The glenoid version of the shoulder joint correlates with the stability of the glenohumeral joint and the clinical results of total shoulder arthroplasty. We sought to analyze and compare the glenoid version measured by traditional axial two-dimensional (2D) computed tomography (CT) and three-dimensional (3D) reconstructed images at different levels.
A total of 30 cases, including 15 male and 15 female patients, who underwent 3D shoulder CT imaging was randomly selected and matched by sex consecutively at one hospital. The angular difference between the scapular body axis and 2D CT slice axis was measured. The glenoid version was assessed at three levels (midpoint, upper one-third, and center of the lower circle of the glenoid) using Friedman’s method in the axial plane with 2D CT images and at the same level of three different transverse planes using a 3D reconstructed image.
The mean difference between the scapular body axis on the 3D reconstructed image and the 2D CT slice axis was 38.4°. At the level of the midpoint of the glenoid, the measurements were 1.7°±4.9° on the 2D CT images and −1.8°±4.1° in the 3D reconstructed image. At the level of the center of the lower circle, the measurements were 2.7°±5.2° on the 2D CT images and −0.5°±4.8° in the 3D reconstructed image. A statistically significant difference was found between the 2D CT and 3D reconstructed images at all three levels.
The glenoid version is measured differently between axial 2D CT and 3D reconstructed images at three levels. Use of 3D reconstructed imaging can provide a more accurate glenoid version profile relative to 2D CT. The glenoid version is measured differently at different levels.
The glenoid version of the shoulder joint is correlated with the stability of the glenohumeral joint and clinical results of total shoulder arthroplasty [
The glenoid version is reported from 2° anteversion to 9° retroversion and varies among individuals and races [
However, the measurement process may be affected by patient posture in a variety of ways, such as if the scapular position is not aligned with the axis of the CT scanner. There is a report suggesting that scapular rotation in the coronal and sagittal planes will affect the variation of the measured glenoid version, highlighting in particular that 0.42° of anteversion was gained with 1° of scapular abduction in the coronal plane [
There are image software programs that offer the capacity for three-dimensional (3D) reconstruction based on 2D CT images. Using these programs, it is possible to measure and analyze the reconstructed image by freely rotating the image in 3D. Moreover, it is possible to print models using 3D printing technology [
Our hypothesis was that differences exist between the glenoid version measured with axial 2D CT and 3D reconstructed imaging, respectively. This thought arose from the discrepancy between the axis of the CT scanner and the scapula position, which can be changed by patient posture. Therefore, the purpose of this study was to analyze and compare the glenoid version measured with traditional axial 2D CT and with 3D reconstructed imaging, respectively.
This study was approved by the Institutional Review Board of Eunpyeong St. Mary’s Hospital (IRB No. PIRB-20200305-005).
A total of 30 cases, including 15 male and 15 female patients, who underwent shoulder 3D CT was consecutively selected and matched by sex at one hospital. Patients with glenoid fracture, previous shoulder operation, deformity due to severe glenoid wear or erosion, or poor CT scan quality were excluded. The mean age of male patients was 52.5 years (range, 28–72 years) and that of female patients was 64.0 years (range, 22–84 years).
Shoulder 3D CT (Optima CT 660; GE Healthcare, Chicago, IL, USA) scans were collected with the patient in the supine position. A free open-source software program, ITK snap (version 3.4.0; United States National Institute of Biomedical Imaging and Bioengineering, Bethesda, MD, USA) [
A scapular coronal plane as a reference plane, based on the method introduced by Kwon et al. [
The glenoid version can be measured ideally when the 2D CT slice axis is orthogonal to the scapular body axis. The 2D CT slice axis was established by use of the scout image function in a PACS (picture archiving and communication) system (Marosis M-view version 5.4; Marotech, Seoul, Korea). We checked for an angular difference between the scapular body axis and the actual 2D CT slice axis (
The glenoid version was measured at three levels, including the upper one-third of the glenoid, midpoint of the glenoid, and center of the lower circle of the glenoid. A center point bisecting the anatomical glenoid axis (i.e., at the midpoint of the glenoid) was chosen because it represents the base plate position in anatomical total shoulder arthroplasty. The center of the lower circle of the glenoid was chosen because it is the center peg hole of the base plate for reverse total shoulder arthroplasty. On axial 2D CT scans of these three levels, the glenoid version was measured (
Here, a 3D reconstructed image was sliced along the transverse scapular plane orthogonal to the scapular coronal plane. The axial 3D slice was taken at the same three levels as those chosen for assessment on the 2D CT scans (
Measured glenoid versions were compared between the 2D CT scans and the 3D reconstructed image at each of the three levels. The IBM SPSS ver. 24.0 (IBM Corp., Armonk, NY, USA) was used for all statistical analyses. The Kolmogorov-Smirnov test was used for normal distribution assessments of all measurements. A paired t-test and the signed rank-test were used to compare the glenoid version between the data from 2D CT scans and 3D reconstructed images, respectively. An analysis of variance and the Kruskal-Wallis test were chosen to compare the glenoid version between the 2D CT images and 3D reconstructed image at each level. Significance levels for all analyses were set at P < 0.05.
