12.8 Soft tissue coverage

Soft tissue coverage of the extremities following trauma facilitates early wound healing and provides durable cover for exposed structures. Defects have traditionally been closed by using the simplest suitable technique from a reconstructive ladder, ranging from primary closure and skin grafting to flap cover. However, the expanded armamentarium available to the reconstructive surgeon permits the emphasis to shift from simply closing the wound to one providing an optimal functional and aesthetic result.

Outcomes are judged by the extent of restoration of form and function, and also by the donor site morbidity of the reconstruction. Losses should ideally be replaced with like tissue and cover should provide durable protection for underlying structures with minimal donor site morbidity. Attempts should be made to restore sensibility where possible as functional results will be enhanced. This chapter discusses options for soft tissue cover in the upper and lower extremities. Hand and wrist cover are discussed in a separate chapter.

The approach to assessment and reconstruction of a surgical defect is similar in both extremities. The history should include an estimate of the forces causing the injury. The presence of peripheral vascular disease, diabetes mellitus, or a history of heavy smoking may influence the choice of reconstruction and are considered with age, sex, occupation, and pre-injury mobility status.

The limb assessment starts with the general trauma evaluation and continues in the operating theatre during initial debridement. High velocity, severe crush, or degloving injuries have extended zones of damage which are often unrecognized on initial inspection but should be suspected as soon as the details of the accident are known. The limb examination should pay particular attention to the vascular supply, skeletal integrity, and the presence or absence of nerve injury. The wound is examined to determine the extent of soft tissue loss, absence of other structures, and degree of exposure of vulnerable tissues (bone, tendon, nerve, cartilage, and vessels). The quality and availability of adjacent tissue is evaluated for possible use in local flap transfer. Avulsion or degloving mechanisms will further widen the affected area. Marginal tissues may not declare viability at the initial exploration and serial debridements are necessary until the wound is stable.

Investigations such as angiography should be requested if indicated, especially if free tissue transfer is being contemplated. Indications for preoperative angiography include patients with suspected vascular injury who may require acute vascular reconstruction (Gustilo 3C tibial fractures) and patients who have had previous regional surgery with possible alteration of recipient vessel anatomy.

A multidisciplinary approach is commonly necessary for the management of these patients, especially in the lower limb where complex fracture fixation procedures are undertaken prior to soft tissue coverage and early participation of all parties who will be involved in management should be encouraged.

The foremost principle in the management of any traumatic injury is early, meticulous surgical debridement and wound irrigation. In complex injuries, particularly with heavy contamination, serial debridement may be performed after 48–72h in order to determine more accurately the extent of tissue damage. Conservative initial debridement in wounds with massive tissue loss allows for preservation of tissue which may otherwise be excised using a more radical approach. At the second debridement any obvious residual devitalized tissue can be excised. The wound should then be suitable for cover which can be undertaken at this stage. Alternatively, if free tissue transfer is proposed as a single-stage procedure, it is essential that all devitalized tissues are excised prior to coverage.

The bacterial count in the wound increases with time prior to surgery and intravenous antibiotic therapy is therefore commenced on admission and continued until soft tissue cover is achieved. Wound swabs should be taken intraoperatively and antibiotics adjusted according to bacterial sensitivities.

Where skin loss is minimal, wounds can be closed by primary suture following debridement and irrigation under appropriate antibiotic cover. During suturing the margins of the wound should be easily opposed without blanching and allowances made for postoperative swelling to avoid ischaemic skin necrosis (approximate—don’t strangulate!). Wounds should not be closed primarily if under tension. If in doubt, sutures should be removed and another method of cover sought. In practice, most wounds can be closed either primarily or with a split skin graft.

Wounds that cannot be closed primarily can generally be closed by applying skin grafts or with flap cover. Skin grafts are also indicated in wounds where grafting would expedite healing in contrast to healing by secondary intention, and also where no advantage can be obtained by using a skin flap. The wound bed should be well vascularized and free from infection, which in practical terms means a wound bed consisting of healthy muscle, fascia, or granulation tissue. The presence of beta-haemolytic streptococci (Lancefield group A) is an absolute contraindication to grafting. Graft will not take on exposed bone, cartilage, or tendon unless the periosteum, perichondrium, or paratenon are intact. Absence of these well vascularized structures, or exposure of nerves or vessels, excludes the use of a skin graft and necessitates flap cover.

Flap cover may be from a local or regional source, or as a free tissue transfer. Flap transfer may be fascial, fasciocutaneous, muscle, or composites depending on the reconstructive requirements. Local random pattern flaps can be transposed, advanced, or rotated to cover small defects where the bed is unsuitable for a skin graft or where a flap would give a better cosmetic result.

