Poly wear

 

Lucent Zones                         

 

Femur:  Gruen Zones

 

AP 1-7

Zone 1:   Greater trochanter

Zone 4:   Tip

Zone 7:   Lesser trochanter

 

Lateral 8-14

Zone 8:   Anterior-superior

Zone 11: Tip

Zone 14: Posterior-superior

 

Acetabulum: Charnley Zones

 

Zone 1:  Superior 1/3

Zone 2:  Middle 1/3

Zone 3:  Inferior 1/3

 

Loosening

 

Concepts

 

1.  Easier to identify loosening in femur than acetabulum

- femur 90% accuracy

- acetabulum 65% accuracy

 

2.  More difficult to identify in uncemented prosthesis

 

3.  Lucent lines don't necessarily represent problem

- may be present in well-fixed prosthesis (retrieval studies)

- Often due to remodelling

 

Cemented Femur

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