27.6.2: Osteochondral fragmentation and OCD

Question 1

Osteochondrosis

Answer 1

failure of endochondral ossification

Question 2

Osteochondrosis dissecans

Answer 2

the ultimate result of osteochondrosis; we call it OCD when pathology progresses to ostechondral fragmentation

Question 3

Cause of osteochondrosis in horses

Answer 3

• Multifactorial
• Focal failure of endochondral ossification (epiphyseal or metaphyseal growth cartilage)
• Polygenetic heritable disease

Question 4

What defect is visible here? What breeds is it most commonly seen in?

Answer 4

• Circled = radiolucent defect
• The fragment is not visible but could be made of cartilage
• This is avulsion fragmentation from short sesamoidean ligaments
• Occurs on the palmar/plantar aspect of P1
• Seen in Warmbloods and Standardbreds

Question 5

What defect is visible here? Which horses do we see this in?

Answer 5

• Defect on the dorsoproximal aspect of P1/ dorsal margin of proximal P1
• Occurs due to overextension of fetlock at high speed/ sometimes trauma suspected -> repetitive impact of dorsal P1 eminences
• Seen in racehorses

Question 6

Where is the fragment? What kind of horse would you expect this injury in?

Answer 6

• Fragment is on the dorsal margin of P1
• Seen in racehorses

Question 7

Which of the following is often the presenting complaint of a horse with osteochondrosis?
* Lameness
* Lies down more
* Bucks under saddle
* Joint effusion

Answer 7

Joint effusion

Question 8

What are the most common sites of OCD in the forelimb?

Answer 8

Shoulder
Fetlock

Question 9

What are the most common sites of OCD in the hindlimb?

Answer 9

• Stifle
• Hock
• Fetlock

Question 10

What lesion is visible at Site 1?

Answer 10

This is a DIRT lesion (distal intermediate ridge of tibia)
This is a common site for osteochondrosis lesions.

Question 11

Which trochlear ridge of the talus is abnormal is this image? (Site 2)
a) medial
b) lateral

Answer 11

b) lateral trochlear ridge of talus is abnormal

Question 12

Which view is shown here and what is the pathology?

Answer 12

View: dorsoplantar
Pathology: osteochondrosis of the medial malleolus of the tibia

Question 13

True/false: this is normal.

Answer 13

False
The sagittal ridge of the distant metacarpus is affected

Question 14

Which view is shown here?

Answer 14

This is a flexed lateromedial metacarpophalangeal / flexed metatarsophalangeal view

Question 15

Which view is being taken here? Which joint is being imaged? What is the most common site of OCD in this joint?

Answer 15

• This is a lateromedial view of the stifle
• Specifically, we are imaging the femoropatellar joint
• The most common site of OCD in the stifle is the lateral trochlear ridge of the femur

Question 16

Which joint is being imaged here? What pathology is present?

Answer 16

• Femorotibial joint
• There is a subchondral cyst-like lesion in the medial femoral condyle

Question 17

You suspect a fragment on the palmar/ plantar surface of the joint (metacarpo/metatarsophalangeal joint). What views will you take?

Answer 17

• Dorsopalmar
• Lateromedial (make this one good and fragment may be visible)
• Obliques with special angles (not day 1)

Question 18

You suspect a fragment on the dorsal surface of the metacarpophalangeal joint. What imaging will you perform?

Answer 18

Radiography
* Dorsal 60 medial-palmarolateral oblique (DMPLO)
* Dorsal 60 lateral-palmaromedial oblique (DLPMO)

If still not sure -> ultrasound

Question 19

What radiographic view will you take to assess OCD in the tarsus?

Answer 19

• DP (slightly modified)
• LM
• DMPLO (slightly modified)
• DLPMO

Question 20

Diagnostic approach to osteochondrosis / osteochondral fragmentation

Answer 20

• Physical exam
• Lameness exam: flexions, reactions to intra-articular blocks
• Radiographs: certain view for each joint/ condition

Question 21

Answer 21

Joint effusion in the stifle

Question 22

You suspect OCD in the fetlock. Which radiographic views will you take?

Answer 22

• DP
• LM
• ± Flexed LM
• DMPLO
• DLPMO

Question 23

What view is this?

Answer 23

• DMPLO
• The sesamoid is always palmar in the limb
• The fragment therefore has to be palmar
• We have highlighted the fragment

Question 24

What views do you want to take when imaging the stifle for OCD?

Answer 24

• LM
• Caudo-cranial
• Caudolateral-craniomedial oblique

Question 25

Which view is this? How can we tell the medial and lateral trochlear ridges apart?

Answer 25

Question 26

Which view is being taken here? What does it highlight?

Answer 26

Question 27

Which view is being taken here? What does it highlight?

Answer 27

Question 28

Which view is shown here? What does it highlight?

Answer 28

Question 29

If we have OCD, should we remove the fragment, or leave it there?

Answer 29

Remove the fragment

Question 30

If we have a fragment on the dorsal surface of P1, should we remove the fragment, or leave it there?

Answer 30

Remove the fragment

Question 31

If we have a fragment on the palmar/ plantar aspect of P1, should we remove the fragment, or leave it there?

Answer 31

• Only remove the fragment if the horse is working at high speed
• If embedded in the sesamoidean ligament, can leave it as it is unlikely to cause future problems

Question 32

Conservative treatment of OCD/ osteochondral fragmentation

Answer 32

• Box rest/ small paddock
• Joint injection with corticosteroids -> for subchondral cyst-like lesions
• Remember the 5 month mark (hock) and 8 month mark (stifle) - lesions may go away by themselves

Question 33

This is the distal femur. Which is lateral and which is medial?

Answer 33

Lateral trochlear ridge - main site of OCD in the femur

Question 34

True/false: some osteochondral lesions can disappear on their own.

Answer 34

True
* Tarsocrural (hock) joint -> lesions can disappear up to 5 months of age
* Femoropatellar (stifle) joint -> lesions can disappear up to 8 months of age