Workbook questions session 3 & 4

Question 1

Define Amelia

Answer 1

A complete absence of a limb or limbs

Question 2

Define Meromelia

Answer 2

Partial absence of a limb or limbs

Question 3

Explain polydactyly?

Answer 3

Supernumeracy (extra) fingers or toes; often an extra digit is incompletely formed
and lacks proper muscle fixation. In the hand, the extra digit is either on the
ulnar or radial side rather than central; in the foot it on the fibular side.

Question 4

Explain syndactyly?

Answer 4

Fusion of fingers or toes; more frequent in the foot than in the hand. Syndactyly
results from a lack of differentiation between two or more digits. Normally
the mesenchyme in the periphery of the hand and foot plates condenses to
form the primordial of the fingers and toes and the thinner tissue between them
breaks down. In some cases, there is also fusion of the bones. Syndactyly
is most frequently observed between the third and fourth fingers and second
and third toes.

Question 5

What is the structural difference between “cutaneous syndactyly” and “osseous syndactyly”?

Answer 5

Cutaneous syndactyly:- Webbing of the skin between the fingers and toes results from failure of this tissue breakdown to occur.
Osseous syndactyly: In some cases, there is also fusion of the bones.

Question 6

What is the structural defect underlying congenital dislocation of the hip (CHD)?

Answer 6

Underdevelopment of acetabulum and head of femur.

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Question 7

CHD is associated with breech presentation (i.e. buttocks rather than head delivered first). Speculate on why this might be so?

Answer 7

Breech presentation may place undue pressure on the developing hip joint: fails to complete normal development.

Question 8

What is the function of the apical ectodermal ridge (AER)?

Answer 8

Stimulates outgrowth of limb and maintains undifferentiated state in mesenchyme immediately underlying it.

Question 9

Explain what happens if the apical ectodermal ridge (AER) is disrupted and give one mechanism causing its disruption.

Answer 9

No limb growth/ shortened limbs; interference affecting blood vessels of AER

Question 10

Name the muscles and their nerve supply that cause flexion at the elbow.

Answer 10

Brachialis – Musculocutaneous;

Biceps brachii – Musculocutaneous;

Brachioradialis – Radial nerve

Question 11

Where does the brachial artery lie in relation to the median nerve in the upper
arm and in the cubital fossa?

Answer 11

In the upper arm – it lies medial to the median nerve;

in the cubital fossa it lies
lateral to it

Question 12

Which structure lies immediately anterior to the brachial artery and the median nerve in the cubital fossa?

Answer 12

Bicipital aponeurosis; this structure which comprises of collagen fibres radiating from the distal part of the biceps tendon passes obliquely across the cubital fossa and merges with the fascia covering the flexor muscles in the medial side of the forearm. It provides some protection to the brachial artery & the median nerve.

Question 13

Where in the elbow region can you normally palpate the ulnar nerve against the humerus?

Answer 13

The ulnar nerve at the elbow passes behind the medial epicondyle of the humerus. It lies in close proximity to the bone surface (& grooving it). It enters the forearm passing through a structure called the “cubital tunnel” formed by the tendinous arch joining the humeral and ulnar heads of the attachment of flexor carpi ulnaris. Here the nerve could get compressed to produce symptoms/signs of the “cubital tunnel syndrome”.

Question 14

Trauma of the ulnar nerve at the elbow results in numbness and tingling sensation and forearm and hand. What clinical term is used to describe this feeling?

Answer 14

Paraesthesia; anaesthesia means loss of feeling or sensation.

Question 15

What is subcutaneous olecranon bursitis and how does it occur.

Answer 15

The bursa lying between the skin and the olecranon process of the ulna becomes
inflamed and produces a swelling due to excessive friction. This condition which is known as subcutaneous olecranon bursitis (also known as “student’s elbow, miner’s elbow). The bursa may become infected and the skin area superficial to it may become inflamed.

Question 16

State three specific factors contribute to the stability of the shoulder joint?

