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Phase 1 > Ch. 43-45, 47, 48 MIPO, Delayed Union, Grafts > Flashcards

Ch. 43-45, 47, 48 MIPO, Delayed Union, Grafts Flashcards

1
Q

what two components help us assess reduction of a fracture

A

alignment of the joints adjacent to the fracture and apposition of the fragments

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2
Q

what is ligamentotaxis

A

the use of ligament or tendon soft tissues nearby to aid in reducing periarticular fractures in a minimally invasive way

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3
Q

what kind of pressure will the muscle envelope of a limb apply to the fracture when under tension during distraction?

A

concentric or hydraulic pressure on the shaft of the bone, which eases the fragments into place

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4
Q

what is the energy, field of view, and accessible space for a full size C arm

A

1.4-2.3 kW or 10-23 mA
23-33 cm field of view
78 cm accessible space

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5
Q

what are three ways to minimize radiation when using the C arm in the OR

A
  1. use the lowest amount of radiation necessary for images
  2. wear appropriate shielding gear
  3. increase the distance between personnel and radiation (inverse square distance law)
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6
Q

what is the inverse square distance law

A

amount of radiation decreases proportionally with the square of the distance from the radiation source

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7
Q

why do we place the generator of the c arm below the table

A

this position will direct backscatter toward the floor instead of the upper body of the surgical team
Backward scatter or back scatter represents 25-40% of the energy of the beam and is most of the exposure we get

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8
Q

what is indirect reduction vs direct when using a traction table

A

indirect will use straps attached to the limb distal to the fracture
direct is used for proximal segments - and you will need to do some kind of wire in that proximal segment

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9
Q

where is the primary biomechanical weakness of an external fixator

A

the pine bone interface

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10
Q

what are four strategies to avoid screw placement in the joint for MIPO locking plates?

A
  1. use non locking screws directed away from the joint
  2. reduce the length of the pilot hole and use shorter locking screws
  3. bend the plate so that the screw hole axis is directed away from the joint
  4. use a slightly shorter plate
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11
Q

where is the most likely place of implant failure for MIPO plates and screws?

A

at the screw - conventional plating usually leads to fatigue of the plate and failure of the plate

  • this is because the working length is usually long so the plate is bending with its long working length
  • also, because the plate is over instead of against the cortex, the screws are cantilevered and bent
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12
Q

what direction will hinged orthoses restrict motion?

A

they will restrict motion in the plane perpendicular to the hinges

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13
Q

what is the residuum?

A

this is the residual limb or the stump that you fit an exoprosthesis to

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14
Q

what are the four tenets of bone healing and regeneration?

A

mechanics
scaffold
growth factor
cells

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15
Q

what are intrinsic healing factors that negatively impact bone healing?

A

diaphyseal cortical bone
decreased/compromised vascularity of the periosteum
sparse soft tissue attachments
aged patients

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16
Q

what layer of the periosteum is important for providing mesenchymal stem cells

A

cambrium layer

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17
Q

what is a delayed union

A

prolongation in time for fracture healing
common mechanical causes include excessive fracture gaps and motion at the fracture site
biologic causes may vary but include damage to vascular supply or periosteum
you don’t know that something is a delayed union until it finally has healed or hasn’t healed

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18
Q

what do pain on palpation of the fracture site and increasing lameness suggest?

A

insufficient stability of the repair

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19
Q

what is a non union

A

a fracture that fails to progress to osteosynthesis regardless of healing time

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20
Q

what is a malunion

A

failure of mechanical reestablishment of the form and function of the fracture in which healing still occurs

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21
Q

how does extracorporeal shock wave therapy improve bone healing?

A

direct and indirect stimulation of bone activity

clinical trials in humans suggest efficacy in hypertrophic non union but not atrophic non union

22
Q

how is pulsed electromagnetic field thought to improve bone healing

A

rapidly changing magnetic field will induce an electric field in a conductive medium
the electric field generates small currents that are thought to induce activity of bone tissues and healing callus

23
Q

what is a hypertrophic non union?

