Cubital Tunnel Syndrome is a compression neuropathy of the ulnar nerve at the level of the elbow. This article reviews the current literature in relation to anatomy, clinical diagnosis, and treatment options of Cubital Tunnel Syndrome.


Authors: Bryce Stash, MD, Monika Martinek, MS3, Natalie Gaio, MD


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In this Article

5 Key Points

1. What is Cubital Tunnel Syndrome?

Cubital Tunnel Syndrome is the compression of the ulnar nerve at the level of the elbow. It is the second commonest compression neuropathy of the arm.

2. Where is the Cubital Tunnel?

The cubital tunnel is an anatomical landmark in the elbow through which the ulnar nerve travels. The cubital tunnel is defined by:

  • Roof: FCU fascia and Osborne’s ligament.
  • Floor: posterior and transverse bands of the MCL and joint capsule.
  • Walls: medial epicondyle and olecranon.

3. What causes Cubital Tunnel Syndrome?

Cubital Tunnel Syndrome can be caused by direct pressure, stretching, and anatomical anomolies. Patients often spend prolonged periods with the elbow flexed due to their occupation, athletics or sleep.

4. What are signs and symptoms of Cubital Tunnel Syndrome?

Cubital Tunnel Syndrome is a clinical diagnosis characterized by numbness and paresthesias in the ulnar nerve distribution (little finger, ulnar ring finger, dorsal ulnar hand). Chronic patients can exhibit intrinsic muscle weakness.

5. What are the treatment options for Cubital Tunnel Syndrome?

Cubital tunnel syndrome can be treated by nonoperative and operative measures.

  • Nonoperative: NSAIDS, splinting, activity modifications.
  • Operative:  Decompression of the ulnar nerve at the level of the cubital tunnel with or without transposition an open or endoscopically.

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Definition of Cubital Tunnel Syndrome

Cubital Tunnel Syndrome an ulnar nerve compression in the cubital tunnel. It is characterized by ulnar nerve sensory and motor deficits, which progresses to intrinsic muscle weakness.

It is the second most common compressive neuropathy after carpal tunnel syndrome (Andrews et al 2018, Bozentka 1998, Robertson et al 2005). The indicence is estimated to be 2-6% of US adults affected. (An TW et al 2017)

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Anatomy of the Cubital Tunnel

The cubital tunnel is a narrow passageway in the median elbow with well-defined anatomical boundaries:

  • Roof: FCU fascia and Osborne’s ligament
  • Floor: MCL (posterior and transverse bands), elbow joint capsule
  • Medial: Medial epicondyle
  • Lateral: Olecranon
Anatomy of the Cubital Tunnel as the Ulnar Never enters and exits the elbow
Anatomy of the Cubital Tunnel

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The ulnar nerve originates from C8-T1 and is a branch of the medial cord of the brachial plexus. A brief summary of its course through the arm is as follows:

  • Proximal Arm: anterior compartment, posteromedial to brachial artery.
  • Distal Arm: enters posterior compartment, adjacent to medial head of triceps.
  • Elbow: posterior to medial epicondyle and travels throught cubital tunnel.
  • Forearm: travels between the FCU heads then between the FCU and FDP.
  • Wrist: Enters via Guyon's canal.
The Ulnar Nerve orientates at the C8-t1 brachial plexus and courses through the arm to terminate at Guyon's Canal
Course of the Ulnar Nerve

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Causes of Cubital Tunnel Syndrome

The aetiology of cubital tunnel syndrome is caused by compression of the ulnar nerve. However, this compresison is often multifaceted.

The most common site of constriction / compression are:

  1. Medial Intermuscular septum: location of ulnar nerve moving from anterior to posterior compartment.
  2. Arcade of Struthers: aponeurotic band from medial IM to medial triceps.
  3. Medial epicondyle: often in previous injury or osteophytes.
  4. Osborne’s ligament: roof of the cubital tunnel.
  5. FCU fascia: forms the arcuate ligament with Osborne Ligament.
  6. Common flexor mass/aponeurosis

Diagnosis of Cubital Tunnel Syndrome

Cubital Tunnel Syndrome is a clinical diagnosis which can be supported by specific investigations. A detailed history and physical examinaiton will also help exluded differential diagnoses.

