What nerve is most likely to be injured from carrying heavy bags at the shoulder for a long time?

Axillary Nerve Injury from Carrying Heavy Bags at the Shoulder

The axillary nerve is the most likely nerve to be injured from carrying heavy bags at the shoulder for a long time. This injury occurs due to direct compression of the nerve as it passes through the quadrilateral space under the shoulder joint 1.

Mechanism of Injury

The axillary nerve is particularly vulnerable to injury from carrying heavy bags at the shoulder due to:

• Direct pressure from the weight of bags on the nerve as it wraps around the surgical neck of the humerus 2
• Compression against the subscapular artery, which can create a "dumbbell-shaped neuroma-in-continuity" in severe cases 1
• Repetitive microtrauma from the straps of heavy bags pressing on the shoulder 3

The position of the arm when carrying bags creates additional strain on the nerve:

• When the arm is flexed at the shoulder with elbow extended, it should only move approximately 45° away from midline before straining the shoulder 2
• Carrying heavy bags often forces the shoulder beyond this optimal range, increasing pressure on the axillary nerve

Clinical Presentation

Patients with axillary nerve injury from carrying heavy bags typically present with:

• Pain in the lateral aspect of the shoulder
• Weakness in shoulder abduction
• Difficulty with external rotation of the arm
• Sensory disturbances over the "regimental badge" area (lateral aspect of shoulder)
• Atrophy of the deltoid muscle in chronic cases

Diagnostic Approach

1. Physical examination:

   • Test deltoid muscle strength (shoulder abduction)
   • Assess sensation over lateral shoulder
   • Look for deltoid atrophy

2. Imaging studies:

   • MRI neurography is most appropriate for visualizing nerve injuries 2
   • 3-T MRI provides high resolution to delineate nerve discontinuities or neuromas 2

3. Electrodiagnostic studies:

   • EMG/NCS to confirm axillary nerve involvement
   • Helps differentiate from other shoulder pathologies

Management

1. Conservative management (first 3-6 months):

   • Avoid carrying heavy bags on the affected shoulder
   • NSAIDs for pain management
   • Physical therapy focusing on:
     • Gentle range of motion exercises
     • Progressive strengthening of deltoid and rotator cuff muscles
     • Scapular stabilization exercises

2. Surgical intervention (if no improvement after 3-6 months):

   • Nerve decompression
   • In severe cases with neuroma formation, resection and nerve grafting may be required 1

Prognosis

• Most cases of axillary nerve injury from bag carrying have good prognosis with conservative management
• Recovery time varies from weeks to months depending on severity
• Complete recovery is possible in most cases if the compression is relieved early
• Chronic compression may lead to permanent nerve damage and muscle atrophy

Differential Diagnosis

Other nerves that may be affected by carrying heavy bags include:

• Suprascapular nerve (affecting supraspinatus and infraspinatus muscles) 4, 5
• Long thoracic nerve (causing scapular winging)
• Musculocutaneous nerve (affecting biceps function)
• Spinal accessory nerve (affecting trapezius function) 6

Prevention

• Use bags with wider, padded straps to distribute pressure
• Alternate shoulders when carrying heavy loads
• Take frequent breaks when carrying heavy items
• Maintain proper shoulder posture and ergonomics
• Strengthen shoulder muscles to improve resilience

Remember that early recognition and intervention are crucial to prevent permanent nerve damage and ensure optimal recovery of shoulder function.