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Flashcards in AO_chapters Deck (202):

preop management of fx patient

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


benefits to pain mgmt for fx patient

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


most effective analgesic time period

PRIOR to onset of pain (surgery)


advantages of multimodal pain therapy

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


define neuroleptanalgesia

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


infection rate of CLEAN ortho procedures



most common isolate causing ortho infxn

Staph intermedius


host risk factors for sx infection

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


intraop risk factors for sx infection

sx > 90 mexcessive electrocauterybreak in asepsisbraided/multifilament sutureimplants


use of periop prophy Ab decreases rate of infxn_______

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


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


AO fracture classification

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


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


physeal fracture classification

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


objectives for fracture repair

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


mechanical and biological factors for fractures

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


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


Three ways of fracture planning

direct overlaybone specimenintact contralateral bone


major benefit of fully reconstructed boney column

shares the wt bearing load of the limb during fx healing


review of post op radiograph criteria

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


rehabilitation goals

prevents musculoskeletal disabilitydecreases healing timefacilitates restoration of normal function


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


types of massage

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


biological fracture healing goals

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


role of screw

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


difference btwn cancellous and cortical screws

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


cortical screw

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


3.5 mm cortical screw characteristics

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


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


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


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


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


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


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

shear forces displace fracture fragments


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

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


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


functions of a dynamic compression plate

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


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)


oval shape of DCP holes allows what degree of screw angulation

25 degrees longitudinally7 degrees transversally


gold eccentric drill guide is how far off center

1.0 mm (therefore allows for compression)


available metal for LCDCP vs DCP

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


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


symmetrical shape of LCDCP holes allows what degree of screw angulation

40 degrees longitudinally7 degrees transversally


what drill guide is used in LCDCP

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


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


reconstruction plate use

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


types of special veterinary plates

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


compression vs neutralization plate functions

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


prebending plate functions to...

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


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


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


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


LCP locking compression plate

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


locking head screw (LHS)

self tappingconical threaded head and threads/locks into plate


unilock plate system

2.0 mm or 2.7 mm systemslocking plate/screw design


CRIF Clamp rod internal fixator system

excellent versatilitygood contouring capabilityease of applicationminimal instrumentationminimal contact with bone


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


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


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


types of ESF connecting bars

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


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


advantages of ESF application

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


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


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)


angled vs parallel pins in ESF

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


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


ILN interlocking nail

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


standard ILN has bolts how far apart

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


bolts used with ILN

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


what mode are ILN placed?

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


ILN can only be passed (normo or retrograde)

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


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


how to remove ILN

first remove screws/boltsattach extension setextract nail


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


most common point style for IM pin

Bayonet3-face trocarDiamond point


difference between steinmann pin and k-wire

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


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

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


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.


repair of distal physeal fractures and pins

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


recommended IM pin diameter when using plater rod

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


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


ideal fracture configuration for using orthopedic cerclage wire

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


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


forces that cerclage wire may counteract

axial compression some rotation


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


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)


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


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)


repair of avulsion fractures

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


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


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


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)


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)


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


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%


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


source of blood supply in initial healing phases

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


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


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


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

collagen fibers resist elongation up to a max 17%


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


tissue types included in the repair phase of secondary bone healing

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


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

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


ultimate tensile strength of compact bone

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


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



remodeling phase in bone healing

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


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)


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


unreamed vs reamed ILN affect on blood flow

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


biological fixation of comminuted fractures is associated with...

incr callusaccelerated radiographic unionearlier gain in strengthearly return to normal function


Primary or direct bone healing

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


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


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


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


daily progress of of cutting cones across a fracture site

50-100 micrometers/day


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


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)


goals of biological fracture fixation

restore length, alignmentlimit manipulation and disruption of ST, hematoma


perferred techniques for stabilization with biological fracture fixation



considerations for what adjunct therapy to promote biologic osteosynthesis

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


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


Properties of demineralized bone matrix

most commonosteoinductive, osteoconductivechemical sterilization


rank the areas for greatest autogenous cancellous bone collection

ilium > prox humerus > medial proximal tibia


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

12 weeks for femoral or humeral site


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


only osteoconductive implants with biomechanics properties

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


main complication with allogenic bone segment

incomplete resorption-->fatigue failureinfection


osteoconductive calcium sulfate

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


Bioceramic osteoconductive examples

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


periosteal stripping in immature animals

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


three factors that affect the size of bone callus

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


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


4 A's of radiographic assessment of bone healing



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



indications for plate removal

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


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


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


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


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


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

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


T/Fstability = rigidity

FALSE Stability should NOT be confused with rigidityex. circular ESF


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


define nonunion

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


classifications of nonunions

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


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)


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

can become lined with synovium= pseudoarthrosis


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)


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


another alternative way to classify nonunions

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


radiographic signs of nonunion

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


diagnostic modality to help ddx btwn nonviable vs viable nonunions

bone scintigraphy


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


common finding with femoral nonunions

associated with rotational instability and patellar luxation


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


common site of malunion

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


usual cause of malunions

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


in immature animals, what further complicates malunions

growth plate fractures or damage leading to ALD


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


treatment of malunions

corrective osteotomies if they cause a functional problem


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


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)


define osteomyelitis

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


causative bacterial agent for osteomyelitis

60% staph speciesstaph intermediusgm positive fibronectin receptors used for adhesion


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



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


local factors involved in formation of osteomyelitis

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


three components to any biofilm

offending microbemicrobe-produced glycocalyxhost biomaterial surface


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


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


clinical signs associated with acute osteomyelitis

febrile, localized swelling and pain, systemically ill


clinical signs associated with chronic osteomyelitis

localized signs, draining tracts, lameness


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


treatment of acute osteomyelitis

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


treatment of chronic osteomyelitis

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


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



most common Ab carrier implant



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


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.


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


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


major cause of implant failure

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


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


mechanically, why does an implant bone composite fail

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


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


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


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


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

screw holes have their greatest effect in torsion


implant material of choice

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


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


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


T/FLess stiff implants abolish stress shielding

FALSEless stiff implants REDUCE but do not abolish stress shielding


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


compare strength of commercially pure Ti, to stainless steel

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


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



define ductility

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


titanium vs ss ductility

titaniums offer less ductility than stainless steel


define corrosion resistance

determines how much metal is released into the surrounding tissue


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


allergic reactions to metal

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


disadvantage of biodegradable implants

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


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)


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