|Year : 2018 | Volume
| Issue : 2 | Page : 157-162
The role of magnetic resonance imaging in the assessment of acromial morphology in association with rotator cuff tear
Ahmed A Hassan1, Medhat M Refaat2, Islam M El-Shazly2
1 Department of Diagnostic Radiology, Ahmed Maher Teaching Hospital, Cairo, Egypt
2 Department of Diagnostic Radiology, Benha University, Benha, Egypt
|Date of Submission||22-Nov-2016|
|Date of Acceptance||12-Jan-2017|
|Date of Web Publication||17-Aug-2018|
Dr. Ahmed A Hassan
Zagazig, Sharkia, 44511
Source of Support: None, Conflict of Interest: None
Background The pathogenesis of rotator cuff tear (RCT) remains controversial. The acromion portion of the scapula and its morphology may be attributable for a variety of shoulder disorders such as RCT.
Aim The purpose of this article is to throw light on the role of MRI in the assessment of morphological characteristics of different acromial shapes in association with RCTs.
Patients and methods This study was carried out from January to August 2016 at the Ahmed Maher Teaching Hospital Radiodiagnosis Department. We used MRI prospectively to image the shoulders of patients who presented to the radiology department with suspected RCT. Their ages ranged between 20 and 60 years with a mean age 40 years. Data were tabulated and manipulated using SPSS (vi 16), and the level of significance was less than 0.05.
Results The study revealed that type III acromion was encountered in male and female patients (42.9 and 42.1%) and type IV acromion was noticed less frequently among male and female patients, respectively (4.8 and 15.8%). In patients younger than 45 years of age (n=25), type I and type III acromion was the most commonly seen (64%) in both sexes. In patients more than 45 years of age, type III acromion was commonly seen (60%). All age and sex differences were not significant (P>0.2). It also revealed that type III was mostly encountered in full-thickness tear (82.4%) and partial tear (52.9%), whereas type I was less frequently associated with partial tear or full-thickness tear (25%). Type III was associated with tendinopathy, acromioclavicular osteoarthritis, and joint effusion.
Conclusion The acromial shapes were classified into four types. On MRI, acromial shapes were better recognized using the mathematical classification scheme for MRI obtained just lateral to the acromioclavicular joint. This should shed light on the morphological characteristics of different acromial shapes that may be of value in diagnosing and treating subacromial pathologies. Such morphological characteristics include measurements of the acromiohumeral distance, the acromial index, and the lateral acromial angle using T2-weighted MRI coronal oblique images.
Keywords: acromion shapes, magnetic resonance imaging, rotator cuff tear
|How to cite this article:|
Hassan AA, Refaat MM, El-Shazly IM. The role of magnetic resonance imaging in the assessment of acromial morphology in association with rotator cuff tear. Benha Med J 2018;35:157-62
|How to cite this URL:|
Hassan AA, Refaat MM, El-Shazly IM. The role of magnetic resonance imaging in the assessment of acromial morphology in association with rotator cuff tear. Benha Med J [serial online] 2018 [cited 2018 Dec 14];35:157-62. Available from: http://www.bmfj.eg.net/text.asp?2018/35/2/157/239198
| Introduction|| |
MRI of the shoulder provides detailed images of structures within the shoulder joint, including bones, tendons, muscles, and vessels. MRI is a noninvasive medical test that helps diagnose and treat medical conditions. MRI uses a powerful magnetic field, radio-frequency pulses, and a computer to produce detailed pictures of organs, soft tissues, bone, and virtually all other internal body structures. MRI does not use ionizing radiation (X rays). Detailed MRI allow physicians to evaluate various parts of the body and determine the presence of certain diseases . The acromion is a posterior shoulder landmark, formed as a posterolateral extension of the scapular spine, superior to the glenoid. It articulates with the clavicle and is the origin of the deltoid and trapezius muscles. Variation in the shape of the acromion can lead to a variety of pathologies such as impingement syndrome and rotator cuff tear (RCT) .
