Computer-aided three-dimensional analysis of carpal alignment in scaphoid nonunion advanced collapse wrists: A comparative study with scapholunate advanced collapse and healthy wrists.

OBJECTIVE

To analyze three-dimensional carpal malalignment and height in scaphoid non-union advanced collapse (SNAC) wrists.

MATERIALS AND METHODS

Twelve cone-beam CT scans of SNAC wrists were analyzed using computer-aided software to define 3D carpal axes and measure intercarpal angles and carpal height ratio. Comparative data included 121 healthy wrists and 18 wrists with scapholunate advanced collapse (SLAC).

RESULTS

SNAC wrists showed dorsal angulation of the lunate and even greater dorsal angulation of the triquetrum, resulting in an increased sagittal scapholunate angle and a decreased sagittal lunotriquetral angle compared to healthy wrists. Compared to SLAC wrists, SNAC wrists had similar sagittal radiolunate and scapholunate angles but a significantly lower lunotriquetral angle. Nonunions in the middle and distal third were associated with greater dorsal angulation of the lunate than proximal third nonunions. In the coronal plane, SNAC wrists showed ulnar tilting of the capitate and hamate compared to healthy wrists. Carpal height ratio was significantly decreased compared with healthy wrists but comparable to SLAC wrists.

CONCLUSION

Scaphoid nonunion location influenced alignment, with proximal nonunions associated with reduced dorsal angulation of the lunate. SNAC wrists differ from SLAC wrists in exhibiting a decreased sagittal lunotriquetral angle, indicating a distinct pathomechanism of carpal instability.