Shoulder Girdle

The Shoulder Girdle is comprised of 3 joints and 2 functional articulations, with only one point of direct contact with the axial skeleton. It’s ball-and-socket construction facilitates maximum range of motion in all three planes of movement making it the most mobile joint in the body (SOURCE-7); however, this is at the expense of its stability. Muscles of the shoulder complex provide the dynamic stability the joints themselves lack. Given many of these muscles receive innervation from the Brachial Plexus and can also cross the neck, the Shoulder Girdle shares a close relationship with the Cervical Spine , particularly in terms of Clinical Examination .

Key Structures

Bone

Muscle

Connective Tissue

Nerve

Fascia

Kinematics

Shoulder kinematics are a complex coordination of joint motion that afford a high degree of mobiity without compromising stability. The Glenohumeral Joint and Scapulothoracic Joint account for the majoirty of this motion through an intricate dance known as the Scapulohumeral Rhythm , while the Sternoclavicular Joint and Acromioclavicular Joint afford smaller contributions which refine and optimise shoulder movement. In terms of muscular contributions, generally the larger superficial muscles such as the Latissimus Dorsi , Deltoid or Pectoralis Major produce movement, while the underlying Rotator Cuff counters their individual translatory biases to maintain a centred Humeral Head and appropriate arthrokinematics (SOURCE-17). The specific kinematics of each movement are listed on their respective page:

Glenohumeral Joint - accounts for the majority of motion at the Shoulder complex (SOURCE-17).

Scapulothoracic Joint

Sternoclavicular Joint - although a relatively small and unstable articulation, the Sternoclavicular Joint represents the primary skeletal connection between the upper limb and axial skeleton (SOURCE-54). All movements of The Shoulder Girdle require movement of the Clavicle at the Sternum , with 3 degress of freedom that correspond with a distinct plane of motion (sagittal, frontal and horizontal) (SOURCE-17+55):

  • Frontal Plane - Elevation and Depression about an anteroposterior axis

  • Horizontal Plane - Protraction and Retraction about a vertical axis

  • Sagittal Plane - Axial Rotation about a longitudinal axis

These motions are detailed further on the Sternoclavicular Joint page, underKinematics.

Acromioclavicular Joint - liberates movement of the Scapula from that of the Clavicle ; however, the extent to which is limited by a small articular surface, dynamic and static stabilisers and, when present, the fibrocartilaginous disc that resides within the joint space. Movement at the Acromioclavicular Joint is reliant on coupled motion at the Scapulothoracic Joint and Sternoclavicular Joint where it permits subtle adjustments to overal motion of The Shoulder Girdle . Three degrees of Scapula movement are described to occur about the lateral Clavicle that are described on its page:

  • Rotation about an anteroposterior axis

  • Rotation about a superoinferior axis

  • Rotation about a laterally extending axis

Pathomechanics

The majority of Shoulder conditions fall on a continuum between a nominal early-phase pathology and a more concerning iteration. In terms of chronicity this is seen when acute Subacromial Impingement festers into chronic Rotator Cuff Tendinopathy ; and in terms of severity when Glenohumeral Instability leads to Glenoid Labrum Tears and recurrent Glenohumeral Dislocation . Many common shoulder pathologies have shared relation to repetitive overhead activities, due to occupational or athletic endeavours (SOURCE-13)

Morphology

The following lists common morphologies that predispose or maintain shoulder pathology:

Recurrence

50% of subjects with shoulder pain had symptoms that persisted three years later (SOURCE-11). Following theories of Central Sensitisation , this chronicity implicates referral from the Cervical Spine due to changes in the Dorsal Horn .

