Lower Limb II

Question 1

A 63-year-old man in the surgical ward is complaining of numbness over the anterior thigh and medial aspect of his right leg. He is unable to extend his right knee and the knee jerk is reduced. He had undergone a femoral aneurysm repair three days ago.

Answer 1

Femoral nerve
The femoral nerve (L2 - 4) may be injured by surgeries to the femoral triangle (such as femoral embolectomy, femoro-popliteal bypass or femoral aneurysm repair), massive haematoma within the thigh, traction during surgery or any form of trauma, including gunshot wounds to the femoral triangle.

Injury to the femoral nerve causes weakness of the quadriceps muscle causing a weak knee extension. The knee may give way on walking and the patient has difficulty climbing stairs. There is numbness over the anterior thigh and medial aspect of the leg. The knee jerk is reduced or absent.

Question 2

A 33-year-old lady, who is 38 weeks pregnant, presents to her general practitioner with a four week history of pain and paraesthesia over the upper outer aspect of her right thigh. There is no restriction of movements in her hips or knees and her gait is normal.

Answer 2

Lateral cutaneous nerve of thigh
The lateral cutaneous nerve of the thigh may be compressed in pregnancy or any condition which causes pressure on this nerve such as injuries in the region of the anterior superior iliac spine or the inguinal ligament. Also known as meralgia paraesthetica, it is a form of entrapment neuropathy. Patients with this disorder present with pain, paraesthesia and sensory loss over the upper, lateral aspect of the thigh. No treatment is necessary as the condition is often self-limiting.

Question 3

A 71-year-old woman presents to the orthopaedic outpatient clinic with left-sided foot drop and altered sensation below the lateral side of the knee. There is loss of knee flexion and absent ankle jerk. She had undergone left total hip replacement six weeks ago.

Answer 3

Sciatic nerve
The sciatic nerve (L4-S3) may be injured following surgery (such as total hip replacement), dislocation of the hip, trauma (high speed road traffic accidents causing posterior dislocation of the hip) and other traction injuries to the nerve. Complete lesion of the sciatic nerve will affect all the muscles below the knee leading to loss of knee flexion, foot drop and an inability to walk. The patient is unable to stand for prolonged periods and is often found to drag his/her feet behind. There is loss of sensation below the knee on the lateral side (saphenous nerve supplies the medial side). The knee jerk is normal (supplied by the femoral nerve) but the ankle jerk is lost. There may be calf muscle wasting in the long term.

Question 4

A 68-year-old gentleman is about to undergo surgery for a popliteal artery aneurysm.
Which of the following structures is the supero-lateral border of the popliteal fossa?
(Please select 1 option)
Lateral head of gastrocnemius
Medial head of gastrocnemius
Sartorius
Tendon of biceps femoris
Tendons of semimembranous and semitendinosus

Answer 4

Tendon of biceps femoris

The polpiteal fossa lies behind the knee.

Its borders are

Superolateral - tenodon of biceps femoris
Superomedial - tendons of semimembranous and semitendinosus
Inferomedial - medial head of gastrocnemius
Inferolateral - lateral head of gastrocnemius.
The sartorius muscle attaches into the medial surface of the tibia.

Question 5

During a vascular examination of the lower limb you attempt to assess the presence of a femoral pulse.
What is the posterior relation of the femoral artery which you compress the artery against to feel its pulsation?
(Please select 1 option)
	 Femoral nerve
	 Iliac bone
	 Inguinal ligament
	 Psoas tendon
	 Symphysis pubis

Answer 5

Psoas tendon

The femoral artery can be palpated at the mid inguinal point. This is half way between the anterior superior iliac spine and the pubic symphysis.

The femoral artery’s lateral relation is the femoral nerve and its medial relation is the femoral vein. Its posterior relation is the psoas tendon.

The femoral artery is the continuation of the external iliac artery. It passes through the femoral triangle, giving off the deep femoral artery, and then enters the adductor canal.

It enters the popliteal fossa and becomes the popliteal artery.

