Introduction

The temporalis muscle flap has limited utility in the routine reconstruction of head and neck defects. The use of this flap has been commonly associated with the reconstruction of maxillectomy defects. The use of the temporalis for these defects has significantly diminished over the past two decades as the role of microvascular flaps have become the mainstay for reconstruction of maxillectomy defects. The temporalis flap remains as one of the reconstructive options for patients with facial paralysis. In these cases, the muscle may be employed to restore dynamic function to the paralyzed face.

The advantage of the temporalis muscle flap is the ease of access to the muscle, the moderate quantity of muscle that can be harvested, and the ability to transfer the muscle to the oral cavity. Because of the limited length of the muscle, and the arc of rotation needed to reach the maxilla, the flap can be brought into the oral cavity by two routes. The first route travels over the zygomatic arch and the other travels under the arch. If the path to the oral cavity is chosen to travel over the arch it will result in a diminished reach of the muscle due to the longer path needed to travel to reach the defect. The alternative route, i.e., under the arch, improves the reach of the muscle but requires an osteotomy of the zygomatic arch and reposition of the arch after the muscle is transferred.

The main disadvantage of the temporalis muscle flap is the resultant hollowing associated with the use of the muscle. In cases where the majority of the muscle is used to reconstruct the defect, the temporal defect can be addressed at the time of surgery with the placement of a temporal implant. One commonly used implant is the Medpor (Stryker, USA) temporal implant. The surgeon can modify the implant to fit the patient’s defect and therefore minimize the hollowing that would otherwise result.

Anatomy

The temporalis muscle is a fan-shaped muscle that originates along the temporal lines of the parietal bone of the skull. The muscle lies within the temporal fossa, is covered by a strong fibrous aponuerotic sheath, the temporalis fascia, and passes medial to the zygomatic arch. Insertions of the muscle are onto the anterior and medial surfaces of the coronoid process and along the anterior ascending ramus of the mandible. The muscle thickness varies from 5 mm along its periphery to 15 mm at the level of the zygomatic arch.¹ The area of muscle that can be harvested measures 10 cm wide and 20 cm long. The temporalis muscle is classified as a Type III² muscle receiving its main vascular supply from the anterior and deep temporal arteries, branches from the second portion of the internal maxillary artery. Both deep temporal arteries have a mean vessel diameter of 1 mm. The minor pedicle to the temporalis muscle is via the middle temporal artery, a branch from the superficial temporal artery that has a mean vessel diameter of 0.5 mm.³ In 1996, Chueng demonstrated the increased vascular contribution of the middle temporal artery to the temporalis muscle.⁴ Paired venae comitantes accompany the named arteries. The innervation to the temporalis muscle, like the other muscles of mastication, arise from the anterior division of the mandibular branch of the trigeminal nerve via the anterior and posterior deep temporal nerves.⁵ The temporalis muscle functions in retraction (posterior horizontal fibers) and elevation (anterior vertical fibers) of the mandible.

Flap harvest

• The patient is positioned with the head rotated to expose the donor side towards the surgeon.
• A decision to shave a strip of the hair along the path of the incision or to shave the entire head will often depend on the gender of the patient. In males, the head is more commonly shaven while in females only a strip of the hair along the path of the planned incision is shaven.
• The incision for the harvest of the temporalis muscle is designed from the pre-auricular area and extends superiorly towards the vertex of the head (Figure 12.1).
• Incision is made along the marked incision line and carried deep to the dermis in the pre-auricular area and deep to the temporoparietal fascia along the scalp.
• The scalp flap is then elevated superficial to the temporalis muscle fascia. This fascia is easily identified by its very white appearance.
• Once the anterior and posterior scalp flaps are elevated, the muscle is exposed up to the temporal crest and as far anteriorly as possible towards the muscle attachment in the anterior temporal crest (Figure 12.2).
• An anterior incision is then made in the muscle and carried down to the bone (Figure 12.3).
• The muscle is elevated from its temporal crest and the posterior incision is made based on the desired width needed to repair the defect.
• The dissection is directed inferiorly towards the pre-auricular area and the insertion of the muscle in the coronoid process and anterior ramus of the mandible. Care should be taken as dissection is carried deep to not traumatize the muscle and injure the deep temporal vessels as they penetrate the muscle near the level of the zygomatic arch.
• Several stay sutures are then placed at the distal end of the muscle to facilitate the rotation of the muscle and minimize trauma to the muscle (Figure 12.4).
• The arc of rotation can be checked to insure reach to the desired defect. In cases where the intent is to reconstruct orbital defects, the rotation can be checked and a subcutaneous tunnel developed to reach the site (Figures 12.5 and 12.6).
• In cases where the muscle is to be transferred into the oral cavity to reconstruct a maxillectomy, the surgeon needs to decide how the muscle transfer will be carried out, i.e., over or under the arch. This can be done after checking the arc of rotation and potential reach (Figure 12.7a–c). A tunnel will need to be created from
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