Overview
Definition:
The Keystone flap is a fasciocutaneous flap that utilizes a dermal vascular plexus of an intact skin island, based on a perforator artery, to supply blood to the flap tissue.
History:
Developed by Drs
M
I
Rozen and L
M
Granzow in the early 1980s, it offers a reliable method for covering defects with local tissue.
Mechanism:
The flap derives its vascularity from perforators arising from a named artery (e.g., posterior interosseous artery, descending branch of the lateral circumflex femoral artery), with the dermal plexus maintaining viability.
Clinical Significance:
It is a versatile flap for covering soft tissue defects, particularly in areas with limited adjacent healthy tissue, offering good aesthetic and functional outcomes.
Indications
Defect Characteristics:
Suitable for moderate to large soft tissue defects
Ideal for defects over bony prominences or joints where other flaps may be cumbersome.
Anatomic Locations:
Commonly used for defects in the extremities (especially lower limb), trunk, and head and neck region
It is particularly useful for traumatic or post-oncologic resections.
Contraindications:
Absolute contraindications include compromised vascularity of the base or distal flap, infection at the recipient site, and inability to adequately mobilize the flap
Relative contraindications include active smoking and significant comorbidities.
Preoperative Assessment
Patient Evaluation:
Comprehensive medical history and physical examination to assess overall health status
Smoking cessation counseling is crucial.
Defect Analysis:
Detailed assessment of the defect size, depth, surrounding tissue quality, and any exposed vital structures (bone, tendon, neurovascular bundles).
Vascular Mapping:
Identification and marking of the origin and course of the supplying artery and its perforators using Doppler ultrasound or intraoperative exploration.
Donor Site Selection:
Choice of donor site based on defect location, flap size requirement, and availability of suitable perforators and skin
Consideration of adjacent tissue availability.
Surgical Technique
Flap Design:
The flap is designed with its base oriented towards the supplying perforator vessel
The dimensions are planned to cover the defect with adequate flap length-to-width ratio, typically up to 4:1.
Dissection:
Dissection proceeds from the distal tip of the flap proximally, preserving the dermal vascular plexus and identifying the pedicle containing the perforator vessel.
Mobilization:
The flap is carefully elevated, ensuring adequate length of the vascular pedicle to reach the recipient site without tension
The flap is often rotated or tunneled.
Insetting And Closure:
The flap is inset into the defect, and meticulous closure of the donor site is performed, often with skin grafting or direct closure if feasible to minimize morbidity.
Postoperative Care
Monitoring:
Close monitoring of flap viability is paramount, assessing for color, capillary refill, temperature, and turgor
Doppler ultrasound can be used for vascular assessment.
Dressing:
Light dressings are typically applied
Immobilization of the operative limb may be necessary to prevent shear forces on the flap.
Pain Management:
Adequate analgesia is essential, utilizing multimodal approaches
IV antibiotics are usually initiated perioperatively.
Activity Restrictions:
Patients are advised to avoid excessive pressure on the flap and limit strenuous activity until adequate healing is confirmed, usually for 2-3 weeks.
Complications
Flap Necrosis:
Partial or complete flap loss due to vascular compromise
Risk factors include inadequate pedicle length, kinking, external compression, and patient comorbidities.
Hematoma Seroma:
Collection of blood or serum under the flap
Can lead to increased risk of infection and delayed healing.
Infection:
Wound or flap site infection can compromise flap viability and lead to delayed healing or dehiscence.
Donor Site Morbidity:
Pain, delayed healing, scarring, or infection at the donor site
Poor donor site closure can lead to contour deformities.
Key Points
Exam Focus:
Understanding the vascular basis of the Keystone flap and its application in covering complex defects
Knowledge of indications and contraindications is vital.
Clinical Pearls:
Meticulous dissection to preserve the dermal plexus and perforator is critical for flap survival
Aggressive perioperative anticoagulation is generally not indicated unless there is specific thrombophilic risk.
Common Mistakes:
Designing a flap that is too long relative to its base, leading to pedicle compromise
Insufficiently mobilizing the flap to avoid tension at the recipient site
Inadequate donor site closure leading to contour deformities.