Radiographic and magnetic resonance imaging-based evaluation of supraspinatus impingement syndrome – A narrative review

Megha Manoj; Shivali Vaibhav Kashikar; Rajasbala Pradeep Dhande; Gaurav Vedprakash Mishra

doi:10.4103/jdmimsu.jdmimsu_437_21

REVIEW ARTICLE

Year : 2022 | Volume : 17 | Issue : 4 | Page : 1005-1008

Radiographic and magnetic resonance imaging-based evaluation of supraspinatus impingement syndrome – A narrative review

Megha Manoj, Shivali Vaibhav Kashikar, Rajasbala Pradeep Dhande, Gaurav Vedprakash Mishra
Department of Radio-Diagnosis, JNMC, DMIMS, Wardha, Maharashtra, India

Date of Submission	29-Nov-2021
Date of Decision	10-May-2022
Date of Acceptance	05-Jun-2022
Date of Web Publication	10-Feb-2023

Correspondence Address:
Dr. Megha Manoj
Department of Radio-Diagnosis, JNMC, DMIMS, Wardha, Maharashtra
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jdmimsu.jdmimsu_437_21

Abstract

Shoulder pain is a common debilitating problem affecting both young as well as elderly people. Its prevalence varies from 6-11% in young adults to 16-25% in elderly. Supraspinatus Impingement syndrome is the most common impingement syndrome causing shoulder pain. Primary or secondary reduction of subacromial distance due to morphological differences of acromion, acromial osteophytes, superior migration of humeral head etc. are predisposing factor for supraspinatus impingement. The aim of this review article is to understand the relevant anatomy of subacromial space and review supraspinatus impingement syndrome and its association with subacromial distance and acromion morphology. Literature search was conducted on PubMed and Google Scholar databases using MeSH terms – 'subacromial distance', 'Supraspinatus Impingement syndrome', 'Acromion', 'MRI'. 8 studies from 2006 to 2021 have been included for review. It was observed that subacromial distance and lateral acromial angle are lower in patients with supraspinatus impingement compared to the general population. Whereas the acromion index is higher in impingement syndrome. Evaluation of supraspinatus impingement syndrome can be done reliably using specialized radiographic views and MRI. Extrinsic factors like reduced subacromial distance and acromion morphology are predisposing factors for impingement of supraspinatus tendon.

Keywords: Acromion, magnetic resonance imaging, subacromial distance, supraspinatus impingement syndrome

How to cite this article:
Manoj M, Kashikar SV, Dhande RP, Mishra GV. Radiographic and magnetic resonance imaging-based evaluation of supraspinatus impingement syndrome – A narrative review. J Datta Meghe Inst Med Sci Univ 2022;17:1005-8

How to cite this URL:
Manoj M, Kashikar SV, Dhande RP, Mishra GV. Radiographic and magnetic resonance imaging-based evaluation of supraspinatus impingement syndrome – A narrative review. J Datta Meghe Inst Med Sci Univ [serial online] 2022 [cited 2023 Apr 1];17:1005-8. Available from: http://www.journaldmims.com/text.asp?2022/17/4/1005/369505

Introduction

Shoulder pain is a common debilitating problem affecting both young and elderly people. Its prevalence varies from 6% to 11% in young adults and 16% to 25% in the elderly.^[1] Chronic shoulder pain can cause disability and abstinence from work, thereby affecting an individual emotionally, physically, and economically. Risk factors for shoulder pain include age, obesity, diabetes, and occupation.^[2] Rotator cuff injury, frozen shoulder, and arthritis including osteoarthritis and rheumatoid arthritis are some of the most common causes of shoulder joint. Out of these, rotator cuff injuries account for more than two-thirds of shoulder pain cases.^[3]

Rotator cuff injuries commonly occur due to degenerative changes of shoulder joint or trauma. Several predisposing factors such as age, sex, hand dominance, smoking, hypercholesterolemia, posture, occupation, and family history have been attributed to rotator cuff injuries.^[4] Although pain is the most common presenting complaint, it can also present asymptomatically. Another common symptom in rotator cuff injuries is muscle weakness.^[5] Physical examination is mandatory to localize the pain and location of tear. There are two predominant mechanisms of impingement: Extrinsic and intrinsic, proposed by Neer et al. and Codman et al., respectively.^[6] Extrinsic impingement of tendons due to compression by adjacent structures is more common than intrinsic impingement which most commonly occurs due to extreme movements of shoulder joint. Intrinsic factors such as age-related microscopic changes such as fascicular thinning and hypovascularity, and decreased vascularity predisposes to rotator cuff tendinosis and subsequent tear.^[7] Whereas extrinsic sources such as os acromiale, osteophytes, Type III acromion, etc., constitute the extrinsic factors of impingement syndromes.