The timing and choice of cover depends on the general condition of the patient including associated injuries, site, size, and depth of defect, extent of the zone of injury (macroscopic and microscopic), thickness of tissue required for reconstruction, donor site availability, and the need to perform secondary reconstructive procedures. In general, low-energy injuries unsuitable for primary closure or split skin grafting can be covered with local fasciocutaneous flaps, whereas extensive defects from high energy injuries often require free tissue transfer. Primary reconstruction of damaged tendons and nerves should only be performed if adequate cover can be provided simultaneously. Nerves and tendons that are not suitable for primary repair should be tagged following debridement and bony stabilization in order to facilitate easy identification during secondary reconstruction.

Split skin grafts are most commonly harvested from the uninvolved thigh or buttock region under general or local anaesthesia with either an electrical or air-driven dermatome or a free hand knife. The donor site is prepared and draped in a sterile fashion. An epinephrine (adrenaline) containing local anaesthetic solution may be infiltrated subcutaneously preoperatively or applied topically following harvest to reduce blood loss and provide postoperative pain relief. The dermatome is set to the appropriate thickness, the donor site lubricated with liquid paraffin, and the graft cut by setting the dermatome flat on the skin, turning on the power and advancing it across the donor site using gentle downward pressure. The harvested skin may be meshed using a mechanical device or ‘hand meshed’ using a scalpel. Meshing allows egress of exudate which could otherwise accumulate under the graft lifting it from its bed. The donor site is dressed. A number of donor site dressings are available, including semiocclusive dressing such as calcium alginate (Kaltostat) or Lyofoam. The graft is spread, cut surface upwards, on a sheet of paraffin gauze. It is then placed on the wound and fixed with sutures or tissue glue (Histacryl), and a well-padded dressing is applied. The graft is typically inspected 5 days postoperatively and the donor site inspected 10–14 days postoperatively.

Careful planning and execution are of paramount importance for successful flap transfer. Flap design begins with projection of the recipient defect backwards (via a template) onto a suitable donor site. The flap should have a predictable circulation and be larger than the primary defect, allowing for safe single-stage transfer with tension free inset. Donor sites produce a secondary defect which may be closed directly or indirectly, using either skin graft or local flaps. Principles which improve the quality of the reconstruction include: elimination of dead space; atraumatic tissue handling; meticulous haemostasis; and the use of appropriate suture materials.

Complex injuries involving fractures with varying degrees of soft tissue loss require stabilization prior to coverage. The method of fixation used depends on the fracture site and type, size and characteristics of the wound and to a certain extent the preference of the orthopaedic surgeon. External fixation conveniently splints bone and soft tissues while providing access to the wound and can be applied rapidly with minimal risk of further devascularization of bone fragments and adjacent soft tissues. Internal fixation using plates and screws or intramedullary nails may be used primarily provided soft tissue cover can be achieved simultaneously. If the surgeon performing the external fixation is different from the surgeon providing cover, it is important that placement of fixation pins is discussed to avoid compromise of potential local donor tissues.

The timing of reconstruction depends on the mechanism of injury, wound status, condition of the patient and availability of appropriate surgical expertise. Early wound closure (defined by Byrd et al. as the first 6 days from injury and by Godina as the first 72h from injury) of complex lower extremity defects with vascularized muscle following radical debridement was associated with lower wound infection rates, a lower incidence of osteomyelitis and non-union, and lower anastomotic thrombosis rates, than delayed closure. In practice, initial evaluation, debridement, and bone stabilization are performed by the orthopaedic trauma team and the plastic/reconstructive surgeon is asked to provide soft tissue cover days later, thus missing the first ‘window of opportunity’ for reconstruction.

Ideally, all severe injuries are managed on a single site with dedicated orthopaedic and plastic/microsurgical surgeons with an interest in trauma. If the appropriate expertise is not available locally, it is essential that orthopaedic surgeons communicate with their local plastic surgery service or with appropriately trained and experienced orthopaedic colleagues before embarking on the first operative procedure. In cases where cover is delayed, it is important to avoid desiccation of the wound between operations.

Topical negative pressure (TNP) wound care management systems have become increasingly popular over the last decade and their use in the management of limb trauma is continually evolving. Used in the appropriate wounds, TNP can reduce swelling and encourage the growth of granulation tissue allowing wound closure with split skin graft rather than a flap. However, used incorrectly it can delay appropriate radical debridement that may otherwise salvage early infected prostheses and metal work. In the military and acute trauma setting it can allow wound debridement and then sterile wound closure, so that appropriate transfer to a specialist centre can be achieved. Its usage should be regularly reviewed and restricted to those with appropriate training or when used in close collaboration with plastic surgery colleagues and it should not replace adequate surgical debridement.

