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AO > AO_chapters > Flashcards

AO_chapters Flashcards

1
Q

preop management of fx patient

A

ABCDairway, breathing, circulatory, other disabilitiesSPO2, auscult, IV access/fluids, imaging, full ortho neuro PE

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2
Q

benefits to pain mgmt for fx patient

A

decrease anxiety/stress and it’s associated hormonal and metabolic derrangementsprovide patient comfort

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3
Q

most effective analgesic time period

A

PRIOR to onset of pain (surgery)

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4
Q

advantages of multimodal pain therapy

A

selectivity to target multiple sites of pain pathadditivite/synergismreduced dosingreduced toxicity

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5
Q

define neuroleptanalgesia

A

combo of neuroleptic drug (ace) and analgesia (opioid)

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6
Q

infection rate of CLEAN ortho procedures

A

2.5-4.8%

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7
Q

most common isolate causing ortho infxn

A

Staph intermedius

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8
Q

host risk factors for sx infection

A

age (>8yrs) obesitydistant infection, endocrinopathyinadequate skin prepprolonged axpropofol

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9
Q

intraop risk factors for sx infection

A

sx > 90 mexcessive electrocauterybreak in asepsisbraided/multifilament sutureimplants

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10
Q

use of periop prophy Ab decreases rate of infxn_______

A

use of periop prophy Ab decreases rate of infxn 4 fold in clean procedures.

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11
Q

traditional recommendation for prophy Ab in clean procedure

A

in clean procedures generally NOT indicated UNLESS>90m surgerymetal implants usedextensive ST damagecefazolin–bactericidal given IV 30 min prior to sx

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12
Q

AO fracture classification

A

1 humerus2 RU3 femur4 tib/fib1=prox2=shaft3=distalA= single fxB= wedge/butterflyC=complex

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13
Q

open fracture classification

A

I. bone penetration thru skin (small puncture hole/laceration < 1 cm); CLEANII. > 1cm laceration with fracture communicating with skin; mild ST traumaIII. A severe comminution; hi energy, ST flaps but available for wound coverageIII. B severe comminution; hi E; bone exposure; periosteum strippedIII. C severe comminution; hi E; bone exposed with damage to arterial blood supply

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14
Q

physeal fracture classification

A

Salter HarrisI growth plate II growth plate metaphysealIII growth plate epiphyseal (intraarticular)IV metaphyseal/epiphyseal (intraarticular)V compressionVI asymmetric compression

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15
Q

objectives for fracture repair

A

reduction/alignmentrigid stabilization/immobilizationmaintain blood supplyearly return to normal function

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16
Q

mechanical and biological factors for fractures

A

mx: fx configuration, reconstruction or not, concurrent ortho injurybx: age, fracture location, ST injury

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17
Q

pros/cons to open vs closed reduction of fx

A

open: visualization, bone grafting, anatomical recon BUT incr sx time and ST injury/blood supplyclosed: preserve ST/blood supply, decr contamination BUT at the expense of fracture alignment/recon

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18
Q

Three ways of fracture planning

A

direct overlaybone specimenintact contralateral bone

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19
Q

major benefit of fully reconstructed boney column

A

shares the wt bearing load of the limb during fx healing

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20
Q

review of post op radiograph criteria

A

4 AsA=appositionA=alignment (50% is necessary to prevent delayed union)A=apparatusA=activity

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21
Q

rehabilitation goals

A

prevents musculoskeletal disabilitydecreases healing timefacilitates restoration of normal function

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22
Q

rehab includes

A

cryotherapy–ICE in acute < 72 hr period; vasoconstrict, min fluid/edema, decr nerve conduction, encourage muscle relax; w compression decr temp by 27 deg Cheat therapy– > 72 hr period, vasodil (NOT in nerve patient); incr metabolismmassage–incr local circulation, decr muscle spasm, attentuate edema, brkdown scar tissuetherapeutic exercise–pROM; maintain normal joint motion, sensory awareness, blood flow improvement; build strength, agility/coordinationtherapeutic US–treats chronic scare and adhesions NM stimulation–creates artificial contraction

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23
Q

types of massage

A

EFFLEURAGE–superficial/light strokingPETRISSAGE–kneadingTAPOTEMENT–percussion/tapping

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24
Q

biological fracture healing goals

A

flexible fixationeliminate anatomic reconstructioncreate axial alignmentless surgical traumaindirect bone healing w calluspreserve blood supply

