Anatomy: Upper Limb Flashcards
(104 cards)
1
Q
What is the deltoid muscle and what are its three parts?
A
Deltoid - gives the shoulder its rounded contour. There are three parts to the deltoid muscle: anterior, middle and posterior. The anterior part flexes the shoulder, the middle part abducts it (after the first 15 degrees), and the posterior part extends it.
2
Q
What nerve is the deltoid innervated by?
A
Innervation: axillary nerve (C5, 6).
3
Q
What is the pectoralis major muscle?
A
Pectoralis major - originates from the sternum and clavicle, and inserts on the lateral lip of the bicipital groove. It is a powerful adductor of the shoulder, as well as contributing to medial rotation and flexion.
4
Q
What nerve is the pectoralis major innervated by?
A
Innervation: medial and lateral pectoral nerves.
5
Q
Where is the trapezius muscle and what does it do?
A
The trapezius muscle is found posteriorly in the neck and back, but acts primarily on the shoulder joint.
The descending fibres of Trapezius attach to the spine of the scapula and acromion. This portion of the muscle is responsible for elevating the scapula (shrugging your shoulders).
6
Q
What nerve innervates the trapezius muscle?
A
Trapezius has an unusual nerve supply, cranial nerve XI, the accessory nerve.
7
Q
Which muscle adducts the shoulder?
A
Pectoralis major
8
Q
Which muscle abducts the shoulder?
A
Deltoid
9
Q
What is the latissimus dorsi muscle?
A
Latissimus Dorsi is a large muscle found in the back. It wraps around the trunk laterally to insert on to the anterior aspect of the humerus.
If the trunk is fixed and the upper limb is mobile it acts to adduct, extend and medially rotate the arm.
If the arms are in a fixed position (such as holding on to a bar above your head) the latissimus dorsi acts to elevate the trunk towards the arms. It is an important muscle for climbing.
10
Q
Which nerve innervates the latissimus dorsi?
A
Innervation: Thoracodorsal nerve
11
Q
What is the serratus anterior and what is it responsible for?
A
Serratus anterior originates on the medial border of the scapula and runs deep to the scapula around the thorax to insert on to the ribs.
It is responsible for protrusion of the scapula. Tonic contraction of serratus anterior keeps the scapula flat on the back. Weakness of this muscle, or damage to its nerve supply can result in winging of the scapula.
12
Q
Which nerve innervates the serratus anterior?
A
Innervation: Long thoracic nerve
13
Q
What are the four rotator cuff muscles?
A
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
14
Q
What is the supraspinatus and how is it innervated?
A
Lies in the supraspinous fossa of the scapula. Its tendon passes under the acromion to insert onto the greater tuberosity of the humerus superiorly. Responsible for the first 10-15 degrees of shoulder abduction before the deltoid takes over.
Innervation: suprascapular nerve (C5, 6).
15
Q
What is the infraspinatus and how is it innervated?
A
Lies in the infraspinous fossa of the scapula. Inserts onto the greater tuberosity of the humerus. Laterally rotates the shoulder. Innervation: suprascapular nerve (C5, 6).
16
Q
What is the teres minor and how is it innervated?
A
IS
Originates from the lateral margin of the scapula inferiorly and inserts onto the greater tuberosity of humerus. Laterally rotates the shoulder. Innervation: axillary nerve (C5, 6).
17
Q
What is the subscapularis and how is it innervated?
A
The only rotator cuff muscle to originate on the anterior surface of the scapula. Inserts onto the lesser tuberosity of the humerus. Medially rotates the shoulder. Innervation: upper and lower subscapular nerves (C5, 6).
18
Q
What is the acromion?
A
From the Greek: akros, meaning highest, and ōmos, meaning shoulder, the acromion is the highest point of the shoulder (like the Acropolis is the highest point in Athens). It articulates with the clavicle at the acromioclavicular joint to link the bones of the shoulder girdle.
19
Q
What is the spine of the scapula?
A
The spine of the scapula is found on its posterior surface. Above it lies the supraspinous fossa, in which supraspinatus sits, and below it lies the infraspinous fossa, in which infraspinatus sits.
20
Q
What is the coracoid process?
