Management of Failed Ulnar Nerve Transposition
For failed ulnar nerve transposition, proceed directly to advanced imaging with T2-weighted MR neurography to identify the specific anatomical cause of failure, followed by revision surgery with comprehensive decompression of all potential compression sites including the arcade of Struthers, medial intermuscular septum, and deep flexor-pronator aponeurosis.
Initial Diagnostic Approach
When a patient presents with persistent or recurrent symptoms after ulnar nerve transposition, the critical first step is determining whether this represents true surgical failure versus inadequate initial decompression. The history distinguishes between:
- No improvement from surgery (suggests technical error or wrong diagnosis)
- Initial improvement with recurrence (suggests perineural fibrosis or new compression)
Imaging Strategy
T2-weighted MR neurography is the reference standard for evaluating failed ulnar nerve surgery 1. Key findings to identify:
- High signal intensity and nerve enlargement indicating ongoing compression
- Specific anatomical compression points
- Perineural scarring
Ultrasound is a viable alternative with high accuracy for assessing:
- Cross-sectional area and nerve thickness 1
- Hourglass constriction patterns
- Dynamic assessment for nerve dislocation or snapping triceps 1
CT with flexion/extension views can demonstrate recurrent ulnar nerve dislocation from snapping medial triceps 1, which is a commonly missed cause of failure.
Common Causes of Failure
Based on the most recent surgical series, inadequate decompression at key anatomical sites is the primary cause 2:
- Arcade of Struthers (proximal): Found in 71.4% of revision cases
- Medial intermuscular septum: Intact/incompletely released in 76.2% of failures
- Deep flexor-pronator aponeurosis (distal): Compressed in 38% of cases
- Snapping medial triceps: A frequently unrecognized cause that can persist for an average of 22 months before correct diagnosis 3
Surgical Management Algorithm
Revision Surgery Indications
Proceed to revision surgery when imaging confirms:
- Anatomical compression at specific sites
- Perineural fibrosis causing nerve tethering
- Snapping triceps with concurrent nerve symptoms
Surgical Technique
The revision procedure must include comprehensive decompression 2, 4:
- Complete proximal release: Decompress the arcade of Struthers
- Medial intermuscular septum: Ensure complete excision (not just incision)
- Distal release: Decompress the deep flexor-pronator aponeurosis
- Address snapping triceps: If present, perform lateral transposition or excision of the medial triceps head 3
Choice of transposition technique 2, 4, 5:
- Submuscular transposition is preferred for severe cases or when snapping triceps is present
- Revision subcutaneous transposition can be effective if complete decompression is achieved at all sites 4
- Simple neurolysis in situ may suffice if the nerve is already transposed and only perineural scarring is present 6
Expected Outcomes
Recent data shows revision surgery achieves 2, 4:
- 66.6% excellent results by Messina's criteria
- 90.5% patient satisfaction
- Significant improvement in McGowan grade (Grade III to Grade I)
- Improved nerve conduction velocities and amplitudes
Non-Surgical Option
Ultrasound-guided therapeutic injection of the transposed nerve can provide temporary relief 7:
- 93% experience immediate relief
- 80% maintain relief at <3 months
- Only 47% maintain relief >3 months
- 20% eventually require revision surgery
This is best reserved for:
- Patients who decline revision surgery
- Those with mild symptoms
- As a diagnostic tool to confirm the nerve as the pain source
Critical Pitfalls to Avoid
Missing snapping triceps: Always assess for concurrent triceps dislocation, which can coexist with ulnar nerve issues and cause persistent symptoms despite technically successful nerve transposition 3
Incomplete decompression: The most common technical error is releasing only the cubital tunnel while missing proximal (arcade of Struthers) or distal (flexor-pronator aponeurosis) compression sites 2
Inadequate septum excision: Simply incising rather than completely excising the medial intermuscular septum leaves a potential compression point 2
Delayed diagnosis: Average delay of 22 months for snapping triceps diagnosis leads to prolonged patient suffering 3