Ortho Hindlimb Flashcards
How many tarsal bones are there? List them
7
- calcaneus
- talus (tibiotarsal bone)
- central tarsal bone
- 1st, 2nd, 3rd, 4th tarsal bones
What are the parts of the talus?
- Body with 2 ridges to form trochlea
- Head articulates with central tarsal bone (distal portion)
What are the parts of the calcaneus?
- tuber calcanei - connects with cancaneal tendon
- sustentaculum tali - medial side
What are the articulations of the tarsus and what do they connect?
- tarsocrural – talus to tibia
- talocalcaneal – talus to sustentaculum tali
- talocalcaneal central – talus/sustentaculum tali to central tarsal
- calcaneoquartal – calcaneus to 4th tarsal bone
- centrodistal (aka inter tarsal) – central tarsal to T1-3
- tarsometatarsal (aka proximal inter tarsal) – tarsal bones to metatarsals
What additional sesamoid bones are present in the Greyhound breed?
- Lateral plantar tarsometatarsal 50%
- small medial inter tarsal tarsometatarsal 27%
Normal standing angle of tarsus in dog vs. cat
Dog = 135 - 145 degrees
Cat = 115 - 125 degrees
What is the range of motion of the tarsus in dog vs cat
Dog = 39 deg flexion, 164 deg extension
Cat = 22 deg flexion, 167 deg extension
What is the prognosis of fracture of talus?
Guarded d/t severe OA
What are 4 fracture patterns of calcaneus?
- Midbody (comminution)
- Slab fractures (dorsomedially or laterally)
- Avulsion involving plantar ligaments
- SH I - avulsion of proximal epiphysis
Prognosis for calcaneal fracture repair?
Good.
Greyhounds good for function, poor for return to racing
What stance may be seen with fracture of calcaneus?
Pseudo-plantigrade stance
What breed commonly gets central tarsal bone fractures?
Greyhounds. RIGHT side
accounts for 79% of tarsal injuries
List 5 patterns of central tarsal bone fracture
- Non-displaced dorsal slab
- Displaced dorsal slab
- Large displaced medial slab
- Medial slab with dorsal slab
- Comminuted
List treatment and prognosis for central tarsal bone fractures
- extension splint to prevent collapse
- screws in lag fashion optimum for types I-IV
- can do conservative for I-II
- arthrodesis?
- Prognosis can be good with successful surgery
What are treatment options for tarsal collateral ligament rupture? Prognosis?
Prognosis for short collateral rupture?
- primary repair with locking loop +/- internal splint (bone anchors, screws and washers, nylon, monofilament wire)
- transosseous tunnels to place suture w/o metal
- Prognosis - fair to guarded if medial and lateral instability
- Short collateral - good
What tendons make up the calcaneal tendon?
- Paired gastrocnemius
- Gracilis
- Semitendinosus
- Biceps femoris
- Superficial digital flexor
What are the 2 most common disruptions of the calcaneal tendon?
Of the latter, what breeds are over represented?
- Traumatic complete tear
- Partial separation of the gastrocnemius
- Labradors, Doberman Pinscher
With disruptions of the gastrocnemius insertion, why do you see knuckling in stance?
stretching of the SDFT over the calcanei from hyper flexion of tarsocrural joint
What signalment for cats have partial disruption of calcaneal tendon?
What is the prognosis?
- cats >5 years
- females outnumbering males 6:1
- Prognosis = good to excellent; cats success rate 84% (72-94%)
What are the breeds seen with luxation of the tendon of SDFT?
Which direction does it go?
What is the treatment?
- Shetland Sheepdogs, collies, Greyhounds
- LATERAL
- desmotomy on side of luxation, repair damaged retaining tissue with 8-10 simple interrupted non-absorbable suture
- immobilize 4 weeks
For arthrodesis of tarsus, what are places to apply plate? Preferred side?
Plantar, dorsal, medial, lateral
plantar = most biomechanically sound BUT dorsal or medial = most common
For dorsal approach to tarsus, cartilage on tibia should be cut at ___ degrees to long axis and ___ degree osteotomy on condylar surface of talus?
90 degrees on tibia
45 degrees on talus
What ancillary treatment can be added to a tarsal arthrodesis plate?
calcaneotibial screw
What is complication rate and outcome of pantarsal arthrodesis?
