Flap Coverage for the Foot

L. Scott Levin

Alessio Baccarani

The goals of soft tissue reconstruction for the foot and ankle region are satisfactory wound coverage and restoration of function. Ancillary considerations include acceptable appearance and minimal donor site morbidity. For soft tissue coverage alone, muscle and axial fasciocutaneous flaps remain primary choices in the lower extremity. Random pattern cutaneous flaps and musculocutaneous flaps usually have more limited applications, but should be considered. Free flaps are generally the soft tissue coverage of choice for most extensive defects of the foot and of the lower third of the leg. Amputations and fillet flaps always represent a fourth possibile option when the limb cannot be preserved in its entirety. Finally, procedures such as osteotomies and/or ostectomies for the production of soft tissue “gain” and resultant coverage of the defect are becoming more common.

Indications

Each anatomic region of the foot has certain characteristics that will influence selection of the flap to be transferred for reconstruction. The foot has special requirements for shoeing and ambulation. The reconstructive ladder for injury to the foot is based on whether there is a fracture, what part of the foot is exposed, and whether the area is weight bearing or non–weight bearing. The ankle and the dorsum of the foot require thin, pliable soft tissue coverage for exposed tendons, bones, or joints. The plantar skin is thick and heavily keratinized, designed to resist high stress, and anchored to underlying bones and ligaments by thick fibrous connective tissue.

Topographically, the forefoot includes the dorsal areas of the metatarsals and toes. The plantar aspect includes the metatarsal heads and the instep. The hindfoot can be divided into the plantar aspect, instep, and lateral aspect of the calcaneus. The ankle can be divided into the area of the Achilles tendon and the anterior aspect of the tibiotalar joint. In the forefoot, the dorsum and the area over the toes are primarily skin and subcutaneous tissue, making the exposure of tendons and joints more probable with high-energy injury. The plantar forefoot is prone to avulsion because of the vertically oriented septa that bridge from the plantar fascia to the dermal elements of the skin. The heel pad is a very unique structure that contains cushion-like shock-absorbing chambers of fat that are not easily replaced if loss is due to such an avulsion injury.

Achilles Tendon Area

The Achilles tendon area is characterized by thin skin with little or no subcutaneous layer. Among local flaps, we consider the sural fasciocutaneous flap one of the best options for covering this area. Other flaps options include lateral supramalleolar and lateral calcaneal artery.

Ankle and Foot Dorsum

Most shallow wounds on the foot dorsum may be safely closed with a split-thickness skin graft. If necessary, exposed extensor tendons may be resected and the skin graft may be applied to the underlying periosteum, providing a simple and quick solution to the clinical problem. For management of larger wounds with bone or tendon exposure, flaps may be required. The most common local flaps used for coverage of this area are abductor hallucis–abductor digiti minimi muscle flaps, extensor digitorum brevis muscle flap, lateral supramalleolar flap, and sural fasciocutaneous flap.

Plantar Forefoot

Local flaps play a major role in the management of deep wounds of the distal third of the foot. Severe injury or infection to a single toe may be best managed by toe or ray amputation, and subsequent closure by means of a plantar or of a dorsal skin flap. If additional skin is required, an adjacent toe may be filleted and trasposed for closure. Ray amputation may be necessary if the metatarsal bone is infected, injured, or devascularized. Metatarsal head ulceration is the most frequent lesion occurring in this area, especially in patients presenting with peripheral neuropathy and associated arthropathy. Many local flaps have been described to treat plantar forefoot defects. The most commonly used are neurovascular island flap (Moberg’s flap), toe fillet flap, V-Y plantar flap, and suprafascial flaps medially or laterally based.

Transmetatarsal amputation provides a functional option when three or more rays have been seriously damaged, expecially in post-traumatic, ischemic, or neuropathic patients. No prosthetic or orthotic device would be necessary, and the patient may be able to wear normal shoes. Achilles tendon lenghtening should be performed in conjunction with transmetatarsal amputation to avoid equinus deformity and stump ulceration.

Plantar Midfoot

The midfoot is defined as the region between the midshaft of the metatarsals and the proximal tarsal row. It comprises the medial non-weight bearing arch as well as the more lateral weight bearing area. Small wounds in this region may be reconstructed with a variety of reconstructive options. Split-thickness skin grafts may provide adequate coverage if the transverse arch of the foot has been maintained, thus allowing the midfoot to remain a largely non–weight-bearing region. Local flap options for reconstruction of defects in this area include neurovascular island flap, V-Y advancement flap, and medially or laterally based suprafascial flaps.

