The shoulder and arm Flashcards
What is the difference between the arm and the forearm
Arm- part between shoulder and elbow (often called upper arm in clinical practice)
Forearm- between the elbow and the wrist
What are the 3 key bones in the shoulder and arm region
The Scapula
The Clavicle
The Humerus
Summarise the key features of the scapula
The scapula is a large, flat triangular bone with:
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three angles (lateral, superior, and inferior),
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three borders (superior, lateral, and medial),
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two surfaces (costal and posterior), and
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three processes (acromion, spine, and coracoid process)
What does the spine of the scapula divide the posterior surface of the scapula into
A prominent spine subdivides the posterior surface of the scapula into a small, superior supraspinous fossa and a much larger, inferior infraspinous fossa
What is the lateral angle of the scapula marked by
The lateral angle of the scapula is marked by a shallow, somewhat comma-shaped glenoid cavity, which articulates with the head of the humerus to form the glenohumeral joint
Describe the greater scapular notch
The region between the lateral angle of the scapula and the attachment of the spine to the posterior surface of the scapula is the greater scapular notch (spinoglenoid notch)
Describe the costal surface of the scapula
Unlike the posterior surface, the costal surface of the scapula is unremarkable, being characterized by a shallow concave subscapular fossa over much of its extent (Fig. 7.21B). The costal surface and margins provide for muscle attachment, and the costal surface, together with its related muscle (subscapularis), moves freely over the underlying thoracic wall.
Describe the acromian and coracoid processes of the scapula
The acromion, which is an anterolateral projection of the spine, arches over the glenohumeral joint and articulates, via a small oval facet on its distal end, with the clavicle.
the coracoid process, a hook-like structure that projects anterolaterally and is positioned directly inferior to the lateral part of the clavicle (on its superior border)
Describe the suprascapular notch
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the small but distinct suprascapular notch, which lies immediately medial to the root of the coracoid process.
Compare the lateral border of the scapula to the medial border
The lateral border of the scapula is strong and thick for muscle attachment, whereas the medial border and much of the superior border is thin and sharp
Describe the tubercles of the scapula
A less distinct supraglenoid tubercle is located superior to the glenoid cavity and is the site of attachment for the long head of the biceps brachii muscle.
A large triangular-shaped roughening (the infraglenoid tubercle) inferior to the glenoid cavity is the site of attachment for the long head of the triceps brachii muscle.
Deltoid tubercle on spine of the scapula
Summarise the clavicle
The clavicle is the only bony attachment between the trunk and the upper limb. It is palpable along its entire length and has a gentle S-shaped contour, with the forward-facing convex part medial and the forward-facing concave part lateral. The acromial (lateral) end of the clavicle is flat, whereas the sternal (medial) end is more robust and somewhat quadrangular in shape
Compare the acromial end of the clavicle to the sternal end
The acromial end of the clavicle has a small oval facet on its surface for articulation with a similar facet on the medial surface of the acromion of the scapula.
The sternal end has a much larger facet for articulation mainly with the manubrium of the sternum, and to a lesser extent, with the first costal cartilage.
Describe the inferior surface of the lateral 1/3rd of the clavicle
Conoid tubercle (distinct tuberosity) Trapezoid line (lateral roughening) They are the point of attachment of the conoid ligament and trapezoid ligament (both part of the coracoclavicular ligament) The coracoclavicular ligament is responsible for vertically attaching the scapula to the clavicle.
What are the surfaces and margins of the clavicle roughened by
In addition, the surfaces and margins of the clavicle are roughened by the attachment of muscles that connect the clavicle to the thorax, neck, and upper limb. The superior surface is smoother than the inferior surface.
What is important to remember about the clavicle
§ First long bone to ossify in the body (5th week) and does so by intramembranous ossification rather than endochondral which is most common to long bones.
§ Orientate via the “flat” lateral end at the acromion of the scapula and the circular sternal end at the sternum/1st CC (superior smooth).
§ Identify – conoid tubercle, trapezoid line, subclavian and costo-clavicular ligament groove (sternal end of posterior surface- can see a groove)
Which structures are at risk if the fractured clavicle is displaced
Structures that may be injured are the subclavian vessels, axillary artery, elements of the brachial plexus, and internal jugular vein, and the lung, causing a pneumothorax.
