Anatomy of the Shoulder Complex

• The shoulder complex has 5 joints.
• The shoulder girdle includes the clavicle and scapula.
• The shoulder joint consists of the humerus and scapula.
• The shoulder has lots of mobility but little stability
• This limited stability in the shoulder is like a golf ball on a tee.

Bones

• The manubrium contains a shallow depression for medial clavicular attachments.
• The manubrium has a sternal or jugular notch.
• The clavicle is S-shaped.
• The tubular part of the clavicle is at the sternal end
• The flatter end of the clavicle is at the acromial end.
• The scapula is a flat, triangular bone
• The vertebra border of the scapula is positioned between T2 and T7
• The scapula provides a location for glenohumeral muscles and a stable base for the GH joint
• The scapula works with the clavicle to enhance total shoulder range of motion (ROM).
• The anterior scapula has the acromion process, the coracoid process, and subscapular fossa
• The glenoid fossa is located on the lateral scapula
• The glenoid labrum deepens 50%
• The posterior scapula has the spine, supraspinous fossa, infraspinous fossa, medial border, lateral border, superior border, superior angle, and inferior angle
• Structures of the humerus include: the head, anatomic neck, surgical neck, deltoid tuberosity, greater tubercle, lesser tubercle, and the bicipital groove aka "intertubercular groove"

Joints of the Shoulder Complex

• True joints include the sternoclavicular (SC), acromioclavicular (AC), and glenohumeral (GH) joints.
• Functional joints include the scapulothoracic and coracoacromial joints.
• Ligaments of the Sternoclavicular Joint
  • Interclavicular Lig.
  • Anterior SC Lig.
  • Posterior SC Lig.
  • Costoclavicular Lig.
• Motions of the Sternoclavicular Joint
  • Elevation/depression
  • Protraction/retraction
  • Rotation
• The lateral end of the clavicle joins with acromion process of scapula at the Acromioclavicular Joint
• The Acromioclavicular Joint has incongruent joint surfaces
• Ligaments of the Acromioclavicular Joint include
  • AC Ligament
  • Coracoclavicular Ligament (Conoid and Trapezoid)
• Motions of the Acromioclavicular Joint are linked to sternoclavicular and scapulothoracic motions
  • Elevation/Depression
  • Abduction/Adduction
  • Upward/Downward Rotation

Scapulothoracic Joint

• The scapula lies atop the rib cage
• The Scapulothoracic Joint has no ligaments
• The Scapulothoracic Joint is closely related to SC and AC joint function
• Scapulothoracic Joint Function aids to:
  • Increase ROM of the shoulder
  • Maintain favorable length-tension relationship for the deltoid muscle to function above 90 degrees
  • Provide glenohumeral stability through maintained glenoid and humeral head alignment for work in overhead position
  • Shock absorption to the outstretched arm
  • Permit elevation of the body
• Motions of Scapulothoracic Joint
  • Elevation
  • Depression
  • Protraction
  • Retraction
  • Upward Rotation
  • Downward Rotation
• The coracoacromial arch is formed by coracoacromial lig.
• It helps prevent superior translation of the humerus
• The coracoacromial arch is not a true joint
• The Glenohumeral Joint is a ball & socket joint
• The head of humerus sits in shallow glenoid fossa
• The glenoid labrum deepens socket
• Ligaments of Glenohumeral Joint
  • Joint Capsule
  • Coracohumeral Lig.
  • Glenohumeral Ligs (Anterior GH Lig., Posterior GH Lig.,Inferior GH Lig.)
  • Transverse humeral Lig.
• Dynamic Support of Glenohumeral Joint
  • Rotator Cuff (Supraspinatus, Infraspinatus, Teres Minor, Subscapularis)

Scapular Stabilizing Muscles

• Anterior
  • Pectoralis minor
  • Serratus Anterior
  • Subclavius
• Posterior
  • Levator Scapulae
  • Rhomboids
  • Trapezius
• Pectoralis Minor
  • O: Ribs
  • I: Coracoid process
  • A: Anterior tilt of the scapula
  • N: Medial pectoral n.
• SERRATUS ANTERIOR
  • O: Angles of ribs (1-9)
  • I: Medial border of scapula
  • A: Scapular protraction
  • N: Long thoracic
• SUBCLAVIUS
  • O: 1st rib
  • I: Inferior clavicle
  • A: Depresses clavicle
  • N: Nerve to subclavius
• LEVATOR SCAPULAE
  • O: Transverse processes of C1-C4
  • I: Superior/medial portion of scapula
  • A: Scapular elevation, Neck lateral flexion, Neck ipsilateral rotation
  • N: Nerve roots C2-C4
• RHOMBOID MAJOR
  • O: T2 – T5
  • I: Medial border of scapula
  • A: Scapular retraction, Downward rotation, Elevation
  • N: Dorsal scapular n.
• RHOMBOID MINOR
  • O: C7 – T1
  • I: Medial border of scapula
  • A: Scapular retraction, Downward rotation, Elevation
  • N: Dorsal scapular n.
• UPPER TRAPEZIUS
  • O: Ext occipital protuberance, Occiput, SP of C7
  • I: Lateral 1/3 clavicle, Acromion process, Spine of scapula
  • A: Scapular Elevation, Upward rotation; Neck Extension, Lateral flexion, Contralateral rotation
  • N: Spinal Accessory n.
• MIDDLE TRAPEZIUS
  • O: SP of T1-T3
  • I: Lateral 1/3 clavicle. Acromion process, Spine of Scapula
  • A: Scapular Retraction "adduction”, Upward rotation
  • N: Spinal Accessory n.
• LOWER TRAPEZIUS
  • O: SP of T4-T12
  • I: Lateral 1/3 clavicle. Acromion process, Spine of scapula
  • A: Scapular: Upward rotation, Retraction "Adduction", Depression
  • N: Spinal Accessory n.