What is most common complication of medial plating?
complication 30-70%
good outcome 50-70%
medial plate –> plantar necrosis
What are treatment options to arthrodese calcaneoquartal and tarsometatarsal joints?
Outcomes?
cross pins, cross pins & IM pin, ESF, lateral plate
good outcome for both
What are origin / insertion of cranial & caudal cruciate ligaments?
Cranial
- caudomedial aspect of lateral condyle
- insert cranial intercondylar area
Caudal
- lateral surface of medial condyle
- insert medial edge of popliteal notch
What separates the lateral collateral ligament from the lateral meniscus?
popliteus tendon
What is hoop stress?
radial force resisted by tensile stress in circumferentially arranged collagen fibers of tissue
What ligament attaches the body of meniscus to tibia/femur?
coronary
What are the layers of meniscus / alignment of fibers?
surface - random orientation
deeper - innermost 1/3 = radial - deals with compression
deeper - outer 2/3 = circumferential - deals with tension
What is Mow biphasic theory?
mechanical behavior of meniscus under load depends on solid matrix phase & interstitial fluid phase (compressive load carried by fluid)
What are 3 blood supply zones of meniscus?
What % menisci get blood supply?
What blood vessels give the supply?
- Red-red zone (peripheral)
- White-white zone (axial)
- Red-white zone (intermediate)
15-25% of periphery
medial/lateral genicular artery
Under static load, menisci carry ___% load
40-70%
List if taut or loose with flexion/extension?
MCL
LCL
CrCL
CdCL
MCL - taut in flexion, taut in extension
LCL - lax in flexion, taut in extension
CrCL craniomedial band - taut in flexion and extension
CrCL caudolateral band - lax in flexion, taut in extension
CdCL cranial band - taut in flexion, lax in extension
CdCL caudal band - lax in flexion, taut in extension
What is the median flexion/extension angle of the stifle?
Flexion = 41 degrees
Extension = 161 degrees
120 degrees of ROM
Pozzi found (2010) medial meniscal release led to ___ % increase in peak contact pressure & decreased ___ % contact area
140% increase in peak contact pressure
50% decrease in contact area
Pozzi (2010) also found smaller ___% radial width partial meniscectomies had minimal effects. But ___% led to significant effects
<30%
75%
What is the Slocum & Slocum active model?
magnitude of thrust depends on compressive loads and slope of tibial plateau
What is the treatment for avulsion of the CrCL?
Epiphysiodesis – K wire in center of cranial intercondylar area of tibia directed parallel to tibia shaft
What are changes seen with histopath for CrCL?
- loss of fibroblasts from core
- decreased # of typical fusiform & ovoid fibroblasts
- increased # cells undergoing chondroid metaplasia
- decreased birefringence & elongation of crimping
What factors have been implicated with CrCL?
- synovial ab
- breed
- age (<2yr)
- sex = females
- neuter status
- BCS
- TPA conformation
- lack of fitness
What is the reported % rupture of CrCL in contralateral limb?
22-54%
What PE factor has been associated with bilateral CrCL disease?
bilateral stifle effusion
What are differences between postliminary and latent meniscal tears?
Postliminary = after initial procedure (from stable instability)
Latent = present at initial procedure but not identified because of failure of diagnosis at time of surgery
What is sensitivity and specificity of meniscal click?
Sensitivity = 50%
Specificity = 90%
Accuracy = 80%
What is specificity, sensitivity, and accuracy of a stifle with pain on flexion and meniscal click
Sensitivity = 85%
Specificity = 57%
Accuracy = 76%
Probing with arthrotomy ___x more likely to diagnose meniscal tear?
Probing with arthroscopy ___x more likely to diagnose meniscal tear?
2.1-2.6x (arthrotomy)
8x (scope)
Classify the meniscal tears
- Vertical longitudinal tears
- Oblique or flap tears
- Radial tears
- Horizontal tears
- Complex tears
- Degenerative tears
What are the 2 types of medial meniscal release?
Midbody
Caudal (via caudal meniscotibial ligament)
For lateral fabellar suture, what are the methods of tensioning/securing?
Tension
- Square knot
- Sliding knot
- Self-locking
- Tension device
Securing
- Square knot
- Sliding knot + square
- Self-locking + square
- Metallic crimp
What are the best tibial points to be most isometric of femur point on very caudal edge of lateral condyle just next to distal pole of fabella
Adjacent to extensor groove + PL attachment point
What is tightrope Arthrex made of?
