in this lecture students learn about biomechanics of shoulder unit including: bones, joints, movements and muscles

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Lecture 2: Biomechanics of
Shoulder Unit
By: Dr. Ali Selk Ghafari
Email: a_selkghafari@sharif.edu
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2.1 Pectoral Girdle
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
Section Summary
Bones of the pectoral girdle
Scapula
• Triangular bone located on the posterolateral
aspect of the thorax.
• Has superior, lateral and inferior angles;
medial, lateral and superior borders; posterior
spine; laterally projecting acromion; anteriorly
projecting coracoid process.
• Articulates with head of humerus at glenoid
fossa forming the shoulder (glenohumeral)
joint; clavicle at acromion forming
acromioclavicular joint.
Clavicle
• Curved bone – medially convex anteriorly,
laterally concave anteriorly.
• Has smooth superior surface; roughened
inferior surface; expanded medial and flattened
lateral ends.
• Articulates with acromion of scapula laterally
forming acromioclavicular joint; sternum
medially forming sternoclavicular joint.
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2.1.1 Pectoral Girdle: Bones – Scapula
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Superior angle
Acromion
Spine
Acromion
Inferior angle
(a) Anterior view (b) Posterior view
Suprascapular
notch
Coracoid
process
Glenoid
cavity
Subscapular
fossa
Lateral
border
Medial
border
Superior
border
Supraspinous
fossa
Lateral
angle
Infraspinous
fossa
Scapula
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2.1.1 Pectoral Girdle: Bones – Clavicle
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Conoid tubercle
Conoid tubercle
(a) Superior view
(b) Inferior view
Sternal
end
Acromial
end
Acromial
end
Sternal
end
Clavicle
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2.2 Pectoral Girdle Muscles
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.2.1 Pectoral Girdle: Movement
The movements of the shoulder girdle are described as:
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.2.2 Pectoral Girdle: Retracting Muscles
• Muscles retracting the
pectoral girdle:
– Rhomboid minor
– Rhomboid major
– Trapezius
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.2.3 Pectoral Girdle: Protracting Muscles
• Muscles protracting the
pectoral girdle:
– Serratus anterior
– Pectoralis minor
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.2.4 Pectoral Girdle: Elevating Muscles
• Muscles elevating the
pectoral girdle:
– Trapezius (upper fibres)
– Levator scapulae
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.2.5 Pectoral Girdle: Laterally Rotating Muscles
• Muscles laterally rotating
the pectoral girdle:
– Trapezius
– Serratus anterior
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.3 Shoulder Joint Movements
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.3 Shoulder Joint Movements
• The movements of the shoulder joint will be considered as:
– Abduction and adduction in the coronal plane,
– Flexion and extension in the sagittal plane,
– Medial and lateral rotation about the long axis of the arm.
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.3.1 Shoulder Joint Abducting Muscles
• Muscles abducting the arm
at the shoulder joint:
– Supraspinatus
– Deltoid
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.3.2ShoulderJoint Flexing Muscles
• Muscles flexing the arm
at the shoulder joint:
– Pectoralis major
– Deltoid (anterior fibres)
– Biceps brachii – long head
– Coracobrachialis
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.3.3ShoulderJoint Extending Muscles
• Muscles extending the arm
at the shoulder joint:
– Latissimus dorsi
– Teres major
– Pectoralis major
– Deltoid (posterior fibres)
– Triceps (long head)
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.3.4ShoulderJoint Adducting Muscles
• Muscles adducting the arm
at the shoulder joint:
– Coracobrachialis
– Pectoralis major
– Latissimus dorsi
– Teres major
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.3.5ShoulderJoint Medially Rotating Muscles
• Muscles medially rotating
the arm at the shoulder
joint:
– Subscapularis
– Teres major
– Latissimus dorsi
– Pectoralis major
– Deltoid (anterior fibres)
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.3.6ShoulderJoint Laterally Rotating Muscles
• Muscles laterally rotating
the arm at the shoulder
joint:
– Teres minor
– Infraspinatus
– Deltoid (posterior fibres)
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.3.7Muscles of the Shoulder Region and Arm
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.4 Shoulder Complex: Joints
Shoulder Complex
• The clavicle articulates with the
thorax by the sternoclavicular
joint, and with the shoulder
blade by the acromioclavicular
joint.
• The humerus of the upper limb
joins the shoulder blade at the
glenohumeral joint.
• It is the summation of the
mobility of these three individual
joints which gives the upper limb
its freedom of movement.
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.4.1 Shoulder Complex: Sternoclavicular Joint
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.4.1 Shoulder Complex: Sternoclavicular Joint
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.4.1 Shoulder Complex: Sternoclavicular Joint
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
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2.4.2 Shoulder Complex: Acromioclavicular Joint
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2.4.4 Shoulder Complex: Shoulder Joint
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
Glenoid labrum
Glenoid labrum
Supraspinatus
tendon
Acromion
Capsular ligament
Humerus
Frontal section of shoulder joint
Subdeltoid
bursa
Deltoid
muscle Synovial
membrane
Glenoid cavity
of scapula
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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2.4.4 Shoulder Complex: Shoulder Joint
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Acromion
Tendon sheath
Humerus
Clavicle
Acromioclavicular ligament
Subacromial
bursa
Supraspinatus
tendon
Coracohumeral
ligament
Subdeltoid
bursa
Subscapularis
tendon
Transverse
humeral
ligament
Biceps brachii
tendon
(long head)
Anterior view of shoulder joint
Glenohumeral
ligaments
Subscapular
bursa
Subcoracoid
bursa
Coracoid
process
Coraco-
acromial
ligament
Coraco-
clavicular
ligament
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2.4.4 Shoulder Complex: Shoulder Joint
Dr. A. Selk Ghafari, Biomechanics of Musculoskeletal System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Coracoid process
Coracohumeral ligament
Subscapular bursa
Subscapularis tendon
Acromion
Supraspinatus
tendon
Subdeltoid
bursa
Infraspinatus
tendon
Glenoid cavity
(articular cartilage)
Synovial membrane
(cut)
Teres minor
tendon
Lateral view , humerus removed
Inferior glenohumeral
ligament
Middle glenohumeral
ligament
Biceps brachii tendon
(long head)
Superior glenohumeral
ligament
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