Evaluation of Dorsal Scaphoid Displacement Using Posterior Radioscaphoid Angle in Patients With Suspected Scapholunate Instability: A Preliminary Study.

Abstract

To assess the validity and reliability of the posterior radioscaphoid angle (PRSA), an indicator of dorsal displacement of the scaphoid, in distinguishing wrists with and without chronic scapholunate instability (SLI). We prospectively evaluated 40 patients (22 men and 18 women; mean age, 46 ± 13 years) with suspected SLI with radiographs and computed tomography arthrography. Based on these data, 3 groups were defined: positive SLI (n = 16), negative SLI (n = 19), and questionable SLI (n = 5). An independent reader measured the PRSA on sagittal computed tomography images using the same procedure. The PRSA median values were significantly lower in the negative SLI group (98°) compared with the positive SLI (110°) and questionable SLI (111°) groups. The difference between the positive SLI and questionable SLI groups was not significant. The best differentiation between patients with and without SLI was obtained with a PRSA threshold value of 103° (specificity of 86% and sensitivity of 79%). In this preliminary study, PRSA analysis offers a quantitative tool for the evaluation of dorsal scaphoid displacement in cases of SLI, including for patients presenting with questionable initial radiography findings. Diagnostic II.