How are fractures of the clavicle commonly classified
Fractures of the clavicle are classified on which third is fractured. The middle one-third of the clavicle is most commonly fractured (80%), with lateral one-third fractures accounting for 15%, and medial one-third fractures being the least frequent (5%).
What is the key role of the clavicle and what can happen in a fracture
The clavicle serves as an osseous strut that braces the shoulder against the sternum to force the upper extremity away from the trunk so that movement of the upper limb clears the trunk. As an osseous strut, the clavicle is buttressed by strong ligaments that connect it horizontally and vertically to adjacent structures.
In this clinical case, the fracture occurred medial to the coracoclavicular ligament (see Figure 94). Consequently, the weight of the upper limb caused the scapula and its attachment to the distal clavicle to move downward and the muscles bridging the glenohumeral joint pulled the upper limb medially.
Preservation of the arterial supply to the clavicle is essential to the repair process. What is the arterial supply to the clavicle?
The nutrient artery to the clavicle is a branch of the suprascapular artery. The nutrient foramen is located in the lateral end of the subclavian groove, which serves as the insertion for the subclavius muscle.
What does the proximal end of the humerus consist of
The proximal end of the humerus consists of the head, the anatomical neck, the greater and lesser tubercles, the surgical neck, and the superior half of the shaft of the humerus
Describe the head of the proximal humerus
The head is half-spherical in shape and projects medially and somewhat superiorly to articulate with the much smaller glenoid cavity of the scapula.
Describe the anatomical neck of the proximal humerus
The anatomical neck is very short and is formed by a narrow constriction immediately distal to the head. It lies between the head and the greater and lesser tubercles laterally, and between the head and the shaft more medially.
Describe the surgical neck and its clinical importance
One of the most important features of the proximal end of the humerus is the surgical neck (Fig. 7.22). This region is oriented in the horizontal plane between the expanded proximal part of the humerus (head, anatomical neck, and tubercles) and the narrower shaft. The axillary nerve and the posterior circumflex humeral artery, which pass into the deltoid region from the axilla, do so immediately posterior to the surgical neck. Because the surgical neck is weaker than more proximal regions of the bone, it is one of the sites where the humerus commonly fractures. The associated nerve (axillary) and artery (posterior circumflex humeral) can be damaged by fractures in this region.
Fractures occur here more commonly than the anatomical neck
Summarise fractures of the proximal humerus
It is extremely rare for fractures to occur across the anatomical neck of the humerus because the obliquity of such a fracture would have to traverse the thickest region of bone. Typically fractures occur around the surgical neck of the humerus. Although the axillary nerve and posterior circumflex humeral artery may be damaged with this type of fracture, this rarely happens. It is important that the axillary nerve is tested before relocation to be sure that the injury has not damaged the nerve and that the treatment itself does not cause a neurological deficit.
Summarise the tubercles of the humerus
The greater and lesser tubercles are prominent landmarks on the proximal end of the humerus and serve as attachment sites for the four rotator cuff muscles of the glenohumeral joint.
Describe the greater tubercle
The greater tubercle is lateral in position. Its superior surface and posterior surface are marked by three large smooth facets for muscle tendon attachments:
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The superior facet is for attachment of the supraspinatus muscle.
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The middle facet is for attachment of the infraspinatus.
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The inferior facet is for attachment of the teres minor.
Describe the lesser tubercle
The lesser tubercle is anterior in position and its surface is marked by a large smooth impression for attachment of the subscapularis muscle.
Describe the intertubecular sulcus
A deep intertubercular sulcus (bicipital groove) separates the lesser and greater tubercles and continues inferiorly onto the proximal shaft of the humerus (Fig. 7.22). The tendon of the long head of the biceps brachii passes through this sulcus.
Describe the roughenings for attachments of muscles onto the intertubercular sulcus
Roughenings on the lateral and medial lips and on the floor of the intertubercular sulcus mark sites for the attachment of the pectoralis major, teres major, and latissimus dorsi muscles, respectively.
