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POTH 225 - Intro to Biomechanics > L7 - Shoulder > Flashcards

L7 - Shoulder Flashcards

1
Q

Name the biomechanics studied about the shoulder?

A
  1. Motion: kinematics
  2. Stability: constraint
  3. Strength : force transmission
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2
Q

Describe the shoulder joint.
- classification
- degrees of movement
- real name

A

Triaxial: ball and socket
–> 3 degrees of freedom

Glenohumeral joint

See NDC p.9 for illustration

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3
Q

Name the movements of the shoulder joint.
- frontal plane
- sagittal plane
- transverse plane

A

Frontal: abduction - adduction
Sagittal: flexion - extension
Transverse: internal rotation - external rotation

See NDC p.9 for illustration
See NDC p.11 for ROM table **dont need to know

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4
Q

What is shoulder / arm elevation?

A

In our class (based on textbook), they are the same.
It is a combination of flexion and abduction
–> HELP exercise

See NDC p.10 for illustration

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5
Q

Activity and ROM
See NDC p.11-12 for table of ROM necessary for certain activities.

A

EATING
Abduction: 45-60°
Horizontal abduction: 70-100°

Dont need to eat

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6
Q

Name the bones that form the shoulder joint.

A
  1. Clavicle
  2. Scapula
  3. Humerus
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7
Q

Describe the clavicle.
- bone shape
- convex
- concave

A

Crank shaped strut

Convex towards sternum (neurovascular structures)
Concave towards humerus

See NDC p.14 for illustration

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8
Q

What are the functions of the clavicle in the shoulder joint? (3)

A
  1. Attaches shoulder to axial skeleton
  2. Force transmission to scapula
  3. Contributes to ROM
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9
Q

Describe the scapula.
- spinal levels
- primary function

A

Between T2 and T7
Primary function: muscle attachment

See NDC p.15 for illustration

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10
Q

Name the bony features of the scapula. (2)
Which is the roof over the humerus?

A
  1. Acromion (posterior)
  2. Coracoid (anterior)

–> Acromion is the roof of the humerus

See NDC p.15 for illustration

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11
Q

Name the acromion variations. (3)

A

Shape of acromion over humeral head

  1. Flat
  2. Curved
  3. Hook

See NDC p.16 for illustration

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12
Q

What explains the instability of the shoulder joint?

A

25%-30% of the humeral head is in the glenoid fossa.
–> Large mobility, little stability

See NDC p.17 for illustration

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13
Q

Describe the plane of the scapula. (3)

A
  1. Superior aspect 30°- 45° anterior to frontal plane.
  2. Slight anterior inclination
  3. Slight upward rotation

See NDC p.18 for illustration

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14
Q

Name the structures of the humerus. (8)
Are they anterior, posterior, medial or lateral?

A
  1. Humeral head (M)
  2. Greater tubercle: superior, middle and inferior facets (L)
  3. Lesser tubercle (A)
  4. Intertubercular groove (A)
  5. Deltoid tuberosity (L)
  6. Radial groove (P)

See NDC p.19 for illustration

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15
Q

What does the greater tubercle need to do to permit full arm elevation?

A

Externally rotate humerus so that the greater tubercule clears acromion process and acromioclavicular ligament.

Arm elevation with internal rotation of arm is more difficult than with external rotation.

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16
Q

What is the function of the radial groove?

A

The radial nerve travels in it.

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17
Q

Describe the humeral head inclination.

A

Angle between humeral shaft axis and humeral head axis is 135°.

See NDC p.20 for illustration

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18
Q

What is the angle of intorsion of the humerus?

A

Angle of intorsion = 30°

See NDC p.20 for illustration

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19
Q

Name the 4 joints of the shoulder.

A
  1. Acromioclavicular
  2. Sternoclavicular
  3. Glenohumeral
  4. Scapulothoracic
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20
Q

Describe the acromioclavicular joint.
- classification
- ROM (6)

A

Synovial joint

3 ROTATORY MOTIONS:
1. Internal/external rotation (vertical axis)
2. Anterior and posterior (ML/longitudinal axis)
3. Upward and downward rotation (anterior-posterior axis)

3 TRANSLATORY MOTIONS:
1. Anterior/posterior
2. Medial/lateral
3. Superior/inferior

See NDC p.22 for illustration

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21
Q

What is the function of the acromioclavicular joint?

A
  1. Allows additional ROM of the scapula on the thorax
  2. Allows force transmission through the UE.
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22
Q

Name the stabilizing structures of the acromioclavicular joint.

A
  1. Coracoclavicular ligaments
    - trapezoid ligament
    - conoid ligament
  2. Acromioclavicular ligament

See NDC p.23 for illustration + IDENTIFICATION

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23
Q

Coracoclavicular ligaments
What is the function of the trapezoid ligament?
What does it prevent?

