Raymond A. Klug, Bradford O. Parsons, and Evan L. Flatow
DEFINITION
Long thoracic nerve palsy leads to classical scapular winging because of weakness of the serratus anterior muscle (FIG 1).
Other types of winging include trapezius winging and rhomboid winging.
Lesions of the long thoracic nerve can range from paresis to complete paralysis, leading to varying degrees of shoulder dysfunction.
The serratus anterior muscle functions to stabilize the scapula against the chest wall, thus providing a fulcrum for the humerus to push against while moving the arm in space.3,4
Without this fulcrum, shoulder elevation is weakened, which leads to inability to use the arm in forward activities.
Forward elevation of the shoulder is most severely affected, followed by shoulder abduction.
ANATOMY
The serratus anterior is a large broad muscle that covers the lateral aspect of the thorax. It has digitations that take origin from the upper nine ribs, pass deep to the scapula, and insert on the medial aspect of the scapula.15
The muscle has three divisions.5
The first division consists of one slip and takes origin from the first two ribs. This division runs slightly upward and inserts on the superior angle of the scapula.
The second division is made up of three slips from the second, third, and fourth ribs, and inserts on the anterior surface of the medial border of the scapula.
The third division, which consists of the inferior five slips from ribs five through nine, inserts on the inferior angle of the scapula. Because this division has the longest course it has the longest lever-arm and the most power for scapular rotation.
The serratus anterior muscle stabilizes the scapula against the chest wall, creating a fulcrum for the proximal humerus to lever against while moving the arm in space.
The serratus anterior protracts and upwardly rotates the glenoid.
Its direction of pull brings the inferomedial border of the scapula anteriorly. The inferior border of the scapula is pulled forward with forward elevation of the arm. This causes the glenoid to tip posteriorly and allow full forward elevation without impingement.
With weakness of the serratus anterior muscle, the scapula translates superiorly and medially, and the inferior border rotates medially and dorsally (FIG 2A).
The serratus anterior muscle is innervated by the long thoracic nerve, which arises from the ventral rami of cervical roots C5–7.
The C5 and C6 roots pass through the scalenus medius muscle and merge before they receive a branch from C7.
The nerve enters the axillary sheath at the level of the first rib and travels posteriorly in the axilla.
It then passes over a prominence in the second rib and descends along the lateral chest wall, where it enters the serratus anterior fascia and then the muscle itself (FIG 2C).5,15
The total length of the nerve is about 24 cm, and there are several possible points of injury.
Proximally, as well as distally along the chest wall, the nerve is susceptible to injury because of its superficial location.
The nerve is tethered in the axillary sheath, which places it on stretch with forward elevation of the arm.
FIG 1 • Clinical photograph of serratus winging.
PATHOGENESIS
Scapular Winging
Scapular winging may be due to primary, secondary, or voluntary causes.8
Primary scapular winging can be divided into neurologic, bony, and soft tissue types.
Neurologic disorders, which are most common, include.
Long thoracic nerve palsy (serratus anterior weakness)
Spinal accessory nerve palsy (trapezius weakness)
Dorsal scapular nerve palsy (rhomboid weakness)
Trapezius weakness winging may be distinguished from serratus winging by the position and direction of scapular laxity (see Fig 2A,B).
Bony abnormalities include osteochondromas of the scapula or fracture malunion.
Soft tissue disorders include.
Soft tissue contractures, causing winging
Muscular disorders such as fascioscapulohumeral dystrophy
FIG 2 • A,B. Resting position of the scapula with serratus anterior and trapezius palsy. C. Superficial location of the long thoracic nerve.
Congenital absence or traumatic rupture of the parascapular muscles
Scapulothoracic bursitis
Secondary winging may occur following disorders of the glenohumeral joint. The most common causes are multidirectional and posterior instability.
The sequence of events leading to secondary scapular winging due to primary shoulder pathology is as follows:
Primary glenulohumeral or subacromial pathology, leading to
Limited glenulohumeral motion, leading to
Increased compensatory scapulothoracic motion, leading to
Increased demand on periscapular muscles, leading to
Fatigue of periscapular muscles—serratus, trapezius, and rhomboids— leading to
Secondary scapular winging
Voluntary winging may occur in psychiatric patients or for secondary gain.
