Dermatologic Surgery: Closure Design, Margins, and Safety
Plan the defect before cutting
Dermatologic surgery questions test preoperative planning as much as technique. Mark the clinical margin from the visible lesion edge, orient the ellipse along relaxed skin tension lines, and design a fusiform ellipse with a length-to-width ratio near 3:1 so the ends close without standing cones. Undermine conservatively to reduce tension, obtain hemostasis, and choose suture material by location and tension. On the face, fine nonabsorbable sutures and early removal reduce track marks; on the trunk and extremities, absorbable deep sutures and longer surface support are common.
Concepts to know
Understand Mohs micrographic surgery for high-risk basal cell carcinoma, squamous cell carcinoma, and selected other tumors, especially in cosmetically or functionally sensitive areas. Know the difference between a flap and a graft, when a graft needs a vascular bed, and why cartilage or bone exposure changes the plan. Know maximum local anesthetic doses: lidocaine with epinephrine is commonly capped at 7 mg/kg, plain lidocaine at 4.5 mg/kg. Review anticoagulation management and antibiotic prophylaxis indications rather than stopping agents reflexively.
Traps
Do not confuse in vivo margins with margins measured on a fixed specimen. Do not force closure under tension when a flap or graft is safer. Dog-ears are not complications if managed with a proper standing cone excision. Eyelid margin surgery requires precise alignment to avoid notching.
Worked rule
For a 1 cm lesion, a 3:1 ellipse is about 3 cm long. On a curved or tension-prone surface, lengthen the ellipse or change the closure rather than accept blanching and necrosis.