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Describe gap healing of a fracture?

Small gaps between the fracture end, minimal movement. lamellar bone forms directly in the fracture gap. intra cortical remodelling through the fracture gap then restores bone.


Describe contact healing of a fracture?

Direct apposition of the fracture ends permits direct remodelling. new cutting cones are initiated in the region of the fracture. reduced radiographic density at bone ends adjacent to fracture site.


What are the potential complications of metaphyseal fractures?

Growth plate damage in skeletally immature animals. Always warn owners to watch for angular deformity developing.


Describe the salter harris physeal fractures

Type I - S (straight) through physis
Type II - A (above)- through physis and metaphysis
Type III - L (lower) through physis and epiphysis
Type VI - T (through) through epiphysis, physis and metaphysis
type V - R - crush


What are greenstick fractures?

incomplete fractures in skeletally immature animals where bone is incompletely mineralised, so less brittle than fully minteralised adult bone.


What are the common complications with using a cast?

Pressure sores (poor technique or loosening), ischaemia, fracture disease - muscle wasting, stiffness, osteoporosis, tissue adhesion, malunion /delayed union.


What is normograde pinning?

Introduce pin away from fracture site, reduce fracture and advance pin.


What is retrograde pinning?

Introduce pin at fracture site, push/pull pin through bone to allow fracture reduction, reduce and drive pin across fracture line.


What are rush pins and what fractures are they useful for repairing?

Have a hooked end and a sledge runner tip at the opposite end. they cross over and bounce of the opposite inner cortex. Useful for metaphyseal fractures especially at the distal femur, and may allow physeal growth to continue in skeletally immature animals.


What are the uses for cerclage wire?

to provide interfragmentary compression - it reduces the fracture gap, increases interfragmentary friction, enhances fracture stability, stops undisplaced fissures opening up or propagating from the fracture site. Fracture must be fully reconstructable. only two fragments in any circumference.


What is tension band wiring used for?

Used to repair fractures or osteotomies which are subjected to distractive forces, eg olecranon osteotomy, tibial tuberosity avulsion, malleolar fracture.


What is the use of a lag screw?

when the screw crosses a fracture line that can be compressed, it provides interfragementary compression.


What is the use of a position screw?

when the screw crosses a fracture line that cannot be compressed, when near fragment is too small to take a gliding hole. Used when a lag screw would cause a fragment to collapse into the medullary cavity.


What are the symptoms of acute osteomyelitis?

Localised pain, swelling, pyrexia, anorexia, lethargy, usually 2-3 days post surgery.


What are the radiographic signs of osteomyelitis?

Bone destruction, periosteal new bone formation, soft tissue swelling, sequestrum formation (isolated fragment of dead bone separated from normal bone), delayed or non union


What should you do with a fracture that has osteomyelitis?

For a stable healing fracture - maintain fixation, fractures will heal in the presence of persistent infection.
For A healed fracture - remove implants. for an unstable fracture - revise fixation to provide rigid stability. Remove sequestrae - may need to graft significant deficits with a cancellous autograft. Establish drainage/lavage.


Why does a viable non union fracture occur?

Usually arise due to inadequate stability of the fracture site, also from inadequate reduction. Should heal following adequate stabilisation.


Why does a hypertrophic non union fracture occur?

Highly vascular fracture site, significant callus - bone is atempting to heal. Remove loose implants and stabilise fragments. swab tissues for c&s.


What are the four types of non viable non union fractures?

Dystrophic - blood supply inadequate
Necrotic - necrotic tissue in fracture site.
Defect - bone defect at fracture gap
Atrophic - sequel to the above. Biologically inactive. no evidence of attempt to heal. bone ends are sclerotic and atrophic. medullary cavity may seal over. Fracture gap fills with fibrous tissue.


What types of dog are prone to atrophic non union fractures?

Toy breed dogs with distal radius and ulna fractures.


What is an autograft?

donor and recipient are the same individual


what is an allograft?

D&R are different animals of the same species.


What is a syngenesiografT?

D&R are blood relatives.


What is an Isograft ?

D&R have identical genetic background.


What is an Xenograft?

D&R are form different species.


Where can a cancellous autograft be collected from?

Lateral tuberosity of humerus
Medial proximal tibia
Greater trochanter of femur
Wing of ilium
(highly cellular but mechanically weak)


What are the advantages and disadvantages to a cancellous autograft?

No immune response, greatest osteogenic effect as has high cellularity, no risk of cross infection.
Disadv- extra operating sites must be prepped and accessed, large quantities can be difficult to obtain.


What are the advantages and disadvantages to cortical bone allografts?

Can be banked, convenient, unlimited quantity.
Disadvantages - immunogenic, slow incorporation into host bone, risk of cross infection. Need strict asepsis since implanting a dead piece of bone. Osseointegration within 1-3 months but complete substitution may take years. Complications are common; infection, rejection, fracture, sequestration.


Describe the composition of bone & the cells present in bone

Organic matrix made mainly of collagen. Mineral - calcium hydroxyl apatite. Osteoprogenitor cells. Osteoblasts (synthesise bone matrix and express osteogenic growth factors), osteocytes (terminally differentiated osteoblasts), osteoclasts - responsible for demineralisation and degradation of bone matrix.


How is calcium kept in homeostasis?

Parathyroid hormone - increases plasma calcium concentration. (mobilises calcium from bone, increases calcium reabsorption in the distal tubule of nephron, increases urinary phosphate excretion) Calcitonin - lowers plasma calcium concentration. (reduces calcium resorption from the bone)
Vitamin D3 (calcitriol) - increases plasma calcium concentration. Increases plasma calcium concentrations by increasing intestinal absorption of calcium, mobilising calcium from bone and causing calcium resorption in the kidney.