contamination are not part of the equation.

Tendon And Nerve Injuries

A single-stage reconstruction, with the opportunity present for preoperative planning, simultaneous tendon/nerve reconstruction may be a reasonable approach; multi-staged, it is safer to wait until the flap transfer is complete and the flap well settled before carrying out the tendon/ nerve reconstruction.
Sometimes disease or previous injury makes it
necessary to replace the overlying skin to allow surgery of bone, joint or tendon to be carried out.
A flap is then usually required, and the con-siderations involved are similar to those de-scribed for the combined skin-tendon/nerve injury.

When the plastic surgeon is asked to help in managing a problem arising from infection occurring in a bone, the bone involved is nearly always the tibia. The pathology is usually one of periodic flare-ups of chronic osteitis, with the background either an old infected fracture or the residuum of acute osteitis, the latter less frequently today with more effective control of the initial episode, possibly with the background of a sequestrum.

The problem relates either to the skin overlying the subcutaneous border of the bone and /or the bone itself.
There are several reasons why the tibia should
be the bone so often involved. Apart from being the long bone whose shaft is probably most frequently fractured, it has a larger subcutaneous surface than any of the others. Less obviously significant, but probably just as important, a much smaller area of its total surface is covered with attached muscle.

The cover provided by the extensive muscle attachments to the other long bones distances them from the surface, and eliminates to a large extent the problem of providing effective skin cover after surgery. In this they provide a sharp contrast to the problems created by the long subcutaneous surface of the tibia, particularly if the injury has involved skin damage, or there is the deep skin fixation which so often follows previous surgery in the area.

The muscles attached to a bone are also
important providers of blood supply to the cortex to which they are attached. The lower half of the tibia, the segment of the shaft most at risk from fracture, has virtually no muscles attached to it, and this leaves perfusion of the bone largely reliant on its nutrient artery.

In a comminuted fracture, bony fragments which appear on X-ray to be detached from the main tibial shaft cannot rely on the perfusion source which the presence of a muscle attachment would provide, increasing the likelihood of sequestration.
This explanation of the reasons why the
problems exist provides at the same time some clues to their solution.

At a clinical level one of the problems concerns the most effective way of replacing the scarred and deeply adherent skin overlying the tibial shaft. When chronic infection of the bone with periodic flare-ups is an additional problem, avascularity and sclerosis are added to the pattern.

The objectives then become ones of providing stable skin cover for
the subcutaneous surface, trying to add to the blood supply of the sclerotic bone, and filling any defect in the bone which may result from the activities of the orthopaedic surgeon, if he has to carry out a sequestrectomy or remove sclerotic bone.
In managing the acute combined skin-bone injury, vascularised muscle used to cover the defect and fill any gaps in bony continuity has been found to have a beneficial effect in salvaging damaged tissues, and it has proved equally useful in these subsequent problems.

The form which soft tissue replacement should
take, whether by fasciocutaneous or myocu-taneous flap, will depend on the local cir-cumstances, but it should be generous in area, and planned with enough reserve to cope with any minor infection which might arise from the bone subsequently. At which precise point the bony problem should be tackled in relation to the timing of the flap transfer is a matter for discussion with the orthopaedic surgeon but, in general, operation on the diseased bone should be undertaken only when it can be immediately and completely covered by the flap.

The extent of the typical area of pretibial scarring is likely to make the possibility of using local tissues to reconstruct the defect a remote one. The use of a distant flap is unavoidable, and the demands of time and patient comfort and convenience are strong arguments in favour of a free flap. The form it should take will depend on the details of the local problem. If skin replace-ment alone is required a fasciocutaneous flap would be adequate.

Osteitis And Infected Fractures

If surgery of the bone will be required, and particularly if there is the possibility of dead space after its completion, or surgery of sclerotic, relatively avascular bone is involved, a flap which includes muscle is likely to be pre-ferable, bringing a more effective blood supply to the site, and capable of filling dead space.
Safe use of a free flap in this context requires as
much knowledge as possible of any changes in the major vessels which may have resulted from the original injury. Caveats regarding the use of vessels which are already damaged, and the use of end-to-side rather than end-to-end anastomosis, have already been discussed in relation to the acute skin-bone injury.

