Repeated Measurements of Ultrasound Median Nerve Cross-Sectional Area Are Associated with Symptomatic and Functional Improvement after Carpal Tunnel Release.

Abstract

Background: The potential for ultrasound (US) to be used as an objective measurement of improvement after carpal tunnel release is poorly understood. The purpose of this study is to evaluate whether measurements of US cross-sectional area (CSA) of the median nerve in the postoperative recovery period are associated with improvement of Boston Carpal Tunnel Questionnaire (BCTQ) scores for the Symptom Severity Scale (SSS) and Functional Severity Scale (FSS). Methods: A total of 167 wrists from 137 patients who underwent CTR with availability of US and BCTQ at 2-weeks, 6-weeks, 6-months and 1-year postoperatively were analysed. The primary outcome measurement was the ability to achieve the minimal clinically important difference (MCID) for relative changes in BCTQ. Regression analysis was performed using generalised estimating equations. Either Pearson correlation or Spearman correlation was used at each timepoint to determine the relationship between median nerve CSA and BCTQ scores. Results: Median nerve CSA was found to be significantly associated with achieving MCID cutoff values for SSS (p = 0.002) and FSS (p = 0.041). In men, a postoperative CSA of <10 mm² was associated with improvements in both FSS and SSS. In women, a postoperative CSA of <10 mm² was associated with improvements in SSS and a postoperative CSA of <8 mm² was associated with improvements in FSS. The Spearman correlation coefficient was significant between median nerve CSA and SSS scores at the 2-week and 6-week follow-up timepoints. Conclusions: Measurements of US median nerve CSA in the postoperative setting can provide an objective measure and are independently associated with BCTQ score improvement that achieves MCID. US measurements at the 2-week postoperative timepoint are most correlated with symptomatic patient-reported outcome measures. Thus, in carpal tunnel release patients with poor early outcomes, US may help rule out persistent CTS and guide further treatment or diagnosis. Level of Evidence: Level III (Therapeutic).