01 August 2022: Clinical Research
Identification of Diagnostic Magnetic Resonance Imaging Findings in 47 Shoulders with Subcoracoid Impingement Syndrome by Comparison with 100 Normal ShouldersJia-feng Yu1ABCDEFG, Ping Xie2ABCDEF, Ke-fu Liu1ABCDEFG*, Yan Sun1ABCD, Jing Zhang1ABCD, Hui Zhu1ABCD, Yue-hao Chen1ABCD
Med Sci Monit 2022; 28:e936703
BACKGROUND: The aim of this study was to identify the diagnostic magnetic resonance imaging (MRI) findings in 47 shoulders with subcoracoid impingement syndrome by comparison with 100 normal shoulders.
MATERIAL AND METHODS: The subcoracoid impingement syndrome group consisted of 47 shoulders with subcoracoid impingement syndrome and the normal group consisted of 100 normal shoulders. The MRI parameters – coracoids-humeral distance (CHD), coracoid index (CI), height of the lesser tuberosity (HLT), coracoid obliquity (CO), coracoglenoid angle (CGA), coracohumeral angle (CHA), width of the subscapular tendon (WST), and contact distance between subscapular tendon and coracoid process (CD) – were compared between the subcoracoid impingement syndrome group and the normal group. The areas under the curves (AUCs) from the receiver operating characteristic (ROC) for single MRI parameters were recorded, in which the MRI parameters with AUC exceeding 0.70 were included in the analysis of combined parameters. Comparisons of ROC were made among single parameters and combined parameters.
RESULTS: For diagnosing subcoracoid impingement syndrome by using single MRI parameters (CHD, CI, HLT, CGA, CHA, WST, and CD), the AUCs were 0.963, 0.806, 0.745, 0.691, 0.613, 0.685, and 0.614, respectively, of which CHD had the largest AUC. CHD, CI, and HLT (AUC exceeding 0.70) were included in the study of the combined parameters. The AUC of combined CHD and HLT showed a significantly larger AUC than that of CHD (0.986 vs 0.963, P=0.036), and showed no significant difference compared with that of combined CHD, CI, and HLT (0.986 vs 0.987, P=0.882).
CONCLUSIONS: Measurement of the coracoid–humeral distance and height of the lesser tuberosity were key MRI diagnostic findings for subcoracoid impingement syndrome.
Keywords: Magnetic Resonance Imaging, Shoulder Impingement Syndrome, coracoid process
Subcoracoid impingement syndrome is defined as impingement of the anterior soft tissues of the shoulder between the coracoid process and the lesser tuberosity, which causes fiber failure and damage, then partial or complete tearing of the subscapularis tendon, resulting in anterior shoulder pain [1–10].
There were some studies discussing the imaging index for diagnosing subcoracoid impingement syndrome. Some studies have shown that the coracohumeral distance (CHD) is the predictor for subcoracoid impingement syndrome on plain film, CT, and MRI [11–14], and the excessive extension of the coracoid process and variants in the lesser tuberosity anatomy are associated with subcoracoid impingement syndrome [4,11,15]. Other authors report that an increase in overall size of the tendon and disproportionate contact of the rotator cuff with surrounding structures were also associated with subcoracoid impingement syndrome [16–18]. Additionally, some angles, such as the coracoglenoid angle and coracohumeral angle, have been found to be indices for subcoracoid impingement syndrome [3,19,20].
However, other studies have shown different results. Radas and Pieper  found no correlation between the coracohumeral interval and subscapularis injury. Bergin et al  reported no significant relationship between the measured subcoracoid interval and severity of subscapularis tendon abnormalities. Some studies showed no correlation between subscapularis injury and MRI parameters [22,23].
We know that impingement syndrome is related to the position of anatomical structures in three-dimensional space; these studies with a single parameter are limited because subcoracoid impingement syndrome arises from a three-dimensional pathology . We speculate that the diagnostic value of combining multiple parameters of MRI is better than that of a single parameter. Therefore, the purpose of this study was mainly to identify the diagnostic magnetic resonance imaging (MRI) findings in 47 shoulders with subcoracoid impingement syndrome by comparison with 100 normal shoulders.
Material and Methods
This study was approved by the Ethics Committee of Suzhou Municipal Hospital (approval no. KL901228). The requirement for informed consent was waived owing to the retrospective nature of the study.
