Long thoracic nerve injuries

1. High-Yield Summary

• Etiology and Innervation: The long thoracic nerve arises from the C5, C6, and C7 anterior rami and supplies exclusive motor innervation to the serratus anterior muscle. Neuropathy abolishes active scapular protraction and upward rotation.
• Pathognomonic Presentation: Manifests as classic medial scapular winging, where the vertebral border and inferior angle lift posterior and migrate medially and superiorly, dramatically accentuated during forward arm elevation and wall push-up testing.
• Diagnostic Benchmarks: Must be differentiated from spinal accessory nerve injury (trapezius palsy), which produces lateral scapular winging, shoulder droop, and asymmetric neck contour. Electrodiagnostic studies (EMG/NCS) serve as the gold standard for confirming denervation, excluding plexopathy or radiculopathy, and tracking reinnervation.
• Conservative Primacy: Expectant nonoperative management (periscapular rehabilitation, preservation of passive glenohumeral motion, and optional dynamic stabilizing bracing) results in spontaneous recovery in 70% to 90% of closed traction and inflammatory palsies over a 12 to 24-month horizon.
• Surgical Reconstruction: Subacute distal neurolysis and decompression may be considered at 6 to 12 months for refractory entrapment. Dynamic pectoralis major transfer (sternal head or complete muscle augmented with semitendinosus autograft to the inferior scapular angle) is the gold standard for irreversible, debilitating winging persisting beyond 18 to 24 months. Scapulothoracic arthrodesis is reserved as a salvage option.

2. Anatomy

The long thoracic nerve (nerve of Bell) possesses an extensive, superficial anatomic trajectory spanning the posterior cervical triangle, thoracic inlet, and lateral chest wall, rendering it uniquely susceptible to traction and surgical trauma.

The nerve arises from the anterior primary rami of the fifth, sixth, and seventh cervical nerve roots (C5, C6, and C7), with occasional contributions from C8. The C5 and C6 roots typically pierce through the substance of the middle scalene muscle, whereas the C7 root passes anterior to the middle scalene before joining the upper components behind the brachial plexus trunks and the first rib.

After crossing the lateral border of the first rib, the nerve enters the axilla posterior to the axillary vessels and brachial plexus cords. It courses inferiorly along the mid-axillary line on the external fascial surface of the serratus anterior muscle, accompanied by the lateral thoracic artery. Along its descent, it emits individual motor twigs to each of the eight or nine fleshy digitations of the serratus anterior. The lower four digitations converge to insert on the anterior aspect of the inferior angle of the scapula, providing the critical mechanical vector for scapular protraction, upward rotation, and stabilization of the vertebral border against the thoracic rib cage.

Neurovascular Danger Zones and Internervous Planes

• Supraclavicular / Scalene Triangle: The nerve is tightly tethered as C5 and C6 traverse the middle scalene muscle. Violent lateral neck flexion with contralateral shoulder depression produces acute traction tethering against scalene muscular fibers.
• First Rib / Thoracic Inlet: The nerve passes adjacent to the first rib, placing it at direct risk during transaxillary first rib resection for thoracic outlet syndrome and anterior scalenectomy.
• Lateral Thoracic Wall: Because the nerve courses superficially on the outer fascial envelope of the serratus anterior, it is vulnerable to direct transection, traction, or thermal cautery injury during axillary lymph node dissection, mastectomy, thoracostomy tube insertion, and chest wall tumor resections.
• Surgical Approaches and Intervals: Reconstructive dynamic pectoralis major transfer utilizes the anterior deltopectoral interval, exploiting the true internervous plane between the deltoid (axillary nerve) and pectoralis major (medial and lateral pectoral nerves). Posteriorly, exposure of the inferior scapular angle requires developing the interval between the latissimus dorsi (thoracodorsal nerve) and the rhomboid major (dorsal scapular nerve).