A
Named after its resemblance to a crow’s beak, this is the most anterior projection of the scapula. It serves as an attachment point for three muscles: pectoralis minor, coracobrachialis and short head of biceps brachii.
21
Q
What is the glenoid fossa?
A
This is the socket for the ball and socket joint of the shoulder. It articulates with the humeral head (the ball). Note that it is a very shallow socket, so it is not very stable. It is reinforced by glenoid labrum (a cartilagenous ring) and the humerus is kept in place by the rotator cuff muscles.
22
Q
What is the lateral border of the scapula?
A
The scapula is described as having superior, inferior, medial and lateral borders. Different muscles attach to to different parts.
23
Q
What is the serratus anterior?
A
This muscle is serratus anterior. This muscle has a strange course. It originates on the medial border of the scapula and runs deep to the scapula (and subscapularis). it wraps around the thorax and inserts on to the ribs anteriorly.
The anterior serrated edge gives the muscle its name.
24
Q
What is the teres major?
A
This is not a rotator cuff muscle. It sits inferior to teres minor and acts as a medial rotator and extensor of the shoulder.
25
Which muscles have the primary action of adduction?
Latissimus dorsi
Teres major
Pectoralis major
26
Which muscles have the primary action of abduction?
Supraspinatus
| Deltoid
27
Which muscles have the primary action of medial rotation?
Subscapularis
28
Which muscles have the primary action of lateral rotation?
Teres minor
| Infraspinatus
29
Which of these is not a function of the rotator cuff muscles?
Adduction of shoulder
The rotator cuff muscles have a dual role in stabilising the glenohumeral joint (E) and movement of the shoulder. Of the four rotator cuff muscles, supraspinatus is responsible for abduction (D), infraspinatus and teres minor for lateral rotation (A) and subscapularis for medial rotation (B). None of them brings about adduction of the shoulder.
30
In a proximal right humerus fracture, what muscle could pull on the distal fragment and cause a deformity?
The powerful adductors of the upper limb, particularly pecotralis major, but also latissimus dorsi, will be pulling the distal fragment inwards. There may also be some medial rotation for the same reason. This is what caused the deformity of Marie's arm noted on examination.
31
In a proximal right humerus fracture, what nerve might be damaged?
The axillary nerve winds posteriorly around the surgical neck of the humerus to supply the deltoid and teres minor and sensation to the skin over the inferior part of the deltoid. The numbness in this area detected on examination of Marie suggests that the nerve has been damaged - a common complication of this type of fracture.
32
Which features normally help to make the shoulder joint more stable?
Glenoid labrum
Rotator cuff
The shoulder is the most mobile joint in the body - but with great mobility comes great instability. The combination of a relatively large humeral head to a small, shallow glenoid fossa make the joint vulnerable to dislocation. Glenoid labrum and the rotator cuff help to provide reinforcement. Marie's complex fracture has fragmented the humeral head and disrupted the attachment sithttps://qmplus.qmul.ac.uk/pluginfile.php/2485703/mod_scorm/content/1/scormcontent/assets/7Ki0ZPWUjbQjoMSP_MoWn0iumeuperlgC.jpges of the rotator, so even after repair this joint would be unstable; therefore, reverse shoulder replacement is the best option.
33
What are the five terminal branches of the brachial plexus?
The 5 terminal branches of the brachial plexus are the musculocutaneous, median, ulnar, axillary, and radial nerves.
34
Where do the divisions of the brachial plexus pass under?
The clavicle
35
What are the roots, motor and sensory location of the musculocutaneous nerve?
Roots: C5, C6, C7
Motor: Elbow flexors
Sensory: Lateral forearm
36
What are the roots, motor and sensory location of the axillary nerve?
Roots: C5, C6
Motor: Deltoid, teres minor
Sensory: Superolateral arm
37
What are the roots, motor and sensory location of the radial nerve?
Roots: (C5), C6, C7, C8, (T1)
Motor: Extensors of elbow, wrist, digits
Sensory: Dorsal surface of lateral hand and lateral 3.5 digits (minus fingertips). See illustration above - radial distribution in red
38
What are the roots, motor and sensory location of the ulnar nerve?