Question 6

A 59-year-old man who works as a window cleaner falls from a ladder and sustains a fracture of his calcaneum.
It is decided that the fracture is best treated surgically. During surgery, an incision is made almost to the lateral malleoli.
Which structure would you expect to see appearing behind the malleoli?
(Please select 1 option)
Flexor digitorum longus tendon
Peroneus longus tendon
Posterior tibial artery
Peroneal nerve
Tibialis posterior tendon

Answer 6

Peroneus longus tendon

The structures passing behind the lateral malleoli are the tendons of peroneus longus and brevis.

Structures passing the medial malleolus are (nearest to malleolus first):

Tibialis posterior tendon
Flexor digitorum longus tendon
Posterior tibital artery
Vein
Nerve
Flexor hallucis longus tendon.

Question 7

Your consultant is in the coffee room and has left you operating on a patient with varicose veins caused by sapheno-femoral junction insufficiency.
Where should you make the skin incision so that you are over the sapheno-femoral junction?
(Please select 1 option)
3 cm below and lateral to the pubic tubercle
3 cm below and medial to the pubic tubercle
Anterior to the medial malleolus
Halfway between the pubic symphysis and the ASIS
Halfway between the pubic tubercle and the ASIS

Answer 7

3 cm below and lateral to the pubic tubercle

The surface marking of the sapheno-femoral junction is 2 to 3 cm below and lateral to the pubic tubercle.

The saphenous vein and femoral vein can be differentiated at surgery because the saphenous vein receives tributaries (superficial and deep external pudendal veins, superficial inferior epigastric vein and superficial inferior epigastria vein).

The saphenous vein runs anterior to the medial malleolus and is an important site for emergency venous access.

The mid inguinal point occurs halfway between the pubic symphysis and the ASIS and the mid point of the inguinal ligament halfway between the pubic tubercle and the ASIS.

Question 8

You are examining the knee of a patient complaining of pain behind his knee. You identify a prominent structure forming the medial boundary of the upper part of the popliteal fossa.

Answer 8

Semimembranosus
The popliteal fossa is a rhomboid shaped anatomical space. The upper boundaries of the popliteal fossa are the biceps tendon laterally and semimembranosus and semitendinosus medially. The inferior boundaries of the popliteal fossa are formed by the heads of the gastrocnemius which are less easily identified on palpation.

Question 9

You are exploring the popliteal fossa for a stab wound. You identify a structure that runs across the lateral aspect of the neck of the fibula.

Answer 9

Common peroneal nerve

The common peroneal nerve can be found on deep palpation of the lateral aspect of the head of the fibula and is particularly vulnerable to injury at the site.

Question 10

A 45-year-old man presents with lower back pain. On examination the ankle jerk is absent.

Answer 10

S1
Lumbar intervertebral disc protrusion is common.

Disc protrusion can exert pressure on a nerve root or roots.

Question 11

A 39-year-old female presents with lower back pain and numbness over the lateral side of one foot.

Answer 11

S1
Prolapse of the L5/S1 disc results in pressure effects on the first sacral nerve causing numbness of the lateral side of the foot and a reduced or absent ankle jerk.

Question 12

A 50-year-old man presents with lower back pain. On examination you find that he has reduced right ankle dorsiflexion and reduced sensation over the lower and lateral part of the right leg and the inside of the right foot.

Answer 12

L5
Prolapse of the L4/5 disc results in pressure effects on the root of the fifth lumbar nerve. This causes weak ankle dorsiflexion and numbness over the lower and lateral part of the leg and medial part of the foot.

Question 13

A motorcyclist is involved in an RTA and sustains a closed fracture of his left tibia. This is stabilised with an external fixator.
You are called to see him some hours later because of unbearable pain in his leg. You use a manometer to measure the pressures in his muscle compartments and the reading in the extensor compartment is 40 mmHg. He is taken to theatre for emergency fasciotomy.
Which of the following would you encounter in the extensor compartment?
(Please select 1 option)
Deep peroneal nerve
Peroneus brevis
Peroneus longus
Sural nerve
Tibial nerve

Answer 13

Deep peroneal nerve

The contents of the extensor compartment are

The deep peroneal nerve
The anterior tibial artery
Four muscles (tibialis anterior, extensor hallucis longus, extensor digitorum longus and peroneus tertius).
The sural and tibial nerves are found in the posterior compartment and peroneus brevis and longus in the lateral compartment.

