Shoulder Joint and Pectoral Girdle

Glenoid labrum

-A fibrocartilagnious ring attached to the margin of the glenoid cavity -serves primarily to DEEPEN the glenohumeral joint -also widens the glenoid cavity and IMPROVES CONGRUITY of the glenohumeral joint -the peripheral surface of the labrum is attached to the joint capsule. -the superior portion of the labrum blends with the biceps tendon. -narrow rim of fibrocartilage around the edge of the glenoid cavity that slightly deepens and enlarges the glenoid cavity.

superior glenohumeral ligament (SGHL)

-Anterior glenohumeral ligament that arises from the glenoid rim from approximately 1:00 and runs inferior and laterally. -Inserts on the anatomical neck near the medial ridge of the intertubercular groove, anterior to the greater tuberosity. -tightens on lateral rotation of humerus and anterior glide of head. -This ligament is most engaged (stretched) for external rotation when arm is by side. When you abduct you are bringing it closer to its attachment, so not as engaged. -So must engaged at 0 deg abduction.

Convex-Concave Rule

-Convex surface = humerus -Concave surface = glenoid fossa -When a convex surface moves on a stable concave surface, the glide of the convex surface is in the OPPOSITE direction of the bony lever. Convex moving on concave: roll and glide are in OPPOSITE direction. If the moving joint surface is CONVEX, sliding is in the OPPOSITE direction of the angular movement of the bone. -When a concave surface moves on a stable convex surface the glide of the concave surface is in the SAME direction as the movement of the bony lever. Concave moving on convex: roll and glide are in same direction. If the moving joint surface is CONCAVE, sliding is in the SAME direction as the angular movement of the bone. -The roll is always in the same direction as the angular movement (movement of bone); the direction of the glide depends on whether it is convex moving on concave or concave moving on convex.

Movements of the shoulder

-Flexion: 150-180 degrees -Extension: 50-60 degrees -Abduction: 180 degrees -External rotation: 90 degrees -Internal rotation: 70-90 degrees -Horizontal Abduction -Horizontal Adduction

Glenohumeral motion

-Glenohumeral motion is controlled by: (1) Passive restraints (static stabilizers): ---Bony geometry (ball and socket joint) ---Glenoid labrum ---Capsuloligamentous structures (reinforce joint capsule, offer stability) ---Negative intra-articular pressure (2) Active restraints ---The rotator cuffs: if the tissue is on the posterior side, it will check internal rotation. If on the anterior side, it will check external rotation. *Passive are the ligaments and the capsule, active is the musculature that is present

Sternoclavicular joint

-Joint formed between the clavicular notch of the manubrium and the sternal (medial) end of the clavicle. -Saddle synovial joint-shape. Plane gliding b/c it doesn't have its own motion. -Movements: gliding, with limited movements in nearly every direction. -Motion of sternoclavicular joint: can occur during elevation/depression of shoulder, protraction/retraction of shoulder, rotation of scapula (3 degrees of freedom) -Joint capsule--capsule is strong but still depends on ligaments for stability -Anterior and posterior sternoclavicular ligaments: cover the anterior and posterior areas of the articulation and connect the manubrium to the clavicle.--they check anterior/posterior motion of head of clavicle(prevent anterior and posterior glide of clavicle) -Interclavicular ligament connects the two clavicles to each other and to the superior end of the manubrium. Extends across the jugular notch of the sternum. Checks excessive depression or downward glide of the clavicle. -The costocavicular ligament joins the first costal cartilage (first rib) to the undersurface of the sternal end of the clavicle. This is a very strong ligament that provides substantial stability. Main check to clavicular elevation and superior glide (prevents superior displacement of clavicle). This is also the axis for elevation and depression -Intra-articular disc separates the incongruent joint surfaces, and is continuous with the anterior/posterior SC ligaments.

acromioclavicular joint

-Joint formed by articulation of acromion of the scapula and acromial end of clavicle. -Plane synovial joint with 3 degrees of freedom -Movements: as part of shoulder girdle; cannot produce movements in isolation. -Movements: axial rotation of clavicle (spin) and rotation of the clavicle around a longitudinal axis ----Occurs during elevation above 60 degrees, scapula upwardly rotates and conoid trapezoid ligaments restrict motion. Coracoid process of the scapula now pulls downward and tugs on the coracoclavicular ligaments...this results in a flip of the clavicle around the longitudinal axis. This is referred to frequently with scapulohumeral rhythm. -Primary function of this joint is to maintain the relationship between the clavicle and scapula during the early stages of elevation--elevation of the upper extremity is a combination of scapular, clavicular, and humeral motion. -AC joint has a joint capsule and 2 major ligaments: acromioclaviculr ligaments and coracoclavicular ligaments. -AC joint contains an intra-articular disc--varies in size; usually degenerates by age 40.

Coracoclavicular ligaments

-Ligaments of the AC joint that run from the coracoid process of the scapula to the clavicle -Conoid ligament (medial) -Trapezoid ligament (lateral) -These ligaments are very strong-frequently the elbow will break before these ligaments rupture. -These ligaments PREVENT SUPERIOR DISLOCATION OF ACROMION ON CLAVICLE-prevents the clavicle from losing contact with the acromion. -most critical role = PRODUCING LONGITUDINAL ROTATION of clavicle necessary for full range of motion of upper extremity. -These ligaments participate in scapulohumeral rhythm. -As scapula rotates upward, clavicle elevates -The coracoclavicular ligament causes posterior spinning of clavicle in response to GH motion--as scapula rotates outward and upward, the coracoclavicular ligaments, which are attached to the inferior surface of the clavicle, stretches and pulls on the clavicle, causing clavicle to spin posteriorly (about longitudinal axis)-(upward rotation of clavicle) -When the arm is elevated through abduction, the rotation of the scapula causes the coracoid process to move and increases the distance between the clavicle and the coracoid process. This movement also increases the tension on the conoid ligament, causing a backward axial rotation of the clavicle. As scapular angulation occurs, the coracoid process is pulled downward and away from the clavicle. The taut coracoclavicular ligament then acts on the outer curvatrue of the clavicle and effects a rotation of the clavicle on its long axis. This clavicular rotation permits the glenoid fossa to continue to elevate and increase the possible degree of arm elevation.

Acromioclavicular ligaments

-Ligaments that connect the clavicle and the scapula. -The acromioclavicular ligament is subdivided into two parts: the superior acromioclavicular ligament covers the superior part of the articulation and extends between the acromial end of the clavicle and the adjoining part of the upper surface of the acromion of the scapula. -the inferior acromioclavicular ligament covers the inferior part of the articulation and is attached to the adjoining surfaces of the clavicle and scapula. -The superior AC ligament is the strongest. -Strengthens the articular capsule of the AC joint, and prevents the AC joint from separating. -The AC joint capsule is weak and needs ligaments to reinforce it--the superior and inferior AC ligaments CONTROL HORIZONTAL (anterior-posterior) STABILITY (prevents posterior and anterior displacement)

Capsuloligamentous structures (of glenohumeral joint)

-Medially, the capsule is attached to the periphery of the glenoid and the glenoid labrum -Laterally, the capsule is attached to the anatomical neck of the humerus -Superiorly, the capsule encroaches on the coracoid process, enclosing the origin of the long head -Inferior margin of the capsule may form a collar-like attachment along the anatomical neck. -Anteriorly, the glenohumeral joint is reinforced by three bands or thickenings of the capsule -Anterior glenohumeral ligaments: superior glenohumeral ligament (SGHL), middle glenohumeral ligament (MGHL), inferior glenohumeral ligament (IGHL), coracohumeral ligament (CH). -Glenohumeral ligaments form a Z on the anterior side of the capusle and sometimes only exist as capsular thickenings...all portions TIGHTEN ON LATERAL ROTATION of the humerus and anterior glide of the head.

Flexion-Extension

-Occurs about an axis that is perpendicular to the glenoid cavity (sagittal) -As a result, flexion occurs in an anteriomedial direction and extension in a posterolateral direction.

Abduction-Adduction

-Occurs about an axis that lies parallel to the glenoid cavity -Axis runs anteriomedially to posteriomedially -As a result, abduction-adduction occurs in a plane anterior to the frontal plane -Abduction of the glenohumeral joint requires external rotation to allow the greater tuberosity to pass under the coracoacromial notch.

Axillary Nerve C5, C6

-Terminal branch of the posterior cord -3 posterior divisions -supplies the GH joint, teres minor, and the deltoid -Gives rise to the superior lateral brachial cutaneous, then winds around the surgical neck deep to the deltoid. -The superior lateral brachial cutaneous nerve supplies the skin of the posteriolateral arm.

Scapulothoracic joint

-The articulation between the scapula and the posterolateral corner of the thorax. -Note: this is not a true anatomical joint due to the lack of fibrocartilaginous union-it is actually an articulation between the scapula and the thoracic cage. -Scapula is suspended on the thorax by the scapulothoracic muscles -Consists of two spaces: a) the space between the serratus anterior and the scapula/subscapularis b) space between the serratus anterior and the thoracic wall. -The thorax and scapula are separated by the subscapularis and serratus anterior muscles, which glide over each other during movements of the scapula. -Resting position of scapula: the medial border is nearly vertical; abducted approx 6cm from the spine; anterior tilt of 20 degrees -Hand of dominance: depressed, downward rotated, anteriorly tilted. -Scapular motions: downward/upward rotation of scapula, elevation/depression, abduction (protraction)/adduction (retraction). -Upward and downward rotation: scapula swings laterally and medially in the frontal plane. -Scapulothoracic motion: a) Elevation/depression-cephelad or caudal b) protraction/retraction - sliding toward or away from the vertebral column (abduction/adduction) c) Rotation-tilt the fossa up or down.

Glenohumeral joint

-The articulation of the glenoid surface of the scapula with the head of the humerus -Classified as a spheroidal (BALL AND SOCKET) joint -multiaxial and has three degrees of freedom -sacrificing stability for mobility -The glenoid fossa is positioned laterally, antheriorly, and slightly superior. It is concave in anterior/posterior and inferior/superior directions. -The humeral head is 1/3 of a sphere and thus is not matched to the concavity of the glenoid...this results in an increased arc of motion, but decreased congruity of joint surfaces. However, the labrum increases this congruity. -The head of the humerus is the CONVEX joint surface, and is approx 1/3 of a sphere. The head faces medially, posteriorly, and superiorly. -The anatomical neck of the humerus separates the humeral head from the remainder of the epiphysis. -The axis through the humeral head and the longitudinal axis may form an angle anywhere between 130-150 degrees in the FRONTAL plane...this is referred to as the angle of inclination. -In the TRANSVERSE plane, the axis through the humeral head and the condyles create the angle of torsion. -The anatomical neck of the humerus serves as the site of attachment for the glenohumeral joint capsule. Lateral to the anatomical neck are the greater and lesser tubercles. -The glenoid fossa forms the concave surface of the glenohumeral joint.

Humerus

-The greater tubercle of the humerus serves as the site of attachment for the supraspinatus, infraspinatus, and teres minor. The greater tuberosity has 3 facets, which those muscles attach to (supraspinatous-superior facet; infraspinatous-middle facet but comes from posterior; teres minor-inferior facet, but comes form posterior). -The lesser tubercle is the site of attachment for the subscapularis muscle. -The tubercles are separated by the intertubercular tube, which the tendon of the long head of the biceps brachii passes through. -The surgical neck is the region below the greater and lesser tubercles (where the upper margin of the humerus joins the shaft). -The axillary nerve and the posterior humeral circumflex artery lie in close proximity to the medial aspect of the neck. They pass posterior through the quadrangular space (the posterior humeral circumflex artery and axillary nerve travel from anterior side into the quandrangular space, coming out posteriorly, and then they supply posterior structures). When the neck is fractured, can result in a disruption of the axillary nerve distribution--deltoid atrophy.

Orientation of the scapula

-The scapula does not lie in the frontal plane, it is angled obliquely 30 degrees in the frontal plane ("Scapular plane" is 30-45 degrees anterior to the frontal plane).

Shoulder Girdle

-The shoulder girdle (pectoral girdle) consists of the lateral ends of the clavicle and scapula, along with the proximal end of the humerus, and the muscles covering these three bones to stabilize the shoulder joint. -The girdle creates a base from which the head of the humerus, in its ball and socket joint with the glenoid fossa of the scapula, can move the arm in multiple directions. -Consists of the glenohumeral joint (scapula and humerus), acromioclavicular joint (scapula and clavicle), sternoclavicular joint (clavicle and manubrium), scapularthoracic joint (scapula and thoracic cage), and subacromial space.

