Orthopedic Radiography
The 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 intracapsular 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

 Radiographs of the chest and abdomen should be made
 And abdominal US can be preformed if needed
HO

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

 On the CC view
– New bone production on the medial coronoid process
– Look like has been hit with hammer
FCP

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 Process
6 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?