Extracranial microanatomic study of supraorbital keyhole approach

The extracranial microanatomic features and tissue protection for supraorbital keyhole approach are described in detail to achieve less invasiveness, which has scant reports and is important for craniofacial surgeons.

Ten formalin-fixed human cadaveric heads were used in 20 sides, by means of an operating microscopic, with microinstruments and magnification ranging from 3x to 16x. The relationship between concerned nerves, muscles, and bone window was identified and measured.

The height from the musculus orbicularis oculi superiorus to the incision on the arch of the eyebrow is 6.9 +/- 1.0 mm. The horizontal distance from the anterior ramus of the temporal branch of the facial nerve to the frontal zygomatic process is 19.5 +/- 3.6 mm. Thus, the supraorbital keyhole approach incision can potentially injure the nerve. However, the lateral branch of the supraorbital nerve is outside the pericranial layer and has no ramus within 10 mm from its emission, and the angle from the lateral branch of the supraorbital nerve to the ridge of the orbit is 74 +/- 3 degrees. Therefore, the supraorbital nerve can be dissected to enlarge the medial region of the bone window. We propose to form the muscle-bone flap to keep adhesion of the temporal muscle and gain cosmetic benefit.

Our microanatomic study of the musculus orbicularis oculi, the temporal branch of the facial nerve, the superior orbital nerve, and the temporal muscle suggests a means to minimize invasiveness and gain cosmetic benefit.