Intra-Tester Reliability and Concurrent Validity of Musculoskeletal Ultrasound and Vernier Calipre in Quantifying the Anteroposterior Diameter of the Common Extensor Origin of the Forearm and the Radial Nerve: A Cadaveric Study

Abstract

Introduction: The literature reports an increase in anteroposterior diameter of the common extensor origin (CEO) of the extensor carpi radialis brevis (ECRB) and extensor digitorum communis (EDC) or the radial nerve in painful elbows diagnosed with lateral epicondylalgia (LE) or supinator syndrome. The edge-to-edge measurements of these anatomical structures are quantified using musculoskeletal ultrasound (MSUS). However, in the current literature, reports on the reliability and validity of MSUS measurements of the CEO (of ECRB and EDC) and the radial nerve are not found. In this study, reliability was measured for three testers in determining the anteroposterior diameter of the CEO (of ECRB and EDC) and the radial nerve. Moreover, the concurrent validity was determined of MSUS measurements with Vernier calipre measurements using formalin preserved elbows of human cadavers. Methodology: Cadaver measurements of the CEO (of ECRB and EDC) and the radial nerve were performed. Initially, the sonologist measured the anteroposterior diameter of the CEO (of ECRB and EDC) and the radial nerve. A month after scan, the formalin preserved cadavers were dissected. Consequently, the anteroposterior diameter of the exposed CEO (of ECRB and EDC) and the radial nerve was measured using the Vernier calipre. Results: Eight upper extremities of four embalmed Filipino cadavers (2 males: 2 females) were dissected. A total of seven (7) CEO of EDC, seven (7) CEO of ECRB, and eight (8) radial nerves at the level of the radial head in the elbows of four (4) cadavers were measured using the MSUS and the Vernier calipre. The MSUS and Vernier calipre protocol used in this study was found to be reliable, p \u3e 0.05. However, in all three levels of interest, the MSUS measurements were statistically different from the Vernier calipre measurements, p \u3c 0.05. Conclusion: MSUS and Vernier calipre measurements are reliable methods in measuring the CEO (of ECRB and EDC) and the radial nerve. While each of these methods is reliable in measuring the anteroposterior dimensions of the CEO (of the EDC and ECRB) and the radial nerve, substituting one for the other yielded statistically different measurement results