Describe the deltoid tuberosity of the proximal humerus
The lateral lip of the intertubercular sulcus is continuous inferiorly with a large V-shaped deltoid tuberosity on the lateral surface of the humerus midway along its length (Fig. 7.22), which is where the deltoid muscle inserts onto the humerus.
In approximately the same position, but on the medial surface of the bone, there is a thin vertical roughening for attachment of the coracobrachialis muscle.
Summarise the shaft of the humerus
In cross section, the shaft of the humerus is somewhat triangular with:
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anterior, lateral, and medial borders, and
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anterolateral, anteromedial, and posterior surfaces
Describe the posterior surface of the humerus
The posterior surface of the humerus is marked on its superior aspect by a linear roughening for the attachment of the lateral head of the triceps brachii muscle, beginning just inferior to the surgical neck and passing diagonally across the bone to the deltoid tuberosity.
Describe the radial groove
The middle part of the posterior surface and adjacent part of the anterolateral surface are marked by the shallow radial groove, which passes diagonally down the bone and parallel to the sloping posterior margin of the deltoid tuberosity. The radial nerve and the profunda brachii artery lie in this groove.
Which structure is found in the middle of the shaft
Approximately in the middle of the shaft, the medial border is marked by thin elongate roughening for the attachment of the coracobrachialis muscle.
Describe the lateral and medial intermuscular septa
Intermuscular septa, which separate the anterior compartment from the posterior compartment, attach to the medial and lateral borders
Distally, what happens to the humerus
Distally, the bone becomes flattened, and these borders expand as the lateral supraepicondylar ridge (lateral supracondylar ridge) and the medial supraepicondylar ridge (medial supracondylar ridge). The lateral supraepicondylar ridge is more pronounced than the medial ridge and is roughened for the attachment of muscles found in the posterior compartment of the forearm.
The distal end of the humerus, which is flattened in the anteroposterior plane, bears a condyle, two epicondyles, and three fossae, as follows
Compare the capitulum to the trochlea
The two articular parts of the condyle
The capitulum articulates with the radius of the forearm. Lateral in position and hemispherical in shape, it projects anteriorly and somewhat inferiorly and is not visible when the humerus is viewed from the posterior aspect.
The trochlea articulates with the ulna of the forearm. It is pulley shaped and lies medial to the capitulum. Its medial edge is more pronounced than its lateral edge and, unlike the capitulum, it extends onto the posterior surface of the bone.
Describe the medial epicondyle
The medial epicondyle, a large bony protuberance, is the major palpable landmark on the medial side of the elbow, and projects medially from the distal end of the humerus. On its surface, it bears a large oval impression for the attachment of muscles in the anterior compartment of the forearm. The ulnar nerve passes from the arm into the forearm around the posterior surface of the medial epicondyle and can be palpated against the bone in this location.
Describe the lateral epicondyle
The lateral epicondyle is much less pronounced than the medial epicondyle. It is lateral to the capitulum and has a large irregular impression for the attachment of muscles in the posterior compartment of the forearm.
Describe the fossae of the distal humerus
The radial fossa is the least distinct of the fossae and occurs immediately superior to the capitulum on the anterior surface of the humerus.
The coronoid fossa is adjacent to the radial fossa and is superior to the trochlea.
The largest of the fossae, the olecranon fossa, occurs immediately superior to the trochlea on the posterior surface of the distal end of the humerus.
These three fossae accommodate projections from the bones in the forearm during movements of the elbow joint.
What is the difference between a tubercle and a tuberosity
Tubercle- round
Tuberosity- irregular lump
Ultimately, what is the main purpose of the upper limbs
Musculoskeletal
To get your hand where you want it to be to perform a task
What is important to remember about the nomenclature of the muscle attachments in the upper limb
Old-fashioned terminology for muscle attachments is:
origins and insertions. Now considered inaccurate.
For Limbs, the correct terminology is:
proximal attachment and distal attachment. The proximal attachment is at, or closer to, the trunk.