This study included 100 normal shoulders and 47 shoulders with subcoracoid impingement syndrome. The diagnostic criteria of subcoracoid impingement syndrome are as follows: (1) MRI findings include narrowed subcoracoid space, increased signal and fraying of the subscapularis tendon; (2) tenderness of the soft tissue around the coracoid process or between the coracoid process and lesser tuberosity; (3) shoulder apprehension test can induce anterior shoulder pain, and the pain is relieved after retesting; (4) coracoid impingement test or modified Kennedy-Hawkins impingement sign was positive, and turned negative after subcoracoid infiltration of local anesthetics [15,24]. A total of 47 patients diagnosed with subcoracoid impingement syndrome (19 males and 28 females) undergoing shoulder MRI, with mean age of (47.19±10.08) and age range from 34 to 70 years, were included in this study. All of them had single shoulder disease, including 24 cases of right shoulder and 23 cases of left shoulder.
The range of the course on subcoracoid impingement syndrome was from 1 month to 1 year. All patients underwent a comprehensive shoulder physical examination before MRI. The normal group consisted of 100 volunteers. The inclusion criteria of normal group are as follows: no history of chronic shoulder pain, with normal shoulder function, no history of shoulder trauma and surgery, no obvious MRI features of subcoracoid impingement syndrome. The normal group included 51 males and 49 females, aged 24–76 years, with an average age of (48.74±12.14).
MRI TECHNIQUE AND MEASUREMENTS:
All MRI examination were performed using the 1.5 Tesla MRI system (Avanto 1.5T, Siemens, Berlin, Germany). All subjects lay in supine position with a loop coil around the shoulder. MRI was performed with the arm in neutral position. The scanning parameters are shown in Supplementary Table 1.
The coracoid-humeral distance (CHD) is defined as the minimal distance between the coracoid process and lesser tuberosity on an axial image [3,11]. The coracoid index (CI) is defined as the distance between coracoid process and glenoid process on an axial image . The height of the lesser tuberosity (HLT) was defined as the length of the line through the highest point inside and outside the intertubercular sulcus and the parallel line through the bottom of the intertubercular sulcus. The coracoid obliquity (CO) was defined as the angle between the axis of the coracoid process and a horizontal line on the coronal image. The coracoid-glenoid angle (CGA) was measured as the angle between a line along the plane of the glenoid face and the apex of the coracoid on the axial image . The coracoid-humeral angle (CHA) was measured as the included angle between the internal and external tangent lines of the humeral head through the tip of the coracoid process on the axial image . The width of the subscapular tendon (WST) is the width of the subscapular tendon measured at the layer with the minimum CHD. The contact distance between subscapular tendon and coracoid process (CD) was defined as the distance between the superior edge of subscapular tendon and lower edge of the coracoid process. The detailed measurement is shown in Supplementary Figure 1. All measurements were performed independently by 2 radiologists using Neusoft PACS software (version 188.8.131.5275) and the average value was taken.
Statistical analysis was performed using SPSS software (version 26, IBM, Armonk, NY, USA). Data were expressed as mean±standard deviation. The age difference between groups was tested by the independent-samples
To determine the best cut-off points, receiver operating characteristic (ROC) curves were designed for each studied variable and the Youden index was applied. The corresponding value with the highest Youden index was considered as the cut-off value with the best precision. Further analysis of the combined parameters included the MRI parameters with AUC exceeding 0.70. MedCalc software (version 9.6.2, MedCalc, Belgium) was used to compare ROC among single parameters and combined parameters.
The normal group (average age 56±14 years) included 51 men and 49 women, and the subcoracoid impingement syndrome group (average age 64±12 years) included 19 men and 28 women. The normal group included 48 left and 52 right shoulders, and the subcoracoid impingement syndrome group included 23 left and 24 right shoulders. There was no significant difference between the normal group and subcoracoid impingement syndrome group in age (t=1.017, P=0.136), sex, or left-and-right side (χ2=1.433, P=0.231; χ2=0.011, P=0.916) (Table 1).
