Foot and Ankle 2

Question 1

Why do we use lines of measurements when assessing radiographs?

Answer 1

Remember, Lines of measurement are used to evaluate normal and abnormal skeletal relationships. We can detect subtle abnormalities avoiding misdiagnosis, and can compare 2 studies for regression or progression of a condition.

Question 2

When assessing a radiograph, the line of measurement for the foot is called the?

Answer 2

Heel pad thickness

Question 3

When assessing a radiograph for the foot, what are the angulation measurements?

Answer 3

Böhler’s Angle
First Metatarsalphalangeal (MTP) Angle

Question 4

What is heel pad thickness and how is it measured?

Answer 4

When we measure the heel pad thickness, we are measuring the thickness of the soft tissue on the heel. It is measured from the shortest distance between the plantar surface of the calcaneus to the external skin contour.

Question 5

What is the maximum heel pad thickness in Men?

Answer 5

Normal value is no more that 25mm

Question 6

What is the maximum heel pad thickness in women?

Answer 6

Normal value is no more that 23mm

Question 7

What is an increased heel pad thickness called?

Answer 7

Heel pad sign

Question 8

Heel pad thickness can increase with what conditions?

Answer 8

Myxoedema (M)
Acromegaly (A)
Phenytoin Therapy (D) (D = drug)
Callus Formation (C)
Obesity (O)
Peripheral Oedema (P)

Use acronym for remembering is
MAD COP

Question 9

What is Bohlers angle?

Answer 9

Bohlers angle is drawn on a lateral calcaneus, ankle or foot x-ray and measures the axial relationships of the calcaneus.
The three highest points of the superior surface of the calcaneus are connected by two tangential lines. The angle is formed posteriorly and is then assessed.
The angle can range from anywhere between 20 and 40degrees, however, anything below 28 degrees is considered abnormal.
The most common cause of an angle below 28 degrees is a calcaneal fracture. But it can also be affected by dysplastic development of the calcaneus.

Question 10

What is the 1st Metatarsalphalangeal (MTP) Angle?

Answer 10

The first metatarsalphalangel angle is used to check for Hallux Valgus.
The x-ray must be performed weight bearing before you can apply the angle of measurement.
It is the angle between the axis of the 1st metatarsal and the axis of the proximal phalanx of the 1st toe
A normal angle is anything less than 15°
A greater angle indicated Hallux Valgus

Question 11

Name the Anatomical variants, congenital and acquired abnormalities
of the foot.

Answer 11

Talar Beak
Tarsal Coalition
Accessory Ossicles
Hallux Valgus
Sesamoid Bones
Symphalangism
Polydactyly
Pseudotumour
Calcaneal Spurs
Apophysis of proximal 5th MT
Calcaneal Apophysitis (Sever’s Disease)

Question 12

What is a talar beak?

Answer 12

A Talar beak is a superior projection of the distal aspect of the talus, it points upwards. It is thought to be caused by the abnormal biomechanical issues of the talonavicular joint – at the insertion site of the talonavicular ligament, a periosteal reaction develops.
Clinically, a talar beak is usually asymptomatic and only present in about 1% of the population. It can be mistaken for osteophytic change at the talonavicular joint due to osteoarthritis.

Question 13

How will a talar beak appear on an X-ray?

Answer 13

On an x-ray, you will see a superior bony protrusion from the distal aspect of the talus with the cortex continuous with the talus tarsal bone. The bony matrix will appear normal. The presence of a talar beak is usually present with tarsal coalition.

Question 14

What is tarsal coalition?

Answer 14

Tarsal coalition is an abnormal connection that develops between two tarsal bones. Similar to carpal coalition in the wrist; the connection can be bony., cartilaginous or fibrous.
Tarsal coalition can occur during foetal development, meaning it can be congenital, or it can be acquired through infection, trauma or arthritis.
The most common coalitions to occur in the tarsal are the calcaneus and the navicular - calcaneonavicular, and the talus and the calcaneus – talocalcaneal coalition.
Tarsal coalition is usually asymptomatic and is bilateral in 50% of the cases.
If it is symptomatic, it typically won’t present before the age of 9 years; the symptoms include reduced range of motion; pain; flatfoot and limping.

Question 15

How does tarsal coalition appear on an x-ray?

Answer 15

On an x-ray, when there is bony coalition we will see the medullary cavity is continuous between the two coalesced bones. In a fibrous coalition there will be irregularity and narrowing of the bony interfaces typicaly with associated sclerosis either side of the joint margin.
In a non-osseus coalition we can see subchondral reactive bony changes, adjacent marrow oedema (on magnetic resonance imaging), an unusual articular orientation and loss of joint space.

