VSAC450 - Orthopedics

What is osteomyelitis? What are its etiologies?

inflammation of bone and bone marrow

caused by bacteria or fungi

How did bacteria enter the bone? (4)

1. traumatic contamination from outside --> in

2. traumatic contamination from inside --> out

3. during surgery

4. extension of soft tissue infection

Can osteomyelitis have a hematogenous origin? Where would the bacteria be deposited in such situation?

yes

deposit at ends of bones due slower blood flow at loops

What are common sources of bacteria in the blood stream (4)?

1. nasty teeth

2. cystitis

3. pyoderma

4. umbilical infection

Who commonly gets osteomyelitis? At which part of the bone?

young animals

metaphysis

What are the most common bacteria in canine bone infections (2)? Anaerobe or aerobic bacteria?

Staphylococcus

Streptococcus

Anaerobe

In what situations would result in one and Multiple bacterial infection?

one: hematogeouns

many: trauma/soft tissue extension

What factors favour the conversion of contamination to persistent infection? (4)

Immunosuppression

Fracture instability

Shit blood supply to the bone

Presence of foreign bodies or dead bones

How do biofilm affect osteomyelitis infection?

bacteria clings to hardware --> biofilm protects bacteria from phagocytosis/antibodies/antibiotics + more numerous

How can bacteria develop a biofilm?

Sequestrum: dead, avascular, piece of bone

foreign object

What are common fungi that cause osteomyelitis? (4)

blastomycosis, coccidioidomycosis, histoplasmosis, cryptococcocosis

How do fungi infect the bone? What other organs are typically infected?

hematogenous route

lungs and eyes, enlarged LN

What part of the bone is affected by fungal osteomyelitis? Can they infect ajacent joints?

metaphyses + epiphyses

yes

What are the clinical signs of osteomyelitis? What are the acute vs chronic differences?

lameness, systemic illness + fever ( fungi ONLY)

acute: swelling, redness discharge

chronic: draining tracts

What are draining tracts characteristics associated with osteomyelitis (4)?

small wounds that come and go

can have multiple

often distal to inf

can be associated with sequestrum

What are the radiographic findings for an osteomyelitis infection?

ragged, proliferative bone with areas of lysis

How would you describe this lesion?

lysis and bone proliferation of the distal metaphysis-diaphysis of the humorous

What are the clinical pathological findings of osteomyelitis?

elevated C-reative protein

biopsy

culture (not draining track)

histopathology

How is acute BACTERIAL osteomyelitis treated?

hematogenous: sys antibiotics for 3w minimum

What conditions are necessary to heal from a chronic BACTERIAL osteomyelitis?

can heal with adequate blood supply + stable

How can chronic BACTERIAL osteomyelitis be treated? (5)

remove sequestra

stabilize fracture

remove or replace inf hardware

regional perfusion with antibiotcs

4-6w on systemic antibiotics

How is fungal osteomyelitis treated?

systemic long-teerm antifungal therapy

amputation or debridement

relapses common

What is the common signalment of panosteitis (eosinophilic panosteitis)?

unknown cause, during first 2 years in large breed dogs (young german shepard)

What is the pathogenesis of panosteitis?

high pressure in medullary canal --> excessive bone remodeling --> necrosis of fat of medullary canal --> replaced with fibrous tissue --> woven bone forms + pain

What are the clinical signs of panosteitis? (5)

varying degrees of lameness + shifting

lethargic

febrile

usually eosinophilic

painful when palpate at diaphyses

What lesions are seen on radiograph for a dog with panosteitis?

early: normal

patchy, mottled, sclerotic densities in medullary canal

late: periosteal proliferation

How is panosteitis diagnosed?

rule out other possible cause of lameness

How is panosteitis treated?

self-limiting

can give analgesics

What is the common signalment for a dog with Hypertrophic osteodystrophy (HOD)?

2-6m large breed dog

What are the common clinical signs for Hypertrophic osteodystrophy (HOD)? How long do symptoms last?

symmetrical lameness/swelling at fore/hindlimbs

fever

anorexia

lethargy

7-10 days

What is the pathogenesis for HOD?

immune cells attack metaphysis adjacent to physis --> necrosis, hemorrhage, inflammation, resorbed bone --> physis remodels + widens --> subperiosteal hemorrhage --> periosteal proliferation/flaring of metaphyses

What are the radiographic findings for HOD?

enlargement of metaphyses at radius, ulna and tibia

"double" physis

periosteal proliferation can be there

What is the most common etiology for HOD?

immune-mediated disease

bac inf

How is HOD treated? (6)

usually self-limiting

possible limb-deformities

supportive care

analgesics

antibiotic therapy

corticosteroids

What is the signalment of craniomandibular osteopathy?

