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appendix
OSCE Scenario Answers
OSCE SCENARIO ANSWER 1.1
A 19-year-old male is admitted with a right-sided spontaneous pneumothorax. He has a past history of a treated coarctation of the aorta. He requires a chest drain.
1. Describe the anatomy of a typical intercostal space.
• A typical intercostal space contains three muscles
comparable to those of the abdominal wall:
• the external intercostal muscle passes downwards
and forwards from the rib above to the rib below.
It is decient in front where the anterior intercostal membrane replaces it
• the internal intercostal muscle passes downwards
and backwards. It is decient behind where it is
replaced by the posterior intercostal membrane
• the innermost intercostal muscle may cover more
than one intercostal space.
• e neurovascular bundle lies between the internal
and innermost intercostals and consists of (from
above down) the vein, artery and nerve, the vein
lying directly in the groove on the undersurface of
the corresponding rib.
2. Why is this knowledge important in your technique of
insertion of an intercostal drain?
Insertion of a chest drain should be close to the upper border of the rib below the intercostal space to avoid the neurovascular bundle.
3. What is the ‘triangle of safety’ when inserting a chest
drain?
• e ‘triangle of safety’ is dened by the anterior border of latissimus dorsi, the lateral border of pectoralis major and a horizontal line lateral at the level of
the nipple with an apex below the axilla. is corresponds to the 5th intercostal space.
• is basically corresponds to an insertion of a drain
between the anterior axillary line and the mid-axillary line at the level of the nipple. Insertion of a
drain at a lower level risks damage to abdominal
contents.
4. Explain the anatomical basis for notching of the lower
border of a rib seen on a chest X-ray of a patient with
coarctation of the aorta.
• In coarctation of the aorta, collaterals develop
between vessels above and below the narrowing.
Blood reaches the aorta beyond the narrowing via
branches of the subclavian artery, which arise above
the aortic narrowing. is results in extreme vascularity of the whole thoracic wall owing to the many
arteries which arise indirectly from the aorta above
its obliterated portion, anastomosing with vessels
connecting with the aorta below the obliteration and
the connecting channels become greatly enlarged.
• On the anterior chest wall, the thoraco-acromial, lateral thoracic and subscapular arteries from the axillary
artery, the suprascapular from the subclavian artery,
and the 1st and 2nd posterior intercostal arteries from
the costocervical trunk anastomose with the 3rd and
lower posterior intercostal arteries, whilst the internal
thoracic artery and its terminal branches anastomose
with the lower posterior intercostal arteries and the
inferior epigastric arteries. e anterior and intercostal
branches of the internal thoracic artery pass blood by
a reverse ow to the lower posterior intercostal with
which they anastomose and hence into the descending
aorta. As a consequence, the intercostal arteries dilate
and become more tortuous because of the increased
blood ow, eroding the lower border of the ribs and
hence giving rise to notching of the ribs, which can be
seen on chest X-ray.
OSCE SCENARIO ANSWER 1.2
A 35-year-old male sustains a crushing upper abdominal
injury in a road trac accident. On admission to A&E he has
a tachycardia of 120 beats/min and a systolic blood pressure
of 90 mmHg. He is complaining of abdominal and bilateral
shoulder tip pain. Urgent CT scan reveals liver and splenic
trauma as well as a ruptured le hemidiaphragm.
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SECTION IV Appendix
1. Describe the three origins of the muscular part of the
diaphragm.
• A vertebral part arising from the crura and the arcu-
ate ligaments.
• A costal part arising from the inner aspect of the
lower six ribs and costal cartilages.
• A sternal portion arising by two slips from the deep
surface of the xiphisternum.
2. At what vertebral levels do the oesophagus and the IVC
pass through the diaphragm?
e oesophagus passes through the right crus at the level
of T10 whilst the IVC passes through the central tendon of
the diaphragm at the level of T8.
3. What is the nerve supply of the diaphragm?
e diaphragm receives its entire motor supply from the
phrenic nerve (C3, 4, 5). e sensory nerves from the central part of the diaphragm run in the phrenic nerve, whilst
the peripheral part of the diaphragm receives sensory bres
from the lower six intercostal nerves.
4. Explain why in some cases irritation of the diaphragm may result in referred pain to the shoulder,
while in others it may result in referred pain to the
abdomen.
e sensory nerve supply of the parietal pleura and peritoneum on the upper and lower surfaces of the diaphragm,
respectively, is as follows:
• Serous membranes related to the central part of the
diaphragm are innervated by the phrenic nerve,
while those related to the peripheral regions of the
diaphragm are supplied by the lower six intercostal
nerves.
• is double sensory innervation explains the dier-
ent distribution of referred pain that may be felt in
cases of infection or inammation of the diaphragm
such as may occur in pleurisy or pneumonia, aecting its upper surface, or in peritonitis, aecting its
lower surface. For example, if it is more the central
part of the diaphragm that becomes inamed in
cases of acute peritonitis, the patient may complain
of pain referred to the area of the cutaneous distribution of C4, i.e. the shoulder.
