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Questions and Answers
The scapula performs anterior tilting only at the SC joint.
The scapula performs anterior tilting only at the SC joint.
False
Poor neuromuscular control can lead to excessive anterior tipping of the scapula.
Poor neuromuscular control can lead to excessive anterior tipping of the scapula.
True
The SC joint is a complex articulation involving just the clavicle and the sternum.
The SC joint is a complex articulation involving just the clavicle and the sternum.
False
The scapula is solely attached to the chest by atmospheric pressure.
The scapula is solely attached to the chest by atmospheric pressure.
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The sternal end of the clavicle and the manubrium show considerable contact between their articular surfaces.
The sternal end of the clavicle and the manubrium show considerable contact between their articular surfaces.
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The medial end of the clavicle is usually concave along its longitudinal diameter.
The medial end of the clavicle is usually concave along its longitudinal diameter.
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Scapula stability is achieved through a combination of muscles and joint integrity.
Scapula stability is achieved through a combination of muscles and joint integrity.
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Clavicular movement at the SC joint is independent of scapular motion.
Clavicular movement at the SC joint is independent of scapular motion.
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The head of the humerus faces laterally and inferiorly, forming an approximate 135° angle of inclination with the long axis of the humeral shaft.
The head of the humerus faces laterally and inferiorly, forming an approximate 135° angle of inclination with the long axis of the humeral shaft.
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The humeral head is rotated anteriorly about 30° within the horizontal plane.
The humeral head is rotated anteriorly about 30° within the horizontal plane.
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The clavicle deviates about 20°–30° posterior to the frontal plane.
The clavicle deviates about 20°–30° posterior to the frontal plane.
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The scapula is positioned anteriorly to the frontal plane by approximately 30°–40°.
The scapula is positioned anteriorly to the frontal plane by approximately 30°–40°.
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The medial border of the scapula lies at a distance of 10-12 cm from the interspinous line.
The medial border of the scapula lies at a distance of 10-12 cm from the interspinous line.
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The inferior angle of the scapula corresponds to the 8th rib and lies at a distance of 7 cm from the interspinous line.
The inferior angle of the scapula corresponds to the 8th rib and lies at a distance of 7 cm from the interspinous line.
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The supero-medial angle of the scapula corresponds to the 2nd thoracic spinous process.
The supero-medial angle of the scapula corresponds to the 2nd thoracic spinous process.
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The greater tubercle of the humerus has three distinct facets for muscle attachment.
The greater tubercle of the humerus has three distinct facets for muscle attachment.
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The interclavicular ligament supports the clavicle's superior glide.
The interclavicular ligament supports the clavicle's superior glide.
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The motions of the sternoclavicular joint include elevation and retraction.
The motions of the sternoclavicular joint include elevation and retraction.
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The clavicle can elevate up to 30 degrees at the sternoclavicular joint.
The clavicle can elevate up to 30 degrees at the sternoclavicular joint.
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Depression of the clavicle stretches the interclavicular ligament.
Depression of the clavicle stretches the interclavicular ligament.
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The costoclavicular ligament has no role in stabilizing the clavicle.
The costoclavicular ligament has no role in stabilizing the clavicle.
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Protraction and retraction of the clavicle occur around a horizontal axis of rotation.
Protraction and retraction of the clavicle occur around a horizontal axis of rotation.
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The sternocleidomastoid muscle stabilizes the sternoclavicular joint.
The sternocleidomastoid muscle stabilizes the sternoclavicular joint.
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The clavicle’s concave articular surface slides inferiorly during elevation.
The clavicle’s concave articular surface slides inferiorly during elevation.
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Abducting the shoulder in the pure frontal plane is more natural than abducting in the scapular plane.
Abducting the shoulder in the pure frontal plane is more natural than abducting in the scapular plane.
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External rotation of the humerus is necessary for completing frontal plane abduction.