Pathology

The Shoulder Girdle is either related or subject to a plethora of pathologies. Pain is a common symptom, with an estimated 18-26% of adults in the general population experiencing shoulder Pain at least once in their lifetime (SOURCE-2). Often these pathologies occur concomitantly. The following lists common pathologies related to the shoulder girdle, with more specific lists found under the pages of the individual joints or tissues:

Subacromial Impingement - a common shoulder pathology with many causes defined by a narrowing of the Suprahumeral Joint which impacts the traversing Rotator Cuff Tendons and Subacromial Bursa . Impingement is said to account for 36-74% of shoulder pain instances (SOURCE-12)

Rotator Cuff Strain or Tear - said to be one of the most common pathologies of the shoulder with a prevalence of ~22% and asymptomatic tears more common that symptomatic ones (SOURCE-4+5)

Rotator Cuff Tendinopathy - Point and annual prevalence of (2.4% - 21%) and (0.5% - 7.4%), respectively in general population (SOURCE-3)

Subacromial Bursitis - the pathological Subacromial Bursa are recognised as a primary Pain producing tissue of the shoulder (SOURCE-36). This may ensue from direct trauma, repeated overuse or local/ systemic Inflammation which implicates a multitude of shoulder pathologies in the pathogenesis of Bursitis . In turn, the bursal inflammatory milleu narrows the subacromial space, leading to an impingement cascade

Scapular Dyskinesis - an umbrella term for altered motion of the Scapula which is often discribed as a non-specific compensatory response to Pain in the shoulder girdle (SOURCE-37). Dyskinesis often occurs concomitantly with other shoulder pathologies and may be a predisposing factor to their onset. While a lack of standardisation of diagnostic critera makes estimating prevalence difficult, Scapular Dyskinesis is reported to be present in ~60% of symptomatic individuals, ~48% of asymptomatic individuals and potentially higher in those who participate in activities with higher physical demand (SOURCE-38)

Glenohumeral Instability - excessive movement of the Glenohumeral Joint implicates potential insufficiency from many static and dynamic stabilisers of the shoulder girdle and may lead to compensation or compromise at the shoulders other joints. Instability may vary from chronic repetitive Subluxation / instability to acute traumatic Glenohumeral Dislocation . Either form may bestow excessive stress upon soft-tissues such as the Glenoid Labrum or Glenohumeral Capsular Ligaments or osseous structures such as the Glenoid Rim of Scapula or Head of Humerus :

  • Subluxation - could account for as many 85% of all instability events (SOURCE-10)

  • Glenohumeral Dislocation - most common Dislocation , accounting for almost half of the bodies total dislocations (SOURCE-8). Its estimated annual prevalence is estimated to be 0.17% in the general population (SORUCE-8)

Glenoid Labrum Tear - represents an array of labral lesions that may implicate several neighbouring tissues. The majority of these lesions are attributed to chronic Glenohumeral Instability or the traumatic alternative - Glenohumeral Dislocation . Each type of labral tear poses its own set of complications which stem from slight divergences in their mechanism. Often these lesions occur in tandem and/ or along with other concomitant conditions such as Avulsion Fractures of the Head of Humerus or Glenoid Rim of Scapula or tears of neighbouring capsuloligamentous structures such as the Inferior Glenohumeral Ligament or Muscles such as the Long Head of Biceps :

Fracture - there are several Bones of the shoulder girdle that are often compromised by particular types of fractures:

  • Avulsion Fracture - excessive strain bestowed upon the capsulolabroligamentous structures of the shoulder girdle results in soft-tissue compromise or severing of the bony attachment. The shoulders most pertinent examples of this involve a bony disturbance of the Glenoid Rim through Bony Bankart Lesions or Humeral Avulsion of the Glenohumeral Ligaments . Given their shared mechanism, these lesions often occur concomitantly with Glenoid Labrum Tear s

  • Compression Fracture - in the shoulder, compression fractures are most often the result of traumatic Glenohumeral Dislocation in the form of a Hill-Sachs Lesion or its reverse/ posterior equivalent. Given their shared mechanism, these lesions often occur concomitantly with Glenoid Labrum Tear s