• On the other hand, if the periphery of the diaphragm
becomes involved in a patient with pleurisy or pneumonia, the patient may complain of pain in the area
of distribution of the cutaneous branches of the
lower intercostal nerves and the pain is referred into
the abdomen.
• is partly explains why right lower lobar pneu-
monia in a child results in pain referred to the right
lower quadrant, which may be mistaken for acute
appendicitis.
OSCE SCENARIO ANSWER 1.3
A 60-year-old female undergoes a right open nephrectomy
via a loin approach through the bed of the 12th rib. A postoperative chest X-ray shows a small right pneumothorax.
1. Describe the surface anatomy of the pleura.
• e cervical pleura extends above the sternal end of
the 1st rib. It follows a curved line drawn from the
sternoclavicular joint to the junction of the inner
one-third and outer two-thirds of the clavicle, the
apex arising 2.5 cm above the clavicle.
• A line of pleural reection passes behind the sternoclavicular joint on each side to meet in the midline
at the angle of Louis (2nd costal cartilage level). e
right pleural edge passes vertically down to the level
of the 6th costal cartilage and crosses:
• 8th rib in the mid-clavicular line
• 10th rib in the mid-axillary line
• 12th rib at the lateral border of erector spinae.
• e le pleural edge arches laterally at the 4th costal cartilage and descends lateral to the border of the
sternum, where it follows a path similar to the right
side. e medial end of the 4th and 5th le intercostal spaces are therefore not covered by pleura.
• e pleura descends below the 12th rib at its medial
extremity.
2. Why has this patient developed a right pneumothorax?
e pleura descends below the medial extremity of the 12th
rib and therefore may be inadvertently opened in the loin
approach to the kidney.
3. At which other site, other than surgery on the thorax,
may surgery or trauma result in a pneumothorax?
e pleura arises above the clavicle in the neck. It may be
injured at surgery in the lower part of the neck, by a stab
wound, or during insertion of an internal jugular line.
OSCE SCENARIO ANSWER 1.4
A 22-year-old male is brought to A&E with a penetrating injury in the le third intercostal space, anterior to the
mid-axillary line. His blood pressure is 80/40, pulse rate 140
beats/min and has mued hear sounds and distended neck
veins. A diagnosis of cardiac tamponade is established.
1. Describe the surface anatomy of the heart.
Distance in cm is from sternal border. Red is superior border, blue is right border, black is le border and green is
inferior border (Fig. 1.4A).
2. Why does cardiac tamponade result in drop in blood
pressure and clinical shock?
e pericardium is formed by a xed brous layer that is
lined by a parietal layer of serous pericardium. While the
Fig. 1.4A Surface anatomy of the heart.
brous pericardium can stretch gradually if there is enlargement of the heart, a sudden increase in the pericardial content
(as in a sudden bleed) can result in cardiac malfunction due
to inability of the brous pericardium to stretch. A relatively
small amount of blood can restrict cardiac activity and interfere with cardiac lling, resulting in shock.
3. Describe how you would treat a cardiac tamponade.
When cardiac tamponade is diagnosed, the most recent edition of the ATLS® manual recommends emergency thoracotomy or sternotomy by a qualied surgeon as soon as possible.
Administration of intravenous uid will raise the patient’s
venous pressure and improve cardiac output transiently while
preparations are made for surgery. If surgical intervention is
not possible, pericardiocentesis can be therapeutic, but it does
not constitute denitive treatment for cardiac tamponade.
Subxiphoid pericardiocentesis can be performed by cleaning
the skin and performing a puncture to the le of the xiphisternum using a 16–18 gauge 15 cm cannula. Aim at a 45° angle
towards the tip of the le scapula. Aspirate continuously; blood
in the syringe conrms the correct position. Push the needle
too far and the ECG will show ST changes (injury pattern)
APPENDIX OSCE Scenario Answers
and should be withdrawn immediately. Aer the removal of
blood (it doesn’t need to be much) the blood pressure should
improve. Remove the needle leaving the cannula and attach a
three-way tap. If symptoms return the three-way tap can be
opened and re-aspirated. Because complications are common
with blind insertion techniques, pericardiocentesis should represent a lifesaving measure of last resort in a setting where no
qualied surgeon is available to perform a thoracotomy or sternotomy. Ultrasound guidance can facilitate accurate insertion.
433
OSCE SCENARIO ANSWER 1.5
An 18-month-old girl developed sudden-onset bouts of cough
and wheezes. A bowl of peanuts was found nearby while she
was playing unwitnessed. She was rushed to A&E and found
to be conscious but distressed, tachypnoeic and wheezy. A
chest X-ray revealed a collapsed lung.
1. In which main bronchus is a foreign body more likely to
be dislodged and why?
e right main bronchus is wider and more vertical; hence,
foreign bodies are more likely to be aspirated into this
bronchus
2. In relation to the surface anatomy, where does the trachea commence and terminate?
e trachea extends from lower border of cricoid cartilage
(level of the sixth cervical vertebra) to terminate into the
right and le main bronchi at the level of the sternal angle
(level of h thoracic vertebra).
