Open fractures of the lower extremity can damage not only bone, but also surrounding vasculature and soft tissue. This requires surgical treatment to both stabilize the fracture and properly treat the involved tissue. The wound should be debrided, which involves the removal of any foreign material or poor or damaged tissue, and thoroughly irrigated to reduce the risk of infection.
Because the lower extremity has a lack of excess tissue, a soft tissue defect often results from this type of trauma. Reconstructive options include a fasciocutaneous free flap (includes skin, subcutaneous tissue, and underlying fascia) or muscle free flap (includes muscle only).
Common donor sites include the rectus abdominis muscle or the anterolateral thigh (ALT) muscles. A free flap involves removing the donor tissue while preserving the vascular bundle (artery and vein) and performing microsurgery to reattach it to the vascular bundle of the lower extremity. This blood supply is what ensures the survival of the flap. See below for an explanation of muscle flaps and the different types.
What is a Muscle Flap?
A flap is a piece of tissue taken from one area (donor site) and transferred to another (recipient site). A flap is different from a skin graft in that it maintains its own blood supply. This blood supply allows the flap to be moved from one area to another and survive. Flaps can be classified based on several factors, including blood supply, tissue composition, and donor site.
A free flap involves complete removal of the tissue from the donor site and placing it onto the defect. A free flap is the most complex type of flap as it requires microsurgery to connect the blood vessels of the flap to the vessels of the recipient site.
A pedicled flap maintains direct connection to the donor site and is stretched to cover the defect.
Depending on where the wound is and how large the defect is, different tissue types may be used. Some of the commonly used tissue types are as follows:
Cutaneous flaps involve only the skin and superficial fascia and are used on small defects.
Fasciocutaneous flaps involve the skin, subcutaneous tissue, and deep fascia and provide abetter blood supply.
Musculocutaneous flaps contain the skin, subcutaneous tissue, fascia, and muscle. The added muscle allows you to fill a larger defect.
Muscle flaps contain muscle only and allow for functionality of the muscle at the recipient site. Because this type of flap does not include skin, a skin graft can also be placed to cover the site.
Skin grafting is the removal of the top layer of the skin and placing it onto another area. The graft can be placed on top of healthy, vascularized wound tissue (granulation tissue) to speed up the healing process. Because the skin graft does not have a blood supply of its own, it depends on the vasculature of the granulation tissue to survive. Through a process called neovascularization, the blood vessels in the granulation tissue spread to the skin graft and begin to grow. Negative pressure wound therapy is typically applied in order to optimize granulation.