Abstract
The three-dimensional carpal alignment was measured in the neutral wrist position in 121 asymptomatic volunteers using computer-based cone-beam CT analysis. Normal values and the reliability of the automated analysis are reported. An analysis software based on segmentation of CT images and mathematical modelling was used to determine several axis variants based on different landmarks and to calculate the intercarpal angles automatically. Twenty wrists were imaged twice to determine intra-observer reliability. Mean values using the preferred axis variants were: scapholunate angle 57° (SD 9°), radiolunate angle 2° (SD 10°), lunocapitate angle -14° (SD 9°). Using alternate axis variants notably changed the angles produced. The intra-observer reliability of the analysis was excellent (mean intraclass correlation coefficient 0.97, SD 0.03). Computer-based CT analysis enables highly reproducible and automated assessment of carpal alignment. This study provides a reference database for measurement techniques and normal carpal angle values in three-dimensional imaging.
Highlights
Knowledge of normal carpal alignment and standardized methods of analysis are essential for studies of the carpus
As the imaged wrists were not fixed in a device, the results showed a range of wrist flexion–extension, defined as the angle between the radius and the dorsal margin of the middle metacarpal in the sagittal plane (Koh et al, 2013), and a range of radial or ulnar deviation, defined as the angle between the radius and the middle metacarpal in the coronal plane
Comparing the angle values estimated by the regression equations to the actual measurements showed standard errors of
Summary
Knowledge of normal carpal alignment and standardized methods of analysis are essential for studies of the carpus. Large scanners often require the upper extremity to be placed in a position that is different from that of the standard neutral radiograph on which the normal values are based (Lee et al, 2018; Tan et al, 2014). The values for angles measured on tomographic images correspond to the values in plain radiographs (Lee et al, 2018). The purpose of this study was to measure intercarpal angles in wrist cone-beam CT images using automated 3-D image analysis software based on the segmentation of CT images and mathematical modelling that was developed for this study, and to report its reliability and the normal ranges of carpal angles in asymptomatic volunteers. Several variants of carpal bone axes were explored using landmarks analogous to the landmarks used for the definition of axes on lateral radiographs
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