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25
Q

role of screw

A

interfrag compressionfixing of a splinting device (plate, nail, fixator)

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26
Q

difference btwn cancellous and cortical screws

A

cancellous screws1. larger outer diameter (thinner inner core)2. deeper thread3. larger pitchused in metaphyseal and epiphyseal bone

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27
Q

cortical screw

A

used in diaphysisas size increases strength increasesscrew diameter should not exceed 40% of bone diameter

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28
Q

3.5 mm cortical screw characteristics

A

2.4 core diameter (use 2.5 drill bit)3.5 thread diameter6 mm head hexagonal recess

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29
Q

T/F self tapping screws can be used as lag screws

A

FALSE; avoid self tapping screws to be used in lag fashion bc may cut a new hole/threads

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30
Q

what is a shaft screw

A

cortical screw with short threads and a shaft that has a diameter equal to that of a threadused as a lag screw in diaphyseal bone

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31
Q

what is a cannulated screw

A

central hollow cored and are inserted over K wires that act as a guide.3.5 mm cortical6.5 mm cancellous

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32
Q

application of a lag screw

A

can use fully or partially threaded NONself tapping screwsfully threaded: overdrill CIS cortex (gliding hole= thread diameter)partially threaded: threaded portion only engages TRANS cortex

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33
Q

Lag screw insertion guidelines

A

EQUIDISTANT from fracture edges (middle of the fragment)PERPENDICULAR to the fracture planeconsider countersink (remeasure) and washer to evenly distribute forces

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34
Q

what happens if the lag screw is NOT perpendicular to the fracture plane

A

shear forces displace fracture fragments

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35
Q

rule of thumb for tightening plate/screw based on screw sizes

A

2.0 mm two fingers2.7 mm three fingers3.5 mm whole hand

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36
Q

screw placement into plate to ensure axial alignment of the plate to the bone

A
  1. screws are first applied at each end of the platethen close to the fracturefinally remaining holes are filled2. ALT if straight alignment, fill closest to fracture firstthen alternate filling towards the end of the plate
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37
Q

functions of a dynamic compression plate

A

compression (eccentric), neutral (middle), bridging, or buttress

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38
Q

hole design of DCP allows compression and how much displacement of the fracture fragments

A

1.0 mm per DCP hole using 3.5/4.5 mm 0.8 mm per DCP hole using 2.7 mmcan place one or two compression screws on either side of the fracture (have to loosen first screw on same side to move fragment and then retighten)

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39
Q

oval shape of DCP holes allows what degree of screw angulation

A

25 degrees longitudinally7 degrees transversally

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40
Q

gold eccentric drill guide is how far off center

A

1.0 mm (therefore allows for compression)

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41
Q

available metal for LCDCP vs DCP

A

DCP stainless steelLCDCP stainless steel and titanium (outstanding tissue tolerance)

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42
Q

limited contact dynamic compression plate (LC DCP) advantages

A
  1. scalloped underneath-allows for the area of the plate/bone contact or footprint to be greatly reduced)-spared capillary network under the periosteum-even distribution of stiffness (limits stress risers at screw holes)-makes contouring easier-does not “kink” plate holes2. symmetrical plate holes-allows eccentric screws in either direction-plate holes are evenly distributed
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43
Q

symmetrical shape of LCDCP holes allows what degree of screw angulation

A

40 degrees longitudinally7 degrees transversally

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44
Q

what drill guide is used in LCDCP

A

universal spring loadedcompressed–>neutral positionnot compressed–>eccentric placement for compression

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45
Q

Veterinary cuttable plates use

A

versatile and used in small animal patientscan be cut to lengthcan be stacked to incr stiffness; but relatively weak plate1.5/2.0 mm2.0/2.7 mmNOT A COMPRESSION PLATE; circular round holes

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46
Q

reconstruction plate use

A

deep notches inbtwn holescontouring can occur in an additional planeoval holes allow for compression

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47
Q

types of special veterinary plates

A

acetabular plates; T/L plates; Double hook plates (prox femur); TPO plates; tubular plates

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48
Q

compression vs neutralization plate functions

A

compression: reducible fractures (simple transverse); axial compressionneutralization: plate protects interfragmentary compression; neutralizes bending forces

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49
Q

prebending plate functions to…

A

…prebending plate 2 mm at fx line functions to compress opposite cortex

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50
Q

Buttress vs bridging plate functions

A

buttress: prevents collapse of fx (ex. metaphyseal fx); plate is subject to full loadingbridging: nonreducible comm fx; aka biological plating; long and strong plate used; subjected to full loading; maintains length/alignment and prevent axial deformity; CALLUS