A

Medial stability during medially directed blow to shoulder facilitated by trapezoid ligament

Prevents medial displacement of acromion relative to the clavicle.

See NDC p.24 for illustration

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24
Q

Coracoclavicular ligaments
What is the function of the conoid ligament?
What does it prevent?

A

Arm elevation: initially clavicle and scapula in upward rotation together.

Scapula continues to rotate upwards and CONOID tightens and eventually restricts the motion of the clavicle.

Clavicle becomes pulled in upwards rotation.

See NDC p.25 for illustration

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25
Name and describe the grades of an acromioclavicular joint injury?
1. Grade I = AC ligament stretched or partially torn 2. Grade II = AC ligament completely torn 3. Grade III = AC joint separation, tear of AC and coracoclavicular ligament and capsule See NDC p.27 for illustration
26
Describe the sternoclavicular joint. - classification - ROM (6)
Synovial joint = saddle joint 3 ROTATORY MOTIONS: 1. Elevation and depression (AP axis, Elevation 50° and Depression 10°) 2. Protraction and retraction (Vertical axis, 30°-60°) 3. Upward and downward rotation (ML axis) 3 TRANSLATORY MOTIONS: 1. Anterior/posterior 2. Medial/lateral 3. Superior/inferior See NDC p.28 for illustration
27
What is the function of the sternoclavicular joint?
Connects upper limb and axial skeleton.
28
Name the supporting ligaments of the sternoclavicular joint.
1. Anterior/posterior sternoclavicular 2. Interclavicular 3. Costoclavicular 4. Intraarticular disc See NDC p.29 for illustration
29
What is the impact of motion of the sternoclavicular joint on the acromial head?
Rotation of the sternoclavicular joint about an axis causes the head and opposite end of clavicle to move in opposite directions (seesaw). See NDC p.30 for illustration
30
Describe the scapulothoracic joint. - classification - ROM (5)
No true articulations! 2 translations 1. Elevation and depression 2. Abduction-adduction 3 rotations 1. Upward-downward rotation 2. Internal-external rotation 3. Scapular tilt See NDC p.32-33 for illustration
31
What is the effect of the motion of one scapulothoracic joint on the other?
When one scapula moves, the other scapula moves in the opposite direction.
32
Motion of Scapulothoracic Joint Describe upward and downward rotation of the scapula. What does upward rotation rely on?
Upward: glenoid fossa moves in superior direction Downward: glenoid fossa moves in inferior direction --> Total upward-downward ROM=60° Upward rotation also relies on clavicular elevation and posterior rotation See NDC p.34 for illustration
33
Motion of Scapulothoracic Joint Describe scapular tilt.
Anterior: superior border of scapula tips forward Posterior: superior border of scapula tips backwards See NDC p.35 for illustration
34
What are the 5 functions of the scapulothoracic joint?
1. Increase ROM of shoulder to enhance reach 2. Maintain favorable length-tension relationship for the deltoid to function >90° 3. Maintain G-H stability for overhead work 4. Shock absorption 5. Permits elevation of body (eg. push-up
35
Describe the glenohumeral joint. - classification - nb of degrees of freedom - stability
Ball and socket = 3 degrees of freedom Poor stability despite glenohumeral ligaments Capsule large, loose inferiorly
36
What is adhesive capsulitis?
Frozen shoulder
37
When is the shoulder in a closed packed position?
1. Abduction 2. External rotation
38
Describe the scapulohumeral rhythm in arm elevation. - ratio - movement of scapula - movement of humerus
Ratio approx 2:1 (GH:ST) --> 2° of glenohumeral motion = 1° scapulothoracic motion Scapula: posterior tilt, upward rotation, external rotation Humerus: anterior flexion, abduction See NDC p.37 for illustration
39
Name the contributions of the shoulder joints to 180° arm elevation.
GH: 120° abduction ST: 60° upward rotation SC: 30° elevation SC: rotates posteriorly AC: upward rotation 30° See NDC p.39 for illustration
40
What structures contribute to STATIC glenohumeral stabiltity? (7)
1. Coracohumeral ligament 2. Glenohumeral ligaments 3. Labrum = increases depth 4. Capsule = helps with constraint 5. Joint contact = ↑ contact = ↑ stability 6. Scapular inclination 7. Intraarticular Pressure = suction effect
41
What structures contribute to DYNAMIC glenohumeral stabiltity? (3)
1. Rotator cuff muscles: supraspinatus, infraspinatus, teres minor, subscapularis 2. Biceps 3. Deltoid
42
Name the signs/tests to determine instability in the shoulder.
1. Apprehension sign 2. Sulcus sign 3. Load and shift test
43
What is the apprehension sign? What instability does a positive sign indicate?
The arm is placed in abduction and external rotation. A positive sign = patient shows visible apprehension or resistance to further movement due to fear of dislocation. This indicates anterior instability of the shoulder. See NDC p.42 for illustration
44
What is the sulcus sing? What instability does a positive sign indicate?
