Midterm Flashcards
(183 cards)
1
Q
Bone strength factors
A
Material, structural, rate of load, orientation of load
2
Q
Rate of load applied=
A
Viscoelastic properties
3
Q
Direction of load=
A
anisotropic (identical properties in all directions?)
4
Q
Heirarchy of strength in response to forces
A
Compression > tension > shear
5
Q
Name Fx mechanisms
A
Tension, compression, torsion, shear, bending
6
Q
Compression: aka, type of Fx, where
A
Axial load; short oblique; vertebral bodies.
7
Q
Tension causes what type of Fx and where
A
Avulsion at apophyses (traction physes- lig/tend attchmt)
8
Q
Shear- type of Fx
A
SH4
9
Q
Bending- type of Fx
A
transverse or short oblique starting on tension surface (+/- Y with butterfly segment)
10
Q
Torsion- Fx type
A
Spiral
11
Q
Configuration of Fx classification
A
Incomplete (greenstick vs fissure), complete (transverse, oblique, spiral, comminuted, segmental)
12
Q
Greenstick Fx- describe, produced by, Fx types
A
by bending/torsion, still weight bearing- both cortices involved- oblique/spiral
13
Q
Transverse Fx- force type
A
Bending
14
Q
Transverse- reduction withstands what forces
A
axial/compression
15
Q
Oblique vs spiral
A
Oblique: cortices on same plane
16
Q
Oblique- causes
A
compression and bending together
17
Q
Comminution- define
A
three segments with connected Fx lines, multiple forces, higher energy trauma
18
Q
Segmental- define
A
Three pieces but no interconnection- intact cylinder between fxs, +/- avascular segment from disrupted medullary vascular supply
19
Q
Open Fx classifications
A
I- clean, laceration 1cm
III- extensive damage, worse prognosis, wont ever be perfect
20
Q
Type of bone in diaphysis, healing speed
A
Mainly cortical, haversian system (mostly mineral, some osteoblasts) slow turnover/healing
21
Q
Type of bone in metaphysis, healing speed
A
cancellous with mantle of cortex, muscle attachments, less mechanical forces applied, good blood supply, fast turnover
22
Q
Long term effect of SH fx
A
physeal fracture- impeded growth, poor long term fxn
23
Q
When joint involved in a fracture, treatment MUST have
A
Anatomic reduction and rigid fixation!
24
Q
SH scheme
A
SALTR - straight (physis), above (thru meta/phys), lower (thr phys/epi, through (epi/meta/phys), compressive cRush
25
Effect of all SH fx on all dogs and cats
growth plate closes
26
Where do SH fx occur? (Boards)
Zone of hypertrophy (where cells get large before mineralizing)`
27
Describe Fx
open/closed, configuration, location, R/L, bone, displacement
28
Describe displacement of fx
Distal to prox
29
Fracture assessment score
Fx, owner, patient- high (10) good- less plates, fast heal; low (1) slow heal, need plates
30
Primary goal of fracture management
Early and complete return to fxn (small incisions, anatomic reduction, rigid fixation, direct bone healing, good rads)
31
Outcomes of anatomic reduction
Load sharing, weight bearing, fracture healing, alignment
32
Biologic fixation- describe
The gardener approach, preserve environment, use bridging osteosynthesis- align ends of bones in functional position, let nature heal
33
What has greatest impact on limb function
alignment >reduction
34
Define fixation
implant physically engaging bone
35
Define stabilization
dont touch bone- cast/splint
36
What does union depend on in bone healing
Mechanical and biologic env- haversian systems laid down along lines of stress
37
Secondary healing- define
Body's natural healing, inflammatory--> reparative --> remodeling
38
Define reparative phase
extra/periosseous blod supplu revascularizes, bringing fibrous tissue for support (-->fibrocart --> cart -->woven)
39
Describe remodeling phase
Woven to lamellar bone
40
Primary healing- define, requirements
Sx intervention with plates/screws (not ExFix), anatomic reduction and rigid stabilization (minimal callus formation)
41
Two forms of primary healing
Contact (direct apposition. MNGC osteoclast chewing, osteoblast laying haversian) or gap healing (
42
Difference between primary healing types
Contact- endochondral ossification; Gap- woven bone (no fibrous/cartilage- just bone)
43
Faster healing: meta or diaph? why?