Question 16

What are accessory ossicles?

Answer 16

They are secondary ossification centres that remain separate from the adjacent bone.

Question 17

How many accessory ossicles are there in the foot?

Answer 17

over 40

Question 18

What is Os Trigonum?

Answer 18

Os Trigonum is a secondary ossification centre that represents the failure of fusion of the lateral tubercle of the posterior process.
It is located posterior to the talus on a lateral ankle, foot or calcaneus x-ray.
The centre should be fused by age 17, if it fails to, then the ossicle trigonum is left. This accessory ossicle can be present in about 7% of adults and bilateral in about 2% of individuals. Literature has shown that os trigonum can be a cause of posterior ankle impingement syndrome. Common in ballet dancers and those who perform repetitive ankle plantarflexion can experience this unilateral posterior ankle pain due to compression of the posterior structures.
Possible differential diagnoses for os trigonum could be a Shepherd fracture – an avulasion fracture of the lateral tubercle of the talus, or a fracture of the Stieda process.

Question 19

What is Os Peroneum?

Answer 19

Os peroneum is a secondary ossification centre located on the lateral plantar aspect of the cuboid bone. Remember the cuboid is a tarsal bone on the lateral aspect of the foot.
Os peroneum sits in the tendon of the fibularis Longus, hence it’s location and is a very commonanatomical variant; it is seen in up to 26% of feet.
As it is an accessory ossicle, it can be congenital, of caused by trauma or degenerative disease.
Os Peroneum is best visualised on a Medial Oblique Foot projection, and if we were to describe it’s appearance, we would say it was small, round bony structure with smooth cortical margins lateral to the cuboid.
Os peroneum can produce pathology, including Os peroneum syndrome.
Os peroneum syndrome refers to a wide range of conditions that cause lateral foot pain. It can result in tenosynovitis and/or disruption of theperoneus longus tendon.

Question 20

What is Os Supranaviculare?

Answer 20

Os Supranaviculare is an accessory ossicle located on the anterior aspect of the navicular. It is typically close to the talonavicular joint (where the talus and navicular articulate with each other).
It is not very common, as is present in about 1% of the population. It is also known as Piries Bone.
An accessory ossicle can be congenital of caused by trauma or degenerative disease.
Os supranaviculare is typically visualosed on a lateral foot or ankle x-ray projection, and we would describe it’s appearance as a smooth round bony structure with smooth cortical margins at the superior-dorsal (or anterior) aspect of the navicular bone (as it is in the x-ray image on this slide).
This ossicle can mimic an avulsion fracture, but by checking the cortical margins and alignment of the ossicle, we can differentiate it from a fracture.

Question 21

What is Accessory Navicular?

Answer 21

Accessory navicular is a large accessory ossicle that is located next to the medial aspect of the navicular ( the navicular bone is located on the medial aspect of the foot)
The fibularis longus tendon will insert onto the ossicle if present, and it’s usually asymptomatic. If there has been traction between the navicular and the ossicle, it may cause medial foot pain and tendinosis (best seen on an MRI).
This accessory ossicle is relatively common, it is present in approximately 10% of the population, and is more common in female patients.
The ossicle typically appears during adolescence (teenage years) and there are 3 types.
Type 1 accessory navicular bone (os tibiale externum)
Type 2 accessory navicular bone
Type 3 accessory navicular bone (Cornuate navicular)

Question 22

What is Hallux Valgus?

Answer 22

Hallux Valgus is a progressive foot deformity with soft tissue and bony prominence medially. The first metatarsophalangeal joint of the big toe is Abducted. This causes lateral deviation or subluxation of the 1st proximal phalanx, and the sesamoid bones of the hallux (hallux refers to the big toe) are also laterally subluxed, as you can see in the x-ray image.

Question 23

What causes Hallux Valgus?

Answer 23

There are many potential causes of hallux valgus; these include sex – it is 10 times more common in females; congenital reasons; chronic Achilles tightness and severe flatfoot.
We can diagnose hallux valgus without taking an x-ray; we can observe the deviation of the big toe. However, on an x-ray we can measure and diagnose more accurately

Question 24

How is Hallux Valgus displayed on an x-ray?

Answer 24

1st MTP angle >15 ͦ ; lateral subluxation of the base of the 1st Prox. Phalanx; lateral subluxation of 1st digit sesamoid bones; 2 ͦ OA of 1st MTP joint; ST swelling medial to 1st MTP

Question 25

How is Hallux Valgus displayed on an x-ray?