Roots: C8, T1
Motor: Intrinsic muscles of hand minus LOAF muscles; FCU and medial 1/2 FDP in forearm
Sensory: Palmar and dorsal surfaces of lateral palm and lateral 1.5 digits. See illustration above - ulnar distribution in yellow
39
What are the roots, motor and sensory location of the median nerve?
Roots: C5, C6, C7, C8, T1
Motor: Flexors of wrist and digits (minus FCU and medial 1/2 FDP); LOAF muscles of hand
Sensory: Palmar surface of lateral hand and lateral 3.5 digits; dorsal surface of lateral 3.5 fingertips. See illustration above - median distribution in blue
40
Where does the axillary nerve provide sensory innervation?
The axillary nerve provides sensory innervation to the skin overlying deltoid, often referred to as the "regimental patch".
41
Where does the musculocutaneous nerve provide sensory innervation?
The musculocutaneous nerve provides motor innervation to the anterior compartment of the arm, but its sensory branch runs to the lateral aspect of the forearm and innervates this.
42
Where does the median nerve provide sensory innervation?
The median nerve innervates the lateral 3.5 digits, on the palmar surface.
43
Where does the ulnar nerve provide sensory innervation?
The ulnar nerve provides the sensory nerve supply to the medial 1.5 digits (palmar and dorsal surfaces).
44
Where does the radial nerve provide sensory innervation?
The radial nerve provides sensory innervation to the dorsum of the hand. Specifically between the thumb and index finger.
45
Damage to the superior trunk of the brachial plexus will affect which nerves?
```
Suprascapular nerve
Axillary nerve
Radial nerve
Musculocutaneous nerve
This condition is otherwise known as Erb's Palsy. The superior trunk, formed from roots C5 and C6, contributes to the lateral and posterior cords. Therefore, the nerves affected will be the suprascapular, the musculocutaneous, the axillary and the radial. The long thoracic forms before the superior trunk. The ulnar comes from the medial cord.
```
Erb's Palsy is commonly the result of traction on the superior trunk due to forced lateral flexion of the neck contralaterally, as can occur in shoulder dystocia at birth.
46
Which movements would not be expected to be deficient in a superior trunk injury?
Finger abduction
We have identified that damage to the superior trunk will affect the suprascapular, musculocutaneous, axillary and radial nerves. Axillary involvement will cause weakness of deltoid, further limiting shoulder abduction. Musculocutaneous involvement will cause weakness of the elbow flexors . Radial involvement will cause weakness of wrist and finger extension . Finger abduction is mediated by the Ulnar nerve and is unaffected.
47
What are the osteological features of the humerus?
The bone of the arm is the humerus.
Proximally, note the humeral head contributing to the glenohumeral joint, and the lesser tubercle anteriorly and greater tubercle laterally. Between the tubercles is the intertubercular groove, in which the long head of biceps brachii runs.
Posteriorly on the shaft, note the spiral groove, along which travels the radial nerve.
Distally, note the epicondyles, larger medially than laterally. The trochlea articulates with the ulna and the capitulum articulates with the radius.
48
What are the two fascial compartments of the arm?
Anterior compartment
Consists of three muscles: coracobrachialis, brachialis and biceps brachii. Biceps brachii has two heads. The short head originates on the coracoid process of the scapula, while the long head originates on the supraglenoid tubercle (intra-articular). Muscles of the anterior compartment flex the elbow. Biceps also supinates the forearm.
Posterior compartment
One important muscle: triceps brachii, which has three heads. The long head originates from the infraglenoid tubercle, the lateral head from the posterior proximal humerus and the medial head from the posterior distal humerus. Between the medial and lateral heads is the spiral groove. Triceps brachii acts to extend the elbow.
49
What arteries are present in the arm?
Arteries
At the inferior border of teres major, the axillary artery becomes the brachial artery. The brachial artery provides a deep branch which travels posteriorly and supplies the deltoid and triceps. The rest of the brachial artery remains anterior and gives branches to the anterior compartment. Distally, it bifurcates to form the radial and ulnar arteries.
50
What veins are present in the arm?
Veins
Deep veins follow the arteries. Additionally, there are two superficial veins. The basilic vein, medially, drains into the brachial vein. The cephalic vein, laterally, runs in the deltopectoral groove and drains into the axillary vein.
51
What nerves supply the muscles of the arm?