In the combined injury of skin and skeleton, skin damage can vary from minimal up to extensive degloving.
Where skin loss has been minor, but closure by direct suture can only be achieved under tension, a ‘relaxation incision’ is often recommended. The idea is that by making such an incision, tension will be reduced, and skin closure will be easier. The method sounds safe enough in theory, but it is less so in practice.

A
‘relaxing’ incision really creates a bipedicled flap which moves across to allow closure of the original wound. It is a well-recognised fact that even in optimal circumstances a bipedicled flap transferred in this way is an unsafe procedure and is liable to necrose. Used in a mixed skin and skeletal injury it is even more hazardous, for soft tissue damage and degloving have so often added their quota to the local devitalisation of skin.

The presence of degloving is a virtual contraindication to its use, and even in the absence of degloving the method should be used with the greatest of care. It is likely to be safest and most effective when closure is difficult because of local swelling of the limb from oedema and haemorrhage, rather than because of skin loss. The incision itself should be straight, placed at a considerable distance from the wound, and run in the long axis of the limb.

Undermining of the skin should be avoided.
When skin loss is more extensive, the replacement methods available are free skin graft, skin or fasciocutaneous flap, muscle or myocutaneous flap, and free flap -usually used individually, occasionally in combination.
Despite the alternative reconstructive methods
available today, split skin grafting should be the first choice if the raw surface is suitable.

In determining which surfaces are suitable for grafting, the key role of the periosteum has already been stressed. Excision of avascular tissue, fixation of the fracture, conservation of periosteum, closure of joint by suture of the capsule when possible, or cover with a muscle flap to create a graftable surface -all combine to give a graft the best chance to take.

The split skin graft has the great virtue also of being able on occasion to stabilise a clinical situation at minimal cost to the patient. It gives the surgeon a breathing space, and even if the graft is unsuitable as definitive cover it is possible to replace it at leisure once the patient’s condition has become stable.
Split skin grafting can be used in conjunction with other techniques.

A muscle flap, for example, may be needed to cover the bare bone element of a composite injury, but the graft can still be applied all around the area covered by the muscle as well as providing cover for the muscle itself.
Skin and fasciocutaneous flaps, rotation or
transposed, raised locally, have little if any place in acute injuries of this sort. Although safer when they include the fascia! layer, they have not been assessed objectively in the context of acute skin-bone trauma.

Before contemplating the use of a flap of this type, it would be essential to gauge the damage to the overall vascularity of the skin which it is proposed to use as the flap, particularly when an element of degloving is
involved. In any case the size and shape of the typical defect and the state of the surrounding skin would preclude its use.

The cross-leg flap may have been increased in safety by incorporating the fascial layer, but for the surgeon with little experience in its use (and such experience is becoming rarer as the method is losing popularity in other contexts) it must be regarded as distinctly hazardous. Such flaps have also to be used with particular circumspection, even as elective procedures in older patients, because of peripheral vascular problems in the ageing limb, and problems of joint stiffness.

These considerations would apply with redoubled force in an emergency situation, especially in the lower limb where the problem really arises. In a lower limb injury a cross-leg fasciocutaneous flap can be contemplated only by an experienced operator, in the young patient with unimpaired peripheral circulation and joints capable of tolerating the immobilisation -a combination of limitations likely to restrict its usage to near zero.

Local fasciocutaneous flaps being generally unsuitable for use at the acute stage of a combined skin-bone injury, the question arises whether the skin-fascia combination is capable of recovering sufficiently to be safe to use at a later date, and if so when. It is difficult to believe that degloved skin can recover to total circulatory normality, though it has been reported as being successfully used for subsequent reconstruction, which would suggest that at least a degree of recovery can take place.

The cautious surgeon is unlikely to accept this as a blanket finding. Reasoning from other clinical contexts, such observations as the amount of superficial scarring of the skin, its degree of comparative mobility, and the thickness of the layer of superficial fascia, would all play a part in decision making.
The use of muscle and myocutaneous flaps
raised locally would be confined to defects of the knee and upper half of the anterior tibia.

The medial head of gastrocnerhius is capable of covering the medial aspect of the knee joint and the upper third of the tibia.
Transfer is probably better carried out as a
muscle flap rather than as a myocutaneous flap when the option is present. Even used in late reconstruction the virtues of a muscle flap with grafting of its exposed surface, as compared with grafting of the secondary defect left by the transfer of the corresponding myocutaneous flap, have been recognised.