3. Describe briey how you would treat the patient.
e treatment would involve taking the child to theatre and
performing a GA – a bronchoscope can then be passed to
retrieve the foreign body. A rigid bronchoscope is usually used
as it allows better visualization of the airways and manipulation of the foreign body. Once visualized, grasping forceps or a
fogarty catheter can be used to remove the foreign body.
OSCE SCENARIO ANSWER 2.1
A 19-year-old male presents with a history of vague central
abdominal pain of 8 h duration. He has now developed a
sharp pain in the right iliac fossa which is exacerbated by
moving and coughing. He has a temperature of 37.4°C and a
white cell count of 15 × 109/L. He is tender with rebound in
the right iliac fossa. A provisional diagnosis is made of acute
appendicitis and he elects for an open appendicectomy.
1. Explain the anatomical basis for the two types of pain
he has experienced.
Initial pain
• e initial pain in the central abdomen at the level of
the umbilicus is referred pain. Referred pain occurs
due to nerve bres in areas that have a high level of
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SECTION IV Appendix
sensory input, e.g. skin, and nerve bres from areas
that have low levels of sensory input, e.g. internal
organs, coming together in the same area of the spinal cord.
• Aerent pain-conducting bres from the viscera
combine with aerent pain-conducting bres from
the skin on one central neuron of the spinothalamic tract. Impulses from the viscera travel in the
same central pathway as pain impulses from the
skin to reach the same nal sensory neuron in the
brain.
• e nal sensory neuron projects pain sensation to
the skin in the place from which it usually receives
pain signals.
• e appendix is a derivative of the mid-gut. e midgut relates to the T10 segment, which is the periumbilical area of the central abdomen, and therefore
pain referred from a mid-gut structure is experienced in the central abdomen in the periumbilical
area.
• In the case of an inamed appendix, which causes
spasm of muscle in its wall, the pain is appreciated as periumbilical abdominal colic, although
the inamed appendix lies in the right lower quadrant. e appendix localizes as mid-gut pain to T10
through its autonomic nerve supply.
Localized pain
• As inammation of the appendix proceeds, the
inamed serosal peritoneum abuts against the parietal peritoneum of the right lower quadrant, which
has somatic innervation. e pain is now well localized to the right iliac fossa. Pain is then experienced
at the site of inammation near the classic site of
McBurney’s point.
• e pains therefore are two separate pains: one a
visceral pain, due to either distension of the appendicular lumen or muscle spasm in the wall of the
appendix; and the other a sharp somatic pain, due to
inammation of the parietal peritoneum. It is incorrect to say that the pain moves; it is a dierent pain
that develops in the right iliac fossa.
2. Describe the structures encountered in a gridiron incision for appendicectomy.
e incision is centred on McBurney’s point (two-thirds of
the way along a line drawn from the umbilicus to the anterior superior iliac spine). Structures encountered include:
• Skin.
• Camper’s fascia.
• Scarpa’s fascia at the lower medial end of the incision.
• e external oblique aponeurosis and muscle is then
encountered, which is split in the line of its bres,
exposing the internal oblique muscle.
• e internal oblique muscle is also split in the line of
its bres.
• Transversus abdominis muscle is then exposed and
also split in the line of its bres; extraperitoneal fat is
then encountered.
• e peritoneum is then incised.
3. What variations in position of the appendix may be
encountered when attempting to locate the appendix?
e position of the appendix is variable:
• 75% lie behind the caecum or colon, i.e. retrocaecal
or retrocolic
• 20% are pelvic
• 5% are either pre-ileal or retroileal.
OSCE SCENARIO ANSWER 2.2
A 40-year-old male presents with severe pain in the right loin
radiating into the right groin. A diagnosis of right ureteric
colic is made and a plain abdominal radiograph is requested.
1. Where would you look for the course of the ureter projected onto the bony skeleton?
A ureteric stone on a plain radiograph may be seen in relation to the following structures:
• running along the tips of the lumbar transverse processes
• crossing in front of the sacroiliac joint
• swinging out onto the pelvic wall and crossing the
ischial spine
• passing medially to the bladder.
2. At which points along the course of the ureter is a stone
likely to impact?
e narrowest parts of the ureter where a stone is likely to
impact are:
• pelvi-ureteric junction
• at the brim of the pelvis
• at the entry to the bladder.
3. How would you identify the ureter during an extraperitoneal approach?
e ureter may be identied at operation as it strips up
with the peritoneum and worm-like movements (vermiculation) may be noticed in its wall, particularly if it is stimulated by the tip of a pair of forceps.
4. What is the blood supply of the ureter and why, when
removing a kidney for transplantation, is it important
to leave abundant connective tissue around the ureter?
• e ureter receives a segmental blood supply from
the following vessels:
• renal arteries, from which it may receive a considerable contribution
• lower polar artery
• testicular or ovarian artery
• internal iliac artery
• inferior vesical arteries.
APPENDIX OSCE Scenario Answers
435
• ere is a rich anastomosis between these vessels in
the peri-ureteral connective tissue. When a kidney is
removed for transplantation, the blood supply of the
ureter depends solely on the renal artery. Blood ow
down the length of the ureter is now via collaterals,
which are in the peri-ureteral connective tissue. If
this tissue is stripped up, there is a risk of ureteric
necrosis following transplantation.