The acromial shape can be classified into four types: type I (flat), type II (curved), type III (hooked) , and type IV (convex) . Rotator cuff disorder is one of the most common disorders of the shoulder. It is a common cause of chronic shoulder pain in adults. The specific etiology of an RCT has not been fully elucidated, but it has been considered to result from a combination of intrinsic and extrinsic factors. Intrinsic factors include degenerative changes, hypovascularity, and microstructural collagen fiber abnormalities. Recognized extrinsic factors include subacromial impingement, tensile overload, and repetitive use  ([Figure 1]).
|Figure 1 Types of acromial shape: 1, type I or flat type; 2, type II or curved type; 3, type III or hooked type; and 4, type IV acromion shape or convex type |
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| Patients and methods|| |
MRI from 40 patients with chronic shoulder pain and positive clinical data were reviewed prospectively. The study was approved by Scientific Research Committee of Benha University. An informed consent is taken from all participants. These patients did not have previous surgery, fracture, or tumors of the shoulder. They underwent conventional MRI from January 2016 to August 2016. Their ages ranged between 20 and 60 years, with a mean age 40 years.
Magnetic resonance imaging
MRI was performed using a 1.5-T scanner (GyroscanIntera 1.5 T Master; Philips, Best, the Netherlands) with a 200-mm Synergy Flex L Coil, a shoulder Coil (Philips).
Conventional magnetic resonance imaging
- We obtained the Preliminary Scout Localizer in the axial, sagittal, and coronal planes.
- Coronal oblique T1 (TSE, TR 664, TE 18, FOV 14, SL 4, MTARIX 205/512, NSA 3).
- Coronal oblique T2 (TSE, TR 2411, TE 100, FOV 14, SL 4, MTARIX 201/512, NSA 2).
- Coronal oblique STIR (TSE, TR 2411, TE 15, FOV 14, SL 4, MTARIX 201/512, NSA 2).
- Coronal oblique PD (TSE, TR 1400, TE 16, FOV 18, SL 4, MTARIX 201/512, NSA 3).
- Axial GR (TSE, TR 551, TE 18, FOV 17, SL 4, MTARIX 179/512, NSA 3).
- Sagittal oblique T2 (TSE, TR 3342, TE 100, FOV 16, SL 4, MTARIX 205/512, NSA 3).
All collected data revised for completeness and accuracy. Precoded data were entered into the computer using the Statistical Package for the Social Sciences (SPSS) version 16 (SPSS Inc., Chicago, Illinois, USA), to be statistically analyzed. Data were summarized using the number and percent for qualitative variables. Comparison between qualitative variables was performed using the χ2-test for qualitative variables. P-values less than 0.05 were considered to be statistically significant.
| Results|| |
The sex and age distribution of our patients are shown in [Table 1] and [Table 2]. Type III acromion was encountered more commonly in male and female patients (42.9 and 42.1%) and type IV acromion less frequently among male and female patients, respectively (4.8 and 15.8%). In patients younger than 45 years of age (n=25), type I and type III acromion was the most commonly seen (64%) in both sexes. In patients more than 45 years old, type III was commonly seen (60%). All age and sex differences were not significant (P>0.2).
|Table 1 Distribution of acromial types in patients with relation to the sex|
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|Table 2 Distribution of acromial types in relation to patients’ age group|
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[Table 3] shows the distribution of acromial types in association with partial and full-thickness tears. Type III was encountered mostly in full-thickness tear (82.4%) and partial tear (52.9%), whereas type I was less frequently associated with partial tear or full-thickness tear (25%). [Table 4] shows the distribution of acromial types in association with different radiological findings. We noticed that type III was associated with tendinopathy, acromioclavicular osteoarthritis, and joint effusion ([Figure 2] and [Table 5]).