The muscles of the anterior compartment are supplied by the musculocutaneous nerve. The muscles of the posterior compartment are supplied by the radial nerve.
However, all five main terminal branches of the brachial plexus travel through the arm to supply the upper limb:
The axillary nerve winds posteriorly around the surgical neck of the humerus.
The musculocutaenous nerve pierces coracobrachialis and then travels in the anterior compartment, supplying it.
The radial nerve travels in the spiral groove on the posterior surface of the humeral shaft and supplies the posterior compartment. It then crosses the elbow anterior to the lateral epicondyle.
The median nerve travels anteromedially in the arm and crosses the cubital fossa medial to the brachial artery.
The ulnar nerve travels posteromedially in the arm and crosses the elbow posterior to the medial epicondyle.
52
What is the cubital fossa and what are its boundaries?
The cubital fossa is a triangular space anterior to the elbow. Its boundaries are:
Superior: an imaginary line between the two humeral epicondyles
Lateral: medial margin of brachioradialis
Medial: lateral margin of pronator teres.
Its roof consists of fascia and skin, and there is little room for expansion of the space.
53
What are the contents of the cubital fossa?
The contents, from lateral to medial, are:
Biceps brachii tendon, which runs through to attach to the distal radius, and off which comes the bicipital aponeurosis, which separates superficial and deep structures in the cubital fossa
Brachial artery, which bifurcates into the radial and ulnar arteries at the inferior aspect of the cubital fossa
Median nerve, which runs just medial to the artery and leaves the cubital fossa by passing between the two heads of pronator teres to supply most of the anterior compartment of the forearm
54
What is the elbow and what movements does it allow?
The elbow is a synovial hinge joint, formed by two articulations: one between the radial head and the capitulum of the humerus, and one between the trochlea notch of the ulna and the trochlea of the humerus. It permits flexion and extension of the forearm, and can be locked in extension by the olecranon of the ulna hooking in to the olecranon fossa of the humerus.
It is supported by the radial and ulnar collateral ligaments for stability.
As the bones are so superficial posteriorly at the elbow, there is a bursa over superficial to the olecranon (the olecranon bursa) to reduce friction and allow it to moove freely under the skin.
55
Which three terminal branches of the brachial plexus cross the elbow to enter the forearm?
Three of the five main terminal branches of the brachial plexus cross the elbow to enter the forearm.
Median nerve: crosses the cubital fossa (see first tab)
Radial nerve: crosses anterior to the lateral epicondyle, travels deep to brachioradialis and splits into a superficial cutaneous and a deep branch
Ulnar nerve: the only nerve to cross the elbow posteriorly, it passes posterior to the medial epicondyle, travelling very superficially in the cubital tunnel. This gives rise to the 'funny bone' sensation of banging the elbow in this region.
56
Which structures are located in the anterior compartment of the arm?
Elbow flexion
Supination
Biceps brachii
Musculocutaneous nerve
57
Which structures are located in the posterior compartment of the arm?
Radial nerve
Triceps brachii
Elbow extension
58
Where is the cephalic vein?
This superficial vein travels up the lateral aspect of the forearm and arm, then through the deltopectoral groove, and drains in to the axillary vein
59
Where is the basilic vein?
This superficial vein travels up the medial forearm and arm, and drains into the brachial vein
60
What helps you to orientate yourself in the cubital fossa?
Medial epicondyle of humerus
61
What is the medial cubital vein?
Although there is a huge amount of anatomical variation in the venous system, most people will have some sort of anastomotic link between the basilic and cephalic veins in the cubital fossa region. Often, this will be a large calibre, very superficial vein - the median cubital vein - which is ideal for venepuncture
62
Where is the ulnar nerve?
The ulnar nerve can just about be sen here travelling posteromedially in the arm. Note how it crosses the elbow posterior to the medial epicondyle
63
Where is the median nerve?
The most medial structure in the cubital fossa, the nerve can be seen here passing deep to pronator teres and the bicipital aponeurosis to enter the anterior forearm, the majority of which it supplies.
64
Where is the brachial artery?
The pulse of the artery can be felt medial to the biceps tendon. Typically, the brachial artery will bifurcate at the inferior aspect of the cubital fossa, as can be seen here
65
Where is the distal tendon of biceps brachii?
