Small Animal Orthopedic Radiology Lecture 2 – Developmental Bone Disease VCA 341 Fall 2011 Andrea...

Small Animal Orthopedic Radiology

Lecture 2 – Developmental Bone Disease

VCA 341 Fall 2011

Andrea Matthews, DVM, Dip ACVR Assistant Professor of Radiology

Osteochondrosis

Failure of endochondral ossification Leads to increased thickness of articular cartilage Appears as subchondral defect

Osteochondrosis = OC

Osteochondritis dissecans = OCD When a flap is formed and separates from subchondral

bone Only seen radiographically when……

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mineralized or… with arthrography

Osteochondrosis

Occurrence Young, rapidly growing, large to giant breed dogs Usually develop signs between 6-9 months of age Occurs in specific anatomic locations

• Caudal aspect of humeral head

• Medial aspect of the humeral condyle

• Lateral femoral condyle

• Trochlear ridges of the talus (medial most commonly)

Can occur in other locations Frequently bilateral

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Shoulder Osteochondrosis

Roentgen signs Subchondral defect and scelosis of the caudal or

caudolateral aspect of the humeral head

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Shoulder Osteochondrosis

Roentgen signs Secondary osteoarthrosis Osteophytes may form in the intertubecular groove Calcified flap of articular cartilage OCD

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Elbow Osteochondrosis

Roentgen signs Subchondral defect and sclerosis of the medial aspect

of the humeral condyle, best seen on DLPMO view Secondary osteoarthrosis

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Stifle Osteochondrosis

Roentgen signs Subchondral defect and sclerosis of the distal aspect of

the lateral femoral condyle May also affect medial condyle but less common Joint effusion and osteoarthrosis

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Normal anatomy The extensor fossa of the long digital extensor muscle

can be confused with an OC lesion

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OC lesion Extensor fossa

Tarsal Osteochondrosis

Roentgen signs Flattening of the medial trochlear ridge of the talus Widening of the joint space Associated with intracapsular ST swelling and DJD

11Normal OC

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Roentgen signs On the lateral view, the plantar aspect of

the tibiotarsal joint will appear wide A mineral fragment may be seen OCD

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Elbow Dysplasia

Fragmented medial coronoid process (FCP)

Ununited anconeal process (UAP)

Osteochondrosis of the medial humeral condyle (OC)

Asynchronous growth of the radius and ulna (?)

Proximal ulnar dysplasia (?)

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Fragmented Medial Coronoid Process

Occurrence Most common developmental abnormality of the elbow Medium and large breed dogs

• Retrievers, GSD, Bernese Mountain Dog Clinical signs develop usually at 5-12 months of age Higher incidence in males

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Roentgen signs Earliest signs are sclerosis of the trochlear notch of the

ulna and osteophytes on the anconeal process and radial head

Osteophytes on the medial coronoid seen on the craniocaudal view

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Roentgen signs Medial coronoid appears blunted on the lateral views May see fragment; however, no fragment is visualized

in the majority of cases

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Ununited Anconeal Process

Occurrence Anconeal process forms from separate center of

ossification Normally fuses to proximal ulna at 5 months of age Failure to fuse (likely due to joint incongruity) UAP GSD predisposed; also seen in other large breeds and

Bassett hounds

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Roentgen signs Irregular, lucent line crossing the anconeal process with

adjacent sclerosis Best seen on flexed lateral view Secondary osteoarthrosis

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Panosteitis

Occurrence 5-18 months of age; reports in mature animals (out to 7

years) Large to giant breed dogs

• GSD, Dobermans, Retrievers, Bassett hounds Self limiting disease with unknown etiology Shifting leg lameness with pain on palpation of long

bones Histologically no evidence of inflammation

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Panosteitis

Roentgen signs

Early Increased medullary opacity Usually in diaphysis near nutrient foramen Blurring of trabecular pattern

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Panosteitis

Roentgen signs

Late Medullary opacities become better

delineated patchy appearance of medullary cavity

Adjacent opacities may coalesce Rough endosteal surface Solid periosteal reaction may be noted

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Panosteitis

Hypertrophic Osteodystrophy (HOD)

Occurrence 2-7 months of age Large to giant breeds of dog Unknown etiology Usually systemically ill

• Usually reluctant to move, painful walking

• Swollen, painful distal radius/ulna and distal tibia

• Pyrexia

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Roentgen signs Lesions usually bilaterally symmetric

and involve the metaphysis of long bones, especially the distal radius, ulna and tibia

Early Thin, radiolucent band in the

metaphysis just proximal to the physis “double physis sign”

Sclerosis adjacent to the radiolucent line in the metaphysis

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Roentgen signs

Late Formation of a cuff or sleeve of

periosteal new bone adjacent to the metaphysis, which is separated from cortex by thin, lucent zone