What are the muscular compartments for the shoulder and arm region
Anterior pectoral girdle muscles Posterior pectoral girdle muscles Intrinsic shoulder muscles Anterior compartment of the upper arm Posterior compartment of the upper arm
List the anterior pectoral girdle muscles
Pectoralis major
Pectoralis minor
Subclavius
Serratus anterior* (runs between anterior and posterior pectoral girdle)
What are the proximal and medial attachments of the pectoralis major muscle
Proximal: Medial half of clavicle and anterior surface of sternum, first seven costal cartilages, aponeurosis of external oblique
Distal: Lateral lip of intertubercular sulcus of humerus
Describe the actions of the pectoralis major and its innervation
Flexion, adduction, and medial rotation of arm at glenohumeral joint; clavicular head—flexion of extended arm; sternocostal head—extension of flexed arm
Medial and lateral pectoral nerves; clavicular head (C5, C6); sternocostal head (C6, C7, C8, T1)
Describe the features of the pectoralis major muscle
The pectoralis major muscle is the largest and most superficial of the pectoral region muscles. It directly underlies the breast and is separated from it by deep fascia and the loose connective tissue of the retromammary space.
3 parts:
clavicular head
sternal head
abdominal part
Describe the proximal and distal attachments of the pectoralis minor muscle
Proximal: Anterior surfaces of the third, fourth, and fifth ribs, and deep fascia overlying the related intercostal spaces (fans out to have digital- finger like parts)
Distal: Coracoid process of scapula (medial border and upper surface)
Describe the innervation and actions of the pectoralis minor muscle
Depresses tip of shoulder; protracts scapula, pulls scapula down
Medial pectoral nerve (C5, C6, C7, C8, T1)
What are the proximal and distal attachments for the subclavius
Proximal- Rib I at junction between rib and costal cartilage
Distal- Groove on inferior surface of middle third of clavicle
Describe the innervation and function of the subclavius
Pulls clavicle medially to stabilize sternoclavicular joint; depresses tip of shoulder
Nerve to subclavius (subclavian nerve)- C5,C6- small branch from superior trunk of brachial plexus
Where do the lateral and medial pectoral nerves originate from
The brachial plexus in the axilla
Describe the proximal and medial attachments of the serratus anterior
Proximal: Lateral surfaces of upper 8–9 ribs and deep fascia overlying the related intercostal spaces
Distal: Costal surface of medial border of scapula
Describe the innervation and actions of the serratus anterior
Protraction and rotation of the scapula; keeps medial border and inferior angle of scapula opposed to thoracic wall
Long thoracic nerve (C5, C6, C7)
Describe winging of the scapula
Because the long thoracic nerve passes down the lateral thoracic wall on the external surface of the serratus anterior muscle, just deep to skin and subcutaneous fascia, it is vulnerable to damage. Loss of function of this muscle causes the medial border, and particularly the inferior angle, of the scapula to elevate away from the thoracic wall, resulting in characteristic “winging” of the scapula, on pushing forward with the arm. Furthermore, normal elevation at the arm is no longer possible.
List the posterior pectoral girdle muscles
Trapezius, Latissimus dorsi, Levator scapulae, the Rhomboids
What are the proximal and distal attachments of the trapezius
Proximal- Superior nuchal line, external occipital protuberance, medial margin of the ligamentum nuchae, spinous processes of CVII to TXII and the related supraspinous ligaments
Distal- Superior edge of the crest of the spine of the scapula, acromion, posterior border of lateral one-third of clavicle
Describe the actions and innervation of the trapezius muscle
Innervation- Motor spinal part of accessory nerve (XI). Sensory (proprioception) anterior rami of C3 and C4
Actions- Powerful elevator of the scapula; rotates the scapula during abduction of humerus above horizontal; middle fibers retract scapula; lower fibers depress scapula
The accessory nerve can be evaluated by testing the function of the trapezius muscle. This is most easily done by asking patients to shrug their shoulders against resistance.
Describe the different parts of the trapezius muscle
Inferior fibres- ascending(C7-T12)
Middle fibres- horizontal
Superior fibres- descending.- nuchal ligament (C1-C6) AND SKULL
What is important to remember about the scapula
Hub for muscles to attach- often there to stabilise it and hold it in position
Describe the proximal and distal attachments of the latissimus dorsi
Distal- Floor of intertubercular sulcus of humerus
Proximal- Spinous processes of TVII to LV and sacrum, iliac crest, ribs X to XII (attached to iliac crest and sacrum via thoracolumbar fascia)
Thoracolumbar fascia and posterior 1/3 of the iliac crest
Floor of the intertubercular sulcus
Broad attachment proximally- fibres converge as a tendon to its distal attachment on the intertubecular groove.
