Reproducibility of Ultrasonographic Measurements of the Ulnar Nerve at the Cubital Tunnel

The cross-sectional area (CSA) of the ulnar nerve is thought to be indicative of ulnar nerve entrapment. The purpose of the study was to determine reproducibility of ultrasonographic measurements of CSA of the ulnar nerve at the cubital tunnel in healthy adults. Two sonographers tested 69 participants using a standardized protocol. The inter-rater reliability intra-class correlation coefficient was 0.63, and the intra-rater reliability intra-class correlation coefficient was 0.85 for sonographer 1 and 0.88 for sonographer 2. The smallest detectable changes were 2.47 and 2.63 mm2 (25% and 26% of the mean CSA). The mean difference and 95% limits of agreement for sonographers 1 and 2 were -0.13 (-2.56 to 2.29) and -0.38 (-2.93 to 2.18). Based on the fair to good inter-rater reliability, the excellent intra-rater reliability and the clinical applicable intra-rater agreement, ultrasonography seems to be a valuable tool with which to assess the CSA of the ulnar nerve for diagnostic and evaluative purposes.