Chapter 14 The Shoulder Complex

Overview The shoulder is a complex set of articulations that work together toward the common goal of positioning the hand in space, which allows an individual to interact with the environment and to perform fine motor functions

Anatomy Although the entire shoulder complex functions as an integrated unit, it is anatomically simpler to describe each joint separately. The shoulder joint complex consists of: Three bones (the humerus, the clavicle, and the scapula) Three joints (the sternoclavicular (S-C), the acromioclavicular (A-C), and the glenohumeral (G-H) joints) One “pseudojoint” One physiological area

Anatomy Glenohumeral Joint The glenohumeral (G-H) joint is a true synovial-lined diathrodial joint that connects the upper extremity to the trunk, as part of a kinetic chain The GH joint is formed by the humeral head and the glenoid fossa of the scapula

Anatomy Glenoid fossa The glenoid fossa is flat, but is made approximately 50% deeper and more concave by a ring of fibrocartilage called a labrum The labrum, which forms part of the articular surface, is attached to the margin of the glenoid cavity and the joint capsule, and contributes to joint stability

Anatomy Scapula The scapula forms the base of the G-H joint It is a flat blade of bone that lies along the thoracic cage at 30° to the frontal plane, 3° superiorly relative to the transverse plane, and 20° forward in the sagittal plane The scapula’s wide and thin configuration allows for its smooth gliding along the thoracic wall, and provides a large surface area for muscle attachments both distally and proximally

Anatomy Scapula A prominent feature of the scapula in man is the large overhanging acromion, which, along with the coracoacromial ligament functionally enlarges the glenohumeral socket The position of the acromion also places the deltoid muscle in a dominant position to provide strength during elevation of the arm Although the acromion appears to be flat, three types of acromion morphology have been described, of which the hooked is associated with an increase in rotator cuff pathology

Anatomy Joint capsule The voluminous joint capsule of the glenohumeral joint allows for large amounts of motion to occur at the G-H joint The lateral attachment of the glenohumeral joint capsule attaches to the anatomical neck. Medially, the capsule is attached to the periphery of the glenoid and its labrum The overall strength of the joint capsule bears an inverse relationship to the patient’s age: the older the patient, the weaker the joint capsule

Anatomy The greater and lesser tuberosities Located on the lateral aspect of the anatomical neck of the humerus Serve as attachment sites for the tendons of the rotator cuff muscles The greater tuberosity serves as the attachment for the supraspinatus, infraspinatus and teres minor The lesser tuberosity serves as the attachment for the subscapularis The greater and lesser tuberosities are separated by the intertubercular groove, through which passes the tendon of the long head of the biceps on its route to attach on the superior rim of the glenoid fossa

Anatomy The glenohumeral ligaments At the anterior portion of the outer fibers of the joint capsule, three local reinforcements are present: the superior, middle and inferior G-H ligaments (>Z= ligaments) Superior - serves to limit external rotation and inferior translation of the humeral head with the arm at the side Middle - serves to limit external rotation (Table 14-5) and anterior translation of the humeral head with the arm in 0° and 45° of abduction Inferior - consists of an anterior band, a posterior band, and an axillary pouch with varying functions

Anatomy The coracohumeral ligament Covers the superior G-H ligament anterior-superiorly, and fills the space between the tendons of the supraspinatus and subscapularis muscle; uniting these tendons to complete the rotator cuff in this area

Anatomy The coracoacromial ligament Consists of two bands that join near the acromion and is ideally suited, both anatomically and morphologically, to prevent separation of the A-C joint surfaces

Anatomy Coracoacromial Arch Formed by the anterior-inferior aspect of the acromion process, coracoacromial ligament, and inferior surface of the A-C joint During overhead motion in the plane of the scapula, the supraspinatus tendon, the region of the cuff most involved in the degenerative process, can pass directly underneath the coracoacromial arch If the arm is elevated while internally rotated, the supraspinatus tendon passes under the coracoacromial ligament, whereas if the arm is externally rotated, the tendon passes under the acromion itself

Anatomy Suprahumeral/subacromial space An area located on the superior aspect of the G-H joint Contents include the long head of biceps tendon, supraspinatus and upper margins of subscapularis and infraspinatus, subdeltoid-subacromial bursa The space is at its narrowest between 60° and 120° of scaption