OSCE SCENARIO ANSWER 2.3
A 40-year-old female has had two attacks of acute cholecystitis and has recently had an attack of biliary colic. She has
been admitted for laparoscopic cholecystectomy.
1. Describe biliary colic. What causes it?
• Sudden onset of severe pain across the epigastrium
(it is not conned to the right upper quadrant
[RUQ]). ere are severe spasms of colic against a
background of continuous severe pain. e patient
rolls around in agony and cannot get into a comfortable position.
• It is caused by a stone impacted in the neck of the
gallbladder or in the cystic duct. e stone may fall
back into the gallbladder or pass through the cystic duct into the common bile duct, when the pain
abates suddenly.
2. What is Calot’s triangle?
Calot’s triangle is formed by the liver, the cystic duct and
the common hepatic duct. It must be exposed carefully to
dene the anatomy of the area, as variations of the anatomy
are not uncommon. e cystic artery (usually a branch of
the right hepatic artery) lies within Calot’s triangle, where
it is exposed and ligated/clipped.
3. Why is a knowledge of the structures in the free edge of
the lesser omentum important while performing gallbladder surgery?
e hepatic artery and the portal vein lie in the free edge of
the lesser omentum. If haemorrhage occurs during cholecystectomy, bleeding can be controlled by compressing the
hepatic artery and portal vein between the nger and thumb
in the free edge of the lesser omentum (Pringle’s manoeuvre).
4. What may result from the close relationship between
the fundus of the gallbladder and the duodenum?
e close relationship between the fundus of the gallbladder and the duodenum may result in an inamed gallbladder adhering to, and ulcerating into, the duodenum, causing
a cholecystoduodenal stula and subsequent gallstone ‘ileus’.
5. Gangrene of the gallbladder with perforation is rare,
even if the cystic artery has thrombosed. Why?
Gangrene of the gallbladder is rare because, even if the cystic artery thromboses, it gets a second blood supply directly
from the liver bed.
OSCE SCENARIO ANSWER 2.4
A 78-year-old male is brought into the Accident and
Emergency department with a history of a sizeable fresh
blood haematemesis. He has a history of peptic ulcer disease.
He is hypotensive and tachycardic.
1. Describe your initial management of this patient?
e initial management of the patient would be along
the lines of ABC. He will need supplemental oxygen and
large-bore i.v. access to allow rapid uid resuscitation.
Bloods should be sent for full blood count, clotting prole, urea and electrolytes (U&Es), liver function tests and
blood for cross matching. Clotting should be normalized
in patients on warfarin using either fresh frozen plasma
(FFP) or prothrombin complex concentrate (i.e. Beriplex).
Platelet count is not associated with bleeding risk or
mortality but if platelet dysfunction is present should
be >100 × 109/L. Consideration should be given to
high-dose i.v. proton pump inhibitor (PPI); these allow
clot stabilization and allow platelet aggregation. Giving
erythromycin as a prokinetic has been associated with a
reduced need for repeat endoscopy and can be considered
in some cases. A nasogastric tube can be placed to allow
old blood to be removed prior to endoscopy and in stable
patients give an indication of early re-bleeding. e mainstay of treatment in these patients is early endoscopy.
2. What are the potential options for treating bleeding
duodenal ulcers?
ere are a number of ways in which bleeding duodenal
ulcers can be treated. e main stay is endoscopy; there are
a number of methods available. ese can be divided into
the following:
• Injection agents – these include epinephrine (vaso-
constriction and tamponade), tissue adhesives,
thrombin and brin (vessel sealing and tamponade)
and sclerosing agents (thrombosis of vessels by tissue
injury).
• Mechanical therapy – endoscopic ligation clips and
banding.
• ermal therapy – these include electrocautery (dia-
thermy), heater probes and argon plasma coagulators. ese work by pressure of the device stopping
bleeding and heat coagulating the vessel
• Haemostatic powders – a number of topical powders
to induce coagulation have shown promise.
If a patient re-bleeds following endoscopy then a further
endoscopic attempt can be made to stop the bleeding. If
this fails again the options are then limited to laparotomy
and opening the duodenum and oversewing the bleeding vessel, or angiography and identication of the bleeding vessel and selective embolization. e vast majority of
bleeds are treated successfully with endoscopy.
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SECTION IV Appendix
3. Which vessel is most commonly involved in bleeding
duodenal ulcers – describe its anatomy?
e vessel most commonly involved in a bleeding duodenal ulcer is the gastroduodenal artery (GDA); it is a branch
of the hepatic artery, and it descends behind the rst part
of the duodenum and divides into the right gastroepiploic
artery and the superior pancreaticoduodenal artery.
4. Name three other causes of upper GI bleeding.
e common causes of upper GI bleeding (other than peptic ulcers) include gastric erosions, oesophageal varices,
oesophagitis, Mallory-Weiss tears and gastric cancers.
OSCE SCENARIO ANSWER 2.5
A 62-year-old male presents to his GP with weight loss,
abdominal pain, jaundice and a palpable gallbladder. He has
dark urine and pale stools.