Meta- less bending, more blood, cancellous
44
When will callus be evident on rads
2-4 weeks (young faster than old)
45
Segment vs fragment
seg- big pieces at end; frag- little pieces in middle
46
Primary site of bone graft- dog/cat
Greater tubercle of humerus (also use iliac crest, prox tibia) (diaphysis is yella marrra)
47
Indications for graft
Enhance unions, replace bone loss, stimulate fusion in arthrodesis
48
Dog/cat histo graft type
Cancellous (vs cortical, corticocancellous)
49
Osteogenesis- def, histo type
Direct placement of osteoblasts (and osteoprogenitors) from cancellous
50
Osteoinduction- def, histo type
Causing mesenchymal cells to differentiate into osteoblasts via cytokines like BMP (corticocancellous)
51
Osteoconduction- def
Trabeculae of bone transfered to act as scaffold for capillaries and incoming osteoblasts, evenutally resorbed
52
Structural support- graft type, describe
Cortical only- usually allograft; never complete remodel- creeping substitution
53
Define "coapt"
To approximate
54
Toggling- define, goal
leverage pieces against each other, 50-100% apposition and functional alignment
55
What forces does coaption reduce best
Bending
56
Copation indications
Temp immob, young fx, distal fx, simple/stable fx, lig/tend inj
57
Effect of coaption post surgery
No increased stability, higher risk of fracture disease
58
Cardinal rule of coaption
Immob prox and distal joints
59
Schanz bandage
Soft, padded, like MRJB
60
What position must p be in for lateral coaption splints
Functional standing- not extension
61
Spica- describe
Splint or cast (hard material), goes proximally over midline then wrapped around body
62
Spica indications
Proximal to elbow
63
RJB- indications, rule of thumb
distal to humeral and femoral condyles; 1 lb cotton/20lb dog
64
RJB- fxn
Decrease swelling, prevent closed going to opened
65
Mason-meta- describe
Spoon splint
66
Mason meta- indications
distal to carpus or tarsus/hock
67
Mason-meta- dont use on what?
Radius/ulna fx- cant immobilize prox joint
68
Velpeau sling- describe
hold forelimb against body, non=weight bearing
69
Velpeau sling- indication
Shoulder injuries
70
Figure of 8- bandage with similar effects
Ehmer sling
71
Figure of 8 and Ehmer function, differences
Non-weight bearing, Prevent abduction, flex hip, internally rotate- Ehmer comes around waist
72
What do Ehmer bandages prevent
Quadriceps tie down- stifle lock from quad fibrosis due to hyperextension- young cats/dogs
73
ExFix best for- Fx type
Comminuted, open, infected, non-union, arthodeses
74
What function does ExFix provide to fx
Stable, but NOT rigid fixation
75
ExFix- forces counteracted
Compression, bending, rotational
76
ExFix- advantages
Open or closed application, stable, post-op adjustments, early weight bearing mitigating fracture dz, economical
77
Types of Ex Fix
I- half pin splintage, uniplanar, unilateral; II- full pin splintage- uniplanar, bilateral (through two skin); III- biplanar, bilateral half and full splintage
78
Which type of exfix cant be used above elbow/stifle
Type II (and type iii)
79
Most used ExFix types in gen prac
Linear
80
What is the weakest link in the exFix
Bone-pin interface
81
Maleffects of smooth pins- exfix
loose so caused periosteal rxn and resorption, had to angle for surface area
82
Threaded pins in exfix, describe
Positive profile- threaded above core diameter, harder to extract- faster healing
83
Type of drill, ExFix
low speed, high torque
84
Pin stiffness in ExFix
Inversely proportional to distance between cis and clamp^3
85
Pins per segment
3-4 per major segment
86
Fixation pin diameter rules
no more than 30% diameter of bone
87
KE vs SK
KE- no threaded pins, one diameter, cant add/subtract clamps, not radiolucent, rod weaker; SK- PPP, allows pre-drilling, bigger/stronger connecting rod, more stability
88
Bone healing in SK system
Secondary! NOT rigid - only plates and screws give primary
89
Most common form of intFix in gen prac, goal
IM fixation- three point fixation
90
IM implants (and describe)
Steinmann (large diameter, less bend), kirschner wire (smallest diameter steinmann, flex), in the manner of Rush, interlocking nails
91
Three point fixation- points
1) prox epi/meta cancellous 2) endosteal diaph 3) distal epi/meta cancellous
92
IM resistance to bend
Proportional to diameter^4th
93
IM points
Trochar (three sided, sharp); threaded (bounce off), chisel (spaded- trocar goes through bone better!)