Ultra high molecular weight polyethylene polyester
What is the advantage of Swivelock?
secured within blind-ended bone tunnel with interference screw suture anchor – NO knots!!
Also, decreases risks of intra-articular placement
What is the outcome for lateral suture?
good - 87% success rate
What has been associated with increased complication with lateral suture?
- high body weight
- young age with surgery
What are outcomes and complications of fibular head transposition?
69% excellent, another report says 51%, another one less than that…
- fibular fracture, tearing of LCL, post-op instability, seroma
For iota-articular CrCL reconstruction, what are the types of grafts/materials?
Autograft
- bone-patellar tendon-bone
- hamstring – tendon of semitendinosus, gracilis
- quadriceps femoris
Allografts
- all of the above
- Achilles
Synthetics
- dacron
- silk
- ligament augmentation device (LAD)
What is ligamentization?
inflammation from necrosis of fibroblasts due to ischemia causes fibroblasts vein filtration along collagen scaffold & secretion of new collagen during subsequent revascularization
What are the different osteotomy procedures to treat CrCL?
- CCWO
- triple tibial osteotomy
- TPLO
- TTA
- TTA 2
- TTA rapid
- Modified Maquet TTA
- CBLO
- TPLO/CCWO
What are advantages to doing cranial closing wedge?
- doesn’t need special saw
- can be done with open physis
- can decrease TPA to then use for TPLO
- can treat patella alta
- can address angular deformity w/o loss of bone apposition
What has been found to be associated with increased patellar ligament thickening on TPLOs?
- lower post-op TPA (<6 degrees)
- increased BW
What is the reported complication rate for TPLOs?
~7-28%
What are technical errors described for TTA?
- osteotomy fragment too small
- osteotomy cut too low
- not allowing proximal shift of tuberosity with advancement
- malalignment of tuberosity in frontal plane medially
- orienting plate so forks are too far away from loading edge of bone
- orienting plate so after advancement distal end lies caudal to tibial shaft
For TTA, what is re-operation rate?
Overall complication rate?
9.8% re-operation
19-59% complication
For triple tibial osteotomy, what is the wedge angle?
2/3 of angle between PL & line perpendicular to TP slope
WA = 0.6 x CA + 7.3
CA = angle of correction of PTA needed to achieve 90 degrees
List advantages/disadvantages to triple tibial osteotomy?
Advantages
- minimal change to orientation femur-tibial articulating surfaces
- small osteotomy gap
- no loss of limb length
- low technical difficulty
Disadvantages
- additional fixation/metal
- variability of post-op patellar-tendon-TP angle
List anatomic abnormalities associated with MPL (10)
- malalignment quadriceps mechanism
- coxa vara
- femoral varus
- genu varum
- shallow trochlear groove w/ poor developed/absent medial ridge
- hypoplasia of medial femoral condyle
- medial displacement of tibial tuberosity
- internal rotation of tibia relative to femur
- proximal tibial varus
- internal rotation of foot despite distal external tibial torsion
What age do you do trochlea chondroplasty?
<6 months
What % medium dogs have patella luxation? What % are medial?
~81%
Any sex predilection for medium-to-large dogs for patella luxation?
males > females
If torsion > __ degrees, don’t do a DFO to treat MPL
> 27 degrees
What is prognosis for deranged stifle? What are major complications?
good function with reconstruction/stabilization
arthrofibrosis and recurrent instability (most lose 30-40 degrees flexion after successful treatment)
What are classifications of patella fractures?
- non-displaced or minimally displaced
- apical
- basilar
- body
- displaced transverse body
- comminuted
How can you augment/assist repair of patellar ligament rupture?
What is prognosis?
- autogenous fascia lata graft
- transarticular splint
- transarticular ESF
- patellar ligament plating
Px = poor to good
Where in stifle does OC happen?
Prognosis?
axial (medial) part of lateral condyle (96%)
fair to poor, OATS promising
What are most common breeds for stifle OC?
Great Dane, Labrador, Golden Retriever, Newfoundland
For stifle arthrodesis, bone plate must span ___% of both long bones
60-70%
What angle do you place K wires to guide osteotomy for stifle arthrodesis?
90 degrees to long axis then 2 more 20 degrees to each of those
What causes pes varus in tibia? What breed commonly gets it?
eccentric medial closure of distal tibia physis –> slow medial growth
DOXIES
What causes pes valgus?