1. What are three potential causes for his jaundice?
Jaundice can be divided into pre-hepatic, hepatic or posthepatic. is patient clearly has post-hepatic or obstructive
jaundice due to the dark urine and pale stools. Causes of this
can be divided into those in the lumen of the bile duct, in the
wall of the bile duct or outside the wall of the bile duct.
• In the lumen – gallstones, parasites, blood clots
• In the wall – congenital atresia, traumatic stricture,
sclerosing cholangitis, cholangiocarcinoma, choledochal cysts.
• Outside the wall – carcinoma (pancreas, ampulla of
Vater, malignant nodes), Mirrizi’s syndrome.
2. What is Courvoisier’s Law?
is law states that in the presence of jaundice and a palpable gallbladder the cause is not gallstones. e theory
being that gallstones tend to lead to chronic inammation,
meaning the gallbladder becomes scarred and brotic and
so unable to distend with obstruction.
3. What would you expect to see on the liver function tests?
e blood tests will obviously show a raised bilirubin
(conjugated – as it has already passed through the liver).
ere will also be a dramatically raised alkaline phosphatase. Liver enzymes can be mildly elevated but not in comparison to levels seen in hepatitis.
OSCE SCENARIO ANSWER 3.1
A patient attempts suicide by slashing the exor aspect of his
wrists in a radial to ulnar direction.
1. Which tendons are likely to be divided and how would
you test their integrity?
• Tendons which may be cut include:
• palmaris longus
• exor digitorum supercialis
• exor carpi radialis
• exor carpi ulnaris.
• It is unlikely that exor digitorum profundus will be
damaged. To test whether exor digitorum supercialis tendons have been damaged, the patient should
be asked to ex the ngers at the proximal interphalangeal joints against resistance while the distal
interphalangeal joints are held extended (to prevent
the action of exor digitorum profundus).
• Damage to the tendons of exor carpi radialis and
exor carpi ulnaris will result in weakness of exion
of the wrist against resistance. If the exor carpi ulnaris tendon alone is damaged, an attempt at exion of
the wrist will result in radial deviation. If the exor
carpi radialis tendon alone is damaged, an attempt at
exion of the wrist will result in ulnar deviation.
2. Which nerves are likely to be aected?
Median and ulnar nerves.
3. How would you test the integrity of these nerves?
e median nerve lies just deep to palmaris longus, and
the ulnar nerve lies between the ulnar artery and pisiform
bone.
• To test the ulnar nerve, the hand is placed palm downwards and the ngers straightened then abducted
and adducted against resistance. Alternatively, a
sheet of paper can be held between the adducted ngers and an attempt made to dislodge it. ere would
also be loss of sensation over the medial 1½ ngers.
• To test the median nerve, the patient is asked to
abduct his thumb against resistance. is involves
bringing the thumb forward at right angles to the
plane of the palm against resistance and feeling the
muscle contracting. With a median nerve lesion this
would not be possible. ere would also be loss of
sensation over the lateral 3½ digits.
OSCE SCENARIO ANSWER 3.2
A patient with chronic renal failure is being assessed for construction of a radiocephalic arteriovenous stula on the le wrist.
1. Where would you palpate the radial and ulnar pulses
to assess their integrity?
• Pulsation of the radial artery is felt lateral to the tendon of exor carpi radialis at the wrist.
• Pulsation of the ulnar artery is felt lateral to the tendon of exor carpi ulnaris at the wrist.
2. e ulnar pulse is not readily palpable. What test
would you use to assess the integrity of the circulation
to the hand and how would you perform it?
• It is important to check the integrity of the palmar
arch before performing a radio-cephalic stula as
there is a small risk of radial artery thrombosis. If
the ulnar artery is not patent then the hand will be
rendered ischaemic.
APPENDIX OSCE Scenario Answers
437
• e Allen test is performed. e patient is asked to
repeatedly clench the st while the radial artery and
ulnar artery are occluded by pressure at the wrist.
e patient is then asked to extend the ngers, palm
up, which should demonstrate blanching of the hand.
Pressure on the ulnar artery at the wrist is removed.
If the hand ushes rapidly (within 5 s) then the ulnar
ow is satisfactory. e test may be repeated, keeping the ulnar artery occluded and releasing the radial
artery to inow.
OSCE SCENARIO ANSWER 3.3
A 30-year-old male is taken to A&E, having fallen from a
horse and landed on the point of his right shoulder. On examination, any attempt to move the shoulder is painful.
1. Describe the anatomy of the upper end of the humerus.
• e head of the humerus forms one-third of a sphere
and faces medially, upwards and backwards.
• e head is separated from the greater and lesser
tuberosities by the anatomical neck.
• e tuberosities are separated from one another by the
bicipital groove, which contains the tendon of the
long head of biceps.
• e upper end and sha meet at the surgical neck.
2. X-ray shows a fracture of the surgical neck of the
humerus. Which nerve is likely to have been damaged?
e axillary nerve may be damaged by fractures of the surgical neck of the humerus.
3. Describe the distribution of the nerve and how you
would test for damage to the nerve.
• e axillary nerve arises from the posterior cord of
the brachial plexus. It passes through the quadrangular space accompanied by the posterior circumex
humeral artery. It ends by dividing into an anterior
and posterior branch.
