Shuang Cong1,2, Shaohua Liu1, Yuxie Xie3, Zhiwen Luo1, Jiwu Chen1. 1. Department of Sports Medicine, Huashan Hospital, Fudan University, Shanghai, China. 2. Department of Orthopedics, Academy of Orthopedics-Guangdong Province, Orthopedic Hospital of Guangdong Province, The Third Affiliated Hospital of Southern Medical University, Guangzhou, China. 3. Department of Radiology, Huashan Hospital, Fudan University, Shanghai, China.
Abstract
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.
BACKGROUND: Three-dimensional computed tomography (3D-CT) is commonly used for the evaluation of camdeformity; 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 camdeformity, 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 camdeformity differed among the oblique axial, oblique coronal, and radial views, with the radial view showing the greatest area.
Authors: Thomas D Alter; Derrick M Knapik; Martina Guidetti; Alejandro Espinoza; Jorge Chahla; Shane J Nho; Philip Malloy Journal: Orthop J Sports Med Date: 2022-05-06