Functional Anatomy of the Shoulder Complex

Learning Objectives

  • Describe the bones, joints, and muscles contributing to purposeful movement of the shoulder complex.

  • Identify the primary purposeful movements of the shoulder within the context of occupational performance.

  • Develop competency in goniometry and manual muscle testing (MMT) as clinical assessment techniques for the shoulder.

  • Use clinical reasoning to identify limitations of the shoulder that may affect occupational performance.

Key Concepts

  • Adhesive Capsulitis: A condition characterized by stiffness and pain in the shoulder joint, often referred to as frozen shoulder.

  • Bicipital Tendinitis: Inflammation of the bicep tendon, leading to pain in the shoulder and upper arm.

  • Dynamic Stability: The ability of the musculoskeletal system to maintain stability while in motion.

  • Scapular Winging: A condition where the shoulder blade protrudes from the back due to weak muscles or injury.

  • Scapulohumeral Rhythm: The coordinated movement of the scapula and humerus during shoulder motion.

  • Shoulder Separation: An injury caused by a direct blow to the shoulder, often resulting in the clavicle being displaced from the acromion.

  • Fall on Outstretched Hands (FOOSH): A common mechanism of injury where a person falls and lands on an outstretched arm, potentially leading to fractures or dislocations.

  • Static Stability: Stability of the joint in a stationary position, reliant on joint structure and connective tissue.

  • Glenohumeral Subluxation: A partial dislocation of the shoulder joint, often seen in individuals with neurological impairments.

  • Hemiparesis: Weakness on one side of the body, often resulting from a stroke or neurological conditions.

  • Rotator Cuff: A group of muscles and their tendons that act to stabilize the shoulder.

  • Subacromial Impingement: Compression of tendons or bursa in the shoulder, leading to pain, especially during overhead activities.

  • Thoracic Outlet Syndrome (TOS): A group of disorders that occur when blood vessels or nerves in the space between the collarbone and the first rib are compressed.

  • Scaption: A movement pattern that combines flexion and abduction, occurring in the scapular plane.

  • Scapular Dyskinesis: Abnormal movement of the scapula during shoulder motions.

  • Scapular Plane: A position where the shoulder blade is rotated forward, facilitating more natural movement.

The Shoulder: A Functional Link

  • The shoulder complex is crucial for various leisure occupations such as yoga, biking, or playing an instrument. It plays a vital role in positioning and stabilizing the arm for manipulative tasks.

  • The shoulder acts as a functional connection between the trunk and the upper limb, enabling gross motion and stability.

  • For optimal occupational performance, understanding the anatomy of the shoulder complex is essential.

Osteology: Bones of the Shoulder Complex

  • Bones involved: Scapula, humerus, and clavicle.

  • Scapula: A flat, triangular bone situated at the back, covering the second through seventh ribs, serves as an attachment for multiple muscles that provide stability and motion (5.1).

Bony Landmarks of the Scapula

  • Borders: Three main borders—medial (vertebral), lateral (axillary), and superior.

  • Angles: Three angles found at the junctions of the borders,

    • Superior Angle: Junction of vertebral and superior borders.

    • Inferior Angle: Junction of vertebral and axillary borders.

    • Lateral Angle: Contains the glenoid fossa, where the humerus articulates.

  • Coracoid Process: An important attachment point for muscles and ligaments, enhancing stability of the scapula against the rib cage.

Clinical Application: Manual Scapular Mobilization

  • Palpation and Mobilization: Important for assessing mobility, restoring range of motion in patients experiencing cervical injuries, strokes, and immobility following injury.

  • Manual mobilization may be needed to facilitate shoulder motion post-injury or after immobilization that leads to tightness.

Scapular Plane (Scaption)

  • Scaption Movement: This movement aligns the humerus with the scapula, facilitating a more natural and comfortable range of motion for overhead activities. It is often utilized in clinical settings to reduce discomfort during rehabilitation post-surgery.

  • Patient Experience: By providing support to the shoulder complex in the scapular plane, patients report reduced strain during movements, enhancing participation in therapeutic interventions.

Clavicle

  • Structure: S-shaped bone, which connects the chest to the upper arm (5.7).

  • Bony Landmarks of the Clavicle: The medial end articulates with the manubrium, while the lateral end forms a joint with the acromion.

Humerus

  • Structure: A long bone connecting the trunk and forearm, significant for shoulder mobility (5.9).

  • Bony Landmarks of the Humerus: Includes the larger greater tubercle and smaller lesser tubercle, with the anatomical and surgical necks playing roles in joint stability and injury susceptibility.

Surgical Neck Fractures

  • Clinical Concern: The surgical neck is a common area for fractures, especially in high-impact activities, where a fall or impact can lead to injuries requiring surgical interventions.

  • The radial nerve, which runs alongside the midshaft, can be affected in midhumeral fractures, leading to wrist drop due to paralysis of radial innervated muscles.

Joints of the Shoulder Complex

Scapulothoracic Joint

  • Classification: Atypical joint with functional gliding movements like elevation, depression, and rotation.

  • Movement: Plays a crucial role in positioning the glenoid fossa for humeral motion, vital for scapular stability during overhead activities.

Sternoclavicular Joint

  • Classification: Saddle joint; provides the only direct bony connection of the shoulder complex to the axial skeleton.

  • Movements: Elevation, depression, protraction, retraction, and rotation.

  • Clinical Insight: Vulnerable to injuries, particularly during falls, given its role in the upper limb's kinematic functions.

Acromioclavicular Joint

  • Classification: Gliding joint that permits limited movement between the acromion and clavicle.

  • Innate Susceptibility: Prone to dislocations, particularly with lateral impacts, often described as shoulder separation which results in misalignment of the clavicle with the acromion.

Glenohumeral Joint

  • Classification: Ball-and-socket joint enabling extensive movement (flexion, extension, abduction/adduction, rotation).

  • Configuration: The larger humeral head articulates with the shallow glenoid fossa, leading to a trade-off between mobility and stability (5.17-5.19).

  • Dynamic support: Surrounding muscular structures are crucial for maintaining joint stability and preventing dislocations, especially in patients with neurological impairments.