Week 12, Thursday

Clinical Anatomy of the Shouldefr ppt.

Six Kinematic Principles Associated with Full Abduction of The shoulder:

  • 180* of active shoulder abduction comes from 120* of GH joint abduction and 60* of ST upward rotation

  • 60* of upward rotation of the scapula is a result of combined movements of the sternoclavicular and acromioclavicular joints

  • Clavicle retracts at the SC joint during shoulder abduction

  • Scapula posteriorly tilts and externally rotates during full shoulder abduction

  • Clavicle posteriorly rotates around its own axis during shoulder abduction

  • The GH joint externally rotates during shoulder abduction

GH translation:

  • GH translation is less during active shoulder motion than during passive shoulder motion

  • In abduction of the GH joint in the plane of scapula, the humeral head undergoes minimal superior glide and then remains fixed or glides inferiorly no more than 1mm

  • Individuals with muscle fatigue or GH instability consistently demonstrate excessive superior glide during active shoulder elevation

Concave-Convex rule:

  • the convex humeral head glides on the concave glenoid fossa in directions opposite the humeral roll

  • The concave-convex rule does not apply to the GH joint

  • The humeral head slides posteriorly in shoulder extension and in external rotation

  • It slides anteriorly during abduction and medial rotation

Sternoclavicular and Acromioclavicular joint motion during arm elevation:

  • total scapular upward rotation is ~ 60*, while total clavical elevation. Is about 40*

    • This difference suggests that the scapula and clavicle move separately at the AC joint

  • The clavicle rotates in a “crank” mechanism, with the confidence ligament keeping the conoid tubercle close to the coracoid process, allowing the proximal and distal ends of the clavicle to “rotate” and provide additional ROM without using all of the possible ROM form the SC joint

Anterior Pectoral Muscles:

  • AKA axia-appendicular or Thoraco-appendicular muscles

  • Move the Pectoral girdle

  • Muscles:

    • Pec Major

    • Pec Minor

    • Subclavius

    • Serratus Anterior

Pec Major:

  • Proximal attachment:

    • Sternocostal head

      • Anterior surface of sternum, upper 6 costal cartilages, aponeurosis of external oblique muscle

    • Clavicular head:

      • Anterior surface of medial half of clavicle

  • Distal attachment:

    • Lateral lip of intertubercular sulcus

  • Action:

    • Adduct and internally rotate humerus

Pec Minor:

  • Proximal Attachment

    • Anterior 3-5 ribs

  • Distal Attachments:

    • Coracoid process

  • Action:

    • Pulls scapula inferiorly ad anteriorly

Subclavius:

  • Proximal attachment:

    • 1st costochondral junction

  • Distal attchment:

    • Inferior surface of distal clavicle

  • Action:

    • Stabilize and depress clavicle

Serratus Anterior:

  • Proximal atttachment:

    • Lateral aspects of ribs 1-8

  • Distal attachment:

    • Anterior aspect f te medial boarder of the scapula

  • Action:

    • Protract scapula

    • Stabilize scapula against thoracic wall

    • Upwardly rotate scapula

Posterior Extrinsic shoulder muscles:

  • AKA Axio-appendicular muscles

  • Superficial:

    • Trapezius (“the only Innervation I will test you on is the Trapezius because it’s easy”- Williams)

    • Lat. Dorsi

  • Deep:

    • Levator scapulae

    • Rhomboid Major

    • Rhomboid Minor

  • Know the Attachments and Actions of all of these

Scapulohumeral Muscles:

  • AKA Intrinsic shoulder muscles

  • Muscles:

    • Deltoid

    • Teres major

    • Supraspinatus

    • Infraspinatus

    • Teres minor

    • Subscapularis

  • Know the attachments and Actions of all of these musles

SITS Muscle Actions:

  • Supraspinatus= abducts the shoulder

  • Infraspinatus= externally rotates the shoulder

  • Teres Minor= externally rotates the shoulder

  • Subscapularis= internally rotates and adducts the shoulder

Brachial muscles with an affect on the shoulder:

  • Biceps Brachii

  • Coracobrachialis

  • Triceps Brachii

  • Know the attachments and Actions of all these muscles

Common injuries of the Shoulder:

  • Shoulder pain is one of the most common reasons people seek out treatment with a health care provider:

    • Only low back pain, neck pain, and headaches are more common

  • Injury to the shoulder joint makes up 8-13% of all sports-related injuries

Impingement Syndrome:

  • The most common cause of shoulder pain and/or dysfunction

  • Most commonly occurs in people who engage in overhead activities or forceful movements of the shoulder

  • The most common type of impingement syndrome is called subacromial impingement syndrome

  • Repetitive injury of the structures in the subacromial space

    • Supraspinatus tendon, subacromial/subdeltoid bursa, tendoson of the long head of the biceps brachii

  • Impinging structures include the acromion process and/or the coracoacromial ligament

Subacromial impingement syndrome:

  • The Supraspinatus tendon is the most commonly affected, due to anatomical location and perhaps even blood supply characteristics

  • Predisposing anatomical features include:

    • a hooked acromion

    • osteophyte at the coracoacromial ligament insertion

    • perhaps AC joint osteophytes

  • Activities that predispose to this syndrome include most overhead throwing sports and swimming

    • Swimmers are particularly at risk due to medial rotation of the humerus when the shoulder is abducted

Shoulder Dislocation:

  • The most of only dislocated joint in the entire human body is eh Glenohumeral joint

  • The most common type of dislocation is anterior, with the anterior-inferior subtype being the most common

  • The usual mechanism of injury is Abduction and external rotation wit an anterior shear-type force applied tot eh humeral head

  • Once a dislocation has occurred, the joint is rendered more unstable and is usually prne to additional dislocations

Shoulder Separations:

  • Dislocations of the acromioclavicular joint, also called separations, are also quite common.

  • The typical mechanism is a fall on an outstretched hand or even the point of the shoulder.

  • Different grades of AC joint separation have been described, with types I and II typically being managed conservatively.

  • Types III and up are often surgical candidates.

  • Fractures of the clavicle occur by the same mechanism and may be present with AC joint injury.

Rotational Injuries:

  • Tears of the labrum, rotator cuff tendons, and long head of the biceps tendon can all occur from repetitive forceful rotation at the shoulder.

    • Examples include overhead throwing, serving in tennis, and spiking a volleyball.

  • Fatigue of the shoulder girdle musculature has been implicated in the development of these injuries.

  • Rotator cuff tears may be due to the large tensile loads placed upon them when decelerating the arm.

  • Suprascapular nerve injury can occur as well with repetitive loading.

Adhesive Capsulitis (Frozen Shoulder):

  • Capsular tightening of the shoulder of unknown etiology

  • Most common in females and middle-aged elderly women

  • Maybe a progression of rotator cuff inflammation

  • Decrease in Range of Motion in shoulder

Shoulder Instability:

  • Dislocation

  • Subluxation

Traumatic Instability:

  • Related to a specific injury

  • Usually needs some form of surgical intervention

  • ~15% success with conservative therapy

  • Usually unilateral with unilateral direction insufficiency

Atraumatic Instability:

  • usually bilateral and multidirectional

Shoulder Laxity:

  • Patient can be born like this

  • Usually doesn’t hurt

  • Strengthening can help increase stability