The aim of this review article is to understand the relevant anatomy of subacromial spaces and review supraspinatus impingement syndrome (SIS) and its association with subacromial distances (SADs). We would also review other causes of extrinsic causes of SIS.

Methodology

The literature search was conducted on PubMed and Google Scholar databases using MeSH terms – “SAD,” “SIS,” “acromion,” and “magnetic resonance imaging (MRI).” Eight studies from 2006 to 2021 have been included for review. Case reports, documentaries, and duplicates were not included in the study.

Inclusion criteria

MRI or conventional radiography-based studies evaluating partial or complete tear of supraspinatus tendon and/or subacromial-subdeltoid bursal effusion
MRI-based studies evaluating subacromial space in rotator cuff injury
Conventional radiograph or MRI-based studies evaluating acromion index
Conventional radiograph or MRI-based studies evaluating lateral angle of acromion.

Exclusion criteria

Computed tomography and ultrasound-based studies of rotator cuff injury
MRI or conventional radiography-based studies evaluating other causes of shoulder pain.

Results

A total of eight MRI or conventional radiograph-based studies done between 2006 and 2021 were considered. A summary of the studies included is given in [Table 1].

Table 1: A summary of similar studies

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Discussion

Anatomy

Subacromial space refers to the space between the lateral aspect of acromion and humeral head. It contains the supraspinatus tendon and subacromial-subdeltoid bursa. Supraspinatus muscle is the superior most rotator cuff muscle arising from the supraspinatus muscle on the dorsal aspect of the scapula inserting into the superior facet of the greater tubercle of the humerus. The coracoacromial arch which comprises the coracoid process, coracohumeral ligament, and acromion from anterior to posterior, helps in stabilizing the tendon. Subacromial-subdeltoid bursa separates the supraspinatus tendon from the coracoacromial arch above. Acromion, the lateral extension of spine of scapula articulates with the lateral end of the clavicle to form acromioclavicular joint. Bigilani et al. described three morphological varieties of acromion: Type I (Flat), Type II (Curved), and Type III (Hooked). A Type IV has also been described recently which is convex downward.^[15]

Imaging of supraspinatus impingement

Conventional radiograph may be used to show bony abnormalities like bony spur that have caused the lesion or bony changes such as sclerosis of the greater tuberosity of the humerus, superior migration of humeral head due to a long-standing pathology.^[16] Standard AP radiographs may reveal osteophytes in the inferior surface of acromion but may not adequately depict anterior acromial pathologies. A caudal angulation of 30° in an AP projection, modified views such as supraspinatus outlet view (modified scapular Y view) and fluoroscopic examination may be used to visualize osteophytes in the undersurface of the anterior acromion. A prospective study done on 100 patients with subacromial bony spur found that only 18% was visualized on the standard AP view compared to the impingement view.^[17]

MRI is a superior imaging modality as it can provide information on the exact extend of tendon tears as well as abnormalities of adjacent structures such as the acromion process and humeral head. MRI can also provide information on atrophy, fatty degeneration, and cross-sectional area of supraspinatus muscle which have implications on the prognosis of tendon repair. Sharma et al. found a sensitivity and specificity of 89.6% and 100% for full-thickness tear and 100% and 86.6% for partial thickness tear, respectively.^[18] On MRI, supraspinatus tendinosis presents with intrasubstance hyperintensity in an enlarged tendon. The hyperintensity within the tendon is less than joint fluid signal intensity. Fluid signal intensity within the tendon suggests tendon tear.