3. Pathogenesis

Long thoracic nerve dysfunction results from mechanical traction, blunt compression, direct surgical disruption, or post-viral inflammatory neuropathy:

• Traction Injury: The most prevalent non-iatrogenic mechanism. Proximally anchored at the middle scalene and distally tethered along the thoracic wall fascia, sudden forcible depression of the shoulder girdle combined with contralateral lateral neck flexion stretches the nerve across the first and second ribs, exceeding the physiological elastic limit of the perineurium. Repetitive traction occurs in overhead athletes (tennis, swimming, volleyball, javelin, and baseball pitching).
• Direct Compression and Blunt Trauma: Direct blows to the lateral chest wall, heavy load carriage over the shoulders (rucksack palsy compressing the nerve between the pack strap, clavicle, and first rib), or prolonged operative positioning with the arm in extreme hyperabduction and external rotation.
• Iatrogenic Transection or Thermal Injury: Occurs during axillary lymphadenectomy, radical mastectomy, transaxillary first rib resection, chest tube placement, and cardiac or thoracic surgery.
• Neuralgic Amyotrophy (Parsonage-Turner Syndrome): An idiopathic or post-viral immune-mediated inflammatory brachial plexopathy. Patients experience acute, severe, unprovoked periscapular pain lasting days to weeks, which rapidly subsides into profound serratus anterior weakness and scapular winging.

4. Natural History

The epidemiological profile demonstrates bimodal distribution: active athletic individuals aged 15 to 40 years presenting with traction or blunt sports-related injuries, and surgical cohorts presenting with iatrogenic injury following axillary lymph node dissection or thoracic surgery.

Closed traction injuries and neuralgic amyotrophy carry a favorable prognosis when the structural continuity of the epineurium is preserved. Spontaneous clinical and electromyographic recovery occurs in 70% to 90% of closed neuropraxic or axonotmetic injuries within 12 to 24 months. Regeneration occurs at an average rate of 1 mm per day. Due to the 25 to 35 cm distance from the scalene triangle to the lower serratus slips, complete clinical reinnervation requires a protracted observation timeline.

In cases of complete neurotmesis or failed spontaneous recovery, persistent denervation leads to irreversible motor endplate loss, muscle atrophy, and fatty replacement within 18 to 24 months. The chronic loss of serratus anterior protraction disrupts scapulothoracic kinematics, causing secondary subacromial impingement, rotator cuff tendinopathy, glenohumeral instability, and chronic periscapular myofascial pain from compensatory overload of the trapezius and levator scapulae.

5. Clinical Presentation

History

Patients typically report aching, dull periscapular and posterior shoulder pain, frequently referred to the lateral arm or deltoid. Functional complaints include profound difficulty or rapid fatigue with overhead reaching, lifting, or pushing activities, clothing slipping off the shoulder, and an embarrassing posterior deformity caused by the protruding shoulder blade. A detailed chronological history must identify inciting events, including acute sports collisions, heavy pack carrying, recent breast or thoracic surgical procedures, or the hallmark agonizing initial pain episode characteristic of Parsonage-Turner syndrome.

Physical Examination

Physical examination requires bilateral exposure of the shoulder girdles and posterior thorax to evaluate resting symmetry and dynamic scapulothoracic rhythm:

• Resting Posture: At rest, the affected scapula may appear slightly elevated and shifted medially compared to the contralateral side. Subacute cases may display subtle asymmetry of the posterior thoracic contour.
• Wall Push-Up Test: The patient stands at arm’s length facing a wall and performs a push-up with palms flat against the surface at shoulder height. Serratus anterior insufficiency prevents stabilization of the vertebral border against the chest wall, causing the medial border and inferior angle to project prominently posterior and medial (Sensitivity: 95%, Specificity: 98%).
• Resisted Forward Elevation: Active forward flexion in the sagittal plane is restricted, typically limited to 90 to 110 degrees, with marked dynamic winging occurring as the arm enters the scapular plane.
• Scapular Assistance Test (SAT): The examiner manually stabilizes the medial border and assists upward rotation of the scapula while the patient actively elevates the arm. Immediate reduction in impingement symptoms and restoration of painless overhead reach confirms that shoulder pain is secondary to scapular dyskinesis (Sensitivity: 85%, Specificity: 78%).
• Differential Diagnosis with Spinal Accessory Nerve (SAN) Palsy: SAN palsy results in trapezius denervation, producing lateral scapular winging. The scapula displaces laterally and downward, with an associated shoulder droop, asymmetric neckline, and inability to shrug against resistance. Long thoracic nerve palsy produces strictly medial winging with intact trapezius shrug function.

