Factors affecting the sagittal alignment of the lunate

The lunate is described as having a tendency to rotate dorsally as a result of its wedge shape, with the apex towards the dorsum, but maintains an attitude of flexion in most individuals. The present study comprised CT scans of the wrist of 70 healthy volunteers. Sagittal measurements were drawn for the midcarpal and radiocarpal axes, alignment and various shape patterns of the lunate. The midcarpal axis was found to be dorsal, volar and collinear to the radiocarpal axis in 21 (30%), 29 (41%) and 20 (29%) subjects, respectively. The sagittal alignment of the lunate demonstrated significant correlation with measurements of the midcarpal and radiocarpal axes with no correlation with its various shape patterns. It is concluded that the relationship between the midcarpal axis and the radiocarpal axis in terms of dorso-volar displacement has a key role in determining the sagittal alignment of the lunate, while the shape of the lunate may be only a secondary consideration