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Flashcards in AO_chapters Deck (202):
1

preop management of fx patient

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

2

benefits to pain mgmt for fx patient

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

3

most effective analgesic time period

PRIOR to onset of pain (surgery)

4

advantages of multimodal pain therapy

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

5

define neuroleptanalgesia

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

6

infection rate of CLEAN ortho procedures

2.5-4.8%

7

most common isolate causing ortho infxn

Staph intermedius

8

host risk factors for sx infection

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

9

intraop risk factors for sx infection

sx > 90 mexcessive electrocauterybreak in asepsisbraided/multifilament sutureimplants

10

use of periop prophy Ab decreases rate of infxn_______

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

11

traditional recommendation for prophy Ab in clean procedure

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

12

AO fracture classification

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

13

open fracture classification

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

14

physeal fracture classification

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

15

objectives for fracture repair

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

16

mechanical and biological factors for fractures

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

17

pros/cons to open vs closed reduction of fx

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

18

Three ways of fracture planning

direct overlaybone specimenintact contralateral bone

19

major benefit of fully reconstructed boney column

shares the wt bearing load of the limb during fx healing

20

review of post op radiograph criteria

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

21

rehabilitation goals

prevents musculoskeletal disabilitydecreases healing timefacilitates restoration of normal function

22

rehab includes

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

23

types of massage

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

24

biological fracture healing goals

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

25

role of screw

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

26

difference btwn cancellous and cortical screws

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

27

cortical screw

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

28

3.5 mm cortical screw characteristics

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

29

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

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

30

what is a shaft screw

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

31

what is a cannulated screw

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

32

application of a lag screw

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

33

Lag screw insertion guidelines

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

34

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

shear forces displace fracture fragments

35

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

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

36

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

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

37

functions of a dynamic compression plate

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

38

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

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)

39

oval shape of DCP holes allows what degree of screw angulation

25 degrees longitudinally7 degrees transversally

40

gold eccentric drill guide is how far off center

1.0 mm (therefore allows for compression)

41

available metal for LCDCP vs DCP

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

42

limited contact dynamic compression plate (LC DCP) advantages

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

43

symmetrical shape of LCDCP holes allows what degree of screw angulation

40 degrees longitudinally7 degrees transversally

44

what drill guide is used in LCDCP

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

45

Veterinary cuttable plates use

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

46

reconstruction plate use

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

47

types of special veterinary plates

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

48

compression vs neutralization plate functions

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

49

prebending plate functions to...

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

50

Buttress vs bridging plate functions

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

51

implant combo particularly effective for bridging application

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

52

advantages of locking plate/screw systems

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

53

LCP locking compression plate

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

54

locking head screw (LHS)

self tappingconical threaded head and threads/locks into plate

55

unilock plate system

2.0 mm or 2.7 mm systemslocking plate/screw design

56

CRIF Clamp rod internal fixator system

excellent versatilitygood contouring capabilityease of applicationminimal instrumentationminimal contact with bone

57

contouring of plates rules of thumb

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

58

pros to positive profile pins

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

59

T/F double clamps are as strong as single clamps

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

60

types of ESF connecting bars

Stainless steel (historically)Carbon fiber--radiolucentTitaniumAcrylic/epoxy

61

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

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

62

advantages of ESF application

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

63

Rules of thumb w ESF fixation

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

64

T/F Bilateral ESF are more stable than unilateral ESF

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)

65

angled vs parallel pins in ESF

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

66

ESF clamp placement

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

67

ILN interlocking nail

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

68

standard ILN has bolts how far apart

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

69

bolts used with ILN

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

70

what mode are ILN placed?

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

71

ILN can only be passed (normo or retrograde)

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

72

ILN lock which side (prix or distal) fragment first

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

73

how to remove ILN

first remove screws/boltsattach extension setextract nail

74

IM pin alone recommended diameter and counteracting forces

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

75

most common point style for IM pin

Bayonet3-face trocarDiamond point

76

difference between steinmann pin and k-wire

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

77

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

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

78

how to add bending strength to IM pins

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

79

repair of distal physeal fractures and pins

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

80

recommended IM pin diameter when using plater rod

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

81

orthopedic wire material

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

ideal fracture configuration for using orthopedic cerclage wire

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

83

how many cerclage wire is recommended per fracture fragment

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

forces that cerclage wire may counteract

axial compression some rotation

85

three methods of tying cerclage wire

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

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

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

with loop cerclage how much wire remains when cutting wire off

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

88

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

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

repair of avulsion fractures

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

90

pin and tension band technique for avulsion fx repair

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

where to drill the hole to pass a tension band

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

92

three phases of bone healing

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

the amount of callus produced in healing depends on what...

