Dermatologic Surgery, Lasers, and Cosmetic Dermatology
Surgical principles
Know excisional techniques (elliptical excision with 3:1 length-to-width ratio, fusiform shape, relaxed skin tension lines), closure types (primary, secondary, flaps, grafts), and haemostasis. Understand anaesthesia (lidocaine with adrenaline, maximum doses, digital precautions), suture selection, and wound care. Complications: dehiscence, hypertrophic scar, keloid, infection, and dog-ear.
Lasers and energy devices
Map lasers to targets: pulsed dye laser (vascular, oxyhaemoglobin), Q-switched lasers (pigment), fractional ablative (CO2, erbium) and non-ablative (1540 nm) resurfacing, and intense pulsed light (broadband). Understand selective photothermolysis: wavelength, pulse duration shorter than thermal relaxation time, and fluence. Fitzpatrick skin type predicts risk of post-inflammatory hyperpigmentation.
Cosmetic dermatology
Know botulinum toxin mechanism (blocks acetylcholine release at neuromuscular junction) and complications; dermal fillers (hyaluronic acid, complications including vascular occlusion); chemical peels (superficial, medium, deep) and their depth; and sclerotherapy.
Traps
- Assuming deeper peel equals better result - depth determines risk.
- Forgetting that Q-switched lasers target pigment but can cause dyspigmentation in darker skin.
- Adrenaline in digits is generally safe in modern practice but exam stems may test traditional caution.
Rule of thumb
For any laser question, apply selective photothermolysis: match wavelength to chromophore, pulse duration to target size, and fluence to desired effect.