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51
Q

implant combo particularly effective for bridging application

A

plate-rodsynergistic mechanical propertiesrod 40-50% medullary canal diameter–> increases fatigue life of plate, decr strain on empty screw holes

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52
Q

advantages of locking plate/screw systems

A

Stability btwn screw and plateplate does NOT need intimate contact with boneplate does NOT rely on frictionexact contouring NOT essentialreduced contact w bone maintains blood supplymay reduce bone resorption under the plate

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53
Q

LCP locking compression plate

A

COMBINATION hole plate (conventional–angle or compression or locking screw)3.5 mm or 4.5 mm systems

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54
Q

locking head screw (LHS)

A

self tappingconical threaded head and threads/locks into plate

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55
Q

unilock plate system

A

2.0 mm or 2.7 mm systemslocking plate/screw design

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56
Q

CRIF Clamp rod internal fixator system

A

excellent versatilitygood contouring capabilityease of applicationminimal instrumentationminimal contact with bone

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57
Q

contouring of plates rules of thumb

A

repeat bending should be avoided because it weakens the platebend plate btwn holes to avoid stress riserslocking plates should used bending teesbending press, hand held pliers, bending irons

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58
Q

pros to positive profile pins

A

shaft diameter is the same throughout the pin reduces bending stress; stronger; better bone purchasethread diameter is greater than shaftpredrilling a hole smaller than core diameter improves quality

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59
Q

T/F double clamps are as strong as single clamps

A

FALSE:double clamps may be used to connect one connecting bar to another NOT as strong as a single clamp

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60
Q

types of ESF connecting bars

A

Stainless steel (historically)Carbon fiber–radiolucentTitaniumAcrylic/epoxy

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61
Q

T/F Mechanical studies show that a 19 mm diameter acrylic/epoxy bar has similar rigidity as 3.175 mm stainless steel bar

A

TRUEMechanical studies show that a 19 mm diameter acrylic/epoxy bar has similar rigidity as 3.175 mm stainless steel bar

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62
Q

advantages of ESF application

A

great in areas of less soft tissue coverage, also mand/maxapplied closed +/- fluoropreserves blood supply

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63
Q

Rules of thumb w ESF fixation

A

AVOID ST/neurovascular structuresAvoid ST injury with use of half pins/unilat framediameter pins < 25% diameter bonemin 2 pins per fragment (3 optimal) placed at least 2 pin diameters from fracture edge

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64
Q

T/F Bilateral ESF are more stable than unilateral ESF

A

TRUE BUT bilateral ESF penetrate the skin twice and lead to more ST injuryBest avoided if two unilateral ESF in two different planes (biplanar configuration)

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65
Q

angled vs parallel pins in ESF

A

Angled pins offers mild incr stabilityMORE threaded parallel pins > purchase to fewer angled pins

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66
Q

ESF clamp placement

A

bolt locking the pin should be placed closest to the bone to shorten the pin length and stabilize the frame~ 1 cm away from skin

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67
Q

ILN interlocking nail

A

stainless steel into IM cavity held by bolts/screwsresist axial, bending, and rotation

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68
Q

standard ILN has bolts how far apart

A

6.0 mm ILN 22 mm apart8.0 mm ILN 11 mm apart

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69
Q

bolts used with ILN

A

VERY STRONGonly threaded into near cortexrest of shaft is unthreaded and has increased bending strength

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70
Q

what mode are ILN placed?

A

bridgingused in nonreducible comm fx; aka biological; subjected to full loading; maintains length/alignment and prevent axial deformity; CALLUS

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71
Q

ILN can only be passed (normo or retrograde)

A

ILN can only be passed NORMOgradeBUT can prepare the medullary canal with retro or normograde

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72
Q

ILN lock which side (prix or distal) fragment first

A

pass ILN normogradelock DISTAL fragment first with screw/bolt after achieving length/alignmentcorrect for rotation and additional alignment prior to locking proximal piece

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73
Q

how to remove ILN

A

first remove screws/boltsattach extension setextract nail

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74
Q

IM pin alone recommended diameter and counteracting forces

A

should be ~70% bone diameter at isthmusonly resists bendingNOT collapse NOT rotationstainless steel aka steinmann pin; adjunct repair is necessary to counteract all forces

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75
Q

most common point style for IM pin

A

Bayonet3-face trocarDiamond point

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76
Q

difference between steinmann pin and k-wire

A

both stainless steelk-wire 0.8-2.0 mmsteinmann pins 2.0-5.0 mm

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77
Q

most effective way of counteracting rotational and axial forces around an IM pin

A

addition of ESF (tie in or IM pin + ESF)

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78
Q

how to add bending strength to IM pins

A

STACK with 2-3 pins in medullary cavity to incr bending strength but does little to axial or rotational stability.