Abnormal growth of distal fibular physis
Where do you insert intramedullary pins for tibia?
medial border of PL with flexed stifle entering proximal tibia 1/3-1/2 distance from cranial surface of TT to medial condyle of tibia
What % of distal tibia fractures are open?
30-40%
What are treatment options reported for tibial tuberosity avulsion?
Prognosis?
- 2 K-wires
- 2 K-wires + tension band
- conservative (<2mm & small breeds)
- “Smillie Nail”
- Stille nail
- Zig-zog suture in patellar ligament
What are treatment options reported for tibial tuberosity avulsion?
Prognosis?
- 2 K-wires
- 2 K-wires + tension band
- conservative (<2mm & small breeds)
- “Smillie Nail”
- Stille nail
- Zig-zog suture in patellar ligament
- Prognosis = good; although premature closure of apophyseal growth plate & deformity of tibial tuberosity common (some say remove implants at 4 weeks)
For tibia/fibula, the nutrient artery comes from which artery?
cranial tibia
What arteries supply the fibular head vs. body?
head - cranial tibial br.
body - nutrient a. from peroneal a.
What % of long bone fractures are the tibia?
20%
What age usually gets tibial tuberosity avulsion? Breeds?
4-8 months
Greyhounds, Bull Terriers, +/- mini-poodles?
Tibia/fibula is __% of all fractures, >__% young pets, __% are open
- 10-20% of all fractures
- > 50% young pets
- 10-20% are open
__% growth length comes from the proximal tibial physis
40%
What age does tuberosity epiphysis fuse to proximal? What age closes?
5-9 months
> 12 months
What % growth comes from distal tibial physis? At what age does the medial malleolus fuses to distal epiphysis?
60%
4-5 months
What is the most common Total Knee design? Components?
- Canine total knee Biomedtrix
- semiconstrained cobalt chromium alloy - femur (with beaded undersurface) & mono bloc tibial cemented fixation
What are contraindications for TKR?
- infection
- neoplasia
- uncontrolled concurrent systemic disease
- loss of extensor mechanisms (patella, collaterals)
What are the 3 types of constructs for treatment of bicondular femur fracture?
- interfragmentary screw alone (or K-wires)
- inter fragmentary screws & IM or cross-pins
- inter fragmentary screws & buttress plate
What is the prognosis of condylar femoral fracture?
good but less favorable than non-articular
Why are chondrodystrophic dogs more prone to supracondylar fractures?
elongated distal femur & caudal orientation generates greater bending moments at the supracondylar region
What is Blumensaat’s line?
proximal extent of intercondylar notch (where tip of interlocking nail should extend)
For distal femoral physeal fracture repairs, what has been associated with poor outcome?
- under reduction of epiphyseal segment caudally
- varus or valgus
- insufficient epiphyseal pin purchase
What is the difference between coxa vara & coxa valga?
Vara - decreased angle of inclination
Valga - increased angle of inclination
What is the angle of inclination?
intersection between anatomic axis & axis bisecting femoral neck
What are the averages of angle of inclination?
132-137 degrees
What makes angle of ante version? Average?
head/neck axis & trans-condylar axis
Avg = 16-31 degrees
What is the tension surface of the femur?
lateral
What is success rate of interlocking nail for femur fracture?
83-96%
What is slack?
unstable rotation/bend
When should Targon ILNs not be used?
if ratio between diameters of cortical drill hole & diaphysis >56%
Targon nails have big bolts
What primarily provides blood supply to femoral diaphysis?
- medial circumflex femoral a. br.
- metaphyseal a.
- periosteum important in young dogs
What % of long bone growth comes from distal femoral physis?
75%
What % of femur fractures are diaphyseal?
56%
What is the 1st screw to place with plate application for treatment of subtrochanteric femur fracture?
transcervical screw within proximal segment inserted obliquely through 2nd or 3rd most proximal hole engaging femoral head & neck
Is collapse common with apple coring?
not common; apple coring is usually self limiting
What animals have more commonly been seen to have slipped capital femoral epiphysis? (form of capital physeal dysplasia)
cats > dogs
overweight, castrated males
Which species more often get femoral neck/cervical fracture?
cats 3-5x more than dogs
usually <1 yr
Shear stresses of femoral cervical fracture are minimal when fracture plane < or = ___ degrees to transverse plane
less than or = to 30 degrees
what is the German (?) approach to the femur?
osteotomy of the greater trochanter (dorsal approach)
What is an advantage of ventral approach to femur?
decreases interference of epiphyseal blood supply
What % of femur fractures are proximal?
