Orthopedic RadiographyThe Hard Facts

Dr. LeeAnn Pack

Diplomate ACVR

Musculoskeletal Radiography

Permit localization and characterization of a lesion

Size, shape, margination, number, position, opacity

Normal radiographic anatomy Diseases are often bilateral in the

appendicular skeleton Radiographic terms – use appropriately

Approach to Interpretation Soft tissues

– Intra-capsular or extra-capsular

Bones– Evaluate periosteal margins for new bone– Evaluate all cortices and subchondral bone– Evaluate the medullary cavity for changes in

opacity

Joints– Evaluate joint capsule attachments– Evaluate joint spaces and peri-articular margins

Bone Loss

Generalized bone loss– Metabolic or Nutritional disease, disuse

Called osteopenia Radiographic findings:

– Decreased bone opacity, cortical thinning, coarse trabeculation, bone deformity or pathological fractures may occur

– Loss of lamina dura – 2ary HPTism

Generalized Bone Loss

Bone Loss

Localized bone loss– Trauma, infection, tumor

Easier to detect than generalized

Bone Loss

Determining Aggressiveness– Zone of transition– The less distinct the

margin the more aggressive the lesion

Bone Loss

If the cortex is destroyed, the process is more aggressive than if the cortex is allowed to remodel

Intact Destroyed

Focal Bone Loss

Geographic Lysis– Large area of lysis– Usually less

aggressive– If destroys the cortex

aggressive

Focal Bone Loss

Geographic lysis– Expansile

appearance– Expansion of the

cortex around an enlarging mass less aggressive

– Note the intact cortex in the picture

Bone Cyst

Focal Bone Loss

Moth Eaten lysis– Multiple smaller

areas of lysis– Areas may become

confluent– More aggressive

than geographic lysis

Focal Bone Loss

Permeative Lysis– Numerous small and

pin point areas of lysis whose margins are indistinct and fade gradually into normal bone

Permeative Lysis

Spiculated Periosteal Reaction

Amorphous Periosteal Reaction

Differentials

Based on aggressiveness of lesion Location/s Mono/ poly-ostotic / joint centered Must assess signalment and history,

location, additional tests… Many diseases have similar

radiographic appearance – may require biopsy

Primary Bone Tumors

Radiographic Signs:– Lesion may be primarily productive, lytic or

both– Lytic or productive lesions usually have an

aggressive appearance– Away from the elbow and toward the knee

Primary Bone Tumors

Radiographic Signs:– Typically mono-ostotic– Typically located in the

metaphysis– Lesions typically do not

cross joints

Primary Bone Tumor

Primary Bone Tumor

OSA – note the ST enlargement

Fungal Osteomyelitis

Radiographic Signs:– Typically lesions are seen in the

metaphysis– Appear similar to primary bone tumor– Often extensive destruction when a joint is

infected (septic arthritis)– Often is poly-ostotic

Fungal Osteomyelitis Etiological Agents: Blastomyces dermatitidis

– Southern states, mid-west and south-west

Coccidioides immitis– Western states

Histoplasma capsulatum– mid-western states

Cryptococcus neoformans & Aspergillosis– Throughout the US

Fungal Osteomyelitis

Fungal

Fungal Septic Arthritis

Differential Diagnosis Single aggressive lesion of long bones

– Primary bone tumor– Fungal osteomyelitis– Metastatic bone tumors

Carcinomas

Use signalment, geographic location, and clinical findings to prioritize the differential list– May require a biopsy with culture

Synovial Cell Sarcoma

Early in the disease there is intra-capsular and/or peri articular swelling

Swelling then turns to a mass effect Later there is bone lysis of multiple

bones of the joint

Synovial Cell Sarcoma

Synovial Cell Sarcoma

Hypertrophic Osteopathy

Palisading periosteal response– Usually solid

Occurs secondary to a mass somewhere– Thoracic– GU tract– Fungal disease– Heartworm disease

HO

Begins on the abaxial digit and progresses proximal and axially

HO

HO

Radiographs of the chest and abdomen should be made

And abdominal US can be preformed if needed

Cruciate Ligament Rupture

Cranial displacement of the infra-patellar fat pad

Caudal displacement of the fascial stripe

Cruciate Ligament Rupture

DJD– Base and apex of the

patella– Proximal aspect of

the trochlear ridge– Medial and lateral

aspects of the distal femur and proximal tibia

– Fabellae

DJD Stifle Peri-articular osteophytes

DJD – Joint Mice

Joint mice are pieces of articular cartilage that have become detached and are in the joint – they mineralize when they have a blood supply – must R/O avulsion fragment

