Weight-Bearing Computed Tomography Analysis of Scapholunate Ligament Injury

Weight-bearing computed tomography allows for assessment of carpal alignment and stability under physiologic load conditions, which may allow for detection of subtle dynamic instabilities that may not be apparent in nonweight-bearing images. The purpose of this study was to evaluate carpal position under physiologic load in healthy and scapholunate interosseous ligament (SLIL)-injured wrists using weight-bearing computed tomography.

Ten healthy controls and 10 participants with arthroscopy (Geisler III or IV) or magnetic resonance imaging-proven SLIL injury underwent computed tomography imaging in three positions: (1) nonweight-bearing neutral, (2) weight-bearing push-up bar (WBPUB) in a semiextended pronated grip position, and (3) weight-bearing in forced wrist extension. Radiographic parameters including scapholunate interval, capitate radius index, radiolunate angle, radioscaphoid angle, scapholunate angle, and dorsal scaphoid translation were performed by a senior resident and reviewed by consensus of three fellowship-trained hand surgeons.

In SLIL injury, the capitate radius index decreased significantly, whereas the scapholunate interval remained unchanged in weight-bearing positions. Scapholunate angle significantly decreased in weight-bearing positions in both groups, and there was no difference in scapholunate angle between SLIL injury and healthy wrists in either weight-bearing position. In WBPUB, SLIL-injured wrists had similar scaphoid flexion but increased lunate extension relative to healthy wrists, whereas in weight-bearing in forced wrist extension, they demonstrated similar lunate extension and decreased scaphoid flexion. In SLIL injury, dorsal scaphoid translation was eliminated in WBPUB.

In SLIL injury, WBPUB demonstrated reduction of the scaphoid into the scaphoid facet, while both weight-bearing positions, WBPUB and forced wrist extension, demonstrated signficant reduction of the scapholunate angle.

Application of load during x-ray or computed tomography imaging could be used to identify reduceable scapholunate ligament pathology prior to surgical reconstruction and may be used in the operating room to assist with obtaining anatomic scapholunate reduction.