Intraobserver and interobserver reliability of radial torsion angle measurements by a new and alternative method with computed tomography

OBJECTIVE: To evaluate the intraobserver and interobserver reliability of radial torsion angle measurement using computed tomography. METHODS: Twelve pairs of cadaver radii and 116 forearms from 58 healthy volunteers were evaluated using axial computed tomography sections measured at the level of the bicipital tuberosity and the subchondral region of the radius. During digital imaging, the angle was formed by two lines, one diametrically perpendicular to the radial tubercle and the other tangential to the volar rim of the distal joint surface. Measurements were performed twice each by three observers. RESULTS: In cadaveric bones, the mean radial torsion angle was 1.48° (‐6° ‐ 9°) on the right and 1.62° (‐6° ‐ 8°) on the left, with a mean difference between the right and left sides of 1.61° (0° ‐ 8°). In volunteers, the mean radial torsion angle was 3.00° (‐17° ‐ 17°) on the right and 2.91° (‐16°‐ 15°) on the left, with a mean difference between the sides of 1.58° (0° ‐ 7°). There was no significant difference between each side. The interobserver correlation coefficient for the cadaver radii measurements was 0.88 (0.72 ‐ 0.96) and 0.81 (0.58 ‐ 0.93) for the right and left radius, respectively, while for the volunteers, the difference was 0.84 (0.77 – 0.90) and 0.83 (0.75 – 0.89), respectively. Intraobserver reliability was high. CONCLUSION: The described method is reproducible and applicable even when the radial tubercle has a rounded contour.