The potential hazard of the presence of muscle damage in assessing its usage in muscle transfer has already been discussed, and its unexpected tolerance of transfer as a flap even when showing signs of injury.
Where the necessary facilities and micro-vascular expertise have been available, free flaps, (fasciocutaneous, muscle and myocutane-ous), have been increasingly used in managing the more severe mixed injuries of skin and bone.

The techniques involved may be demanding, but the results, judged in terms of healing time, time to fracture union and time in hospital, are all better. Muscle, transferred as a flap, appears also to bring with it a degree of vascularity which, used to cover a surface which shows damage, prevents the damage progressing to necrosis, and it seems to retain these virtues even when it is part of a free flap.

Provisionof Skin Cover

In a situation where periosteal stripping and continuing exposure of bare cortical bone is so often followed by sequestration of its outer layer, this is a particularly valuable attribute. The muscle is also able to fill any bony defect which may have resulted from the removal of comminuted bony fragments judged to be avascular, and in this way eliminate dead space.
A free flap frequently used is the latissimus
dorsi flap.

Its long pedicle and reliable vessels of a good calibre make it among the less technically demanding transfers. The large area of muscle which can be transferred also makes it possible to cope with the more extensive defects successfully so that, even if part of the area of skin loss is graftable, it may still be convenient to cover the entire area with the flap. The rectus abdominis flap has become a popular, and equally suitable, alternative.

Both flaps tend to be used as muscle rather than as myocutaneous flaps, leaving skin cover to be provided by grafting.
For the smaller defect, alternatives are the radial forearm, the lateral upper arm flap and the
scapular flap. The comparative virtues of the three are discussed in Chapter 4.

The vessels at the fracture site chosen for anastomosis will depend on the site of injury and the extent of vascular involvement. They must be examined with extreme care for signs of damage, and interpositional vein grafts may be needed if it proves necessary to reach a healthy vessel wall which can be used for anastomosis. Immediately post-traumatic, reliable criteria of total normality of the vessel wall present a problem.

Seven to 10 days later, signs of damage to vessels are more obvious, with oedema and thickening of the wall.
The state of the other main arteries of the limb may also need to be assessed to ascertain to what extent the artery chosen for anastomosis is sustaining the limb alone or with minimal assistance from the other main arteries.

The findings may preclude the use of end-to-end anastomosis to the flap artery, and even in the absence of damage to other vessels end-to-side anastomosis may be preferable. The information provided by arteriography is, as already stressed (p. 102), only partial and must be matched against the findings at operation.

Fixation of the fracture is the responsibility of the orthopaedic surgeon, but in choosing the method he has also to ensure that his choice does not conflict with the needs of the soft tissue injury. The essence of the method used is that it should provide rigid fixation of the fracture, and the potential alternatives are plaster of Paris, with or without a window, internal fixation using plate and screws, intramedullary nail fixation and external fixation frame.

 

With plaster of Paris fixation there is no access to the area of skin loss unless a large window is cut. A window of adequate size is likely to affect fixation of the fracture adversely, and on these grounds is undesirable. However, if a window is to be avoided, the skin cover used at the time of primary treatment has to be restricted to split skin grafting at the very most, and it is therefore not an option where skin damage is a significant part of the total injury.

Even without a window, plaster of Paris fixation alone may not be considered capable of providing the rigid fixation regarded as essential when the fracture
is unstable.
Internal fixation using plates and screws may be an effective method in the closed tibial fracture but in the compound fracture with skin loss its role is more open to question.

The site of skin loss nearly always overlies the subcutaneous surface of the tibia, and addition of the incisions and dissection required to expose the bone to insert an anteriorly applied plate extends the area of soft tissue damage to an undesirable degree, in the surface where the tibia is most vulnerable from the point of view of overlying skin necrosis. Application of the plate to the posterior surface is an alternative, but the posterior approach has not become standard practice in this context.

In the comminuted fracture particularly, the
method is unlikely to be the one of choice, and even in the absence of comminution it has the serious disadvantage of adding considerably to the amount of bone exposed and soft tissue dissected.
Intramedullary nail fixation might appear to have adverse factors.