6. Imaging and Diagnostic Studies

The diagnostic workup combines radiographic exclusion of osseous and structural pathology with advanced cross-sectional imaging and electrodiagnostic localization:

• Plain Radiographs: Standard shoulder series (true AP / Grashey, axillary, and scapular Y views) are obtained to rule out glenohumeral degenerative disease, acromioclavicular dislocation, and clavicular malunion. Dedicated thoracic and chest radiographs evaluate rib fractures, past surgical clips, and bony lesions such as scapular osteochondromas, which produce mechanical pseudo-winging.
• Dynamic Ultrasonography: Enables real-time evaluation of serratus anterior muscle slip thickness and contraction during active push-up maneuvers, allowing comparison with the contralateral unaffected side.
• Magnetic Resonance Imaging (MRI): High-resolution MRI of the brachial plexus and thoracic chest wall identifies muscle denervation patterns. In acute and subacute phases, fluid-sensitive STIR and T2-weighted sequences demonstrate hyperintense muscle edema throughout the serratus anterior slips. In chronic denervation (>12 months), T1-weighted images reveal muscle atrophy and fatty infiltration, signaling poor prognosis for spontaneous neural recovery. Shoulder MRI simultaneously evaluates concomitant rotator cuff pathology.
• Electromyography and Nerve Conduction Studies (EMG/NCS): The definitive diagnostic gold standard. Needle EMG performed 3 to 4 weeks post-injury reveals membrane instability with positive sharp waves and fibrillation potentials in the serratus anterior. Serial testing at 3 to 6-month intervals assesses motor unit action potential (MUAP) morphology and voluntary recruitment. EMG of the cervical paraspinal muscles, rhomboids (dorsal scapular nerve), and trapezius (spinal accessory nerve) is mandatory to rule out C5-C7 cervical radiculopathy and diffuse brachial plexopathy.

7. Classification

Scapular winging is classified by anatomical etiology and dynamic directional displacement, dictating definitive surgical intervention and distinguishing neuromuscular deficits from structural abnormalities.

8. Treatment

Medical and Nonoperative Treatment

Nonoperative therapy represents the cornerstone of management for all closed, traction, blunt traumatic, and post-viral neuropathies:

• Observation Window: A structured 12 to 24-month observation period is mandatory for closed injuries, with serial clinical and electrodiagnostic evaluations scheduled every 3 to 6 months to monitor motor unit recruitment.
• Physical Therapy Protocol: Maintenance of full passive glenohumeral range of motion is paramount to prevent secondary adhesive capsulitis and subacromial contracture. Periscapular strengthening emphasizes the upper, middle, and lower trapezius, rhomboids, and levator scapulae to develop compensatory stabilizing vectors. Provocative resistive overhead loading and aggressive push-ups must be avoided during the denervation phase.
• Dynamic Orthotic Bracing: Specialized scapular stabilization braces (such as the modified Marin brace) utilize an anteriorly directed compressive pad over the inferior angle, stabilizing the scapula against the thoracic wall and facilitating forward elevation during early rehabilitation.
• Pharmacotherapy: Oral anti-inflammatory agents (NSAIDs) for periscapular discomfort; short-course oral corticosteroids during the acute phase of Parsonage-Turner syndrome; and neuropathic agents (gabapentin, pregabalin) for dysesthetic burning nerve pain.

Operative Treatment

Surgical intervention aims to restore dynamic scapulothoracic kinematics, abolish posterior medial winging, resolve secondary impingement pain, and restore functional overhead reach:

