Musculoskeletal Disease Imaging

Osteochondrosis

developmental disorder seen in rapidly growing young animals when endochondral ossification fails at an articular surface, leaving cartilage that turns thick and prone to fracture or fragmentation

How does Osteochondrosis appear on radiographs?

as a defect in subchondral bone beneath the affected articular cartilage

Osteochondritis dissecans (OCD)

Osteochondrosis that has progressed to formation of a cartilage or mineralized flap/fragment

Radiographs will only show a Osteochondritis dissecans (OCD) cartilage flap if...

it contains enough mineralized subchondral bone

*A flap made entirely of cartilage may be invisible radiographically!

Four locations Osteochondrosis is commonly found in dogs:

1.) caudal humeral head

2.) medial humeral condyle

3.) femoral condyles

4.) talar trochlear ridges

Seven locations Osteochondrosis is commonly found in horses:

1.) medial femoral condyle

2.) lateral femoral trochlear ridge

3.) intermediate ridge of the tibia

4.) lateral talar trochlear ridge

5.) medial malleolus

6.) sagittal ridges of the distal third metacarpal/metatarsal bones

7.) cervical articular processes

Normal radiographic image of canine humeral head

smooth, continuously curved subchondral bone surface

Radiographic appearance of osteochondrosis of the canine humeral head

surface may become flattened or irregular, often with subchondral sclerosis underneath the lesion

If an osteochondrosis at the canine humeral head progresses to OCD, there will be a...

thin mineralized flap or separate mineral fragment visible

Radiographic appearance of osteochondrosis of the canine femoral condyle

produces an irregular, undulating, or concave lucent defect in the subchondral bone, often with surrounding subchondral sclerosis

One femoral condyle may remain smooth while the affected condyle has an irregular surface

Radiographic appearance of osteochondrosis of the canine talus

trochlear ridge of the talus may become flattened or blunted

tarsocrural joint space appears widened

Radiographic appearance of osteochondrosis of the equine medial femoral condyle

range from a smooth subchondral defect to a larger, expansile, cyst-like defect surrounded by sclerosis

commonly called osseous cyst-like lesions.

Radiographic appearance of osteochondrosis of the equine lateral trochlear ridge of the distal femur

Radiographic appearance of osteochondrosis of the equine intermediate ridge of the distal tibia

DMPLO view is particularly useful for highlighting this ridge!

Radiographic appearance of osteochondrosis of the equine lateral trochlear ridge of the talus

Three diseases under elbow dysplasia:

1.) ununited anconeal process (UAP)

2.) fragmented medial coronoid process (FCP)

3.) medial humeral OC (OCD)

elbow dysplasia results in joint ________

incongruity

ununited anconeal process (UAP)

failure of the anconeal process to fuse to the olecranon

What positioning of the elbow is best for visualizing ununited anconeal process (UAP)?

flexed lateral elbow

What does ununited anconeal process (UAP) look like radiographically?

a radiolucent line between the anconeal process and olecranon

fragmented medial coronoid process (FCP)

most common cause of elbow dysplasia!!

What does fragmented medial coronoid process (FCP) look like radiographically?

blunting of the medial coronoid process or a fragment

medial humeral OC (OCD)

concave defect in the subchondral bone with surrounding sclerosis

medial humeral OC (OCD) can occur with what other elbow dysplasia?

fragmented medial coronoid process (FCP)

Hip dysplasia

developmental malformation of the coxofemoral joint where head of femur slips out of acetabulum

In a normal hip, ____% of the femoral head should be covered by the acetabulum

50%

Radiographic findings of hip dysplasia

subluxation/luxation of the femoral head from the acetabulum

shallow acetabula

enthesophytes on femoral neck

osteophytes on femoral head and acetabulum

Five Congenital Diseases

1.) Panosteitis

2.) Hypertrophic osteodystrophy

3.) Craniomandibular osteopathy

4.) Avascular necrosis of the femoral head

5.) Femoral neck metaphyseal osteopathy

Panosteitis

inflammation of an entire bone; self limiting and cause unknown

What breed of dog is classically affected by Panosteitis? How old?

