Should You Consider Using Bioengineered Alternative Tissues Over Tendon And Bone?

Caitlin S. Garwood, DPM, and Paul J. Kim, DPM, MS, FACFAS

Given the inherent obstacles with complex lower extremity wounds, the need for immediate coverage and possible risks with using flaps and pedicles, these authors explore the potential of employing bioengineered alternative tissues in wounds with exposed tendon and bone.

Complex lower extremity wounds with exposed tendon and bone are a reconstructive challenge. Surgeons have used free tissue transfer as the treatment of choice in order to achieve adequate soft tissue coverage. In certain settings, however, free tissue transfer or local flap coverage is associated with increased morbidity and mortality, and may not be the best option.

   Unfortunately, in these situations, amputation may be the treatment of choice or the end result.1-6 The development of bioengineered alternative tissues (BATs) has led to new methods for reconstruction of these complex wounds. When free tissue transfer is not an option, surgeons have turned to the use of BAT in combination with split-thickness skin grafting (STSG) for adequate wound coverage.2,5 Specifically, one can use dermoconductive BATs (those with no cellular components) to serve as scaffolds for cellular migration for deep tissue coverage and neodermis production.6-8 Due to potential complications associated with complex microsurgical procedures, this method of wound coverage is becoming increasingly popular.

   As soon as a wound on the lower extremity presents with exposed tendon or bone, the need for quick and effective coverage becomes a more daunting situation. Trauma such as severe crush injuries, pressure ulcers, chronic diabetic ulcers, venous or arterial ulcers, and surgical wound complications can all lead to deep exposure of these structures. Without the exposure of such structures, typical management would be debridement, local wound care with dressings and offloading. Due to the biology of tendons and bone, the need for immediate and definitive coverage is key.3,5,9

   The main issue with deep, complex wounds of the lower extremity is that the wound itself does not provide the adequate blood supply to keep a skin graft alive. The lower extremity also has limited options for local tissue transfer. Surgeons have accordingly turned to free tissue transfer. In many patients the length and intricacy of these procedures is contraindicated and can lead to significant complications. Contraindications for free flaps include significant comorbidities, hemodynamic instability, age, inadequate blood flow and infection. Things to consider prior to surgery are the length of the procedure, donor site morbidity, the need for close monitoring and potential failure.3,4

   Techniques using flaps and pedicles are associated with a failure rate of 12 percent and an amputation rate of 18 percent.3,10-13 There has also been an estimated length of stay of about 76 hospital days with an average of eight surgeries.3,10-13 It is evident that a simpler method of wound coverage would be more ideal and one should possibly attempt this prior to free tissue transfer in some patients.

   Blood vessels and synovial fluid nourish tendons. When tendons lose overlying soft tissue, there is disrupted nourishment and tendons can quickly become desiccated. This causes loss of the tendon fibers as well as loss of proper function of the tendon. Tendons can quickly lose their ability to glide and operate at joints, leading to the need for other surgical interventions such as joint fusions or tendon transfers. In order to avoid these procedures, surgeons aim for quick and definitive coverage.9

   Similar to tendons, bones need quick and definitive coverage. The most important reason is to decrease the risk of infection. Osteomyelitis can be a devastating sequela of wounds with exposed bone. Timely soft tissue coverage of bone also increases the potential for healing any fractures that are present.14,15

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