External rotation of the humerus is necessary for completing frontal plane abduction.
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The humeral head rolls anteriorly while sliding posteriorly during horizontal abduction.
The humeral head rolls anteriorly while sliding posteriorly during horizontal abduction.
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Flexion at the shoulder primarily involves a spinning motion of the humeral head.
Flexion at the shoulder primarily involves a spinning motion of the humeral head.
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Extremes of flexion at the shoulder can lead to posterior translation of the humerus.
Extremes of flexion at the shoulder can lead to posterior translation of the humerus.
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The coracoclavicular ligament provides significant stability to the AC joint and consists of two parts: the anterior and posterior ligaments.
The coracoclavicular ligament provides significant stability to the AC joint and consists of two parts: the anterior and posterior ligaments.
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Internal and external rotation from the anatomical position are associated with a roll-and-slide motion.
Internal and external rotation from the anatomical position are associated with a roll-and-slide motion.
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The trapezoid ligament extends almost vertically and provides resistance to posterior forces applied to the clavicle.
The trapezoid ligament extends almost vertically and provides resistance to posterior forces applied to the clavicle.
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The AC joint allows for more extensive motions compared to the SC joint.
The AC joint allows for more extensive motions compared to the SC joint.
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Anterior translation of the humerus can be provoked by abduction.
Anterior translation of the humerus can be provoked by abduction.
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Rotation of the GH joint from about 90° of abduction primarily utilizes a spinning motion.
Rotation of the GH joint from about 90° of abduction primarily utilizes a spinning motion.
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The coracoclavicular ligament plays a critical role in coupling the posterior rotation of the clavicle to scapula rotation.
The coracoclavicular ligament plays a critical role in coupling the posterior rotation of the clavicle to scapula rotation.
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The CCL is stronger and absorbs more energy than most other ligaments of the shoulder.
The CCL is stronger and absorbs more energy than most other ligaments of the shoulder.
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The AC joint is primarily responsible for limiting upward rotation of the scapula.
The AC joint is primarily responsible for limiting upward rotation of the scapula.
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The superior capsular ligament is reinforced through attachments from the deltoid and trapezius muscles.
The superior capsular ligament is reinforced through attachments from the deltoid and trapezius muscles.
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Medial displacement of the scapula’s acromion on the clavicle is facilitated by the strength of the conoid ligament.
Medial displacement of the scapula’s acromion on the clavicle is facilitated by the strength of the conoid ligament.
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Study Notes
Osteologic Features of the Humerus
- The head of the humerus faces medially and superiorly, forming a 135° angle with the humeral shaft.
- The humeral head is retroverted (rotated posteriorly) about 30° relative to a M-L axis through the elbow.
Shoulder Girdle Angulations
- The clavicle deviates about 20°-30° posterior to the frontal plane.
- The scapula deviates about 30°–40° anterior to the frontal plane.
- The angle between the scapula and clavicle is approximately 60°.
Scapula Position on the Chest Wall
- The scapula extends from the 2nd to the 7th rib.
- Its supero-medial angle aligns with the 1st thoracic spinous process or the 2nd rib.
- The medial tip of its spine aligns with the 3rd spinous process.
- The medial border is 5-6 cm from the interspinous line.
- The inferior angle is 7 cm from the interspinous line and aligns with the 7th rib.
Motions of the Scapula
- The scapula moves on the chest wall primarily through adjustments at the acromioclavicular joint.
- Anterior tilting/tipping and posterior tilting/tipping describe the rotation of the glenoid fossa.
- Anterior/posterior tipping at the AC joint normally occurs with anterior/posterior rotation of the clavicle at the SC joint.
- Isolated anterior tipping at the AC joint leads to prominence of the inferior angle of the scapula.
Scapula Stability on the Chest Wall
- The scapula is stabilized by atmospheric pressure.
- The acromioclavicular and sternoclavicular joints play a role in overall stability.