Although numerous flaps have been described, the vast majority of defects can be covered adequately by using one of a limited number of ‘workhorse’ flaps.

The latissimus dorsi muscle free flap is the workhorse of lower limb reconstruction, whereas the pedicled latissimus dorsi muscle or musculocutaneous flaps are useful in shoulder and arm reconstruction. The muscle is easily elevated, has a long pedicle enabling microvascular anastomosis outside the zone of injury, and can be folded which aids in dead-space obliteration. Dimensions averaging 25cm × 40cm in adults provide cover for defects extending from the proximal tibia to the ankle. The amount of muscle harvested can be tailored to the defect preserving innervation and function of the remaining muscle. Among the disadvantages of muscle transfer is weakness of upper extremity ‘push-off’, an activity of importance in some athletes and bell ringers!

The serratus anterior muscle can be transferred as a free flap either alone or combined with the latissimus dorsi muscle for cover of medium to large defects in the distal third of the leg and foot. The upper slips of the muscle should be preserved during harvest in order to reduce winging of the scapula which would result from complete removal of the muscle. Although the donor site is closed directly, lack of an associated skin flap necessitates skin grafting for resurfacing.

The rectus abdominis muscle can be used as a pedicled muscle or musculocutaneous flap for coverage of both groins or as a free muscle flap for coverage of lower limb defects. The blood supply is robust, considerable muscle bulk is available and the skin paddle can be carried anywhere along the muscle. If the skin island is placed at the level of the inframammary fold, a pedicled musculocutaneous flap can provide cover of the groin, trochanter, or anterior thigh as far as the knee. Disadvantages of flap harvest include abdominal weakness that results particularly in the inferior portion of the abdomen below the arcuate line, although hernias are rare and functional morbidity is minimal as the remaining rectus muscle compensates.

The arc of rotation of the pedicled gracilis flap allows for cover of ipsilateral groin defects or defects on the anterior and posterior thigh. The gracilis can also be transferred as a free muscle or musculocutaneous flap for coverage of limb defects. A neuromuscular flap can be used to provide motor input following muscle loss, e.g. for elbow flexion. Muscle harvest causes minimal functional morbidity and the donor site can always be closed primarily. However, long cutaneous skin paddles are unreliable distally and the flap may be difficult to raise in the obese.

The scapula flap can be used to cover defects in the upper arm and axilla as a pedicled flap and defects in the forearm as a free flap. Composite flaps consisting of skin overlying the scapula, latissimus dorsi, and/or serratus anterior muscle are available for cover of large complex defects. Primary closure of the donor site is usual, although the scar over the scapula will almost always stretch leaving an unattractive donor site.

The groin flap has been popular for cover of hand and forearm defects. It is large enough for most upper extremity defects and can be extended if necessary by delay procedures. The donor site can usually be closed primarily leaving an acceptable ‘bikini-line’ scar. The distal portion can be radically thinned to fit hand defects with a more acceptable contour although it may still be bulky in obese patients. As with all staged transfers the delay between stages may lead to stiffness which is compounded by the dependent position the arm is forced to adopt. Early aggressive hand therapy or use of this flap as a free tissue transfer can reduce this problem. Utilizing either method, groin flaps may require thinning procedures to improve contour.

A large territory of forearm skin can be raised as an axial pedicle flap or as a free flap on the radial artery. Palmaris longus tendon and radial bone can be included for extensor or metacarpal reconstruction respectively if required. Composites of bone and skin can also be used for thumb reconstruction. The pedicled radial forearm flap is often used as a reversed flow distally based fasciocutaneous flap for cover of distal dorsal hand defects or degloved fingers in a mutilated hand. The vascular anatomy is constant and the excellent nerve supply allows its use as a neurovascular flap. The main disadvantages of this flap are the donor site morbidity and the sacrifice of the radial artery. The donor site may require a split skin graft for reconstruction which can be unsightly and should preferably not be used in female patients. Smaller donor sites that are still too wide for direct suture may close with a local sliding transposition flap. An Allen test should always be performed before raising this flap to confirm adequate ulnar artery vascular input to the whole hand.

