Trapezius Muscle Flap
Lauren M. Mioton
Gregory A. Dumanian
The trapezius muscle flap is a reliable option for coverage of the posterior trunk and for defects of the head and neck.
The trapezius muscle, which has a unique triangular shape, is the most superficial muscle on the posterior neck and thorax (FIG 1).
It is composed of three parts: descending, transverse, and ascending portions.
The descending or superior part originates from the occiput and inserts into the lateral third of the clavicle. It acts to elevate the scapula.
The transverse or middle part originates from the spinous processes of the 1st to 5th thoracic vertebra and inserts into the acromion. It acts to retract the scapula.
The ascending or inferior part originates from the spinous processes of the 6th to 12th thoracic vertebra and inserts into the spine of the scapula. It acts to depress the scapula.
There are three arterial supplies to the trapezius muscle. The relative importance and the origin of these vessels are quite variable.
The upper one-third of the muscle receives its blood predominantly from the transverse cervical artery, which itself is a branch of the thyrocervical trunk or the suprascapular artery almost 80% of the time. It passes through the posterior triangle of the neck to the anterior border of the levator scapulae muscle before dividing into two main branches.
The branch entering the upper trapezius is termed the superficial cervical artery, or the superficial branch of the transverse cervical.
The dorsal scapular artery (DSA) supplies the middle one-third of the trapezius.
In 75% of cases, the DSA originates off the subclavian artery and passes between the upper and middle (or middle and lower) trunks of the brachial plexus before coursing through the rhomboids.
A branch emerging from between the rhomboid muscles serves as the perforator to the inferior trapezius. It also supplies the skin paddle above and lateral to the overlying latissimus.
The third source of blood to the inferior-most trapezius is from segmental, posterior intercostal arteries 3 to 6. Due to these numerous small perforators and a dominant larger perforator, most classify this muscle as Mathes and Nahai type V.
Dominance of one source vessel tends to cause a lack of development of the adjacent vascular territory.
The entry point of the transverse cervical is cephalad and medial in location to the entry point of the DSA.
The trapezius muscle is innervated by the spinal accessory nerve (CN XI).
It accompanies the superficial branch of the transverse cervical artery in the superior portion of the muscle and the dorsal scapular artery in the inferior portion. It crosses superficial to the superficial cervical artery in a majority of cases.
The levator scapulae, rhomboid minor, rhomboid major, and latissimus dorsi muscles all lie deep to the trapezius.
The levator scapulae extend from the 1st to the 4th cervical vertebrae and insert on the superior angle of the scapula.
The rhomboid minor originates from the spinous process of the 6th and 7th cervical vertebrae and inserts into the medial aspect of the scapula.
The rhomboid major begins off the spinous processes of the 1st to 4th thoracic vertebrae and inserts into the medial border of the scapula, below the spine of the scapula.
PATIENT HISTORY AND PHYSICAL FINDINGS
The medical evaluation of patients is based on their preexisting medical conditions. No special considerations are needed for this procedure. Importance of shoulder abduction for work may lead to the choice of an alternate reconstruction.
The skin is examined for scars or previous incision sites. If a previous radical neck dissection or instrumentation of the subclavian artery has been performed, a preoperative evaluation of the transverse cervical artery and the dorsal scapular artery with duplex ultrasound or even arteriogram may be necessary to determine vascular patency.
A functional assessment of the shoulder and arm mobility should be performed with baseline function documented.
Imaging, such as CT or MR angiography, is often not performed in the preoperative evaluation for a trapezius muscle flap.
The trapezius muscle flap can be used for coverage of the posterior back or for soft tissue defects of the head and neck.
The decision to use such a flap should be based on the location of the defect and tissue required.
Smaller defects of the posterior trunk that only require the muscle supplied by the dorsal scapular artery (descending branch) can be performed without significant arm dysfunction, as the upper and middle aspects of the muscle remain present to help with shoulder stability. However, mobilization of the entire muscle to reach the neck, face, and anterior trunk is associated with a sizeable donor site morbidity including limited arm elevation and pain. It should only be considered when other flap options have been eliminated, microsurgery is not an option, or the accessory nerve has already been divided during tumor resection.