The arm is pulled down. A positive sign = a gap between the humeral head and acromion of the shoulder. This indicates inferior instability. See NDC p.43 for illustration
45
What is the load and shift test? What instability does a positive sign indicate?
Stabilize the shoulder blade and apply force to the humeral head, moving it forward and backward. The examiner assesses for any translation or subluxation of the joint. Excessive translation = anterior-posterior instability. See NDC p.44 for illustration
46
What is assessed in shoulder instability? (4)
1. Etiology (traumatic vs atraumatic) 2. Degree of Instability (subluxation vs dislocation) 3. Unidirectional vs multidirectional 4. Generalized ligamentous laxity
47
What is the coracoacromial arch? What does it form? (2)
Ligament attaching the coracoid process to the acromion. It forms the sub-acromial space + roof of the glenohumeral joint. See NDC p.47 for illustration
48
What causes the subacromial space to narrow? What can this cause?
It narrows with elevation and internal rotation. Can cause impingement (irritation) of the supraspinatus and long head of biceps. Due to sustained or intermittent compression. See NDC p.48 for illustration
49
What are the 2 mechanisms that can cause subacromial space reduction?
1. Intrinsic mechanism 2. Extrinsic mechanism
50
Name an intrinsic mechanism for subacromial space reduction?
Factors within the tendon = cuff degeneration --> weak rotator cuffs
51
Name the extrinsic mechanisms for subacromial space reduction? (5)
1. Glenohumeral kinematics : glide path of humerus is not well alligned with GH fossa 2. Anatomical or bony deformity 3. Scapular kinematics: type 3 acromion shape (hook) 4. Ergonomics (job: painter, electrician) 5. Sports
52
Name a sport that can cause impingement of structures in the subacromial space?
Butterfly swimming --> repetitive internal rotation and abduction (narrows subacromial space) It is an extrinsic mechanism.
53
Name and describe the impingement tests.
1. Neer's test - passively elevate arm while in internal rotation 2. Hawkin's test - arm and elbow flexed at 90°, internally rotate arm --> Pain = impingement
54
What are the 2 ways a rotator cuff can tear?
1. Wear and tear 2. Traumatic
55
What happens if a patient tries to elevate arm with a torn supraspinatus?
The only movement possible will be done by the scapulothoracic joint. See NDC p.53 for illustration
56
What is the function of the deltoid?
The deltoid causes the humerus and humeral head to translate superiorly See NDC p.56 for illustration
57
What is the function of the supraspinatus?
The supraspinatus causes abduction of the humerus and compression of the humeral head. See NDC p.56 for illustration
58
What is the function of the infraspinatus and teres minor?
Initially pull humeral head downwards and then externally rotate humerus (positioning of greater tubercle). See NDC p.57 for illustration
59
Can the deltoid independently abduct the arm? What is necessary?
The deltoid cannot independently fully abduct (elevate) the arm. All rotator cuff muscles work to compress humeral head in glenoid fossa during arm elevation. See NDC p.56-57 for illustration
60
Name the muscles that sabilize the scapula. (5) When is scapular stabilization needed?
1. Serratus anterior 2. Trapezius 3. Rhomboids (major and minor) 4. Pectoralis Minor 5. Levator Scapulae Scapular stabilization is needed when we need to push something (ex: pushing car, crawling)
61
Scapula Force Couple What scapular stabilization muscles are used in upward scapular rotation?
1. Upper and lower trapezius 2. Serratus anterior See NDC p.60 for illustration
62
What causes medial winging of the scapula?
Serratus anterior weakness --> long thoracic nerve Unopposed trapezius pulling scapula medially. See NDC p.61 for illustration
63
What causes lateral winging of the scapula?
Trapezial weakness --> spinal accessory nerve Unopposed serratus anterior pulling scapula laterally. See NDC p.61 for illustration
64
Scapula Force Couple What scapular stabilization muscles are used in downward scapular rotation?
1. Pectoralis minor 2. Levator scapulae 3. Rhomboids (major and minor) See NDC p.63 for illustration
65
What other LARGE muscles are important for the shoulder joint?
1. Latissimus Dorsi 2. Teres Major 3. Pectoralis Major 4. Coracobrachialis
66
What large muscles are important for shoulder depression? What activity depends on them?
1. Latissimus Dorsi 2. Pectoralis Major Weight bearing with upper extremity: crutches, transferring from wheelchair See NDC p.65 for illustration
67
When is compressive load on the shoulder joint highest during arm abduction? Why?
Compressive load on joint, so joint reaction forces, are highest when arm is 90° abducted. At 90° abduction, the moment arm of gravity is the furthest from the shoulder center of rotation See NDC p.66-67 for the graph + illustration
68
Shoulder elevation in the plane of the scapula occurs....
Occurs 30-45 degrees anterior to the frontal plane

POTH 225 - Intro to Biomechanics (14 decks)

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