25%
What type of Salter Harris is most common for capital physeal fracture?
What % of cases have separation of trochanteric physis?
SH 1
11-15%
What age does proximal femoral physis separate?
2-3 months
What % longitudinal growth comes from capital physis?
25%
When does the growth plate of capital physis close in dogs vs cats?
Dogs = 9-12 months
Cats = 7-10 months
Femur fractures are ___% of all fractures in dogs?
___% of all long bone fractures?
20-25% of all fractures
45% of all long bone fractures
___% of femur fractures are in animals <1yr
48%
Describe femur fracture classification adapted by AO
3 = femur
2nd number = position of fracture within bone (1 - proximal, 2 - shaft, 3 - distal)
A = single
B = wedge or butterfly
C = complex or >1 fragment
Final # = severity, prognosis (1 - least severe, 3 - severe, guarded to poor)
Schlag et al - JAVMA 2019 (Ehmer)
- outcomes of craniodorsal hip luxation with closed reduction and Ehmer sling
- 43.5% reluxated at or near time of sling removal
- 50% of patients had ST injury from sling
Likely to have severe sling injury
- 12.5x more likely with poor owner compliance
- 4x more likely if placed by intern
- 5.7x more likely if soiled/wet bandage
What is mass selection?
making selection decisions on individuals hip joint phenotype
What is heritability?
Defined as the ration of additive genetic variation to overall phenotype variation of given trait
estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population
What is the equation for determining genetic change?
change = h^2 x (Avg parents - Avg population)
What are ideal characteristics of a hip screening tool?
- ideal metric accurate
- metric should be precise
- metric represented as continuous ratio scale
- ideal metric measurable as early as possible in life and constant throughout life
- must have heritable component
- selection pressure
What is the Wiberg angle?
CT view - to look a femoral head position to acetabulum
Similar to Norberg angle but 90 degrees less in magnitude)
What are kinematic changes noticed in CHD?
- increased hip extension at end stance phase
- increase femorotibial flexion throughout stance and early swing phase
- coxofemoral deceleration early in stance phase
- increased stride length
- decreased PVF
For OFA, FCI, BVA, U-Penn, and DLS, what is the scheme for evaluation?
- OFA: 7 point cardinal grade system (excellent to severe)
- FCI: Letters A-E (A1 = best grade); Norberg angles >100 = scores A & B
- BVA: made for GSD; 9 radiology features (8: 0-6; 1: 0-5); worst 53/hip = 106
- U-Penn: D1 0.3 cutoff point; 0 = full congruency
- DLS: subluxation quantified assessing % femoral head coverage; ~56% femoral head coverage about equal to D1 of 0.3
- Flockiger subluxation: subluxation index measured by circle gauges
What are osteoarthritic markers for CHD?
- caudolateral curvilinear osteophyte (CCO)
- circumferential femoral head osteophyte (CFHO)
What is “puppy’s line”?
indistinct subtle opacification on femoral neck in area of CCO (incidental)
List radiographic derived systems/methods to objectively/subjectively determine CHD?
(state if hip extended or neutral)
- Orthopedic Foundation for Animals (OFA) - extended
- Federation Cynologique Internationale - extended
- British Vet Associated/Kennel Club - extended
- U-Penn Hip Improvement Program - neutral & Fluckiger subluxation index
- Dorsolateral subluxation score - neutral & Fluckiger subluxation index
What % of dogs with CHD have CCLr?
32%
What is the Barlow test?
1st part of Ortolani – adducted & dorsal pressure to subluxate femoral head
What is Barden’s test?
- femur perpendicular plane of pelvis, lateral force is applied with 1 hand lifting femur without abduction, other hand resting on greater trochanter
- finger pressure medial thigh elicits Barden sign
- Greater trochanter > 1/2” = laxity
What is joint reaction force?
forces crossing joint representing vector addition of gravitational forces and muscle forces to balance movements of standing/movement
What are sequential biomechanical steps with hip dysplasia?
- peri-articular muscle force increases (compensate for lateral movement)
- increased cartilage stress (due to smaller area)
- Functional subluxation - likely subluxate during swing phase with femoral head moving medially to reduced position with weight bearing –> catastrophic reduction
List treatment options for hip dysplasia
- conservative (PT, NSAIDs, rest, etc.)
