title: Three-dimensional measurement of cemented femoral stem stability: an in vitro cadaver study.
abstract: OBJECTIVE
  To compare the in vitro stability of two cemented hip stem designs: Stem I was a collarless, double-tapered, highly polished implant; Stem II had a collar and matt finish.
  
  
  BACKGROUND
  Stability of the femoral component of a hip implant is important for its long-term clinical success. Excessive migration or cyclic motion can increase the risk of early implant failure.
  
  
  METHODS
  The stems were implanted in paired human cadaver femurs, and custom-designed micromotion sensors were used to measure three-dimensional motions of the stems at proximal, middle and distal locations during simulated in vivo loading cycles.
  
  
  RESULTS
  This study found that despite 'rigid' fixation, cemented stems exhibit detectable motions under a limited number of cycles of simulated physiologic loads. At four times the donor body weight, Stem I showed a subsidence of 90 microm, compared to 25 microm of Stem II (P<0.05). In contrast, the proximal end of Stem II exhibited greater cyclic motions in the medial-lateral direction (P<0.05).
  
  
  CONCLUSIONS
  The different motion patterns could be due to the design differences, such as surface finish and geometry. RelevanceImplant design is an important factor related to the behavior of the cement/bone interface and the overall success of the implant. This study compares in vitro micromotion of two cemented femoral prostheses with differing proximal designs.
authors.affiliation: M.E. Muller Institute for Biomechanics, University of Bern, P.O. Box 30, Murtenstrasse 35, CH-3010, Bern, Switzerland.
authors.forename: A D
authors.initials: AD
authors.lastname: Speirs
authors.forename: M A
authors.initials: MA
authors.lastname: Slomczykowski
authors.forename: T E
authors.initials: TE
authors.lastname: Orr
authors.forename: K
authors.initials: K
authors.lastname: Siebenrock
authors.forename: L P
authors.initials: LP
authors.lastname: Nolte
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002484:Cementation; D005269:Femur; D006622:Hip Prosthesis; D006801:Humans; D066298:In Vitro Techniques; D008875:Middle Aged; D009038:Motion; D011474:Prosthesis Design; D011475:Prosthesis Failure