• Distal Neurolysis and Nerve Decompression: Indicated in subacute presentations (6 to 12 months post-injury) where electrodiagnostic studies demonstrate incomplete conduction block or persistent focal compression along the supraclavicular triangle or chest wall fascia. Surgical release of constricting fascial bands and external neurolysis restores microvascular perfusion.
• Acute Nerve Repair and Nerve Transfers: For open penetrating trauma or recognized intraoperative transection, immediate primary epineurial microvascular repair or cable autografting (sural nerve) is indicated. In early proximal injuries (<9 months), motor nerve transfers (such as a branch of the thoracodorsal nerve or medial pectoral nerve to the long thoracic nerve) have demonstrated successful reinnervation in specialized centers.
• Dynamic Pectoralis Major Transfer: The gold standard reconstructive procedure for chronic, irreversible long thoracic nerve palsy. The sternal head (or whole muscle) of the pectoralis major is released from its humeral insertion and elongated using an autologous graft (hamstring semitendinosus/gracilis or fascia lata). The tendon construct is passed subpectorally beneath the latissimus dorsi and anchored through transosseous tunnels to the inferior angle and vertebral border of the scapula. The transfer is tensioned with the arm held in 30 degrees of abduction and the scapula held flush against the chest wall in full protraction.
• Scapulothoracic Arthrodesis: A static salvage option reserved for failed dynamic muscle transfers, combined multi-nerve paralysis (concomitant serratus and trapezius deficiency), or generalized muscular dystrophy (FSHD). The medial scapular border is fused to the third through sixth ribs using dual reconstruction plates and autologous or allograft bone.

Indications and Contraindications

• Indications for Dynamic Tendon Transfer: Symptomatic, debilitating medial scapular winging persisting beyond 18 to 24 months; EMG/NCS confirmation of absent motor unit recruitment and chronic serratus anterior denervation; normal passive glenohumeral range of motion; and intact 5/5 pectoralis major strength.
• Indications for Early Exploration: Acute sharp, penetrating trauma with immediate post-injury winging, or recognized surgical transection during axillary or thoracic surgery.
• Contraindications: Glenohumeral adhesive capsulitis or fixed joint contracture (passive motion must be fully restored prior to tendon transfer); active surgical site infection; generalized progressive neuromuscular disorders (relative contraindication for tendon transfer; indication for arthrodesis); and patient inability to adhere to post-operative immobilization and protracted rehabilitation.

9. Outcome

Nonoperative management achieves complete or functionally satisfactory spontaneous recovery in 70% to 90% of closed neuropraxic and traction injuries, with resolution of periscapular pain and return of normal forward elevation within 12 to 24 months.

For patients undergoing dynamic pectoralis major transfer for chronic palsy, data demonstrate reliable functional restoration and pain relief. Active forward elevation improves by an average of 40 to 45 degrees (increasing from pre-operative baselines of 110 degrees to post-operative arcs exceeding 150 degrees). Validated patient-reported outcome measures show substantial improvements, with ASES scores increasing from mean baselines of 48 points to over 80 points postoperatively. Long-term prospective and retrospective cohort analyses confirm that functional stability and pain relief remain durable beyond 15 to 17 years of follow-up.

In patients selected for distal long thoracic nerve neurolysis and decompression during the subacute window, clinical series document complete or substantial resolution of winging in 80% to 86% of cases, accompanied by rapid alleviation of periscapular dysesthesias and improved endurance.

10. Complications

Complications following operative reconstruction are categorized by chronological onset and severity:

11. Pearls and Pitfalls

Execution of surgical decision-making and dynamic reconstruction requires adherence to several clinical principles:

• Differentiate Winging Directions: Never proceed to surgery without definitively verifying whether winging is medial or lateral. Transferring the pectoralis major for trapezius palsy (lateral winging) destabilizes the shoulder girdle and causes severe functional impairment.
• Respect the Reinnervation Clock: Avoid premature tendon transfer prior to 18 to 24 months in closed neuropraxic or post-viral etiologies. Spontaneous axonal regeneration occurs over a protracted timeline and may yield complete recovery without surgical reconstruction.
• Tensioning Parameters: When securing the autograft-augmented pectoralis major tendon to the inferior angle, tensioning must be performed with the arm held in 30 degrees of abduction and slight internal rotation while an assistant holds the scapula pressed firmly against the thoracic wall in maximal protraction and downward flush contact.
• Cortical Fixation Integrity: Do not suture the transfer exclusively to the thin periosteum of the scapula. Drill multiple transosseous bone tunnels through the thickened cortical bone of the inferior angle, or use high-strength cortical suture anchors to prevent catastrophic pullout.
• Wide Submuscular Tunnel: Create a generous subpectoral and sublatissimus subcutaneous tunnel (at least 3 to 4 fingerbreadths in width) to prevent strangulation or compression of the transferred pectoralis muscle belly and preserve its vascular pedicle.