Represents subperiosteal hemorrhage

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Roentgen signs

Late Periosteal reaction becomes more

solid and confluent with the cortex later on

Results in marked bony enlargement of the metaphysis

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Images show progression of disease…

Early Late

Retained Cartilaginous Core

Occurrence Unknown etiology Form of OC of the distal ulnar

metaphysis/physis• Failure of endochondral ossification

resulting in formation of core of cartilage in the metaphysis

Large to giant breeds• Saint Bernard

Usually develop clinical signs around 6-12 months of age

Often bilateral

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Roentgen signs Conical, radiolucent zone extending from the distal ulnar physis

proximally into the distal ulnar metaphysis Smoothly marginated or irregular

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Roentgen signs Can cause asynchronous growth of

the radius and ulna and angular limb deformity

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Hip Dysplasia

Normal hip joint At least ½ of the femoral head

should be covered by the dorsal acetabular rim

The femoral neck should be narrower than the head and have a smooth margin

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Hip Dysplasia

Roentgen signs Shallow, flattened acetabulum Inadequate femoral head coverage or even subluxation

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Normal

Hip Dysplasia

Roentgen signs Periarticular osteophytes form along the acetabular rim,

resulting in an irregular edge

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Hip Dysplasia

Roentgen signs Morgan line

• Osteophyte formation along caudal femoral neck usually secondary to joint laxity

• These osteophytes are actually enthesiophytes at the attachment of the joint capsule

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Hip Dysplasia

Standard VD view of Pelvis Pull legs straight back and rotate

inward Open collimation to include entire

pelvis and both femora through to the stifles

Called “straight or extended leg view” Used for OFA evaluation

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Hip Dysplasia

Orthopedic Foundation for Animals (OFA) Uses extended leg view 24 months of age or older Evaluate for subluxation, degenerative changes Hips graded based on following categories

• Excellent• Good• Fair• Borderline• Mild dysplasia• Moderate dysplasia• Severe dysplasia

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Hip Dysplasia

PennHIP The University of Pennsylvania Hip Improvement Program Allows evaluation of joint laxity prior to degenerative

changes Examiners have to be certified Three sets of radiographs

• Extended leg

• Distraction view with distraction apparatus

• Compression view with distraction apparatus Calculation of distraction index (DI)

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Hip Dysplasia

Distraction index (DI) 0 = tightest hip 1 = completely luxated hip 0.4 = cut off index which identifies

dogs that have the highest probability of developing osteoarthrosis secondary to hip dysplasia

Index corrected for breed

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Hip Dysplasia

Extended leg

CompressionDistraction

Hip Dysplasia

Other methods Half-axial view

• Distraction method

• Distance between the femoral heads compared on extended leg view and distraction view

Norberg angle

• Used in Europe

• Normal angle is >105 degress

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Aseptic Necrosis of the Femoral Head (Legg-Calve-Perthes)

Occurrence and Pathogenesis Young (8-18 months of age) toy and small breed dogs

• Poodles, miniature pinscher, terriers Bilateral <15% of the time Compromised blood supply to proximal femoral

epiphysis necrosis of subchondral bone Normal blood supply to femoral head in adult dogs

• Synovial membrane (sole supply in puppies)

• Arteries in round ligament of the head of the femur

• Nutrient vessels through metaphysis (after physeal closure)

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Roentgen signs Increased width of joint space

• Articular cartilage thickens as ischemia causes necrosis of subchondral bone

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Roentgen signs Irregular opacities in the

femoral head

• Fragmentation of trabeculae Patchy regions of osteolysis in

femoral head

• Invasion of vascular granulation tissue absorbing and replacing dead bone

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Roentgen signs Deformity and flattening of the femoral head

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Roentgen signs Remodeling of the acetabulum = osteoarthrosis Due to abnormal articulation and osteophyte formation

on the acetabulum, femoral head and neck

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Patellar Luxation (PL)

Occurrence Young, small breed dogs; also

seen in large breeds• Medial luxation in small

breeds• Lateral in large breeds

Most commonly congenital/developmental• Can be traumatic

Associated with malalignment of the quadriceps due to rotation and/or deformity of the femur and/or tibia

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http://devinefarm.net/rp/grp/mpl2.gif

Medial Patellar Luxation (MPL)

Roentgen signs Patella medial to trochlear groove Coxa vara

• Lateral bowing of distal femur

• Medial bowing of the proximal tibia

• Medially located tibial tuberosity and quadriceps

Shallow trochlear groove

• Requires skyline view to evaluate Secondary osteoarthrosis usually mild

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http://devinefarm.net/rp/grp/mpl2.gif

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Medial Patellar Luxation (MPL)

Arrow is pointing to cranial margin of the patella

End

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Small Animal Orthopedic Radiology Lecture 2 – Developmental Bone Disease VCA 341 Fall 2011 Andrea...

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