Posterolateral Corner Injuries
November 10, 2020

Ulnar Nerve Entrapment

Ulnar Nerve Entrapment

 

Case:

A 27 year old, right hand dominant male presents with a two month history of numbness and tingling in his left hand. He is unable to recall any specific trauma or prolonged compression to his wrist or elbow. He describes weakness holding onto dishes as well as intermittent shooting pain from his elbow and down the inside of his forearm. He has also noticed that his 4th and 5th fingers are bending on their own. 

 

Introduction: 

 

The ulnar nerve is the largest branch of the medial cord of the brachial plexus. It is derived from the anterior division of C8 and T1. It also received some fibres from the lateral cord and the middle trunk. (See Figure 1).

Figure 1 – Brachial Plexus

The ulnar nerve courses from the brachial plexus, through the axilla, down the triceps, into the forearm, and distally into the hand. Along this course there are multiple sites of potential compression. 

 

In this review, we will discuss the presentation, diagnosis, and management of the syndromes associated with the two most common sites of compression. 

 

  1. Cubital Tunnel Syndrome
  2. Ulnar Tunnel (Guyon Canal) Syndrome

 

Definitions and Epidemiology: 

 

Cubital Tunnel Syndrome

 

Cubital Tunnel Syndrome (CTS) is caused by compression and traction of the ulnar nerve at the elbow. It is the second most common upper extremity neuropathy. Incidence is cited at 25 per 100,000 person-years in men and 19 per 100,000 person-years in women. 

 

Ulnar Tunnel (Guyon Canal) Syndrome

 

Ulnar Tunnel Syndrome (UTS) occurs when there is entrapment of the ulnar nerve at the level of the wrist. Specifically, this occurs near the level of the Guyon Canal, the fibro-osseous tunnel where the ulnar nerve travels between the hamate bone and pisiform. The nerve can become compressed proximal, at, or distal to the Guyon Canal. The location of the compression determines whether the patient will present with motor, sensory, or combined deficits.

 

Anatomy

 

Proximal to the Guyon Canal

 

Axilla to Elbow: 

  • Distal to axilla → anterior compartment → medial intermuscular septum → posterior compartment along medial head of triceps → posterior to medial epicondyle → cubital tunnel. 

Elbow to Wrist: 

  • Between FDP & FCU (with ulnar artery) → dorsal cutaneous branch emerges 6-8 cm proximal to distal ulna and travels dorsally → palmar cutaneous branch emerges 10-20cm distal to medial epicondyle

 

At the Guyon Canal

  • Borders of the Guyon Canal/Ulnar Tunnel
    • Ulnar and Proximal: Pisiform
    • Radial and Distal: Hook of Hamate 

 

Distal to the Guyon Canal

  • Exiting the canal motor fibers leave the trunk and superficial sensory fibres continue distally

 

Function of Ulnar Nerve

  • Motor
    • Flexor muscles of the forearm: 
      • Flexor Carpi Ulnaris
      • Flexor Digitorum Profundus (medial half)
    • Intrinsic hand muscles
      • Superficial branch: palmaris brevis muscle 
      • Deep branch: hypothenar muscles, opponens digiti minimi, interosseous muscles, third and fourth lumbricals, adductor pollicis and medial head of the flexor pollicis brevis. 
  • Sensory (3 branches)
    • Palmar cutaneous branch – medial half of the palm.
    • Dorsal cutaneous branch – dorsal surface of the medial one and a half fingers, and the associated dorsal hand area.
    • Superficial branch – palmar surface of the medial one and a half fingers.
      Figure 2 – Ulnar nerve dermatomes in hand

 

Presentation

 

Symptoms: 

 

Cubital Tunnel Syndrome: 

  • Altered sensation on the volar and dorsal aspect of the 4th and 5th digits
    • Exacerbated with prolonged elbow flexion both occupational and athletic activities
  • Hand weakness and loss of coordination during fine motor skills (eg. clipping nails)
  • Pain at the posteromedial elbow, along the medial aspect of the forearm and into the hand
  • Symptoms are typically worse at night due to sleeping with the elbow flexed

 

Ulnar Tunnel Syndrome

  • Common etiologies: 
    • Soft tissue tumors (eg. ganglion cysts)
    • Trauma (eg. hook of hamate fracture, repetitive forces such as racquet and club sports, long distance cycling, etc.)
    • Anomalous muscles and fibrous bands
    • Arthritic, Synovial, Endocrine, and Metabolic Conditions
    • Iatrogenic Injury
  • Symptoms are dependent on the site of compression. This is classified into 3 Zones
    • Zone 1 (within Guyon Canal): mixed motor and sensory findings
    • Zone 2 (deep motor branch): motor deficits only
    • Zone 3 (superficial sensory branch): sensory deficits only
      Figure 3 – Ulnar Nerve Zones of hand

Physical Examination:

  • Inspection:
    • Inspect entire limb for signs of trauma, masses, deformity, and atrophy
    • Muscle atrophy: First dorsal interosseous muscle (injury at elbow), hypothenar muscles (injury at wrist)
    • Ulnar nerve subluxation at the elbow may be present
      Figure 4 – Wasting of 1st dorsal interosseous muscle
  • Sensory Exam:
    • Decreased sensation and two-point discrimination in the distribution of the ulnar nerve described above
    • Close attention to palmar, deep, and superficial branch distribution
  • Wartenberg Sign: 
    • Inability to actively adduct the 5th finger (weakness of 3rd palmar interosseous)
      Figure 5 – Wartenberg Sign

