Goldstein Lists

Question 1

1. Factors leading to an increase in stress shielding (4)

Answer 1

• Bigger stems (stiffness α r4)
• Stiffer metals (Co-Cr > SS > Ti)
• Stem geometry (solid cylinder)
• More extensive porous coating

Question 2

2. Factors affecting rates of polyethylene wear (9)

Answer 2

• Manufacturing process
• Post-processing modifications
• Sterilization process
• Packaging method
• Shelf life
• Thickness
• Locking mechanism strength
• Constraint
• Conformity
• Activity level
• (Production → patient)

Question 3

3. Factors affecting wear rates of hard-on-hard bearing surfaces (3)

Answer 3

• Surface roughness
• Sphericity (< 10 μm)
• Radial clearance (< 150 μm)

Question 4

4. Advantages of tantalum implants versus titanium (3)

Answer 4

• Modulus of elasticity closer to that of bone
• Better bony ingrowth
• Improved friction (better scratch fit)

Question 5

5. Options for reconstruction of bone defects (6)

Answer 5

• Cancellous autograft/allograft
• Structural bone graft
• Cement
• Metallic augments
• Cement with raft screws
• Metallic endoprostheses

Question 6

6. Modes of polyethylene wear

Answer 6

• Mode 1: wear between bearing surfaces (abrasive, adhesive)
• Mode 2: wear between bearing surface and non-bearing part of implant (ex. head on acetabular shell)
• Mode 3: third body wear
• Mode 4: wear between non-bearing surfaces (backside wear)

Question 7

7. Effects of polyethylene cross-linking (8)

Answer 7

• Improved wear characteristics
• Decreased resistance to fatigue/fracture
• Decreased elastic modulus
• Decreased tensile strength
• Decreased ductility
• Decreased yield strength
• Decrease wear particle size
• Decreased number of wear particles

Question 8

8. Order of decreasing Young’s modulus in tissues (highest [stiffest] to lowest) (10)

Answer 8

• Ceramic
• Cobalt chrome
• Staineless steel
• Titanium
• Cortical bone
• PMMA
• Polyethylene
• Cancellous bone
• Tendon/Ligament
• Cartilage
• (“Sir (cer), CoST Could Push Polly to CANCEL her TeLephone CARrier”)

Question 9

9. Methods of polyethylene sterilization (4)

Answer 9

• Gas plasma
• Ethylene oxide
• Low-/high-dose radiation
• Radiation in air vs. inert gas

Question 10

10. Types of corrosion (4)

Answer 10

• Galvanic
• Crevice
• Stress
• Fretting

Question 11

11. Methods of polyethylene manufacturing (4)

Answer 11

• Ram bar extrusion with machining
• Hot isostatic pressing with machining
• Compression molding with machining
• Direct compression molding (best

Question 12

12. Types of lubrication (6)

Answer 12

• Elastohydrodynamic
• Boundary (“slippery surfaces”)
• Boosted
• Hydrodynamic (fluid film)
• Weeping
• Mixed

Question 13

13. Factors affecting hydrodynamic lubrication (7)

Answer 13

• Material (high carbon content better)
• Bearing surface roughness
• Sphericity
• Head size
• Radial clearance
• Fluid viscosity
• Angular velocity

Question 14

14. Coefficients of friction (increasing order) (6)

Answer 14

• Articular cartilage (0.002 – 0.04)
• Ceramic-on-ceramic
• Metal-on-metal
• Metal-on-polyethylene (0.05 – 0.15)
• Ice-on-ice (0.1)
• Steel-on-steel (0.6 – 0.8)
• (A.C.M.M.I.S.)

Question 15

15. Components of current (4th generation) cementing techniques (8)

Answer 15

• Canal preparation
• Cement restrictor
• Antibiotic-loaded
• Low-viscosity
• Vacuum mixing
• Gun insertion
• Pressurization
• Stem centralizer
• (Start → finish)

Question 16

16. Methods to improve success of biologic fixation (8)

Answer 16

• Viable bone (absolute MUST)
• Cortical bone seating
• Porosity (pores 50-150 μm over 50% of implant)
• Deeper pores
• Increased surface roughness
• Surface coating (hydroxyapatite – Ca10(PO4)6(OH)2)
• Minimal gaps (< 50 μm)
• Minimal motion (< 150 μm)
• (Bone, implant, interface)

Question 17

17. Differential diagnosis of a painful TKA (8)

Answer 17

• Extrinsic
  o Referred pain
  o CRPS
• Intrinsic
  o Infection
  o Instability
  o Impingement
  o Loosening/osteolysis
  o Malpositioning/malalignment
  o Patellar clunk syndrome

Question 18

18. Causes of patella baja in a native knee (4)

Answer 18

• Trauma
• Idiopathic
• Lateral closing wedge HTO
• Tibial tubercle osteotomy
• (T.I.L.T.)

Question 19

19. Risk factors for anterior polyethylene post wear (4)

Answer 19

• Femoral component flexion
• Excess posterior tibial slope
• Anterior translation of tibial component
• Knee hyperextension
• (F.E.A.K.)

Question 20

20. Indications for takedown of a hip fusion (4)

Answer 20

• Painful pseudarthrosis
• Malposition limiting function
• To allow ipsilateral TKA
• Disabling ipsilateral knee pain/contralateral hip pain/back pain

Question 21

21. Radiographic definitions of developmental dysplasia of the hip (3)

Answer 21

• Lateral centre-edge angle < 20° (Wiberg angle)
• Anterior centre-edge angle < 20° (Lequesne angle)
• Acetabular index > 5° (Tonnis angle)

Question 22

Classification of adult developmental dysplasia of the hip (Crowe) (4)

Answer 22

• Based on the % proximal migration of the head-neck junction compared to normal femoral head height (or 20% of pelvic height)
  o I: < 50%
  o II: 50-75%
  o III: 75-100%
  o IV: > 100%