Describe the innervation and actions of the latissimus dorsi
Innervation- Thoracodorsal nerve (C6 to C8)
Actions- Extends, adducts, and medially rotates humerus (at the gleno-humeral joint)
pulls the body up to the arms during climbing. Also important in rowing.
Describe the proximal and distal attachments of the rhomboid minor
Proximal- Lower end of ligamentum nuchae and spinous processes of CVII and TI vertebrae
Distal- Posterior surface of medial border of scapula at the root of the spine of the scapula
Describe the innervation and actions of the rhomboid minor
Innervation- Dorsal scapular nerve (C4, C5)
Actions- Elevates and retracts the scapula
Describe the proximal and distal attachments of the rhomboid major
Proximal- Spinous processes of TII–TV vertebrae and intervening supraspinous ligaments
Distal- Posterior surface of medial border of scapula from the root of the spine of the scapula to the inferior angle
Describe the innervation and actions of the rhomboid major muscle
Innervation- Dorsal scapular nerve (C4, C5)
Actions- Elevates and retracts scapula
Same as minor
Forms parallelogram
Describe the proximal and distal attachments of the levator scapulae muscle
Proximal- Transverse processes of CI and CII vertebrae and posterior tubercles of transverse processes of CIII and CIV vertebrae
Distal- Posterior surface of medial border of scapula from superior angle to root of spine of the scapula
Describe the innervations and actions of the levator scapulae muscle
Innervation- Branches directly from anterior rami of C3 and C4 spinal nerves and by branches (C5) from the dorsal scapular nerve
Actions- Elevates and rotates the scapula
Which muscles make up the intrinsic shoulder compartment
Rotator cuff muscles (supraspinatus, infraspinatus, teres minor and subscapularis)
Teres major
Deltoid
Describe the proximal and distal attachments of the deltoid
Proximal- Inferior edge of the crest of the spine of the scapula, lateral margin of the acromion, anterior border of lateral one-third of clavicle
Distal- Deltoid tuberosity of humerus
Describe the innervation and actions of the deltoid
Innervation- Axillary nerve (C5, C6)
The axillary nerve and associated blood vessels (the posterior circumflex humeral artery and vein) enter the deltoid by passing posteriorly around the surgical neck of the humerus.
Actions- Major abductor of arm (abducts arm beyond initial 15° done by supraspinatus); clavicular fibers assist in flexing the arm; posterior fibers assist in extending the arm (at GHJ)
Describe the different parts of the deltoid muscle
Clavicular part (anterior) Spinal part (posterior) Middle part
The deltoid covers the shoulder joint- giving it a rounded appearance- broad attachment
Fibres can act separately to aid a particular movement- but most act together to contribute the movements of the shoulder joint.
Summarise the rotator cuff muscle
Rotator cuff group acts to fix the head of humerus in the glenoid fossa.
Supraspinatus important in initiating abduction of arm for first 15°, then deltoid takes over.
