Indian Journal of Rheumatology

REVIEW ARTICLE
Year
: 2018  |  Volume : 13  |  Issue : 5  |  Page : 17--21

Regional sonology of the upper limb - I: Shoulder


Ankit B Shah1, Bipin R Shah2,  
1 Department of Radiology, Eclat Polyclinic, Mumbai, Maharashtra, India
2 Department of Imaging, Gray Scale Imaging, Vile Parle (West), Mumbai, Maharashtra, India

Correspondence Address:
Dr. Ankit B Shah
102, Kusumkunj, 10th Road, Khar (West), Mumbai - 400 052, Maharashtra
India

Abstract

Knowledge of the anatomy of the shoulder and its periarticular soft tissues and scanning techniques are essential for successful ultrasound (US) examination of the shoulder. Inflammatory conditions or overuse injuries affecting the periarticular structures are the most common causes of nontraumatic shoulder pain. Dynamic imaging with US is an added advantage and scores over similar cross-sectional imaging modalities. In a routine US examination of the shoulder joint, the extraarticular segment of the long head of biceps, rotator-cuff tendons and their muscle bellies, rotator interval, subacromial-subdeltoid bursa, posterior joint recess, and the acromioclavicular joint are assessed systematically.



How to cite this article:
Shah AB, Shah BR. Regional sonology of the upper limb - I: Shoulder.Indian J Rheumatol 2018;13:17-21


How to cite this URL:
Shah AB, Shah BR. Regional sonology of the upper limb - I: Shoulder. Indian J Rheumatol [serial online] 2018 [cited 2022 May 19 ];13:17-21
Available from: https://www.indianjrheumatol.com/text.asp?2018/13/5/17/238197


Full Text



 Introduction



The relatively superficial location of the periarticular structures around the shoulder joint allows their evaluation with ultrasonography. Inflammatory conditions or overuse injuries affecting the periarticular structures are the most common causes of nontraumatic shoulder pain. Ultrasound (US) has a high spatial resolution of the periarticular soft tissues. Dynamic imaging with the US is an added advantage and scores over similar cross-sectional imaging modalities.

Knowledge and concepts of the anatomy of the shoulder and its periarticular soft-tissues aids in successful US examination of the shoulder. Discussion of the US anatomy of the shoulder would include (1) long head of biceps (LHBT), (2) Rotator-cuff, (3) rotator interval (RI), (4) subacromial-subdeltoid (SASD) bursa, (5) posterior joint recess, and (6) acromioclavicular (AC) joint.

 Long Head of Biceps Tendon



The LHBT tendon has intraarticular and extraarticular segments. It takes its origin from the supraglenoid tubercle and traverses horizontally in the glenohumeral joint space [Figure 1]. It exits the glenohumeral joint at the rotator-cuff interval (focal space between the subscapularis and the supraspinatus [SS] tendons). The extraarticular LHBT angulates inferiorly as it exits the RI. The extraarticular LHBT is located within the bicipital groove of the humerus which is formed by the lesser tuberosity (LT) medially and the greater tuberosity (GT) laterally. The extraarticular LHBT is surrounded by a synovial sheath known as the biceps tendon sheath (BTS). The BTS communicates with the joint cavity. The LHBT is held firmly in the bicipital groove by the coracohumeral and the transverse humeral ligaments (HLs). The transverse HL covers the proximal bicipital groove.{Figure 1}

US of the shoulder begins by identifying the extraarticular LHBT from the anterior aspect. The LT and GT are the osseous landmarks used to identify the location of the LHBT by placing the probe transversely on the humerus. The LHBT is seen in the short axis as an oval hyperechoic structure within the bicipital groove [Figure 2]. The presence of a small amount of fluid within the BTS is seen as a hypoechoic halo around the hyperechoic tendon. The transverse HL is seen as a hyperechoic band covering the LHBT in the proximal bicipital grove. Inferiorly, the LHBT is scanned until the attachment of the pectoralis major tendon.{Figure 2}

Turning the probe by 90 degrees, the LHBT is seen as a fibrillary hyperechoic cord-like structure situated between echogenic humeral cortex and the deltoid muscle belly [Figure 3].{Figure 3}

 Rotator-Cuff



The rotator-cuff is a short, flat, and broad musculotendinous structure formed by close interdigitation of the fibers of four tendons.[1] From anterior to posterior direction, the tendons forming the rotator-cuff include subscapularis, SS, infraspinatus, (IS), and the teres minor tendons.

Subscapularis

The subscapularis is a multipennate muscle taking its origin from the anterior surface of the scapula. It attaches to the LT [Figure 4]. The subscapularis tendon has a broad footprint measuring approximately 39.5 mm in the craniocaudal direction.[2]{Figure 4}

The subscapularis tendon is evaluated from the anterior aspect in the short and long axis after asking the patient to externally rotate the shoulder so that the maximum extent of the tendon is visualized after it slides outward below the coracoid process.

