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This is the clinical evidence summary written for health professionals. It is technical, and it lists the research this page was built from. You do not need to read it to understand your treatment or to make a decision about it.

Anatomy & Pathophysiology

Bony Anatomy

• The proximal humerus comprises four main parts: the humeral head, greater tuberosity, lesser tuberosity, and humeral shaft [3].
• The articular head of the humerus is spherical with a diameter of 37 to 57 mm [3].
• The most superior portion of the articular surface of the humeral head averages 8 mm above the greater tuberosity [3].
• Humeral version averages 29.8 degrees, with a range of 10 to 55 degrees [3].
• The humeral head is inclined approximately 130 degrees with respect to the humeral shaft [3].
• The neck-shaft angle measures an average of 135 degrees [4].
• The humeral head is retroverted an average of 30 degrees [4].
• The glenoid is a convex structure of shallow depth shaped like an inverted pear [3].
• The glenoid cavity is a shallow socket, approximately one third the size of the humeral head [4].
• The subchondral bone of the glenoid is relatively flat, with the articular concavity augmented by cartilage and a circumferential labrum [6].
• The glenoid averages 5° of retroversion in relation to the axis of the scapular body [6].
• The acromion, coracoacromial ligament, and coracoid process form the coracoacromial arch, a rigid bony-ligamentous structure that imparts stability to the shoulder girdle [3].
• The scapula is attached to the axial skeleton by the acromioclavicular and sternoclavicular joints [5].
• The scapula is separated from the chest wall by thin gliding fibro-fatty tissue, allowing its smooth excursion over the chest wall [5].
• The lateral pillar connects the inferior border of the glenoid with the inferior angle of the scapula [5].
• The spinal pillar arises from the central part of the glenoid and continues medially to become part of the base of the scapular spine [5].
• The two bony pillars connected by a markedly thinner medial border form the basic load-bearing structure of the scapular body, known as the biomechanical body of the scapula [5].
• The weakest bone in the scapula is located primarily in the central part of the biomechanical body, specifically in the infraspinous fossa [5].
• The weakest area of the circumference of the biomechanical body of the scapula is the spinomedial angle, which is the connection of the scapular spine and the medial border of the scapula [5].

Soft Tissue Anatomy

• The greater tuberosity serves as the attachment site for the supraspinatus, infraspinatus, and teres minor tendons of the rotator cuff [3].
• The lesser tuberosity serves as the attachment site for the subscapularis tendon [3].
• The bicipital groove lies between the greater and lesser tuberosities and serves as a pathway for the long head of the biceps [3].
• The rotator cuff consists of four muscles: the subscapularis, supraspinatus, infraspinatus, and teres minor [4].
• The infraspinatus and teres minor are external rotators, while the subscapularis is an internal rotator of the humerus [4].
• The rotator cuff muscles serve as depressors of the humeral head to allow the deltoid to efficiently abduct the humerus [4].
• The subscapular bursa lies between the subscapularis tendon and the neck of the scapula and communicates with the joint cavity between the superior and middle glenohumeral ligaments [7].
• The rotator interval is defined medially by the base of the coracoid, superiorly by the supraspinatus tendon, and inferiorly by the subscapularis tendon [6].
• The rotator interval contains the coracohumeral ligament, the superior glenohumeral ligament, and the intra-articular portion of the long head of the biceps tendon [6].
• The coracohumeral ligament restricts external rotation in adduction and is a static restraint to inferior and posterior translation in adduction and external rotation [6].
• The superior glenohumeral ligament is a primary static restraint against anterior translation with the arm at the side [6].
• The middle glenohumeral ligament is a primary static restraint against anterior translation with the arm in external rotation and 45° of abduction [6].
• The anterior band of the inferior glenohumeral ligament is a primary static restraint against anterior-inferior dislocation of the glenohumeral joint in 90° of abduction and external rotation [6].
• The posterior band of the inferior glenohumeral ligament is a primary static restraint against posterior-inferior translation in internal rotation and adduction [6].
• The glenoid labrum provides concavity and up to 50% of marginal glenoid socket depth [6].

Vascular Anatomy

• The proximal humerus receives its blood supply from the anterior and posterior humeral circumflex branches from the third division of the axillary artery [3].
• The anterior humeral circumflex artery provides vascular inflow to the humeral head by way of its terminal anterolateral branch known as the artery of Laing, also known as the arcuate artery [3].
• The ascending branch of the anterior humeral circumflex artery courses parallel to the lateral aspect of the long head biceps tendon and enters the humeral head at the interface of the bicipital groove and greater tuberosity [3].
• The anterolateral ascending branch of the anterior humeral circumflex artery provides the primary blood supply to the humeral head [6].
• Injury to the arcuate artery may result in osteonecrosis of the humeral head [3].
• Additional extraosseous collateral branches can permit humeral head perfusion despite complete ligation of the arcuate artery [3].