It might well be felt that the exposure of the entire medullary cavity to the surface, which the insertion of such a nail entails, would invite the spread of infection from end to end of the bone. The fact that it is being successfully used, admittedly in conjunction with the provision of well-vascularised flap cover, would indicate that this fear is largely
groundless.

Viewed in relation to the provision of skin cover it has the considerable virtue that its use does not place any restraints on the method of providing skin cover selected by the plastic surgeon.
The external fixation frame also has the virtue of leaving the fracture site unimpeded from the point of view of providing skin cover.

 

The transfixion pins inserted into the bone at a distance from the fracture provide virtually absolute stability without interfering with the fracture site once the frame has been set up. The absence of interference with the soft tissues, damaged or undamaged, at or around the fracture site, allows the two components of the injury, bone and soft tissue, to be managed with minimal reference one to the other.

Almost the only aspect of the bony fixation which may affect soft tissue management is the site of insertion of the pins. This determines the line of the interconnecting bar, and thought should be given to this aspect to ensure that it does not make the reconstruction which the plastic surgeon wishes to use less easy technically, or even impossible. With this proviso, it leaves the entire range of reconstructive techniques available for use.

The fractures most often associated with skin loss involve the long bones, tibia and, much less frequently, ulna. Before the management of such an injury can usefully be discussed, it is necessary to have an understanding of the principles which underlie its treatment, for the detailed handling of the injury is the expression in practical terms of these principles.

A primary objective in treating such a combined injury is to prevent infection, and this is achieved by fixing the fracture and by providing skin cover to isolate it from the surface.
An X-ray of a fracture gives an incomplete
picture of the total injury in the way that it ignores the soft tissue element.

The severity of this latter element and the form it takes are of major importance when the soft tissues around the fracture site -muscle, fascia and skin -are being assessed for damage and even viability, or as potential sources to provide cover for the bone, fractured or merely bared by the injury.
The injury to muscle can take the form of obvious tearing of muscle fibres, but damage at a less gross level can also occur, resulting in swelling of the muscle belly.

Even so, muscle is unexpectedly resilient in practice, and has been successfully transferred in the form of a flap shortly after the original injury, though its use in this way is not without risk.
The injury to skin takes a different form, seen
most strikingly when part of the injury involves degloving of the skin and superficial fascia.

Degloving as an isolated injury has already been described, but when it is associated with bony trauma it has to be considered also in relation to the extent to which it might be possible to use degloved skin and its underlying layer of fascia as a local flap to cover the surface defect. Before the use of such skin can be considered, there would have to be clear evidence of circulation in the skin area, and even when this criterion has been fulfilled it has not proved a reliable flap source.

The various elements of a mixed skin-bone injury can vary widely in their severity, and the plastic surgeon is liable to have a biased view of the situation. He is likely to see only the injuries at the most severe end of the spectrum, and assume that they are the norm, whereas in fact the less severe injuries are being successfully managed by the orthopaedic surgeon on his own. Nonetheless, if a harmonious and effective relationship is to be built up, the plastic surgeon is best invited to see the patient at the acute stage if the orthopaedic surgeon considers that there is even a remote possibility that he may have to be involved in treatment later.

The greater trochanter is the projection which determines the site of the trochanteric ulcer. Initially, the main cavity of the ulcer is the trochanteric bursa which overlies the projection and, if this alone is involved, permanent closure may be achieved without interfering with the bone.

As the condition progresses the trochanter and neck of femur increasingly project into the cavity, and excision of trochanter and appropri-ate cortex of the shaft is required to let the soft tissues collapse and obliterate the cavity. In the most severe instances a pyoarthrosis of the hip joint may develop and, once present, this complica-tion is virtually impossible to eradicate without amputation of the limb.

The ulcer is so undermined in most cases that
free skin grafting is seldom practicable. Cover by a flap is necessary. When this takes the form of a skin flap a transposed flap is used; its precise situ-
ation and shape will depend on the size and shape of the ulcer, with the proviso always that the secondary defect should be on an area free from subsequent weightbearing.

Added safety can be provided by incorporating the iliotibial tract in the flap, in the form of a tensor fasciae latae myocutaneous flap.