|Table 3 Association of different acromial types with partial thickness rotator cuff tear in the studied patients (n=40).|
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|Table 4 Association of different acromial types with full-thickness rotator cuff tear in the studied patients (n=40)|
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|Figure 2 Mathematical determination of the acromial morphology. A line connecting most caudal points of the acromial undersurface was drawn on the parasagittal T2-weighted MRI, and with the help of two orthogonal lines, the acromion was divided into three segments of equal lengths. Then, the angle between the anterior third and the posterior two-thirds was measured|
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|Table 5 Comparison between different acromial shapes in patients with rotator cuff tear and acromial measurements including acromial thickness, acromiohumeral distance, acromion index, and lateral acromial angle|
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| Discussion|| |
In the present study, we found that the type III acromial shape (43.8%) was encountered more often and type IV (6.3%) less frequently among male patients, although there was no significant difference in terms of age and sex (P>0.2); with regard to the distribution of different acromial shapes, we noticed that the type IV acromial shape was not seen in patients older than 45 years of age, whereas type III was present in 63.6% of patients older than 45 years of age, which did not match with the findings of a previous study conducted by Paraskevas et al.  (44 pairs of dried scapulas were reviewed). They noted that type I acromion was significantly more common in female patients (13 or 56.5% vs. 10 or 43.4%), whereas type III was significantly more common in male patients (9 or 56.2% vs. 7or 43.7% in female patients); this could be explained by the higher number of patients in their study compared with this study. In the current study, the mean acromion thickness in patients with RCT was significantly greater (P>0.025). Although this was in accordance with the conclusion of previous studies ,, there was a slight difference regarding the mean acromial thickness in patients with RCT: it was 8.8 mm in the study by Paraskevas et al. , 8.5 mm in the study of Collipal et al.  (the study included 36 scapulae at the museum of the Anatomy Unit, Universidad de La Frontera), and 8.3 mm in the study by Oh et al.  (the study included 106 patients with full-thickness RCTs and 102 patients without tears), but it was 8.6 mm in our study. Variations of the acromial morphology known as ‘congenital and osteal etiological factors’ may contribute to RCT and play subsidiary roles in diagnosing the rotator cuff injury. They include the acromial shape, lateral acromial extension or acromial index, the angle between the undersurface of the acromion and the glenoid or lateral acromial angle (LAA), and the distance from the acromion to the humeral head . Nyffeler et al.  (their study included 102 patients with a proven full-thickness RCT, 47 patients with osteoarthritis of the shoulder and an intact rotator cuff, and 70 volunteers as the control group) first described the concept of acromion index (AI), which could directly express the lateral extension degrees of acromion. In addition, it could be considered as the coverage degree of acromion onto the subacromial tissue. Furthermore, Banas et al.  first identified the concept of LAA, which was defined as the slope of the inferior surface of the acromion relative to the scapular glenoid plane. In addition, the acromiohumeral distance (AHD) that was measured as the smallest interval from the inferior surface of the acromion to the superior aspect of the humerus has important clinical significance. As several soft tissues pass through this arch, such as the infraspinatus, supraspinatus, and subacromial bursa, narrowing of this distance indicates the superior migration of humeral head, which has been associated with the tearing of the rotator cuff tendons, especially the supraspinatus tendon . Acromial measurements of the AI and the LAA determine the shape of the acromion, which may represent a useful marker to confirm the relationship with RCT .