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79
Q

repair of distal physeal fractures and pins

A

CROSS PINfragments must have good contact and ideally interdigitate to resist rotation

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80
Q

recommended IM pin diameter when using plater rod

A

plate rod = buttress mode (prevents collapse)reduced bending stress<50% bone diameter

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81
Q

orthopedic wire material

A

316L stainless steelmalleable 16-24 gaugethe larger the diameter the greater the bending and tensile strengthdo not kink or have tissue inbtwn wire and bone

82
Q

ideal fracture configuration for using orthopedic cerclage wire

A

long oblique fracture where fracture length is at least 2 x the diameter of the bone

83
Q

how many cerclage wire is recommended per fracture fragment

A

at LEAST 2 cerclage per fracture fragmentspaced between half to one bone diameter apartshould be placed perpendicularly to fracture (can use skewer pin to hold) USED AS ADJUNCT REPAIR

84
Q

forces that cerclage wire may counteract

A

axial compression some rotation

85
Q

three methods of tying cerclage wire

A

TWIST —must twist and pull evenly so wires wrap along each other, NOT one over the other; alt. twist and flatten techniquesingle loopdouble loop

86
Q

with twist cerclage, how many twist should remain prior to cutting the wire

A

cut with 2-3 twists remaining with twist and pull methodcut with 5-6 twists remaining with twist and flatten methodDO NOT bend (will decrease initial tension)

87
Q

with loop cerclage how much wire remains when cutting wire off

A

use wire tightenerachieve max tension, bend wirerelease tension and wirebend wire armcut with 0.5-1.0 cm remaining and press flat

88
Q

tension and load to failure for 1.0 mm twist, single and double loop cerclage

A

tension load at failuretwist 70-100 N fail at 260 Nsingle 150-200 N fail at 260 Ndouble 300-500 N fail at 666 N (2.6 x stronger)

89
Q

repair of avulsion fractures

A
  1. lag screw (may predispose small fracture piece to break)2. two pins and cerclage (pin and tension band tech)
90
Q

pin and tension band technique for avulsion fx repair

A

pins placed perpendicularly to fracture and parallel with each other (to counteract rotation)tension band counteracts tension forces and places them into compressive forces across the fracture site

91
Q

where to drill the hole to pass a tension band

A

hole is drilled transversely approx the same distance below the fracture line as the pins are above the fracture line

92
Q

three phases of bone healing

A

inflammatory : 3-5days; disruption of blood vessels, hematoma, lack of mechanical supportrepair: hematoma replaced with GT (angiogenesis/capillary regrowth/growth factors for bone formation), slight incr in mechanical strengthremodel: wks to months, incr strength as fibrocartilage is formed and remodeled to bone (Haversian progress)

93
Q

the amount of callus produced in healing depends on what…

A

the amount of callus produced during healing depends on the stability of the fracture (greater instability, greater callus)

94
Q

define strain

A

strain is defined at the deformation (or change in gap) occurring at the fracture site relative to the size of the gapthe amount of strain influences the type of tissue that forms in the fracture gap

95
Q

bone formation and strain

A

the amount of strain influences the type of tissue that forms in the fracture gapbone forms only in stable environment with very LOW strain < 2%

96
Q

source of growth factors in inflammatory phase

A

first source of mitogenic growth factors= platelets at the site of traumaPDGF, TGF Bother angiogenic factors : endothelial derived VEGF, acidity, PG E1 and PG E2later, macrophages stimulate fibroblasts thru FGF to initiate fibroplasia

97
Q

source of blood supply in initial healing phases

A

EXTRAOSSEOUStransient, but comes from adjacent soft tissuesrevascularizes the hypoxic fracture site.

