Bones Flashcards
Cortical bone
-mostly in the shaft (diaphysis)
-dense
-stiff
Cancellous bone
-aka trabecular or spongey bone
-shock absorbing
-can compress
-mostly in the epiphysis of the bone
Osteocytes
mature bone cells
-sensing and signaling
Osteoblasts
bone builders
-secrete osteoid, collagen-based bone matrix
Osteoclasts
bone dissolvers
-cause release of calcium
Bones are…
dynamic
-mineralization and demineralization are continual
Osteoporosis
“brittle bones”
-demineralization exceeds mineralization
-common at old age
Osteomyelitis
infection in a bone
Periostitis
new bone growth (deposition) associated with irritation, trauma to an area of the periosteum
Common locations of periostitis
-between the splint bones and cannon (“splints”)
-at the insertion of tendons or ligaments (most common in lower leg/pastern)
-can also occur in response to trauma to an area
Splints
a form of periostitis
-more common on front limbs (the medial aspect)
-can be sore when it first happens
-more common in young horses
Ring bone
a form of periostitis
-new bone proliferation at the insertion of the extensor tendon
-usually on the short pastern
-common in horses that work on hard surfaces or horses that have a lot of animation
-can cause lameness if it bridges over the pastern
Types of fractures:
-open or closed
-complete or incomplete
-comminuted
-displaced or non-displaced
Open fracture
skin in broken and the bone is exposed,
increased risk of infection
Closed fracture
bone is fractured but did not break skin, much better than an open fracture
Complete fracture
in two pieces
Incomplete fracture
only cracked (not completely broken in two)
Comminuted fracture
a type of complete fracture
-bone is in many pieces or shattered
Displaced fracture
the bone fragment has moved from its original site
-the fragment can puncture the skin or damage the neurovascular bundle (if in the legs) and cause more damage
Non-displaced fracture
bone is aligned as it should be, just fractured. Better than a displaced fracture
The three phases of bone healing:
-inflammatory phase
-reparative phase
-remodeling phase
Inflammatory phase of bone healing
- hemorrhaging, clot, inflammatory cells arrive (heat, pain, swelling)
- increase blood flow
- osteoclasts arrive and will clean up bone debris in the area
Reparative phase of bone healing:
- chondrocytes and fibroblasts arrive, deposit collage to begin the formation of a soft callus (over the fracture site) – 1-2 weeks
- osteoblasts arrive and deposit osteoids, osteoids form the matrix that will be mineralized
- mineralization of osteoid begins formation of the hard callus, bone formation may occur outside the boundary of the original bone – 2-4 months
Remodeling phase of bone healing:
- may overlap with reparative phase
- osteoclasts remove excess bone mass at fracture site…returns bone to original shape (can take several months)
- bone strength can return to normal
What affects bone healing rate?
-extent and location of damage
-type of fracture (open comminuted/displaced is the worst)
-age of animal (young faster than old)
-ability to stabilize (prevent further damage and the proximity of pieces to each other)
-amount of associated soft tissue damage
Internal fixation
a type of fracture repair
-putting in screws to stabilize the bone
-sometimes screws are left in, sometimes they are taken out
What is the main goal of fracture first aid?
to prevent closed, incomplete fractures from becoming:
-open
-complete
-comminuted
-displaced
Intramembranous ossification
-bones get thicker; osteoclasts and osteoblasts
-occurs primarily in the periosteum
The periosteum is more active in…
young animals
Intramembranous ossification occurs in adults in response to:
exercise, the bone can get thicker
Endochondral ossification
bones get longer (horses get taller)
Where does endochondral ossification occur?
at the growth plate (physis)
When does endochondral ossification stop?
occurs until the physis closes
-not all physes close at the same time
-some are closed at birth; others close later than 2 years old
The process of endochondral ossification
-chondrocytes multiply and form columns
-chondrocytes hypertrophy (columns are invaded by blood vessels and chondrocyte formation/lysis)
-osteogenesis
-remodeling (attaining the final shape)
Osteomylitis
infection of the bone
Osteogenesis
bone formation
When does the physis at the proximal P-1 then distal cannon close?
4-8 months (long pastern first than distal cannon)
When does the physis at the distal radius and tibia close?
18-24 months or later
Which grows longer the cannon or the radius?
the radius (cannons are relatively the same size when the foal is born to when they mature)
What % of their mature height are foals when they are born?
about 50-60%
When does a horse normally reach 100% mature height?
around 2.5-4 years old
What % of their mature weight are foals when they are born?
about 10%
When foals are born they are shaped more like an…
upright rectangle
What part of a horse typically grows faster in height?
the hind end
Horses may reach mature height …
before mature weight, length, and width
Defects in early skeletal development may have long term effects on:
-conformation
-movement
-bone strength
-joint function
Developmental orthopedic disease (DOD)
a collection of different developmental bone and joint issues
DOD includes:
-physitis
-flexural and angular deformities
-osteochondrosis
Physitis
inflammation around the physis (growth plate)
-usually the metaphyseal growth plate
-often mild and resolves with no long term significance
Most common locations of physitis
-fetlock (in foals and weanlings, short yearlings)
-knee (weanlings and yearlings, sometimes 2 yr olds)
If physitis is severe what can occur:
-can cause lameness or uneven loading
-can make angular deformities worse
Physitis can be worse with/in
-big bodied foals
-with hard surfaces
Flexural defects
see it from the side, difficult to resolve
-over at the knee
-back at the knee
-upright pasterns
-club foot
Angular defects
seen from the front, easier to resolve; may be present at birth and improve or worsen with growth
-in at the knee/carpus valgus
-carpus varus
-toed in/out
-cow hocks
If something is congenital
they were born with it
What can angular deformities result in?
uneven loading in joints and physes which can create more damage
-surgical approaches effective when the physis is still active
Transphyseal “bridge”/screw
screw placed across physis on fast growing side (not joint)
-allows slow growing side to catch up and then the bridge is removed
-bones will heal the holes
Osteochondrosis
defect in normal conversion of cartilage to bone at growth plate
-most defects are initiated before 1 year of age
-some defects may resolve
Osteochondrosis can result in
-areas of reduced mineralization (lucencies)
-osteochondritis dissecans (OCD) lesions
-lameness depending on site and severity, type of horse activity
-weakened areas in the bone
The two types of physis:
epiphyseal
metaphyseal
OCD lesion
an area on the bone that is not well defined and rough and sometimes cracked
Subchondral lucency
a bone cist
-area of the bone that is less dense and weaker
Risk factors for DOD
-genetics
-environment (housing)
-health/exercise
-diet
The most important age to try to prevent DOD is:
0-20 months old
When is the equine skeleton fully mature?
3-5 years old
Epidemiology
the study of the distribution and determinants of health-related states or evens in specified populations and the application of this study to the control of health problems
Epidemiology is important because it:
allows evaluation of large numbers of animals, across many conditions
From the studies, was early exercise detrimental?
not really from the data provided
From the studies, was early exercise beneficial?
possibly