94
IM approaches
Normograde (in end of bone, across fx, into far segment); Retrograde (in fx site, drive prox, then back down to distal)
95
Easiest to retrieve end of bone config
Tied in (pin through skin, tied to exFix) (vs end cut flush, end cut and countersunk)
96
Which type of pin are used in the manner of Rush in IM
K wires with chisel tip to deflect
97
K wire positioning
Less than 15 degrees or less than parallel with medullary cavity
98
Describe Rush manner
Into cavity, against endosteal cortex, providing dynamic flexion with three point fixation
99
What IM technique is used in SH fractures
Dynamic pinning- in the manner of Rush, cross proximal to Fx line
100
Interlocking nails prevent what , due to
Bending, rotational, axial forces due to screw prox and dist to fx line
101
Femur- preferred IM approach
USUALLY Normo with over=reduction for better distal positioning
102
Tibia- preferred IM approach
MUST be normo (retro comes out in stifle)
103
Radius- preferred IM approach
JUST SAY NO (stress pinning of physeal ok)
104
Ulna- preferred IM approach
either
105
Humerus
Retro>normo, easier
106
Requirements for circlage 10 command
Perfect 360 reduction/reconstruction; oblique fx 2-2.5x diameter of bone at Fx level, wire sufficient diameter, more than 1 wire, approp distance (1/5), no soft tissue inside (wire contact bone), perp to long axis (except K), must be tight, prevent slip with hemi or K
107
Function of cerclage
fragment apposition, not enough stability alone for weight bearing- Always used with plate, pin or exFix
108
Cerclage forces resisted
dependent on friction of interdigitation
109
Cerclage wire placement
1cm apart, 5mm from end of segments, evenly spaced
110
Cerclage- prevent slip at diameter change
Hemi-cerclage (thread through hole in bone); K wire perpendicular to fx, cerclage prox and distal to K wire protrusions
111
Twist knot- adv/disadv
More resistant to distractive forces, simpler, retighten, cheaper; not as tense as loop, twist protrudes into soft tissue
112
Loop knot- adv/disadv
Tighter, less trauma from loop, perp to long axis of bone; Less resistant to distractive forces, can't re-tighten, more $
113
Biomechanics of loops and twists- 4 studies
Loop greater tension before and after bend; twist lose tension when bent; twist greater distractive resistance, resistance to dist. forces increase with greater wire diameter
114
Pin and tension band best for
Apophyseal protuberances
115
Pin and tension band function
Turn tension forces to compressive in osteotomy
116
Equine limb toe up
P3 (coffin) P2 (pastern) P1 (MCP/fetlock) MC3 (carpus/tarsus-hock) R/U (elbow) Humerus
117
Primary goal of eq fx
Stabilize limb for transport
118
Eq- sedation, avoid
Xylazine or detomidine +/- torb (avoid ataxia and acepromzine for a1 antag)
119
Eq- Section 1 goal
Immob fetlock, align dorsal cortices
120
Eq- Sec 2 goal
Immob distal to Fx
121
Eq- Sec 3 goal
Prevent abd
122
Eq- Sec 4 goal
Carpal extension
123
Eq- Section 1 bandage and splint
thin nonRJB, dorsal/plantar
124
Eq- Sec 2 bandage and splint
Thick RJB, Ca/lat (calc to ground)
125
Eq- Sec 3 bandage and splint
Thick RJB, Ca/lat (elbow/withers or tub cox to ground with wide board)
126
Eq- Sec 4 bandage and splint
Thin nonRJB, Ca gr to elb; none on hind limb
127
Eq- Best NSAID for MSkel
Phenybutazone
128
Eq- transport
Gooseneck or large van - no box or stock
129
Eq- hindlimb fx face
Front
130
Eq- forelimb fx face
Back
131
Eq- Fx Px
type, number, location, open/closed, soft tissue/vasc injury, age/breed/weight/nature, time between injury and intervention, first aid efficacy
132
Biggest factor for horse prognosis
Type and location
133
Stall rest indications
non displaced/incomplete stress fx, MC/T 2/4, patella, pelvis
134
Thomas Schroeder bandage
cast with donut ring- used as a crutch to stabilize
135
Eq- exFix indication
Distal limb only (fetlock down)
136
Describe transfixation-pin casts
Spiral around eq leg to dec rotational stress and give axial suppt., 2-3 cross pins prox to Fx in cast to the ground
137
transfixation-pin casts indications
distal limb
138
EFSD- describe