Describe the proximal and distal attachments of the supraspinatous muscle
Proximal- Medial two-thirds of the supraspinous fossa of the scapula and the deep fascia that covers the muscle
Distal- Most superior facet on the greater tubercle of the humerus
Describe the innervation and actions of the supraspinatous muscle
innervation- Suprascapular nerve (C5, C6)
Actions- Rotator cuff muscle; initiation of abduction of arm to 15° at glenohumeral joint
Describe the proximal and distal attachments of the infraspinatous muscle
Proximal- Medial two-thirds of the infraspinous fossa of the scapula and the deep fascia that covers the muscle
Distal- Middle facet on posterior surface of the greater tubercle of the humerus
Describe the innervation and actions of the infraspinatous muscle
Innervation- Suprascapular nerve (C5, C6)
Actions- Rotator cuff muscle; lateral rotation of arm at the glenohumeral joint
Describe the proximal and distal attachments of the teres minor
proximal- Upper two-thirds of a flattened strip of bone on the posterior surface of the scapula immediately adjacent to the lateral border of the scapula
Distal- Inferior facet on the posterior surface of the greater tubercle of the humerus
Describe the innervation and actions of the teres minor
Innervation- Axillary nerve (C5, C6)
Action- Rotator cuff muscle; lateral rotation of arm at the glenohumeral joint
Describe the proximal and distal attachments of the subscapularis muscle
Proximal- Medial two-thirds of subscapular fossa
Distal- Lesser tubercle of humerus
Describe the innervation and actions of the subscapularis muscle
Innervation- Upper and lower subscapular nerves (C5, C6, (C7))
Action- Rotator cuff muscle; medial rotation of the arm at the glenohumeral joint
Describe the proximal and distal attachments of the teres major muscle
Proximal- Elongate oval area on the posterior surface of the inferior angle of the scapula
Distal- Medial lip of the intertubercular sulcus on the anterior surface of the humerus
Describe the innervation and actions of the teres major muscle
Innervation- Lower subscapular nerve (C5, C6, C7)
Actions- Medial rotation and extension of the arm at the glenohumeral joint
Which muscles make up the anterior compartment of the arm and which nerve innervates them?
Biceps brachii
Brachialis
Coracobrachialis
Innervated by: musculocutaneous nerv
Describe the proximal and distal attachments of the biceps brachii
proximal- Long head—supraglenoid tubercle of scapula (goes through intertubecular groove held in place by transverse humeral ligament); short head—apex of coracoid process
Distal- Radial tuberosity
The long and short heads converge to form a single tendon, which inserts onto the radial tuberosity.
As the tendon enters the forearm, a flat sheet of connective tissue (the bicipital aponeurosis) fans out from the medial side of the tendon to blend with deep fascia covering the anterior compartment of the forearm.
Describe the innervation and actions of the biceps brachii
Innervation- Musculocutaneous nerve (C5, C6)
Actions- Powerful flexor of the forearm at the elbow joint and supinator of the forearm; accessory flexor of the arm at the glenohumeral joint
Describe the proximal and distal attachments of the coracobrachalis muscle
Proximal -Apex of coracoid process
Distal- Linear roughening on midshaft of humerus on medial side
Describe the innervation and actions of the coracobrachialis muscle
Innervation- Musculocutaneous nerve (C5, C6, C7)
Action- Flexor of the arm at the glenohumeral joint
Describe the proximal and distal attachments of the brachialis muscle
Proximal- Anterior aspect of humerus (medial and lateral surfaces) and adjacent intermuscular septae- shaft of humerus
Distal- Tuberosity of the ulna (coranoid process)
Describe the innervation and actions of the brachialis muscle
Innervation- Musculocutaneous nerve (C5, C6); small contribution by the radial nerve (C7) to lateral part of muscle
Actions- Powerful flexor of the forearm at the elbow joint
List the muscles of the posterior arm compartment
Triceps
Anconeus
Describe the proximal and distal attachments of the triceps brachii muscle
proximal- Long head—infraglenoid tubercle of scapula; medial head—posterior surface of humerus; lateral head—posterior surface of humerus
Distal- The three heads converge to form a large tendon, which inserts on the superior surface of the olecranon of the ulna.
Describe the innervation and actions of the triceps brachii muscle
Innervation- Radial nerve (C6, C7, C8)
Innervation of the triceps brachii is by branches of the radial nerve. A tap on the tendon of the triceps brachii tests predominantly spinal cord segment C7
Actions- Extension of the forearm at the elbow joint; long head can also extend and adduct the arm at the shoulder joint
Describe the proximal and distal attachments of the anconeus muscle
Proximal- Lateral epicondyle of humerus
Distal- Olecranon and proximal posterior surface (shaft) of ulna
Describe the innervation and actions of the anconeus muscle
Innervation- Radial nerve (C6, C7, C8) (via branch to medial head of triceps brachii)
Actions- Abduction of the ulna in pronation; accessory extensor of the elbow joint (stabilises the joint in pronation and supination_
What is important to remember about the rotator cuff muscles
All head to the head of the humerus and cross the shoulder joint to attach around the head of the humerus
Main activity is to hold head of humerus into the glenoid cavity- although each muscle can act individually.
