Continuing Education Activity
Flaps are sometimes used to close skin defects and vary from simple local flaps to complex free flaps. The design of a flap is a key step in treating skin defects operatively. This activity outlines the evaluation and management of skin defects using flaps and highlights the role of the interprofessional team in managing patients with skin defects.
- Outline the management considerations for patients with skin defects.
- Explain the importance of adequate patient counseling and collaboration when designing a local flap.
- Summarize the common pitfalls a surgeon may fall into when designing flaps.
- Describe the importance of collaboration and communication among the interprofessional team to enhance care delivery for patients postoperatively after a flap operation.
The flap design requires creativity and planning from the surgeon. The surgeon must be aware that the donor site must be perfectly closed in a functional manner. The goal of ideal flap design is to restore the skin’s functions and properties. Perfect anatomy knowledge is vital for successful outcomes.
Anatomy and Physiology
The flaps are classified according to the blood supply into axial local flaps, which means it contains a single arteriovenous pedicle, and it is indicated when primary closure is not advisable, and the area does not support split-thickness skin graft (STSG) and if the length-width ratio is more than 2 to 1. The other type is random pattern flaps, which means it is supported by many microcirculation without a single arteriovenous pedicle; its indications are when primary closure is not possible, and the area does not support STSG, and the length-width ratio is less than 2 to 1. The last type is a venous flap, which means that it uses veins as inflow/outflow of arterial blood.
The flaps are classified according to tissue type into:
- The cutaneous flap, which includes skin and subcutaneous tissue.
- Fascial flap, which includes fascia without overlying skin such as temporoparietal flap.
- Muscle flaps usually require an additional skin graft transfer to cover muscle; the muscle can be transposed to form a composite flap.
- Bone flaps such as the free fibula flap, which is based on the peroneal artery pedicle, used in diaphyseal bone reconstruction, and free iliac crest flap. Its base is deep circumflex iliac vessels used in metaphyseal reconstruction flaps.
- Composite flaps that consist of different tissue types such as radial forearm flap (fasciocutaneous flap).
Another classification depending on mobilization type:
- Local flap in which tissue transferred from adjacent area to the defect.
- Distal random flap: the transfer of tissue to a different site; its indications are when surrounding tissue does not support a local flap, and the length-width ratio is less than 2 to 1.
- Distal axial pattern flap: indicated when the surrounding tissues cannot support the local flap and when the length/width ratio required more than 2 to 1.
It is based on direct cutaneous vessels supplying certain skin segments. They provide a large wound closure. Axial pattern flaps need good surgical technique and attention to detail while developing the axial flap.
4- Free tissue transfer and its indications when local or distant tissue is not sufficient for either distal axial or random flaps.
Harvesting a free flap is usually associated with the production of a special donor site morbidity. Accordingly, the implication for microvascular tissue transfer is just made if there is a significant defect, which cannot be closed directly for technical or functional purposes. Therefore, smaller defects usually are not indicated for a free flap.
Indications for flap coverage are:
- Soft tissue injury with exposed
- Orthopedic implants
There are few conditions in which flap coverage gives poor outcomes and hence not indicated in such circumstances and these include:
- Failure to achieve clear margins before performing a flap
Equipment varies depending on the type of flap. Simple flaps may require a scalpel and forceps, while free flaps may require a doppler, microscope, vessel loops, vascular clamps, and more.
Preoperative considerations should include:
- Evaluation of the smoking history
- Peripheral vascular disease
- Steroid use
- Previous surgeries
- The extent of traumatic injury
- Patient age and skin condition
- Defect location.
Before a free flap or large muscular rotational flap, a preoperative angiogram may help evaluate circulation and angiosomes.
In complex injuries, primary wound closure is difficult. Ideal results could be obtained by the use of adjacent tissue as local flaps. The satisfaction of the surgeon and patient needs excellent planning of surgical techniques. Well-planned flaps result in excellent cosmetic results with minimal complications of the surrounding tissues.
Ladder of Reconstruction: In increasing complexity order
- Primary closure of the wound
- Secondary closure of the wound and the healing will be by secondary intention
- Skin grafts (full and split-thickness)
- Local flaps
- Regional flaps
- Free tissue transfer
In children, we can accept wound debridement and healing by secondary intention if the bone is exposed.
1. Finger Flaps
The main target of the management of fingertip injury is a pain-free fingertip with sensate skin. For injuries that have a loss of soft-tissue without bone exposed, healing by secondary intention or skin graft is considered the best method. If the bone is exposed and a nail matrix is available to provide a stable nail plate, the coverage using a local advancement flap can be done. The outcome of the injuries of nail-bed is mainly dependent on the severity of the germinal matrix injury.
A flap is considered a skin with a different amount of underlying tissue used to cover a defect. Usually, it receives its blood supply from another source other than the original tissue on which it is transferred.
- Digital Island Artery: Used in wounds over dorsal oblique fingertip and volar oblique fingertip.
- V-Y Advancement Flap: Used in wounds over the straight or dorsal oblique fingertip. Advancement flaps include precisely planned incisions to close primary injuries in a linear manner. Advancement flaps are categorized as uni-pedicle, bi-pedicle, Y-to-V, and V-to-Y flaps, each with its benefits and drawbacks. When designing the advancement flap, the surgeon must estimate primary and secondary transfer to avoid distortion of surrounding tissues.
