Definition

Scapular winging refers to prominence of the vertebral (medial) border of the scapula. The inferomedial border can also be rotated or displaced away from the chest wall. This well-defined medical sign was first described by Velpeau in 1837. It is associated with a wide array of medical conditions or injuries that typically result in dysfunction of the scapular stabilizers and rotators and, ultimately, glenohumeral and scapulothoracic biomechanics.

Scapular winging is classified as either static or dynamic based on the examination of 25 patients with 23 different causes of scapular winging. Static winging is attributable to a fixed deformity in the shoulder girdle, spine, or ribs; it is characteristically present with the patient’s arms at the sides. Dynamic winging is ascribed to a neuromuscular disorder; it is produced by active or resisted movement and is usually absent at rest. Scapular winging has also been classified anatomically according to whether the etiology of the lesion is related to nerve, muscle, bone, or joint disease ( Table 18.1 ).

The scapula is a triangular bone that is completely surrounded by muscles and attaches to the clavicle by the coracoclavicular ligaments and acromioclavicular joint capsule. Motion of the scapula along the chest wall occurs through the action of the muscle groups that originate or insert on the scapula and proximal humerus. These muscles include the rhomboids (major and minor), trapezius, serratus anterior, levator scapulae, and pectoralis minor. The rotator cuff and deltoid muscles are involved with glenohumeral motion. Innervation of these muscle groups includes all the roots of the brachial plexus and several peripheral nerves. Scapular winging may be caused by brachial plexus injuries, but most often is related to a peripheral nerve injury (see Table 18.1 ).

Injury to the long thoracic and spinal accessory nerves with weakness of the serratus anterior and trapezius muscles, respectively, is most commonly associated with scapular winging. The serratus anterior muscle originates on the outer surface and superior border of the upper eighth or ninth ribs and inserts on the costal surface of the medial border of the scapula. It abducts the scapula and rotates it so the glenoid cavity faces cranially and holds the medial border of the scapula against the thorax.

The serratus anterior muscle is innervated by the pure motor long thoracic nerve (LTN), which arises from the ventral rami of the fifth, sixth, and seventh cervical roots. The nerve passes through the scalenus medius muscle, beneath the brachial plexus and the clavicle, and over the first rib. It then runs superficially along the lateral aspect of the chest wall to supply all the digitations of the serratus anterior muscles. Because of its long and superficial course, the LTN is susceptible to both traumatic and nontraumatic injuries ( Fig. 18.1 ).

Anterolateral view of the right upper chest and shoulder showing the course of the long thoracic nerve and innervation of the serratus anterior muscles. Note the superficial location of the long thoracic nerve.

From the Mayo Foundation for Medical Education and Research. © Mayo Foundation, 2007.

The trapezius muscle consists of upper, middle, and lower fibers. The upper fibers originate from the external occipital protuberance, superior nuchal line, nuchal ligament, and spinous process of the seventh cervical vertebra and insert on the lateral clavicle and acromion. The middle fibers arise from the spinous process of the first through fifth thoracic vertebrae and insert on the superior lip of the scapular spine. The lower fibers originate from the spinous process of the sixth through twelfth thoracic vertebrae and insert on the apex of the scapular spine. They are innervated by the pure motor spinal accessory nerve (cranial nerve XI) and afferent fibers from the second through fourth cervical spinal nerves. The root fibers unite to form a common trunk that ascends to enter the intracranial cavity through the foramen magnum. It exits with the vagus nerve through the jugular foramen, pierces the sternocleidomastoid muscle, and descends obliquely across the floor of the posterior triangle of the neck to the trapezius muscle. In the posterior triangle, the nerve lies superficially, covered only by fascia and skin, and is susceptible to injury. Cadaver studies have shown considerable variations in the course and distribution of the spinal accessory nerve in the posterior triangle and in the nerve’s relationship to the borders of the sternocleidomastoid and trapezius muscles. The trapezius muscle adducts the scapula (middle fibers), rotates the glenoid cavity upward (upper and lower fibers), and elevates and depresses the scapula. Overall, the trapezius muscles maintain efficient shoulder function by both supporting the shoulder and stabilizing the scapulae ( Fig. 18.2 ).

Lateral view of the neck showing the course of the spinal accessory nerve and innervation of the trapezius muscle.

From the Mayo Foundation for Medical Education and Research. © Mayo Foundation, 2007.

A rare cause of scapular winging is dorsal scapular nerve palsy. The dorsal scapular nerve is a pure motor nerve from the fifth cervical spinal nerve that supplies the rhomboid and levator scapulae muscles. It arises above the upper trunk of the brachial plexus and passes through the middle scalene muscle on its way to the levator scapulae and rhomboids. The rhomboids (major and minor) adduct and elevate the scapula and rotate it so the glenoid cavity faces caudally.

The levator scapulae muscles originate on the transverse process of the first four cervical vertebrae and insert on the medial borders of the scapulae between the superior angle and the root of the spine. They elevate the scapulae and assist in rotation of the glenoid cavity caudally. They are innervated by the dorsal scapular nerve (emanating from the fifth cervical spinal nerve) and the cervical plexus (emanating from the third and fourth cervical spinal nerves) ( Fig. 18.3 ).

View of upper back showing origins and insertions of rhomboid, levator scapulae, and trapezius muscles.

From the Mayo Foundation for Medical Education and Research. © Mayo Foundation, 2007.

Symptoms

A patient’s presenting symptoms depend on the type and chronicity of the injury. Most patients, however, complain of upper back or shoulder pain, muscle fatigue, and weakness with use of the shoulder. The diagnosis of scapular winging is made clinically, but can be difficult to make, especially when the presenting symptoms and physical examination direct the practitioner towards more common neck and shoulder conditions. A pain profile should be obtained, including onset and duration of pain, location, severity, and quality as well as exacerbating and relieving factors, not only to provide baseline information but also to help develop a differential diagnosis. The patient should also be questioned about hand dominance because the dominant shoulder is usually more muscular but sits lower than the nondominant shoulder. Knowledge of the patient’s age, occupation and hobbies, and current and previous level of functioning may also contribute to the diagnosis and treatment plan. The mechanism of injury in patients with traumatic palsy is important, as are associated findings including muscle spasm, paresthesia, and muscle wasting or weakness. The scapular winging of long thoracic neuropathy and serratus anterior muscle weakness must be distinguished from that of a spinal accessory neuropathy and trapezius muscle weakness as well as dorsal scapular neuropathy and rhomboid weakness. Serratus anterior muscle dysfunction is the most common cause of scapular winging. Typically, patients complain of a dull aching pain in the shoulder and periscapular region. The periscapular pain may be related to spasm from unopposed contraction of the other scapular stabilizers in the presence of serratus anterior muscle weakness. There may be “clicking” or “popping” noise emanating from the periscapular area when the patient moves, which is made worse with stressful upper extremity activities. Because the serratus anterior muscle rotates the scapula forward as the arm is abducted or forward flexed above the shoulder level, these movements are affected. Shoulder fatigue and weakness are related to loss of scapular rotation and stabilization.

A cosmetic deformity may occur in the upper back as a result of the winged scapula. It may be apparent at rest, but usually is more obvious on raising of the arm. Patients may find it difficult to sit for prolonged periods with the back resting against a hard surface, such as driving for long periods.

With trapezius muscle weakness, the affected shoulder is depressed, and the inferior scapular border rotates laterally, which makes prolonged use of the arm painful and tiresome. Patients often complain of a dull ache around the shoulder girdle and difficulty with overhead activities and heavy lifting, especially with shoulder abduction greater than 90 degrees.