3-8m west highland white and scottish terriers

How is craniomandibular osteopathy characterized?

proliferation of woven bone in mandibles

painful + difficult to open mouth

What are common radiographic findings for craniomandibular osteopathy?

proliferation of woven bone of mandible and skull

usually bilaterally symmetrical

How is craniomandibular osteopathy diagnosed?

radiograph, CT, biopsy to rule out other diseases

How is craniomandibular osteopathy treated?

supportive care, analgesics, wait it out until proliferation recedes

What are characteristics for Hypertrophic Osteopathy (HO)?

symmetrical periosteal proliferation over bones in distal extremeties

associated with thoracic or abdo masses

What are common physical findings for Hypertrophic Osteopathy (HO)?

ok joints

stiff gait in all limbs thicker + painful metacarpi, metatarsi, antebrachium and crus

What is the pathophysiology for Hypertrophic Osteopathy (HO)?

mass stimulate autonomic nerves --> vasodilation + increased subperiosteal blood supply --> new bone formation + lifting of periosteum = pain

tumor makes growth factors to continue new vessel and new bone formation

What kind of masses cause HO?

neoplastic (90%), abcess, spirocerca lupi inf

How is HO treated?

analgesics

vagotomy

lesions recede if primary mass is removed

What causes osteopenic and fragility disorders?

Ca/P imbalance due to hyperparathyroidism

How can primary hyperparathyroidism cause osteopenia (2)?

parathyroid tumour

parathyroid hyperplasia

How can secondary hyperparathyroidism cause osteopenia (2)?

nutritional (low Ca:P ratio)

renal failure

What is the pathogenesis for nutritional secondary hyperparathyroidism?

diet is low in Ca or improper Ca:P ratio --> extra PTH seecreted --> move Ca out of bones into blood --> osteopenic bones --> folding fractures

What are other nutritional problems affecting bones?

Vit A or D deficiency or oversupplementation --> skeletal problems

restricted protein diets in growing animals

What are differential diagnoses for folding fractures (osteopenia)?

vit-D dependent rickets type 2

osteogenesis imperfecta

How is nutritional secondary hyperparathyroidism treated?

correct diet + no internal fixation

What are the characteristics for Diffuse Idiopathic Hyperostosis (DISH)?

flowing bone bridging the vertebral column over 3 continuous disks

stiffness

What are the kinds of Primary Bone Tumours? (5)

osteosarcoma (90%)

chondrosarcoma

fibrosarcoma

hemangiosarcoma

multilobular osteochondrosarcoma (MLO)

What is the common signalment for osteosarcoma (+ chondrosarcoma)?

middle aged (5-9y) giant breed dog

very agressive form seen in 2y olds

What is the common site for osteosarcoma (+ chondrosarcoma)?

metaphyses/epiphyses

doesn't cross joints

distal radius, proximal humerus, both ends of tibia/femur

What are the common radiographic findings for osteosarcoma?

mix of lysis = new bone formation

can get pathologic fractures

What is the early radiographic finding for osteosarcoma?

irregular trabecular pattern or lysis

Where do fracture-associated sarcomas form? Why?

site of previous fracture

complication (inf or delayed union) or metal corrosion

What are the most common tissue types that cause secondary tumours in bones? (7)

prostatic

mammary

transitional cell carcinoma

sarcoma

multiple myeloma

lymphoma

Where are common bone lesions found in bones with secondary tumours?

can be anywhere

most common = diaphysis

How are bone neoplasias diagnosed?

x ray (include chest if primary)

definitive: cytology or bone biopsy + histo

What is the biological behaviour of osteosarcoma (OSA)?

OSA has already metastasized (LUNGS) by the time it gets diagnosed

What are the risk factors for developing OSA? (3)

genetics: abnormal p53 gene

previous fracture/infection

spayed or neutered during first year of life

What is the prognosis in dogs with OSA?

no tx or remove primary tumour: 5m

chemo: 10-11m

How is cat OSA different from dog OSA?

cat = slower to metastasize therefore good candidate for amputation when diagnosed (curative)

How is OSA treated?

amputation

limb-sparing procedure

chemo (cisplatin or doxorubicin)

immunotherapy

How is OSA treated PALLIATIVELY?

remove primary tumour

palliative radiation

pain management

biphosphonate therapy

Describe the characteristics of each grade of Chondrosarcomas. (1 +3)

1. least aggressive + cured by removing primary tumour

3. like OSA except less chemoresponsive

What are the characteristics for Multilobular Osteochondrosarcoma?

axial skeleton (skull)

osteoproductive

50% chance LT survival with removal + chemo

What is the biological behaviour and prognosis for secondary bone tumours?

