By convention, radial bend (apex ulnar) was given a positive value, and ulnar bend (apex radial) was given a negative value. The SBA is defined as the angle within the shaft of the metacarpal in the AP and lateral planes. The shaft length was defined as the distance from the center of the most distal part of the distal condyle to the middle of the bony prominences at the metacarpal base and was measured on both coronal and sagittal images. b The CAA was found by drawing a line at the midpoint of the widest part of the cartilage cap and measuring the angle it makes to the metacarpal axis The intersection of these two lines creates the SBA. Then a line was drawn from the midpoint of the distal line to the midpoint of the middle line. A line was drawn from the midpoint of the proximal line to the midpoint of the middle line. a The SBA was measured by drawing lines transversely that divided the metacarpal into four equal sections to establish the proximal, middle, and distal portions. Measurement of shaft bending angle (SBA) and capital-axis angle (CAA). All images were calibrated for size (pixel to distance calibration based on the radiographic marker and digital scale) to ensure accurate measurement. This reconstruction produced virtual AP and lateral images of the individual digits (Fig. From these, AP and lateral RaySum projections were constructed of the individual metacarpals within the field of view. Next, a line was drawn from this center point in the metacarpal head to the midpoint (anteroposterior (AP) and mediolateral) of the metacarpal base found on the axial view (Fig. At the metacarpal head, a transverse (axial) line was drawn perpendicular to the volar and dorsal cortices and at the level of the radial collateral ligament recess, bisecting the head (Fig. These planes were utilized to generate coronal and sagittal projections (RaySum) of each metacarpal individually based on the geometric axis of each bone. Using a digital 3D image reconstruction program (TeraRecon, Foster City, CA), the raw data point files from the CT scans were reconstructed in three planes . Doubling the required sample size allowed for the discrimination of nearly 3° of difference with statistical significance. To achieve this power, 15 scans were required. We aimed to power our study to discriminate 5° of change (paralleling the error range in measurement of conventional radiographs). Thirty-five scans of the small metacarpal and 30 scans of the ring metacarpal were included in this study. Scans which were deemed inadequate based on these properties, or those in which there were any acute or chronic pathologic changes involving the small and ring metacarpals were excluded from study analysis. De-identified raw images from each scan were evaluated for adequate resolution, proper sequences, complete visualization of the metacarpals and no obvious prior injury, severe arthritic changes, or other anomalies affecting the fourth and fifth metacarpals. We used a novel method of image manipulation of computer tomography (CT) images to eliminate difficulties inherent in measuring the anatomy in the lateral plane using radiograph, such as the overlap phenomenon.Īfter the institutional review board approval of the project, 50 consecutive hand CT scans were identified retrospectively using a radiographic database. The purpose of this study is to describe the precise anatomy of normal small and ring metacarpals to serve as reference. Due to bony overlap in the lateral radiographic projection, our understanding of the metacarpal anatomy in this plane is significantly limited. There is a paucity of data detailing the normal radiographic anatomy, with only one report using plain radiographs to measure morphometric parameters. As such, a good understanding of the normal anatomy is important in repairing or reconstructing metacarpal fractures. Although some degree of deformity can be tolerated with little functional consequence, the goal of surgical treatment of metacarpal fractures is restoration of normal anatomy. Accurate measurement of deformity is important in assessing the extent of injury and determining an appropriate course of treatment. Recent studies underscore the difficulty in reliably measuring the magnitude of displacement and angulation. There is no consensus regarding a standard method of radiographic measurement of these fractures. Indications for surgical treatment are based on the degree of fracture angulation and rotational alignment. In addition, these fracture types account for 18 % of all hand injuries. These injuries are common, with an incidence of 13.6 per 100,000 person-years for acute hospital care in the USA. Metacarpal neck fractures of the small and ring fingers typically occur as a result of a direct trauma.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |