BMS Anatomy Lecture 10 Scapulocostal, Sternoclavicular, Acromioclavicular, and Shoulder Joints (Fall 2023) PDF

BMS Anatomy Lecture 10 Scapulocostal, Sternoclavicular, Acromioclavicular, and Shoulder Joints (In-Person Class) Presented By: Dr. K. Lumsden; [email protected] (Toronto Campus) Dr. M. Doroudi; [email protected] Boucher Campus) Moore's Clinically Oriented Anatomy, by Arthur F. Dalley II Ph.D. FAAA (...

BMS Anatomy Lecture 10 Scapulocostal, Sternoclavicular, Acromioclavicular, and Shoulder Joints (In-Person Class) Presented By: Dr. K. Lumsden; [email protected] (Toronto Campus) Dr. M. Doroudi; [email protected] Boucher Campus) Moore's Clinically Oriented Anatomy, by Arthur F. Dalley II Ph.D. FAAA (Author), Anne M. R. Agur BSc (OT) MSc Ph.D. FAAA (Author), 9th ed. Upper Limb Chapter; Pages: 268 – 277 Scapulothoracic Joint A physiological joint (no true articulation) Scapula with Thoracic cage Movements of this joint is provided by the muscles attached to scapula Dependent on acromioclavicular and sternoclavicular articulations Any movement at the scapulothoracic joint will result in movement at both of these joints Scapulothoracic Joint Role Provides a movable base for the Humerus, hence increasing arm ROM at shoulder joint Helps deltoid function with proper tension with arm above 90 Provides Glenohumeral stability for overhead work Absorbs shocks to outstretched arms Scapulothoracic Joint 1. Protraction – abduction away from midline (spine) 2. Retraction – adduction towards midline (spine) 3. Elevation (upward sliding on ribcage) 4. Depression (downward sliding on ribcage) 5. Rotation of scapula (reference is glenoid cavity and inferior angle) 1. 2. Upward rotation – glenoid rotates superiorly, inferior angle rotates away from midline Downward rotation – glenoid rotates inferiorly, inferior angle rotates towards midline ✓ Displacement of the inferior angle is 10 – 12 Cm. and that of the lateral angle is 5 – 6 Cm. Sternoclavicular Joint The Articular Surfaces Include: Facet on the lateral end of the clavicle (aka acromial facet) Facet on the medial end of the acromion Type of Joint: Plane synovial joint Movement: Slide and glide 5 Sternoclavicular Joint Supportive ligaments (3): 1 2 3 6 SC Joint Movements 1 2 3 4 5 Movement Elevation of Clavicle Depression of Clavicle Protraction Retraction Rotation of Clavicle Degrees 60 5 - 10 25 – 30 25 – 30 30 7 Acromioclavicular joint (A/C Joint) The Articular Surfaces Include: Facet on the lateral end of the clavicle (aka acromial facet) Facet on the medial end of the acromion Type of Joint: Plane synovial joint Movement: Slide and glide Note: AC joint moves as a result of scapular movement Acromioclavicular joint (A/C Joint) Ligaments: Acromioclavicular Ligament: A strong fibrous band that reinforces the superior aspect of the acromioclavicular joint Trapezoid Ligament: Extends from the coracoid process of the scapula to the trapezoid line on the inferior lateral end of the clavicle Conoid Ligament: Extends from the base of the coracoid process of the scapula to the conoid tubercle on the inferior aspect of the lateral clavicle The trapezoid and the conoid ligaments make up the Coracoclavicular Ligament, which anchors the lateral end of the clavicle and prevents superior dislocation of the AC joint Glenohumeral (Shoulder) Joint Articular Surfaces: The glenoid fossa of the scapula and the head of the humerus The articular surfaces are covered by hyaline cartilage Type of Joint: Ball and socket synovial joint (multi-axial – 3 degrees of freedom 10 Physiology of the Shoulder (Glenohumeral Joint) 1. 2. 3. The shoulder, the proximal joint of the upper limb, is the most mobile of all the joints in the human body. It has 3 DOF and this allows it to move the upper limb with respect to the three planes in space. Medial – lateral axis, controls the movement of flexion and extension. Antero-posterior axis, controls the movements of abduction and adduction. Vertical axis, controls the rotational movements. 11 Glenohumeral (Shoulder) Joint The head of the humerus is much larger than the glenoid cavity, only approximately 1/3 of the head of the humerus fits into the glenoid fossa Glenoid Labrum is a ring of fibrocartilage attached to the margins of the glenoid cavity. It widens the cavity slightly but deepens it appreciably so as to make the articular surfaces congruent. 