• e anterior branch accompanied by the posterior
circumex humeral artery winds round the surgical
neck of the humerus deep to deltoid, which it supplies, giving o a few small cutaneous branches to
the skin covering the insertion of the deltoid.
• e posterior branch supplies teres minor and is
continued as the upper lateral cutaneous nerve of the
arm, which supplies the skin over the lower part of
the deltoid.
• Paralysis of the deltoid results in loss of abduction
of the arm from 15° to 90°. is is dicult to test
because of pain on any movement of the shoulder. It
is therefore more appropriate to test for loss of sensation in the skin over the lower part of the insertion of
deltoid (the ‘badge’ area).
OSCE SCENARIO ANSWER 3.4
A 30-year-old motorcyclist is brought to the Accident
and Emergency department aer a road trac accident.
Following application of the ATLS protocol, secondary survey revealed signicant so tissue injury to the right shoulder
and axillary areas. He was unable to abduct his arm and you
suspect he has shoulder dislocation with tear to the rotator
cu muscles and possible injury to the brachial plexus.
1. What muscles make up the rotator cu?
e rotator cu comprises the subscapularis, supraspinatus, infraspinatus, and teres minor.
2. What muscles are involved in abduction of shoulder
joint?
e supraspinatus initiates the movement of abduction.
en, the deltoid is responsible for further abducting
the arm. e scapula then rotates, bringing the glenoid
upwards. is is performed by the trapezius and serratus
anterior. e lateral rotation of humerus is achieved by
infraspinatus and teres minor.
3. e patient is noted to have his arm hanging adducted
by his side, medially rotated while the elbow is extended
and pronated. Which part of the brachial plexus is
aected and what is this injury called?
is position (waiter’s tip hand) is caused by upper brachial
plexus injury (Erb’s palsy), which is the commonest injury
of the brachial plexus. It aects roots C5 and 6 and results
in loss of abduction (deltoid and supraspinatus paralysis)
and lateral rotation movements (infraspinatus and teres
minor paralysis) of the arm and exion (biceps, brachialis
and brachioradialis paralysis) and supination of forearm
(biceps and supinator paralysis).
4. Where does the long thoracic nerve originate from?
What muscle does it supply? How can you test for
potential injury to it aer axillary dissection?
e long thoracic nerve originates from the anterior rami
of C5, 6 and 7. It supplies serratus anterior muscle. Injury
to this nerve can occur secondary to axillary surgery and
results in winging of the scapula. To assess that, you ask
the patient to stand up facing a wall. e patient then is
asked to push rmly with both hands against the wall. e
examiner observes for winging of the scapula from behind.
OSCE SCENARIO ANSWER 3.5
A 63-year-old female attends breast clinic aer feeling a le
breast lump. On examination, she had a 3×3 cm palpable
hard lump in the upper outer quadrant, and you noticed skin
puckering with arm elevation. Axillary examination demonstrated palpable enlarged lymph nodes.
1. What is the blood supply to the breast?
e blood supply of the breast arises from:
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SECTION IV Appendix
• e axillary artery via its lateral thoracic and acromiothoracic branches.
• e internal mammary artery via its perforating
branches.
• e intercostal arteries via the lateral perforating
branches.
2. What is the lymph drainage to the breast?
Most of the breast tissue drains into the axillary lymph
nodes, while the medial part drains into internal mammary
lymph nodes. Occasionally there may be drainage along the
intercostal vessels, and lymphatic channels exist from one
breast to the other; therefore, drainage is possible across the
chest wall. Rarely there may be direct drainage to the supraclavicular nodes; these should not be missed out on breast
examination.
3. How do you classify axillary lymph nodes anatomically and surgically?
Axillary lymph nodes are classied anatomically into ve
areas: anterior, posterior, lateral, central and apical, while
in surgery, the term ‘axillary clearance’ refers to axillary
lymph node dissections which can be at level I, II or III.
Level I dissection involves removing nodes in the axillary
tail (if present) and clearing the lymph nodes inferior to
the inferolateral border of the pectoralis minor. Level II
includes nodes posterior to the pectoralis minor and Level
III clears nodes superior to the muscle and up to the apex
of the axilla.
OSCE SCENARIO ANSWER 4.1
An 85-year-old female trips over the edge of a carpet at home.
She cannot get up from the oor. On arrival at hospital she
complains of pain in the right groin. On examination the
right leg is externally rotated, shortened and adducted.
1. Classify fractures of the neck of the femur.
ese fractures may be classied as either:
• intracapsular (subcapital, transcervical)
• extracapsular (basal, intertrochanteric).
2. Explain the anatomical basis for external rotation,
shortening and adduction.
• Shortening of the fractured femur is due to the
strength of the longitudinally lying muscles, especially the quadriceps and hamstrings, as well as the
adductor group, which combine to pull the limb
superior and medially.
• In external (lateral) rotation, the femoral head nor-
mally rotates about a vertical axis, passing through
the centre of the head of the femur and medial condyle. e femoral neck swings about this axis. Due to
the angle between the neck and the sha, this axis of
rotation does not pass through the sha of the femur.