Long Thoracic Nerve Palsy
Long thoracic nerve palsy is the most common cause of serratus dysfunction resulting in symptomatic scapular winging, especially in those patients who fail nonoperative management and are being considered for pectoralis tendon transfer.1
Long thoracic nerve palsy has been reported to result from idiopathic, iatrogenic, viral, compressive, or traumatic (blunt or penetrating) causes.15
Most injuries are neurapraxic, due to blunt trauma.
Lesions also may occur through entrapment of the fifth or sixth cervical roots at the level of the scalenus medius, during traction over the second rib, or with traction and compression at the inferior angle of the scapula with general anesthesia or prolonged abduction of the arm.
Iatrogenic injuries may occur during radical mastectomy, first rib resection, or transaxillary sympathectomy, or during surgical positioning.6
Other less common causes include viral illnesses, ParsonageTurner syndrome, isolated long thoracic neuritis, immunizations, or C7 nerve root lesions.
Often, the cause is idiopathic, with a questionable history of trauma or viral illness.
Pathoanatomy
A mechanical advantage is gained by stabilization of the scapula against the chest wall.
With loss of this mechanical advantage, forward elevation against resistance is decreased owing to scapulothoracic motion.
Additional types of shoulder pathology can result secondary to stabilization of the scapula:
Impingement due to relative anterior rotation of the acromion (FIG 3)
Weakness due to loss of mechanical advantage in forward elevation
Adhesive capsulitis from disuse
With complete paralysis of the serratus anterior, complete forward elevation and abduction greater than 110 degrees are not possible.3,15
NATURAL HISTORY
As mentioned previously, most injuries to the long thoracic nerve are neurapraxic from stretch of the nerve or blunt trauma.
Most cases resolve spontaneously without operative intervention within 12 months, although maximal recovery may take up to 24 months.2,7,9
The exception to this rule is injury due to nerve laceration from penetrating trauma or iatrogenic injury.
PATIENT HISTORY AND PHYSICAL FINDINGS
A thorough history (including previous illnesses, procedures and interventions, hand dominance, and activity level) and complete examination of the shoulder and back are essential.
Treatment often is delayed, and diagnosis may become apparent only after failed treatment for other disorders.
Furthermore, patients may develop secondary stiffness from disuse, and this may be the primary complaint.
Patients often present with vague complaints of shoulder pain or weakness with overhead activities.
Because winging may be subtle, the patient must be undressed from the waist up, viewed from the back, and tested with provocative maneuvers such as resisted forward elevation and pushups against a wall.
Pain may come from several sources, making diagnosis of long thoracic nerve palsy based on pain distribution difficult.
Compensatory overuse of the remaining scapulothoracic musculature may cause pain localized posteriorly about the scapula.
Patients may present with impingement-type pain with forward elevation.
In secondary winging, pain may result from an underlying diagnosis such as glenohumeral instability.
With severe pain, long thoracic neuritis or ParsonageTurner syndrome should be considered.
Physical examination usually reveals classic winging, with the scapula translated medially and the inferior border rotated toward the midline (see Fig 1).
Patients may present with varying degrees of weakness of forward elevation of the arm.
Resisted testing may accentuate winging, as will having the patient do a pushup against a wall.
Weakness of forward elevation may be decreased by manual scapular stabilization against the chest wall by an examiner, the so-called “scapular stabilization test.”13
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain radiographs of the shoulder, cervical spine, and chest should be part of the workup.
Although radiographs rarely are diagnostic, bony abnormalities such as osteochondromas, cervical spondylosis, or scoliosis may be evident.
CT or MRI scans may be helpful in these situations, but are often not necessary.
FIG 3 • Normal and abnormal scapular kinematics and its relationship to subacromial impingement syndrome.
Electromyographic and nerve conduction velocity studies are useful in confirming the diagnosis as well as following patients clinically.
