Old exams Flashcards
Define stress shielding:
Effect resulting in decreased density of bone as a consequence of load sharing between an implant and tissue
Define osteolysis and effect on loosening of hip joint:
Cellularly mediated bone loss, secondary to debris production and/or release by implants in or near the bone
Rank the following with respect to stress-shielding:
Aluminia Porous tantalum alpha-Ti alloys beta-Ti alloys CoCr
Alpha-Ti alloys Beta-Ti alloys Porous tantalum CoCr Aluminia
A titanium plasma sprayed cementless stem in total hip arthroplasty..
a) Has generally a clinical success rate of 85% after 10 years
b) Has preferably a non-circumferential titanium coating
c) Has an initial press fit by mechanical fixation
d) Has preferably a cylindrical, not dual tapered design
c) Has an initial press fit by mechanical fixation
List all the components of a total knee replacement:
- Femoral condyle
- Tibial component
- Tibial spacer
- Patella component
Total knee replacement: What biomaterials can be used for the femoral condyle?
CoCr alloys
ceramic biomaterials (AL_2O_3, ZrO_2)
Oxidized Zr-Nb alloy (Oxinium)
Total knee replacement: What biomaterials can be used for the tibial component?
CoCr (for cemented implants) Ti alloys (for cementless implants)
Total knee replacement: What biomaterials can be used for the tibial spacer?
Ultrahigh molecular weight polyethylene (UHMWPE)
Total knee replacement: What biomaterials can be used for the patella component?
UHMWPE ceramic biomaterials (AL_2O_3, ZrO_2)
the presence of an implanted device increases susceptibility to infection because:
a) The infecting bacteria can use (parts of) the implant for their nutrition
b) Antibiotics bind to the implant surface, and therefore do not reach the bacteria
c) The biomaterial surface can be colonized by bacteria in so called biofilm
d) The immune cells in tissue around an implant have reduced capability to kill bacteria
C and D
Total hip replacement: List biomaterials that may be used for the Acetabular cup
- Titanium fibre mesh
- Aluminia
- Porous tantalum
- Cocr
Total hip replacement: List biomaterials that may be used for the Liner
UHMWPE
Total hip replacement: List biomaterials that may be used for the Femoral head
Zirconia, Oxinium
Total hip replacement: List biomaterials that may be used for the Femoral stem
Stainless steel, CoCr, Titanium
Name a material commonly used as bone cement
PMMA
Classify Total Joint Replacements to the FDA criteria (class I, II, III device)
Class III, because it is an orthopedic implant
Implants increase infection susceptibility to infectin because…
a) Bacteria can use (part of) the implant for nutrition
b) Antibiotics bind to the implant surface and therefore do not reach the bacteria
c) The biomaterial surface can be colonized by bacteria in a so called biofilm
d) Immune cells in tissue around the implant have reduced capability to kill bacteria
C and D
Choose from below material and make a fixation plate for a multiple-fractured partially shattered femur
a) PMMA
b) Zirconia
c) Stainless steel
d) Ti6Al4V
C. The fix is temporary and doesn’t need bone in-growth
What are the three components of the Tissue Engineering Triad in the Standard Model?
a) Cells, mechanical stimuli and surgical intervention
b) Biomaterials, autologous tissue and drug delivery
c) Drug delivery, Autologous cell and an animal model
d) Cells, scaffolds and bioactives
D
Which of the following has the best osteointegrative properties?
a) Stainless steel
b) Porous Ti
c) Al2O3
d) CoCrMo
e) PMMA
B
Osteoblasts function is described by:
a) Removal of bone tissue
b) Forming of cartilage
c) Forming bone tissue
d) Biofilm formation
C
Implant loosening is caused by (among other causes) stress shielding and osteolysis: Define both terms:
Stress shielding: Effect resulting in a decreased density of bone as a consequence of load sharing between an implant and tissue
Osteolysis: Cellularly mediated bone loss, secondary to debris production and/or release by implants in or near the bone
Implant loosening is caused by (among other causes) stress shielding and osteolysis: Which material properties are important to reduce the influence of both contributions?
Elastic modulus
Implant loosening is caused by (among other causes) stress shielding and osteolysis: Rank the materials with respect to stress shielding effect:
Aluminium
Titanium-alloys
Cobalt-chromium alloys
Best -> worst:
Titanium-alloys - Cobalt-chromium alloys - Aluminium
Indicate which letter belong to which number:
A: PMMA 1. Affected by gamma sterilization
B: Ca10(PO4)6(OH)2 2. is used as cement
C: Tantalum 3. Has positive osteointegrative properties
D: UHMWPE 4. Is a biodegradable material
E: Mg 5. Is also called trabecular bone
A-2 B-5 C-3 D-1 E-4
Tissue engineered implants primarily doesn’t survive because of…
a) surgically caused tissue damage
b) Poor nutrient delivery & waste removal by insufficient vascularization
c) Poor cell survival “in vitro”
d) Insufficient mechanical stimulation prior to implantation
B
Which of the following coupling in Total Hip Replacement will generate the smallest volume and finest wear particles?
a) CoCr - UHMFWP
b) CoCr - CoCr
A
Describe the three classes defined by the FDA criterias:
class I: Minimum invasiveness, well-established safety and effectiveness class II: Higher degree of invasiveness but not long durations class III: Highest degree of invasiveness, life-sustaining/supporting, high risk of illness or injury
You see an image of a Total Hip Replacement, with an acetabular cup with an emptiness around the fixture surface, and an X-ray of decreasing bone close to an hip implant stem. Identify the failure
Looseing of the cup, as a result of osteolysis
Describe the cemented and the cementless procedure in Total Hip Replacements. Which would you choose for a 30 year old patient and which would you choose for a 70 year old patient?
Cemented for the 70 year old, cementless for the 30 year old.
Because: For some people, an uncemented prosthesis can last longer than cemented replacements cause there is no cement that can break away. And, if the patient needs an additional hip replacement (likely for such a young person) the second surgery is sometimes easier if the person has an uncemented prosthesis.
The primary disadvantage of an uncemented prosthesis is the extended recovery period - Takes a long time for the natural bone to grow and attach to the prosthesis. People with uncemented must limit activities up to 3 months after surgery. The natural bone growth may also cause much pain, but for a 30 year old it is probably worth the time.
What is the main damage mode of a tibial spacer?
Delamination wear of the UHMWPE biomaterial under cyclic loading. This could be the effect of oxidative degradation of the biomaterial following sterilization of the component by gamma radiation.
Where is the main source of in vivo wear debris generation for a monolithic hip femoral stem which belongs to a cemented total hip replacement?
- The interface between the CoCr femoral head and acetabular cup liner
- The interface between the implant and the bone cement
Where is the main source of in vivo wear debris generation for a modular titanium hip stem which belongs to a cementless total hip replacement?
- The interface between the CoCr head and acetabular cup liner
- the interface between the CoCr head and the neck of the stem
