Triangular fibrocartilage of wrist: presentation on high resolution ultrasonography.

This study consisted of two parts. Part I is for detection of the normal triangular fibrocartilage by high resolution ultrasonography and Part II is a preliminary study to evaluate high resolution ultrasonography in the diagnosis of tears of the triangular fibrocartilage. Normally, the triangular fibrocartilage was seen in all cases in Part I as an inverse triangular structure of homogeneous hyperechogenicity on transverse and oblique sagittal scans at the level of the distal radioulnar joint. At its waist it measured from 2.3 to 4.2 mm (mean, 3.0 +/- 0.5 mm) on oblique sagittal scan and from 2.5 to 3.7 mm (mean, 3.2 +/- 0.4 mm) on transverse scan. Under normal conditions, the triangular fibrocartilage is thicker than 2.5 mm on both transverse and oblique sagittal sections with a confidence level of 95%. In Part II, eight of the 47 wrists were found to be hypoechoic in the triangular fibrocartilage region, which proved to be tears by arthrography. Six cases showed a homogeneous hyperchoic triangular fibrocartilage measuring from 1.8 to 2.8 mm (mean, 2.3 +/- 0.5 mm) in transverse section and from 0 to 2.2 mm (mean 1.2 +/- 1.1 mm) in oblique sagittal section; five of these proved to be tears by arthrography. In contrast, 33 wrists had a homogeneous hyperechoic triangular fibrocartilage measuring from 2.5 to 4 mm (mean, 3.1 +/- 0.4 mm) and 2.5 to 4.2 mm (mean, 3.1 +/- 0.6 mm) on transverse and oblique sagittal sections, respectively; 27 proved to be normal triangular fibrocartilage by arthrography. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 68.4%, 96.4%, 92.9%, 81.8%, and 85.1%, respectively. HRUS can display the normal triangular fibrocartilage as a homogeneous hyperechoic and inverted triangular structure. The torn triangular fibrocartilage appears as a hypoechoic region or as thinning (< 2.5 mm) of the hyperechoic structure on either transverse or oblique sagittal section. HRUS has an acceptable accuracy in the diagnosis of triangular fibrocartilage tear.