The computed tomography (CT) scans will be performed on either a General Electric CTI scanner or a Siemens Volume Zoom scanner. The scans will be performed at either the University of Colorado hospital or the Anschutz Center for Advanced Medicine at the Fitzsimmons site. The subject will be positioned face-up on the CT table, with arms supported at his side in a special cradle designed for this study, which will prevent movement during the scanning. Two contiguous slices of 5 or 10 mm thickness will be taken through the center of the glenohumeral joints. With proper positioning, both right and left joints will be centered on the same images. The CT table will be moved and two slices of 5 to 10 mm thickness will be taken through the distal humerus on both sides at the level of the epicondyles.
Computed Tomography Safety Information
Computed Tomography Scanning uses x-ray technology to image the musculoskeletal system. This technologyis typically used as a diagnostic tool to visualize and compare the relative alignment and positioning of bony joint compinenets. Researchers have carried out extensive tests of radiation dosage to determine whether CT scans are safe for patients. In accordance with the relatively low risk associated with the radiation dosage of CT scans, doctors and researchers continue to utilize CT scans as a commonplace diagnostic tool. The current research study proposes to limit radiation exposure further through several amendments to typical protocol.
The advent of studies using computed tomography have begun to illuminate the important role of the bony alignment of the shoulder as a possible primary factor responsible for the secondary pathologies seen in the ligamentous constraints of the shoulder. Considering the role of the humeral torsion in anterior shoulder instability, the etiology of pathologic humeral torsion comes into question. During the development of the adolescent skeleton, bone growth occurs faster than bone resorption. This bone growth occurs in accordance with Wolff's Law, which states that bone will remodel preferentially with increased bone deposition in areas of imposed stress. The external forces placed on the bones of children play a pivotal role in the development of the skeletal system, due to the rapid remodeling of bone during childhood. Increased rotational forces imposed on the immature skeleton magnify the amount of torsion dispersed through the longitudinal axes of bones. Due to the repetitive nature and extreme rotational forces associated with pitching, torsional malformations may be magnified in elite youth pitchers. Sample Shoulder CT Scan Images
Each child will receive two scans per visit or six scans total over the course of the five-year study. It is important to note that the radiation received is a safe level and that the radiation is not additive. Whenever a scan is given and a small dose of radiation is received, that radiation decreases and disappears slowly over the following two months. Therefore, when the next scan is performed there will be no radiation from the previous scan present causing an additive effect. The exposure factors for each slice whether 5 or 10 mm will be: 120KV or 25mAs.
Measurement of humeral torsion typically involves a quantitative comparison of the angle the humeral head with the axis of reference with the angle of the distal humerus in relation to the same axis of reference. From the CT images obtained, magnified views of the four joints will be obtained from the two slices. One each side, a coned down view of the glenohumeral joint, including the entire body of the scapula and entire humeral head will be printed on film. A similar magnified view of the elbow will be obtained for each side. Superimposition of the shoulder and elbow images will allow for measurement of humeral torsion. The changes in humeral torsion for elite pitchers compared to non-throwing athletes of the same age, will paint a clear picture as to the bony changes associated with repetitive pitching.