Question 14

From the options below, please state the first structure that will be encountered when the popliteal fossa is opened whilst performing a surgery in this region:
(Please select 1 option)
	 Common peroneal nerve
	 Popliteal artery
	 Popliteal vein
	 Posterior femoral cutaneous nerve
	 Sural nerve

Answer 14

Sural nerve This is the correct answerThis is the correct answer
Popliteal fossa is a diamond-shaped region posterior to the knee.

It is bounded

Superomedially by semimembranosus and semitendinosus muscles
Superolaterally by the biceps femoris muscle, and
Inferolaterally and inferomedially by the lateral and medial heads of the gastrocnemius muscle respectively.
The fossa is covered by the popliteal fascia, which is perforated by the short saphenous vein and the sural nerve.

The sural nerve is the most superficial structure and thus most likely to be encountered when the popliteal fossa is explored during surgery.

The important contents of the fossa include

The popliteal artery and vein
Tibial and common peroneal nerves
Short saphenous vein 
The sural nerve
Posterior femoral cutaneous nerve, and
The obturator nerve.

Question 15

You are an orthopaedic SHO in clinic. Your consultant, realising that you are about to sit your examinations, calls you in to see a patient he has just seen.
The patient has sustained an injury to a nerve in his lower limb some time ago. When you examine the patient in front of your consultant, you note loss of muscle bulk in the anterior and lateral compartments of the affected leg. There is loss of ankle dorsiflexion and toe extension. The foot itself looks normal.
Which is the affected nerve?
(Please select 1 option)
	 Femoral nerve
	 Peroneal nerve
	 Popliteal nerve
	 Sciatic nerve
	 Tibial nerve

Answer 15

Peroneal nerve

The palsy described is characteristic of the peroneal nerve. If you asked the patient to walk you may have seen the patient walk with a high stepping gait.

The peroneal nerve is a branch of the sciatic nerve. Its motor distibution is to the muscles of the anterior compartment via its deep branch (extensor hallucis longus, extensor digitorum longus, extensor digitorum brevis, tibialis anterior and peroneus tertius) and to the lateral compartment via its superficial branch (peroneus brevis and longus).

Question 16

Which of the following is true regarding the femoral artery?
(Please select 1 option)
Is a branch of the internal iliac artery
Is crossed anteriorly by the medial cutaneous nerve of the thigh
Lies lateral to iliopsoas
Lies medial to the femoral vein
Lies medial to the lymphatic vessels

Answer 16

Is crossed anteriorly by the medial cutaneous nerve of the thigh

The femoral triangle contains from medial to lateral, the femoral vein, artery and nerve.

The triangle is formed

Laterally by sartorius
The inguinal ligament superiorly and
The adductor longus medially.
The roof of the triangle are the superficial structures, namely

The fascia lata
Cribiform fascia
Subcutaneous tissue 
The skin.
The floor is muscular and is formed, from medial to lateral, by

The adductor longus
Part of the adductor brevis
The pectineus 
The iliopsoas.
The femoral vessels are enclosed in the femoral sheath with the femoral nerve lying outside the sheath.

Medial to the femoral vein within the sheath is the femoral canal, an area of dead space into which the vein can expand during increased venous return.

The femoral artery is a continuation of the external iliac artery. It exits in the triangle via the apex and enters the subsartorial (Hunter’s) canal.

The femoral artery lies at the midinguinal point, which is midway between the pubic symphysis and anterior superior iliac spine.

Question 17

Deep to the inguinal ligament which of the following is correct?
(Please select 1 option)
Pectineus arises from the posterior pubic ramus
The capsule of the hip joint lies beneath the iliopsoas
The femoral artery lies lateral to the femoral nerve
The femoral nerve lies within the femoral sheath
The psoas muscle is supplied by the femoral nerve

Answer 17

The capsule of the hip joint lies beneath the iliopsoas

Amongst many other reasons the relations of the inguinal ligament are important in determining the origin of hernias.

The inguinal ligament is the thickened lower border of the aponeurosis of the external oblique. It extends from the anterior superior iliac spine to the pubic tubercle in a curved line which folds posteriorly. Its medial attachment forms a narrow sling for support of the spermatic cord or round ligament of the uterus.

