CORR Insights®: What Is the Normal Ulnar Bow in Adult Patients?

Abstract

Although the restoration of the normal radial bow has long been known to be a key step in the fixation of forearm fractures [7], similar attention has not been paid to restoring anatomic curvature of the ulna. In fact,we use straight plates forwhat has traditionally been thought of as a straight bone. But as Hreha and colleagues [2] show in the current study, sometimes it is important to bend or contour a plate before applying it to a fractured ulna. It is well established that the articulation between the radius and ulna, including the interosseous membrane, substantially affects pronation and supination of the forearm [1, 3, 5, 6]. But might we further improve functional outcomes following treatment of forearm fractures by meticulously restoring the native anatomyof the ulna in the same fashion as we restore the radial bow? Hreha and colleagues [2] cleverly adapted the methods of earlier studies (one that measured the ulna’s sagittal bow [4] and another that measured the radius in the coronal plane [7]) to define normal ranges of anatomic bowing of the ulna in an adult population. They found that the ulna is anything but straight; it is bowed substantially both in the coronal and sagittal planes. Knowing this can help us in practice because we must understand normal anatomy in order to restore it