Pathophysiology of Frozen Shoulder

• Frozen shoulder, also known as adhesive capsulitis, is characterized by pain and restricted glenohumeral joint motion, especially external rotation [15].
• The essential lesion in frozen shoulder involves the coracohumeral ligament and the rotator interval capsule [15].
• Histologically, frozen shoulder shows evidence of inflammation and fibrosis with a dense matrix of type III collagen containing fibroblasts and myofibroblasts [15].
• The histological findings in frozen shoulder appear similar to findings in Dupuytren disease [15].
• Laxity of the rotator interval results in inferior laxity, while contracture of the interval is seen with adhesive capsulitis [6].
• Posttraumatic or postsurgical stiffness results from excessive scar formation [15].
• Motion loss in posttraumatic or postsurgical stiffness may involve the humeroscapular motion interface between the proximal humerus and overlying deltoid and conjoined tendon, as well as contracture of the rotator cuff and capsule [15].
• The pathogenesis of a stiff shoulder is still elusive, though ongoing basic science research has provided insight into cellular and biochemical pathways resulting in shoulder stiffness [1].

Investigations

General Principles

• The diagnosis of a stiff shoulder depends on awareness of the problem, with history and physical examination being paramount [1].
• Ancillary studies may be helpful in certain circumstances for the diagnosis of a stiff shoulder [1].
• The purpose of imaging the shoulder is to help establish the diagnosis, determine the severity of the pathoanatomy, assist in surgical planning, and enable the surgeon to illustrate the condition to the patient [2].
• Unless a specific research protocol is in place, the temptation to "overimage" should be resisted by obtaining only the scans or reconstructions necessary for patient care [2].
• Proper radiographic technique is as important as proper surgical technique to achieve the desired outcome [2].
• A robust approach to imaging the shoulder must recognize that the shoulder is a three-dimensional structure that cannot be represented by a single planar view [13].
• Critical relationships, such as the degree of centering of the humeral head, change with the position of the arm [13].
• Shoulder pathology may be found in a large number of different bones and soft tissues [13].
• Overlying and superimposed structures as well as metallic implants may complicate imaging the structures of interest [13].
• Surgeons need to develop a judicious approach to imaging that yields necessary information while avoiding the tendency to "over-image" [13].

Radiographic Evaluation

• Standardized plain films are almost always sufficient to garner the information needed for shoulder care [2].
• CT scans may offer a few degrees of increased precision in the measurement of glenoid version, but this precision does not improve the quality of the surgery or the clinical outcome [2].
• There is information that can be gathered from properly taken plain films that cannot be obtained from CT scans [2].
• The first key radiographic view is the anteroposterior (AP) view in the plane of the scapula taken so that the x-ray beam passes through the glenohumeral joint [2].
• The AP view in the plane of the scapula shows the superoinferior position of the humeral head relative to the glenoid [2].
• The AP view in the plane of the scapula shows the presence of osteophytes on the humeral head and glenoid [2].
• The AP view in the plane of the scapula shows narrowing of the joint space [2].
• The AP view in the plane of the scapula shows the degree of medial displacement of the humerus in relation to the lateral acromial line [2].
• The AP view in the plane of the scapula shows the quality of the humeral and glenoid bone [2].
• The AP view in the plane of the scapula shows the presence of loose bodies [2].
• The AP view in the plane of the scapula shows whether there is humeral head collapse or deformity [2].
• The second key radiographic view is the axillary view taken with the arm in the functional position of elevation in the plane of the scapula [2].
• The axillary view is oriented so that both the spinoglenoid notch and the scapular neck are visible [2].
• The axillary view shows a different perspective of the humeral anatomy [2].
• The axillary view shows the amount of glenoid bone [2].
• The axillary view shows the shape of the glenoid [2].
• The axillary view shows the version of the glenoid in relation to the plane of the scapula [2].
• The axillary view shows the relationship of the humeral head to the glenoid fossa [2].
• The standardized axillary view is referred to as the "truth view" because it demonstrates glenohumeral relationships in the functional position of elevation [2].
• CT scans have the disadvantage of being taken with the arm in the adducted position [2].
• Many "axillary views" sent for consultation are taken without standardization, making it impossible to determine important features of the glenohumeral joint [2].
• When taken properly, standardized anteroposterior and axillary views indicate the thickness of the cartilage space between the humerus and the glenoid [2].
• When taken properly, standardized anteroposterior and axillary views indicate relative positions of the humeral head and the glenoid [2].
• When taken properly, standardized anteroposterior and axillary views indicate the presence of osteophytes [2].
• When taken properly, standardized anteroposterior and axillary views indicate the degree of osteopenia [2].
• When taken properly, standardized anteroposterior and axillary views indicate the extent of bony deformity and erosion [2].
• Joint space narrowing is most evident on the axillary truth view as opposed to images made with the arm at the side [2].
• The axillary truth view can show posterior subluxation or "functional decentering" that is not evident in images taken with the arm at the side [2].
• The degree of posterior subluxation can be measured as the position of the center of the humeral head in relation to the plane of the scapula [2].
• The degree of posterior subluxation can be measured as the position of the center of the humeral head in relation to the glenoid face [2].
• The degree of posterior subluxation can be measured as the point of contact of the humeral articular surface on the glenoid articular surface [2].
• The point of contact of the humeral articular surface on the glenoid articular surface reflects the degree of centering of the net humeral joint reaction force on the glenoid [2].
• Malcentering of the joint reaction force leads to posterior instability, posterior glenoid wear, and "rocking horse" loosening of prosthetic glenoid components [2].
• At least two X-ray views should be obtained: an anteroposterior in the plane of the glenoid and an axillary projection with the arm in abduction [11].
• The axillary projection with the arm in abduction shows the relationship of the humeral head to the glenoid [11].