5-14 month old Germand Shepherds (or other large breed dogs)

Clinical signs of Panosteitis

shifting leg lameness with and pain with deep palpation of the affected bones

Panosteitis radiographic findings

patchy medullary sclerosis, often centered near the nutrient foramen

nutrient foramen

small opening in the diaphysis where an artery enters the bone to provide nourishment

Hypertrophic osteodystrophy

inflammatory condition of long bones which affects rapidly growing puppies

What region is hypertrophic osteodystrophy most often found?

distal antebrachium

What dogs are classically affected by Panosteitis? How old?

large breed puppies 3-6 months old

Radiographic findings of hypertrophic osteodystrophy

radiolucent line within the metaphysis adjacent to the physis

sclerosis of the surrounding metaphyseal bone

Severe/chronic hypertrophic osteodystrophy can cause...

substantial metaphyseal remodeling and sclerosis

*radiolucent metaphyseal line may no longer be visible

Craniomandibular osteopathy

bony proliferation of the maxilla and mandible

What breeds is craniomandibular osteopathy common in? What age?

terriers, labs, and dobermans 3-10 months old

Clinical signs of craniomandibular osteopathy

pain and difficulty opening the mouth

Radiographic findings of craniomandibular osteopathy

periosteal proliferation along one or both hemimandibles

can progress and surround the tympanic bullae

Avascular necrosis of the femoral head

aka Legg-Calvé-Perthes disease; occurs when the blood supply to the femoral head and neck is disrupted

What breeds is Legg-Calvé-Perthes disease common in? What age?

small breed dogs, 4-12 months old

Radiographic findings of Legg-Calvé-Perthes disease

mottled lucency of the femoral head and neck, often mixed with areas of sclerosis

misshapen femoral head and heck; thinning of the neck

acetabular joint space widening

How can hip dysplasia and Legg-Calvé-Perthes disease be differentiated?

Hip dysplasia can produce severe remodeling and malformation, but it does not typically cause actual loss/resorption of the femoral head and neck. Avascular necrosis does.

Femoral neck metaphyseal osteopathy

abnormal bone remodeling/growth around the femoral neck, causing the neck to become thickened

What species and age is femoral neck metaphyseal osteopathy common in?

young male cats

Radiographic appearance of femoral neck metaphyseal osteopathy

mottled lucency and progressive thinning of the femoral neck

characteristic "apple core" appearance!

Laminitis

can result from inflammation, endocrine disease, or mechanical overload and causes separation of the laminae of the hoof

Radiographic findings of laminitis

sinking and rotation of P3

remodeling at the distant tip of P3

Periosteal proliferation along the dorsal surface of P3

Gas within the hoof wall

Three measurements made to assess severity of laminitis:

1.) Founder distance

2.) Hoof wall thickness

3.) Hoof wall to P3 length ratio

Founder distance

line is made at the level of the coronary band, and a vertical line is drawn down to the extensor process of P3

Normal founder distance length

4-15 mm

An increased founder distance indicates what?

that P3 has sunk distally within the hoof capsule

Hoof wall thickness

measured at both a proximal and distal location, perpendicular from the hoof wall to the surface of P3

Normal hoof wall thickness

14-22 mm

What would be an abnormal hoof wall thickness? What would this indicate?

if the distal line is longer than the proximal line, this indicates that P3 has rotated away from the dorsal hoof wall

Hoof wall to P3 length ratio

calculation: hoof-wall thickness divided by the length of P3

Why is a hoof wall to P3 length ratio calculated?

to correct for differences in horse size and radiographic magnification

Normal hoof wall to P3 length ratio

30%

An increased hoof wall to P3 length ratio indicates what?

abnormal separation between P3 and the hoof wall

Chronic laminitis radiographic appearance

progressively greater remodeling of the distal phalanx

Aggressive vs non-aggressive bone lesions

Aggressive bone lesions progress rapidly, have poorly defined margins, and cause greater bone destruction

