Is Handheld Lower-Resolution Ultrasound Evaluation Sufficient to Measure the Cross-Sectional Area of the Median Nerve?

Abstract

Purpose: This study aimed to assess the accuracy of median nerve cross-sectional area (CSA) measurements using a handheld ultrasound (HHUS) and a cart-based high-resolution ultrasound.

Methods: Fifteen healthy subjects were prospectively enrolled. Each subject underwent standardized ultrasound evaluations of their median nerves with HHUS and a high-resolution ultrasound by three different providers with different levels of training in musculoskeletal ultrasound. CSA calculations were performed using a standardized method. The primary outcome was the mean difference in CSA (ΔCSA) between the gold standard high-resolution ultrasound and the lower resolution handheld ultrasound, with a noninferiority margin set at ΔCSA < 2 mm². Inter-rater reliability was calculated using Lin concordance correlation coefficient (LCCC), and the intraclass coefficient (ICC) was used to calculate intra-rater reliability.

Results: The average CSA of the median nerve across all patients and reviewers using the high-resolution US was > 0.9 mm² for the HHUS. In paired comparisons within subjects, the ΔCSA of the median nerve using the HHUS was 1.8 mm² (95% CI, 0.8-2.7 mm²), and the LCCC was weak 0.258 (0.018-0.470). Noninferiority was not achieved. The intrarater reliability between devices was poor at 0.201. However, the inter-rater reliability among different examiners was good when using the high-resolution device, but it was poor using the HHUS.

Conclusions: The findings suggest caution for the use of handheld ultrasound in measurements of median nerve CSA because the difference between HHUS and gold standard high-resolution ultrasound was not within the noninferiority margin of 2 mm².

Type of study/level of evidence: Diagnostic II.