Week 8 - Implant Reaction

Question 1

sequence of events for implant reaction

Answer 1

1. implantation
2. blood-biomaterial interactions
3. provisional matrix formation
4. acute inflammation
5. chronic inflammation
6. granulation tissue
7. foreign body reaction
8. fibrosis/ fibrous capsule development

Question 2

step 1

Answer 2

IMPLANTATION

Question 3

step 2

Answer 3

BLOOD-BIOMATERIAL INTERACTIONS

Question 4

what forms: PROVISIONAL MATRIX FORMATION

Answer 4

STEP 3
- forms within mins-hrs of implantation
- fibrin ( blood coagulating protein-
produced from fibrinogen)
- inflammatory products (released by complement system)
- activated blood platelets
- inflammatory cells
- endothelial cells

Question 5

what happens: ACUTE INFLAMMATION

Answer 5

STEP 4

• neutrophils arrive in vast numbers
• do a lightning immunological assault
• short duration (mins-days)

Question 6

main features: ACUTE INFLAMMATION

Answer 6

• release of fluid and blood plasma proteins
• arrival of leukocytes (initially neutrophils, later macrophages)
• resolves in a week –> longer = infection

Question 7

role of leukocytes: ACUTE INFLAMMATION

Answer 7

• adsorb to biomaterial
• frustrated phagocytosis
• -> particulate biomaterials/ wear debris, phagocytosis is successful

Question 8

draw the graph

Answer 8

how do i insert a photo?

Question 9

cell mediators: role and examples

Answer 9

chemicals released by damaged cells that have a role in stimulating the inflammatory response

• histamine
• prostoglandins
• leukotrienes
• kinins
• complement

Question 10

what happens: CHRONIC INFLAMMATION

Answer 10

STEP 5

• macrophages (monocytes and lymphocytes) arrive –> DEFINING FEATURE
• proliferation of blood vessels and connective tissue
• less uniform histologically than acute
• long term presence of lymphocytes and monocytes may indicated long-standing infection

Question 11

what happens: GRANULATION TISSUE

Answer 11

STEP 6

• fibroblasts and endothelial cells arrive and healing begins
• scar tissue begins to form

Question 12

initiation: GRANULATION TISSUE

Answer 12

• 1 day post implant

- by action of monocytes and macrophages

Question 13

key features: GRANULATION TISSUE

Answer 13

• proliferation of small blood vessels –> neo-vasculatisation. angiogenesis –> proliferation, maturation and organisation of endothelial cells into capillaries
• proliferation of fibroblasts –> activley synthesise collagen and proteoglycans of CT
• macrophages present but not dominant

Question 14

purpose of INFLAMMATION

Answer 14

• contain, neutralise, dilute or wall (ward) off injurious agent or process, setting off regenerative process

Question 15

what happens: FOREIGN BODY REACTION

Answer 15

STEP 7
macrophages form giant cells
- multinuclear macrophages
- components of granulation tissue

Question 16

examples: FOREIGN BODY RESPONSE

Answer 16

• silicon breast implant –> FBR 1-2 macrophage cells in thickness
• dacron vascular implant –> FBR individual macrophages and FBGC’s

Question 17

what happens: FIBROSIS

Answer 17

fibrotic capsule development

• immune system cannot kill or remove implant it incapsulates it
• fibroblasts creating CT capsule to isolate implant
• esp. for non-porous implants
• applies to biocompatible and bioinert materials

Question 18

exceptions: FIBROSIS

Answer 18

• porous biocompatible/ bioactive –> infuse with CT
• nonporous bioactive –> interfaces with normal CT
• biodegradable –> metabolised away
• toxic –> prolonged complications and cell death

Question 19

minimising: FIBROSIS

Answer 19

• more biocompatibl/ bioinert
• less movement
• leaching toxins = thicker capsule
• bioactive coatings (HA) = eliminated capsule