Wounds larger than 4 to 6 cm generally require either free flap reconstruction or midfoot amputation to achieve a stable coverage. Clearly amputation would represent the second option if foot salvage is not indicated or possible with free tissue transfer. The two most common forms of midfoot amputation are the Lisfranc amputation and the Chopart amputation. The Lisfranc amputation is the amputation at the tarso-metatarsal joint and is associated with a high rate of equinovarus deformity. The Chopart procedure requires an intertarsal resection, just distal to the cuboid and navicular bone. Both types of midfoot amputations will affect the patient’s ability to dorsiflect and evert the residual limb because of disruption of the insertions of the peroneal and tibialis anterior tendons.

Plantar Hindfoot

Hindfoot soft tissue repair is the most challenging to the reconstructive surgeon. Reconstruction should provide durable soft tissue for safe weight-bearing, while permitting a normal ankle motion. The dualism of form and function represents a mandatory principle to be considered in the management of wounds in this area. Damage to the neurovascular and tendinous structures beneath the flexor retinaculum is an event that may impair permanently the patient’s gait, mandating a below-knee amputation.

Many local flaps have been described to restore healing in the hindfoot area. The most common are intrinsic muscle flaps (abductor hallucis AH, flexor digitorum brevis FDB, abductor digiti minimi ADM); medial plantar artery flap; heel pad flaps; and sural fasciocutaneous flap. With the only exception being the sural artery fasciocutaneous flap, all the regional flaps listed require antegrade blood flow through the posterior tibial artery and its branches. Those procedures are therefore often not possible in patients affected by peripheral vascular disease.

Large hindfoot defects greater than 5 to 6 cm in patients devoid of the posterior tibial vessels should be considered for microsurgical reconstruction. Many neurosensory flaps have been described for microvascular transplantation in an effort to provide sensation to the plantar reconstruction. Lateral arm and deltoid represent two useful donor sites because of their reliable neurovascular anatomy, the ability to recover protective sensation, and because of their thickness; however, a correlation between the presence of flap sensation and the success of hindfoot reconstruction has never been established. Microvascular transplantation of muscle with skin graft coverage can provide succesful outcomes if the surgeon remembers to remove the underlying bone prominences, educates the patient on proper shoe wear, and performs frequent follow-up. We believe the use of muscle to obliterate dead space and aid in delivering antibiotics to the region is important for successful
outcomes in cases of osteomyelitis. Because of its proximity to the wound margin, the posterior tibial artery is usually the preferred recipient vessel in hindfoot reconstruction. For hindfoot coverage, it is important to avoid scarring around the posterior tibial nerve and around the posterior tibial tendon, which may become exposed or trapped during the healing process.

Table 34-1. Surgical Reconstructive Options

Foot Region	Locoregional Flaps	Free Flaps	Amputation and Ancillary Procedures
Achilles tendon region	Sural fasciocutaneous Lateral calcaneal artery	Fasciocutaneous	Syme Below knee
Ankle and dorsum	Intrinsic muscle flaps (AH, ADM, EDB) Sural fasciocutaneous Lateral supramalleolar	Fasciocutaneous Myocutaneous	Syme Below knee
Plantar forefoot	Toe fillet flap Neurovascular island flap V-Y advancement Suprafascial flaps	Fasciocutaneous Myocutaneous Muscle	Ray Transmetatarsal
Plantar midfoot	Neurovascular island flap V-Y advancement Suprafascial flaps	Fasciocutaneous Myocutaneous Muscle	Lisfranc Chopart
Plantar hindfoot	Intrinsic muscle flaps (AH, FDB, ADM) Medial plantar artery flap Sural fasciocutaneous Suprafascial flaps (heel pad flaps)	Fasciocutaneous Myocutaneous Muscle	Syme Calcanectomy

Syme’s amputation has a well-established role in the management of complex hindfoot deformities, especially in diabetic patients. The procedure involves the use of the heel pad as a soft tissue cover over the distal end of the residual tibia and fibula. Table 34-1 summarizes the main surgical reconstructive options for each region of the foot.