When the neck of the femur is fractured, rotation
takes place about an axis passing through the sha
of the femur. Iliopsoas can now externally rotate the
femur, leaving it in the characteristic position of fractured neck of femur, i.e. externally rotated.
3. What is the blood supply of the head of the femur?
• is comes from three sources:
• vessels from the hip capsule, where this is reected
onto the neck in longitudinal bands or retinacula
(retinacular vessels)
• vessels travelling up the diaphysis
• an artery in the ligamentum teres, which is a negligible source in the adult.
• e chief source is from the retinacular vessels.
4. Explain why some fractures require a dynamic hip
screw while others require a hemiarthroplasty.
• Fractures of the femoral neck completely interrupt
the blood supply from the diaphysis. If the retinacular vessels are torn, avascular necrosis of the femoral
head will occur. Avascular necrosis of the femoral
head is much more likely to occur with intracapsular
fractures than extracapsular fractures because intracapsular fractures are more likely to disrupt the retinacular ow.
• erefore, with extracapsular fractures a dynamic
hip screw will be satisfactory, while with intracapsular fractures there is a danger of avascular necrosis
of the femoral head and a hemiarthroplasty is more
appropriate.
OSCE SCENARIO ANSWER 4.2
You are asked to examine the pulses in a patient’s lower limb.
1. Describe the anatomical landmarks you would use to
locate the peripheral pulses in the lower limb.
• e femoral artery is located at the mid-inguinal
point, which is midway between the anterior superior iliac spine and the pubic symphysis.
• e popliteal artery is located in the midline of the
popliteal fossa behind the knee. It should be palpated
in the lower half of the popliteal fossa where it can
be compressed against the at posterior surface of
the tibia. e knee should be exed to about 130°
in order to relax the muscles and fascia to facilitate
palpation.
• e posterior tibial artery is located posterior to the
medial malleolus, midway between the latter and the
medial border of the tendo calcaneus.
• e dorsalis pedis artery may be palpated on the
dorsum of the foot against the navicular and medial
cuneiform bones. It lies lateral to the tendon of
extensor hallucis longus and medial to the tendon of
extensor digitorum longus to the 2nd toe.
APPENDIX OSCE Scenario Answers
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OSCE SCENARIO ANSWER 4.3
A 60-year-old female presents with a swelling in the right
groin.
1. What are the boundaries of the femoral triangle?
e boundaries are:
• above is the inguinal ligament
• medially is the medial border of adductor longus
• laterally is the medial border of sartorius.
2. On examination, the lump is below the inguinal ligament. Based on your knowledge of the contents of the
femoral triangle, with the exception of lymphadenopathy, what pathological conditions may arise from the
contents of the triangle?
Possible conditions are femoral hernia (coming down the
femoral canal), aneurysm of the femoral artery, saphena
varix at the sapheno-femoral junction, neuroma of the
femoral nerve.
3. On examination, you believe that the lump is a lymph
node. Which structures drain to the inguinal lymph
nodes?
e following structures drain to the inguinal lymph
modes:
• the skin of the leg
• the skin of the buttock as far up as the iliac crest
• the skin of the lower abdominal wall up to and
including the umbilicus
• the skin of the labia
• the lower one-third of the vagina
• the lower half of the anal canal
• the fundus of the uterus (lymphatics accompanying
the round ligament to the groin).
OSCE SCENARIO ANSWER 4.4
A 27-year-old male is impaled on a metal pole aer falling
from some scaolding. It has entered his right buttock. You
are asked to see him on the ward several days aer recovering
from surgery. e nurse looking aer him is concerned he has
a nerve injury.
1. What is the likely nerve to be injured in a penetrating
injury to the buttock?
e most likely nerve to be injured in the buttock is the sciatic nerve. If the nerve injury is not complete it may present as a common peroneal nerve injury as the bres to this
nerve lie uppermost in the sciatic nerve.
2. What are the roots of this nerve?
e roots of the sciatic nerve are L4–5 and S1–3.
3. If he has a nerve injury what are the likely clinical signs
and why?
e sciatic nerve has both motor and sensory components. e motor signs would be diculty in exing the
knee, although some is possible via the sartorius (femoral
nerve) and gracilis (obturator nerve). ere will be plantar exion or foot drop and all the muscles below the knee
are paralysed (loss of tibial and common peroneal nerve).
Sensation in the thigh is preserved but is lost below the
knee apart from some sensation along the medial aspect of
the leg and foot from the saphenous nerve (femoral nerve).
OSCE SCENARIO ANSWER 4.5
A 52-year-old male has been hit by a car on the outside of
his le leg as he crossed the road. It is obvious he has a nasty
fracture of his lower leg. e plain X-ray has shown a nasty
comminuted proximal bular fracture and a tibial fracture.
1. What is the likely nerve to have been injured and what
would be the examination ndings?
e common peroneal nerve leaves the popliteal fossa and
winds round the neck of the bula where it is easily injured
from fractures of the bula. Injury leads to paralysis of the
muscles of the anterior and lateral compartments of the
calf. e patient will experience foot drop (foot is plantar
exed and pulled inwards (equinovarus). Sensory loss is
the anterior and lateral sides of the leg, dorsum of the foot
and toes, and the medial side of the hallux.
