The Utility of Pre-operative Ulnar Nerve Cross Sectional Area in Predicting Changes in PROMIS Scores Following Cubital Tunnel Release
Gabrielle K Marushack, BSE, Christopher J Dy, MD MPH, FACS and David M Brogan, MD, MSc, Washington University School of Medicine, St. Louis, MO
Introduction
Cubital tunnel syndrome (CuTS) is the second most common entrapment neuropathy, affecting up to 6% of the population1. Numerous studies have demonstrated that cross sectional area (CSA) of the ulnar nerve can be used to diagnose CuTS2,3,4. However, the utility of pre-operative ulnar nerve CSA in predicting patient outcomes following cubital tunnel release is less well understood. The primary goal of this study was to determine the relationship between preoperative ulnar nerve CSA and change in PROMIS scores.
Methods
A retrospective review was conducted of all cubital tunnel surgeries performed by the senior authors from 2015-2023. We included all patients with a preoperative ulnar nerve ultrasound who had completed PROMIS questionnaires pre- and post-operatively. Demographics, pre-operative study results (NCV, EMG and CSA), and PROMIS scores were obtained from these patients’ charts. We conducted linear regression analyses and two-tailed t-tests to determine statistical significance. Power analysis demonstrated that 136 patients provided 80% power to detect a significant correlation with alpha of 0.05.
Results
At 6-12 weeks post-operation, patients with a preoperative CSA ≤ 18 mm2 had an average improvement in PROMIS physical function score of 7.3%, which was significantly greater than the -2.9% average change experienced by patients with a preoperative CSA > 18 mm2 (p < .05). Additionally, of the 14 markers of pre-operative nerve function that we analyzed, 12 markers indicated significantly better nerve function in patients with a CSA ≤ 18 mm2 compared to those with a CSA > 18 mm2. PROMIS anxiety, pain interference, and physical function scores improved significantly at 6-12 weeks post-operation compared to pre-operation, but these changes did not correlate linearly with preoperative CSA.
Conclusion
Patients with pre-operative ulnar nerve CSA > 18 mm2 are likely to have significantly less improvement in PROMIS physical function scores from cubital tunnel surgery. Pre-operative CSA did not correlate linearly with electrophysiologic measures or patient reported outcome measures. To our knowledge, this is the largest study to examine the correlation between preoperative ulnar nerve CSA and change in patient-reported outcomes and the only study on ulnar nerve CSA and patient-reported outcomes to use PROMIS scores.
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