U shaped transosseus exFix for distal comminuted
139
Adv/disadv of eq exFix
Immediate weight bearing, wound/open fx access; only under 90kg or non-weight bearing
140
4 Principles of Eq intFix
rigid stabilization, anatomic reduction, preserve blood supply, early mobilization (Via screws and plates)
141
Eq- cortical screws, most common size
Thick with thin thread = strong, rigid; as position, implant, lag fashion; 4.5
142
Eq- cancellous screw
Thin diameter with thick thread, replace stripped cortical
143
Eq screw in lag fashion- order
drill (glide) drill (thread) countersink, measure, tap, screw
144
Eq drill specs
1mm/sec with saline flush to prevent swath overheating/necrosis of bone
145
Tapping
Creates threaded holes in drilled holes
146
Plate fixation- eq minimums
4 screws per side of Fx
147
Eq- DCP- features
Slanted holes, interfrag compression, neutral or compression positions
148
Eq- LC-DCP- features
same as DCP with scallops and sturdier due to even distribution of mass
149
Eq- LCP features
more rigid, bigger core, smaller threads, perpendicular only needed, LCP or cortical screws both work, less bone-plate contact bc heads of screws lock in plate= rigid fixation
150
Eq fx complications
infection, breakdown, osteoarthritis, angular limb deformity, supporting limb laminitis (life threatening)
151
Princ of intFix
Anatomic reduction, stable int fixation, atrauma, early return to fxn
152
IntFix screws
self tap- big core, sturdy, creates groove; cancelous- less study but better in cancellous
153
Locking screws (strength vs cortical)
diam bigger, so stronger
154
Screw function classification (3)
Implant, lag, position
155
Implant screw
Most common fxn, hold plate to bone, both cortices preferred
156
lag screw indications
very oblique fx
157
position screw
holds in place, no compression, both cortices
158
Plate classification by function (3)
Compression, neutralization, buttress (bridging)
159
Compression plate- indication, function, goal
transverse and short oblique; reduce and compress, primary healing
160
Neutralization plate- indication, function
comminuted, no compression
161
Buttress plate - indication, function
not reconstructing the column, bridges fx gap and takes on entire load
162
What plate is the internal external fixator
Locking plates
163
Minimum cortices in SA plates
4, 6 preferred (3 bicortical or 4 uni+2bi)
164
Fx fixation specs
Screws 4-5mm from fx line
165
What fx should not get RJB in SA
femoral and hmeral- fulcrum creation, vessel/tissue tears
166
When fx takes longer to heal than expected; main causes
Delayed union (>3-4m); bio and mechanical
167
Bio causes of delayed union
poor blood, infxn, systemic dz, drugs
168
Mechanical causes of delayed union
inadequate fx fixation causing motion and no callus maturation, poor reduction, excessive post op activity
169
Dx delayed union-
Rads- distinct fx margins (not rounded), arrest/regression of healing from serial rads
170
Tx delayed union
Autograft of cancellous, vascularized graft, bone forage, remove implants
171
Two types of non-union
Viable and non
172
Dx non-union
palpable instability, mm atrophy, limb deformity
173
Viable non-unions
hypertrophic callus (lots of blood supply but no healing in middle); slightly hypertrophic, oligitrophic (no callus)
174
Non-viable unions
dystrophic, necrotic, defect non-union, atrophic non-union
175
Tx non-union
Just like delayed- Sx- debride, open med canal, rigid fixation, autograft, tx according to type
176
What type of plate is best for ulna
NONE- too small
177
Types of mal-union; causes
fxn and non-fxn'l; GP injury, non-anatomic position, poor reduc/stab
178
Tx mal-union
Corrective osteotomy- realign, rigid rfix
179
Most common dog infection of implant
Staph
180
Rad findings in osteomyelitis
Long zone of transition, swelling, sequsterum, avascular/nonviable, involucrum, cloaca
181
Involucrum
(periosteal rxn around sequestrum, forms membrane
182
Bandages- change q?
5-7 (can stretch 10 with good compliance)
183
Prophylactic Abx- schedule
Cefazolon 30-60 min pre-sx; q 1.5-3 h; no more than 24 unless contaminated