Non-aggressive bone lesions are slow-growing and well-defined

Aggressive bone lesions are often due to...

malignancy or infection

Five major features to focus on to determine if a bone lesion is aggressive or non aggressive:

1.) location

2.) pattern of bone destruction

3.) zone of transition

4.) new bone formation

5.) rate of change

Lesion location

The distribution of a lesion, if it is one or several bones, and what part of the bone is involved

Three types of distribution of a lesion

solitary, multifocal, or generalized

Examples of a solitary bone lesion

primary bone tumor or localized infection

Examples of multifocal bone lesions

metastasis or disseminated infection

Examples of generalized bone lesions

suggestive of metabolic, nutritional, or congenital disease

If multiple adjacent bones across a joint are affected, think about ________ disease

If distant bones are involved, think about ________ disease processes

joint

disseminated

Examples of describing what part of the bone is involved

-epiphysis --> articular surface of bone

-physis --> growth plate between epiphysis and metaphysis (if present)

-metaphysis --> connect the epiphysis to the diaphysis

-diaphysis --> long shaft of bone

-periosteum --> outer membrane that covers the bone

-cortex --> hard outer portion of a bone

-medullary cavity --> hollow space inside bone

Three patterns of bone destruction

1.) geographic

2.) moth eaten lysis

3.) permeative

geographic lysis

relatively large area of bone loss with sharply defined margins

moth eaten lysis

multiple small, irregular, poorly defined areas of bone loss

permeative lysis

contains numerous tiny, poorly defined lucencies, giving the bone a "sponge-like" appearance

Which patterns of bone destruction are aggressive?

Which patterns of bone destruction are non aggressive?

very aggressive: permeative

aggressive: moth eaten lysis

non aggressive: geographic lysis

*in order of bone margins becoming less defined; less defined = more aggressive

zone of transition

how quickly the radiograph changes from abnormal bone to normal bone.

Short zone of transition

you can easily identify where the lesion stops and normal bone begins; suggests a slower growing process

Long zone of transition

the lesion gradually fades into normal bone, making it difficult to determine exactly where the lesion ends

A ________ zone of transition is associated with a non aggressive bone lesion

A ________ zone of transition is associated with a aggressive bone lesion

short

long

Three types of new bone formation:

1.) smooth, lamellar

2.) palisading

3.) medullary

smooth, lamellar bone formation

forms organized layers of new bone along the cortex; usually indicates a slower process

palisading bone formation

consists of new bone extending perpendicular to the long axis of the bone

medullary bone formation

new bone formation within the medullary cavity

ex: panosteitis!

The different types of bone formation can all be either...

aggressive or non aggresive!

A _______ rate of change indicates non aggressive bone lesions

A _______ rate of change indicates aggressive bone lesions

slow

fast

Characteristics of a aggressive lesion

poorly defined, has moth-eaten or permeative lysis, has a long zone of transition, may have irregular periosteal proliferation, and changes rapidly over time

Three categories of aggressive lesions:

1.) neoplastic

2.) infectious

3.) immune mediated

Malignant neoplastic bone lesions

cancerous growths of bone

Malignant neoplasia can be divided into three categories:

1.) primary

2.) metastatic

3.) multicentric

primary malignant neoplasia

tumor that originates within the affected bone

examples of primary malignant neoplasia

-osteosarcoma

-chondrosarcoma

-fibrosarcoma

-hemangiosarcoma

Characteristics of primary malignant neoplasia

geographic, moth-eaten, and permeative bone lysis

cortical destruction

associated tissue mass

metastatic malignant neoplasia

neoplastic bone tumors in multiple bones

metastatic bone tumors typically arise from...

carcinomas (esp urogenital carcinomas)

metastatic bone tumors appearance

multiple areas of medullary sclerosis (though lesions can have variable appearances)

multicentric malignant neoplasia

originates at multiple locations rather than simply spreading from one primary bone tumor

multicentric bone tumors appearance

numerous relatively well-defined areas of bone lysis throughout the skeleton; "punched out" lesions