The most lateral of the contents of the contents of the cubital fossa, the tendon is easily palpable. It is travelling distally to insert on to the proximal radius
66
Where is the bicipital aponeurosis?
The biceps tendon gives off this aponeurosis which fans out over the cubital fossa and proximal anterior forearm. Note how the important structures of the cubital fossa typically pass deep to it. In a not uncommon anatomical variation, the ulnar artery can run superficial to it after branching from the brachial artery - this is a potential risk during venepuncture
67
What is the superficial radial nerve?
This is the sensory branch of the radial nerve. It supplies sensation to the skin of the base of the thumb and dorsal aspect of the lateral hand
68
What is the brachioradialis?
This strange muscle of the posterior compartment of the forearm has minor functions in flexion, pronation and supination of the forearm. Its medial margin is the lateral border of the cubital fossa. The radial nerve can be found deep to it, at which point it splits into deep and superficial branches
69
What is the pronator teres?
This muscle, as its name suggests, is a pronator of the forearm. The median nerve passes deep to pronator teres to enter the anterior compartment of the forearm
70
What could indicate damage to the brachial artery in a catheterisation?
The large amount of bruising and swelling in the cubital fossa suggests that there has been bleeding here and a haematoma is forming. The artery in the cubital fossa is the brachial artery. Sometimes, during arterial catheterisation, it can be particularly difficult to navigate the area where the radial artery becomes the brachial artery (at the bifurcation of the brachial artery). This is likely to be the case in this scenario - the catheter tip has become stuck and there has been a small perforation of the brachial artery.
71
Where might you feel a pulse to check that the distal arterial supply is still intact?
The radial pulse can be palpated here and will give you useful information about the flow in the radial artery. The temperature and colour of the hand are good clues too
The ulnar pulse is palpable here (in theory). In practice it can be difficult to feel, especially in patients with arterial disease. If you suspect an injury at level of the bifurcation of the brachial artery, it is important to check both radial and ulnar pulses
72
Which nerve is least vulnerable to compression by a haematoma in the cubital fossa?
Ulnar nerve
The key here is to recognise which structures are closest to the brachial artery in the cubital fossa. The median nerve (B) is directly adjacent, so this is the most likely to be involved. The lateral cutaneous nerve of the forearm (A) is a branch of the musculocutaneous nerve, which travels just lateral to the cubital fossa, superficial to brachioradialis. The radial nerve (D) similarly is just lateral, but deep to brachioradialis. The ulnar nerve (C) is very unlikely to be involved as it is posterior at the elbow.
73
Which sensory nerve innervates the thumb and first 2.5 fingers?
Median nerve
This is the sensory distribution of the median nerve. Pins and needles in this area suggests that there is some sort of problem with the median nerve - likely compression. Given that we know there is a large blood clot developing in the cubital fossa, this is likely to be the cause of the compression. However, don't forget that Al has a compressive cuff around his wrist as well to prevent bleeding at the puncture site, so this may also be compressing the median nerve at the wrist.
74
Which movements involve the median nerve?
Thumb opposition
Finger flexion
Wrist flexion
Thumb flexion
75
Which movements do not involve the median nerve?
Wrist extension
Thumb extension
Finger adduction
Thumb adduction
76
What are the bones in the forearm and their corresponding joints?
The bones of the forearm are the radius (laterally) and ulna (medially). Both articulate with the humerus proximally to form the elbow joint, and with the wrist distally to form the wrist. Additionally, there are two radioulnar joints: one proximally and one distally. The proximal radioulnar joint - a pivot joint - permits pronation and supination of the forearm as the radius is dragged over the ulna.
The space in between the two bones is filled by interosseus membrane, which separates the anterior and posterior compartments of the forearm.
Note that the radius is smaller proximally and larger distally, whereas the ulna is larger proximally and smaller distally.
77
What are the muscles in the anterior compartment of the forearm responsible for?
The muscles of the anterior compartment of the forearm are responsible for flexion of the wrist and digits and pronation of the forearm. Many of the muscles have a common tendon, which originates at the common flexor origin on the medial epicondyle of the humerus. There are four layers of muscles in the anterior compartment.
You do not need to know each muscle in detail, but some nerve pathologies make more sense if you have an understanding of these muscles.
