Dermatologic Surgery, Lasers and Aesthetic Procedures
Scope
The exam tests surgical principles, suture and closure selection, Mohs surgery, laser physics, and safe aesthetic practice.
Core rules
- Excision: fusiform ellipse with 3:1 length-to-width ratio; margins perpendicular; undermining parallel to relaxed skin tension lines.
- Closure: simple interrupted, running, vertical mattress; absorbable deep sutures; face sutures removed earlier than truncal.
- Mohs micrographic surgery examines 100% of margins; indicated for high-risk BCC/SCC, recurrent tumors, and tissue-sparing sites.
- Laser physics: selective photothermolysis requires wavelength absorption, pulse duration shorter than thermal relaxation time, and adequate fluence. Pulsed dye laser (585–595 nm) targets oxyhemoglobin for port-wine stains; Q-switched lasers target tattoo pigment; 755/810/1064 nm target hair follicles.
- Complications: dyspigmentation, scarring, infection, filler necrosis from intravascular injection.
Worked example
An infant has a facial port-wine stain. Reasoning: pulsed dye laser at 595 nm with a pulse width matched to vessel thermal relaxation time is first-line and is best started early.
Traps
Laser hair removal in tanned skin risks burns and paradoxical hypertrichosis. Do not use Q-switched lasers for tattoo removal without considering ink composition. Filler injection should stop if severe pain suggests vascular occlusion.