Articular capsule of glenohumeral joint

-Thin, loose sac that completely envelops the joint and extends from the glenoid cavity to the anatomical neck of the humerus. -Anatomical neck = site of attachment for the joint capsule. -Capsule is twice the size of the humeral head -Capsule is weakest inferiorly, but the weakness is most apparent in the anterior direction since forces are more likely to thrust the humeral head forward. Inferior portion is protected from above by the arch. -Not many ligaments reinforcing hte inferior region; and no ligament reinforcement on the posterior side--Capsule is most likely to dislocate inferiorly or posteriorly. -Attached medially to the glenoid cavity (beyond the labrum), laterally to the anatomical neck of the humerus, and superiorly to the coracoid process (enclosing the long head of the biceps within the capsule). -Synovial membrane lines the fibrous capsule. -Inferior portion of the capsule is loose and redundant with the arm at the side of the body--this becomes tight and stretched out at the end of the range of elevation. More specifically, ABDUCTION tightens the capsule. -The inferior portion of the capsule is referred to as the axillary pouch. -The posterior capsule is very thin. -Anteriorly, the glenohumeral joint is reinforced by three bands or thickenings of the capsule.

coracohumeral ligament

-an superior glenohumeral ligament that arises from the lateral end of the coracoid process and runs laterally splitting into two bands -the anterior band blends with the subscapularis tendon to insert near the lesser tubercle. -Posterior band blends with the supraspinatus tendon to insert near the greater tubercle -Strong, broad ligament that strengthens the superior part of the articular capsule and extends from the coracoid process of the scapula to the greater tubercle of the humerus -The ligament strengthens the superior part of the articular capsule, and reinforces the anterior aspect of the articular capsule. -checks external rotation but is more important as a passive support to the limb against gravity. -Checks any kind of motion with arm at 0 deg abduction (arm by side)

middle glenohumeral ligament (MGHL)

-anterior glenohumeral ligament that arises from the glenoid rim from approximately 1:00-3:00 and runs inferiorly and laterally. -Inserts on the anatomical neck medial to the lesser tuberosity -tightens on lateral rotation of humerus and anterior glide of head. -This ligament is most engaged at 45 degrees abduction. It checks external rotation at 45 degrees abduction.

inferior glenohumeral ligament (IGHL)

-anterior glenohumeral ligament that arises from the inferior 2/3 of the glenoid rim and runs laterally -From approximately 3:00-8:00 -Inserts along the inferior 1/3 of the head of the humerus -tightens on lateral rotation of humerus and anterior glide of head. -IGHL complex: -anterior band: a thickening which arises between 2 and 4 o'clock. -Posterior band: a thickening which arises from the glenoid rim between 7 and 9 o'clock. -Axillary pouch: inferior support -inserts on the humerus below the lesser tuberosity. -During 90 degrees of abduction, the inferior glenohumeral ligament is most engaged (stretched). -When externally rotating (while the anterior band of this ligament is engaged. -When internally rotating (while at 90 deg abduction) the posterior band of this ligament is engaged.

medial/lateral rotation

-bring arm in = medial rotation -bring arm out = lateral rotation

Glenoid fossa

-forms the concave surface of the glenohumeral joint -much smaller than the head of the humerus -laterally, superiorly, and anteriorly. For the fossa to face in this direction, not the scapula does not lie in true frontal plane at rest (lies in scapular plane) -The curvature of the fossa is greater in the frontal plane than in the sagittal plane. -Majority of the time the humeral head only rests on a small inferior portion of the fossa -The supraglenoid tubercle serves as a site of attachment for the long head of the biceps

