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93 Cards in this Set

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Best bearings for hard-soft couple
Co-Cr-PE
Best bearings for ceramic components
Alumina best. Zirconia bad- undergoes phase transformation -->changes surface roughness
Hip lubrication type in hard-soft bearings
Boundary (synovial fluid can't separate asperites)
Indication for Ti alloy THA components
Nickel allergy
Best technique for polyethylene manufacturing
direct compression molding
Effects of calcium stearate on polyethylene
Creates areas w/ unfused PE particles--> dec mechanical properties
Advantages of PE cross-linking
improves resistance to adhesive and abrasive wear
Disadvantages of PE cross-linking
Decreased: tensile strength/fatigue strength/fracture toughness/ ductility
Effects of PE oxidation
molecular chain scission. Accelerated PE wear/failure.
Effects of crystallinity on cross-linking
Only amorphous areas cross-link. If crystallinity over 70% then higher failure rates
Particles generated hard-hard bearings
more particles. Much smaller (0.015-0.12 micron). Run in period during first million cycles. Cleared locally via lymph.
Lubrication type hard-hard bearings
Mixed (boundary/hydrodynamic-completely separated). Hydrodynamic phase d.o. head size >38mm/velocity/roughness.
Smoothness of bearings
Ceramic>metal>>>PE
Radial clearance
Difference in radius of head and cup. Bigger head--> equatorial contact. Smaller head-->polar contact. Optimal <150 micron clearance- w/ polar contact with high bearing conformity.
Stripe wear
Seen w/ hard on hard bearings. Assoc w/ edge loading. Represents surface wear.
Positions associated with hip edge loading
heel strike/ stair climbing/rising from chair
Third generation cement preparation
Vacuum-->dec porosity. Pressurized cement. Precoated stem. Rough surface finish. Stem centralizer.
Cement mantle
2mm suggested. 2/3 rule: 2/3 canal filled w/ stem- 1/3 filled w/ cement. NO contact bet femoral stem and cortex
Femoral component design cemented THA
Stiffer preferred (elastic-->transfers stress to cement). Precoating--> no difference. Medial flange--> no difference.
Porous coated components
Bony ingrowth. Pore size 50-350 microns. Porosity 40-50%. Gaps < 50 microns
XR findings of stem fixation
Spot weld: inc bone density surrounding distal extent of porous coating (well fixed). Intramedullary pedestal: e/o loose components.
Prime factor contributing to stress shielding
Stem stiffness
Factors affecting stem stiffness
1. 4th power of stem radius. 2. metal (Co-Cr stiffer than Ti). 3. Geometry
Incidence of dislocation
1-2% primary. 26% revision. Highest in elderly with THA post failed femoral neck fx fixation
Main determinant of primary arc
head-neck ratio
Excursion distance
Distance head must travel to dislocate (1/2 diameter of femoral head)
Ideal acetabular alignment
15-30deg anteversion. 35-45deg coronal tilt
Need for revision post dislocation
2/3 treated succesfully nonop. 1. if dislocates within functional range post-reduction. 2. after >2 dislocations
Treatment total hip w/ loss of greater troch attachment
Reattachment not succesfull. Tx: larger head +/- constrained liner
Most common cause of THA revision
Cemented: failure of acetabular component. Non-cemented: failure of femoral component (osteolysis)
Most common complication hip resurfacing
Femoral head fracture- risk: notching/osteoporosis/osteonecrosis/misplaced acetabular cup--> impingement
Acetabular revision
Porous coated hemisphere cup w/ screws best. Can use hemisphere cup if 2/3 rim remains. Cavitary defects filled w/ graft. Structural allograft- high failure rate (secondary to graft resorption/component migration). Recon cage: for segemental defects. Fail 2/2 abduction pullout.
Acetabular component screw placement
Posterosuperior: safe- risk: sciatic n/superior gluteal a/v. Anterosuperior: risk: external iliacs. Posteroinferior: safe if <20mm. Risk: sciatic/inferior gluteals/internal pudendals. Anteroinferior: risk: anterior inferior obturator n/a/v.