Answer 25

1st MTP angle >15 ͦ ; lateral subluxation of the base of the 1st Prox. Phalanx; lateral subluxation of 1st digit sesamoid bones; 2 ͦ OA of 1st MTP joint; ST swelling medial to 1st MTP

Question 26

What is a sesamoid bone?

Answer 26

Bone embedded within a tendon or muscle
Helps modify pressure, diminish friction, help alter direction of muscle pull, smooth surface for tendons

Question 27

What does Hallux mean?

Answer 27

Big toe

Question 28

What are a commonly seenanatomical variant, present in up to 1/3 ofhallux sesamoids?

Answer 28

Multipartite hallux sesamoids

Question 29

What is symphalangism?

Answer 29

Ankylosis of the interphalangeal joints (fusion)
Stiffness of the joints, lack of skin folds, reduced range of movement
M/C seen as an isolated anatomical variant as a fusion of the middle and distal phalanges in the 5th toe

Question 30

What is polydactyly?

Answer 30

Polydactylyrefers to the situation where there are more than the usual number of digits (five) in a hand or foot – Poly means many, and dactyl refers to digits.
It can be broadly classified as:
preaxial polydactyly: extra digit(s) towards the thumb/hallux
postaxial polydactyly: extra digit(s) towards little finger/toe

Question 31

What is a pseudotumour?

Answer 31

Pseudotumours are common findings in the calcaneus also. A calcaneal pseudotunour is an anatomical variant that mimics a bone lesion on an x-ray image.
They are caused by rarefaction of the normal trabecular pattern; the trabecular rarefaction is a low stress area of bone that becomes apparent when it is surrounded by more prominent higher stress areas. So rarefaction means lessening of density, in this case, the decreased density of the trabecula bone in the area.
Pseudo tumour of the calcaneus is classed as a Do not touch lesion = it does not require further investigation as it is clear on the x ray. The pseudotumour of the calcaneus is a lesion that is real but obviously benign.

Question 32

What is a calcaneal spur?

Answer 32

A calcaneal spur is the formation of an osteophyte at the insertion sites of the plantar aponeurosis and the Achilles tendon.
It is typically seen in older males and females and is thought to be related with osteoarthritis, obesity or previous heel pain.
Unfortunately, the exact pathophysiology, or cause, is unknown, but there are some theories about.
On an x-ray, a calcaneal spur appears as a bony projection from either the plantar aspect of the calcaneus (if associated with he plantar aponeurosis) or on the posterosuperior aspect of the calcaneus (if associated with the Achilles Tendon insertion). The cortex and matrix are continuous with the rest of the calcaneal bone.
Very rarely, calcaneal spurs can fracture, but they’re commonly associated with conditions such as plantar fasciitis, reactive and psoriatic arthritis.

Question 33

What is apophysis of the proximal 5th MT?

Answer 33

A normal anatomical variant we may see on an x-ray of the foot is the apophysis of the proximal 5th metatarsal. The apophysis is a normal developmental outgrowth of a bone which arises from a separate ossification centre, and fuses to the bone lateral in development.
In this location, the apophysis can easily be mistake for os peroneum or an avulsion fracture of the base of the 5th metatarsal.
To differentiate between them: the apophysis lies laterally and is orientated longitudinally parallel to the shaft. A fracture is typically extraarticular (occurs outside the joint capsule) and is orientated transversely as you can see in the first of the x-ray images on the slide.
We will typically see the apophysis on a plain film x-ray between 10 and 12 years of age, and fusion of the apophysis to the metatarsal base occurs within the next 2-4 years.

Question 34

What is Calcaneal Apophysitis (Sever’s Disease)?

Answer 34

Calcaneal apophysitis is a painful inflammation of the heel’s growth plate. It typically affects children between the ages of 8 and 14 years old, because the heel bone (calcaneus) is not fully developed until at least age 14. Until then, new bone is forming at the growth plate (physis), a weak area located at the back of the heel. When there is too much repetitive stress on the growth plate, inflammation can develop. Also called Sever’s disease, this is not s “true” disease.
Overuse and stress on the heel bone through participation in sports is a major cause of calcaneal apophysitis. The heel’s growth plate is sensitive to repeated running and pounding on hard surfaces, resulting in muscle strain and inflamed tissue.
If you look at the x-ray image, you will see the calcaneal apophysis is more dense (appears whiter) compared to the main part of the calcaneus. There may also be loss of the fat or soft tissue planes indicating inflammation.