20. Bone tumours and infections

Question 1

Which portion of the bone is typically affected by primary bone tumours?

Answer 1

Metaphysis

=> may extend out

Question 2

What is the most common primary bone tumour of dogs?

Answer 2

OSA

Question 3

What is the typical age distribution of canine OSA?

Answer 3

BIMODAL!!

=> approx. 2yrs, and later in life

Question 4

What are the typical sites of forelimb and hindlimb OSA?

Answer 4

Towards knee, away from elbow

Question 5

What is codmans triangle?

Answer 5

Reactive subperiosteal new bone -> was considered pathognomic for neoplasia, however NOT TRUE. Can be seen with benign lesions. NOT SPECIFIC!

Question 6

TABLE OF NEOPLASTIC / INFECTIOUS BONE DISEASE

Answer 6

Question 7

What is the most common feline primary bone tumour? Age of incidence?

Answer 7

OSA, mean 10yrs

Question 8

How does feline OSA differ from canine OSA?

Answer 8

• Less common (but still most common primary bone)
• Hindlimbs more commonly affected than forelimbs
• Age: 10yrs
• Less pulmonary mets

Question 9

What are reported causes of secondary OSA? What breeds are typically effected, and how do they differ in appearance?

Answer 9

• BONE INFARCTION

=> THR, idiopathic, very rarely fracture / internal fixation / TPLO

=> SMALL BREEDS -> shelties and terriers

• Bone infarcts: mutifocal medullary opacities
• > OSA tends to be more lytic cf predominantly mixed appearance of primary canine OSA

Question 10

How may idiopathic and implant associated bone infarction differ in appearance?

Answer 10

Idiopathic:

• Typically polyostotic

Implant

• Monostotic
• Wispier appearance

Question 11

What is the lag time reported with TPLO associated OSA?

Answer 11

• 4.5 yrs

Question 12

What is the typical signalment of dogs with fungal osteomyelitis?

Answer 12

Young, large breed dogs from geographic areas

=> Blasto (South east)

=>Coccidio (South West)

Question 13

What region of the appendicular skeleton is typically effected by fungal osteomyelitis?

Answer 13

Metaphysis (high blood supply -> haematogenous spread)

OFTEN POLYOSTOTIC!

* can occur in diaphysis / epiphysis, or be monostotic

Question 14

What is the most common cause of bacterial osteomyelitis?

Answer 14

Direct innoculation

Question 15

How does BACTERIAL osteomyelitis differ from primary bone neoplasia radiographically?

Answer 15

• As usually not haematogenous -> focal, and variable location. MAY NOT BE METAPHYSIS
• Haematogenous more typical IN YOUNG DOGS and POLYOSTOTIC therefore
• Tend to have less aggressive periosteal reaction (palisading / columnar rather than spiculated)

Question 16

List protozoan agent associated with osteomyelitis? And features?

Answer 16

HEPATOZOON -> spread by tick Rhicephalus sanguineus

• Rx:

Mainly periosteal lesions -> Variable appearance, can be smooth!

Axial or appendicular

May be extensive skeletal involvement

* Typically have systemic signs*

Question 17

List common features of metastatic bone neoplasia

Answer 17

• Axial and proximal long bones
• Carcinomas > sarcomas. But many tumours
• Pulmonary / mammary classic
• Diaphyseal, metaphyseal

Question 18

What is the most common canine subungual tumour? Which dogs?

Answer 18

SCC

=> Large black coated dogs

Question 19

What features have been proved to be similar between subungual tumours and infections?

Answer 19

• manus / pes distribution
• Freq of bone involvement 52% vs 63.5% (neoplasia)

Question 20

Lysis of a digit was most common in which tumour?

Answer 20

SCC

Question 21

WHAT IS FELINE LUNG DIGIT SYNDROME?

Answer 21

PUlmonary tumour -> DIGITAL METS!!!! Often associated with p

NOTE:

DIffers from HYPERTROPHIC OSTEOPATHY (Maries disease), where palisading or brush border periosteal reaction seen along diaphysis of long bones

• > thoracic or abdominal neoplastic or inflamm lesion elsewhere
• > DOESNT HAVE TO BE NEOPLASTIC