Femoral stem revision
noncemented/extensively coated porous coated/long-stem. Pass 2-3cm below original or 2 shaft diameters below defect.
Timing of periprosthetic fractures
non-cemented: <6 months- stress risers . Cemented: 5yrs ave @ stem tip/distally- cortical defects
Tx periprosthetic greater troch fracture
nonoperative
HO after THA
higher risk: contralateral HO/ direct lateral approach/prior fusion. Reop only if severe dec ROM/pain. Nonop tx not effective. Prevention: 600-750cGy w/in 48hrs (shield noncemented parts). Indomethacin 75mg x6wks
Nerve injury post THA
peroneal div sciatic most common- closest to acetabulum at ischium. Usually 2/2 retractors. Risk: lengthening over 3.5cm
Balancing varus deformity
1. osteophytes. 2. deep MCL. 3. posteromedial corner. 4. sup MCL. 5. PCL- rare
Balancing valgus deformity
1. osteophytes. 2. lateral capsule. 3. IT if tight in extension/ popliteus if tight in flexion. 4. LCL
Balancing sagittal plane deformities
Symmetric: adjust tibia. Asymmetric: adjust femur
Indications for cruciate substituting design
previous patellectomy/ inflammatory arthritis/ PCL deficiency
TKA component alignment- patellofemoral balancing
Femur: ER/medialize. Tibia: ER/center over medial 1/3 tubercle. Patella: medialize/central.
Femoral condyle size
Medial larger than lateral
Addressing pateall baja during TKA
Lower joint line. Patella: small dome placed superiorly. Cut but don't resurface or patellectomy if severe
PE thickness TKA
Thinnest portion larger than 8mm.
Effects of PE machining
shearing forces--> stretch subsurface 1-2mm-->sensitize to oxidation (white band of subsurface oxidation)
Flexion closure
assoc w/ quicker flexion recovery. Avoids need for CPM
Manipulation arthrofibrosis post TKA
4-6wks postop ideal. Inc risk supracondylar fx if wait longer or femoral notching.
Patellar clunk syndrome
PS knees only. Tissue on posterior quad above sup pole of patella- catches in box at 35-40deg- pops back out--> clunk
Rectus snip
oblique transverse cut medial--> lateral quad tendon- risk diastasis of repair--> extensor lag
Indications for constrained non-hinged TKA
MCL attenuation/ LCL deficiency/ flexion gap laxity. Controversial for MCL deficiency- high stress
Indications for constrained hinged knee
global ligament deficiency/hyperextension instability/ s/p joint resection. Must have medullary stems and rotating platform.
Location of knee joint line
1.5-2cm above fibular head
Tx nondisplaced supracondylar periprosthestic fx
cast/brace
Tx supracondylar periprosthetic fx extends distal to flange/ comminuted
revision TKR w/ medullary stem
Flap coverage TKA
medial gastroc flap (off medial sural artery)--> medial/lateral. Lateral gastroc flap only useful for lateral wounds.-- risk common peroneal palsy from flap traction
UKA vs TKA
faster early recovery/rehab. Fewer short term complications. Smaller incision. Worse long term complications.
Contraindications UKA
1. ACL deficiency. 2. fixed varus. 3. knee flexion less than 90deg. 4. inflammatory arthritis. 5. highly active patient/laborer.
Correction varus deformity w/ UKA
correct to 1-5deg valgus
Failure UKA
fixed bearing: mechanical loosening. Mobile bearing: disease progression
Most common complication TSA approach
axillary nerve injury
Most common reason for failure of TSA
glenoid loosening
Glenoid bone stock and TSA
Can't proceed of glenoid wear to coracoid. Relative retroversion common 2/2 OA
Humerus positioning TSA
20-30 deg retroversion.
