Wrist and hand ultrasound: Reliability of side-to-side comparisons of very small (<2-mm) clinically relevant anatomic structures

Objectives—In ultrasound (US) examinations of clinically relevant very small structures of the wrist and hand, the healthy contralateral side can be used as a reference to identify subtle abnormalities. Intraindividual side-to-side variability must be minimal. The aim of this study was to assess the reliability of side-to-side US evaluations of very small structures of the wrist and hand. Methods—Forty-one healthy volunteers were prospectively studied. Small structures of the wrist and hand were evaluated bilaterally by 2 musculoskeletal radiologists in separate sessions. The first annular pulleys of the second finger and the thumb, sagittal band of the third finger, extensor and flexor retinacula, ulnar collateral ligament of the thumb, radial collateral ligament of the second finger, and palmar cutaneous branches of the median and ulnar nerves were considered. To assess intra-and inter-reader agreement, 10 of 41 (24%) examinations were repeated. Nonparametric statistics were used. Results—Data were not normally distributed (P>.001). Intra-reader agreement was κ = 0.674 (95% confidence interval [CI], 0.57–0.78), and inter-reader agreement was κ = 0.935 (95% CI, 0.92–0.95). The mean value ± SD for all of the structures was 0.78 ± 0.44 mm. The overall coefficient of variation was 9.8% ± 0.07%. The intraclass correlation coefficient was 0.97 (95% CI, 0.96–0.98). Conclusions—In clinical practice, the healthy contralateral side can be used as a reference during a real-time musculoskeletal US evaluation of small (<2-mm) structures.