A

a type of viable non union
caused by excessive motion at the fracture site, which leads to fibrous tissue being laid down instead of bone
it is the elephant foot non union

24
Q

what is an oligotrophic non union

A

this is a viable non union and has no radiographic evidence of biologic activity (so it will look like a non viable on radiographs)
treat by removing loose implants (often loose cerclage)

25
Q

what is a dystrophic non union

A

a type of non viable non union

there is non viable (no living bone tissue) on one or both sides of the fracture

26
Q

what is a necrotic non union

A

a type of non viable non union - there is an infected section of bone (a sequestrum)

27
Q

what is a defect non union

A

a type of non viable non union
caused by a gap that is too large
also called a segmental non union

28
Q

what is an atrophic non union

A

a type of non viable non union where dead bone is removed without subsequent healing
usually not amenably to treatment

29
Q

what three factors influence the success of managing an osteomyelitis case

A

viability and stability of the bone
virulence and antimicrobial susceptibility of the organism
state or condition of the soft tissue envelope

30
Q

what are the top three most common bacteria identified in osteomyelitis in dogs and cats

A

Staphylococcus
E coli
Streptococcus

31
Q

how is a biofilm advantageous to bacterial growth

A
  • the extracellular matrix can capture and concentrate the nutrients required by organisms to survive
  • growth within the matrix provides protection from shear stresses, host phagocytic activity, protease and ROS defenses by host
  • bacteria have genotypic and phenotypic alterations and therefore an altered or quiescent growth pattern… but then most antimicrobial agents rely on bacterial growth to be effective
  • extracellular matrix is also a literal barrier to antimicrobial agents
  • microenvironment will affect the antimicrobial activity like lowering pH, decreased partial pressure of oxygen, increasing pressure of CO2
32
Q

what are the two theories for why the metaphyseal region of bone is the most commonly affected in an osteomyelitis

A
  1. within the metaphyseal region of long bones, the capillaries are characterized by an incomplete basement membrane and gaps within the endothelial cells… this may be a mechanism for bacterial translocation
  2. sluggish blood flow within the metaphyseal capillaries allows bacteria to settle and initiate colonization
33
Q

why are osteomyelitis infections usually limited to the metaphyseal side of a physeal plate?

A

transphyseal vessels are lacking at birth in dogs and cats and then the infection is restricted to just the one side

34
Q

what is an involucrum

A

An involucrum (plural: involucra) is a complication of osteomyelitis and represents a thick sheath of periosteal new bone surrounding a sequestrum

35
Q

what is the preferred method for testing for cryptococcus

A

latex agglutination test

36
Q

what are the goals of treatment of post traumatic osteomyelitis

A
  1. removal of necrotic tissue, sequestra, and foreign material
  2. meticulous debridement such that further disruption in the vascular environment is minimized
  3. biofilm removal and/or disruption
37
Q

what is the empiric antibiotic recommended for an osteomyelitis caused by Staphylococcus that is coagulase negative

A

first generation cephalosporin, nafcillin

38
Q

what is the empiric antibiotic recommended for an osteomyelitis caused by Staphylococcus that is coagulase positive

A

first generation cephalosporin, clavamox, quinolones, chloramphenicol, TMS

39
Q

what is the empiric antibiotic recommended for an osteomyelitis caused by Staphylococcus pseudintermedius

A

first generation cephalosporin, clavamox, oxacillin

40
Q

what is the empiric antibiotic recommended for an osteomyelitis caused by Actinomyces

A

penicillin

41
Q

what is the empiric antibiotic recommended for an osteomyelitis caused by Proteus, Pseudomonas, E coli

A

quinolones, aminoglycoside, second or third generation cephalosporin, ticarcillin-clavulanate, imipenem

42
Q

what is the empiric antibiotic recommended for an osteomyelitis caused by anaerobes

A

clavamox, clindamycin, metronidazole, penicillin

43
Q

what is the empiric antibiotic recommended for an osteomyelitis caused by Blastomyces, coccidiodes?

A

Itraconazole, ketoconazole, amphotericin B

44
Q

what are the four techniques of bone grafting?

A

osteogenesis
osteoinduction
osteoconduction
osteopromotion

45
Q

what is the gold standard for bone regenerative materials?

A

fresh autogenous cancellous bone grafts

46
Q

why are fresh autogenous cancellous bone grafts so great? which of the four techniques does it utilize

A

osteogenesis
cancellous bone grafts have a mix of cells - differentiated osteoblasts to undifferentiated mesenchymal stem cells in the marrow component
they revascularize faster than cortical grafts!
the live cells might produce new bone almost immediately
they really have all you need - osteoinductive/conductive/promotive

47
Q

how quickly can you reharvest bone from the same site

A

restoration (the cancellous bone returning to the donor site) occurs more completely in the proximal humerus than tibia - can repeat harvest by 8 weeks in the humerus and 12 weeks in the tibia

48
Q

what is the optimal size for cancellous particles that are harvested?

A

3-6 mm - using a #000 to #2 curette

49
Q

what are the viable cellular elements that would invoke an immune response if present on an allogeneic graft

A

periosteum, muscle, blood cells, bone marrow

50
Q

what is demineralized bone matrix

A

bone that has been ground to specific particle sizes and has been decalcified with the use of acids (like hydrochloric acid)
canine bone has 22-25% calcium before mineralization and <3% after

Phase 1 (35 decks)

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