In considering the tissue defect, thought must be given to the anatomic location and the etiology and nature of the wound and to the wounding agents and their
kinetics. In high velocity wounds the zone of injury may be more extensive than the apparent size of the external defect. This effects the quality of local tissues that may be viable, but the degree of their contusion and circulatory impairment may be so extensive that any attempt to provide coverage by shifting them will cause necrosis. In such patients free flap coverage is the only satisfactory alternative.
Indications and requirements for reconstruction vary according to the level of the extremity injury. The more proximal the wound, the greater the likelihood that local tissues, can be used for closure and therefore fewer the indications for free flap transfer. Salvage of the elbow or the knee joint in conjunction with a below elbow or a below knee amputation represents a special situation; here local muscles are not always available. The benefits of maintaining a functioning knee or elbow joint and of avoiding a higher amputation are so great that closure with a vascularized tissue transfer (Fig. 7.1), may be worth the attempt.19,76
Below the elbow or knee free flap coverage is indicated for large defects in which there is exposed bone or in the distal third of the leg where, because of lack of surrounding soft tissues, all but the smallest defects require free tissue transfer. By definition in extensive extremity injuries, type Illb and IIIc in the Gustilo classification, local tissues are not available.26
The reconstructive requirements of the heel and foot are similar. Both coverage and durable weight bearing surface with protective sensation should be provided whenever possible. Again local sensory tissues, such as plantar flaps, the dorsalis pedis flap and the lateral calcaneal flap from the lateral aspect of the foot, are useful for limited tissue losses. Larger defects of the foot, may require free tissue transfer.11,62 When similar injuries occur in the hand vascularized tissue is available from the foot,55 but other donor sites must be used for the foot itself. There is no ideal tissue however for substitution of the specialized weight bearing surface in a completely satisfactory manner. Sensate fasciocutaneous flaps or muscle flaps with skin grafted surface have all been used with success.56 Special footwear however, for protection of the transferred tissue, is always necessary.68
Free vascularized bone flaps are necessary for patients with segmental skeletal defects of the long bones or for segmental defects of the mandible, which frequently may be irradiated. Patients with defects longer that 6 cm do less well with cancellous bone grafting and the incidence of delayed healing and nonunion is common them. Vascularized bone flaps are a better choice for these patients; they avoid at the same time, particularly in the upper extremity, the awkward external fixation devices that are necessary for the Ilizarov bone transporting technique. The use of vascularized bone flaps for the treatment of aseptic necrosis of the femoral head has also proven invaluable.
Besides the obvious need for soft tissue coverage and skeletal reconstruction, another indication for free tissue transfer is the need to reanimate a paralyzed face 28 or to dynamically reconstruct an extremity by the transfer of free vascularized and neurotized muscle.53 Thus, closure of the eyelids and restoration of a smile can now be achieved (Fig. 7.2).
Elbow flexion can be obtained by substituting the function of the biceps muscle in longstanding brachial plexus injuries. Flexion and extension of the digits may also be restored by free muscle transfer in patients with Volkman's ischemic contracture, severe avulsion injuries or extensive electrical burns. Similarly functional restoration
Fig. 7.1. A) Short below knee stump with exposed bone and lack of soft tissues.
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