- JPS
- TPO/DPO/ 2.5 PO (literature)
- THR
- FHNE arthroplasty
- hip denervation
- pectineus myectomy
Subsidence <___mm is NOT clinically important
< or = 4-5mm
What do you need to remove for revision of aseptic loosening? Why?
remove periprosthetic fibrous membrane –> contains indicators of bone lysis
What angles of lateral opening lead to craniodorsal hip luxation and caudoventral hip luxation?
> 60 degrees - craniodorsal
<25 degrees - caudoventral
What are other factors to affect hip luxation?
- hip joint laxity
- periarticular osteophytes
- hip joint conformation
- architectural changes
What are Vancouver classifications of femur fractures with THR?
- Ag/Al = level of greater or lesser trochanter
- B = involves prosthesis
- C = fracture distal to prosthesis
List mechanical, biological, & implant failures for total hip arthroplasty
Mechanical
- luxation
- femoral fracture
- acetabular fracture
- cup avulsion
- subsidence
Implant
- failure of metal part
- polyethylene failure
- fracture of cement mantle
- debond cement-metal interface
Biological
- aseptic loosening
- septic loosening
- femoral infarction
- pulmonary embolism
- sciatic neuropraxia
For femoral head to neck ratios, larger ratio leads to greater ROM but ____ and a large femoral head leads to ___
greater ROM but small femoral neck predispose failure or fracture
larger head leads to decrease risk of luxation BUT more wear
What is the version angle of acetabulum? Goal?
cranial or caudal angulation, 15-20 degrees
15 = goal
What is the positive angle of inclination of the acetabulum?
angle dorsal to iliac-ischial axis
What position for angle of lateral opening is typical?
about 45 degrees
What is femoral offset? What happens when it is increased?
distance between center of rotation of femoral head & anatomic axis of the femur
increased = greater impingement-free ROM
What is jumping distance? What happens when it increases? Downsides?
distance femoral head travels or subluxates before luxation occurs
Increased = greater resistance to luxation BUT increases wear debris
What happens with lower or higher angle of inclination
lower = greater lateralization & greater bending moment
For impingement - what is the difference between longer and shorter necks?
longer neck = less impingement BUT less force to induce luxation
shorter neck = greater impingement BUT greater force to induce luxation
Greater the femoral neck ante version leads to ___? What happens with normo/retroversion?
- greater ROM BUT increased risk of craniodorsal luxation with external rotation
- normo or retroversion – caudal luxation
For cemented THR system, ingrowth occurs with pore size ____ & micro motion must be <____
pore size 50-400 micrometers
motion <20 micrometers
What % porosity is ideal for growth?
30-40%
What is the Helica “stemless” implant?
both femur/acetabulum screw in design with self tapping helices threads
What does hydroxyapatite do?
osteoproductive - gives CaPO4 base for deposition of bone
How can the interface for cemented implants be strengthened?
roughen surface - sandblast or bead blast
What are 3 cementing techniques?
- centrifugation - vacuum with cement mixing
- pressurization - cement injector & plastic IM cement restrictor
- pulsatile lavage - minimize blood/fat interposition
- For acetabulum - holes/troughs drilled
What are properties of ceramics?
- harder than metal
- high elastic modulus (>300x bone)
- cracks (large particle size)
What can decrease some of the downsides of ceramics?
add oxides & hot isostatic pressing = decreases size/cracks
What are 2 types ceramics? Which are better properties?
- Alumina (better): fluid film lubrication (hydrophilic)
- Zirconia: poor thermal conductivity, generates heat with loading
What are types of hip articulations & which is most common?
- metal on polyethylene (most common)
- metal on metal
- metal on ceramic
- ceramic on polyethylene
- ceramic on ceramic
What usually makes up acetabular bearing surface of THR? Properties?
- UHMW polyethylene
- good, low friction
- prone to wear debris
What makes the metal component of femoral head for THR?
- Cobalt-chromium (downside = cytotoxic)
- Titanium alloy (downside = more wear debris)
What coating options are available for THR implants?
- Ti-N ceramic (decreases reduction wear rates but scratching)
- Diamond-like carbon (amorphous; decreases friction, wear resistant, biologically inert)
What are reported methods to decrease incidence of screw loosening for TPO/DPO?