The femoral artery lies at the mid-inguinal point and above the capsule of the hip joint beneath iliopsoas.

The psoas is supplied by segmental branches from the lumbar plexus.

Pectineus arises from the superior ramus of the pubis.

Question 18

Which of the following is correct regarding the obturator nerve?
(Please select 1 option)
Emerges from the lateral border of psoas major
Has a branch separated by adductor brevis
Is formed from the posterior divisions of second, third and fourth lumbar nerves
Lies below the obturator artery in the obturator foramen
Supplies the lateral margin of the knee

Answer 18

Has a branch separated by adductor brevis

“The obturator nerve arises from the ventral divisions of the second, third, and fourth lumbar nerves; the branch from the third is the largest, while that from the second is often very small.”

Question 19

A complete division of the femoral nerve results in which of the following?
(Please select 1 option)
Failure of adduction of the thigh at the hip joint
Failure of the knee extension
Foot drop
Paraesthesia of the lateral aspect of the foot
Sensory loss over the lateral part of the lower leg

Answer 19

Failure of the knee extension

The femoral nerve is the largest branch of the lumbar plexus and arises from L2/3/4.

The common peroneal nerve (a branch of the sciatic nerve) is relatively unprotected as it winds its way round the lateral aspect of the head of fibula and if stretched or damaged results in foot drop.

The lateral aspect of the foot is supplied by the sural nerve, S1/2, as a branch of the common peroneal nerve.

The posterior division of the femoral nerve supplies the saphenous nerve (l3/4), supplying sensation to the medial aspect of the calf and branches to the quadriceps femoris and knee joint.

The obturator nerve supplies the hip joint.

Question 20

Which of the following reflexes and innervating spinal segments is correctly paired?
(Please select 1 option)
	 Anal reflex - S1
	 Ankle jerk - L5
	 Biceps jerk - C7 and 8
	 Knee jerk - L3 and 4
	 Triceps jerk - T1

Answer 20

Knee jerk - L3 and 4

With reflexes, once again this is something that must be learnt ‘off by heart’.

The common reflexes asked for in an exam are:

Biceps C5/6
Triceps C7
Finger jerk C8
Knee jerk L3/4
Ankle jerk S1
Anal reflex S4/5.
The anal reflex is elicited by lightly scratching the perianal skin. In normal circumstances, the external anal sphincter contracts.

Question 21

Which of the following is not true of the relations of the anterior tibial artery?
(Please select 1 option)
Accompanied by an anterior tibial vein on either side as it descends
Descends on the interosseous membrane
Descends through the extensor compartment of the leg
The deep peroneal nerve runs on its lateral side proximally
Tibialis anterior lies laterally

Answer 21

Tibialis anterior lies laterally This is the correct answerThis is the correct answer
The anterior tibial artery is formed by the bifurcation of the popliteal artery in the calf, which passes forwards above the upper border of the interosseous membrane to reach the extensor compartment.

The artery with both of its veins run inferiorly on the interosseous membrane and passes between the two malleoli anteriorly to become the dorsalis pedis.

Tibialis anterior lies medial to the artery throughout.

Extensor digitorum longus and peroneus tertius lie laterally.

The deep peroneal nerve runs laterally initially and then passes in front in the middle third.

Question 22

Trendelenburg test

Answer 22

Trendelenburg test: This test is performed with the patient standing. The patient is asked to raise one leg; the test is positive if the hip on the raised side drops. A positive test suggests weakness of the abductors of the other hip. Ober’s tests for tight iliotibial band. The Thomas test, is for tight hip flexors. Barlow and Ortolani tests can be used in combination at birth and can elicit a dislocated hip, assess its reducibility and diagnose an unstable hip which is dislocatable.

Question 23

positive Lachman test.What is the origin and insertion of the damaged ligament?

Answer 23

The anterior cruciate ligament is attached to the anterior intercondylar area of the tibia and passes upwards, backwards and laterally to the medial surface of the lateral femoral condyle. The posterior cruciate ligament is attached to the posterior intercondylar area of the tibia and passes upwards, forwards and medially to the lateral surface of the medial femoral condyle. Both cruciate ligaments are intracapsular but extrasynovial. The medial meniscus is attached to the medial collateral ligament but the lateral collateral ligament is not attached to the lateral meniscus as the popliteus muscle runs between them.

