Foot and Ankle 2 Flashcards
Why do we use lines of measurements when assessing radiographs?
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.
When assessing a radiograph, the line of measurement for the foot is called the?
Heel pad thickness
When assessing a radiograph for the foot, what are the angulation measurements?
Böhler’s Angle
First Metatarsalphalangeal (MTP) Angle
What is heel pad thickness and how is it measured?
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.
What is the maximum heel pad thickness in Men?
Normal value is no more that 25mm
What is the maximum heel pad thickness in women?
Normal value is no more that 23mm
What is an increased heel pad thickness called?
Heel pad sign
Heel pad thickness can increase with what conditions?
Myxoedema (M)
Acromegaly (A)
Phenytoin Therapy (D) (D = drug)
Callus Formation (C)
Obesity (O)
Peripheral Oedema (P)
Use acronym for remembering is
MAD COP
What is Bohlers angle?
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.
What is the 1st Metatarsalphalangeal (MTP) Angle?
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
Name the Anatomical variants, congenital and acquired abnormalities
of the foot.
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)
What is a talar beak?
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.
How will a talar beak appear on an X-ray?
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.
What is tarsal coalition?
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.
How does tarsal coalition appear on an x-ray?
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.
What are accessory ossicles?
They are secondary ossification centres that remain separate from the adjacent bone.
How many accessory ossicles are there in the foot?
over 40
What is Os Trigonum?
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.
What is Os Peroneum?
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.
What is Os Supranaviculare?
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.
What is Accessory Navicular?
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)
What is Hallux Valgus?
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.
What causes Hallux Valgus?
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
How is Hallux Valgus displayed on an x-ray?
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
