The triangular-shaped scapula has three angles: inferior, superior, and lateral (Figure 5-5). The longitudinal axis is indicated by the dashed green line. The very cooperative nature of shoulder muscles increases the versatility, control, and range of active movements. The large and rounded greater tubercle has an upper, middle, and lower facet, marking the distal attachment of the supraspinatus, infraspinatus, and teres minor, respectively (see Figure 5-7, B and Figure 5-9). ACL, anterior capsular ligament; CCL, costoclavicular ligament; PCL, posterior capsular ligaments. These crests receive the distal attachments of the pectoralis major and teres major (see Figure 5-7, A). Extension is a movement that increases the angle between the two parts that the joint is connecting. The interclavicular ligament spans the jugular notch, connecting the medial end of the right and left clavicles. To allow so much movement the joints need to be 'free' to move, therefore the shoulder should be 'unstable' compared to other joints of the body; However a series of complex ligaments and muscle keep it in joint. Little movement occurs at this joint, with the movements being reflected in scapular elevation, abduction (protraction), and rotation. The remaining outer edge of the disc attaches to the internal surface of the capsule. Common conditions affecting range of motion, Pendulum and Codman Exercises for Shoulder Rehabilitation. A normal range of motion for shoulder flexion is 180 degrees. • The shoulder complex includes the articulations of the humerus, the clavicle, the scapula, and the posterior surface of the ribs. This absorption mechanism apparently works well because significant age-related degenerative arthritis is relatively rare at this joint.35, The tremendous stability at the SC joint is due to the arrangement of the periarticular connective tissues and, to a lesser extent, the interlocking of the articular surfaces. Keep your elbows against your body and move your forearms towards your body. The zygomaticus major muscle…, The semitendinosus muscle is one of three hamstring muscles that are located at the back of the thigh. This article have been viewed 30080 times, Periarticular Connective Tissue and Other Supporting Structures, Scapulothoracic Posture and its Effect on Static Stability, Overall Kinematics of Shoulder Abduction: Establishing the Six Kinematic Principles of the Shoulder Complex, Sternoclavicular and Acromioclavicular Joints during Full Abduction, Innervation of the Muscles and Joints of the Shoulder Complex, Muscles That Elevate the Arm at the Glenohumeral Joint, Upward Rotators at the Scapulothoracic Joint, Function of the Rotator Cuff Muscles during Elevation of the Arm, Muscles That Adduct and Extend the Shoulder, Muscles That Internally and Externally Rotate the Shoulder. until the 15 minute clock stops. The stretched costoclavicular ligament helps limit as well as stabilize the elevated position of the clavicle. The costal facets, located on the lateral edge of the manubrium, provide bilateral attachment sites for the first two ribs. This series of joints provides extensive range of motion to the upper extremity, thereby increasing the ability to reach and manipulate objects. Up to this point, we have discussed the arthrology and kinematics of each joint of the shoulder complex. The SC joint is the only bony attachment site of the upper extremity to the axial skeleton. Primary movements at the scapulothoracic joint are traditionally described as elevation and depression, protraction and retraction, and upward and downward rotation. Joint surfaces vary, however, from flat to slightly convex or concave (see, The AC joint is surrounded by a capsule that is directly reinforced by. In addition, skin The arthrokinematics for elevation and depression of the clavicle occur along the SC joint’s longitudinal diameter (see Figure 5-12). costoclavicular Buy Membership for Rheumatology Category to continue reading. C. The manubrium possesses a pair of oval-shaped clavicular facets, which articulate with the clavicles. The depth of the supraspinatous fossa is filled by the supraspinatus muscle. Anterior view of a mechanical diagram of the arthrokinematics of roll and slide during elevation (A) and depression (B) of the clavicle around the right sternoclavicular joint. Superior and inferior acromioclavicular joint ligaments. The acromioclavicular (AC) joint is the articulation between the lateral end of the clavicle and the acromion of the scapula (Figure 5-16, A). Proximal attachments of muscle are shown in red. The clavicle, through its attachment to the sternum, functions as a mechanical strut, or prop, holding the scapula at a relatively constant distance from the trunk. FIGURE 5-2. This places your hands above your head with your arms straight. The triangular-shaped scapula has three angles: The posterior surface of the scapula is separated into a, The scapula articulates with the head of the humerus at the slightly concave, Located at the superior and inferior rim of the glenoid fossa are the. Imagine your body is a cabinet, your arms are the cabinet doors and you’re shutting the doors. Protraction and Retraction: Protraction and retraction of the clavicle occur nearly parallel to the horizontal plane, around a vertical axis of rotation (see Figure 5-13). The costoclavicular ligament is a strong structure extending from the cartilage of the first rib to the costal tuberosity on the inferior surface of the