2. What other nerves are injured in fractures/dislocations?
Examples include:
• e axillary nerve can be injured by fractures of the
humerus and anterior dislocations of the shoulder.
• e radial nerve can be injured by fractures/disloca-
tions of the humerus, fractures of the spiral groove of
the humerus and fracture/dislocations of the radial
head.
• e ulnar nerve can be injured by fractures/disloca-
tions of the elbow.
• e median nerve is at risk of injury with supra-con-
dylar fractures.
• e sciatic nerve can be injured with fractures of the
pelvis.
• e obturator nerve can be injured by anterior dislo-
cations of the hip.
3. He is placed in a plaster-cast but just aer midnight the
nurse on the ward calls to tell you he is in tremendous
pain and his leg feels ‘odd’. What is the likely diagnosis
and what would be the treatment?
Pain of this magnitude following a severe lower limb fracture is likely to be compartment syndrome. Swelling of
the muscles of the lower limb compress the neurovascular structures in the calf, causing tingling and numbness,
pain on passive movement of the calf, and eventually
vascular compromise. It is a clinical diagnosis – the old
adage is ‘if you think its compartment syndrome then
treat it as compartment syndrome’. e treatment of this
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SECTION IV Appendix
is a surgical fasciotomy in which the four compartments
of the calf have their fascia opened via two incisions. A
medial incision to open the supercial and deep posterior compartments and a lateral incision for the lateral
and anterior compartments.
OSCE SCENARIO ANSWER 5.1
A 55-year-old female undergoes a right supercial parotidectomy for a pleomorphic adenoma of the parotid gland.
1. What is the order of structures traversing the gland
from without in?
From without in the structures are:
• the facial nerve
• the retromandibular vein, formed by the junction of
the supercial temporal and maxillary veins
• the external carotid artery, dividing at the level of
the neck of the mandible into its supercial temporal
and maxillary branches.
2. Name the divisions of the facial nerve within the gland.
ese are from above downwards:
• temporal
• zygomatic
• buccal
• mandibular
• cervical.
3. How would you test the integrity of the individual
branches of the facial nerve in the postoperative period
to exclude intraoperative damage?
• e temporal branch supplies frontalis. Ask the patient
to wrinkle the forehead by raising the eyebrows.
• e zygomatic branch supplies orbicularis oculi. Ask
the patient to close the eyes tightly and attempt to
open them against resistance.
• e buccal branch supplies buccinator and part of
orbicularis oris. Buccinator compresses the cheek, as
in the act of blowing, and allows the cheek to cave in,
as in the act of sucking. Test this by asking the patient
to whistle. Inability to whistle suggests damage to the
buccal branch.
• e marginal mandibular branch supplies the mus-
cles around the mouth, including orbicularis oris.
ere will be drooping of the mouth on the aected
side and inability to smile. Ask the patient to smile –
the lips do not separate on the aected side. is
branch is the thinnest and has the longest course
through the parotid, and therefore is most likely to
be injured.
• e cervical branch supplies platysma. Ask the
patient to pull down the corners of the mouth. e
patient will be unable to do this on the aected
side.
4. What is Frey’s syndrome? Explain its anatomical basis.
• Frey’s syndrome (gustatory sweating) is redness and
sweating on the face adjacent to the parotid gland
precipitated by eating (or anything else which precipitates salivation).
• It is caused by damage to the auriculotemporal nerve
at the time of surgery. e auriculotemporal nerve provides both parasympathetic innervation to the parotid
gland and sympathetic innervation to the sweat glands
and subcutaneous vessels. Damage to the auriculotemporal nerve results in aberrant regeneration of parasympathetic secretomotor bres, which grow along the
cut sympathetic nerve bres to the skin, blood vessels
and sweat glands. When the patient eats, activation of
the parasympathetic nerve bres produces sweating
and ushing.
OSCE SCENARIO ANSWER 5.2
A 50-year-old male presents to a general surgery clinic with a
lump in the right side of his neck.
1. What are the boundaries of the anterior and posterior
triangles of the neck?
• e boundaries of the anterior triangle of the neck are:
• the midline anteriorly
• the anterior border of sternocleidomastoid
posteriorly
• the lower margin of the mandible superiorly.
• e boundaries of the posterior triangle are:
• the posterior border of sternocleidomastoid
anteriorly
• the anterior border of trapezius posteriorly
• the middle third of the clavicle inferiorly.
Examination reveals that the lump is in the right posterior
triangle.
2. What are the possible dierential diagnoses?
Possible dierential diagnoses are:
• sebaceous cyst
• lipoma
• abscess
• lymph node
• cervical rib
• subclavian artery aneurysm.
On further examination you suspect lymphoma and discuss
the case with a haematologist. e haematologist requests
an excision biopsy. e lump lies centrally in the posterior
triangle.
3. What structure do you need to avoid at surgery and
what is the eect of injury to this structure?
• e spinal accessory nerve enters the posterior tri-
angle of the neck from behind the posterior border
of sternocleidomastoid at the junction of the upper
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