History

Cubital Tunnel Syndrome is a progressive condition characterised by the following symptoms:

  • Paresthesias and numbness of the ring and ulnar side of ring finger.
  • Weakness in grip strength
  • Aching pain on the medial aspect of the elbow, due to inflammation.
  • Night symptoms‌‌

Physical Exam

The physical examination for cubital tunnel syndrome should include motor, sensory and provocative tests. This can be done through a "Look, Feel, Move, Provoke" structure.

Look:

  • Atrophy: Interosseous and First Web Space
  • Clawing: Ring and Small Finger
  • Subluxation: Ulnar nerve can sublux over the medial epicondyle during flexion of elbow.

Feel:

  • Reduced sensation to ulnar 1.5 digits
  • Can also have reduced senation to dosrum aspect of ulnar wrist (dorsal branch of ulnar nerve)

Move

  • Power: reduced grip  and pinch strength (adductor pollicis)
  • Froment Sign: flexion of thumb IPJ (AIN innervated FPL) to compensate for reduced thumb adduction (ulnar nerve innervated)
  • Jeanne sign: compensatory thumb MCP hyperextension and adduction by radial nerve-innnervated EPL. This compensates for loss of IP extension and thumb adduction by adductor pollicis (ulnar nerve).
  • Wartenberg sign: persistent small finger abduction and extension during attempted adduction secondary to weak 3rd palmar interosseous and small finger lumbrical.  This indicates late stage ulnar nerve deficits (Goldamn et al, 2008)
  • Masse sign: palmar arch flattening and loss of ulnar hand elevation secondary to weak opponens digiti quinti and decreased small finger MCP flexion

Provoke

Positive provocation tests will reproduce the patient’s symptoms such as paresthesias and/or numbness in the ring finger, small finger, or the ulnar part of dorsal hand.

  • Tinel’s test: positive sign over the cubital portion of the elbow. This has reported sensitivity 70%, specificity 98% (Pandey et al, 2014)
  • Elbow flexion test - positive sign when bending the elbow for more than 60 seconds. This has a reported sensitivity 75%, specificity 99% (Pandey et al, 2014)
  • Pressure provocation test - positive sign when direct pressure is applied to the cubital tunnel  (Goldamn et al, 2008)

Investigations‌‌ for Cubital Tunnel Syndrome

Cubital tunnel syndrome is a clinical diagnosis which can be supported by the adjunctive investigaitons.  

Nerve Conduction Studies

Nerve conduction studies can be used for the diagnosis and prognosis of nerve compression (Tang et al, 2015). The diagnostic threshold is a nerve conduction velocity less than 50 m/sec across the elbow (Landeau et al, 2013).

  • Advantages: can help localize lesions of the ulnar nerve, as well as differentiate from other nerve disorders.
  • Disadvantages: There is little diagnostic yield from electrodiagnosis and electrodiagnosis of the ulnar nerve at the elbow is much less straightforward than the median nerve at the wrist.

Imaging

  • Ultrasound: high frequency ultrasound of 14 Hz, ulnar nerve cross-sectional area of 0.065 squared cm (Landeau et al, 2013).
  • MRI: aids in visualization of ulnar nerve (Landeau et al, 2013).
  • X-Ray: helps in diagnosis of ulnar nerve compression caused by presence of bone spurs, fractures, or arthritis (Landeau et al, 2013).


Differential Diagnosis

Ulnar Tunnel Syndrome

  • Ulnar nerve is compressed in the wrist instead of the elbow,
  • No dorsum hand sensory disturbance
  • No extrinsic muscle motor issues (as muscles already innervated)  
  • Positive Tinel's at Guyon's Canal

Bone

  • Deformities, calcifications, osteophytes of bone can occur, especially the medial epicondyle of the humerus,
  • Confirmed by Imaging.