The appropriate type of flap depends on the shape of the ulcer. Frequently suitable is the bilateral flap of buttock skin based on the in-ferior gluteal fold , and this double flap is especially useful in the sacral pressure sore in the non-paraplegic patient. If the shape and extent of the ulcer make this flap unsuitable, alternatives are the transposed or rotation flap using buttock skin, extending on to the lumbar region. Gluteus maximus has been incorporated into these flaps to add to their safety and effective-ness, and more recently flaps have been designed to use the gluteus maximus muscle in a more formal way.

 

Each muscle, together with a triangle of the overlying buttock skin, is detached from its sacral insertion and mobilised, preserving the inferior gluteal nerve and the gluteal vessels, and advanced to meet its fellow in the midline to reconstruct the postexcisional defect of the sacral ulcer, providing skin cover along with an underlying pad of muscle.
In using the glutei in this way there are several considerations which need to be taken into account, and which are not immediately appar-ent.

One concerns the fact that gluteus maximus is not an expendable muscle, and if the transfer will result in denervation it can only be used in the paraplegic patient. The advancement myocu-taneous flap as described should retain the nerve supply and can thus be used in the non-para-plegic. The entire area is also extremely vascular, and dissection involving gluteus maximus, indeed dissection generally in this area, both in the paraplegic and non-paraplegic patient, involves considerable blood loss.

Several techniques have been developed which do not fit readily into a neat classification, either because they are not strictly surgical, though they are used in a surgical context, or have been taken from other surgical disciplines because they offered a partial or complete solution to problems whose management by conventional plastic surgical methods was unsatisfactory.

 

TISSUE EXPANSIONIn this technique, a silastic ‘bag’, not unlike an uninflated balloon, is placed under the skin and superficial fascia, and inflated at intervals by the injection of saline under pressure. The saline is not injected directly into the ‘bag’, but into a small non-expansile reservoir placed at a distance from it, and connected to it by a fine bore tube.

Additional Techniques

In this technique, a silastic ‘bag’, not unlike an uninflated balloon, is placed under the skin and superficial fascia, and inflated at intervals by the injection of saline under pressure. The saline is not injected directly into the ‘bag’, but into a small non-expansile reservoir placed at a distance from it, and connected to it by a fine bore tube.

The effect of the inflation is to produce an increasing bulge of the overlying tissue, and in so doing stretch the skin. In this way the skin is ‘expanded’, increased in area, and made available for reconstruction. Expansion is exploited clinically in two ways.

In one, as used in postmastectomy breast recon-struction, the expanded skin and the underlying cavity are both utilised: the cavity for permanent insertion of a silicone implant to recreate the breast mound, the expanded skin to provide an envelope for the implant. . The other way in which the principle is used is in the creation of an area of skin availability which, sited alongside a defect, allows it to be closed directly.

The expanded area may be created beforehand, so that, when the defect is created, the expanded skin is already available to close it. Alternatively, it may be used to replace a skin graft, previously applied to cover the defect.

The skin adjoining a defect is generally re-cognised to give the best result in reconstructing it, because they have similar characteristics, and this is a major virtue of the method, one which shows most strikingly when it is used to extend hair-bearing scalp in replacing an area of alopecia. Various shapes of expanders are used -round, oval and crescentic -with different sizes, depending on the amount of expansion desired.

A skin incision is made, just long enough to allow the expander to be inserted without bending, and the pocket to accommodate it is dissected, generally at the deep level of the superficial fascia. A pocket is also made for the reservoir at a distance from the expander. 121 The reservoir is sometimes positioned externally, making injection easier as well as painless, though it probably increases the risk of infection reaching the expander.

A small volume of saline is injected immediately to smooth out the envelope of the expander, the incisions are closed, and the wounds left for 1-2 weeks to heal. Expansion is then begun, and repeated usually at weekly intervals. Whitening of the skin, indicative of local ischaemia, or a complaint of pain by the patient, are signs that expansion has gone far enough for the time being.

Over the period of the expansion, a degree of capsule formation usually builds up and, depending on its severity, it is left, scored or excised. The technique has its strong advocates, but overall it has not achieved the popularity which seemed likely when it was first introduced. Adverse factors concern the time taken to achieve adequate expansion, 6-12 weeks, and the increasingly bizarre appearance of the patient as expansion proceeds.