98
Q

what does resorption of fracture ends do for inter fragmentary strain

A

widens the fracture gaplowers strain (but still remains hi)minimizes deformation in local tissues

99
Q

repair phase characterized by what cell type and tissue

A

mononuclear cells (macros) and stimulation of fibroblastscapillary ingrowthGRANULATION TISSUEincr in mechanical strength, but strain remains hiCOLLAGEN more abundant (initially I, II, III) TYPE I COLLAGEN PREDOMINATES

100
Q

collagen fibers in repair phase of bone healing resist how much elongation

A

collagen fibers resist elongation up to a max 17%

101
Q

where do mesenchymal cells originate from in order to ddx to chrondrocytes or osteoblasts during repair phase

A

mesenchymal cells within cambium layer of periosteum, endosteum, bone marrowbeing proliferating and ddx to chondrocytes or osteoblasts during repair phase

102
Q

tissue types included in the repair phase of secondary bone healing

A

hematoma–> GT –> connective tissue–> cartilage –> cartilage mineralization –> woven bone formation

103
Q

external callus results in increased diameter of the fracture—which leads to what

A

strength incr by power 3rigidity incr by power 4decreases interfrag strain

104
Q

ultimate tensile strength of compact bone

A

130 Nm/mm^2ability to elongate is < 2%

105
Q

T/F at the end of repair phase, the injured bone has regained enough strength and rigidity to allow low impact exercise

A

true

106
Q

remodeling phase in bone healing

A

is a balance btwn osteoclastic resorption and osteoblastic deposition governed by Wolff’s law and modulated by piezoelectricity

107
Q

define pizoelectricity

A

a phenomenon in which electrical polarity is created by pressure exerted in a crystalline environmentwith axial loading, electropositive convex (osteoclastic); electroneg concave (osteoblastic)

108
Q

what do medullary implants do to bone blood flow

A

IM pins and/or reaming of medullary cavity temporarily disturb blood flowcauses reversed centripetal flow for intense bone remodeling at bone fx site

109
Q

unreamed vs reamed ILN affect on blood flow

A

unreamed attenuates blood flow 30%reamed attenuates blood flow 70%

110
Q

biological fixation of comminuted fractures is associated with…

A

incr callusaccelerated radiographic unionearlier gain in strengthearly return to normal function

111
Q

Primary or direct bone healing

A

stable fracture fixationwithout callus formationdirect osteonal proliferationinclude both gap and contact healing

112
Q

how do gap and contact healing of direct/primary bone healing differ from indirect/secondary bone healing

A

Both gap and contact healing (direct/primary healing) differ from indirect/secondary bone healing by the ABSENCE of resorption of the fracture ends

113
Q

contact healing of primary bone healing occurs when?

A

< 0.01 mm defectinterfragmentary strain < 2 %=primary osteonal reconstruction, w lamellar bone oriented normally initiated by cutting cones

114
Q

define cutting cone

A

cutting cones occur in contact primary bone healingclosest to fracture linesosteoclasts line the spearheadosteoblast follow in the rear so that boney union and Haversian remodeling occur simultaneously

115
Q

daily progress of of cutting cones across a fracture site

A

50-100 micrometers/day

116
Q

difference btwn contact and gap healing of primary bone healing differ

A

contact < 0.01 mm defect; boney union and remodeling occur simultaneously;lamellar bone in normal orientationgap: 0.008-1 mm defect; boney union and remodeling occur in two separate steps; lamellar bone perpendicularBOTH FORM BONE WITHOUT CALLUS

117
Q

define gap healing

A

0.008-1 mm defectinterfragmentary strain < 2 %boney union and remodeling occur in two separate stepslamellar bone oriented perpendicularly (weaker) w secondary osteonal reconstruction (3-8 weeks)

118
Q

goals of biological fracture fixation

A

restore length, alignmentlimit manipulation and disruption of ST, hematoma

119
Q

perferred techniques for stabilization with biological fracture fixation

A

ESFILNMIPO

120
Q

considerations for what adjunct therapy to promote biologic osteosynthesis

A

fresh autogenous graftautogenous cancellous is most effective material to promote healing (osteogenic, osteoinductive–controversial, osteoconductive)

121
Q

properties of bone grafts

A

osteogenic–graft that supplies/supports bone forming cellsosteoinductive–induces bone formation in a site where no bone will occur normally (recruits to the area); demineralized bone matrixosteoconductive–scaffoldosteopromotion–enhancement of regenerating bone; PRP

122
Q

Properties of demineralized bone matrix

A

most commonosteoinductive, osteoconductivechemical sterilization

123
Q

rank the areas for greatest autogenous cancellous bone collection

A

ilium > prox humerus > medial proximal tibia

124
Q

how soon after should one wait to take a second cancellous autograft from the same location