C8 radiculopathy

  • Sensation: Paresthesias in the small finger and ring finger,
  • Motor: deficits in extrinsic and intrinsic motor movements
  • Differentiated by ordering cervical spine radiographs (Andrews et al 2018).


Treatment of Cubital Tunnel Syndrome

Cubital Tunnel Syndrome can be managed through non-surgical and surgical treatment options. Many patients can respond to conservative options and surgical decompression has well reported outcomes.

Non-Surgical‌‌

Patients with mild to moderate cubital tunnel syndrome should undergo a trail of nonsurgical management. A review article of 50 published reports comprising more than 2000 patients noted that 50% of patients with mild cubital tunnel symptoms reported relief with nonsurgical treatment alone (Dellon 2016).

Conservative management may include:

  • Avoiding or modifying activities that involve repetitive flexion of the elbow
  • Triceps strengthening exercises
  • Avoiding direct pressure to medial aspect of elbow
  • Maintaining a resting elbow position of 45-50 degrees of flexion
  • Nighttime elbow splinting to prevent flexion beyond 50 degrees
  • Nerve gliding exercises
  • NSAIDS

Surgical

There are three common operative approaches when it comes to cubital tunnel syndrome. These are simple decompression, anterior transposition (subcutaneous, intramuscular, submuscular), and medial epicondylectomy. All of these procedures have been found to produce satisfactory outcomes (Boone 2015).

‌‌Simple Decompression

This involves a 8-10 cm incision centered behind medial epicondyle in ulnar groove. During incisioon, the the medial antebrachial cutaneous nerve (MABC) is located ~3.5 cm distal to medial epicondyle in subcutaneous plane, running over the fascia. Release all fascial structures superficial to the ulnar nerve along the medial elbow that may be compressing the ulnar nerve, this may include:

  • Medial intramuscular septum (~8 cm proximal to medial epicondyle)
  • Arcade of Struthers
  • Medial epicondyle osteophyte
  • Osbourne’s ligament
  • Arcuate ligament (aponeurosis of FCU, often continuous with Osbourne’s ligament)
  • Deep flexor/pronator aponeurosis

‌‌Anterior Transposition of Ulnar Nerve

  • Places ulnar nerve anterior to medial epicondyle, eliminating tension on nerve with elbow flexion.
  • Subcutaneous transposition involves securing the ulnar nerve anteriorly with subcutaneous tissue.
  • Submuscular transposition involves releasing the flexor pronator mass from the medial epicondyle and elevating it off the underlying medial collateral ligament. The ulnar nerve is then transposed anteriorly, and the reflected pronator mass is secured back to the medial epicondyle.
  • Intramuscular transposition involves securing the anteriorly transposed ulnar nerve with a fascial sling.

Medial Epicondylectomy

  • Maximal nerve decompression noted when an oblique osteotomy is performed in a plane midway between the coronal and sagittal planes.18
  • Proponents of this technique note that limited nerve dissection is required, and thus there is decreased vascular compromise to the nerve.
  • There is a risk of destabilizing the elbow by damaging the MCL, thus you must preserve the insertion of the MCL and repair the periosteum.
  • Persistent medial elbow pain has been reported after this technique, but is rare.

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Outcomes of Cubital Tunnel Syndrome

Cubital tunnel surgery is generally well tolerated and can produce great results, although the success rate cannot duplicate that of a carpal tunnel release.

A recent systematic review concluded that there was insufficient evidence to identify a preferred operative treatment, and suggested that simple decompression and decompression with transposition were equally effective (Caliandro et al, 2019). Additionally, decompression with transposition may result in more deep and superficial wound infections (Caliandro et al, 2019). Procedural choice is often dictated by a surgeon’s preference, though most surgeons tend to transpose the nerve if it appears to be subluxing either on preoperative or intraoperative exam.

Endoscopic assistance has been shown to yield slightly better short term outcomes, with faster healing times, but has relatively similar long term outcomes to open procedures (Dutzmann et al, 2013) Patients undergoing endoscopic release were also more likely to have a hematoma after surgery (Caliandro et al, 2019)

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