JOINTS Flashcards
tx tight in extension (unable to achieve full extension), balanced flexion
cut more distal femur
cut off for aspirate TKA
WBC more than 1100
PMN more than 64%
cut off for aspirate THA
WBC more than 3000
PMN more than
cam mech
in PS knee
post built into poly that articulates w fem component in flexion
loose flexion gap in PS knee causes
posterior knee dislocation when cam jumps the post in flexion
osteolysis cellular mech
macrophage activation and bone resorption (lytic lesion on XR)
ideal size of cement mantle
at least 2 mm
contraindication for constrained acetab liner
malpositioned implant
young pt w large inherent ROM
if pt had prior patellectomy what type of TKA
posterior stabilized TKA
if fem component has a box then it is
Posterior stabilied
indications for constrained acetab components
1) abd insufficiency/capsular attenuation
2) neuro dz
3) well positioned comp
WAYS to incr hip dislocation
head neck ratio
decr head neck ratio
WAYS to decr hip dislocation
skirted femoral head
incr dislocation bc decr head neck ratio
osteolysis is due to macrophage response to wear particles of what size
less than 1 micron in size
indications for constrained nonhinged TKA
varus/valgus deformity w MCL/LCL incompetency
post polio
neuorpathic arthropathy
how to measure femoral offset
distance from center fem head to line down fem shaft
how to decr osteolysis around distal fem stem
use proximally circumferentially coated ingrowth stem
indications for constrained acetab component
recurrent dx due to
- capsular attenuation
- abductor dysfunction
- cog dz
- late dx w well positioned components
if tight in both flexion/extension do what
resect more prox tibia
high or low osteolysis with alumnia ceramic
low
mc reason for reoperation in 1st 6 months after hip resurfacing
fem neck fx
release of popliteus does what in valgus knee
increase lateral flexion space
how to decr Q angle and patellar subluxation
ER fem/tibial component
moving fem head medially will incr or decr offset
incr
changes to tibia incl poly affect flexion vs extension
changes to femur
tibia = affects both flex/ext
femur = affects one of the two
what inhibits ossteolysis
IFN gamma
OPG
IL4
IL10
median parapatellar approach vs quad sparing for TKA
median = better alignment
offset liner
incr or decr joint reactive forces
incr
incr or decr joint reactive forces
extended offset femoral component
incr
incr or decr joint reactive forces
varus neck angle (more than 120)
decr
type of wear
pitting/delamination
fatigue wear
type of wear
deformation w/o wear
creep
type of wear
removal of material on the backside of modular tibial components
adhesive/abrasive wear
valgus malalignment TKA usu due to
deformity in distal femur (varus = proximal tibia)
for valgus knee avoid femoral malrotation by referencing
AP axis (not hypoplastic LFC)
complication unique to computer nav in TKA
fem shaft fx
painful catching in PS TKA due to?
tx?
patellar clunk syndrome due to extensor mechanism over trochlear notch from flex to extension
tx = arthro synovectomy
mechanism of alendronate
inhib farnesyl pyrophosphate synthase (nitrogen containing)
mechanism of denosumab
RANKL inhibition
mech of steroids
phospholipase A2 inhib
incr risk of peroneal nerve injury
preop valgus alignment, hx of HTO
adhesive vs abrasive wear
adhesive = rubbing 2 hard surfaces so transfer from less to more wear resistant material
abrasive wear = surface imperfects with less-wear-resistant material
medial gastroc flap relies on which artery
medial sural artery
what is best tka implant that decr poly wear and bone-implant interface stresses
mobile bearing TKA
incr risk of what after acetab liner revision
dislocation
revision surgery for acetab fx with medial cup migration
acetab revision with cup-cage construct (not triflange = only for bone loss)
highest risk of PJI
revision TKA
best tka for neuromuscular disease with valgus knee
rotating-hinge TKA
osteolysis after tha correlated with
linear wear rate
wbc and pmn % for PJI in TKA
wbc more than 1100
pmn % more than 64%
disadvantage of highly cross linked poly
decr toughness
decr ductility
decr fatigue strength
improved wear properties
how does femur change from flexion to extension
MEDIAL PIVOT femur INTERNALLY ROTATES relative to tibia
femur translates ANTERIORLY
moving acetab component more medial = incr or decr stability of hip
decr
mc complication of custom triflange component
dislocation
mechanism of osteolysis
1) macrophage make TNFa, IL-1
2) promotes RANK-RANKL
3) activate osteoclasts
RANKL produced by
osteoblasts
function of OPG
OPG binds RANKL (so RANKL can’t bind RANK on osteoclast precursor cells)
wear rate above what is considered significant
0.1 mm per year