Supraspinatus impingement syndrome

SIS refers to entrapment of the supraspinatus tendon and subacromial bursa within the subacromial space leading to rotator cuff injury and bursitis, respectively. Clinically, the patient presents with shoulder pain on elevating the arm or on lying on the affected side. Age is an important contributing factor as the prevalence of SIS has been found to increase with it.^[19] A number of clinical tests with sensitivity and specificity of 90% and 54%, respectively, are available for diagnosing full-thickness tears clinically.^[20] Impingement of the tendon may be due to intrinsic or extrinsic factors. The concept of the intrinsic mechanism of impingement of supraspinatus tendon due to the degenerative process was described by Codman and Akerson in 1934.^[21] Codman first introduced the concept of “Critical zone” which is identified as a region of decreased vascularity in the supraspinatus tendon 1 cm away from its insertion. The critical zone was proposed to be the most common site of tendinopathy. However, the concept of decreased vascularity as intrinsic factor for rotator cuff tendinopathy was contradicted by several other studies.^[22],[23] Subacromial spurs, Type III acromion and degenerative changes of acromioclavicular joint are some of the extrinsic factors which cause impingement of the tendon. Os acromiale is an important extrinsic cause of SIS which is often overlooked. Os acromiale is an anatomical variant which represents an unfused secondary ossification center of acromion. Its prevalence in the general population is estimated to be 1%–15%.

SIS, in its mildest form can present with subacromial bursitis to tendinosis and in severe cases, as tendon tear. Supraspinatus tendon tear can be broadly classified into two types: partial tear and full-thickness tear. Ellman classification further categories partial thickness tear into three types based on the location of tear, i.e., articular surface or bursal surface and depth of involvement. According to this classification, <3 mm involvement is Grade I, 3–6 mm is Grade II, and >6 mm is Grade III.^[24]

SAD refers to the linear distance between acromion and humerus. A decrease in this distance can lead to impingement of supraspinatus tendon. Normally it ranges from 7 mm to 14 mm. The cutoff below which impingement occurs has been variably described by different authors. Saupe et al. evaluated the association of SAD and SIS in 63 individuals who were divided into three age and sex-matched groups of 21 individuals each. It was found that <7 mm SAD was associated with a full-thickness tear in 90% of patients. Whereas SADs of 8–10 mm and >10 mm was associated with 57% and 38% full-thickness tears. They also found an association between SAD and supraspinatus tendon tears. It was found that the average size of tear decreased with increased SAD. They also found a greater variation in the subacromial space in patients with infraspinatus tendon involvement.^[9] Park et al. evaluated the mean SAD in 80 patients with supraspinatus impingement using MRI and concluded that they had narrower SAD compared to the general population.^[25] However, Park et al. in their systematic review of the relationship between reduced SAD and supraspinatus impingement found no significant correlation between them.^[26] The acromion index is the ratio of linear distance measured from the lateral edge of acromion to the plane of the glenoid cavity to the linear distance measured from the lateral edge of the humeral head to the plane of the glenoid cavity on coronal MR section or AP radiograph of shoulder joint. Miyazaki et al. studied the difference in acromion index in patients with rotator cuff tear and normal patients, and found higher acromion index in rotator cuff injury.^[10] An MRI-based study done by Vijay Kumar et al. evaluated 15 patients with supraspinatus tendon impingement, 15 patients with supraspinatus tendon tear, and 10 normal patients and found significant differences in SAD, acromial index, and lateral acromial angle in these groups. The acromial index was higher and lateral acromial angle (<70°) was lower in patients with impingement syndrome.^[13] A similar study done by Liu et al. compared 91 patients with partial tear of supraspinatus tendon with 91 normal patients and found significantly higher acromion index in patients with tendon tear. No statistically significant differences were found in lateral acromion angle or SAD in these groups.^[14] Mohamed and Abo-Sheisha studied the morphological characteristics of acromion in 56 patients to find their association with rotator cuff tear and found that Type III acromion was associated with full-thickness tear of supraspinatus tendon.^[27] Contradicting the above study, Balke et al. found no association between the type of acromion and supraspinatus impingement, rather proposed that large lateral extension and a low lateral acromial angle (<70°) are associated with impingement syndrome.^[11] Miyazaki et al. evaluated acromial index in 83 (Brazilian population) patients with full-thickness tear using MRI and found the mean AI to be higher (7.2 mm) in patients with rotator cuff tear.^[10] Chalmers et al. have found no association between acromial morphology and supraspinatus tendon tear and its healing.^[28]

Conclusion

Evaluation of SIS can be done reliably using specialized radiographic views and MRI. Extrinsic factors such as reduced SAD and acromion morphology are predisposing factors for impingement of supraspinatus tendon. SAD and lateral acromial angle are lower in patients with supraspinatus impingement compared to the general population. Whereas the acromion index is higher in impingement syndrome.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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