What is the approach to diagnosing and treating ulnar nerve issues?

Diagnostic Approach and Management of Ulnar Nerve Issues

The diagnostic approach to ulnar nerve issues should include a combination of clinical examination, electrodiagnostic studies, and imaging, with MRI without IV contrast being the reference standard for imaging ulnar nerve entrapment. 1

Clinical Assessment

• Motor testing should focus on finger abduction/adduction, thumb adduction, and flexion of 4th and 5th digits to assess ulnar nerve function 2
• Sensory testing should evaluate for altered sensation in the ulnar fourth and fifth digits and the medial side of the arm 3
• Provocative maneuvers including Tinel test and flexion compression testing should be performed to assess nerve irritability 4
• Assessment for ulnar nerve hypermobility should be included, as it occurs in over one-third of adults and can be reliably diagnosed with standardized examination 4
• Focused preoperative physical assessment can identify patients with increased risk for perioperative peripheral neuropathies 5

Diagnostic Testing

• Electrodiagnostic studies are helpful in supporting the diagnosis, particularly in patients with atypical presentation 5
• MRI with T2-weighted neurography is the reference standard for imaging, showing high signal intensity and nerve enlargement 1
• Ultrasound is an effective alternative with high accuracy (sensitivity 77-79%, specificity 94-98%) for assessing cross-sectional area and nerve thickness 1
• Shear-wave elastography has shown 100% specificity and sensitivity for diagnosing ulnar neuropathy at the elbow 1
• The classic "sural sparing pattern" in electrodiagnostic studies can help differentiate ulnar neuropathy from other conditions 5

Common Sites of Entrapment

• Cubital tunnel at the elbow (most common site) 3
• The ulnar groove in the humerus 3
• Guyon's canal at the wrist 3
• Static compression can occur by the cubital tunnel retinaculum and Osborne's ligament between the two heads of the flexor carpi ulnaris 6
• Dynamic compression can occur when the nerve is unstable (subluxation/dislocation outside the ulnar groove) 6

Conservative Management

• Maintain neutral forearm position when arm is tucked at side 1
• Use supinated or neutral forearm position when arm is abducted on an armboard 1
• Limit arm abduction to 90° in supine position to prevent ulnar nerve entrapment 1
• Avoid prolonged pressure on the postcondylar groove of the humerus (ulnar groove) 1
• Patient education and elimination of flexion postures or repeated elbow flexion motions can provide relief in early stages 6
• Paracetamol (up to 4g/day) is recommended as first-line oral analgesic for pain management 1
• Topical NSAIDs are recommended for localized pain with fewer systemic side effects 1
• Range of motion and strengthening exercises are recommended to maintain function 1

Surgical Management

• If conservative management fails or signs of sensory and/or motor deficit are present, surgical treatment should be considered 6
• For stable nerves, in-situ nerve decompression is typically the first-line surgical treatment 6
• For unstable nerves, anterior nerve transposition (generally subcutaneous) or, more rarely, medial epicondylectomy should be performed 6
• Surgery should include exploration of the ulnar nerve throughout its course around the elbow and release of all compressive structures 7

Special Considerations

• Tardy ulnar nerve palsy is a chronic condition characterized by delayed onset ulnar neuropathy after elbow injury, typically occurring as a consequence of nonunion of pediatric lateral condyle fractures 8
• Ulnar nerve hypermobility (present in 37% of elbows) should be assessed and categorized as stable or hypermobile (further subclassified as perchable, perching, or dislocating) 4
• Periodic assessment of upper extremity position during procedures is essential to prevent complications 5
• Avoid excessive elbow flexion beyond 90° as this increases risk of ulnar neuropathy 2

Monitoring and Follow-up

• If surgical treatment fails, review the patient's history and repeat diagnostic tests 6
• Main causes of surgical failure include neuroma of a branch of the medial cutaneous nerve of the forearm, nerve instability, and persistence of a compression point 6
• Regular follow-up is recommended to monitor for progression or improvement of symptoms 9