The CHD, CI, HLT, CO, CGA, CHA, WST, CD of the normal group were 7.7±1.5mm, 16.0±3.3mm, 5.5±1.0 mm, 8.9±2.9°, 132.6±8.5°, 106.7±9.5°, 5.4±1.3 mm, and 8.9±2.3 mm, respectively. The CHD, CI, HLT, CO, CGA, CHA, WST, and CD of subcoracoid impingement syndrome group were 4.7±1.2 mm, 20.1±3.3 mm, 6.6 ±1.4 mm, 9.3±3.0°, 126.8±9.6°, 110.2 ±10.5°, 6.4±1.8 mm, and 10.5±3.8 mm, respectively. The CHD, CI, HLT, CGA, CHA, WST, and CD between subcoracoid impingement syndrome group and normal group showed significant differences (Z=−9.043, P<0.001; Z=5.981, P<0.001; Z=4.787, P<0.001; Z=−3.731, P<0.001; Z=2.205, P=0.027; Z=3.623, P<0.001; Z=2.233, P=0.026) (Table 2; Figures 1–3).
Using a single parameter for diagnosing subcoracoid impingement syndrome, the area under the curve (AUC) of CHD, CI, HLT, CGA, CHA, WST, and CD were 0.963, 0.806, 0.745, 0.691, 0.613, 0.685, and 0.614, respectively (Figure 4), in which CHD showed the largest AUC.
The parameters (CHD, CI, HLT) with AUC exceeding 0.70 were included in the study of the combined parameters. When the cut-off values were 5.9 mm, 16.5 mm, 5.5 mm for CHD, CI and HLT, respectively, the sensitivity and specificity were 89.4% and 92.0%, 85.1% and 61%, 83% and 57%, respectively. Compared with the AUC using a single CHD for diagnosing subcoracoid impingement syndrome, the combined CHD and CI did not have a significantly different AUC (0.968 vs 0.963, P=0.645), the combined CHD and HLT had a significantly larger AUC (0.986 vs 0.963, P=0.036), and the combined CHD, CI, and HLT also had a significantly larger AUC (0.987 vs 0.963, P=0.022). The AUC of combined CHD and HLT showed no significant difference compared with that of combined CHD, CI, and HLT (0.986 vs 0.987, P=0.882) (Figure 5).
LIMITATIONS OF THIS STUDY ARE AS FOLLOWS:
First, the sample size of subcoracoid impingement syndrome in this study was not large enough, and future studies should include more cases for detailed analysis. Second, dynamic MRI may have better value for diagnosing subcoracoid impingement syndrome. Third, in this study, the clinical application scanning parameters were used. Although the scanning thickness was slightly thicker, the conclusions of our study can directly guide clinical work.
Measurement of the coracoid-humeral distance and height of the lesser tuberosity were key MRI diagnostic findings for subcoracoid impingement syndrome.
FiguresFigure 1. The CHD (3.98 mm) of subcoracoid impingement syndrome (A) was narrower than that of the normal shoulder (7.20 mm) (B). (Avanto 1.5T, Siemens; Neusoft PACS software, version 184.108.40.20675, Neusoft). CHD – coracoid-humeral distance. Figure 2. The CI (22.17 mm) of subcoracoid impingement syndrome (A) was longer than that of the normal shoulder (15.52 mm) (B). (Avanto 1.5T, Siemens; Neusoft PACS software, version 220.127.116.1175, Neusoft). CI – coracoid index. Figure 3. The HLT (7.88 mm) of subcoracoid impingement syndrome (A) was higher than that of normal shoulder (5.74 mm) (B). (Avanto 1.5T, Siemens; Neusoft PACS software, version 18.104.22.16875, Neusoft). HLT – height of lesser tuberosity. Figure 4. The ROC curves of CHD, CI, HLT, CGA, CHA, WST, and CD for diagnosing subcoracoid impingement syndrome. (SPSS software, version 26, IBM). ROC – receiver operating characteristic curve; CHD – coracoids-humeral distance; CI – coracoid index; HLT – height of lesser tuberosity; CO – coracoid obliquity; CGA – coracoglenoid angle; CHA – coracohumeral angle; WST – width of the subscapular tendon; CD – contact distance between subscapular tendon and coracoid process. Figure 5. The ROC curves of combined MRI parameters for diagnosing subcoracoid impingement syndrome. (SPSS software, version 26, IBM). ROC - receiver operating characteristic curve; CHD – coracoids-humeral distance; CI – coracoid index; HLT – height of lesser tuberosity.
TablesTable 1. Comparison of sex, left-and-right side, and age between normal and subcoracoid impingement syndrome groups. Table 2. Comparison of CHD, CI, HLT, CO, CGA, CHA, WST, and CD between normal and subcoracoid impingement syndrome group. Supplementary Table 1. The MRI sequences and parameters for shoulder.
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