As our aim was to evaluate the acromial morphological variations in association with RCT, these measurements revealed a significantly thicker acromion (P=0.025) with significantly shorter AHD, a larger AI, and a smaller LAA (P<0.001 for each parameter) in patients with RCT. Furthermore, on comparing these measurements between each of the four acromial types in patients with RCT, we found that all these acromial measurements, including the acromion thickness, AHD, AI, and LAA, were significantly deferent in type III acromion shape as compared with the study conducted by Mohamed and Abo-Sheisha  [the study included 56 patients with RCT (either partial or full-thickness tear) and 30 control volunteers]. In addition, Guishan and Ming  discussed the clinical significance of measuring AI, LAA, and AHD, and they considered such measurements as morphological variations of the acromion and named them as ‘congenital and osteal etiological factors’ for RCT. Type III (hooked) acromion was strongly associated with RCT and may be a result of tractional damage to the tendon. In contrast, type I (flat) acromion may have an insignificant involvement in cuff disease and accordingly may be best treated conservatively .Paraskevas et al.  studied the clinical significance of the shape of the anterior third of the acromion in relation to impingement syndrome as well as RCT. They reported that in hooked acromion, the reduced dimensions of the subacromial space can explain such a relation, which more often leads to impingement of the rotator cuff tendon and subsequent tear production. In the present study, we found a insignificant correlation of type III acromial shape with RCT (P=0.06). However, other studies  reported that the incidence of type III acromion shape in patients with RCT is not highly significant and it does not always correlate with the occurrence of RCT, but the RCT size is significantly larger in type III acromion rather than in other acromion shapes .
The shape and size of the acromion are due to the fusion of the three ossification centers called meta-acromion, mesoacromion, and preacromion, which are recognizable at the age of 18 years. At this age, another nucleus, the basiacromion, has fused entirely with the spine of the scapula. Thereafter, the meta-acromion fuses to the scapula, whereas the preacromion and mesoacromion fuse at first to each other and then from the 21st to 22nd years onwards to other portions of the scapula and the entire process is completed in the mid 20s. If these ossification centers persist, different types of os acromiale could be recognized. These types include the os acromiale commune, which is a result of failure in fusion between the meta-acromion and mesoacromion, and the os acromiale terminal, which is a consequence of failure in fusion between the preacromion and mesoacromion. Nonfusion of the mesoacromion with the meta-acromion is the most common type of os acromiale. In the current study, we reported only one case of os acromiale associated with type II acromion, but not causing any symptoms which does not match with the findings of the study conducted by Mohamed and Abo-Sheisha , who reported only one case of os acromiale that was of type III acromial shape associated with partial thickness tear of the supraspinatus tendon. MRI demonstrated the existence of an unfused bony ossicle that was best recognized on axial images.
Os acromiale is one of the rare causes of RCTs and impingement syndrome. When the deltoid muscle contracts, it can cause inferior displacement of an unfused acromion fragment, thus impinging the rotator cuff. Furthermore, abnormal motion of the unstable segment at the fibrous union site may cause pain and RCT. The os acromiale can also decrease the volume of the subacromial space and cause impingement syndromes in some cases. In the study conducted by DeLee , a statistically significant correlation was found between RCT and osteoarthritis, which is similar to our study (P<0.049), which is encountered among type III acromion shapes (69.2%). There were some limitations to our study. First, the rotator cuff tendons may be mechanically irritated by some other morphological factors that were not included in this study. The small number of patients was another limitation. Therefore, further studies with more considerable number of patients are recommended to elucidate these factors and completely confirm the relationship between the acromion morphology and RCT.
| Conclusion|| |
Our findings may help guide therapy in patients with shoulder pain and findings suggesting a type III acromion shape. Specifically, patients presenting with nontraumatic shoulder pain may benefit from early physical therapy and intervention if findings on MRI suggest impingement. Early intervention may prevent ultimate tears of the rotator cuff and could possibly reduce morbidity with aging ([Figure 3]).
|Figure 3 (a–d): A 49-year-old female patient presented with chronic right shoulder pain. Conventional MRI coronal and sagittal oblique (T1WI, T2WI, STAIR) images showing type IV acromion shape, a thickened supraspinatus tendon with abnormal signal within and disruption of its fibers at it is bursal surface, subacromial bursitis, and mild joint effusion|
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Ahmed Maher Teaching Hospital, Misr Radiology Center provided equipment for this study.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]