  • Clavicle - the most commonly fractured bone in the body, accounting for 44-66% of all Shoulder fractures and 2.6-12% of those body-wide (SOURCE-22+23+24)

  • Scapula / Coracoid Process

  • Proximal Humerus - represent ~ 4% of all fractures that present to an orthopaedic clinic (SOURCE-20), with a reported incidence of 82 per 100,000 person-years (SOURCE-21)

  • Scapula - these fractures are considered rare, accounting for 1% of all fractures and 3-5% of those that affect the Shoulder (SOURCE-25)

Referred Pain Neuropathy - pain may be derived by Entrapment of a Peripheral Nerve or a Radiculopathy of a Nerve Root :

Visceral Referred Pain- shared nerve pathways allow internal organs to refer to the shoulder

  • Diaphragm - often percieved at the tip of the shoulder (~ C3 - C5 distribution) and the result of Inflammation (SOURCE-17)

  • Soft Organ Referred Pain (SOURCE-17):

Adhesive Capsulitis - also known as “Frozen Shoulder”, represents the degenerative fibrotic morphology that follows chronic disease states and periods of immobility/ pain avoidance. The gradual onset of this condition is described in distinct phases. Stage I, the inflammatory stage, is defined by the notable loss in GH Joint - External Rotation and onset of Pain . Stage II, the Freezing stage, usually occurs between 3-9 months and represents acute Synovitis and Glenohumeral Joint Capsule Contracture formation. Stage III, the Frozen stage, occurs between 9-15 months and marked by a complete loss of the Axillary Pouch and contracture formation which leads to stiffness/ restriction. The final Stage IV, the Thawing stage, represents mature contracture formation and notable loss of motion in absense of Pain . Adhesive Capsulitis is often reported to have an incidence of 2-5% in the general population; however, this number may be inflated (SOURCE-6)

Dislocation - the three true joints of the Shoulder Girdle may be subject to dislocation

  • Glenohumeral Dislocation - discussed above

  • Acromioclavicular Joint - the extent of injury and number of soft-tissues implicated is generally correlated with the significance of force bestowed upon the shoulder. Acromioclavicular Joint dislocations has an overall incidence of 3-4 per 100,000 persons in the general population with 25-50% occuring during sporting activities (SOURCE-43)

  • Sternoclavicular Joint - account for <3% of all injury to the Shoulder Girdle (SOURCE-27)

Muscle Tear or Tendinopathy - while significantly less common than the Rotator Cuff , the following muscles are known subjects of tissue lesion:

Osteoarthritis

  • Glenohumeral Joint - is reported to be present in ~5-15% of complainants shoulders and believed to be the underlying cause of shoulder Pain in 2-5% of cases (SOURCE-45+46). The prevalence appears to be population specific with Glenohumeral Osteoarthritis reported to be present in the vast majority (~94%) of women over the age of 80 (SOURCE-47).

  • Acromioclavicular Joint - degenerative changes such as a loss of intra-articular disc and protective Cartilage may lead to Pain ful Bone -on- Bone contact, making age a major risk factor (SOURCE-44). Osteoarthritis may also be a long term consequence of traumatic injury which serves as a catalyst to the accumulation of micro-trauma and Inflammation (SOURCE-44)

Deep Vein Thrombosis of the Upper Extremity (DVT-UE) - the formation of a blood clot can occur through primary and secondary means to occlude the deep veins of the arm, notably the Axillary Vein and Subclavian Vein (SOURCE-52+53):

  • Primary DVT-UE - also known asPaget-Schroetter Syndrome, accounts for the minority (~20%) of DVT-UE and more often affects young, healthy individuals as the underlying mechanism is effot-induced. Repeitive, exhaustive movements of the upper limb leads to mechanical compression of the Thoracic Outlet (equivalent to Venous Thoracic Outlet Syndrome ). This pathological compression in physiologic movement is often attributed to anatomical variation, including Cervical Spine Ribs , Clavicle Fracture and hypertrophy of the Scalenes .

