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Perfusion to the Ulnar Nerve as Affected by Three Surgical Conditions: In Situ Decompression, Subcutaneous Transposition, and Submuscular Transposition: Preliminary Results
Scott G. Edwards, MD
Department of Orthopaedic Surgery, The CORE Institute, Phoenix, AZ
Introduction: Currently, there is conflicting data that fails to support one surgical treatment for ulnar neuropathy at the elbow over other. One possible reason may be a lack of understanding of how these procedures change the perfusion to the ulnar nerve. Although many theories have been proposed, no studies have demonstrated how these procedures actually affect the perfusion to the ulnar nerve. The purpose of this study is to compare the perfusion of the ulnar nerve in vivo during different surgical conditions.
Materials and Methods: All patients who met criteria of being diagnosed with recalcitrant ulnar neuropathy failing nonoperative management were enrolled prospectively in this study during September 2015 to April 2016. Exclusion criterion was previous ulnar nerve surgery involving transposition. Using intraoperative fluorescence scanning angiography, the perfusion of the ulnar nerve in each patient was measured at four conditions: native nerve exposure, in situ decompression, subcutaneous transposition, and submuscular decompression. Perfusion measurements were taken in five locations on each nerve: 8 cm proximal to the medial epicondyle (Area 1); 4 cm proximal to medial epicondyle (Area 2); at medial epicondyle (Area 3); 4cm distal of medial epicondyle (Area 4); and 8cm distal to medial epicondyle (Area 5).
Results: 14 patients were enrolled which included 10 males and 4 females. 5 had diabetes and 4 were smokers. 3 patients had previous ulnar nerve decompression. 4 patients underwent concomitant surgery which included carpal tunnel release, radial head excision, and lateral epicondylar debridement. Overall, nerve perfusion increased 30% with in situ decompression. Perfusion, however, decreased 16% after subcutaneous transposition as compared to decompression with Areas 4 and 5 demonstrating the most substantial drops (12% and 15% respectively). With submuscular transposition, perfusion returned to decompression values, with Areas 2 and 4 demonstrating the most substantial improvements (10% and 8%, respectively).
Conclusions: All three surgical treatments evaluated improved ulnar nerve perfusion, but subcutaneous transposition did not allow as much perfusion as either in situ decompression or submuscular transposition. Given the segments of the nerve affected after subcutaneous transposition, it is possible that the nerve’s contact against the adjacent muscle distal to the medial epicondyle may have caused excessive intraneural tension. In situ decompression appears to be a preferred choice for the purpose of maximizing the perfusion to the nerve. When transposition is indicated, however, submuscular may be preferred to subcutaneous, particularly in patients who may have predisposed compromised vascularity such as smokers or diabetics.
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