Additionally, in idiopathic cases or where dystrophy is suspected, these tests may be helpful in ruling out other neuromuscular disorders (such as fascioscapulohumeral dystrophy) that may preclude muscle transfer as an option for scapular stabilization.
Serial studies every 3 months are recommended.
Studies should include cervical roots, brachial plexus, and the spinal accessory nerve.
DIFFERENTIAL DIAGNOSIS
Rotator cuff tear
Fracture malunion
Glenohumeral instability
Impingement
Acromioclavicular joint disease
Biceps tendinitis
Neurologic disorders
Suprascapular nerve entrapment
Scoliosis
Scapular osteochondroma
NONOPERATIVE MANAGEMENT
Whether idiopathic, viral, or compressive, almost all cases of serratus winging from long thoracic palsy resolve spontaneously within 1 to 2 years.2,7,9
Without a clear history of penetrating trauma, all patients initially should be treated conservatively (FIG 4).
Physical therapy should consist of range-of-motion exercises to avoid secondary glenohumeral stiffness.
Braces and orthotics that have been designed to stabilize the scapula to the chest wall may provide symptomatic relief. Their use is controversial, however, and many patients find them cumbersome.
Some authors have recommended bracing to decrease continued traction on the nerve.14
SURGICAL MANAGEMENT
Patients for whom nonoperative treatment has failed and who have persistent symptomatic scapular winging are candidates for surgical stabilization.
Patients often are given up to 24 months to recover nerve and muscle function before surgical repair is considered.
However, Fery2 has reported that up to 25% of patients with serratus anterior paralysis may fail nonoperative treatment.
Patients who have penetrating trauma or iatrogenic injury, where a long thoracic nerve transection is suspected, may be indicated for acute nerve exploration and repair.
Historically, three different procedures have been used to treat patients with symptomatic serratus anterior dysfunction: scapulothoracic fusion, static stabilization procedures, and dynamic muscle transfers.
Scapulothoracic fusion is mainly a salvage procedure, sometimes used in patients with previous failures or in patients with dystrophies, such as fascioscapulohumeral dystrophy, where multiple muscles may be affected.
Static stabilization uses fascial slings or tethers to help stabilize the scapula.
These procedures have fallen out of favor because the slings may gradually stretch out, with subsequent loss of scapular stability.
Dynamic muscle transfers, first described by Tubby12 in 1904, have been found to offer the optimal recovery and result in nearly normal scapulothoracic motion.
FIG 4 • Algorithm for treatment of serratus palsy. EMG, electromyography. (Adapted from Kuhn JE. The scapulothoracic articulation: anatomy, biomechanics, pathophysiology, and management. In: Iannotti JP, Williams GR Jr., eds. Disorders of the Shoulder: Diagnosis and Management, ed 2. Philadelphia: Lippincott Williams & Wilkins, 2007:1058–1086.)
Numerous different transfers have been described, but most surgeons currently perform a transfer of the sternal head of the pectoralis major to the inferior angle of the scapula to reconstruct the function of the deficient serratus anterior.
The sternal head of the pectoralis is preferred because it has good excursion and similar power to the serratus, and its fiber orientation is similar to that of the serratus.1,2
Preoperative Planning
Preoperative planning should include a discussion with the patient regarding allograft versus autograft augmentation of the pectoralis transfer.
Typical options include contralateral fascia lata or semitendinosus autograft, or semitendinosus allograft.
A tendon stripper is needed for autograft harvest if desired.
A 5-mm round trip burr or drill bit is needed to fashion a tunnel through the inferior angle of the scapula.
Heavy nonabsorbable suture (no. 2 or no. 5) is needed to attach the pectoralis transfer and prepare the graft augmentation.
Patient Positioning
The patient is placed supine in the beach chair position, with care taken to leave access to the midline posteriorly and anteriorly.
A pad is placed behind the midline of the thorax to improve posterior exposure.
The forequarter is draped free with the entire scapula in the surgical field.