The mean angle between the 2D CT slice axis and the scapular body axis on the 3D reconstructed image was 38.4°. The mean glenoid version measured at the level of the upper one-third of the glenoid was −3.6°±4.5° on the 2D CT images and −4.5°±5.7° on the 3D reconstructed image. At the level of the glenoid center, the glenoid version was measured as 1.7°±4.9° on the 2D CT images and −1.8°±4.1° on the 3D reconstructed image. Finally, the mean glenoid version measured at the level of the center of the lower circle of the glenoid was 2.7°±5.2° on the 2D CT images and −0.5±4.8° on the 3D reconstructed image. A statistically significant difference was found between the glenoid version measured on the 2D CT images and 3D reconstructed image at all three levels (P=0.003, P=0.000, and P=0.000, respectively) (
Considering results of the same modality, a statistical difference was found among the three levels between 2D CT scans (P=0.000) and 3D reconstructed images (P=0.007). During a multiple comparison test, a statistical difference was found between the upper one-third of the glenoid and the midpoint of the glenoid (P=0.000) and between the upper one-third and the center of the lower circle of the glenoid (P=0.000) on the 2D CT images. During a multiple comparison test of the 3D reconstructed image, a statistical difference was found between the upper one-third of the glenoid and the center of the lower circle of the glenoid (P=0.006). All angles were measured by two orthopedic surgeons (HK and HSS) independently. The interclass correlation coefficient was greater than 0.9.
In this study, there was a significant difference in glenoid version between measurements collected from routine axial 2D CT scans and a 3D reconstructed image at three levels of the glenoid. Thus, the glenoid version could be different depending on the level of measurement and whether 2D axial CT scans or a 3D reconstructed image is assessed. Restoring the glenoid version anatomically is important when performing shoulder arthroplasty since it affects the clinical results [
In most of the available reports in the literature, the glenoid version was measured on axial 2D CT scans. In the study by Nyffeler et al. [
To overcome this discrepancy, Kwon et al. [
Considering that ideal glenoid version can be achieved when the superoinferior axis of glenoid—that is, the coronal plane of the scapula—is orthogonal to the axis of a 2D CT scanner, this study suggested that it is not easy to match this axis in real-world clinical circumstances. Patients may experience difficulties maintaining the necessary position due to pain, anxiety, medical comorbidities, or body habitus. Technicians might face challenges in positioning patients in the right position due to variations among patients’ spine curvatures or the anterior tilt of the glenoid itself. As a result, the scanning process may proceed without proper perception of the patient position, which would make it difficult to obtain an accurate scapula axis and which can lead to inaccurate measurements of the glenoid version. Indeed, a difference of 38.4°, which is quite a large variation from 90°, was observed in this study.
The glenoid version is mostly measured on axial 2D CT scans. To assess the difference of the glenoid version measured at different levels, the glenoid version was measured not only at the midpoint of the glenoid, but at levels superior and inferior to the center of the glenoid. From this, it was revealed that the glenoid version was different depending on the level at which measurements are performed. Lewis and Armstrong [
This study had some limitations. The sample size of each group was relatively small. Because glenoids with deformities were excluded from this study, more studies should be completed to validate our measurement method in patients with arthritis or other defects of the glenoid. However, by measuring the glenoid version on the 3D reconstructed image, no effect of patient positioning was apparent, which is a strength of this research.
In this study, by accurately selecting the transverse planes on the 3D reconstructed image, comparison with axial 2D CT images was possible. This study has significant value to facilitate clinical improvement given the availability of easy access to the 3D reconstruction program. Also, it is meaningful that the angular difference between the scapular body axis and 2D CT slice axis was analyzed. In this investigation, the glenoid version was measured differently between axial 2D CT scans and a 3D reconstructed image at three levels. The 3D reconstructed image provided more accurate glenoid version data relative to the 2D CT scans. Finally, the glenoid version is measured differently at different levels.
None.
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ITK SNAP (version 3.4.0) was used for reconfiguring computed tomography axial images into the three-dimensional structure image.
Meshmixer (version 3.0) was used to edit and rotate the three-dimensional reconstructed image.
Scapular plane. (A) The scapular coronal plate, as the reference plane, was defined by connecting the inferior tip of the scapular body, medial pole of the scapula, and the midpoint of the glenoid surface. (B) The scapular coronal plane was demonstrated on the three-dimensional constructed image with the Meshmixer software. (C) The transverse scapular plane was marked orthogonally to the scapular coronal plane.
The angle between the axis of a standard axial two-dimensional computed tomography (2D CT) scan (orange line) and the scapula body axis (yellow line) was measured.
The glenoid version as measured on an axial two-dimensional computed tomography scan. (A) The level of measurement at the upper one-third of the glenoid. (B) The glenoid version at the upper one-third of the glenoid. (C) The level of measurement at the center of the glenoid. (D) The glenoid version at the center of the glenoid. (E) The level at the center of the lower plane. (F) The glenoid version at the center of the lower circle of the glenoid.
The glenoid version as measured on the three-dimensional (3D) reconstructed image. (A) The 3D reconstructed image showing three transverse planes. (B) The glenoid version as assessed at the upper one-third transverse plane. (C) The glenoid version as assessed at the center of the glenoid. (D) The glenoid version as assessed at the center of the lower circle of the glenoid.
Mean glenoid version on the 2D CT images and 3D reconstructed image (minus value represents retroversion)
Level of the glenoid | 2D CT | 3D reconstruction | P-value |
---|---|---|---|
Upper one-third (°) | −3.6±4.5 | −4.5±5.7 | 0.003 |
Center (°) | 1.7±4.9 | −1.8±4.1 | 0 |
Center of the lower circle (°) | 2.7±5.2 | −0.5±4.8 | 0 |
P-value |
0 | 0.007 |
Values are presented as mean ± standard deviation.
2D: two-dimensional, CT: computed tomography, 3D: three-dimensional.
Paired
Analysis of variance.