Stress-Strain Curves, Material Properties, and Shoulder Biomechanics in Engineering and Anatomy

What is the definition of anisotropy in human tissue?

Different mechanical properties depending on the direction of the load.

How is being robust different from being anti-fragile?

Robustness is the ability to withstand stress, while anti-fragility means to thrive and grow from stress.

What are the differences in bone stiffness depending on loading rate?

Fast loading rate results in higher stiffness compared to slow loading rate.

List three reasons why muscles ought not to be described as springs.

1) Non-linear, 2) Length or joint angle can change without external force, 3) Muscle activation changes with activation levels.

What should we say instead of 'stiffness'?

Apparent stiffness.

How many articulations exist in the shoulder?

4.

Define the mobility/stability trade-off.

High mobility equals low stability.

What angle is the scapular plane relative to horizontal?

35 degrees.

What are the three borders of the scapula?

Medial, lateral, superior.

What muscle attaches on the infraglenoid tubercle?

Long head of triceps.

What muscle attaches on the coracoid process?

Pectoralis minor, short head of biceps, coracobrachialis.

What runs through the intertubercular groove of the humerus?

LHB tendon.

Describe the roll/slide mechanics of the sternoclavicular joint during abduction.

Superior roll and inferior slide of the clavicle.

True or False: The AC joint has roll/slide mechanics.

False.

What motion(s) would place the middle capsular ligament of the glenohumeral joint under tension?

External rotation or anterior translation.

Describe the arthrokinematics of the glenohumeral joint in flexion.

Spin.

Describe the arthrokinematics of the glenohumeral joint in abduction.

Superior roll and inferior slide.

Describe the arthrokinematics of the glenohumeral joint in internal rotation.

Anterior roll and posterior slide.

Define shoulder impingement.

When the humeral head rolls superior and compresses the supraspinatus against the acromion.

What is the scapulohumeral rhythm for full overhead reaching?

2:1 ratio; 120 degrees from GH joint, 60 degrees from ST.

What is the upward scapular rotation during overhead reaching?

60 degrees of upward scapular rotation results from 25 degrees elevation of clavicle and 35 degrees elevation at AC.

What is the retraction angle of the clavicle during overhead reaching?

15 degrees.

What is the posterior tilt and external rotation of the scapula during overhead reaching?

20 degrees posterior tilt and 10 degrees external rotation.

What are the proximal and distal insertions of the deltoid?

Proximal: Spine of scapula, acromion, clavicle; Distal: Deltoid tuberosity.

What is the general action of the deltoid?

Abduction.

What are the proximal and distal insertions of the serratus anterior?

Proximal: Ribs 1-9; Distal: Medial border of scapula.

What is the general action of the serratus anterior?

Protraction.

What are the proximal and distal insertions of the supraspinatus?

Proximal: Supraspinous fossa; Distal: Superior facet of greater tuberosity.

What is the general action of the supraspinatus?

Abduction.

What are the proximal and distal insertions of the biceps brachii?

Proximal: Short head - coracoid process, Long head - supraglenoid tubercle; Distal: Radial tuberosity.

What is the general action of the biceps brachii?

Elbow flexion and shoulder flexion.

What are the proximal and distal insertions of the subscapularis?

Proximal: Subscapular fossa; Distal: Lesser tuberosity.

What is the general action of the subscapularis?

Internal rotation.