The lateral arm fasciocutaneous flap can be used as a pedicled flap to cover proximal forearm defects, or as a free flap to cover small to moderate size defects in the lower limb and distal forearm. Flaps with dimensions of 15 cm × 14 cm have been described but if the donor site is to be closed primarily the width should be limited to 6–8cm. The main advantage of the lateral arm flap over the radial forearm flap is that the nutrient artery is not essential to the vascularity of the distal upper extremity.

For small to medium sized defects of the middle and distal third of the leg, turnover flaps of fat and fascia have been used as a bed for a split skin graft (Figure 12.8.2). They can be designed to incorporate a perforator in the base adjacent to the defect, and hence a more reliable blood supply. Donor sites that have been previously traumatized or degloved are unsuitable due to perforator damage and impaired vascularity. Success with these flaps requires some expertise and they should not be used for coverage of infected wounds. While muscle flaps are relatively resistant to bacterial contamination in contrast to fasciocutaneous flaps, adipofascial flaps have not been shown to have this property. Although donor site morbidity is minimal, the major disadvantage of this flap is the unpredictable take of skin grafts applied to the fascial surface.

Where nerve, blood vessels, tendon, or bone are not injured or exposed, e.g. a deep friction burn or a skin avulsion injury, a split thickness skin graft can provide excellent cover. Where grafts cross the elbow joint, splinting and physiotherapy help to prevent the development of skin contractures that may reduce the range of elbow motion. With careful surgical technique, a split skin graft will heal sufficiently to allow mobilization within one week of the procedure. Pressure garments can be worn for 6–18 months to hasten graft maturation and improve the final appearance.

In some avulsion or degloving type injuries the skin flap can be used as a full thickness skin graft following defatting providing the surface of the skin flap is relatively undamaged. This has the advantage of providing skin with a good colour and texture match without donor site morbidity. Defects that are unsuitable for skin grafting require flap cover from local or regional sites or free tissue transfer.

Significant upper limb trauma is often associated with chest injuries and definitive cover may have to be delayed until the patient’s condition is stable. Debridement with dressings or a split thickness skin graft, autogenous or autologous, can be used as a temporary biologic dressing. A pedicled latissimus dorsi flap may then be required to reconstruct defects in the shoulder and arm. Fasciocutaneous flaps such as the scapula or groin flaps may also be used to cover large forearm defects. For smaller defects, the lateral arm flap can cover defects above and below the elbow.

In more complex defects, free tissue transfer may be the method of choice for soft tissue cover. Other indications for free tissue transfers in the upper limb are as follows:

Significant lower limb trauma is often associated with other injuries and while management of life-threatening conditions takes precedence over limb injuries, decisions regarding treatment of the injured limb need not be delayed. Prerequisites for reconstruction are vascular patency and tibial nerve integrity.

The circumferential muscle layer surrounding the femur in the proximal third of the thigh allows for most defects to be closed with split thickness skin grafts. When vessels or nerves are exposed following post-traumatic vascular reconstruction or occasionally with exposure of orthopaedic metalwork, a number of local pedicled flaps are available including: rectus abdominis, tensor fascia lata, gracilis, sartorius, vastus medialis, and vastus lateralis. When suitable local tissue is not available or composite tissue is needed, free tissue transfer should be considered.

Traumatic defects or exposure of orthopaedic metalwork following wound dehiscence in this region frequently require flap cover. Choices for coverage include proximally based fasciocutaneous flaps, local muscle flaps, and free tissue transfer. The gastrocnemius muscle is the most useful source of cover in this area. Based on proximal pedicles, the medial or lateral head of this muscle can be harvested for cover of medium sized defects from the proximal patella as far caudal as the junction of the upper and middle thirds of the tibia. Functional morbidity is minimal and split skin grafting of the muscle produces good surface contour.

Defects in the middle third of the leg can be covered with a soleus muscle flap. Based proximally, muscle vascularity is reliable to a point 5cm above its tendinous insertion. No functional deficit is noted following transfer although the long term effects on the venous pump mechanism have not been reported. High energy injuries with comminuted tibial fractures can result in soleus laceration and contusion excluding its use. In these cases, free tissue transfer of muscle from outside the zone of injury is indicated. For coverage of smaller defects the tibialis anterior muscle can be split longitudinally and flipped through 180 degrees to cover the tibial shaft. This technique preserves the innervation to the muscle and there is no functional deficit.

Defects in the distal third of the leg cannot easily be replaced with skin grafts as muscle cover is limited. Choices for cover include fasciocutaneous and free flaps. The axis of rotation of distally based fasciocutaneous flaps is designed with the base including one of two vascular perforators located 6cm and 12cm superior to the medial malleolus. These can be identified preoperatively using handheld Doppler. Fasciocutaneous flaps cannot be used when there has been extensive degloving as perforators will have been avulsed. Under such circumstances, in infected wounds, or where there is segmental bone loss, a free muscle transfer with a split skin graft is more appropriate.