Answer 16

The tone of the rotator cuff muscles; the coracobrachialis, the short head of biceps and the long head of triceps assist the deltoid in resisting downward dislocation of the joint.

Capsular and extracapsular ligaments.

Glenoid labrum helps to deepen the glenoid fossa (cavity).

Question 17

Why does the humeral head dislocate so easily? (½ mark)

What is the usual direction of dislocation and why?

Answer 17

The glenoid fossa (cavity) is relatively shallow; it accepts a little more than a third of the humeral head. Although the joint is strengthened on its superior, anterior and posterior aspects, it is weak on its inferior aspect. Hence, the head of the humerus usually dislocates inferiorly, but ends up as an anterior (subcoracoid location) due to the pull of muscles , i.e. anterior-inferior dislocation.

Question 18

What is the “coraco-acromial arch” and what is its role at the shoulder when falling down on an outstretched hand?

Answer 18

The arch is an extrinsic, protective osseoligamentous structure formed by the smooth inferior aspect of the acromion and the coracoid process of the scapula with the coracoacromial ligament spanning between them. It forms a protective arch that overlies the head of the humerus, preventing its superior displacement from the glenoid cavity of the scapula.

Question 19

Which nerve and blood vessels are at risk during the inferior displacement of the humeral head from the glenoid cavity (as in anterior-inferior dislocation of
the shoulder)?

Answer 19

Axillary (circumflex) nerve and circumflex humeral arteries

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Question 20

How would you determine the integrity of the above nerve in a patient with a dislocated shoulder? What would you not do and why?

Answer 20

Test for sensation in the “regimental badge area” on the upper lateral part of the arm (area supplied by the cutaneous branch of the axillary nerve).
Do not test motor function, as this would lead to more damage.
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Question 21

In injuries of the shoulder joint, the humerus may fracture at its “surgical neck”. Where is the “anatomical neck” of the humerus and give one anatomical significance of it?

Answer 21

The anatomical neck is formed by the groove circumscribing and separating the head from the greater and lesser tubercles.

Significance:
• The articular capsule of the joint is attached nearby.

• The anatomical neck also marks the region of the epiphyseal growth plate during the growth in length of the humerus

Question 22

List all the movements of the scapula (six of them) and the principle muscles that produce them

Answer 22

Protraction – Serratus anterior
Retraction – (Middle fibres of) trapezius, rhomboids
Elevation – (Upper fibres of) trapezius, levator scapulae
Depression – (gravity) (relaxation of elevator muscles)
Lateral rotation/upward rotation – upper and lower fibres of trapezius
Medial rotation/downward rotation – Latissimus dorsi, levator scapulae, rhomboids (tilt glenoid cavity inferiorly)
NB In lateral/upward rotation of the scapula, the glenoid cavity moving superiorly (i.e. when upper limb is abducted). Converse is true for medial/downward rotation.

Question 23

Which muscles are involved in the abduction of the arm from 0° to 90° and then 90° to 180°?

Answer 23

Supraspinatus (15 – 20°)

Deltoid (90°)

Upper and lower fibres of the trapezius (above 90°)

Serratus anterior

Question 24

Describe two effects of a torn supraspinatus tendon as shown in clinical examination of the shoulder joint?

Answer 24

Failure of initiation of abduction in first 15 degrees
When the person is asked to lower the fully abducted arm slowly and smoothly, from approximately 90 °, the limb suddenly drops to the side in an uncontrolled manner. This is mainly due to the torn supraspinatus tendon (the tendon tears due to degenerative tendonitis because it is relatively avascular).

Question 25

What is the significance of the subacromial bursa? Describe the condition of painful arc syndrome.

Answer 25

The tendon of supraspinatus is separated from the coracoacromial ligament, acromion and deltoid by the subacromial bursa. When the bursa is inflamed (subacromial bursitis), abduction of the arm is extremely painful during the arc of 50° to 90° (“painful arc syndrome”). The pain may radiate as far distally as the hand. Acute pain is also felt lateral to the acromion.

Question 26

Which nerve has been affected to explain hypersensitivity from the axilla to the medial side of the arm following axillary clearance?