  • Secondary DVT-UE - accounts for the majoirty (~80%) of DVT-UE instances and most often the result of a combination of the following factors, with or without anatomical variants:

    • Irritation of the vessel walls - the most common source of DVT-UE is Central Venous Catheters, Peripherally Inserted Central Catheter or a Pacemaker lead that causes local endothelial injury and initiating the thrombotic cascade

    • Chemotherapeutics

    • Tumour-related Hypercoaguability

Clinical signs for DVT-UE inclues sudden-onset arm swelling, Pain , heaviness and occasionally cyanosis (SOURCE-53).

Assessment

As the Shoulder Girdle represents a major portion of the body with many components, this section provides an overview of the approaches taken to assessment. For assessment protocols tailored to a specific pathology, see its respective page. With a high prevalence of concomitant pathologies, it is often difficult to determine which symptoms are compensatory and causative (SOURCE-13). This clinical challenge necessitates a rigorous and holistic shoulder investigation. Each assessment modality is arranged in a descending step-by-step manner, although this is subject to change:

Subjective History

A patients subjective histroy should be gathered to gain adequate perspective of the circumstances surrounding the patients pathology which directs and refines physical assessment. For the Shoulder Girdle a major component of this is establishing a precise mechanism of injury (SOURCE-49):

The nature of the patients Pain may also be revealing. Night pain is common for Adhesive Capsulitis or Rotator Cuff pathology, while numbness or the sensation of pins and needles may indicate a neuropathy (SOURCE-49). The feeling of a “dead-arm” may indicate a Glenohumeral Dislocation or Subluxation where the Axillary Nerve is compromised which often occurs concomitantly with Glenoid Labrum Tear (SOURCE-49). A patients age may also increase or decrease the likelihood of certain shoulder pathologies (SOURCE-8+47+49+50+51):

  • Rotator Cuff - both acute/ traumatic and chronic/ degenerative pathologies of the cuff become increasingly prevalent with age. Rotator Cuff Tears usually occur between the ages of 30-50 while degenerative conditions ususally occur between the ages of 40 to 60

  • Subacromial Impingement - primary impingement is usually seen in those over the age of 40 while secondary impingement is typically seen in younger populations between the age of ~15-35

  • Adhesive Capsulitis - more common in those between the ages of 40-70

  • Osteoarthritis - usually occurs in those beyond the age of 50 and may be present in the majority of the elder population and is often asymptomatic

  • Atraumatic Glenohumeral Instability - usually occurs between the ages of 10 and 35

  • Glenohumeral Dislocation - prevalence is highest for males between 21-30 and females 61-80

  • Cervical Spine Spondylosis - usually occurs over the age of 50

Observation

Observation of the Shoulder Girdle is typically done from an anterior, posterior and lateral view with the patient standing (SOURCE-18+48):

  • Anterior View - Sternum should be centred with Ribs symmetrical. Similarly, the Sternoclavicular Joint and Acromioclavicular Joint on each side should appear symmetrical. Unilateral or anterior translation of the shoulder is often apparent. Excessive shoulder rotation (often internal) may be noted through position of The Hands or The Elbow s

  • Lateral View - in the sagittal plane the following structures should be aligned; Ears , the shoulder girdle, midpoint of the trunk, Greater Trochanter of Femur , slightly anterior of midline of The Knee and Lateral Malleolus of Fibula . Only about 1/3rd of the Head of Humerus should extend anteriorly of the Acromion of Scapula , additional anterior translation would be considered excessive. The Medial Border of Scapula should have ~9º of anterior tilt

  • Posterior View - the neck to shoulder line should be symmetrical between sides. Acromion should appear horizontal and the Medial Borders of Scapula parallel with eachother and only a few cm from the Vertebral Column . T2 roughly aligns with the Scapulas Superior Angle, T3 with its Spine and T7 with the Inferior Angle.