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

94

define strain

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

bone formation and strain

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

source of growth factors in inflammatory phase

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

source of blood supply in initial healing phases

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

98

what does resorption of fracture ends do for inter fragmentary strain

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

99

repair phase characterized by what cell type and tissue

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

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

collagen fibers resist elongation up to a max 17%

101

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

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

102

tissue types included in the repair phase of secondary bone healing

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

103

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

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

104

ultimate tensile strength of compact bone

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

105

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

true

106

remodeling phase in bone healing

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

107

define pizoelectricity

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

108

what do medullary implants do to bone blood flow

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

109

unreamed vs reamed ILN affect on blood flow

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

110

biological fixation of comminuted fractures is associated with...

incr callusaccelerated radiographic unionearlier gain in strengthearly return to normal function

111

Primary or direct bone healing

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

112

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

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

113

contact healing of primary bone healing occurs when?

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

114

define cutting cone

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

daily progress of of cutting cones across a fracture site

50-100 micrometers/day

116

difference btwn contact and gap healing of primary bone healing differ

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

define gap healing

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

goals of biological fracture fixation

restore length, alignmentlimit manipulation and disruption of ST, hematoma

119

perferred techniques for stabilization with biological fracture fixation

ESFILNMIPO

120

considerations for what adjunct therapy to promote biologic osteosynthesis

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

121

properties of bone grafts

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

Properties of demineralized bone matrix

most commonosteoinductive, osteoconductivechemical sterilization

123

rank the areas for greatest autogenous cancellous bone collection

ilium > prox humerus > medial proximal tibia

124

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

12 weeks for femoral or humeral site

125

cell viability for fresh cancellous autograft

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

126

only osteoconductive implants with biomechanics properties

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

127

main complication with allogenic bone segment

incomplete resorption-->fatigue failureinfection

128

osteoconductive calcium sulfate

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

129

Bioceramic osteoconductive examples

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

130

periosteal stripping in immature animals

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

131

three factors that affect the size of bone callus

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

132

radiographic signs of indirect bone healing

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

4 A's of radiographic assessment of bone healing

alignmentappositionapparatus/implantsactivity/healing

134

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

TRUE

135

indications for plate removal

1. osteomyelitis2. pain on palpation of bone3. radiographic evidence osteopenia

136

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

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

137

define a delayed union

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

Causes of delayed union

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

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

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

140

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

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

141

T/Fstability = rigidity

FALSE Stability should NOT be confused with rigidityex. circular ESF

142

treatment of delayed union

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

define nonunion

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

144

classifications of nonunions

1. viable/biologically active--variable amounts of callus but failed bridging2. nonviable/biologically inactive--no callus

145

Causes of nonunion

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

146

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

can become lined with synovium= pseudoarthrosis

147

how are biologically viable nonunions further classified

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

how are biologically INactive or nonviable nonunions further classified

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

another alternative way to classify nonunions

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

150

radiographic signs of nonunion

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

151

diagnostic modality to help ddx btwn nonviable vs viable nonunions

bone scintigraphy

152

treatment for nonunion fractures

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

153

common finding with femoral nonunions

associated with rotational instability and patellar luxation

154

define malunion

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

common site of malunion

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

156

usual cause of malunions

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

157

in immature animals, what further complicates malunions

growth plate fractures or damage leading to ALD

158

name 7 angular deformities

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

treatment of malunions

corrective osteotomies if they cause a functional problem

160

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

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

161

distraction osteogenesis

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

define osteomyelitis

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

163

causative bacterial agent for osteomyelitis

60% staph speciesstaph intermediusgm positive fibronectin receptors used for adhesion

164

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

TRUE

165

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

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

166

local factors involved in formation of osteomyelitis

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

167

three components to any biofilm

offending microbemicrobe-produced glycocalyxhost biomaterial surface

168

how do biofilms help protect bacteria

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

169

3 mechanisms of Ab resistance of bacteria with biofilm formation

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

clinical signs associated with acute osteomyelitis

febrile, localized swelling and pain, systemically ill

171

clinical signs associated with chronic osteomyelitis

localized signs, draining tracts, lameness

172

how to confirm osteomyelitis

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

173

treatment of acute osteomyelitis

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

174

treatment of chronic osteomyelitis

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

175

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

TRUE

176

most common Ab carrier implant

PMMApolymethylmethacrylate

177

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

d) use of braided suture material

178

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

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

179

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

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

180

benefits of local Ab administration for treatment of osteomyelitis

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

major cause of implant failure

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

182

methods of bone implant composite failure

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

183

mechanically, why does an implant bone composite fail

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

184

revisions of implant failure

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

most commonly proposed mechanical factors leading to refractor after implant removal

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

stress protection from bone plate application

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

187

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

screw holes have their greatest effect in torsion

188

implant material of choice

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

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define stiffness

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

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stiffness or modulus of elasticity of titanium vs stainless steel

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

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T/FLess stiff implants abolish stress shielding

FALSEless stiff implants REDUCE but do not abolish stress shielding

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define strength

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

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compare strength of commercially pure Ti, to stainless steel

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

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

TRUE

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define ductility

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

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titanium vs ss ductility

titaniums offer less ductility than stainless steel

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define corrosion resistance

determines how much metal is released into the surrounding tissue

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stainless steel vs Ti corrosion resistance

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

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allergic reactions to metal

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

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disadvantage of biodegradable implants

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

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methods for filling bone defects

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

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

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