Magnetic Resonance Imaging

• Magnetic resonance imaging (MRI) is useful to identify osteonecrosis of the humeral head [11].
• Magnetic resonance imaging (MRI) is useful to identify a bone tumour [11].
• Magnetic resonance imaging (MRI) can identify labral tears [11].
• Magnetic resonance imaging (MRI) can identify rotator cuff tears [11].
• The accuracy of MRI for identifying labral tears and rotator cuff tears is enhanced by combining the scan with arthrography [11].
• Findings of adhesive capsulitis and an intact labrum on magnetic resonance arthrography were independent predictors for pain relief after glenohumeral corticosteroid injections [14].

Computed Tomography

• Computed tomography (CT) is helpful for planning fracture surgery [11].
• Computed tomography (CT) is helpful for planning shoulder joint replacement [11].

Ultrasonography

• Ultrasonography is a simple and accurate test for identifying rotator cuff tears [11].
• Ultrasonography is a simple and accurate test for identifying calcific tendinitis [11].
• Ultrasonography can be useful in guiding injections [11].
• Ultrasonography can be useful in guiding barbotage, which involves aspirating calcific deposits in the rotator cuff [11].
• The most commonly performed joint examination using ultrasonography is the shoulder examination [9].
• The accuracy of shoulder ultrasonography depends on the skill of the scanner operator and an awareness of pitfalls that are encountered [9].

References

[1] Rockwood And Matsen S The Shoulder. Arthroscopic Management of Prearthritic and Arthritic Conditions of the Shoulder and the Postarthroplasty Shoulder > SUMMARY.

[2] Rockwood And Matsen S The Shoulder. Arthroscopic Management of Prearthritic and Arthritic Conditions of the Shoulder and the Postarthroplasty Shoulder > Radiographic Evaluation.

[3] Rockwood And Matsen S The Shoulder. Shoulder and Elbow Specialty Clinic Workers’ Survey > ANATOMY.

[4] A Lange Medical Book Current Diagnosis Treatment In Orthopedics Fifth Edition. 2Musculoskeletal Trauma Surgery > SHOULDER AND ARM INJURIES.

[5] Rockwood And Green S Fractures In Adults. 29: Principles of Nonunion and Bone Defect Treatment > Applied Anatomy Related to Scapular Fractures.

[6] Aaos Comprehensive Orthopaedic Review 3. Anatomy of the Shoulder, Arm, and Elbow > I. Shoulder.

[7] Rockwood And Matsen S The Shoulder. Developmental Anatomy of the Shoulder and Anatomy of the Glenohumeral Joint > Bursae.

[9] Orthopaedic Knowledge Update Sports Medicine 6. Diagnostic Ultrasonography and Ultrasonography-­Guided Procedures > Annotated References.

[11] Apley And Solomon S Concise System Of Orthopaedics And Trauma. INVESTIGATION.

[13] Rockwood And Matsen S The Shoulder. Developmental Anatomy of the Shoulder and Anatomy of the Glenohumeral Joint > SENIOR EDITOR COMMENTARY.

[14] Orthopaedic Knowledge Update Sports Medicine 6. Magnetic Resonance Imaging of the Glenohumeral Joint > Annotated References.

[15] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > SHOULDER STIFFNESS > 1. A stiff shoulder may be posttraumatic, postsurgical, or the result of adhesive capsulitis.