  • Froment Sign: 
    • Patient attempts a “key pinch” or to keep a piece of paper between thumb and 2nd finger.
    • Positive when flexion of the thumb interphalangeal joint (FPL compensates for weakness of adductor pollicis)
      Figure 6 – Froment Sign
  • Jeanne Sign: 
    • Compensatory hyperextension of the 1st MCP and adduction of the thumb with key pinch. This is due to the loss of IP extension and adduction by adductor pollicis
  • Claw Hand Deformity:
    • Intact extrinsic flexors, loss of lumbrical and interosseous muscles
    • Hyperextension of the metacarpophalangeal joints and flexion at the proximal interphalangeal joint of the 4th and 5th digits. 
    • Seen in more severe neuropathy
  • Grip Strength and Key Pinch Strength:
    • These should be performed and compared to the contralateral side for comparison
    • If available a dynamometer will be help to quantify weakness and monitor recovery
  • Provocative Tests:
    • Tinel’s Sign over the cubital tunnel or ulnar tunnel
    • Elbow flexion test:
      • Positive if symptoms develop with elbow in flexion for >60 seconds
    •  pressure over the cubital or ulnar tunnel
  • Vascular Examination:
    • Distal ulnar nerve injuries may be associated with arterial thrombosis or aneurysms
    • Palpate ulnar artery for presence of thrill or pulsatile mass
    • Allen’s test: ensures patency of the arterial arch system in the hand

 

Differential Diagnosis

  • C8/T1 Radiculopathy
  • Thoracic Outlet Syndrome
  • Alcohol related neuropathy
  • Diabetic neuropathy
  • Medial Epicondylopathy
  • Elbow Osteoarthritis 
  • FCU Tendinitis
  • Pisotriquetral arthritis
  • Nonunion of the hook of the hamate
  • Hypothenar hammer syndrome
  • Pancoast Tumor
  • Amyotrophic Lateral Sclerosis

 

Investigations: 

  • EMG/NCS
    • helpful in establishing diagnosis and prognosis
  • Radiographs 
    • rule out hook of hamate fracture
  • Ultrasound 
    • rule out hook of hamate fracture
  • MRI 
    • Evaluate ganglion cyst or ulnar artery aneurysm 
  • Doppler Ultrasound or arteriogram
    • Evaluate for ulnar artery thrombosis or aneurysm 

 

Management:

  • Conservative/Non-operative (mild to moderate cases)
    • Cubital Tunnel Syndrome
      • Activity Modification
        • Avoid direct pressure to medial elbow
        • Avoid repetitive triceps exercises
        • Avoid prolonged elbow flexion
      • NSAIDs
      • Nighttime elbow extension splinting
        • Rolled towels placed in antecubital fossa secured with elastic bandage
        • Rigid thermoplastic custom fit orthoses
        • 45 degree elbow extension with forearm neutral
      • +/- Nerve gliding exercises 
    • Ulnar Tunnel Syndrome
      • European Handguide published in BMJ states conservative management in mild to moderate cases for at least 3 months.
      • According to this Handguide, NSAIDs and corticosteroids are NOT beneficial
      • Activity modification
        • Avoid direct pressure to ulnar tunnel 
        • Avoid repetitive or prolonged wrist extension
      • Bracing/Ergonomic modification
        • Cyclists may consider ergonomically friendly handlebars, or special padded cycling gloves to off-load guyon’s canal.
        • Wrist splinting in neutral position while fingers move freely, at night for 1-12 weeks
      • Consider therapeutic ultrasound and/or nerve gliding exercises
  • Operative
    • Cubital Tunnel Syndrome Surgical Indications
      • Failure of nonsurgical management
      • Advanced and severe symptoms
        • Impaired two-point sensation
        • Muscle atrophy
        • Concerns for motor/sensory losses becoming recalcitrant to treatment
      • Surgical procedures include:
        • Ulnar nerve decompression without transposition
        • Ulnar nerve decompression with anterior transposition
        • Medial epicondylectomy 
    • Ulnar Tunnel Syndrome Surgical Indications
      • Persistent or worsening symptoms over 2 to 4 months
      • Ulnar intrinsic muscle denervation, atrophy or weakness
      • Persistent ulnar sensory deficients 
      • Surgical procedures include:
        • Local decompression
        • Tendon transfer
        • Carpal tunnel release if both present
        • Hook of hamate excision if fracture present

Dr Alessandro Francella (PR ND Feb 20, 2021)

References: 

  1. Earp B., et al. (2014). “Ulnar Nerve Entrapment at the Wrist”. J Am Acad Orthop Surg. 22: 699-706 
  2. Staples J., et al. (2016). “Cubital Tunnel Syndrome: Current Concepts.” J Am Acad Orthop Surg. 25: e215-e224. 
  3. Becker RE, Manna B. Anatomy, Shoulder and Upper Limb, Ulnar Nerve. [Updated 2020 Jul 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499892/
  4. Dunn J., Schulte S. Cubital Tunnel Syndrome. www.orthobullets.com
  5. Hatch D. Ulnar Tunnel Syndrome. www.orthobullets.com
  6. Aleksenko D, Varacallo M. Guyon Canal Syndrome. [Updated 2020 Jul 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK431063/