Musculoskeletal - Bones

Question 1

2 types of abnormalities related to bones

Answer 1

abnormality of gait and abnormality of form
(often present clinically together)

Question 2

Wolff’s Law

Answer 2

the idea that natural healthy bones will adapt and change to adapt to the stress that it is subjected to

Question 3

Pathological fractures

Answer 3

associated with processes that weaken the bone - predisposing it to fracture
(fracture is caused by an underlying disease)

Question 4

process of fracture healing

Answer 4

1. Hematoma formation
2. Growth factors produced from macrophages and platelets stimulate granulation tissue formation (hours to days)
3. Mesenchymal cells differentiate into osteoblasts (days)
4. Early callus formation initially contains cartilage. The cartilage functions to anchor and create a more stable environment for the production of woven bone (days)
5. Primary callus of woven bone (weeks)
6. Remodelling of woven bone into lamellar bone into a secondary callus (weeks to months to years)

Question 5

list some factors that can delay the healing of fractures

Answer 5

excessive movement
reduced blood supply / poor nutrition
tissue necrosis
infection
pathological fracture e.g. neoplasia
metallic implants

Question 6

chondrodysplasia

Answer 6

widespread abnormality of growth cartilage
localised in some breeds - basset hound, dachshund
inherited and often lethal (bulldogs, spider lambs)

Question 7

osteopetrosis

Answer 7

a rare disorder where bones grow abnormally and are overly dense - bones contain a large thickened area but the trabeculae are fragile
SLC4A2 mutation in cattle
Angus cattle genetic mutation
BVDV
growth retardation lattice (thickening near physis)
lead toxicity

Question 8

3 types of osteopetrosis

Answer 8

1. inherited - bones have a large thickened area but the trabeculae are fragile
2. infectious disease - growth retardation lattice (region of thickening near physis)
3. toxic - lead

Question 9

disorders of bone formation

Answer 9

angular limb deformities
feline physeal dysplasia

Question 10

angular limb deformities

Answer 10

common in foals
associated with assymetric lesion involving growth plate causing failure of endochondral ossification, abnormal carpal and tarsal bone development, laxity of supporting structures

Question 11

most common angular limb deformity in dogs

Answer 11

premature closure of the distal ulnar physis. the radial growth plate remains open, resulting in continued growth and eventuating in a valgus angular limb deformity.

Question 12

feline physeal dysplasia

Answer 12

a condition of young cats, in which one or both femoral heads atraumatically separates from the femoral neck along an abnormal physis.
This lesion is often bilateral, and is more common in male neutered, overweight cats of 2-4 years of age.
-> Typically this lesion can result in a slipped capital femoral epiphysis or a fracture of the femoral neck.

Question 13

metabolic bone diseases

Answer 13

osteoporosis / osteopaenia
rickets and osteomalacia
fibrous osteodystrophy

Question 14

difference between osteoporosis and osteopaenia

Answer 14

osteopaenia is when there is a loss of bone mass, but the remaining bone is adequately mineralised (quality of bone is not reduced, just the quantity)

osteoporosis is a clinical syndrome of reduced bone mass manifested by bone pain and pathologic fractures - it is more serious than osteopaenia.

Question 15

what are growth arrest lines?

Answer 15

period of malnutrition responsible for slow growth and parallel (rather than perpendicular) orientation of trabeculae within the metaphysis
(horizontal lines across the bone from periods of malnutrition during growth)

Question 16

causes of osteopaenia

Answer 16

protein/calorie malnutrition, calcium deficiency, copper deficiency, severe GI parasitism or IBD, physical inactivity, chronic glucocorticoid excess, hormonal loss

Question 17

rickets and osteomalacia

Answer 17

Caused by Phosphorous deficiency, vitamin D deficiency
Results in defective cartilage mineralisation, bone softening and prevention of orderly degeneration of chondrocytes

Question 18

rachitic rosary

Answer 18

nodular thickenings around the costochondral junctions of multiple ribs
(associated with rickets and osteomalacia)

Question 19

fibrous osteodystrophy

Answer 19

associated with a persistent elevation of parathyroid hormone (PTH)
caused by nutritional secondary hyperparathyroidism (low calcium: high phosphorous), renal secondary hyperparathyroidism (failure to excrete P -> decreased Ca2+), or primary hyperparathyroidism (adenomas).

extensive osteoclastic resorption of bone and replacement by fibro-osseous tissue-> ‘rubber jaw’

Question 20

septic osteomyelitis

Answer 20

bone inflammation
bone responds to infection and necrotic bone by attempting to remove by inflammation and remodelling, if the necrotic bone is excessive, it is isolated by production of new bone
necrotic bone = sequestrum
surrounding new bone = involucrum
severe inflammation can adversely affect structure and function e.g. fibrosis -> instability

Question 21

portals of entry of bacteria into bone

Answer 21

direct extension - cutaneous wound, open fracture, puncture, trauma and local infection
haematogenous - commonly leads to septicaemia in a foal

Question 22

chronic osteomyelitis

Answer 22

prolonged inflammation of the physis resulting in fibrotic remodelling prone to fracture

Question 23

metaphyseal osteopathy

Answer 23

sterile inflammation
bilaterally symmetrical, fibrinosuppurative lesion causing lameness, swollen limbs, pain and fever
young/adolescent large breed dogs

Question 24

panosteitis

Answer 24

sterile inflammation in large and giant breed dogs
5-12 months of age
mild-severe lameness
usually self-limiting
increased medullary opacity of diaphysis, associated with replacement of the medullary cavity with fibrovascular connective tissue and woven new bone.

Question 25

legg-calve-perthes disease

Answer 25

small and miniature breeds of 4-8 months of age
aseptic necrosis of femoral head resulting in collapse
bilateral in 15% of cases

Question 26

primary bone neoplasia

Answer 26

Primary bone tumours arising from the bone-forming cells (osteoblasts) are the most common.
Primary bone neoplasias are more common in our canine species vs feline. In our other domestic species, they occur infrequently or rarely.

Question 27

feline-lung-digit syndrome

Answer 27

metastatic pulmonary carcinoma arises in the lungs, however, also has a predilection for the digits in cats
If you are presented in clinic with a feline patient that has swollen digits, a thoracic radiograph should be included in your diagnostic work-up.