A

12 weeks for femoral or humeral site

125
Q

cell viability for fresh cancellous autograft

A

85-100% decreases to 57% if in blood soaked sponge 3 hrobtain immediately after fracture reduction/stabilization in order to use fresh

126
Q

only osteoconductive implants with biomechanics properties

A

Frozen segments of allogenic bone(autogenous cancellous graft has scaffold properties but does NOT have mechanical support)

127
Q

main complication with allogenic bone segment

A

incomplete resorption–>fatigue failureinfection

128
Q

osteoconductive calcium sulfate

A

medical gradevoid filler in non weight bearing applicationscompletely resorbed 2-5 weeks in animals+/- impregnated with Abaffordable

129
Q

Bioceramic osteoconductive examples

A

Hydroxyapatite (HA)Tricalcium phosphate (TCP)HA slower to resorb that TCPporosity for bone ingrowthradioopaque (can interfere with rads)

130
Q

periosteal stripping in immature animals

A

results in production of a callus AWAY from the bone as osteoprogenitor cells get pulled with the periosteum

131
Q

three factors that affect the size of bone callus

A
  1. interfragmentary strain2. local blood supply3. hypoxia (encourages chondrocytes>osteoblasts)
132
Q

radiographic signs of indirect bone healing

A

5-7 days post op–widening of fracture edges10-12 days post op–mineralization of callus (boney callus)30 days post op–disappearance of fracture line90 days post op–complete remodeling

133
Q

4 A’s of radiographic assessment of bone healing

A

alignmentappositionapparatus/implantsactivity/healing

134
Q

T OR FClinical union is faster in sites with abundant cancellous bone and highly vascularized marrow (metaphysis)

A

TRUE

135
Q

indications for plate removal

A
  1. osteomyelitis2. pain on palpation of bone3. radiographic evidence osteopenia
136
Q

T OR FFractures undergoing direct primary healing are initially stronger than those undergoing indirect bone healing with callus

A

FALSEFractures undergoing direct primary healing are initially WEAKER than those undergoing indirect bone healing with callus pg 92

137
Q

define a delayed union

A

fracture that takes longer to heal than anticipatedquantitative judgement–no specific timeline, need serial radiographsshould be suspected when limb is more painful and use is less than anticipated

138
Q

Causes of delayed union

A

factors that negatively influence fracture healing1. biological–vascularity/infarction–initial contamination (ie. open wounds)–concurrent systemic disease/trauma2. Mechanical–stability (creates motion and incr intrafragmentary strain that exceeds tissue tolerance)–MOST IMPORTANT FACTOR–initial trauma–initial transportation of patient

139
Q

what is the fate of a piece of bone that has been deprived of its vascular supply

A

sequestrum (dead/dying bone–radiolucent)surrounded by an involucrum (new bone–radioopaque)cloaca

140
Q

Implant related factors leading to instability of fracture and subsequent delayed union

A

small implant sizeinsufficient bone purchase/contactthreaded (better than) smooth pins

141
Q

T/Fstability = rigidity

A

FALSE Stability should NOT be confused with rigidityex. circular ESF

142
Q

treatment of delayed union

A

continuing or augmenting the technique originally usedrather than changing it completely (unless external coapt–change to internal fixation)continued monitoring for bone healing+/- bone graft augmentation +/- bigger implant/stable implant if needed

143
Q

define nonunion

A

fracture that has failed to heal and does NOT show signs of any further healing/progressionusually several months

144
Q

classifications of nonunions

A
  1. viable/biologically active–variable amounts of callus but failed bridging2. nonviable/biologically inactive–no callus
145
Q

Causes of nonunion

A
  1. poor decision making and technical failure; inadequate fracture fixation–>instability, hi strain2. big fracture gap3. vascularity (toy breed dogs distal radius)
146
Q

what can happen (rare) to a biologically active nonunion that has variable amounts of callus (unmineralized fibrocartilage)

A

can become lined with synovium= pseudoarthrosis

147
Q

how are biologically viable nonunions further classified

A
  1. hypertrophic–enlarged bone ends, elephant foot2. slightly hypertrophic–horse hoof3. oligotrophic–no radiographic signs of callus BUT capable of growth; rounded edges and undergo decalcification(depending on how much callus is present)
148
Q

how are biologically INactive or nonviable nonunions further classified

A
  1. dystrophic–poorly vascular, callus at one end but NOT the other2. necrotic–major fragments devascularized, no callus3. defect–large bone defect4. atrophic–most extreme, defect with resorption at fracture ends
149
Q

another alternative way to classify nonunions

A

Callus: hypertrophic, slightly hypertrophicno callus: viable oligotrophic, all other nonunions

