Study of carpal bone morphology and position in three dimensions by image analysis from computed tomography scans of the wrist

The morphology and positioning of the carpal bones were studied in three dimensions in 18 normal adults on computed tomography (CT) scans of the wrist. The digital data from each CT scan were processed to extract the carpal bones and to automatically characterize their geometry (geometric centroid, principal axes of inertia) using specific software tools. Biometric and angular parameters were defined for this purpose, and most of these parameters showed a normal distribution. The mean distance between the geometric centroid of the capitate and that of the triquetrum, expressed as a relationship to the length of the first principal axis of inertia of the capitate, was found to be the greatest (157.6%±8.4%), whereas the smallest mean distance was between the hamate and triquetrum (91.4%±7.3%). In the sagittal plane, the first principal axis of inertia of the bones of the first carpal row projected in front of the vertical axis of the orthogonal reference system, whereas the first principal axis of the capitate projected behind it. Measurements using this methodology are far more numerous than those from standard plain radiographs and have the additional advantage of being independent of the examiner. Future investigations on normal wrists should provide a normal range for each quantitative parameter, and comparative study of normal and pathologic wrist measurements should help to define the most relevant parameters for specific traumatic pathologies of the wrist.