A Novel Classification of Intraoperative Ulnar Nerve Instability to Aid Transposition Surgery

Abstract

The purpose of this study was to compare inter-and intraobserver agreement of a novel intraoperative subluxation classification for patients undergoing ulnar nerve surgery at the elbow. We hypothesize there will be strong inter- and intraobserver agreement of the four-category classification system and reviewers will have substantial confidence while reviewing the classification system. Four blinded fellowship-trained orthopedic hand surgeons reviewed 25 videos in total on two separate viewings, 21 days apart. Variables collected were ulnar subluxation classification (A, B, C or D) and a confidence metric. Subsequent to primary data collection, classification grading was stratified into A/B or C/D subgroups for further analysis. Cohen's kappa scores were used to evaluate all variables collected in this study. The interpretation of kappa scores included ≤0.0 as no agreement, 0.01-0.20 as none to slight, 0.21-0.40 as fair, 0.41-0.60 as moderate, 0.61-0.80 as substantial, and 0.81-1.0 as almost perfect agreement. Interobserver agreement of subluxation classification as a four-category scale demonstrated a moderate agreement on first viewing, second viewing, and when both viewings were combined (kappa=0.51, 0.51, and 0.51 respectively). Seventy-five percent (3 out of 4) of reviewers had moderate intraobserver agreement for ulnar nerve subluxation classification while one reviewer had substantial intraobserver classification (kappa= 0.72). Overall, there was high confidence in 65% of classification scores in the second round of viewing, which improved from 58% in the first viewing round. When ulnar subluxation classification selections were regrouped into classes A/B or C/D, 100% of reviewers had substantial interobserver (kappa=0.74 - 0.75) and substantial to almost perfect intraobserver (kappa=0.71 to 0.91) agreement. The four-category classification was reproducible within and between reviewers. Agreement appeared to increase when simplifying the classification to two categories, which may provide guidance to surgical decision making. The validation of a reproducible classification scheme for intraoperative ulnar subluxation may aid with decision making and further postoperative outcomes research.