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. Author manuscript; available in PMC: 2015 May 1.
Published in final edited form as: J Shoulder Elbow Surg. 2013 Dec 2;23(5):708–719. doi: 10.1016/j.jse.2013.08.014

Figure 1. Principal axes and Cardinal planes.

Figure 1

Figure 1

The principal axes are defined as three mutually perpendicular axes about which the moment of inertia of the humerus is maximized (http://oxforddictionaries.com/definition/english/principal-axis) and define the distribution of shape within the humerus. Of the three axes, the first principal axis (Z – superior direction) has the largest moment or inertia and the third principal axis (X – posterior direction) has the smallest moment of inertia. The cardinal planes were defined based on the principal axes, the coronal plane was perpendicular to X, the sagittal plane was perpendicular to Y, and the axial plane was perpendicular to Z.