BIOANATOMY AND BIOMECHANICS
The forehead extends from the hairline superiorly to the eyebrows inferiorly and merges into the temple laterally at the temporal fossa. The skin of the forehead is moderately sebaceous and varies considerably in mobility from one individual to another. In youth, the forehead is smooth. With age, a series of dynamic horizontal rhytides appears. There is considerable variation in the vertical height of the forehead, with some individuals having a very low hairline and others having a higher hairline and a more prominent forehead (Fig. 12.1).
Natural variation in the height of the forehead. (A) Low hairline and short forehead. (B) High hairline and broad forehead
The forehead is prominent in the perception of appearance. Repairs that result in lines are generally well tolerated, whereas skin grafts are best avoided when feasible. Eyebrow symmetry should be maintained, and this may mean the placement of a vertical rather than a horizontal incision line. While historically the closure of wounds with horizontal linear repairs was favored, for a number of reasons discussed later, vertical incisions are often preferable.
The forehead has a rich vascular supply (Fig. 12.2). From medial to lateral, the forehead is supplied by the dorsal nasal vessels, the supratrochlear system, and the supraorbital artery, all of which are branches of the internal carotid artery. Laterally, the blood supply is from the frontal branches of the superficial temporal artery, itself a branch of the external carotid. The lateral and inferior blood supply anastomoses broadly with vessels from the scalp at the hairline. The main vessels of the medial forehead emerge from bony foramina and ascend just over muscle for a short distance before ascending into the adipose and gradually becoming more superficial as they branch extensively onto the mid and upper forehead.
Vascular supply of the forehead. The medial forehead is mainly supplied by the supratrochlear and supraorbital plexi, whereas the lateral forehead is supplied by branches from the superficial temporal system. There is a wide anastomosis of the arterial supply of the forehead
The sensory innervation of the forehead parallels that of the vascular supply, with rich innervation from the supratrochlear and supraorbital nerves. The nerves run just above the frontalis until they are midway up the forehead, at which point their branches ascend to a more superficial level (Fig. 12.3). Transection of the main nerve branches may lead to temporary or permanent anesthesia and may also result in piercing postoperative pain and long-standing neuralgia. Motor innervation of the forehead comes from the frontal branch of the temporal nerve. This nerve lies deep and lateral on the forehead, running in the muscular fascia. Injury to this nerve, which is far more ...