Question 24

Compartment syndrome

Answer 24

Compartment syndrome, a devastating early complication of lower limb fractures, occurs when the capillary perfusion pressure falls below the tissue perfusion pressure. This leads to necrosis of the muscles and nerves in the enclosed compartment. Up to 45% of all cases of compartment syndrome are caused by tibial fractures. It is more common in patients with open tibial fractures compared to closed tibial fractures (6% vs 1.2%), probably reflecting the severity of the injury. Although commonly caused by trauma, it can also occur following crush injury, massive haemorrhage, gun shot injuries, deep burns, electrical injuries, restricting tourniquets and fluid extravasation; chronic compartment syndrome has been reported following splints, casts and dressings, military antishock trousers, drug/alcohol abuse, coma, gastrocnemius or peroneus muscle tear and snake envenomation. Peripheral pulses including the dorsalis pedis and posterior tibial are normal during the early phases of development of compartment syndrome (since it is the microvasculature which is initially affected); loss of peripheral pulses is usually a late and sinister sign that suggests imminent tissue ischaemia. The most significant and reliable clinical sign, however, is severe pain in response to passive stretch of the ischaemic muscles. Pain is deep and aching in nature. The sensory nerve fibres are more susceptible to ischaemia than the motor fibres and hence there is loss of sensation before paralysis of the affected group of muscles. All muscles in the lower leg tolerate 4 h of ischemia well, but by 8 h the damage is often irreversible. Areas of muscle may infarct giving rise to rhabdomyolysis, hyperphosphataemia, hyperkalaemia, high uric acid levels and metabolic acidosis; acute renal failure is a well-recognised complication of untreated compartment syndrome. Many surgeons now use compartment pressures in excess of 30–35 mmHg in a normally perfused patient as an indication for open compartment fasciotomy. However, in a haemodynamically unstable or a shocked patient, a lower threshold is indicated: Fasciotomy should be undertaken if the difference between the diastolic pressure and the measured compartment pressure is less than 30 mmHg (eg, if the diastolic pressure falls to 50 mmHg, fasciotomy should be undertaken even if the compartment pressure is only 20 mmHg

Question 25

male presents with pain radiating down the leg, worse in the anterior leg distal to the knee. On physical exam, he is unable to extend his knee and his patellar reflex is absent

Answer 25

Lesions affecting L3/4 also result in a decreased knee reflex, and sensory loss over the anterior thigh and medial part of the leg. S1 lesions result in weak plantar flexion, loss of ankle reflex and sensory loss over the sole of the foot. Common peroneal nerve injuries often occur from pressure from plaster casts and lateral knee ligament injuries. Superficial peroneal nerve injuries impair eversion but not dorsiflexion, as this action is subserved by the deep peroneal nerve

Question 26

displaced intracapsular fracture of neck of femur following a fall from a horse. What is the most common complication of this injury?

Answer 26

Posteriorly the capsule is attached half-way along the neck. The intertrochanteric crest lies posteriorly. A fracture of the neck of the femur causes lateral rotation of the thigh. The blood supply to the head of the femur passes through the retinacula on the neck. The obturator externus winds round the inferior aspect of the neck. Nonunion rate is around 20%, whereas AVN is about 30%

Question 27

The femoral triangle of Scarpa in the thigh contains some important structures

Answer 27

The femoral sheath is a downward continuation of the abdominal fascia about 2.5 cm below the inguinal ligament. It is believed to allow for femoral vessel movement in the inguinal region during movement of the hip. The mnemonic ‘NAVEL’ describes some of the key structures in this region (from lateral to medial): femoral nerve, artery, vein, empty space, lymphatics (Cloquet’s). Apart from the femoral nerve, that lies most laterally, all the other structures in the mnemonic are encased in the femoral sheath. The mentioned empty space and lymphatic compartments form the ‘femoral canal’, where femoral hernias may occur. Therefore, the femoral canal is in the most medial portion of the femoral sheath. The femoral ring is the abdominal opening into the femoral canal. At 2–3 cm below the inguinal ligament, the femoral sheath fuses with the adventitia of the femoral vessels. The pubic branch of the inferior epigastric artery replaces the obturator artery in about 30% of cases, and may be at risk in a femoral hernia repair.