Scapulohumeral rhythm

-scapulohumeral rhythm = the coordinated movement of the scapulae across the thoracic cage called scapula thoracic movement together with the movement of the humerus on the glenoid, or glenohumeral movement (Scapulothoracic movement + glenohumeral movement) -correct scapulohumeral rhythm is required to achieve full upper limb elevation. -Scapular superior rotation upon the thorax tilts the glenoid fossa upwards. This change in its orientation accentuates the movement occurring at the glenohumeral joint. This coordinated movement occurs in a predictable fashion and any disturbance to this pattern is evidence of a muscular or joint dysfunction. -Generally, in the first 30 degrees of shoulder abduction the scapula remains stationary against the ribcage with the movement occurring only at the glenohumeral joint. -As shoulder abduction continues the inferior angle of the scapula begins to shift outwards as it undergoes superior rotation. -On average, there is approximately two degrees of glenohumeral movement for every 1 degree of scapulothoracic movement. This means that as the upper extremity moves on through abduction - 90 degrees in the glenohumeral joint contributes to 40 degrees for a total of 70 while the scapulothoracic has only contributed 20 degrees. This ratio continues above 90 degrees so that by the time the arm has been raised to 150 degrees the contributions of each joint would be 110 for the glenohumeral and 40 for the scapulothoracic. -The actual ratio can vary during different portions of the arch of elevation and can be different from individual to individual--therefore, its always important to compare the involved side with the uninvolved side. -Muscles primarily responsible for the scapulothoracic stability and motion: serratus anterior, rhomboids, levator scapulae, and trapezius. Pectoralis minor and subclavius are also scapulothoracic muscles. -Scapula contributes to both flexion and shoulder abduction by upwardly rotating the glenoid fossa 60 degrees. The arm can move through only 30 deg of abduction and 45-60 deg of flexion with minimal scapular movements. Past these points, the scapular movements occur with the arm movements. Functions of scapulohumeral rhythm: -Maintains joint congruity -Large range of motion with increasing stability -Maintains good length-tension relationships between muscles.

Quadrangular space

-superior border = teres minor -inferior border = teres major -medial border = long head of triceps -lateral border = coracobrachialis, surgical neck. -axillary nerve (C5, C6) and posterior humeral circumflex artery pass through this space from the anterior to the posterior, and supply structures on the posterior side (deltoid and teres minor muscles; innervates the skin on the lateral shoulder and back of the arm).

Subacromial space

As the arm abducts to 90 deg, the greater tuberosity makes contact with the acromion process. If the arm is externally rotated, 30 deg more abduction can occur as the greater tuberosity is moved out from under the arch. -Clinical relevance: -Primary impingement: structural stenosis of subacromial space -secondary impingement: functional stenosis of subacromial space due to abnormal arthrokinematics. -Avoidance of impingement during elevation of the arm requires: external rotation of humerus to clear greater tuberosity, and upward rotation of scapula to elevate lateral end of acromion.

infraspinatus

Muscle of the shoulder region -O: infraspinous fossa of scapula and deep fascia -I: middle facet of greater tubercle of humerus -A: lateral rotation of arm -N: suprascapular nerve

subscapularis

Muscle of the shoulder region -O: subscapular fossa -I: lesser tubercle of the humerus -A: medially rotation of arm at shoulder, adduction -N: upper and lower subscapular nerves

Supraspinatus

Muscle of the shoulder region -O: supraspinous fossa of scapula and deep fascia -I: superior facet of greater tubercle of humerus -A: arm abduction (acts with rotator cuff muscles) -N: suprascapular nerve

Teres minor

Muscle of the shoulder region -O: upper 2/3 of posterior surface of lateral border of scapula -I: inferior facet of greater tubercle of humerus -A: Lateral rotation of arm -N: axillary nerve

Scapulothoracic motion

Scapulothoracic motion that occurs during scapulohumeral rhythm involves the AC joint and the SC joint. -Scapular rotation is necessary to: enhance glenohumeral stability, elevate acromion to avoid impingement, and maintain effective length-tension relationship of scapulohumeral muscles.

interclavicular ligament

connects the two clavicles to each other and to the superior end of the manubrium. Extends across the jugular notch of the sternum. Checks excessive depression or downward glide of the clavicle.

Anterior and posterior sternoclavicular ligaments

cover the anterior and posterior areas of the articulation and connect the manubrium to the clavicle.--they check anterior/posterior motion of head (prevents anterior/posterior glide of clavicle) -During protraction, posterior ligament becomes taut -During retraction, anterior ligament becomes taut. -These ligaments pass inferiorly and medially from the sternal end of the clavicle to the anterior and posterior surfaces of the manubrium.

costoclavicular ligament

joins the first costal cartilage (first rib) to the undersurface of the sternal end of the clavicle. This is a very strong ligament that provides substantial stability. Main check to clavicular elevation and superior glide (prevents superior displacement of clavicle head) -Becomes taut when the arm is elevated -Axis for elevation/depression is this ligament.