- Cross Finger Flap: Used in wounds over the volar oblique fingertip, used mainly in patients more than 30 years old, it causes less stiffness.
- Reverse Cross Finger Flap: Used in wounds over the dorsal finger and MCP.
- Moberg Advancement Volar Flap: Used in wounds over the thumb's volar aspect if less than 2 cm. Disadvantage: Thumb IPJ contracture and stiffness.
- Neurovascular Island Flap: Used in wounds over the volar thumb up to 4 cm, does not cause IPJ contracture.
- Axial Flag From the Long Finger: Used for wounds over the volar proximal finger, dorsal proximal finger, and lacerations over MCP.
- First Dorsal Metacarpal Vessel Flap: Used in lacerations over the dorsum of the thumb and the volar of the thumb if more than 2 cm, it utilizes the first dorsal metacarpal artery, it does not cause IPJ thumb contracture.
- Thenar Flap: Used for wounds over the volar oblique fingertip to middle or index finger in patients less than 30 years.
- Z-Plasty/ 60 Degrees Flaps: Used in the lacerations over the first web space lacerations, it increases the length up to 75%.
- Posterior Interosseous Fasciocutaneous Flap: Used in wounds over the first webspace.
- Groin Flap: Used in wounds located in the dorsal hand.
2. Arm Flaps
- Lateral Arm Flap: Used in lateral arm wounds, it utilizes the posterior radial collateral vessels.
- Latissimus Dorsi Myocutaneous Flap: Indicated for large wounds around the elbow, it utilizes the thoracodorsal artery perforators.
3. Leg Muscle Flaps
- Medial Gastroc Flap: Indicated for midline and medial defects located over the tibia proximal third, it utilizes the medial sural vessels.
- Lateral Gastroc Flap: Indicated for lateral wounds located a proximal third of the tibia.
- Soleus Flap: Indicated for defects over the middle third of the tibia, the vessels are: the peroneal artery (proximal), the posterior tibial artery (medial), and popliteal artery trunk.
- Gracilis Flap: It is the most common donor for the free muscle transfer; it utilizes the medial femoral circumflex vessels. The Gracilis muscle is the most superficial muscle of the adductor compartment. Indication: coverage of groin, pubis, perineum, scrotum, and vagina.
- Free Flaps: Indicated for wound coverage flap over the distal third of the tibia, also in the proximal and middle leg when the gastrocnemius and soleus are damaged.
- Groin Flap: It is an axial flap that is indicated mainly for providing soft-tissue coverage to the upper extremity; it utilizes the superficial circumflex iliac vessels, the main complication is the injury of the lateral femoral cutaneous nerve.
- Reverse Sural Artery Pedicle Flap: A fasciocutaneous flap can be applied to treat the lower leg and foot wounds. Surgeons can do this procedure after a quick time evaluating the lower leg's neurovascular anatomy and understanding the procedure's necessary technical features. The flap does not need microsurgical abilities and can be done reasonably quickly. The flaps usually have partial necrosis that might need debridement, dressing, and surgeon tolerance. The main complications of the procedure are lateral foot numbness and the requirement to harvest a split-thickness graft.
4. Bone Flaps
- Free Iliac Crest Flap: Used in metaphyseal reconstruction, it utilizes the deep circumflex iliac artery.
- Free Fibula Flap: Used in diaphyseal reconstruction, it utilizes the peroneal artery.
- Vascular Bone Graft (Radius Bone): Used in osteonecrosis of the scaphoid bone, taken from the dorsal aspect of the distal radius, it utilizes the first-second intercompartmental artery (a branch from the radial artery).
- Index Metacarpal Transposition Flap: Used mainly to reduce the space left between the ring and index finger after middle ray amputation.
- Little Metacarpal Transposition Flap: Used primarily to reduce the space left between the little and middle finger after ring ray amputation.
The dimension of the skin flap depends on many factors, the caliber and the length of the dominant artery on which a flap is based; the span and caliber of the nearby captured vessel; the length and caliber of the connecting choked artery, and the favorable anatomy of the venous return.
Flap procedure is not simple; complications can occur. Complications associated with the flap procedure are:
- Flap Failure: inadequate arterial flow, inadequate venous outflow
- Donor Site Morbidity: may be cosmetically unacceptable, pain related to grafting seroma
- Nonunion for vascularized bone transfer
- Hook Nail Deformity: tight tip closure, insufficient bony support
Flaps have similar complications like side-to-side wound closures; as the blood supply of a flap is considered more precarious, its complication has a more dire effect.
Risk factors for flap necrosis depend on:
- The injury reason
- The length-width ratio of the wound
- Pedicle thickness
- Operation time
- Injury site
- Blood perfusion direction
- Operating methods
- Size of the flap
The treatment goal is to maintain the skin and its underlying soft tissue and maintain the best environment for the gliding of muscles/tendons. In addition, the skin's contracture must be avoided to produce an acceptable outcome in terms of function and cosmesis. To obtain good results, the dermis, epidermis, and underlying layer should remain intact.
Enhancing Healthcare Team Outcomes
Flaps require a multidisciplinary approach consisting of surgeons, nurses, providers, and physiotherapists. Patients with skin defects need to be identified in the clinical setting, appropriate investigations must be done, and appropriate surgical intervention should be performed, and then undergo proper rehabilitation protocols.