Preoperative Planning

Evaluation of the patient with soft tissue injury should include determination of the time of injury, mechanism, energy absorption, fracture configuration, systemic injuries, damage to the soft tissue envelope, vascularity of the extremity, sensibility, ultimate ability to salvage the foot (which is both functional and sensate), and underlying medical conditions of the patient. The principles of evaluation of orthopaedic trauma are the same for any basic medical evaluation. These principles apply whether in the outpatient clinic, emergency room, or trauma unit. An evaluation of the perfusion of the traumatized limb is of paramount importance, and if vascular (arterial) injury is suspected, a vascular surgery or microsurgery consultation should be obtained. Compartment syndrome should be considered and ruled out in any injured extremity, particularly after crush injuries. A general motor examination including the active and passive range of motion as well as a detailed sensory examination should be performed. A nerve deficit may be secondary to a spinal cord injury, nerve laceration, compartment syndrome, traction injury, or entrapment between bony fragments. The radiologic evaluation starts with standard plain radiographic examination. Computed tomography (CT) is indicated in complex foot injuries and may give valuable information regarding soft tissue damage as well.

The wound should be inspected once, and the wound pattern and contamination noted. The next inspection of the wound should then be in the operating room under sterile conditions. Repetitive examination of open wounds in the emergency room has led to higher rates of wound infections and osteomyelitis and should be avoided. In cases of open fractures in polytrauma patients, workup of other injuries may take several hours, not to mention the need for emergent lifesaving visceral surgery that may precede definitive care for open fractures. Prophylactic antibiotics are administered and given on a regular basis until definitive wound debridement and fracture stabilization can be performed.

In summary, with any lower extremity reconstruction, three basic principles are of great importance and should therefore be carefully optimized before undertaking any reconstructive effort:

Evaluation of underlying skeletal architecture, stabilization, and management of associated orthopaedic injuries
Adequate wound preparation, which includes full debridement and control of any local infection prior to coverage
Overall assessment of the patient’s suitability for reconstruction and rehabilitation, including the opportunity of restoring some degree of protective sensation to the limb

Recipient Vessels

If free tissue transfer is required for wound coverage, then the last point of consideration prior to surgery should be the selection of recipient vessels for microvascular transfer as this will influence patient positioning within the operating room. A general agreement on which vessels to use has not yet been reached. Conflicting data have been reported on the survival and outcome of the transferred flaps, depending on the vessel used or the location of anastomosis proximal or distal to the zone of injury. For example, the anterior tibial vessels may be preferred for their easy accessibility, whereas the posterior tibial vessels are strongly advocated by others due to their larger diameter.

The most important factors influencing the site of recipient vessel are the site of the injury and the vascular status of the lower extremity; it is best to ensure adequate arterial inflow and adequate venous outflow before surgery. Intraoperatively, it is imparative that the anastomosis be performed outside the zone of injury. The type of flap used, method, and type of microvascular anastomosis represent less important factors in determining the recipient vessels.

Surgery

Locoregional Flaps

As discussed in the Indications section, locoregional flaps play a very important role into the management of foot wound coverage.

Toe Fillet Flap

Anatomy

The flap is based on the medial and lateral neurovascular bundles of the toe to be amputated.

Flap Design

The toe adjacent to the wound is outlined. This island flap is better disssected with the patient in supine position under tourniquet control.

Technique

The flap is elevated beginning distally, off the distal phalanges and flexor tendons. The medial and lateral bundles are identified in the associated web spaces. A connecting incision to the wound is made. The toe is thus disarticulated at the metatarsophalangeal joint, and the dorsal skin is used for donor site closure. The flap is then rotated to the defect, ensuring a safe placement of the neurovascular structures (Fig. 34-1).

Neurovascular Island Flap

Anatomy

The flap is based on the great toe neurovascular bundle on the fibular side.

Flap Design

The flap is designed on the fibular side, centerd over the area of the neurovascular bundle. These flaps may cover wounds up to 2 to 3 cm in diameter. The use of a tourniquet facilitates a safe dissection. The donor site often requires a skin graft closure.

Technique

The flap is elevated on the lateral plantar aspect of the great toe at the level of the phalangeal periosteum. The vascular bundle can be proximally dissected in the web space to allow a longer arc of rotation. An incision is made to connect the web space to the wound, and the flap is thus transposed to the defect.

V-Y Advancement Plantar Flaps

Anatomy

These flaps are based on vertical perforating vessels throughout the plantar aspect of the foot.

Flap Design

Many V-Y advancement flaps may be designed with different orientation on the plantar foot. The use of a tourniqut facilitates a safer dissection.

Only gold members can continue reading. Log In or Register to continue