What are the causes of cubital tunnel syndrome?

Causes of Cubital Tunnel Syndrome

Cubital tunnel syndrome is primarily caused by compression, stretching, or traction of the ulnar nerve as it passes through the cubital tunnel at the elbow, with repetitive elbow flexion, direct pressure, and anatomical variations being the most common contributing factors. 1

Anatomical and Mechanical Factors

• Elbow Flexion:

  • During elbow flexion, the cubital tunnel volume decreases by up to 55% as the arcuate ligament (Osborne's ligament) elongates 2
  • Intraneural and extraneural pressures can exceed 200 mm Hg with elbow flexion and flexor carpi ulnaris contraction 2
  • The ulnar nerve elongates 4.7-8 mm during elbow flexion, creating traction forces 2

• Anatomical Structures Contributing to Compression:

  • Osborne's ligament (cubital tunnel retinaculum)
  • Humeroulnar arcade
  • Deep flexor/pronator aponeurosis 3
  • Anconeus epitrochlearis muscle (rare anatomical variation) 4

Classification of Causes

Primary Causes

1. Anatomical variations:

   • Presence of anconeus epitrochlearis muscle 4
   • Anterior subluxation of the ulnar nerve 3
   • Shallow retrocondylar groove

2. Mechanical factors:

   • Repetitive elbow flexion (occupational or recreational activities) 5, 1
   • Prolonged elbow flexion (especially during sleep) 2
   • Direct compression on the "funny bone" area 1

Secondary Causes

1. Trauma-related:

   • Elbow fractures or dislocations
   • Post-traumatic scarring
   • Cubitus valgus deformity 3

2. Degenerative changes:

   • Osteoarthritis of the elbow joint 5
   • Osteophyte formation
   • Joint space narrowing

3. Space-occupying lesions:

   • Ganglion cysts
   • Tumors
   • Heterotopic ossification 5

Risk Factors

• Occupational factors:

  • Jobs requiring repetitive elbow flexion
  • Positions that place direct pressure on the elbow
  • Vibration exposure 1

• Medical conditions:

  • Diabetes mellitus (increases nerve susceptibility to compression) 6
  • Rheumatoid arthritis
  • Prior elbow trauma or surgery 3

Pathophysiological Progression

1. Initial stage: Intermittent compression leads to transient symptoms
2. Intermediate stage: Persistent compression causes demyelination
3. Advanced stage: Chronic compression results in axonal damage, leading to muscle atrophy and irreversible changes 1

Clinical Pitfalls and Diagnostic Considerations

• Cubital tunnel syndrome is often underdiagnosed due to patients not seeking treatment for early symptoms 1
• It can be misdiagnosed as C8 radiculopathy, Pancoast tumor, or pressure palsy 3
• Symptoms may worsen at night due to prolonged elbow flexion during sleep
• Early intervention is crucial to prevent irreversible muscle atrophy and hand contractures 7

Understanding these causes is essential for proper diagnosis and management, as treatment approaches vary based on the underlying etiology and severity of compression.