The tendon is seen as an echogenic fibrillar structure in the long axis as it attaches to the LT [Figure 5]. In the short axis, the subscapularis tendon is seen to have intermittent hypoechoic linear echoes [Figure 6] due to the multipennate nature of the tendon where the muscle tissue is interposed between the tendon fascicles.[3]{Figure 5}{Figure 6}

Supraspinatus

The SS muscle takes its origin from the supraspinous fossa along the posterior surface of the scapula. The tendon passes through a tunnel-like area formed by the coracoacromial arch (acromion, the AC joint, and the coracoid process) above and the glenohumeral joint below [Figure 4]. The tendon inserts into the upper facet of the GT with a relatively broad footprint.

The tendon is examined in the long and short axis using various maneuvers. The more commonly used position is known as the modified crass position, where the tendon is examined from the anterior aspect by asking the patient to extend the shoulder with the elbow flexed at 90° and the palm facing anteriorly. The palm is made to touch the ipsilateral hip.[4]

The SS tendon is seen as a thick, echogenic “beak-shaped” structure with fibrillar echoes and having a convex superficial margin [Figure 7]. The tendon is visualized just below the lateral margin of the acromion as it inserts over the GT. The SS tendon has a relatively broad footprint on the GT. The tendon measures 6.4 mm (±1.4 mm) in medial to the lateral direction at the site of insertion.[3] On the short axis, measuring from the anterior margin of the rotator-cuff interval, the SS tendon measures 1.8 cm–2 cm in the anteroposterior direction [Figure 8]. The posterior fibers of the SS tendon closely interdigitate with the anterior fibers of the IS tendon; hence, the posterior limit is not well delineated on imaging – this region is referred to as the conjoint tendon.{Figure 7}{Figure 8}

Infraspinatus and teres minor

The IS arises from the infraspinous fossa of the scapula and attaches on the GT, just posterior to the attachment of the SS tendon. The teres minor muscle originates from the lateral margin of the scapula and attaches to the inferior facet of the GT.

The IS and the teres minor tendons are evaluated from the posterior aspect. The tendons are evaluated in the long and short axis after asking the patient to touch his finger to the opposite shoulder across the chest. This maneuver allows the maximum length of the tendons to be visualized. Identification of the scapular spine in the short axis (sagittal section) allows identification of the infraspinous fossa, which lies inferior to the spine.[5] Scanning the area from lateral to medial aspect shows the two echogenic tendons as separate tendons arising from the muscle bellies. The tendons are seen as well-defined echogenic structures with fibrillary pattern [Figure 9].{Figure 9}

 Rotator Interval



The RI is the space between the superior margin of the subscapularis tendon and the anterior margin of the SS tendon [Figure 10]. The boundaries of the RI are formed by the fusion of the fibers of the joint capsule, subscapularis tendon, and the SS tendon. The contents of the RI include the LHBT, coraco-HL, and the superior gleno-HL.{Figure 10}

It is evaluated from the anterior aspect using the modified crass maneuver as described above [Figure 11].{Figure 11}

 Subacromial-Subdeltoid Bursa



Although many bursae have been described around the shoulder, the subacromial-subdeltoid (SASD) bursa is the most clinically significant one. The SASD bursa lies deep to the deltoid muscle and the AC joint [Figure 12]. Laterally, it extends beyond the rotator-cuff insertion and curves around the GT. There is no communication of the SASD bursa with the glenohumeral joint.{Figure 12}

Normally, the SASD bursa is visualized as an echogenic stripe [Figure 7] due to the peribursal fat, not more than 2 mm in thickness.[6] When inflamed, the SASD bursa is seen as a hypoechoic structure situated between the deltoid muscle and the rotator-cuff tendon.

 Posterior Joint Recess



The posterior joint recess is evaluated from the posterior aspect. Maintaining the arm in the neutral position, the probe is placed transversely across the joint line and scanning is performed in the craniocaudal direction. The axillary pouch is seen below the level of the humeral head. The posterior labrum is seen as an echogenic triangular structure [Figure 13].{Figure 13}

 Acromioclavicular Joint



The (AC) joint may be evaluated either from the anterior aspect or the posterior aspect. After, palpating the AC joint, the probe is placed horizontally over it. If the AC joint is not palpable, the lateral margin of the acromion is identified, and the probe is slid medially till the joint is reached.

The normal AC joint has smooth articular cortical margins. The AC joint capsule is seen as a hypoechoic convex structure overlying the joint cavity [Figure 14].{Figure 14}

 Conclusion



US is an excellent modality to evaluate the various pathologies involving the periarticular soft tissues of the shoulder joint. The key periarticular structures include the rotator cuff, SASD bursa, extraarticular LHBT tendon, and the RI and the AC joint. Thorough knowledge of the complex anatomy of the shoulder joint and familiarity with the normal US appearance of the various periarticular structures aids in performing a successful US examination and increases the confidence of the individual performing the examination.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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