150
Q

radiographic signs of nonunion

A

persistent gapvariable amount of callus (non-bridging)rounded, sclerotic fracture endsobliteration of medullary cavitySequestraadjacent osteopeniainstability–implant loosening/bone lysis

151
Q

diagnostic modality to help ddx btwn nonviable vs viable nonunions

A

bone scintigraphy

152
Q

treatment for nonunion fractures

A

Sx intervention!remove loose implants, sequestra debride nonviable tissue (may need osteotomy–shortens leg)stabilize fracturegraft+/- culture and Ab 6-8 weeks

153
Q

common finding with femoral nonunions

A

associated with rotational instability and patellar luxation

154
Q

define malunion

A

healed fractures in which anatomical bone alignment was not achieved or maintained during healingusually ALD present with variable functional outcome(minor < 10% or 10 degrees, major > 10% or 10 degrees

155
Q

common site of malunion

A

pelvic fracturesmay lead to reduction in pelvic canal (obstipation, dystocia)

156
Q

usual cause of malunions

A

improper treatment (inadequate reduction or loss of reduction) of the original fracture in which anatomical bone alignment was not achieved.

157
Q

in immature animals, what further complicates malunions

A

growth plate fractures or damage leading to ALD

158
Q

name 7 angular deformities

A
  1. frontal plane: varus (towards medial sagittal plane), valgus (away from median sagittal plane)2. Sagittal plane: procurvatum and recurvatum3. of the axial plane: internal and external rotation4. shorteningsimple = one affected planecomplex = more than 1 affected plane
159
Q

treatment of malunions

A

corrective osteotomies if they cause a functional problem

160
Q

how do small animal patients compensate for minor ALD with minor limb shortening

A

compensate for minor shortenings by extending the joints a little more than usual

161
Q

distraction osteogenesis

A

for young dogs with ALD with limb shorteninguse circular ESF and create osteotomydistraction goal: 1 mm per day (at a rate of 3-4 times a day)

162
Q

define osteomyelitis

A

inflammatory condition of bone most commonly caused by infectious agentshematogenous or traumatic insultacute or chronic(chronic post traumatic most common)

163
Q

causative bacterial agent for osteomyelitis

A

60% staph speciesstaph intermediusgm positive fibronectin receptors used for adhesion

164
Q

T/Fopen fractures have an increased incidence of infection as bacteria have a direct opportunity to enter tissues

A

TRUE

165
Q

if normal bone is resistant to bacterial colonization and infection, when does osteomyelitis occur

A

when the vascular supply is compromised and tissue ischemia is present with bacterial contamination

166
Q

local factors involved in formation of osteomyelitis

A

tissue ischemia/impaired blood supplybacterial contaminationbone necrosis/sequestrafracture instabilityforeign material or implants

167
Q

three components to any biofilm

A

offending microbemicrobe-produced glycocalyxhost biomaterial surface

168
Q

how do biofilms help protect bacteria

A

biofilms protect bacteria from the action of Ab, impede cellular phagocytosis, inhibit Ab ingress, and alter B- and T-cell responses

169
Q

3 mechanisms of Ab resistance of bacteria with biofilm formation

A
  1. biofilm is a molecular filter2. near quiescent (dormant) growth pattern of biofilm microbes render Ab ineffective3. harsh environment (low pH, incr Co2,, decr O2, and hydration) inactivate Ab
170
Q

clinical signs associated with acute osteomyelitis

A

febrile, localized swelling and pain, systemically ill

171
Q

clinical signs associated with chronic osteomyelitis

A

localized signs, draining tracts, lameness

172
Q

how to confirm osteomyelitis

A

positive microbial testing in fracture region, sequestra, local necrotic tissue, or implantsdraining tract cultures may or may not be involved with infectious process

173
Q

treatment of acute osteomyelitis

A

draindebridesystemic Ab ( IV for first 3-5 days then oral 4-8 weeks)rigid stabilizationdirect bone culture delayed wound closure

174
Q

treatment of chronic osteomyelitis

A

meticulous debridement– need to remove biofilmestablish drainagerigid stabilization (remove old /loose implants first if needed)+/- bone graft6-8 weeks Ab

175
Q

T/Fbone will heal in the face of infection if stable

A

TRUE

176
Q

most common Ab carrier implant

A

PMMApolymethylmethacrylate

177
Q

Which one has not been reported as a risk factor for increased risk of infection TPLOs.a) increased BWb) skin staplesc) genderd) use of braided suture material e) Simultaneous bilateral procedures

A

d) use of braided suture material

178
Q

Frey et all JAVMA 2010 902 CCL Sx risks of infection/inflammation w skin staples

A

1.9x greater with staples (p=0.04).Recommendation minimum distance staples-to bone 4mm for safe application of staples.