Shoulder Joint Muscles

• Anterior: Pectoralis major (RC), Coracobrachialis (RC), Biceps brachii
• Inferior: Subscapularis (RC), Latissimus dorsi, Teres Major
• Superior: Deltoid, Supraspinatus (RC)
• PECTORALIS MAJOR
  • O: Clavicle, Sternum, Ribs (2-6)
  • I: Crest of greater tubercle
  • A: Glenohumeral Adduction, Horizontal adduction, Medial rotation
  • N: Medial & lateral pectoral nn.
• CORACOBRACHIALIS
  • O: Coracoid process
  • I: Medial 1/3 of humerus
  • A: Glenohumeral joint Flexion, Horizontal adduction
  • N: Musculocutaneous n.
• BICEPS BRACHII
  • O: Glenoid (long head), Coracoid (short head)
  • I: Tuberosity of radius
  • A: Shoulder flexion (weak), Elbow flexion, Supination
  • N: Musculocutaneous n.
• SUBSCAPULARIS (RC)
  • O: Subscapular fossa
  • I: Lesser tubercle
  • A: Medial Rotation
  • N: Subscapular n.
• DELTOID
  • O: Scapula (Acromion process,Spine of scapula), Clavicle
  • I: Deltoid tuberosity
  • A: Flexion (ant.), Abduction (mid.), Extension (post.)
  • N: Axillary n.
• SUPRASPINATUS (RC)
  • O: Supraspinous Fossa
  • I: Greater tubercle
  • A: Abduction
  • N: Suprascapular n.
• INFRASPINATUS (RC)
  • O: Infraspinous Fossa
  • I: Greater tubercle
  • A: Lateral Rotation
  • N: Suprascapular n.
• TERES MINOR (RC)
  • O: Lateral border of scapula
  • I: Greater tubercle
  • A: Lateral Rotation
  • N: Axillary n.
• LATISSIMUS DORSI
  • O: Thoracolumbar fascia, Thoracic vertebrae, Lumbar vertebrae
  • 1: Crest of lesser tubercle
  • A: Extension, Adduction, Medial rotation
  • N: Thoracodorsal n.
• TERES MAJOR
  • O: Lateral border of scapula
  • I: Crest of lesser tubercle
  • A: Extension, Adduction, Medial rotation
  • N: Subscapular n.
• TRICEPS BRACHII
  • O: Lateral border of scapula (long head), Posterior humerus (medial & lateral heads)
  • I: Olecranon process
  • A: Shoulder extension (weak), Elbow extension
  • N: Radial n.
• Nerve roots of C5-T1 make up the Brachial Plexus
• The Brachial Plexus supplies almost all of upper extremity
• The Brachial Plexus:5 terminal branches
  • Radial n.
  • Median n.
  • Ulnar n.
  • Musculocutaneous n.
  • Axillary n.
• Coordination of movements between the clavicle, scapula, and humerus is Scapulohumeral rhythm
• To properly function, all 4 joints must work together in a specific fashion
  • Glenohumeral Joint (GH)
  • Scapulothoracic (ST)
  • Sternoclavicular (SC)
  • Acromioclavicular (AC)
• Shoulder elevation in the scapular plane:Normal elevation with properly functioning muscles
• Muscles of the rotator cuff attach to the humeral head to maintain the humerus in proper position in the lower portion of the glenoid fossa so the shoulder appears to have a slight shrug as the arm elevates
• 180º of Total Abduction/Flexion
  • GH has 120º of abduction or flexion
  • If scapula was immobile, only 120º of abduction or flexion would be possible
  • ST, SC, and AC contribute the remaining 60°
• 2:1 ratio of GH:ST movement through full 180º of motion is achieved in Scapulohumeral Rhythm
• Phase 1: 0º- 90º of the following contributions:
  • GH contribution: 60º abduction/flexion of humerus
  • ST contribution: 30º upward rotation of scapula, corresponds with 30º of clavicular elevation at the SC joint, Costoclavicular ligament limits amount of clavicular elevation
• Phase 2: 90°-180° of the following contributions:
  • GH contribution: 60º abduction/flexion of humerus
  • ST contribution: 30º upward rotation of scapula, Corresponds with 30º of posterior rotation at the AC joint
• Scapulohumeral Rhythm Review:
  • 180º total ROM
  • 120º GH abduction/flexion of humerus
  • 60º ST upward rotation of scapula
  • 30º SC elevation of clavicle
  • 30º AC rotation of clavicle
  • 2:1 ratio
• Summary of Shoulder Motion Table notes the Glenohumeral Motion, Scapulothoraic Motion, Sternoclavicular Motion, Acromioclavicular Motion for Flexion, Extension, Abduction, Adduction, Lateral rotation, Medial rotation, Horizontal abduction and Horizontal adduction.
• The shoulder is an inherently unstable joint
• Imbalances in posture and strength most commonly trigger problems
• There is a complex relationship between ligaments, joint capsule, muscles
• Compensation from other components is necessary in cases of dysfunction to prevent problems in the shoulder
• Scapular Dyskinesis is when the scapula is winging
• Muscle Imbalance of Scapula notes the muscle imbalances to trapezius, serratus anterior (upper), Rhomboids, trapezius, rotator cuff, serratus anterior (lower), Deltoid, Levator Scapulae due to muscle imbalance.