Not all zirconia femoral heads degrade in vivo

Clin Orthop Relat Res. 2007 Dec;465:220-6. doi: 10.1097/BLO.0b013e318158b4d3.

Abstract

Degradation of yttria-stabilized zirconia femoral heads in vivo has been linked to increased roughening and even fracture of the femoral head. To determine whether magnesia-stabilized zirconia is better suited to resist degradation, we characterized the monoclinic phase concentration, surface topography, and microhardness of retrieved zirconia femoral heads. From previous work, we expected yttria-stabilized zirconia heads to undergo considerable tetragonal-to-monoclinic phase transformation in vivo, leading to considerably increased roughness and decreased microhardness, whereas magnesia-stabilized zirconia heads would not experience phase transformation and thus would not roughen or exhibit decreased microhardness. We studied seven yttria-stabilized zirconia and 12 magnesia-stabilized zirconia femoral heads. Yttria-stabilized zirconia heads explanted after 5 years exhibited a rough orange peel-like surface under light microscopy and were rougher than magnesia-stabilized zirconia heads (average roughness approximately 20 nm versus 7.5 nm, respectively), likely attributable to increased mono-clinic phase transformation (approximately 37% by weight) caused by low-temperature aging. The microhardness of yttria-stabilized zirconia heads decreased with age, but the relationship was not noteworthy. In contrast, magnesia-stabilized zirconia retrievals showed no change in monoclinic phase concentration, surface roughness, or microhardness with age. The properties of the yttria-stabilized zirconia evaluated in our study deteriorated in vivo, whereas magnesia-stabilized zirconia did not degrade and appears to be a superior biomaterial for bearing in total joint arthroplasty.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arthroplasty, Replacement, Hip / instrumentation*
  • Device Removal
  • Equipment Failure Analysis
  • Femur / surgery*
  • Hardness
  • Hip Prosthesis*
  • Humans
  • Magnesium Oxide / chemistry*
  • Prosthesis Design
  • Prosthesis Failure*
  • Reoperation
  • Surface Properties
  • Time Factors
  • Treatment Outcome
  • Yttrium / chemistry*
  • Zirconium / chemistry*

Substances

  • Magnesium Oxide
  • Yttrium
  • Zirconium
  • zirconium oxide
  • yttria