Anatomy The subacromial bursa One of the largest bursa in the body Provides two smooth serosal layers; one of which adheres to the overlying deltoid muscle and the other to the rotator cuff lying beneath

Anatomy Neurology The shoulder complex is embryologically derived from C 5-8, except the A-C joint, which is derived from C 4. The sympathetic nerve supply to the shoulder originates primarily in the thoracic region from T 2 down as far as T 8

Anatomy Vascularization The vascular supply to the rotator cuff muscles of the shoulder consists of three main sources: the thoracoacromial, suprahumeral, and subscapular arteries The brachial artery provides the dominant arterial supply to each of the two heads of the biceps

Anatomy Glenohumeral joint Close packed position Open packed position The close packed position for the G-H joint is 90° of glenohumeral abduction and full external rotation; or full abduction and external rotation, depending on the source Open packed position Without internal or external rotation occurring, the open packed, or rest position of the G-H joint has traditionally been cited as 55° of semi-abduction and 30° of horizontal adduction

Anatomy Glenohumeral joint Capsular pattern According to Cyriax, the capsular pattern for the shoulder is external rotation the most limited, abduction the next most limited, and internal rotation the least limited in a 3:2:1 ratio respectively

Anatomy The acromioclavicular joint The acromioclavicular (A-C) joint is a diarthrodial joint, formed by the acromion and the lateral end of the clavicle The joint serves as the main articulation suspending the upper extremity from the trunk, and it is at this joint about which the scapular moves

Anatomy Acromioclavicular joint The articulating surface of the lateral end of the clavicle can be either convex or concave and corresponds with the articulating surface of the acromion. Consequently, although the joint is described as a planar joint, there is often a male-female relationship, with 3 degrees of freedom

Anatomy A-C ligaments The coracoclavicular ligaments (conoid and trapezoid) are the primary support for the A-C joint These ligaments provide mainly vertical stability, with control of superior and anterior translation as well as anterior axial rotation

Anatomy A-C joint Neurology. Innervation to this joint is provided by the suprascapular, lateral pectoral, and axillary nerves Capsular pattern. Lacks a true capsular pattern Close and open packed positions. Undetermined

Anatomy Sternoclavicular (S-C) joint Represents the articulation between the medial end of the clavicle, the clavicular notch of the manubrium of the sternum, and the cartilage of the first rib, which forms the floor of the joint Has been classified as a ball and socket joint, a plane joint, and as a saddle joint A meniscus completely divides the joint into two cavities

Anatomy Sternoclavicular (S-C) joint Ligaments. A number of ligaments provide support to this joint: Anterior sternoclavicular ligament Posterior sternoclavicular ligament Interclavicular Costoclavicular

Anatomy Sternoclavicular (S-C) joint Close packed position. The close packed position for the S-C joint is maximum arm elevation and protraction Open packed position. The open packed position for the S-C joint has yet to be determined, but is likely to be when the arm is by the side Capsular pattern. Lacks a specific capsular pattern

Anatomy Scapulothoracic Joint Functionally a joint but it lacks the anatomic characteristics of a true synovial joint Plays a significant role in all motions of the shoulder complex

Anatomy Muscles of the Shoulder Complex For simplicity, the muscles acting at the shoulder may be described in terms of their functional roles: scapular pivoters, humeral propellers, humeral positioners, and shoulder protectors

Anatomy Muscles of the Shoulder Complex Scapular pivoters Comprise the trapezius, serratus anterior, levator scapulae, rhomboid major, and rhomboid minor As a group, these muscles are involved with motions at the scapulothoracic articulation, and their proper function is vital to the normal biomechanics of the whole shoulder complex

Anatomy Muscles of the Shoulder Complex Humeral propellers Comprise the latissimus dorsi, pectoralis major, and pectoralis minor

Anatomy Muscles of the Shoulder Complex Humeral positioners. Comprised of the three parts of the deltoid muscle

Anatomy Muscles of the Shoulder Complex Shoulder protectors Rotator cuff Biceps brachii

