L22 Implantable Prostheses

Question 1

Implants

Answer 1

• Implants: devices or tissues that are placed inside or on the surface of the
  body
• Many implants:  prostheses – replace missing body part
• Other implants: deliver medication, monitor body functions or provide support to organs and tissues

Question 2

Implant Considerations

Answer 2

• Permanent (joints, stents) or removable (chemo ports, screws for broken bone repair)
• Materials (skin, bone, body tissues, metal, plastic, ceramic) -> allergies, rejection
• Surgical procedure to insert -> infections, bruising, pain, swelling,
• Biocompability: ability of material to perform as it interacts with human body; should not produce a toxic or immunological response
• Tissue engineering, scar formation
• Failure rate (strength of material, design) –repair or replacement of implant procedures
• Degradation
• Benefits vs. risks

Question 3

Design of Implants

Answer 3

Anatomy of organ
* Structure
* Function

Pathology of organ
* Description of different problems, lesions
* Selection of patient population

Old and new solutions
* Past and present approaches to solving problem
* Best current approach
* Problems with “gold” standard

New design
* Visualization
* Space and cost constraints
* Safety and efficacy
* Risk/benefit analysis

Question 4

Joint Replacement Prostheses

Answer 4

Fit
* Anatomy: ability to manufacture size, shape
Function
* Kinematics
* Range of Motion

Fixation
* Designs with irregular surfaces for bone integration
* Bone cement
* Porosity
* Ca- containing coating

Tribology
* Friction
* Wear – smooth and wear resistant surface
* Lubrication – lubricated for low friction

Other effects
* Stress shielding – lower modulus of elasticity

Question 5

Spinal Implants

Answer 5

Fusion:
* often with a bone graft
* Cages/interbody cages – between two vertebras; porous walls to
graft will grow into them
* Plates – support to cervical spine, flexible, secured with screws
* Rods – strong and flexible, hooks or pedicle screws

Non-fusion:
* artificial disks
* expandable rods (scoliosis)
* stimulation devices

Question 6

Heart Valve Repair or Replacement

Answer 6

• Repaired using a ring to support the damaged valve
• Entire valve removed and replaced with an artificial valve: carbon coated plastic or tissue made from animal valves

Question 7

Other Implants

Answer 7

• Dental
• Breast
• Cochlear
• Eye lens