179
Q

Gallagher 2012 vet surgeryinfection after TPLO and implant removal showed what Ab sensitivity for empirical Ab recommendations

A

94% S gentamicin (may argue local Ab beads)67% S clavamox31% S enrofloxacin

180
Q

benefits of local Ab administration for treatment of osteomyelitis

A

less systemic side effectshigh local dose (serum concentration 10-20x)prolonged dose (use of Ca sulfate beads are biodegradable over 6-8 weeks; PMMA most commonly used)USE CIDAL, water soluble AB

181
Q

major cause of implant failure

A

TECHNICAL FAILURE (improper implant size/selection/application)not infection

182
Q

methods of bone implant composite failure

A

can fail at level of implantcan fail at level of bone (bone healing)can fail at level of attachment of implant to bone

183
Q

mechanically, why does an implant bone composite fail

A

cyclic loading and fatigue(initial loads are not as important as cyclic loading)

184
Q

revisions of implant failure

A

improve mechanical and biologic environmentmay need to change all implants or augment old onesaugmentation of old implant is only considered IF alignment and reduction are maintained and failed implant will not hinder subsequent healingconsider GRAFTS

185
Q

most commonly proposed mechanical factors leading to refractor after implant removal

A

limb loaded too quicklystress protection under the area of plate, open bicortical screw holes (stress risers)***most importantremoval of implant prior to clinical union

186
Q

stress protection from bone plate application

A

rigid plate fixation has been associated with stress protection and subsequent bone lossincreased bone porosity decreased bone mineral density

187
Q

screw holes act as stress risers have their greatest effect in what force

A

screw holes have their greatest effect in torsion

188
Q

implant material of choice

A

METAL (SS or titanium)high strength and stiffnessgood ductilitybiologically well tolerated

189
Q

define stiffness

A

depends on the material, design and dimension of implantaka modulus of elasticityslope of a load vs deformation curveosteosynthesis restores bone stiffness temporarily while fracture healing restore bone stiffness permanently

190
Q

stiffness or modulus of elasticity of titanium vs stainless steel

A

stiffness of titanium (110 GPa) is half that of stainless steel (200 GPa)in other words, titanium plate would deform nearly twice as much as a steel plate

191
Q

T/FLess stiff implants abolish stress shielding

A

FALSEless stiff implants REDUCE but do not abolish stress shielding

192
Q

define strength

A

ultimate stress limit that material/structure can withstand without deformation/rupturestrength determines the level of load up to which the implant remains intact

193
Q

compare strength of commercially pure Ti, to stainless steel

A

ultimate tensile strengthCP Ti 860 MPa (10% less than SS)SS 960 MPa

194
Q

T/F In internal fixation, the resistance to repeated load, which by result in fatigue failure is more important than strength

A

TRUE

195
Q

define ductility

A

implant material characteristic that characterizes the degree of plastic deformation it tolerates before rupturehelps determine the ease of contouring

196
Q

titanium vs ss ductility

A

titaniums offer less ductility than stainless steel

197
Q

define corrosion resistance

A

determines how much metal is released into the surrounding tissue

198
Q

stainless steel vs Ti corrosion resistance

A

SS is highly corrosive resistant though “fretting” local corrosion can occur (screw head moving in relation to plate hole)CP ti shows nearly NO corrosion making it a better biologic material

199
Q

allergic reactions to metal

A

nickel containing SS 1-2 %no reaction with titaniumVery little data

200
Q

disadvantage of biodegradable implants

A

they have limited mechanical properties and therefor should only be used in areas of minor loading

201
Q

methods for filling bone defects

A
  1. autocortico, cancellous, or corticocancellous grafts2. allograft3. Distraction osteogenesis4. deproteinized bone (kiel bone)5. synthetic bone fillers (HA, tricalcium phosphate)
202
Q

T/FVery high levels of strain can be present within small fracture gaps

A

TRUEVery high levels of strain can be present within small fracture gaps even under conditions where the displacement may not be perceptible

AO (1 decks)

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