CHAPTER 21 Incisions
Planning the Direction of the Incision
Although generally considered minor procedures, skin incisions are invasive. They cause permanent changes in skin architecture and carry the potential for deleterious patient outcomes in terms of cosmesis and function. Skin incisions must be made with careful, thoughtful consideration and advance planning.
The physician must obtain an informed consent and ensure that the patient knows the basic complications of pain, bleeding, infection, recurrence, scarring, and distortion of the anatomy. The physician must always consider the patient as a whole being and not simply focus on “the lesion.” Many pitfalls are avoidable if this is kept in mind.
Simple full-thickness skin excisions performed with care usually do not pose a threat to underlying structures. The plane of removal should be at the junction of the adipose tissue and the dermis (Fig. 21-1). Nonetheless, familiarity with the anatomy of the proposed surgical site in regard to underlying nerves, vessels, tendons, bursae, and bony structures is essential. Of special concern are two nerves that lie superficially within the subdermal fat layer: the temporal branch of the facial nerve and the spinal accessory nerve (Figs. 21-2 and 21-3). Injury to the temporal branch of the facial nerve may cause inability to wrinkle the forehead and drooping of the eyebrow on the affected side. Damage to the spinal accessory nerve can lead to loss of use of the trapezius muscle. When performing excisions in these regions, physicians should consider less invasive alternative methods for treating the particular lesion, if possible. If an incisional approach must be used, the patient should be advised of the potential complications.
Figure 21-2 Temporal branch of facial nerve. The nerve lies superficially within a triangle created by a line extending from the tragus to the upper forehead wrinkle area and a line extending from the tragus to the lateral aspect of the eyebrow.
Skin incisions and excisions must take into account static and dynamic skin tension to minimize scarring and maximize function. Langer’s lines of minimal skin tension, in general, lie perpendicular to the long axis of underlying musculature and can usually be demonstrated by pinching together a local area of skin or by having the patient contract the muscles under that area. On the face, wrinkles form along these lines as a result of repeated contraction of the facial musculature. Linear incisions (e.g., for removal of underlying lesions such as lipomas or for incision and drainage) should be oriented parallel to wrinkle lines when possible (parallel to the lines of minimal skin tension). With an elliptical excision, in which a section of overlying skin is removed, the long axis of the ellipse should lie parallel to the lines of minimal skin tension. Standard depictions of Langer’s lines (Fig. 21-4) assist in planning incisions, but lines of minimal tension must be evaluated on each patient individually before a procedure. For the face, the patient’s simulating various facial expressions will aid in demonstrating natural wrinkle lines. It should also be noted that for certain elliptical excisions (especially on the face), the long axis of the excision may need to curve or angle instead of lying entirely in a straight line (Fig. 21-5). Planning incisions along lines of minimal tension decreases the forces on the wound that tend to pull it apart, thereby reducing scar potential. Certain areas, especially the deltoid and sternum, are invariably prone to experiencing transverse traction, with a subsequent wider scar and a higher propensity for keloid formation. Children also have an increased tendency to develop hypertrophic or keloid scars.