Intra-capsular ST Swelling

Normal IC Swelling

Cruciate Rupture

Patellar Luxation

Patellar Luxation

Patellar Luxation

Developmental MS Diseases

OCD– Shoulder– Elbow– Stifle– tarsus

Fragmented Medial Coronoid Process

Ununited Anconeal Process

Panosteitis Hypertrophic

Osteodystrophy Hip Dysplasia Legg-Calve-Perthes

Osteochondrosis

Dysfunction of endochondral ossification (bone that forms from cartilage)

Disturbance leads to increased thickness of the cartilage

Cartilage is radiolucent compared to bone therefore, radiographically we see a radiolucent subchondral defect

Osteochondrosis

Subchondral defect – flattening Surrounding sclerosis as time

progresses Joint mice Secondary DJD Locations: shoulder, elbow, stifle, tarsus

Shoulder OCD

Subchondral defect on the caudal aspect of the humeral head

May see a joint mouse May just be flattened Secondary DJD May need arthrogram or explore

Shoulder OCD

Shoulder OCD – note flattening

Elbow OCD Subchondral defect present on the

distal medial aspect of the humerus (humeral condyle)

Surrounding sclerosis

Elbow OCD – CC and Obl

Tarsus OCD

Rotts! Medial trochlear ridge of the talus Often seen small mouse Joint effusion DJD See best on oblique view or flexed

lateral

Tarsal OCD MTR

Fragmented Medial Coronoid Process

On the lateral view– Blunted appearance

to the medial coronoid process

FCP

On the CC view– New bone production

on the medial coronoid process

– Look like has been hit with hammer

FCP A = blunted medial coronoid process B = osteophyte on anconeal process C = osteophyte on medial coronoid process

Ununited Anconeal Process

Forms from a separate center of ossification Should fuse in all dogs by 6 months Lucent line – best seen on flexed lateral

Ununited Anconeal Process

Ununited Anconeal Process6 month old GSD

7 month old GSD

UAP

Elbow Dysplasia

1. Ununited anconeal process

2. Osteochondrosis of medial aspect of distal humeral condyle

3. Fragmented medial coronoid process

4. Premature closure of radius/ulna physis causing incongruency of elbow joint

Elbow DJD

Note the large osteophyte on the anconeal process – this is often times one of the earliest changes seen with DJD in the elbow

Panosteitis

Late– Medullary opacities

become patchy– Opacities appear to

coalesce– Solid periosteal reaction

may be seen on adjacent cortex

Panosteitis Multiple leg involvement is likely Shifting leg lameness

Panosteitis

Hypertrophic Osteodystrophy

Early– A thin band of

radiolucency in the metaphyseal portion of the bone

– Double physis– Cheeseburger sign– Sclerosis seen

adjacent to lucency

HOD

HOD

HOD

Hip Dysplasia

Clinical Features– The laxity of the coxofemoral joint leads to

improper development and degenerative change

– Clinical signs range from mild to severe– Usually bilateral but can be unilateral

Extended VD View

Used for OFA Legs pulled down

and rotated inward Must include the

entire pelvis and stifles

Positioning Effect of Rotation

Normal Anatomy - Coverage

There should be at least 50% coverage of the femoral head by the dorsal acetabular rim

HD with Severe Subluxation

Normal Anatomy

The femoral neck should be more narrow than the femoral head

The femoral neck should have a smooth margin

Hip Dysplasia

The acetabulum is shallow and flattened.

Bilateral Hip Dysplasia

Hip Dysplasia

Periarticular osteophytes will form along the acetabular rim and dorsal edge

Hip Dysplasia

Wedging of the cranial articular margin

Morgan Line

Enthesiophyte formation on the distal aspect of the femoral neck

Secondary to coxofemoral joint laxity

Early sign of DJD

Does This Dog Have Hip Dysplasia?

Legg-Calve-Perthes

Associated with decreased or lack of blood supply to the femoral capital epiphysis

The normal blood supply comes from:– Synovial membrane– Arteries in the round ligament of the head

of the femur– Nutrient vessels through the metaphysis

Legg-Calve-Perthes

Patchy areas of lysis in the femoral head Invasion of vascular granulation tissue

replacing dead bone

Legg-Calve-Perthes

Deformity of the femoral head Flattening of the femoral head

Legg-Calve Perthes

Shoulder – What Do You See?