Even when circumstances are ideal, the complication rate is considerable, mainly the result of infection, haematoma or extrusion, and the nature of the technique means that any complication requires removal of the expander and spells failure of the method. The other substantial problem is that of designing the expansion, which involves three dimensions, to provide cover for a defect which, the breast and scalp apart, is usually two-dimensional. The most effective applications of the method have been where the surface is convex with a bony base, as in the scalp and forehead, and in breast reconstruction.

The flap, designed astride the intermuscular septum, is raised under tourniquet. Its breadth is limited to 6cm because of the need to close the secondary defect directly; its average length is 10 cm. As a first step, the line joining the lateral epicondyle and the deltoid insertion, representing the line of the intermuscular septum, is marked out on the skin.

Behind this line the flap contains no structures of note, and this makes it convenient to raise this seg-ment first, and establish the plane between the investing layer of fascia and triceps at the outset, dissecting forward until the lateral intermuscular septum is reached. The muscle fibres can then be separated from the septum over its full depth and over the length of the flap, exposing the vessels and the nerves in the septum.

The skin incision is extended proximally to just behind the posterior border of deltoid, and this allows the vessels and nerves to be dissected out proximally, separated from the radial nerve, and traced back into the spiral groove. In carry-ing out this dissection triceps and deltoid are separated, and any fibres of triceps attached to the septum which are obscuring the groove are divided.

 

With the vascular pedicle defined, the flap anterior to the septum can be freed from brachialis and brachioradialis, and its elevation completed. Throughout the dissection numerous small branches of the perfusing vessels supply-ing the surrounding muscles have to be divided.
When the transfer is as an osteofasciocutan-
eous flap, a strip of muscle is left attached to each side of the septum.

These strips, carried down to the bone over the length to be raised, provide protection for the vessels in the septum which are perfusing the two elements of the composite transfer, skin and bone. As a prelimin-ary to this part of the dissection the radial nerve should be retracted out of the way. A 1 cm broad, and up to 10 cm long, strip of the humeral shaft can be raised without compromising the strength of the bone. Clinical usage

The skin element is thin and the underlying layer of fat is generally thin, the combination making for a flexible flap. The scar which represents the sec-ondary defect, though in a site which may regularly be exposed, is not unduly obtrusive. The small-ness of the diameters of its perfusing vessels is its major drawback, the trend generally being towards flaps with larger perfusing vessel diameters.

The perforating system of the ulnar forearm flap passes from the ulnar vessels to the investing layer of fascia in the septum between flexor carpi ulnaris and flexor digitorum superficialis. The flap is generally sited towards the ulnar side of the forearm, but in other respects the techniques involved in its transfer are similar to those of the radial forearm flap in its fasciocutan-eous form.

 

The two flaps have a largely similar range of potential usage, but the radial form is more often used in clinical practice.

 

 LATERALUPPER ARM FLAP

This fasciocutaneous flap is raised on the lateral aspect of the upper arm, just above the lateral epicondyle of the humerus, using as its vascular basis the posterior branch of the radial collateral artery and its venae comitantes. It can also be transferred as an osteofasciocutaneous flap by including a segment of the underlying humeral shaft. The parent vessel of the perfusion system is the profunda brachii artery.

 

This vessel runs alongside the radial nerve, deep to triceps, in the spiral groove, and reaches the lateral intermus-cular septum between triceps and the insertion of deltoid. There it divides into two branches, anterior and posterior. The anterior branch, small and not always present, accompanies the radial nerve as it passes distally in the groove between brachialis and brachioradialis.

The posterior branch, with an external diameter of 1.5-2 mm, is consistently present, with associated venae comitantes, running distally in the intermuscular septum between triceps and the brachialis-brachioradialis muscle group. In the intermuscular septum it gives off branches which reach the investing layer of deep fascia and the overlying skin.

Additional multiple small vessels pass from it into the surrounding muscles, and also reach the humeral periosteum to which the intermuscular septum is attached. The lower lateral cutaneous nerve of the arm supplies sensation to the skin area and is aviable for suture in the recipient area if a sensate flap is desired. Division of the nerve, and of the posterior cutaneous nerve of the fore-arm which arises in common with it, leaves an anaesthetic area distal to the flap site.