Range of Motion

Range of Motion of the Shoulder Girdle occurs as a composite of motion at all of its joints/ articulations, as described in Scapulohumeral Rhythm . To quickly rule in/out the shoulder as a source of Pain , the Shoulder Quick Screen may be performed. For a more thorough investigation all major shoulder motions should be performed actively, passively and then against resistance. Combined, repetitive and sustained motions may also be of relevance. Thorough investigation should also extend to associated structures including the Cervical Spine , Thoracic Spine and proximal Ribs . Findings should be compared to the asymptomatic side as a point of reference. Shoulder - Active Range of Motion - typically perfomed first as the patient demonstrates their voluntary range which indicates their functional capacity and severity of symptoms.

Shoulder - Passive Range of Motion - passive assessment usually proceeds active to compare any potential differences in ranges between the two. If passive range of motion exceeds active range of motion, dynamic contributors (such as muscle weakness, poor coordination or nerve involvement) are implicated in pathology. Conversely, when active and passive range are equally restricted, a capsular or bony restriction is implicated.

Isometric Tests - the same active shoulder motions can be performed against the resistance of the pracitioner to isolate Muscle Strength and reveal any deficits or localise symptoms of Pain .

Orthopaedic Tests

An extensive list of Orthopaedic tests and the pathologies they are indicated for may be found on the Shoulder - Special Tests page.

Neurological Tests

The following Neurodynamic Tests may be conducted to evaluate the involvement of neural structues such as Nerve Roots and Peripheral Nerves in Pain or restriction: Upper Limb Nerve Tension Tests - the Brachial Plexus which forms the Peripheral Nerves of the arm encounters several potentially compressive points on its course through the Shoulder Girdle:

Dermatomes - altered sensation in a particular region (skin) implicates the Nerve Root that innervates that region:

Myotomes - if not already assessed as part of the isometric testing

Imaging

As imaging findings alone do not consistently correlate with a patients symptoms and findings are often identified in asymptomatic shoulders, they should be complimented by physical examination before reaching a diagnosis and establishing a treatment protocol (SOURCE-30).

Radiography (X-Ray)- often the first line of imaging for shoulder pathologies such as suspected Fractures of the Head of Humerus (SOURCE-35). Additionally useful for visualising Dislocation s, degenerative changes (space narrowing or bone spurs) and calcification. As superimposed structures may impede ability to distinguish osseous structures, particular views are recommended for individual structures which are detailed on their respective pages. Unlike many of the other imaging techniques, X-rays are limited in their ability to visualise soft-tissues.

Ultrasonography (Ultrasound)- a highly accessible imaging modaility with real-time capabilities for the evaluation of soft-tissues including the Subacromial Bursa , Rotator Cuff and their Tendons . A major limitation of this modaility is that it is highly operator dependent.

Magnetic Resonance Imaging (MRI)- with the capacity for Bone and Soft-Tissue to be implicated in shoulder pathology, MRIs may be preferable due to their ability to produce clear images of both. High sensitivity for the detection of edema also allows MRIs to recognise pathologies in their early phase (SOURCE-19).

  • Proton Density Weighted Images (PD)- localise bone and soft-tissue pathology at the same time. The high water content in inflamed tissue causes this tissue to appear white (SOURCE-19)

Computed Tomography (CT) Scan- akin to MR-arthrography, used most often for the evaluation of Cartilage or the Glenoid Labrum (SOURCE-30). Typically reserved as a complement to other imaging modalities for the assessment of bony changes or when MRI’s are contraindicated (SOURCE-30). CT-Scans also have value for fracture classification and preoperative planning, particularly when a shear component is present (SOURCE-31+32)

Dual X-Ray Absorptiometry (DEXA)- is considered the gold-standard for the evaluation of Bone Mineral Density which serves a marker for Osteoporosis (SOURCE-33+34)

Treatment

There are many treatment modalities available to the shoulder that ultimately aim to restore appropriate tone to soft tissues, correct joint arthrokinematics or address underlying Pain and Inflammation . The approach often depends on the pathology, severity and chronicity of the condition with options ranging from conservative management like physiotherapy and pharmacological interventions to more invasive options such as injections or surgical repair. The overarching goal is to restore optimal shoulder function, alleviate discomfort and prevent recurrence to enable individuals to return to their daily activities and physical performance.

