Overview
Definition:
Fasciocutaneous flaps are composite tissues containing skin, subcutaneous fat, and the underlying fascia, mobilized based on perforating vessels supplying the fascia and overlying skin
In the lower limb, these flaps are crucial for covering exposed bone, tendons, neurovascular bundles, and joints, particularly in complex trauma, oncological resections, or chronic non-healing wounds
Sural flaps utilize the neurovascular bundle associated with the sural nerve, while propeller flaps are designed as fasciocutaneous or myocutaneous flaps that are rotated on a vascular pedicle, often a perforator vessel, to reach defect sites.
Epidemiology:
Lower limb defects requiring reconstruction are common, particularly following high-energy trauma, road traffic accidents, and in diabetic patients with osteomyelitis or vascular insufficiency
The incidence of such defects necessitating flap coverage varies geographically and with trauma patterns
Propeller flaps have gained popularity due to their versatility in covering defects in challenging locations and their pedicled nature, avoiding free flap transfer in many cases.
Clinical Significance:
Effective reconstruction of lower limb defects is vital for limb salvage, restoration of function, and prevention of infection
Fasciocutaneous flaps provide well-vascularized tissue that promotes wound healing, reduces scar contracture, and allows for weight-bearing in the long term
Understanding the principles, indications, and techniques of sural and propeller flaps is essential for surgeons managing complex lower extremity reconstructions, impacting patient outcomes and quality of life.
Sural Flap
Definition:
The sural flap is a neurocutaneous flap based on the sural nerve and its accompanying vascular supply, typically the small saphenous vein and branches of the posterior tibial or peroneal artery
It can be raised as a fasciocutaneous flap, incorporating the deep fascia for enhanced vascularity
It is primarily used for coverage of distal lower limb defects, including the ankle, heel, and foot.
Types:
Distally based sural flap: Based on the vascular pedicle of the posterior tibial or peroneal artery and the sural nerve
Proximally based sural flap: Less common and relies on retrograde flow, generally not preferred for distal defects.
Arterial Supply:
Peroneal artery perforators and posterior tibial artery perforators that supply the deep fascia and contribute to the flap's vascular network.
Venous Drainage:
Superficial venous network converging into the small saphenous vein and its tributaries, which follow the sural nerve.
Neuro Component:
The sural nerve provides sensation to the flap
Preservation of the nerve's continuity is important for sensory recovery in the recipient site.
Propeller Flap
Definition:
A propeller flap is a type of pedicled flap where a flap of skin and subcutaneous tissue (or muscle) is incised and raised, but its vascular pedicle (usually a perforator artery and vein) is preserved and dissected proximally
The flap is then "propped" or rotated around this pedicle to cover a defect
The length of the pedicle dictates the arc of rotation, allowing coverage of adjacent or nearby defects without requiring microsurgical anastomosis.
Principle:
The flap is rotated on its pivot point, which is the origin of the perforator vessel from a larger artery
This allows for precise placement of well-vascularized tissue to cover complex defects.
Indications:
Coverage of defects over exposed bone, tendons, hardware, or joints in the lower limb
reconstruction after trauma, oncological resection, or debridement of infected wounds
defects that are not amenable to primary closure or skin grafting
cases where free flap transfer is contraindicated or undesirable.
Advantages:
Preserves the vascular pedicle, often avoiding the need for microsurgical expertise and prolonged operative time associated with free flaps
Good vascularity allows for coverage of challenging tissue beds
Versatile in terms of flap design and location
Can be raised as fasciocutaneous, adipofascial, or myocutaneous variants.
Disadvantages:
Limited arc of rotation depending on pedicle length and flexibility
Risk of pedicle compromise if over-rotated or kinked
Potential for venous congestion if the perforator is primarily venous
May require secondary procedures for scar revision or debulking.
Diagnostic Approach
History Taking:
Detailed mechanism of injury, presence of comorbidities (diabetes, peripheral vascular disease), smoking status, previous surgeries or radiotherapy to the area, and the nature of the defect (size, depth, exposed structures, surrounding tissue quality).
Physical Examination:
Thorough assessment of the defect, including size, depth, and presence of exposed vital structures
Evaluation of surrounding soft tissues for pliability and vascularity
Assessment of distal pulses and perfusion to rule out significant vascular compromise
Examination of potential donor sites for flap viability and suitability.
Investigations:
Doppler ultrasound or angiography to map perforator vessels for propeller flaps
Plain radiographs to assess underlying bone integrity and presence of osteomyelitis
CT angiography or MRI may be used in complex cases
Laboratory investigations including complete blood count, coagulation profile, and biochemical tests to assess overall health and anesthetic risk.