A pneumatic arm positioner (Spider Limb Positioner, Tenet Medical Engineering, distributed by Smith & Nephew Endoscopy, Andover, MA) is helpful during the procedure to maintain position of the extremity.
If fascia lata or semitendinosus autograft is to be harvested, the lower extremity must be prepped and draped free as well.
Approach
The following section describes our preferred technique for transfer of the sternal head of the pectoralis major to the inferior angle of the scapula for serratus anterior dysfunction.
TECHNIQUES
EXPOSURE
A 10to 15-cm incision is made in the axillary crease posterior to the lateral border of the scapula (TECH FIG 1A).
The deltopectoral interval is developed, and the cephalic vein is retracted laterally.
The pectoralis tendon is identified at its humeral insertion.
The sternal head, which lies deep to the clavicular head, is identified and isolated bluntly (TECH FIG 1B,C).
Often, abduction and external rotation of the extremity is helpful in exposing the sternal head.
The sternal head insertion is released sharply from the humerus, taking care not to damage the underlying long head of the biceps tendon or the clavicular head of the pectoralis major (TECH FIG 1D,E).
Traction sutures are placed into the sternal head tendon, and the muscle belly is freed of adhesions medially.
TECH FIG 1 • A. Axillary incision used for pectoralis major transfer. B,C. The sternal head, which lies deep to the clavicular head, is identified and isolated bluntly. (continued)
TECH FIG 1 • (continued) D,E. The sternal head insertion is released sharply from the humerus, taking care not to damage the underlying long head of the biceps tendon or the clavicular head of the pectoralis major. (B–E:from Post M. Orthopaedic management of neuromuscular disorders. In: Post M, Flatow EL, Bigliani LU, Pollack RG, eds. The Shoulder: Operative Technique. Philadelphia: Lippincott Williams & Wilkins, 1998:201–234.)
GRAFT HARVESTING
At this point, attention is turned to the fascia lata harvest, or preparation of the allograft tendon.
For fascia lata harvest, two small incisions (2 to 3 cm) are made on the lateral aspect of the thigh, about 20 cm apart.
After incision, the fascia lata is exposed and cleaned with an elevator between the two incisions.
Once the fascia lata is identified and isolated, a tendon stripper is used to harvest a graft approximately 6 cm × 20 cm.
The graft is then folded over itself and tubularized using heavy, nonabsorbable suture.
Once prepared, the graft is woven into the sternal head tendinous origin and secured with heavy, nonabsorbable suture (TECH FIG 2).
TECH FIG 2 • Once prepared, the graft is woven into the sternal head tendinous origin and secured with heavy, nonabsorbable suture. (From Post M. Orthopaedic management of neuromuscular disorders. In: Post M, Flatow EL, Bigliani LU, et al, eds. The Shoulder: Operative Technique. Philadelphia: Lippincott Williams & Wilkins, 1998:210–234.)
SCAPULAR EXPOSURE, PREPARATION, AND TENDON ATTACHMENT
After the pectoralis tendon and graft are ready, the scapula is exposed.
The inferior angle of the scapula is identified and exposed by blunt dissection along the chest wall.
The latissimus dorsi and teres major tendons are retracted distally, and the lateral neurovascular structures are avoided by staying medial.
Once the inferior angle of the scapula is identified, it is exposed subperiosteally, and a 6to 8-mm burr hole is made 2 cm from the lateral and inferior border of the scapula.
The graft is then passed through the bone hole from anterior to posterior, tensioning the graft while reducing the scapula on the chest wall, so that the native pectoralis tendon is flush with the bone tunnel.
The graft is then looped through the hole in the inferior scapula and sutured to itself using heavy, nonabsorbable suture (TECH FIG 3).
It is necessary to ensure that native pectoralis tendon is brought to the scapula, because the tendon graft may stretch over time.
The wound is then closed in layers over a drain.
The extremity is placed in a sling and a scapulothoracic orthosis, which maintains pressure on the scapula against the chest wall.