death + painful + specific to primary cell tumor type

How are secondary bone tumours treated? What about in bone?

address primary tumour + metastases

palliative ration, drugs, sx removal for bone

What are the characteristics of synovial sarcoma?

primary or secondary tumor

CROSSES JOINTS

3 grades (3 is worst)

How are synovial sarcomas treated?

amputation

What are the indications for amputation? (9)

1. severe nerve damage

2. severe blood supply damage

3. severe muscle or bone loss

4. necrotizing fasciitis

5. neoplasia

6. chronic, debilitating muscle contractures

7. atrophic non-unions

8. sever osteoarthritis in a limb

9. chronic osteomyelitis + nonresponsive to tx

What are NOT indications for amputation? (7)

1. puppy + kitten fracture

2. fractures you can fix

3. fractures of tibia, ulna, radius, metacarpals, metatarsals

4. degloving injuries

5. hip/shoulder injury

6. cruciate ligament ruptures

7. acute nerve injuries

Where is a forelimb amputation done?

forequarter disarticulation with the scapula

Where are hindlimb amputations done? (3)

1. hemopelvectomy (remove part of pelvis)

2. hindquarter disarticulation at the hip

3. proximal third femur amputation

How is an amputation performed for prosthetic use?

1. done through a joint

2. leave lots of soft tissue to be comfy

3. best = at or below carpus/tarsus

What are the components of an osseointegrated prosthese?

part of prosthesis is implated into bone + external foot

What are types of distal amputations with pad transfer? What is it's purpose?

types: carpal pad transposition + free footpad transfer

purpose: make limb functional when amputated at or distal to carpo(tarso)metacarpal(tarso) junction

What are the characteristics of digital amputations?

any/all digits can be removed

all 3 phalanges can be removed

How is osteochoncrosis defined?

disruption of endochondral ossification (cartilage to bone) when articular cartilage/epiphysis are developing

What causes osteochoncrosis?

microtrauma to vessels --> affects blood supply --> necrosis of subchondral bone

What are the histo characteristics of osteochoncrosis?

cartilage = tick + abnormal, defect in subchondral done

How are microtrauma to vessels occur in osteochondrosis? What are possible consequences?

everyday minor trauma --> microfissures

fissures spread to surface --> make flap

consequence: osteochondritis dissecans (OCD)

What are possible etiologies for osteochondrosis/OCD?

genetic

nutritional

traumatic

ischemis

What are characteristics of OCD?

large/giant breed dogs

onset at 4-12m

c/s: lameness and joint swelling

What are the most common sites for OCD?

caudal humeral head, medial humeral condyle, medial trochlear ridge of talus, lateral femoral condyle, distal ulnar metaphysis

How is OCD diagnosed?

PE (joint swelling), xray (lucent area in subchondral bone), CT = best

True or False: OCD is frequently bilateral.

TRUE

How is OCD treated? (7)

1. medical therapy (exercise, NSAIDs, chondroprotective agents)

2. arthrotomy/arthroscopy: remove flap + debride

3. osteochondral transplantation

4. implant resurfacing

5. chondrocyte implant

6. stem cells

7. arthrodesis (chronically affected/arthritic joints)

What is the definition of osteoarthritis (OA) or degenerative joint disease (DJD)?

slow degeneration of articular cartilage

How does OA/DJD occur?

articular cartiledge loses its normal matrix --> fibrillated chondrocytes --> fissured --> subchondral bone exposed

How does OA/DJD look radiographically?

thickened joint capsule

osteophytes at joint capsule attachment

What causes OA? (4)

1. articular fractures

2. joint incongruity

3. joint instability

septic and immune-mediated arthritis

4. toxic insults

How is OA treated in dogs?

result of another joint problem --> treat underlying cause

What are clinical signs of OA in a DOG? (4)

1. sometimes none

2. decreased joint range of motion

3. stiffness in morning

4. lameness after exercise

What are clinical signs of OA in a CAT? (5)

1. weight loss, A-

2. U+/feces outside litterbox

3. attitude change

4. poor grooming

5. reluctance to jump

What are strategies for treating OA? (7)

1. weight loss (decrease load on joint)

2. corrective osteotomy (shift load to normal part of joint)

3. molecular/gene therapy

4. modify cartilage metabolism (DMOAs) --> omega-3

5. decrease pain/inflammation --> NSAIDs, nerve growth factor inhibitors, corticosteroids, stem cells, platlet-rich plasma

6. rehab

7. remove (excision arthroplasty), replace, fuse joint (arthrodesis)

What are differences between pediatric vs adult patient? (4)

1. growth plates

2. thickker cartilage + periosteum

3. higher collagen compared to mineral

4. ligaments stronger than bone