Answer 26

Intercosto-brachial nerve (T2); lateral cutaneous branch of T2 penetrates the serratus anterior muscle and enters the axilla and the arm; nerve sweeps across from the thoracic wall to supply the skin of the lateral wall of the axilla.

Question 27

Which nerve damage and what muscle weakness causes a “winged scapula”?

Answer 27

The long thoracic nerve (nerve to serratus anterior muscle) may have been injured during the operation. Serratus anterior muscle holds the scapula against the chest wall and contraction of this muscle moves the scapula around the chest wall as in protraction.
Paralysis of the serratus anterior muscle (due to its nerve injury) causes the medial border of the scapula and its inferior wing to “wing” because of the unopposed action of muscles (e.g. the rhomboids) on the medial border of the scapula.

Question 28

Explain why this patient (following axillary clearance) could not abduct her upper limb above the horizontal?

Answer 28

The affected serratus anterior muscle is unable to rotate the scapula laterally (glenoid fossa to face superiorly) to allow complete abduction of the upper limb (i.e. beyond
90 °).

Question 29

Explain why the upper limb may become swollen with lymphatic fluid following axillary clearance.

Answer 29

Excision of axillary lymph nodes and lymphatic vessels leads to the disturbance (in this instance the accumulation of lymph) of the normal lymphatic drainage of the upper limb; the lymph nodes in the axilla receive lymph from the whole of the upper limb.

Question 30

State the mechanisms by which cancerous tissue may spread.

Answer 30

Through the blood (haematogenous), lymphatics or by direct spread to local tissues.

Question 31

What is a myotome?

Answer 31

A particular group of muscles sharing nerve from spinal cord segment or brain stem.

Question 32

Cervical nerves 5, 6 and 7 emerge above the corresponding numbered vertebra, while cervical nerve 8 emerges below vertebra C7. Explain why this is so.

Answer 32

There are 7 cervical vertebrae & 8 cervical nerves. The first cervical nerve emerges from the spinal cord and passes between the base of the skull and the 1st cervical vertebra; thus the 8th nerve emerges below C7. From T1 down, the spinal nerves exit below their corresponding vertebra.

Question 33

Which nerve is likely to be injured in mid-shaft humeral fracture and why?

Answer 33

Radial nerve; the nerve runs in the radial (or spiral) groove on the posterior surface of the shaft of humerus. It is closely associated with the bone and is likely to be injured in mid-shaft humeral fracture.

Question 34

What would be the effect of a mid humeral fracture ( &damage to radial nerve within the radial groove) on movement at the elbow?

Answer 34

No effect or weakened extension of the elbow. Flexion is fine. Most of the nerve supply to the triceps the three heads of the triceps branches prior to the radial nerve entering the spinal groove or just in the proximal part of the groove. As they most likely branch before the nerve lesion there will be no or little compromise of extension. Anconeus is paralysed but this has only a minor role in elbow extension.

Question 35

Explain why a mid-humeral fracture might have caused poor wrist and finger extension?

Answer 35

Injury to the radial nerve in the radial groove would result in paralysis of brachioradialis and all extensor muscles of the wrist and fingers. This injury results in a clinical sign called “wrist drop” (i.e. inability to extend the wrist and fingers at the metacarpophalangeal joints (MCP joints); the wrist is flexed because of unopposed
2
flexor muscles and gravity.

Question 36

Precisely, where in the injured arm would the surgeon feel for arterial pulses?

Answer 36

In the cubital fossa (brachial pulse), at the wrist (radial pulse between flexor carpi radialis & brachioradialis & ulnar pulse above the flexor retinaculum)

Question 37

If the brachial artery was injured, describe and explain the pattern of colour change you would expect and the level of its upper limit in the arm.

Answer 37

Bruising of the cubital fossa & ischemia & pallor of the forearm. The distal limb would be pale below site of the lesion. Some colour may remain in the limb if superior ulnar collateral arteries arise superior to vessel damage. The deep brachial artery anastomoses with the recurrent radial artery, also providing some blood flow to forearm.