Injury to the long thoracic nerve typically occurs as a result of a stretching mechanism [1], especially in sports, although the nerve can be injured by compression, or very rarely penetrating trauma. Patients may not notice symptoms until days or weeks later. Usually a loss of upper extremity strength is the chief complaint, although prolonged symptoms may lead to pain from other periscapular muscles, especially the pectoralis minor and levator scapulae, as these muscles are excessively active in an attempt to compensate for the weak serratus anterior.

With serratus anterior weakness, the levator scapulae, rhomboids, and trapezius will dominate pulling the scapula medial and superior (Fig. 12.3a, b). Tenderness may be found at the origins of the levator scapulae (superomedial angle of the scapula) and pectoralis minor (medial aspect of the coracoid). Winging may be accentuated by resisted flexion of the extended arm.

Injury to the long thoracic nerve can be detected by EMG [3]. Findings in the injured nerve include increased latency, with fibrillations and sharp waves in the involved serratus anterior. In addition, a decreased number of motor unit action potentials are noted with voluntary contraction.

The differential diagnosis for scapular winging due to serratus palsy includes static causes of winging (scapular osteochondroma, malunited scapula or rib fracture), muscle injury (serratus or other), or other neurologic injury, including the spinal accessory nerve, the dorsal scapular nerve, and/or the brachial plexus or cervical nerve root injury.

Conservative treatment is recommended as most cases of long thoracic nerve injury are neuropraxic and will recover spontaneously. Because the nerve is so long, however, the recovery may be up to 2 years. Recovery can be followed clinically or via serial EMG studies conducted no more frequently than every 3 months. Approximately 80% of patients do well in the long term with resolution of the winging and normal flexion and abduction; however many patients still have pain at long-term follow-up [4].

Surgical neurolysis of the long thoracic nerve in the supraclavicular region has been reported as a treatment with successful outcomes [5]. Release of the distal part of the nerve has also been reported [6]. It is important to recognize that if neurolysis is performed early, it is unknown if these patients would have recovered spontaneously. The outcomes of neurolysis suggest relatively rapid recovery of the nerve.

In patients in whom the serratus palsy does not recover after 18–24 months, or in those in whom no recovery is noted after 12 months on serial EMG studies, muscle transfer surgery may be offered. Marmor and Bechtol [7] described transfer of the pectoralis major with a fascia lata extension to the inferior angle of the scapula (Fig. 12.4). There has been some concern with the potential for failure with indirect transfers of the tendon, leading some to recommend transfer of the tendon directly to the scapula (direct transfer) [8, 9]. In addition, because the muscle orientation is closer to the serratus, many authors recommend using only the sternal head of the pectoralis major, which reduces scarring and improves cosmesis in the axilla [8, 10]. Elhassan and Wagner [11] has described a variation of this transfer where a portion of the humeral bone is retained on the tendon of the sternal head of the pectoralis major, which allows bony union to the scapula.

Transfer of the sternal head of the pectoralis major to the scapula is helpful, and one can expect good to excellent results in approximately 90% of patients [8, 10, 12, 13]. Failure and recurrence of winging is a known complication and may be less common when the direct transfer is employed [12].

Spinal accessory nerve injuries are almost always iatrogenic [14], typically as a result of a lymph node biopsy or other surgery in the posterior cervical triangle. The diagnosis and treatment are often delayed [14], and injury to this nerve is a common source of malpractice claims [15].

With a palsy of the trapezius, inspection of the patient will demonstrate a loss of the usual webbing of the neck and often a surgical scar over the posterior cervical triangle. The serratus will dominate, and the scapula will rest in a depressed and lateral position (Fig. 12.6a, b). With elevation the medial border of the scapula will wing substantially. This can be accentuated by resisted flexion of the arm.