Acetabluar Component Loosening

Description: Wheeless Textbook of Orthopaedics (THR) - Loosening of Uncemented Acetabular Components: (press fit acetabular components) - normal bone ingrowth: - generally for bone ingrowth to occur, the component must lie with 50 micrometers of the acetabulum, inorder for host bone ingrowht to occur; - as noted by RD Bloebaum et al 1997, bone ingrowth into component averages only 12%, eventhough 84% of the cup surface was in contact w/ periprosthetic bone; - bone ingrowth was found to be uniform in all zones, most likely due to the uniform distribution of stresses from the metal backing; - radiographic signs of loosening: (see radiographic techniques for eval of acetabulum) - radiolucent lines that initially appeared after two years - progression of radiolucent lines after two years - radiolucent lines in all three zones - radiolucent lines 2 mm or wider in any zone - migration - loosening is present w/ more than 2 mm of migration (either horizontal or vertical); - continuous radiolucent line; - note that peripheral radiolucent lines which are non-continuous are commonly found in press fit acetabular components and are often not progressive; - of note, postoperative gaps are net necessarily associated with subsequent presence of radiolucent lines, progressive radiolucent lines, or socket-loosening;