Biomedical Engineering Final Exam with 100% correct answers 2024

What are the different types of fracture fixation devices? - answer-- Screws - Plates - Intramedullary Rods - External Fixators What does the stability of intramedullary rods depend on? - answer-- Mechanical properties of nail - Nail fit in IM space - Mechanical properties of locking screw/bolts What does the bending and torsional stiffness of intramedullary rods depend on? - answer-- Nail diameter - Nail slots What do stabilizing pins/anchors do? - answer--resist rotation -prox and distal ends stay put so displaces less fragments What are the advantages of external fixators? - answer-- Only technique that allows stability to be adapted preoperatively, intraoperatively, and postoperatively and - allows to treat soft tissue injuries while stabilizing complex fractures What are the limitations of external fixators? - answer-- Compromise of blood supply in fracture healing zone - Interfragmentary movement - Pin site infection - Creates stress risers in adjacent bone What is the most common reason for joint replacements? - answer-Arthritis - Osteoarthritis - Rheumatoid arthritis What are the most common types of joint replacements? - answer-Hips and Knees What are the two classifications of joint replacements? - answer-- Articular surface only - Articular surface and bone substructure What structural and functional characteristics must be considered when completing a joint replacement? - answer-- Provide normal range of motion while transmitting joint forces - Longevity (last lifetime of patient) - Biocompatibility What are the design challenges of joint replacements? - answer-- Biocompatibility - Hermeticity - Structural design - Delivery system - Power management - Detection - Wireless communication What is corrosion? How can you reduce it? - answer-Gradual degradation of materials by electrochemical attack - Can be reduced by surface oxide films - Sensitive to wear - Regeneration times vary by material What material has the fastest surface oxide film regeneration time? Which has the slowest? Do you want this to be fast or slow? - answer-Titanium = fastest Stainless Steel = slowest * want this to be fast What is surface modification? What does it improve? - answer-Performed on biomedical implants to improve: - Corrosion resistance - Wear resistance - Surface texture - Biocompatibility What are four common types of surface modification? - answer-- Laser treatment - chemical treatment - HA - add ceramic coating What are some causes of joint replacements? - answer-- Joint diseases (most common rheumatoid arthritis) - Long term wear (ex:osteoarthritis) - Bone fractures - Avascular necrosis - Acute injury Did the first artificial knee or hip replacement come first? - answer-Knee - 1890 hip- 1891 shoulder -1893 Implants improved due to... (5) - answer-- new, better quality materials - different fixation methods - advanced implant design - advance in properties and coatings - less invasive techniques What are the four classifications of hip replacements? what do they mean? - answer-- Hip arthroplasty → resurfacing the femoral head - Femoral stem → usually only for femoral head fractures in healthy bone (normally in elderly due to falls) - Cup arthroplasty → surface of the acetabulum - Total hip arthroplasty (THA) → both femoral head and acetabular cup What type of hip replacement is the most common? - answer-THA What is the area of greatest concern when determining which material to use in a hip replacement? - answer-Friction and wear - Healthy organic cartilage surfaces → surface friction close to 0 due to synovial fluid - Man-made bearing surfaces: friction 100X higher - Result in: - Accelerated wear over time - Induced inflammatory response in surrounding tissues What are metal-on-metal bearings for hip replacements? - answer-- First used in the 60's and 70's - Clinical results of polyethylene-on-metal proved superior - Not applied to many joints other than hip - Younger patients best candidates What were most failures with metal-on-metal bearings due to? - answer-- Poor metallurgy (quality of metal) - Poor manufacturing (led to pitting) - Implant design (loosening huge problem) What led to a resurgence of metal-on-metal bearings for hip replacements? - answer-Improved manufacturing techniques and metallurgy - Cobalt chromium alloyed provides superior hardness and wear resistance - Superior strength over PE - Superior toughness over ceramics (ceramics are more brittle, less tough, but prevent wear) What are some important factors to control when using metal-on-metal bearings for hip replacements? - answer-- Conformity between bearing surfaces - Smooth surface finish What are some of the metal degradation concerns for metal-on-metal hip replacements? - answer-- Still considerably higher than other bearing combinations - Metal ions are transported to distant locations in the body (buildup in kidney) - More wear seen with larger bearing diameter (resurfacing vs. THR) - Not recommended for patients with poorly functioning kidneys - May be an issue with pregnant women? - Osteolysis and loosening associated with wear debris What is the difference in bearing diameter between THR and resurfacing? - answer-- Resurfacing → larger diameter - THR → smaller diameter - b/c doesn't restrict ROM? What group is best suited for M-O-M hip replacements? - answer-younger patients b/c need strength and longevity What is the most commonly used bearing combination for joint replacements? - answer-Metal on polyethylene What is the most commonly used bearing combination for HIP joint replacements? - answer-M-O-M What are metal-on-polyethylene bearings for hip replacements? What 2 groups are considered? - answer--2 groups considered: - Relatively sedentary older adults - Younger adults performing activities involving repetitive impact - Decreased wear allows larger more stable bearing sizes - Greater susceptibility to fracture under extreme conditions What are ceramic bearings for hip replacements? - answer-- Dense ceramics used: alumina and zirconia - Greatest advantage over metals is wear resistance - Can be polished to very smooth surface and remain relatively scratch resistant - Brittleness makes them susceptible to fracture (patients with active lifestyle not good candidates) What group is best suited for ceramic hip replacements? - answer-younger and more sedentary What is a hip hemiarthroplasty? - answer-Only femoral head replaced - Common for femoral neck fractures - sometimes head and stem What is a THA? - answer-acetabular cup and femoral head are replaced Who was the father of the artificial hip? - answer-John Charnley from England What was the first THA made of? Why did is fail? - answer-stainless steel failed due to loosening (irregular contact btwn bone and implant b/c weren't using bone cement) What are the advantages to the current THA designs? - answer-- Inexpensive - Easy to fit into different sizes/shapes of bone - Allows for immediate weight bearing - Improved wear-resistance What are the disadvantages to the current THA designs? - answer-- Cement disintegrates with age --> loosening - 'Polyethylene disease' (osteolysis) from wear debris - decreases bone quality What is the purpose of bone cement? - answer--used to increase congruity btwn bone and implant -helps dissipate the forces more evenly -prevents rotation of stem in IM canal b/c acts as grout What are the advantages of the surface coatings used in hip replacements? - answer-- Encourage bone growth infiltration - Doesn't require use of bone cement - Provides stable and strong joint bonding - Fracture toughness maintained (metal) What was John Charnley's role in THA? - answer-- Sought to develop 'low friction' arthroplasty - 1st attempt: Teflon (resulted in rapid failure) - 2nd attempt: metal femoral head on acrylic stem, thick-walled Teflon cup (this design quickly failed due to poor wear characteristics) - 1960's: Birth of 'Total Hip Replacement' (HMWPE cup and metal femoral head) What are the limits to lifespan of hemiarthroplasty? - answer-- Aseptic loosening - Osteolysis - Led to COC (alumnia on zirconia designs) designs (1990's)