Arthroplasty

Question 1

Releasing the PCL during TKA does what to the flexion and extension gaps?

Answer 1

Significant increase in extension gap
Average increase in flexion gap

Question 2

Recurvatum or hyper extension deformity of the knee is best addressed with this TKA design when performing total knee arthroplasty?

Answer 2

Rotating hinged construct

Question 3

Inflammatory cell type for metal on metal hips/metalosis?

Answer 3

Lymphocytes

Question 4

Inflammatory cells for polyethylene wear?

Answer 4

Macrophage

Question 5

What is modern Morse taper design?

Answer 5

-12/14 taper
-Similar metal types between head and trunnion (limit corrosion)
-Apply head to a dry taper

Question 6

C. Acnes is susceptible to which antibiotics?

Answer 6

Penicillin
Zosyn
Vancomycin

Question 7

Factors that contribute to total hip arthroplasty joint reaction force?

Answer 7

Medializing the acetabulum decreases joint reactive force so,

-lateralized acetabular liner
-incompletely medialized cup
-extended offset femoral components

Question 8

For TKA soft tissue balancing laterally, what structures are tight in flexion and extension?

Answer 8

Tight in…

Extension: IT band
Flexion: popliteus

Question 9

Hetertopic ossification matures after ____? And can be monitored by this test?

Answer 9

18 months
Serum alk phos levels

Question 10

Inferior gluteal artery is located where during posterior approach?

Answer 10

Inferior to piriformis

Question 11

Press fit stems should be made of this material?
Cemented stems?

Answer 11

Titanium

Cobalt chrome/stainless steal

Question 12

Ductile definition

Answer 12

Large amount of plastic deformation

Question 13

Creep definition

Answer 13

Progressive deformation over time

Question 14

Order of decreasing Young’s modulus for arthroplasty material?

Answer 14

Young’s modulus is stiffness (stress/strain).

Ceramic
Cobalt chrome
Stainless steal
Titanium

Question 15

Cement is good in _______ but fails with ____

Answer 15

Compression
Shear

Question 16

Process for cross linking polyethylene?

Answer 16

Irradiation
- leads to cross-linking via production of free radicals (must be done in inert environment)

Free radical elimination
-done via reheating/melting and vitamin E (need to remove residual free radicals so the poly does not oxidize in the patient)

Sterilization
-ethylene oxide
-gas plasma

Question 17

Three processes to remove polyethylene free radicals after cross linking irradiation?

Answer 17

Melting (changes shape)
-highly effective
-reduces polyethylene mechanical properties

Annealing (heating, does not change shape)
-less effective
-maintains mechanical properties

Vitamin E
-biological antioxidant

Question 18

Trade off of polyethylene irradiation

Question 19

Effect oxidation has on polyethylene?

Answer 19

Increases elastic modulus (stiffness) and decrease strength

Question 20

THA goal combined anteversion?

Answer 20

35-45 deg

Question 21

Benefits of using a larger femoral head for THA?

Answer 21

Greater arc of ROM and less risk of impingement.
Larger head jump distance for dislocation.

Question 22

Abrasive wear

Answer 22

Caused by 3rd body trapped between two surfaces

Question 23

Adhesive wear

Answer 23

Most important process in osteolysis caused by chemical bonds between the poly and implant surface which then trigger the osteolysis cascade

Question 24

Osteolysis cascade

Answer 24

Adhesive wear
Macrophages ingest particles and release inflammatory molecules TNF alpha, IL-6
The osteoclasts are then activated and remove bone.

Question 25

Cell type involved with metal on metal hips?

Answer 25

Lymphocyte

Question 26

Serum ion levels above what value is a problem?

Answer 26

>7 ppb

Question 27

After explanting a metal on metal THA, what are the best next implants to re-implant.

Answer 27

Ceramic head Polyethylene liner

Question 28

Diagnostic criteria for trunionosis?

Answer 28

Cobalt > chromium elevations 2:1 or greater

Question 29

Mecahanism of trunionosis?

Answer 29

-Fretting corrosion: Mechanically assisted micromotion between two surfaces that disrupt the protective oxide layer -Crevice corrosion: crevices create local conditions that increase oxidation

Question 30

How to revise trunionosis

Answer 30

Convert to ceramic head with titanium sleeve Must have titanium sleeve because if resting the stem the corroded reunion can fracture an otherwise standard ceramic head

Question 31

Long term risk of hemiarthroplasty?

Answer 31

Protrusio

Question 32

Praprofsky femur classification and treatment?

Answer 32

Classification for loose femoral stem 1. Loose stem, no ingrowth, no bone loss 2. Metaphyseal bone loss 3. Metaphyseal + cortical bone loss 4. Extreme near complete bone loss 1. Standard metaphyseal fit stem 2. Diaphyseal fit stem 3. Diaphyseal fit stem 4. Mega prosthesis

Question 33

Criteria during a revision of the acetabulum to use cementless hemispherical cup (with screws)?

Answer 33

2/3rd rim fit 50% acetabular bone stock necessary

Question 34

During cartilage revision if there is pelvic discontinuity you want to use these implants?

Answer 34

Cup-cage or triflange implant

Question 35

VTE prophylaxis pearls

Answer 35

Question 36

Mechanism of action of TXA

Answer 36

Binds plasminogen and prevents the breakdown of fibrin

Question 37

Things to know about DDH when doing THA?

Answer 37

Lack of anterior and lateral acetabular coverage. The acetabulum is naturally more anteverted. The femur is more anteverted.

Question 38

MCL differential functions of the anterior portion of the MCL and the posterior oblique portion?

Answer 38

Anterior MCL: tight in flexion Posterior oblique portion: tight in extension

Question 39

When do you do a coronal correcting osteotomy during TKA?

Answer 39

- when deformity on distal 1/4 of femur or proximal 1/4 of tibia and > 20 deg *must be closing wedge *use diaphyseal fit stem with splines to provide rotational stability

Question 40

Postop wound drainage after ___ days requires a washout.

Answer 40

5 days *every subsequent day increases infection risk 42% in hips and 29% in knees

Question 41

Largest arterial contribution to the patella?

Answer 41

Inferomedial geniculate artery