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Failed Submuscular Ulnar Nerve Transposition: What Next?
Todd Rimington, MD1; Dean G. Sotereanos, MD2
1Orthopaedic Surgery, Allegheny General Hospital, Pittsburgh, PA; 2Allegheny General Hospital, Pittsburgh, PA

Reasons for failure of ulnar nerve transposition include incomplete release and cicatrix formation.  Common areas of incomplete release include proximally at the medial intermuscular septum and distally at the flexor carpi ulnaris aponeurosis.  In contrast, our experience has implicated the medial epicondyle as common source of recurrent compression.  Cicatrix tethers the ulnar nerve to medial epicondyle and the posterior aspect of the ulnar nerve is compressed against the anterior aspect of the medial epicondyle resulting in a Z-shaped deformity of the ulnar nerve.  The purpose of this study was to evaluate the clinical outcomes of revision ulnar nerve transposition with medial epicondylectomy after failed submuscular ulnar nerve transposition.  We hypothesize that revision submuscular ulnar nerve transposition with medial epicondylectomy will improve elbow pain, and ulnar nerve function.

Methods: We retrospectively reviewed the charts of 14 patients who had failed submuscular ulnar nerve transposition.  Their average age was 36.9 years with an average of 1.9 previous surgeries.  The average follow-up was 17.6 months.   The primary reason for revision was elbow pain in 9 patients and poor hand function in 5 patients. Our surgical approach included revision ulnar nerve decompression with microscopic external neurolysis, minimal medial epicondylectomy, and flexor-pronator origin lengthening.   Primary outcomes assessed included pain by VAS scale, two-point discrimination, interosseous strength and McGowen grade.  Student t-test and Chi-square analysis were used to compare results with significance p<0.05. 

Results: Pain improved from 8.9 (range 6-10) to 2.8 (range 0-6) on a VAS pain scale (p<0.01).  All patientsí pain improved with the surgery.  Two-point discrimination in the small finger improved from 12.4 mm to 8.1 mm (p=0.02).  There was not a significant improvement in McGowan grade 2.1 to 1.9 (X2=1.58, p=0.45) or interosseous strength 3.9 to 4.4 (X2=5.07, p=0.08).  No patients developed a worse McGowan grade or lost interosseous strength.  There was no difference between the total elbow range of motion 136 dregrees to 137 degrees, p=0.44.

Summary Points

  1. The medial epicondyle is an important source of recurrent compression after failed submuscular ulnar nerve transposition.
  2. The transposed ulnar nerve can form a Z-shaped deformity over the anterior aspect of the medial epicondyle that is accentuated with elbow extension.
  3. Revision of a submuscular ulnar nerve transposition should include medial epicondylectomy when a Z-shaped deformity is present.
  4. Revision submuscular ulnar nerve transposition with medial epicondylectomy significantly improves elbow pain and ulnar sensory function with no detriment to ulnar nerve motor function. 

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