TECH FIG 3 • The graft is looped through the hole in the inferior scapula and sutured to itself using heavy, nonabsorbable suture. (From Post M. Orthopaedic management of neuromuscular disorders. In: Post M, Flatow EL, Bigliani LU, et al, eds. The Shoulder: Operative Technique. Philadelphia: Lippincott Williams & Wilkins, 1998:210–234.)
PEARLS AND PITFALLS
POSTOPERATIVE CARE
Patients are kept immobilized in the sling and orthosis for 6 weeks.
After 6 weeks, range-of-motion exercises are begun, and the brace is discontinued.
Strengthening exercises are begun as motion returns.
Patients are restricted from heavy lifting or manual labor for 6 months.
OUTCOMES
Most series of sternal head transfer for serratus anterior dysfunction and scapular winging report good to excellent results with improvement in function, relief of pain, and correction of winging.
Post11 reported on eight patients treated with sternal head transfer with excellent results.
Connor et al1 reported on 11 patients, 10 of whom (91%) had significant improvement in pain and function and relief of winging.
Warner and Navarro13 reported that seven of eight patients had excellent results, with the only unsatisfactory outcome following a deep infection.
Conversely, Noerdlinger et al10 reported that of 15 patients treated, only 7 (47%) had good to excellent results. They found that those patients who lacked external rotation at follow-up had poorer results, and that more aggressive therapy regarding rotation may be needed.
COMPLICATIONS
Seroma and infection13
Neurovascular injury
Scapular fracture through bone tunnel
Shoulder stiffness10
Graft loosening and loss of tension11
REFERENCES
· Connor PM, Yamaguchi K, Manifold SG, et al. Split pectoralis major transfer for serratus anterior palsy. Clin Orthop Relat Res 1997; 341:134–142.
· Fery A. Results of treatment of anterior serratus paralysis. In Post M, Morrey BF, Hawkins R, eds. Surgery of the Shoulder. St. Louis: Mosby-Year Book, 1990:325–329.
· Gregg JR, Labosky D, Harty M, et al. Serratus anterior paralysis in the young athlete. J Bone Joint Surg Am 1979;61A:825–832.
· Inman VT, Saunders JB, Abbott LC. Observations on the function of the shoulder joint. J Bone Joint Surg 1944;26:1–30.
· Jobe CM. Gross anatomy of the shoulder. In Rockwood CA Jr, Matsen FA III, eds. The Shoulder. Philadelphia: WB Saunders, 1998:34–94.
· Kauppila LI, Vastamaki M. Iatrogenic serratus anterior paralysis. Long-term outcome in 26 patients. Chest 1996;109:31–34.
· Kuhn JE, Hawkins RJ. Evaluation and treatment of scapular disorders. In Warner JJ, Iannotti JP, Gerber C. Complex and Revision Problems in Shoulder Surgery. Philadelphia: Lippincott-Raven, 1997:357–376.
· Kuhn JE, Plancher KD, Hawkins RJ. Scapular winging. J Am Acad Orthop Surg 1995;3:319–325.
· Leffert RD. Neurologic problems. In Rockwood CA Jr, Matsen FA III, eds. The Shoulder. Philadelphia: WB Saunders, 1998:965–988.
· Noerdlinger MA, Cole BJ, Stewart M, et al. Results of pectoralis major transfer with fascia lata autograft augmentation for scapula winging. J Shoulder Elbow Surg 2002;11:345–350.
· Post M. Pectoralis major transfer for winging of the scapula. J Shoulder Elbow Surg 1995;4:1–9.
· Tubby AH. A case illustrating the operative treatment of paralysis of the serratus magnus by muscle grafting. Br Med J 1904;2:1159–1160.
· Warner JJ, Navarro RA. Serratus anterior dysfunction. Recognition and treatment. Clin Orthop Relat Res 1998;349:139–148.
· Watson CJ, Schenkman M. Physical therapy management of isolated serratus anterior muscle paralysis. Phys Ther 1995;75:194–202.
· Wiater JM, Flatow EL. Long thoracic nerve injury. Clin Orthop Relat Res 1999;368:17–27.