Evaluation of Cam Deformity on 3-Dimensional Computed Tomography With the Best-Fit Sphere Technique and the Alpha Angle Marking Method

Background: Three-dimensional computed tomography (3D-CT) is commonly used for the evaluation of cam deformity; however, it does not display the cam border directly. Purpose: To compare the efficacy of the best-fit sphere (BFS) method and the alpha angle marking (AAM) method in 3D-CT evaluation for the cam border. Study Design: Cohort study (Diagnosis); Level of evidence, 3. Methods: Twenty-six cases of cam deformity, confirmed during hip arthroscopy, were included in this study. All patients underwent a CT scan before surgery. Using multiplanar reconstruction, we obtained reformatted CT images of oblique axial, oblique coronal, and radial views. The alpha angle and femoral head-neck offset ratio (hnoR) were measured on the reformatted CT images. The cam area on 3D-CT was displayed in 4 different ways: by importing the markers from the reformatted CT images of the oblique axial view (cam-oa), the oblique coronal view (cam-oc), or the radial view (cam-r) using the AAM method, or by using the BFS method (cam-bfs). The sizes and locations of the displayed cams were compared. Results: All hips in this study had an alpha angle greater than 60° and an hnoR smaller than 0.17. The radial view measured a larger alpha angle and smaller hnoR than the oblique axial and coronal views ( P < .05). The areas of cam-oa, cam-oc, cam-r, and cam-bfs were 161.47 ± 27.96, 89.78 ± 19.23, 241.73 ± 34.55, and 329.75 ± 42.73 mm2, respectively, and their medial-to-lateral ranges along the acetabulum (clockface referents) were 12:30 to 03:00, 11:30 to 01:30, 11:30 to 03:00, and 11:00 to 03:30, respectively. Among the 4 displays, cam-bfs had the largest area and medial-to-lateral range ( P < .05), and cam-r had the second largest area and range ( P < .05). No significant difference in the mean distances from the acetabular rim to the superior border was detected among the 4 displays ( P > .05). Conclusion: The cam area displayed by the BFS method on 3D-CT was larger than those evaluated by the AAM method. In the reformatted CT, the sizes and locations of cam deformity differed among the oblique axial, oblique coronal, and radial views, with the radial view showing the greatest area.

Postoperative 320 multi-slice computed tomography in assessment of pedicle screw insertion in thoraco-lumbar fixation

Background Pedicle screw instrumentation is used widely in lumbar spine for stabilization to enhance arthrodesis and has been accepted in the thoracic spine in recent years. The purpose of this study was to assess the value of postoperative 320 multi-slice computed tomography (MSCT) in assessment of pedicle screw placement in patients with spinal fixation with clinical and surgical correlation. Results A total of 340 pedicular screws were inserted to 70 cases. 286 (84.12%) were in, 54 screws (15.88%) were violated, and revision surgeries were required for 5 displaced screws. On axial, coronal reconstruction and three-dimensional (3D) reformatted CT images 36, 47, and 54 displaced screws were detected, respectively. Both sensitivity and specificity for 3D reformatted images were 100%. For axial image, they were 97.6% and 89.4%, respectively, compared with surgical findings in 5 revised screws. Conclusion Multi-slice CT scan is a valuable and valid postoperative assessment tool of accuracy of spinal pedicle screw placement.

Abstract WMP8: Thin-sliced Reformatted CT Imaging: Validation of a Safer and Faster Technique to Assess Clot Size and Vessel Diameter in Large Vessel Occlusions

Background: Thin-sliced reformatted non-contrast CT head are not widely used to detect the thrombus. The purpose of this study was to investigate whether thin-sliced reformatted non-contrast CT scans could be reliably used to detect and measure size of the thrombus size in patients with acute ischemic stroke due to LVO and therefore serve as a potential substitute of CT Angiogram (CTA). Success of this paradigm could reduce stroke decision algorithm to nonenhanced CT scan before a code neurointervention is activated; hence saving time and contrast. Methods: Comprehensive prospective analysis of patients who underwent acute endovascular intervention for LVOs at a community based, university affiliated comprehensive stroke center during one year period (Jan 2015-Dec 2015) was done. The raw data of non-enhanced CT scans and CTAs were collected. All raw data were reconstructed with thin slices of 0.625 mm using standard GE software. Two observers independently evaluated the 5-mm maximum intensity projections of the thin slices and CTA in coronal and axial projections for best assessment of vessel diameter and thrombus length. Inter-observer agreement was measured using Cohen κ. Results: There were 749 patients who presented with acute ischemic stroke during the specified time period. Of those 67 were large vessel circulation strokes; of which, 22 had both CT and CTA done. Mean clot length measured was 14.75 (SD +/-4.95) on thin slices CT and 15.02 (SD +/-5.47) on CTA. Vessel diameter measured was 2.77 (SD +/-0.47) on thin sliced reformatted CT and 2.41 (SD +/-0.49) on CTA. There were no instances where clot size or vessel diameter could not be measured on thin slice reformatted CT. Inter-observer agreement was higher for both CTA (κ, 0.83) versus thin-slice nonenhanced CT reconstructions (κ, 0.80). Conclusions: Thin-sliced reconstructions of standard cranial nonenhanced CT raw data can be reliably used to detect and measure the thrombus size in LVOs. It also reliably measures the vessel diameter, making intervention planning possible. Larger multicenter trials are needed to validate our data.