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Online ISSN 1827-1707
CURRENT TRENDS AND CONTROVERSIES IN HIP DISORDERS - PART I
Chen D., Lin S., Cutrera N., Padgett D., Wright T.
Hospital for Special Surgery, New York, NY, USA
Ceramic femoral heads were introduced into total hip arthroplasty for their high elastic modulus and hardness, high wettability, low friction, and excellent scratch resistance. However, a common problem observed on retrieved ceramic heads is the appearance of metallic debris transferred on to the bearing surface. The objectives of this study were to investigate the location and extent of metal transfer on retrieved implants and to determine factors which may be associated with this occurrence. Sixty-eight ceramic hip retrievals were examined, and patient demographic information on all 68 cases was collected. The surface of each ceramic head was assessed for metal transfer using a subjective grading system. Non-contact white-light profilometry was used to characterize surface roughness of the apex, below the equator, and in regions of metal transfer; 87% of the ceramic heads displayed metal transfer with an average grade of 2.6. About 13% of the metal transfer occurred on the apex, 73% at the equator, and 14% below the equator. 35% of the examined retrievals were revised for osteolysis or loosening and 25% for dislocation or instability. Heads revised for device failure and osteolysis or loosening had significantly higher surface roughnesses than those revised for periprosthetic fracture and dislocation or instability. Surface roughness measured within the metal transfer was significantly higher than that measured within the apex and below the equator. Surface roughness was significantly correlated with subjective wear grade. Zirconia heads had significant higher surface roughness measurements within the apex and below the equator than alumina heads. These metallic regions, thought to be due to subluxation of the head and/or impingement with the metallic acetabular shell, cause increased surface roughness that likely creates higher wear rates of the articulating polyethylene acetabular inserts.