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Location of Fracture Determines Deformity in Wrist

When the scaphoid bone on the thumb side of the wrist is broken it may not heal. This is called a nonunion fracture. In time degenerative changes occur and arthritis sets in. This doesn't happen with all nonunion scaphoid fractures. In this study, researchers show why this happens.

Using a special 3-dimensional (3-D) imaging technology, 20 patients with nonunion scaphoid injuries were examined. Using CT scan and computer software a 3-D model was made for each patient. Both bones of the forearm (radius and ulna) and the scaphoid were included. The authors used a mirror image of the uninjured wrist to match the bone placement.

The location of the fracture on the scaphoid was mapped. Any shifting or displacement of the bone fragments was also shown. The injured wrist was compared to the normal wrist by superimposing the injured view over the normal CT image.

Based on the location of the fracture, two types of scaphoid nonunion were described. The first was distal (farther away from the forearm) and the second was proximal (closer to the forearm). The broken piece moved away from the main bone, sometimes shifting and rotating. This causes a wrist deformity as the bones around the scaphoid shift, too.

Using 3-D imaging the authors were able to show that the location of scaphoid nonunion fractures determines the final outcome. Patients with distal fractures end up with more deformity and a worse result. The location of the break causes instability of the entire first row of wrist bones. Surgery is needed to correct the deformity and restore the wrist.

References: Kunihiro Oka, MD, et al. Patterns of Carpal Deformity in Scaphoid Nonunion: A 3-Dimensional and Quantitative Analysis. In The Journal of Hand Surgery. November 2005. Vol. 30A. No. 6. Pp. 1136-1144.

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