Definition

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

 

Polyethylene

PMMA

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

- TNF

- aggregates more macrophages

- release TNF, IL1, IL6, PGE2

- stimulated osteoclastic bone resorption

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