clavicle. Extension - Movement of the arm through the … This extensive ligament consists of two parts: the trapezoid and conoid ligaments. Axial (Longitudinal) Rotation of the Clavicle: The third degree of freedom at the SC joint is a rotation of the clavicle around the bone’s longitudinal axis (see Figure 5-13). Then 2 back squats, 2 shoulder presses, 2 deadlifts. Depression—From an elevated position, the scapula slides inferiorly on the thorax. Find out why it is sometimes accompanied by pain while other times it's not, as…, Few would suspect the cause of shoulder pain to be something as typical and inactive as sitting at our desks. The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. Much of the stability in the shoulder complex is provided by this muscular coordination. The right clavicle and acromion have been removed to expose the top of the right glenohumeral joint. • Angles: inferior, superior, and lateral, • Supraglenoid and infraglenoid tubercles. The muscles in the shoulder aid in a wide range of movement and help protect and maintain the main shoulder joint, known as the glenohumeral joint. ... Movement of the shoulder would be limited to 30 degrees of shoulder flex/abd. The shoulder’s main motions are flexion, extension, abduction, adduction, internal rotation, and external rotation. STUDY. Maximums of approximately 45 degrees of elevation and 10 degrees of depression have been reported.27,140 Elevation and depression of the clavicle produce a similar path of movement of the scapula.73. Large forces through the clavicle often cause fracture of the bone before the SC joint dislocates. The right acromioclavicular joint. The rounded and prominent medial or sternal end of the clavicle articulates with the sternum (see Figure 5-3). The mechanics of this interesting motion are further described later in this section on shoulder kinematics. The GH joint is of parti… Excessive tightness in the posterior bundle of the costoclavicular ligament, the posterior capsular ligament, and the scapular retractor muscles limit the extremes of clavicular protraction. This gives the shoulder complex a huge range of motion and makes it a very versatile joint. 2. Clavicular fractures are most common in males under 30 years old—most often as the result of contact-sport or road-traffic accidents.164, The osteokinematics of the clavicle involve a rotation in all three degrees of freedom. The study of the upper extremity begins with the shoulder complex, a set of four articulations involving the sternum, clavicle, ribs, scapula, and humerus (Figure 5-1). An articular disc of varying form is present in most AC joints. The right clavicle and acromion have been removed to expose the top of the right glenohumeral joint. This motion occurs as a natural component of lowering the arm down to the side. (The axis of rotation is shown in Figure 5-13 as intersecting the sternum because, by convention, the axis of rotation for a given motion intersects the convex member of the joint.) The right side shows the first seven ribs and clavicle. The primary purpose of these movements is to place the scapula in an optimal position to accept the head of the humerus. Near the superior rim of the glenoid fossa is the prominent coracoid process, meaning “the shape of a crow’s beak.” The coracoid process projects sharply from the scapula, providing multiple attachments for ligaments and muscles (Figure 5-6). C, Upward and downward rotation. The acromion extends in a lateral and anterior direction, forming a horizontal shelf over the glenoid fossa. Shoulder adduction occurs when you move your arms towards the middle of the body. Angle B: The orientation of the scapula (scapular plane) deviated about 35 degrees anterior to the frontal plane. The vertical axis of rotation is shown through the sternum. The tremendous stability at the SC joint is due to the arrangement of the periarticular connective tissues and, to a lesser extent, the interlocking of the articular surfaces. FIGURE 5-13. An anterior-lateral view of the articular surfaces of the right sternoclavicular joint. The latissimus dorsi muscle attaches to the floor of the intertubercular groove, medial to the biceps tendon. FIGURE 5-14. Upward rotation—The inferior angle of the scapula rotates in a superior-lateral direction, facing the glenoid fossa upward. The longitudinal diameters (purple) extend roughly in the frontal plane between superior and inferior points of the articular surfaces. Shoulder complex. The articulations between the bones make up the shoulder joints. The dashed line around the ends of the clavicle show attachments of the joint capsule. The SC joint functions as the basilar joint of the entire upper extremity, linking the appendicular skeleton with the axial skeleton. 4. The conoid ligament extends almost vertically from the proximal base of the coracoid process to the conoid tubercle on the clavicle. CHAPTER 6 Biomechanics of the Shoulder Eiji Itoi, MD, PhD, Bernard F. Morrey, MD, Kai-Nan An, PhD Because of its component parts, a description of the biomechanics of the shoulder complex is rather involved. Located at the superior and inferior rim of the glenoid fossa are the supraglenoid and infraglenoid tubercles. The AC joint is surrounded by a capsule that is directly reinforced by superior and inferior ligaments (Figure 5-17).36,105 The superior capsular ligament is reinforced through attachments from the deltoid and trapezius.
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