title: Regional Ulnar Nerve Strain Following Decompression and Anterior Subcutaneous Transposition in Patients With Cubital Tunnel Syndrome.
abstract: OBJECTIVE
  Simple decompression and anterior subcutaneous transposition are effective surgical interventions for cubital tunnel syndrome and yield similarly favorable outcomes. However, a substantial proportion of patients demonstrate unsatisfactory outcomes for reasons that remain unclear. We compared effects of decompression and transposition on regional ulnar nerve strain to better understand the biomechanical impacts of each strategy.
  
  
  METHODS
  Patients diagnosed with cubital tunnel syndrome and scheduled for anterior subcutaneous transposition surgery were enrolled. Simple decompression, circumferential decompression, and anterior transposition of the ulnar nerve were performed during the course of the transposition procedure. Regional ulnar nerve strain around the elbow was measured for each surgical intervention based on 4 wrist and elbow joint configurations.
  
  
  RESULTS
  With elbow extension at 180°, both circumferential decompression and anterior transposition resulted in approximately 68% higher nerve strains than simple decompression. Conversely, with elbow flexion, simple decompression resulted in higher average strains than anterior transposition. Limited regional differences in strain were observed for any surgical intervention with elbow extension. However, with elbow flexion, strains were higher in distal and central regions compared with the proximal region within all surgical groups, and proximal region strain was higher after simple decompression compared with anterior transposition.
  
  
  CONCLUSIONS
  As predicted by the altered anatomic course, anterior transposition results in lower ulnar nerve strains than simple decompression during elbow flexion and higher nerve strains during elbow extension. Irrespective of anatomic course, circumferential release of paraneurial tissues may also influence nerve strain. Nerve strain varies regionally and is influenced by surgery and joint configuration.
  
  
  CONCLUSIONS
  Our data provide insight into how surgery resolves and redistributes traction on the ulnar nerve. These findings may help inform which surgical procedure to perform for a specific patient, guide rehabilitation protocols, and suggest regions of anatomic concern during index and revision surgery.
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA; VA San Diego Healthcare System, San Diego, CA.
authors.forename: Ian
authors.initials: I
authors.lastname: Foran
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA; VA San Diego Healthcare System, San Diego, CA.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Vaz
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA; VA San Diego Healthcare System, San Diego, CA.
authors.forename: Jakub
authors.initials: J
authors.lastname: Sikora-Klak
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA; Department of Radiology, University of California, San Diego, La Jolla, CA; Department of Bioengineering, University of California, San Diego, La Jolla, CA.
authors.forename: Samuel R
authors.initials: SR
authors.lastname: Ward
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA; VA San Diego Healthcare System, San Diego, CA.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Hentzen
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA; Department of Bioengineering, University of California, San Diego, La Jolla, CA; VA San Diego Healthcare System, San Diego, CA. Electronic address: sbshah@ucsd.edu.
authors.forename: Sameer B
authors.initials: SB
authors.lastname: Shah
mesh_terms: D000368:Aged; D020430:Cubital Tunnel Syndrome / Q000175:diagnosis / Q000601:surgery*; D019299:Decompression, Surgical / Q000009:adverse effects* / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016067:Nerve Transfer / Q000379:methods*; D019635:Neurosurgical Procedures / Q000379:methods; D010147:Pain Measurement; D016059:Range of Motion, Articular / Q000502:physiology*; D012086:Reoperation / Q000379:methods; D012189:Retrospective Studies; D018570:Risk Assessment; D012494:Sampling Studies; D013180:Sprains and Strains / Q000209:etiology / Q000503:physiopathology*; D016896:Treatment Outcome; D014459:Ulnar Nerve / Q000503:physiopathology / Q000601:surgery*
keywords: Cubital tunnel syndrome; anterior transposition; biomechanics; decompression; peripheral nerve