Wrist Pathology: Trauma

CT plays an essential role in both detection and delineation of wrist fractures. The wrist is one of the musculoskeletal regions which will benefit the most from multidetector row CT (MDCT) imaging. Many articles in the literature have described protocols tailored for specific types of wrist fractures and alternative methods of positioning the arm to evaluate a particular region of the anatomy. Because of the small size of the bones and the limited resolution of reconstructions from helical CT datasets, one or more specific planes have been advised for the CT acquisition depending on the site of fracture. Furthermore, the recommendation has been made to acquire one dataset in the plane perpendicular to the line of the fracture to maximize the resolution when assessing the fracture. With spiral CT, despite the use of 2 mm collimation, the plane of acquisition yielded the highest resolution images and reconstructions have been suboptimal. Accordingly, the anatomic region of the fracture dictated the acquisition plane and multiple acquisitions were recommended if viewing in more than one orientation was required. These alternative types of positioning can be difficult for the patient with an acute fracture.

Using MDCT, the superior resolution resulting from isotropic datasets should preclude the requirement for wrist acquisitions in any plane other than axial in order to obtain adequate resolution in any viewing orientation. The high quality volumetric datasets made possible with MDCT result in datasets with equal resolution in all planes, which yield exceptional multiplanar and 3D renderings. As a result, the volumetric dataset can be reconstructed or rendered in the optimal viewing orientation for any fracture location or orientation. Furthermore, unlike a CT tailored for one type of fracture, unsuspected associated fractures can still be displayed in the appropriate plane with no loss of resolution. Multiple acquisitions may still be warranted if radioulnar subluxation is suspected. Subluxation may only be revealed by comparing CT in the neutral position to the appearance of the wrist prone and supine.

The axial plane is best for fractures of the distal radius and hamate hook, and to evaluate the DRUJ, intercarpal joints, subluxations and displaced bone fragments. The coronal plane facilitates evaluation of the radiocarpal joint, intercarpal joints and carpal-metacarpal joints, and is the best orientation for post operative imaging following surgical fusion. Sagittal imaging has been recommended for identification of intraarticular radial fracture gaps and step-offs and to visualize the axis running along the 3rd metacarpal-capitate-lunate-radius. This plane is also useful for detecting dorsal and palmar subluxation. For suspected scaphoid fractures, CT should be acquired in the oblique/sagittal plane. This is optimal for identifying palmar or dorsal displacement or angulation, humpback deformities and fracture diastasis.