Instability s/p TSA
anterior- 2/2 subscap pull-off
TSA s/p 4 part humeral fx
Anatomic positioning tuberosities key to function. Nonunion--> instability
Rotator cuff arthropathy tx
1. reverse TSA. 2. hemi w/ large head--> 40-70 deg elevation. 3. RTC reconstruction- combine w/ resurfacing. Must retain CA ligament- avoid superoanterior escape.
Wiberg angle
lateral center edge angle (>20deg nml)
Lequesne angle
anterior center edge angle (>20deg nml)
Acetabular index
>5deg nml (Tonnis angle)
Crossover sign
e/o acetabular retroversion
THA s/p DDH
Place head into native acetabulum. May need subtroch osteotomy for shortening to realign. Lengthening over 3.5cm--> risk sciatic nerve injury.
Advantages of ganz periacetabular osteotomy
1. multiplanar. 2. allows large corrections. 3. medializes joint. 4. inherent stability (post column intact). 5. avoids hip abductors
Subtrochanteric osteotomy for DDH
Correction of coxa valga and excessive femoral anteversion. Do not use closing wedge for flexion (compromises future THA)
Contraindications HTO for knee OA
1. lateral tibial subluxation >1cm. 2. bone loss medial compartment. 3. flexion contracture >10deg. 4. Knee flexion less than 90deg. 5. Varus >10 deg.
Poor prognostic indicators HTO
Unable to obtain 8-10 deg valgus/ overweight patient-- if both then 60% failure @ 3yrs
Proximal tibia lateral closing wedge osteotomy- complication
Main complication: recurrence, loss of posterior tibial slope, patella baja
Proximal tibia opening wedge osteotomy- complication
nonunion, collapse of opening wedge. Better at maintaining posterior slope than closing wedge
Distal femoral varus-producing osteotomy
Goal: produce horizontal joint line w/ tibiofemoral angle of 0 deg. Most common complication after converting to TKA is inability to restore anatomic valgus
Hip arthrodesis
Indication: <35yo w/ severe post-traumatic arthritis. Requires 30% more energy. DJD 15-25yrs postop in lumbar spine (55-100%)>ipsilateral and contralateral knee>contralateral hip. Position: 0 add/0-15 ER/20-25 flexion.
Conversion hip arthrodesis to THA concern
abductor function: consider EMG/NCS of gluteus medius preop. If absent then conversion contraindicated.
Knee arthrodesis
Indication: most common- failed TKR. Position: 5 valgus/ 0-10 ER/ 0-15 flexion. IM fixation preferred if bone loss.
Shoulder arthrodesis
Contraindicated if ipsilateral elbow arthodesis. Position: 30/30/30. Rotation most critical in optimal function.
Mechanism osteolysis
Particles ingested by macrophages--> activated macrophages release TNF-alpha/IL-1/IL-6/PG/hydrogen peroxide/acid phosphatase-->activate osteoclasts
Tx osteolysis around acetabular screw
if cup well fixed: poly exchange, debride and bone graft osteolytic lesion. Revise cup if not well fixed
Early postoperative infection- total joint
within 3wks of implantation. Tx: poly exchange/ I&D/ abx x 4-6wks
Hematogenous infection- total joint
Seeding well established implant. Tx: poly exchange/I&D/ abx x 4-6wks. Implant exchange if recurrent.
Chronic infection- total joint
infection present >3wks. Usually coag - staph aureus. Tx: implant exchange
Dental prophylaxis s/p arthroplasty
First 2yrs. Lifetime if immunocompromised/immunosuppressed (RA/SLE/DM/previous total joint infection)
Core decompression osteonecrosis
Indications: early ON before collapse. Effects: pain relief. Poorer results if steroid induced
Rotational osteotomy for osteonecrosis
Indications: small lesion in weight-bearing area (<50%). Goals: rotate affected area out of weight-bearing area. CI if over 50% involvement.
Vascularized bone graft for osteonecrosis
Indication: early stage ON. CI if whole head involvement. Goal: prevent subchondral collapse.