Differential Diagnosis:
Other flap options for lower limb reconstruction include free flaps (radial forearm, anterolateral thigh, latissimus dorsi), local random flaps, myocutaneous flaps, and skin grafts
The choice depends on defect size, depth, location, vascularity of recipient bed, donor site availability, and surgeon's expertise.
Management
Preoperative Planning:
Detailed planning of flap design, orientation, and pedicle dissection based on anatomical landmarks and imaging studies
Consideration of the recipient site's needs and the donor site's implications
Marking the flap outline and the vascular pedicle
Consultation with vascular surgery if significant vascular issues are suspected.
Surgical Technique Sural Flap:
Incise the skin around the defect
Identify the sural nerve and its accompanying vascular leash
Elevate the flap from distal to proximal, preserving the fascia and neurovascular bundle
Dissect the pedicle proximally to the desired length
Prepare the recipient bed by debridement of non-viable tissue
Transfer the flap to the defect and secure with sutures
Ensure adequate flap inset and closure of the donor site, often with skin grafting.
Surgical Technique Propeller Flap:
Design the flap based on the perforator artery and vein
Elevate the flap, carefully dissecting the perforator vessel from the surrounding tissue
Preserve adequate length of the perforator and its surrounding fascial sheath
Identify the defect and prepare the recipient bed
Rotate the flap on its pivot point to cover the defect
Suture the flap into the defect and close the donor site
Meticulous attention is paid to avoid kinking or tension on the pedicle.
Postoperative Care:
Close monitoring of flap viability, color, capillary refill, and temperature
Elevation of the limb to reduce venous congestion
Analgesia and antibiotic prophylaxis
Avoidance of pressure on the flap or pedicle
Regular assessment for signs of venous congestion or arterial compromise
Gradual mobilization as per protocol
Dressing changes as required.
Donor Site Management:
Primary closure for small donor sites
Skin grafting for larger defects to promote healing and prevent contracture
Split-thickness skin grafts are commonly used
Protection of the graft with appropriate dressings.
Complications
Early Complications:
Partial or complete flap necrosis due to vascular compromise (arterial inflow or venous outflow obstruction)
Hematoma formation
Seroma
Infection of the flap or donor site
Epidermolysis
Wound dehiscence.
Late Complications:
Chronic wound breakdown
Scar contracture
Sensory deficits in the flap or donor site
Bulky flap appearance
Recurrence of ulceration or defect
Non-union of underlying fractures if bone was exposed
Poor cosmetic outcome.
Prevention Strategies:
Meticulous flap design and dissection, careful preservation of vascular pedicles, avoiding over-rotation or tension on the pedicle, adequate debridement of the recipient bed, prophylactic anticoagulation in selected cases, appropriate postoperative positioning and monitoring, and judicious use of skin grafting for donor sites.
Prognosis
Factors Affecting Prognosis:
The size and depth of the defect, the vascularity of the recipient bed, the patient's overall health status and comorbidities (especially diabetes and peripheral vascular disease), the extent of previous radiation therapy, and the surgeon's experience
Proper flap selection and meticulous surgical technique are paramount.
Outcomes:
Successful reconstruction with fasciocutaneous flaps generally leads to good wound healing and restoration of limb form and function
Early and late complications can impact the long-term success
Propeller flaps offer a favorable risk-benefit profile for many lower limb defects, often obviating the need for free flaps.
Follow Up:
Regular follow-up is crucial to monitor flap viability, wound healing, and function
Patients should be educated on wound care and signs of complications
Long-term follow-up may be required to manage any late sequelae, such as scar management or revision procedures
Weight-bearing status should be guided by the underlying tissue and bone healing.
Key Points
Exam Focus:
Understand the vascular basis of sural and propeller flaps
Key indications for each
Donor site considerations
Common complications and their management
Differences between pedicled and free flaps.
Clinical Pearls:
For propeller flaps, precisely identify and preserve the perforator
map it preoperatively with Doppler
Avoid excessive rotation that can compromise venous outflow
For sural flaps, judicious dissection of the sural nerve maintains sensation
Consider the length and width ratios to ensure adequate flap vascularity
Adequate recipient bed preparation is critical for any flap success.
Common Mistakes:
Over-reliance on pedicle length without considering its caliber
Insufficient debridement of the recipient bed
Ignoring patient comorbidities that affect wound healing
Inadequate flap inset leading to tension or constriction
Failure to monitor flap viability closely postoperatively
Not considering distal pulses and overall limb perfusion.