78
What are the 4 layers of muscle in the anterior compartment of the forearm?
```
First layer (4 muscles) - these act on the wrist and forearm. From lateral to medial, they are pronator teres, flexor carpi radialis, palmaris longus and flexor carpi ulnaris. The mnemonic Pass Fail Pass Fail (PFPF) can be a useful way to remember this
Second layer (1 muscle) - this layer is made up only of flexor digitorum superficialis (FDS), which flexes the proximal interphalngeal joints
Third layer (2 muscles) - these muscles are flexor pollicis longus, which flexes the thumb, and flexor digitorum profundis (FDP), which flexes the distal interphalangeal joints
Fourth layer (1 muscle) - the final muscle is pronator quadratus, which pronates the forearm
```
79
Which two nerves innervate the anterior muscle of the forearm?
Innervation of the anterior forearm muscles is shared by the median nerve and the ulnar nerve.
Median nerve - in yellow bellow. Innervates all of the anterior compartment except flexor carpi ulnaris and the medial half of flexor digitorum profundis
Ulnar nerve - in green below. Innervates flexor carpi ulnaris and the medial half of flexor digitorum profundis
80
Which arteries and veins serve the forearm?
Arteries
Most of the anterior compartment is supplied by the ulnar artery and its branches. The radial artery supplies the remainder laterally
Veins
Deep veins follow the arteries. Superficially, the cephalic vein is found laterally, and the basilic vein medially
81
Which muscles of the forearm flex the interpharyngeal joints?
Flexor pollicis longus
Flexor digitorum profundis
Flexor digitorum superficialis
82
Which muscles of forearm are responsible for pronation?
Pronator teres
| Pronator quadratus
83
Which muscles of the forearm are responsible for wrist flexion?
Flexor carpi ulnaris
Palmaris longus
Flexor carpi radialis
84
What is the appearance of epicondylitis (Golfer's Elbow)?
The medial and lateral epicondyles of the humerus can be seen on the image (medial left, lateral right). Originating from the medial epicondyle, there is a band of brighter soft tissue. This is the common flexor origin, which is inflamed (tendinitis). The medial epicondyle itself also appears brighter than the lateral epicondyle, suggesting epicondylitis.
85
Which movements are likely to accentuate the pain in Golfer's Elbow?
Wrist flexion
Pronation
The problem is with the medial epicondyle and common flexor origin, into which the pronators of the forearm and flexors of the wrist and digits attach. Performing these movements against resistance will put strain on the tendon and worsen the pain. This is a useful test in the diagnosis of golfer's elbow.
86
Thinking about the anatomical relations of the medial epicondyle, medial epicondylitis is most likely to progress to inflammation of which nerve?
Ulnar nerve
The ulnar nerve is intimately related to the medial epicondyle, running posterior to it in the cubital fossa. Inflammation of the medial epicondyle, therefore, may progress to inflammation of the ulnar nerve. Of note, there may very rarely be median nerve involvement due to compression between the heads of pronator teres.
The axillary and musculocutaneous nerves are too proximal, and the radial nerve is too lateral.
87
If there is coexistant ulnar nerve inflammation, where would you test to ensure its sensory distribution is intact?
Many clinicians will use the little finger to test ulnar nerve sensory function
This is certainly within the sensory distribution of the ulnar nerve.
88
If there is coexistent ulnar nerve inflammation, which movements may be weak?
Flexion of medial two digits
Flexion of wrist medially
In the forearm, the ulnar nerve supplies FCU and the medial half of FDP. All the other muscles are supplied by the median nerve. Therefore, a problem with the ulnar nerve will only affect flexion of the wrist on the medial side and flexion of the medial two digits.
89
How would golfer's elbow be treated?
Advice is to rest the arm for 4-6 weeks and take NSAIDs as needed (if the ulnar nerve is not involved in the injury)
90
What are the two layers of the posterior compartment of the forearm and what are their features?
The muscles of the posterior compartment of the forearm cannot be categorised as easily as those in the anterior compartment. They can, however, be broadly divided into a superficial and a deep layer.
You are not expected to know these muscles individually.
Superficial layer - primarily act on wrist and digits (except thumb and index finger). Extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi and extensor carpi ulnaris all originate via a common extensor tendon on the lateral epicondyle. Extensor carpi radialis longus and brachioradialis originate on the lateral supracondylar ridge.
