Triquetral Alignment: Measurement Techniques, Reliability, and Normal Values.

PURPOSE: Assessing triquetral alignment aids in evaluating carpal instability, but no reliable methods have been established. This study assessed factors affecting the reliability of triquetral angle measurements by experienced observers and used a computer-aided analysis software to establish normal values for triquetral alignment.

METHODS

A mathematical modeling-based software analyzed 121 cone-beam computed tomography scans of asymptomatic wrists and measured the radiotriquetral and lunotriquetral angles. Thirty scans were digitally reconstructed into lateral radiographs and measured by hand surgeons without (n = 7) and with (n = 6) illustrated instructions. The second group also measured optimized images with bone overlap removed. Two-axis variants were used: a traditional axial axis and a novel axis perpendicular to the distal articular surface. Intra- and interobserver reliability was assessed using intraclass correlation coefficients. Two patients with volar intercalated segment instability were analyzed using the software.

RESULTS

The computer-aided method demonstrated excellent repeatability and was similar to the manual measurements by surgeons. The mean lunotriquetral angle was 22° (SD 8°; range 4° to 51°) using the axial axis and 10° (SD 8°; range -11° to 33°) using the perpendicular axis. Manual measurements using the axial axis showed poor to moderate reliability, while the perpendicular axis in optimized images demonstrated excellent reliability. In a patient with complete lunotriquetral injury, the software detected a decreased lunotriquetral angle (-7°) compared to a normal angle (15°) contralaterally. In a patient with suspected nondissociative instability, the software confirmed the flexion of the entire proximal carpal row.

CONCLUSIONS

Manual identification of the traditional triquetral axis is unreliable in summation radiographs, even when aided by instructions. The computer-aided analysis was more reliable than that of experienced observers with optimized images.

CLINICAL RELEVANCE: Computer-aided analysis improves the reliability of triquetral alignment assessment and can improve diagnostic accuracy. The established normal values provide a reference for future studies on triquetral pathology.