12. Controversy

Several clinical dilemmas continue to stimulate debate in the management of long thoracic nerve injuries:

• Timing of Decompression vs. Expectant Observation: Traditional orthopedic practice mandates waiting 18 to 24 months before surgical intervention to allow full opportunity for spontaneous neural regeneration. Conversely, peripheral nerve surgeons advocate early distal neurolysis and decompression at 6 to 9 months for refractory cases with documented conduction block, demonstrating high rates of prompt motor recovery and preventing prolonged muscle atrophy.
• Sternal Head vs. Whole Pectoralis Major Transfer: Transferring only the sternal head preserves the clavicular head, thereby maintaining the anterior axillary fold contour and assisting with forward elevation. However, some reconstructive surgeons advocate transferring both the sternal and clavicular heads to maximize contractile power and scapular stabilization in heavy manual laborers.
• Graft Selection (Hamstring Autograft vs. Synthetic Mesh vs. Allograft): Hamstring semitendinosus autograft remains the benchmark for tensile strength and biological integration. However, synthetic tapes and acellular dermal matrices eliminate donor site knee morbidity and shorten operative time, though long-term concerns regarding foreign-body reaction and mechanical creep persist.

13. Evidence-Based Synthesis

Modern clinical decision-making is grounded in high-quality randomized controlled trials and prospective registry analyses, corroborated by seminal biomechanical and anatomical descriptions.

14. References

• Nath RK, Somasundaram C. Meta-Analysis of Long Thoracic Nerve Decompression and Neurolysis Versus Muscle and Tendon Transfer Operative Treatments of Winging Scapula. Plast Reconstr Surg Glob Open. 2017. doi:10.1097/GOX.0000000000001481 [Level I: Systematic Review & Meta-Analysis]
• Geurkink TH, Marang-van de Mheen PJ, Robbers T et al. Long-term outcomes of pectoralis major transfer for scapular winging due to long thoracic nerve palsy: results after a median follow-up of 17 years. JSES Int. 2024. doi:10.1016/j.jseint.2024.04.002 [Level IV: Long-Term Retrospective Cohort]
• Chalmers PN, Saltzman BM, Feldheim TF et al. A comprehensive analysis of pectoralis major transfer for long thoracic nerve palsy. J Shoulder Elbow Surg. 2015. doi:10.1016/j.jse.2014.12.014 [Level IV: Retrospective Multicenter Cohort]
• Roulet S, Bernier D, Le Nail LR et al. Neurolysis of the distal segment of the long thoracic nerve for the treatment of scapular winging due to serratus anterior palsy: a continuous series of 73 cases. J Shoulder Elbow Surg. 2022. doi:10.1016/j.jse.2022.02.039 [Level IV: Continuous Prospective Cohort]
• Wiater JM, Flatow EL. Long thoracic nerve injury. Clin Orthop Relat Res. 1999. doi:PMID:10613149 [Level V: Seminal Instructional Review]

15. Master Class Pro-Tip

When evaluating suspected serratus anterior palsy, always perform the dual-maneuver clinical exam to differentiate medial from lateral scapular winging before ordering electrodiagnostics. Medial winging (long thoracic nerve injury) is dramatically accentuated during active forward elevation and the wall push-up test as the serratus anterior fails to protract the vertebral border. Conversely, lateral winging (spinal accessory nerve injury) is highlighted during active shoulder abduction and external rotation as the trapezius fails to elevate and retract the acromion.

During dynamic pectoralis major transfer with semitendinosus autograft, weave the graft through the tendon with non-absorbable locking sutures and secure it transosseously through the thickened triangular bone of the scapular inferior angle while pinning the scapula in maximal protraction and flush chest-wall contact. Verifying full passive glenohumeral motion prior to transfer is imperative; unrecognized adhesive capsulitis will inevitably overload the reconstruction and cause catastrophic fixation failure.

Master Class Surgical Pearl: Scapular Winging Differential and Tendon Transfer Tensioning