- screws penetrate deeper body of sacrum (>90%)
- SI joint not entered (different study)
- with cancellous screws
What are complication rates for for pelvic osteotomy?
- TPO: 35-70% = screw loosen/pelvic canal narrowing
- DPO: 3.2% screw loosening (2010)
- For 2012 (Rose) - locking plate 0.4% screw loosening
What is the prognosis for bilateral TPO/DPO?
good
What are guidelines for patient selection to get DPO/TPO?
- laxity of hip (but no complete luxation)
- no radiographic evidence of OA
- <1 year old (some say <10mo)
What reduction angle has become proposed as prognostic factor of getting OA?
<15 degrees less likely to get OA (Gatineau 2012)
What is the order of steps for TPO? Which step ISN’T done in DPO?
- Pubic ostectomy (medial to iliopectineal eminence) or pubic symphysiotomy
- ischial osteotomy - caudal to center of ischiatic table
- ilial osteotomy - just caudal to SI joint
**DPO - NO ischial osteotomy
What are settings for JPS? (between 2 types of units?)
- 500kHz electrosurgery 40w (monopolar)
- current 10-30 seconds every 2-3mm along cranial 1/3 to 1/2
- 4mHz radiowave 50w (spatula)
- coag setting & current 7-8 seconds
What are complications of JPS?
- excessive ventroversion of acetabulum leads to caudomedial subluxation
- lack of efficacy (surgical error?)
What type of joint is pelvic symphysis?
synchondrosis then synostosis
What dose bone start to replace the pelvic symphysis?
9-21mo
What is the arcuate ligament?
crosses ischial arch - ossified often
What age is recommended for JPS?
12-20 weeks
What is a contraindication to JPS?
ANY visible OA
Describe sizes of screws for SI luxation?
- 2/2.7 - small dogs and cats
- 3.5 or 4 - medium size
- 4.5 & 6.5 - large
Where can a 2nd screw be placed?
dorsal/cranial to 1st (only giant breeds, deep set)
What % SI injury are unilateral? % bilateral?
77% unilateral
23% bilateral
Describe location for sacral screw in dogs vs. cats
- dog = on line 40% from ventral point of sacral wing 100 degrees & mid-distance notch & C shaped cartilage
- cats = hole 51% of sacral wing length 97 degrees just cranial to C shaped cartilage dorsal margin sacral wing 47% wing height
Describe location in ilium for screw placement dogs vs. cat
- dog = middle of caudal 1/2 tuber sacrale, level dorsal 1/3 width of ilium
- cat = 31% length of tuber sacrale from caudal aspect & 52% ilial height
What is usual approach for acetabular fracture?
What else provides exposure?
dorsal approach & osteotomy of greater trochanter
tenotomy/elevation gemelli & internal obturator
List options for surgical repair of the acetabulum?
- plates: straight, curved acetabular, recon, T plate, L plate
- plate +/- PMMA
- screws + PMMA
- wires + PMMA
- screws / lag fashion
What is the prognosis for acetabular fracture?
good with plate but OA
Describe the types of acetabular fractures?
- cranial: cranial 1/3
- dorsal: dorsal or middle 1/3 (articular surface) - some refer to this as “central”
- caudal: caudal 1/3 (maybe manage conservatively)
- central: medial wall (acetabular fossa, +/- some articular surface)
What is secondary acetabular protrusion?
medial luxation of femoral head in pelvic canal after acetabular fracture; may need salvage procedure
What are the 3 techniques to reduce ilial fracture?
- direct manipulation with bone forceps on caudal segment to lever to lateral
- use implant (attached to caudal) - gives reduction & mobilizes caudal segment
- “forceps sliding maneuver” - oblique fragments
List fixation options for ilial fractures?
- ventral plate
- ventral lag screws
- T-plate (lateral)
- straight/recon plate lateral
- dual plate lateral
- orthogonal plate lateral
- dorsal plate
- ESF
- pin/screws + PMMA
What % of all dog/cat fractures are pelvis?
16% (dog)
25% (cats)
What % are related to HBC injury? What % fracture at 3 or more sites?
90% cats
77% dogs
76% have 3 or more sites
What part of pelvis fractures most?
pubis > ischium > SI joints > ilium > acetabulum
What % of animals have injury to weight bearing axis? Unilateral or bilateral?
Unilateral - 89%
Bilateral - 39%