Brachioradialis has a minor role in supination and pronation, and, paradoxically, flexion of the elbow. It can be found overlying the lateral epicondyle of the humerus (looking like it is in the anterior compartment of the forearm)
Deep layer - primarily act on the thumb and index finger: extensor pollicis longus and brevis, extensor indicis, abductor pollicis longus. The exception is supinator, whose action, thankfully, is supination.
Note the space formed at the base of the thumb, bounded by the extensor pollicis longus and brevis tendons. This space is known as the anatomical snuffbox. Note also all tendons crossing the wrist deep to the extensor retinaculum.
91
What is the common extensor origin?
Common tendon of ECRB, EDC, EDM and ECU originating from lateral epicondyle
92
Where is the radial nerve and what does it innervate?
The radial nerve pieces supinator to enter the posterior compartment of the arm. Here it innervates all of the muscles in the compartment.
93
Where is the extensor retinaculum?
Note the extensor tendons passing deep to the retinaculum to cross the wrist
94
What does the superficial radial nerve supply?
Supplies the skin of the dorsolateral hand
95
What is the extensor pollicis longus (EPL)?
One of two extensors of the thumb. Its tendon attaches to the distal phalanx of the thumb and forms the medial border of the anatomical snuffbox
96
What is the anatomical snuffbox?
Within the anatomical snuffbox runs the radial artery (feel your pulse here). Deep to this is the Scaphoid bone.
97
What is the extensor pollicis brevis (EPB)?
One of two extensors of the thumb. Its tendon attaches to the proximal phalanx of the thumb and forms the lateral border of the anatomical snuffbox together with the tendon of APL, which is parallel and closely related
98
What is the abductor pollicis longus (APL)?
The tendon of APL runs parallel to EPB, just anterior to it, and together the two tendons for the lateral border of the anatomical snuffbox. Together with abductor pollicis brevis, it abducts the thumb
99
What is a name for a fracture in the middle of the humerus?
This type of fracture is usually referred to as a humeral shaft fracture, or more specifically a midshaft humeral fracture.
100
Which nerve is most at risk in a midshaft humeral fracture?
Radial nerve
The radial nerve is very closely related to the humeral shaft as it runs on its posterior surface in the spiral groove. A fracture like this can damage the radial nerve (C), either by means of compression or transection, and can also damage the profunda brachii artery, which is close by. The long thoracic (A) and thoracodorsal (B) nerves are found in the axilla. The axillary nerve (D) is more proximal, and the median nerve (E) is more superficial.
101
Which movements may be affected by a radial nerve injury?
Wrist, elbow and finger extension
Wrist extension is innervated by the radial nerve - radial nerve palsy may lead to 'wrist drop'
Elbow extension happens via triceps brachii. It may or may not be affected by radial injury, depending on whether the injury is before or after the radial nerve gives branches to triceps.
Finger extension is innervated entirely by the radial nerve.
102
You want to test the sensory distribution of the radial nerve. Where is the best place to do this?
The first interdigital web space on the dorsum of the hand is the ideal place to test the sensory distribution of the radial nerve - more specifically, its superficial branch
103
The tendons of which of these muscles are boundaries of the anatomical snuffbox?
Extensor pollicis brevis
Extensor pollicis brevis
Abductor pollicis longus
The medial border of the anatomical snuffbox is the tendon of EPL. The lateral border is formed by the tendons of both EPB and APL, which run parallel and are very closely related. APB and FPB are both muscles of the thenar eminence of the hand.
104
Tenderness in the anatomical snuffbox is most likely to be associated with fracture of which bone, which forms the majority of its floor?
Scaphoid bone
The scaphoid forms the floor of the anatomical snuffbox, so a scaphoid fracture may be detected as tenderness on palpation of the anatomical snuffbox. Scaphoid fractures are commonly the result of a fall onto an outstretched hand, and are notoriously difficult to detect on x-ray acutely.
Arterial supply to the scaphoid is retrograde (distal to proximal). Failure to detect a scaphoid fracture may lead to prolonged disruption of the blood supply, which may cause avascular necrosis of the proximal fragment and chronic problems with the wrist joint.
