Biological response to particulate matter

- characterised by periprosthetic osteolysis

- stimulated by wear debris

- debris gains access to any area accessible by fluid


Sources of particulate debris


1.  Wear


Mechanisms of wear

A.  Adhesion

B.  Abrasion

C.  Fatigue


Modes of wear


1.  Motion between 2 surfaces designed for motion

2.  Primary bearing surface against an non intended bearing surface

- i.e. femoral head against acetabular shell when liner has worn out

3.  Interposed third body particles i.e. bone or cement

4.  Two non bearing surfaces together i.e. back sided fretting, morse taper fretting, screws


2.  Corrosion


Electrochemical process releasing metal ions

- modular interfaces i.e. head neck

- metal on metal bearings


Types of wear particles




Cobalt alloy

Titanium alloy


Morphology of wear particles


Usually less than 1um in size


Biological response to wear particles


Small particles phagocytosed by macrophages

- unable to digest

- stimulate release of cytotoxic factors


- aggregates more macrophages

- release TNF, IL1, IL6, PGE2

- stimulated osteoclastic bone resorption

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