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Response to Implantation

Response to Implantation. The implantation/injection/insertion of any device into the body will evoke a host tissue response to the injury. OBJECTIVES to provide an overview of the body’s normal response to an injury to overview the body response to the implantation of a device.

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Response to Implantation

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  1. Response to Implantation The implantation/injection/insertion of any device into the body will evoke a host tissue response to the injury. OBJECTIVES • to provide an overview of the body’s normal response to an injury • to overview the body response to the implantation of a device CHEE 340

  2. Normal Wound Healing • wound healing is a dynamic cascade of events initiated by injury • it may be divided into phases characterized by both cellular population and cellular function • blood clotting • inflammation • cellular invasion and remodeling • before reviewing wound healing, it is necessary to introduce some of the main players • cells of the blood stream • fibroblasts CHEE 340

  3. Fibroblasts CHEE 340

  4. Intravascular Cells CHEE 340

  5. Intravascular Cells • red blood cells erythrocytes, thrombocytes CHEE 340

  6. Clotting or Thrombosis • blood coagulation or clotting is the blood response to damaged blood vessels • objective is to form a patch that isolates the leak and stops blood loss CHEE 340

  7. Coagulation Pathways CHEE 340

  8. Inflammation • Inflammation is the reaction of vascularized tissue to local injury. • ACUTE INFLAMMATION • implantation causes disruption of microvasculature • initial response is vasodilation and increased permeabilty of capillaries • fluid and proteins and leukocytes exude into injured tissue (extravasation) • CHRONIC INFLAMMATION • characterized by the presence of macrophages, monocytes, and lymphocytes with the proliferation of blood vessels and connective tissue CHEE 340

  9. Leukocyte Invasion at Wound Site CHEE 340

  10. Granulation Tissue Deposition - Remodeling • Due to death of cells following injury, and their removal, there is a local decreased tissue mass • fibroblasts and vascular endothelial cells are recruited to site • Begin to form granulation tissue (ECM and new blood vessels) CHEE 340

  11. Wound Healing CHEE 340

  12. Foreign Body Reaction • The presence of the implant changes the healing response, and this is called the Foreign Body Reaction. • FBR consists of: • macrophages • multinucleated foreign body giant cells • form upon coalescence of macrophages • fibroblasts • capillaries CHEE 340

  13. Fibrosis and Fibrous Encapsulation • End stage of healing response • Usually four or more weeks after implantation • A relatively acellular fibrous capsule • spindle shaped fibroblasts • small number of macrophages • Presence of neutrophils suggests persisting inflammatory challenge • Presence of foreign body giant cell suggests production of small particles by corrosion, depolymerization, dissolution or wear CHEE 340

  14. Foreign Body Response - Resolution • continuing presence of an implant may result in the attainment of a final steady-state condition called resolution • there are 3 possible outcomes for the implant : • resorption • integration • encapsulation (fibrosis) CHEE 340

  15. Cell Regeneration After Injury • Possible outcomes for the injured tissue: • replacement of injured tissue with parenchymal cells of the same type • replacement by connective tissue that constitutes the fibrous capsule • The regeneration of cells in the body is tightly controlled • There are essentially 3 categories of cell populations • Renewing or labile • Expanding or stable • Static or permanent CHEE 340

  16. Fibrosis and Fibrous Encapsulation • 78-week PMMA histology (sheep): illustrates soft tissue encapsulation of prepolymerized PMMA CHEE 340

  17. Experimental Results 50:50 CL:LA 18 000 g/mol sterilized with 25kGy rat femur CHEE 340

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