Skin excisions general

Skin tension lines:

• Types of tension lines:
  • Biodynamic excisional skin tension (BEST) lines were derived using tensiometer data to show optimal orientation of a skin excision to minimise tension across its closure
  • Cleavage lines (including Langer lines) were derived from experiments on cadavers determining the shape of wounds
  • Wrinkle lines are based on observational data of wrinkles in elderly people. They do not always align with tension lines, especially on chin, dorsum of nose, and the area lateral to the eyes.
  • Relaxed skin tension lines are produced by positioning the body so that the skin is relaxed, then gently pinching the skin to reveal a crease. These differ from Langer lines, since they are tested on living people. On the face, they often go at right angles to Langer lines.
• The best guide to orientating excisions is found using relaxed skin tension lines, BEST lines, and lines following the direction of stretch marks.
• Scars parallel to Langer's lines and relaxed skin tension lines look better
• Note that some types of lesions will naturally grow with their long axes aligned with skin tension lines - for example, ovoid seborrheic keratoses are generally aligned.
• Long axis of ellipses should be oriented along skin tension lines, with a ratio of 3-4:1 of length to width.
• If lines meet at 30 degrees or less, should be able to avoid dog ears

Preventing incomplete excisions

• Never compromise excision for the sake of reconstruction
• Mark prior to LA - the extent of induration is the extent of the lesion
• See separate topics for specific margins required
• Don't change the line of excision once it has been marked, except to increase it
• Check the bottom of the lesion once it has been excised - if there isn't a mobile bottom layer, re-excise a deeper shave

Circular excisions

• Often the easiest way, especially when there isn't a clear best way beforehand
• Excise the lesion then use skin hooks to determine the best orientation of closure
  • Whichever way requires less tension and has less rounded apexes is generally better
  • If there is too much tension on the wound, or surrounding anatomical structures are distorted, need to move on to flap or graft. Usually need to remove all sutures and start again with flap. The flap will be larger than you expect, even if the wound almost closes primarily.
• Watch out for pantographic expansion - the slight increase in length of the wound when you pull the circle closed. This can 'push' other structures out of the way. This can only be reduced by adding an elliptical incision at right angles and doing a kind of advancement flap.
• Excise the dog ears after placing the first few sutures in the middle

Other considerations:

• Sutures should be removed 5-7 days later on the face, or 10-14 days later in other locations
• Prophylactic antibiotics are unnecessary
• Patients can continue their anticoagulants
• Platelets should be >50 and INR <3

Dealing with positive margins

• Re-excise when possible
  • Especially SCC positive at any margin, melanoma positive at any margin
  • BCC positive at deep margin should be re-excised
  • If a flap was used, generally take it down as soon as possible, and re-excise the relevant area. If it's left for a while, will need to take the deeper part of the flap too.
  • If the margin was macroscopically normal at original surgery, and was performed by an experienced skin cancer surgeon, it is very hard to establish where the tumour is. Either a large re-excision will need to be done or the patient should have Moh's micrographic surgery with a plastic surgeon.
• Radiotherapy - where adequate excision may cause unacceptable cosmetic deformity, patient does not want further surgery, or as a primary treatment in non-surgical candidates
• Observation may be considered in some patients
  • Pre-malignant lesions
  • BCCs positive at a lateral margin (not a deep one) - recurrence rate about 50%, but it will be visible

Simple excision

• Can do either fusiform ellipse (A) or tangent-to-circle (B)
• Consider slightly offsetting the opposing tangents if doing (B) so that you don't get a small gap at the opposite apices

Dog ears

• A consequence of closing a rounded defect in a straight line. Redundant skin accumulates at either end and produces a bulge - a relative looseness, not an excess skin
• Tends to subside over time as the centre of the scar relaxes
• Can be reduced by extending the excision in the direction of closure, at the cost of a longer scar
• Decide between making a longer scar, and leaving a dog ear that may not fully resolve
  • Children get more hypertrophic scars and better remodelling, so better to leave it
  • Elderly patients don't remodel much and rarely get hypertrophic scars, so better to fix it
• Can also excise some extra subcutaneous fat at either end to flatten it out a bit

Lesion excision along convex surfaces: Lazy S repair

• Elongates the length of the scar, but avoids puckering or buckling in the middle