13 Capsule of the Glenohumeral (Shoulder) Joint ❖ Attaches to the margins of the glenoid cavity medially and to the anatomical neck of the humerus laterally. ❖ It is covered from inside by the synovial membrane. 14 Glenohumeral (Shoulder) Joint Ligaments  The capsular ligaments: The joint capsule is very loose and permits free movements. It is least supported inferiorly where dislocation commonly occurs. Such a dislocation may damage the closely related axillary nerve. Anteriorly the joint capsule is reinforced by 3 supplemental bands, called the superior, middle and inferior glenohumeral ligaments. 15 Transverse Humeral Ligament Bridges the upper part of the bicipital groove of the humerus (between the greater and lesser tubercles), converts the intertubercular groove into a canal, and functions as a ‘retinaculum’ for the tendon of the long head of the biceps brachii, holding the synovial sheath and tendon in place during glenohumeral movements. 16 Coracohumeral Ligament From the coracoid process of the scapula to the greater tubercle of the humerus. Intrinsic Ligament. Coracoacromial Arch An extrinsic, protective structure formed by the smooth inferior aspect of the acromion and coracoid processes of the scapula, and the coracoacromial ligament bridging the gap between them. This arch overlies the head of the humerus, preventing its superior displacement from the glenoid cavity. 18 Position of the Rotator Cuff Muscles Tendon Around the Joint Capsule 19 Position of the long head of biceps inside the Shoulder Joint 20 Bursae around the shoulder Joint There are several bursae around the shoulder joint such as the subscapular bursa (Overlies the anterior joint capsule and lies beneath the subscapularis muscle). These bursae serve to decrease friction between the tendon and/or muscle and joint capsule.  The subacromial bursa: Is between the acromion and the tendon of the supraspinatus muscle. It facilitates movements of the supraspinatus tendon under the coracoacromial arch and of the deltoid over the fibrous capsule and greater tubercle of the humerus. It is subject to impingement beneath the acromial arch if it is inflamed and swollen.  Subdeltoid bursa: Is between the deltoid and the fibrous capsule. It may be continuous with the subacromial bursa. 21 Flexion, Extension, and Hyperextension of the shoulder joint Flexion and extension (1): performed in a sagittal plane, about a transverse axis. (a) Extension: 45° to 50°. (b) Flexion to 180° 22 Flexion, Extension, and Hyperextension of the shoulder joint Adduction (2): adduction in the frontal plane starting from the position of reference is mechanically impossible owing to the presence of the trunk. Starting from the position of reference, adduction is only possible when combined with: (a) Extension, which allows a bit of adduction. (b) Flexion, in this case adduction can reach 30° to 45° 23 Abduction of the shoulder joint Abduction (3): the movement of the upper limb away from the midline, takes place in a frontal plane, about an antero-posterior axis. When abduction reaches 180° the arm is vertically above the trunk. Two points must be noted : 1. After the 90° position, the movement of abduction brings the upper limb once more closer to the sagittal plane of the body. 2. The final position of abduction at 180° can also be achieved by flexion to 180°. 24 Scapulohumeral Rhythm 25 Rotation of the shoulder joint This occurs about the longitudinal axis of the humerus. (a) Position of reference: in order to measure the range of movements of rotation the elbow must be bent at 90°, the forearm thus lying in a sagittal plane. WHY? (b) Lateral rotation: to 80° (c) Medial rotation: to 95° For medial rotation to reach this far, the forearm must be pulled behind the trunk, and this introduces a certain degree of extension. 26 Transverse Movements of the shoulder joint Horizontal movements: these take place about a vertical axis and involve not only the shoulder joint but also the scapula. Their total range falls short of 180°. (a) Position of reference: 90° ABD. of shoulder joint in the frontal plane. Muscles involved are: (b) Horizontal adduction: range 140°. Muscles involved: Ant. deltoid, subscapularis, pectoralis major, pectoralis minor, serratus anterior, coracobrachialis, and short H. of biceps. (c) Horizontal abduction : range 30°. Muscles involved: Post. deltoid, infraspinatus, teres major, teres minor, rhomboid muscles, trapezius, latissimus dorsi. 27 Muscles of the Shoulder Girdle 28 MAIN MUSCLE ACTIONS ON THE SHOULDER JOINT