Stretching

The following lists Stretching techniques may be relevant to the Shoulder that aim to either restore length of associated soft-tissues or correct overall biomechanics, with lists of targeted stretches for each Muscle on its respective page (seeKey Structuresabove):Simple:

Intermediate:

Advanced:

Strengthening

Strength training forms an integral role of shoulder (p)rehabilitation and enables individuals to improve function/ capacity. Resistance movements for the shoulder not only improve strength but neuromuscular control which coordinates quality motion at the numerous shoulder articulations. While many listed exercises may be progressed through load or time under tension, the following details shoulder movements in rough order of most rudimentary to sophisticated.

Initial Phase - typically used in the early phases of (p)rehabilitation to mitigate Muscle atrophy, provoke activity and cue appropriate joint motion:

Mid-Phase - simple strength exercises that may be relevant once Pain -free motion is achieved:

Late Phase - exercises at this stage should more closely reflect the activities/ demands of the patient. Relevant functional patterns should be promoted and exercises should be progressed in complexity and intensity:

Mobilisation

Through promoting appropriate joint arthrokinematics Mobilisations have been shown to be an effective treatment modality for many shoulder pathologies, often improving dysfunctional markers such as Pain , Range of Motion and Strength or functional deficits.

Joint Play - passive accessory movements performed without active movement

Mobilisation with Movement - mobilisations applied with active movement

Dry Needling

The following tissues have Dry Needling procedures detailed on their respective pages:

Surgery

Surgical intervention for the Shoulder Girdle is typically reserved for when conservative measures fail to meet desired outcomes. These interventions often seek to restore stability, decompress structures or repair damaged tissue which may be associated with Pain or dysfunction. While specific procedures for joints or pathologies may be discussed on their individual pages, the following general procedures are avaliable: Glenohumeral Joint - see Humerus page for more detail

  • Open Reduction and Internal Fixation (ORIF) - an incision is made through the overlying skin and soft-tissue to reveal the fracture site. The bone fragments are then repositioned (reduced) and then fixed with metal plates, screws or nails

  • Shoulder Reconstruction - a prosthetic replaces either the Humeral Head alone (Hemiarthroplasty) or additionally the Glenoid Fossa (Reverse Total Shoulder Arthroplasty)

  • Intramedullary Nailing (IMN)- A permanent rod or “Nail” is inserted into the centre of the Bone

  • Closed Reduction and Percutaneous Pinning (CRPP)- the Humeral fragments are fixed using pins which are then later removed

Acromioclavicular Joint

  • Coracoclavicular (CC) Screw Fixation - one of the oldest techniques that involves open reduction of the Acromioclavicular Joint and insertion of a screw from the Distal Clavicle into the Coracoid Process of Scapula

  • Hook Plate Fixation - a plate is fixed to the superior surface of the Clavicle with a hook that engages the inferior surface of the Acromion which affords a stable reduction

  • Endobutton Coracoclavicular Fixation - a modern and typically arthroscopic approach which utilises a synthetic suture-button system to restore the native Coracoclavicular Ligament s

  • Ligament Reconstruction with Biological Grafts - autografts and allografts used to anatomically reconstruct the Coracoclavicular Ligament and Acromioclavicular Ligaments

Suprahumeral Joint

  • Subacromial Decompression - decompresses the Subacromial space through the removal of bony spurs and inflammatory tissue such as the Subacromial Bursa to widen the space for traversing Tendon s

Other

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