Soft tissue cover in the foot can present a challenging prospect to the reconstructive surgeon with different requirements for dorsal and plantar surfaces. Dorsal skin is thin and pliable and provides a smooth undersurface to allow for tendon gliding whereas the weight bearing plantar skin is glabrous and able to withstand the shearing stresses of ambulation due to its dense soft tissue attachments to bone. Reconstructive goals include the restoration of sensibility, cover of bones and tendons, to minimize bulk and provide resistance to tangential shearing movement. The ability to perceive deep pressure is essential for weight bearing, ambulation and long-term stability of coverage.

Skin grafts on the dorsum of the foot are susceptible to trauma from footwear and need protection until they are mature. Small defects unsuitable for grafts can be covered by local fasciocutaneous or muscle flaps (dorsalis pedis, lateral calcaneal, extensor digitorum brevis, abductor hallucis, or abductor digiti minimi). For more extensive defects, free fascial transfers (lateral arm, radial forearm, or temporalis) can be used with a skin graft. Free fascial flaps lack bulk and produce an excellent contour to the dorsum of the foot while permitting tendon gliding. Free fasciocutaneous or muscle flaps should be used for contaminated wounds or deeper defects.

The specialized plantar skin is best replaced with like tissue. Heel or forefoot defects with an adequate pad of subcutaneous tissue do well with a split or full thickness graft. Delayed application of skin grafts can reduce the severity of hyperkeratosis seen at the junction of plantar skin and skin graft. In wounds where the subcutaneous padding has been lost, the non-weight bearing skin of the medial instep can often be used for transposition to adjacent weight-bearing areas, i.e. lateral instep and heel. Axial flaps such as the medial plantar artery instep flap are useful for heel cover as they contain cutaneous nerves and are sensate. The toe fillet flap provides the best cover for forefoot defects with innervated skin, and minimal donor site morbidity. If the medial and lateral plantar nerves are intact, deep pressure sensation will be preserved offering protection from pressure necrosis to free flap cover. Muscle flaps, e.g. latissimus dorsi, provide bulk for padding of bony prominences and ambulation will be restored in most cases with appropriate rehabilitation. Rehabilitation of these patients is especially important with provision of custom-made shoes and instruction on foot care.

Chronic osteomyelitis has been defined as ‘one or more foci in bone that contain pus, infected granulation tissue, sequestra, a draining sinus and resistant cellulites’. Treatment involves radical debridement of all devascularized bone, poorly vascularized soft tissue, and infected granulations. The wound is then left to heal by secondary intention, skin grafted, or covered with a flap. In cases where there is segmental bone loss skeletal reconstruction should be delayed and closure is best accomplished using free or pedicled muscle flaps. Reconstructive options once primary healing has occurred depend on the size of the defect and include: cancellous bone grafting; the use of vascularized iliac crest or fibula grafts; and the use of bone transport techniques.

The decision to amputate is made on a case by case basis, considering the injured extremity, the patient’s age, associated injuries, and socioeconomic situation. While recovery and rehabilitation following complex lower limb reconstruction can often be a lengthy process, amputation often hastens recovery and return to work and with a suitable prosthesis can often provide a functional extremity. Disruption of the posterior tibial nerve is generally considered an indication for amputation because of the importance of plantar sensibility. Amputation should also be considered in massive degloving injuries of the foot as reconstruction will not recreate a normal foot.

Valid comparisons of the results of soft tissue cover are difficult to make for the following reasons:

Fasciocutaneous flaps provide reliable soft tissue cover in the extremities with a reported 97% success rate, as measured by wound healing and limb preservation. Free tissue transfer for cover of Gustillo grade III lower limb injuries has resulted in limb salvage rates of greater than 90%. In all series the highest success rate with the least complications occurred when patients were treated in the acute period. A major factor in obtaining better outcomes was the surgeon’s learning curve with results improving with experience.

Long-term follow-up of 72 patients with Gustilo grade IIIB open fractures treated with free tissue transfer revealed a limb salvage rate of 93%, with 96% patient satisfaction. However, only 28% of these patients returned to long-term employment within 2 years in contrast to 68% of patients who underwent amputation for lower extremity trauma during the same period. This puts into perspective the fact that despite the technical ability to achieve salvage in a severely injured limb the surgeon must bear in mind the long-term goals of occupational rehabilitation before selecting patients for this treatment.