Musculoskeletal - Bones Flashcards
2 types of abnormalities related to bones
abnormality of gait and abnormality of form
(often present clinically together)
Wolff’s Law
the idea that natural healthy bones will adapt and change to adapt to the stress that it is subjected to
Pathological fractures
associated with processes that weaken the bone - predisposing it to fracture
(fracture is caused by an underlying disease)
process of fracture healing
- Hematoma formation
- Growth factors produced from macrophages and platelets stimulate granulation tissue formation (hours to days)
- Mesenchymal cells differentiate into osteoblasts (days)
- Early callus formation initially contains cartilage. The cartilage functions to anchor and create a more stable environment for the production of woven bone (days)
- Primary callus of woven bone (weeks)
- Remodelling of woven bone into lamellar bone into a secondary callus (weeks to months to years)
list some factors that can delay the healing of fractures
excessive movement
reduced blood supply / poor nutrition
tissue necrosis
infection
pathological fracture e.g. neoplasia
metallic implants
chondrodysplasia
widespread abnormality of growth cartilage
localised in some breeds - basset hound, dachshund
inherited and often lethal (bulldogs, spider lambs)
osteopetrosis
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
3 types of osteopetrosis
- inherited - bones have a large thickened area but the trabeculae are fragile
- infectious disease - growth retardation lattice (region of thickening near physis)
- toxic - lead
disorders of bone formation
angular limb deformities
feline physeal dysplasia
angular limb deformities
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
most common angular limb deformity in dogs
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.
feline physeal dysplasia
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.
metabolic bone diseases
osteoporosis / osteopaenia
rickets and osteomalacia
fibrous osteodystrophy
difference between osteoporosis and osteopaenia
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.
what are growth arrest lines?
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)
causes of osteopaenia
protein/calorie malnutrition, calcium deficiency, copper deficiency, severe GI parasitism or IBD, physical inactivity, chronic glucocorticoid excess, hormonal loss
rickets and osteomalacia
Caused by Phosphorous deficiency, vitamin D deficiency
Results in defective cartilage mineralisation, bone softening and prevention of orderly degeneration of chondrocytes
rachitic rosary
nodular thickenings around the costochondral junctions of multiple ribs
(associated with rickets and osteomalacia)
fibrous osteodystrophy
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’
septic osteomyelitis
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
portals of entry of bacteria into bone
direct extension - cutaneous wound, open fracture, puncture, trauma and local infection
haematogenous - commonly leads to septicaemia in a foal
chronic osteomyelitis
prolonged inflammation of the physis resulting in fibrotic remodelling prone to fracture
metaphyseal osteopathy
sterile inflammation
bilaterally symmetrical, fibrinosuppurative lesion causing lameness, swollen limbs, pain and fever
young/adolescent large breed dogs
panosteitis
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.