Biomechanics Complete movement at the shoulder girdle involves a complex interaction between the glenohumeral, acromioclavicular, sternoclavicular, scapulothoracic, upper thoracic, costal and sternomanubrial joints, and the lower cervical spine During these motions, the scapula invariably acts as a platform upon which shoulder rotation and arm activities are based

Biomechanics The Scapulohumeral Rhythm The combination and synchronization of the motions that occur between the scapula and the humerus during arm elevation An early study by Inman determined that a 2:1 ratio existed between the motion occurring at the G-H joint and scapula respectively This ratio is not consistent throughout the range of motion

Biomechanics Force couples During the first 30° of upward rotation of the scapula, the serratus anterior muscle and the upper and lower divisions of the trapezius muscle are considered the principal upward rotators of the scapula Together these muscles form two force couples; one formed by the upper trapezius, and the upper serratus anterior muscles, the other formed by the lower trapezius, and lower serratus anterior muscles

Examination In the presence of shoulder girdle dysfunction (assuming systemic or orthopedic causes have been ruled out), there are three possible causes for shoulder girdle dysfunction Compromise of the passive restraint components of the shoulder girdle Compromise of the neuromuscular system’s production or control of shoulder girdle motion Compromise to one or more of the of the neighboring joints that contribute to shoulder girdle

Examination History A good history is the cornerstone of proper diagnosis, especially since shoulder pain has a broad spectrum of patterns and characteristics It is important to establish the patient’s chief presenting complaint (which is not always pain) as well as defining their other symptoms. The most common complaints associated with shoulder pathology include pain, instability, stiffness, deformity, locking, and swelling

Examination Systems review Symptoms that are not associated with movement should alert the clinician to a more serious condition Scenarios related to the shoulder that warrant further investigation by the clinician include an insidious onset of symptoms, and complaints of numbness or paresthesia in the upper extremity

Examination Observation The clinician observes how the patient holds the arm, the overall position of the upper extremity, and the willingness of the patient to move the arm Deformity is a common complaint with injuries of the A-C joint and fractures of the clavicle A number of static tests for the scapular position exist

Examination Palpation The optimal methods of palpating the shoulder tendons occur in regions where there is the least amount of overlying soft tissue It is best to divide the shoulder complex into compartments for palpation Symptoms reproduced by palpation in these compartments are frequently associated with a specific underlying pathology

Examination AROM, PROM with overpressure McClure and Flowers classify limited shoulder motion into two categories: Decreased ROM secondary to changes in the periarticular structures, including shortening of the capsule, ligaments, or muscles as well as adhesion formation. Clinical findings for this category include a history of trauma, immobilization, presence of a capsular pattern, capsular end-feel, and no pain with the isometric testing Decreased ROM due to nonstructural problems, including the presence of pain, protective muscle spasm, or a loose body within the joint space. Clinical findings for this patient include a history of trauma or overuse, and the presence of a non-capsular pattern

Examination Examination of the Dynamic Scapula Given the importance of the scapulothoracic joint to overall shoulder function, it is important to examine the scapulothoracic joint arthrokinematics, and muscle power

Examination Strength testing Localized, individual isometric muscle tests around the shoulder girdle can give the clinician information about patterns of weakness other than from spinal nerve root or peripheral nerve palsies e.g., instabilities, postural dysfunction, and also help to isolate the pain generators

Examination Examination of Movement Patterns These tests are concerned with the coordination, timing, or sequence of activation of the muscles during movement

Examination Functional Testing The assessment of shoulder function is an integral part of the examination of the shoulder complex The term shoulder function can include tests for biomechanical dysfunction and tests assessing the patient’s ability to perform the basic functions of activities of daily living

Examination Other test for the shoulder complex include: Muscle Length Tests Examination of the passive restraint system and neighboring joints Special Tests Diagnostic and imaging studies

Intervention Acute phase goals: Protection of the injury site Restoration of pain-free range of motion in the entire kinetic chain Improve patient comfort by decreasing pain and inflammation Retard muscle atrophy Minimize detrimental effects of immobilization and activity restriction Maintain general fitness Patient to be independent with home exercise program

Intervention Functional phase goals: Attain full range of pain free motion Restore normal joint kinematics Improve muscle strength to within normal limits Improve neuromuscular control Restore normal muscle force couples