Comparative Computer-Aided Analysis of Three-Dimensional Carpal Alignment in Scapholunate Advanced Collapse and Healthy Wrists.

PURPOSE: Scapholunate dissociation frequently results in malalignment and scapholunate advanced collapse (SLAC). Previous analyses have relied on visual observations of carpal angles among the scaphoid, lunate, and capitate on lateral radiographs. However, the 3-dimensional carpal alignment during SLAC progression remains unclear. The purpose of this study was to analyze 3-dimensional carpal malalignment in SLAC wrists.

METHODS

Using computer-aided cone-beam computed tomography analysis software based on segmentation and numerical modeling, we defined three-dimensional carpal axes and examined alignment and carpal height ratio in 18 SLAC wrists along the radial coordinate (positive in palmar and ulnar directions). These results were compared with previously reported normal alignment values obtained from 121 healthy wrists.

RESULTS

In the sagittal plane, mean scapholunate, lunotriquetral, lunocapitate, and capitometacarpal angles were -100° (SD, 11°); 20° (SD, 11°); 7° (SD, 12°); and 18° (SD, 8°); respectively, whereas the angles were -58° (SD, 9°); 12° (SD, 8°); -17°(SD, 11°); and 8° (SD, 6°); respectively, in healthy wrists. The sagittal scapholunate angle exhibited the highest area under the receiver operating characteristic curve (0.999), with a threshold value of ≤-76°, indicating pathology. In the coronal plane, the carpal alignment of SLAC wrists remained unchanged, excluding a minimal ulnar tilt of the capitate.

CONCLUSIONS

Carpal malalignment in SLAC wrists not only affects the radio- and midcarpal joints, but also extends to the third carpometacarpal joint, with malalignment evident in both the sagittal and coronal planes. In SLAC wrists, the sagittal lunotriquetral angle increases in the positive direction, due to the lunate angulating more than the triquetrum.

CLINICAL RELEVANCE: These findings have potential to contribute to the development of computer-aided diagnostic tools for 3-dimensional imaging technology. In the future, such tools could highlight abnormal values and minimize diagnostic errors in clinical practice.