- Muscles attaching the scapula to the chest also contribute to its stability.
Sternoclavicular (SC) Joint
- It is located at the medial end of the clavicle, the clavicular facet on the sternum, and the superior border of the cartilage of the first rib.
- It connects the appendicular skeleton to the axial skeleton.
- It allows considerable range of movement despite being firmly attached.
- The articular surface is an irregular saddle shape, with clavicle convex along its longitudinal diameter and slightly concave transversely.
Sternoclavicular Joint Stability – Capsule and Ligaments
- The interclavicular ligament prevents excessive depression of the distal clavicle.
- This prevents compression of the brachial plexus and subclavian artery.
- The interclavicular ligament supports the weight of the upper extremity and external loads during clavicle depression.
Tissues That Stabilize the Sternoclavicular Joint
- Anterior and posterior sternoclavicular joint ligaments
- Interclavicular ligament
- Costoclavicular ligament
- Articular disc
- Sternocleidomastoid, sternothyroid, sternohyoid, and subclavius muscles
Sternoclavicular Joint Mobility
- The SC joint moves in elevation (35–45 °) and depression (10-15 °) in a near frontal plane.
- Elevation involves the convex articular surface of the clavicle rolling superiorly and sliding inferiorly.
- Depression involves the clavicle rolling inferiorly and sliding superiorly.
Sternoclavicular Joint Mobility
- Protraction and retraction (15-30°) occur in a near horizontal plane.
- Retraction involves the concave articular surface of the clavicle rolling and sliding posteriorly.
Acromioclavicular Joint
- The AC joint is stabilized by a capsule reinforced by superior and inferior ligaments.
- Attachments from deltoid and trapezius muscles reinforce the superior capsular ligament.
- The coracoclavicular ligament (CCL) provides stability and consists of two parts:
- Trapezoid (laterally): oblique superior-lateral direction, resists posterior translatory forces.
- Conoid ligament (medially): almost vertical, restrains motion in superior and inferior directions.
Acromioclavicular Joint - Stability
- The CCL is stronger than most other shoulder ligaments.
- It provides horizontal and superior stability and prevents superior dislocation of the clavicle.
- The CCL limits upward rotation of the scapula at the AC joint.
- The coracoclavicular ligament (trapezoid portion) prevents medial displacement of the scapula's acromion.
- The CCL couples posterior rotation of the clavicle with scapula rotation during upper limb elevation.
Acromioclavicular Joint - Mobility
- The SC joint allows extensive motion of the clavicle, guiding scapula movement.
- The AC joint facilitates more subtle movements between the scapula and clavicle.
Mobility - Arthrokinematics
- Abduction in the scapular plane (30° anterior to the frontal plane) is more natural than pure frontal plane abduction.
- This avoids impingement due to the greater tubercle placement under the coracoacromial arch.
- It allows the retroverted humeral head to be oriented directly into the glenoid fossa.
- Completion of frontal plane abduction requires external rotation of the humerus to clear the greater tubercle.
Mobility - Arthrokinematics
- Horizontal abduction involves humeral head rolling posteriorly and sliding anteriorly.
- Horizontal adduction involves the reverse motion.
Mobility - Arthrokinematics
- Flexion primarily involves a spinning motion of the humeral head.
- Extension involves the reverse motion.
- External rotation involves humeral head rolling posteriorly and sliding anteriorly.
- Internal rotation is similar, but with reversed directions.
- From anatomic position, internal and external rotation involve roll-and-slide.
- Rotation from 90° of abduction mainly involves spinning.
Mobility - Arthrokinematics
- Anterior translation of the humerus is provoked by:
- Abduction
- External rotation
- Horizontal abduction
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Description
This quiz explores the osteologic features of the humerus and the anatomical relationships of the shoulder girdle. It covers the angulations of the clavicle, positions of the scapula on the chest wall, and the motions involved. Test your knowledge on these critical aspects of human anatomy.
