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