What is the treatment for ulnar nerve injury?

Treatment for Ulnar Nerve Injury

For traumatic ulnar nerve injuries requiring surgical repair, early neurorrhaphy provides the best functional outcomes, but for injuries at or above the proximal forearm, distal motor nerve transfers should be strongly considered to preserve hand intrinsic motor function. 1

Risk Stratification and Prognostic Factors

Before determining treatment strategy, assess these critical prognostic factors that predict motor recovery:

• Patient age is the single most important predictor, especially for high-level injuries (at or above proximal forearm) 2
• Injury level significantly impacts prognosis—higher injuries have worse outcomes 2
• Gap size at the lesion site correlates with recovery potential 2
• Delayed time to surgery worsens outcomes 2
• For cases with multiple poor prognostic factors, prolonged observation after initial repair may not be reasonable, and early nerve transfer should be considered instead 2

Conservative Management (For Incomplete Injuries or Post-Surgical Rehabilitation)

Pain Management Algorithm

1. First-line: Paracetamol up to 4g/day for its efficacy and safety profile 3, 4, 5
2. Second-line: Topical NSAIDs for localized pain with fewer systemic side effects 3, 4, 5
3. Third-line: Oral NSAIDs at lowest effective dose for shortest duration if paracetamol inadequate 3, 5

Physical Rehabilitation

• Early sensory reeducation appears to improve sensory function and should be initiated promptly 6
• Range of motion and strengthening exercises maintain function 3, 4, 5
• Local heat application before exercise provides additional benefit 3, 5
• Motor and sensory outcomes generally improve with rehabilitation, though techniques vary widely in the literature 6

Immobilization and Protection

• Splints or orthoses provide symptom relief, particularly with associated wrist pain 3
• Rigid immobilization may be preferred over removable splints for better symptom control 3

Surgical Treatment Strategy by Injury Zone

Zone-Based Surgical Algorithm

The ulnar nerve should be divided into 4 distinct surgical zones, each requiring a unique management strategy 7:

For acute nerve lacerations or complete transections (Sunderland Grade V):

• Zone I and II injuries: Achieved 79.9% and 93.9% recovery respectively to first dorsal interosseous muscle power grade >3 using zone-specific nerve transfer techniques 7
• Zone III and IV injuries: Achieved 84% recovery to the same extent with appropriate surgical intervention 7

Specific Surgical Techniques

For high-level injuries (at or above proximal forearm):

• Distal motor nerve transfers should be performed to preserve hand intrinsic motor function rather than waiting for proximal repair to regenerate 1
• Early nerve transfer may be superior to observation in cases with poor prognosis 2

For nerve repair:

• Early neurorrhaphy of acute nerve injuries provides the best outcome 1
• Advances in imaging (MRI without IV contrast showing T2-weighted high signal intensity and nerve enlargement) allow earlier identification of closed nerve injuries 3, 1

Regarding reverse end-to-side (RETS) nerve transfer:

• A 2022 prospective multicentre study found no crossover regeneration from the donor nerve in RETS procedures 8
• Reinnervation extent was no different from decompression surgery alone 8
• Key pinch strength improved, but compound muscle action potential amplitudes did not 8
• The justifications for RETS technique need careful re-evaluation based on these findings 8

Perioperative Prevention of Ulnar Nerve Injury

For patients undergoing surgery, specific positioning strategies prevent iatrogenic injury:

• Maintain neutral forearm position when arm is tucked at side 4, 5
• Use supinated or neutral forearm position when arm is abducted on armboard 4, 5
• Limit arm abduction to 90° in supine position 4, 5
• Avoid prolonged pressure on the postcondylar groove of the humerus (ulnar groove) 4, 5
• Avoid excessive elbow flexion beyond 90° as this increases ulnar neuropathy risk 4, 5
• Apply specific padding (foam or gel pads) at the elbow, but ensure it is not too tight as inappropriate padding can paradoxically increase risk 4
• Periodic assessment of upper extremity position during procedures is essential 9, 3, 4, 5

Diagnostic Workup

Electrodiagnostic Studies

• Helpful in supporting diagnosis, particularly in atypical presentations 4
• Differentiates demyelinating vs. axonal injury for treatment planning 5
• The classic "sural sparing pattern" helps differentiate ulnar neuropathy from other conditions 4
• Identifies axonal degeneration through reduced sensory nerve action potential amplitude 5

Imaging

• MRI without IV contrast is the reference standard, with T2-weighted neurography showing high signal intensity and nerve enlargement 3, 4, 5
• Ultrasound is an effective alternative with high accuracy (sensitivity 77-79%, specificity 94-98%) for assessing cross-sectional area and nerve thickness 3, 4, 5
• Shear-wave elastography has shown 100% specificity and sensitivity for diagnosing ulnar neuropathy at the elbow 4, 5

Monitoring and Follow-Up

• Regular follow-up to monitor for progression or improvement of symptoms 4
• Follow-up monitoring strategies are determined by location and severity of the lesion 5
• Treatment decisions should consider symptoms, functional limitations, and associated pathology rather than imaging findings alone 3

Critical Pitfalls to Avoid

• Do not wait indefinitely after initial repair in cases with poor prognostic factors (older age, high-level injury, large gap, delayed surgery) 2
• Do not use padding that is too tight during positioning—this creates a tourniquet effect 4
• Do not rely solely on clinical tests for residual neuromuscular blockade assessment during anesthesia—quantitative monitoring is essential 9
• Do not assume RETS nerve transfer provides crossover regeneration—recent evidence shows it does not 8