Question 28

What is the positive left Trendelenburg test associated with?

Answer 28

The Trendelenburg test is used to assess stability of the hip. A positive Trendelenburg test is seen with any painful disorder of the hip. It is also present with a dislocated or subluxed hip and in other conditions where the proximal femoral anatomy is abnormal (short femoral neck with high riding trochanter). Weak abductor muscles will also lead to a positive test. The abductors of the hip include piriformis, gluteus medius and minimis. Pectineus adducts the hip. The other adductors of the hip are gracilis, and adductor longus, brevis and magnus.

Question 29

In the anatomy of the bony pelvis, several bony landmarks have important clinical relevance.

Answer 29

In the natal cleft, the sacral cornua are important surface markings for the sacral hiatus, through which a needle is passed for epidural anaesthesia. A direct inguinal hernia protrudes above and medial to the pubic tubercle. The external inguinal ring is palpable superolateral to the pubic tubercle. The femoral canal has the lacunar ligament as its medial wall. The ischial spine guides a needle to the pudendal canal for per vaginam pudendal nerve block. The transtubercular plane is an important landmark for lumbar puncture and transects the L5 vertebra (the supracristal plane, which passes through the L4 lumbar spine, can also be used).

Question 30

numb, swollen and blistered feet. What is the main cause of this trench foot condition?

Answer 30

Trench foot or cold immersion foot (or hand) is caused due to a non-freezing injury of the hands or feet. This is typically seen in soldiers, sailors, or fishermen, who are chronically exposed to wet conditions and temperatures just above freezing, i.e. 1.6°C to 10°C (35°F to 50°F). It occurs due to microvascular endothelial damage, stasis and vascular occlusion. Although the entire foot may appear black, deep tissue destruction may not be present. An alternating arterial vasospasm and vasodilatation occurs, with the affected tissue first cold and anaesthetic, progressing to hyperaemia in 24 to 48 h. This then leads to an intense painful burning and dysaesthesia, as well as tissue damage characterised by oedema, blistering, redness, ecchymosis, and ulcerations. Pruritic, red–purple skin lesions are a feature of chilblain or pernio. Complications of trench foot include local infection, cellulitis, lymphagitis, and gangrene.

Question 31

What are the contents of the popliteal fossa?

Answer 31

The roof of the popliteal fossa is formed by the fascia lata. Within the apex of the fossa the sciatic nerve divides into common peroneal and tibial branches (but may divide higher), the former lying either against or under the medial edge of the biceps femoris muscle. The deepest structure is the popliteal artery. The sural nerve pierces the deep fascia halfway down the leg. The roof is pierced by the short saphenous vein.

Question 32

Where does the scaphoid major blood supply come from?

Answer 32

The scaphoid articulates with the radius, and since it transmits weight from the hand to the radial head it is commonly fractured during falls. When the fracture line severs the blood supply to the proximal fragment, avascular necrosis of the latter is a common complication. Tenderness in the anatomical snuffbox is initially the only clinical sign of the fracture before radiological evidence of osteonecrosis develops (2 weeks later). The flexor retinaculum takes its origin from the tubercle of the scaphoid and ridge on the trapezium. The adductor pollicis muscle has an origin from the capitate, not the scaphoid and so adduction of the thumb is unimpaired and pain-free after scaphoid fracture

Question 33

What is the main branch of the posterior tibial artery

Answer 33

The popliteal artery divides into the anterior and posterior tibial arteries at the lower border of the popliteus muscle, anterior to the fibrous arch of the soleus muscle. The peroneal artery is the first branch of the posterior tibial artery. At the ankle joint, the posterior tibial artery passes deep to the flexor retinaculum

Question 34

What is the main cutaneous branch of the tibial nerve in the popliteal fossa?

Answer 34

The tibial nerve is the large terminal branch of the sciatic nerve. It runs through the popliteal fossa, at first lying on the lateral side, then crossing medial to the popliteal artery. It leaves the fossa by passing deep to gastrocnemius and soleus. The tibial nerve supplies the knee joint, popliteus, and the posterior compartment muscles of the leg and the foot