title: Results of hip resurfacing.
abstract: BACKGROUND
  The renewed popularity of resurfacing hip arthroplasty in the last 10 years has generated a remarkable quantity of scientific contributions based on mid- and short-term follow-up. More than one paper has reported a consistent early revision rate as a consequence of biological or biomechanical failure. Two major complications are commonly described with resurfacing implants: avascular necrosis and femoral-neck fracture. A close relationship between these two events has been suggested, but not firmly demonstrated, whereas cementing technique seems to be better understood as potential cause of failure.
  
  
  METHODS
  We performed an in vitro study in which four different resurfacing implants were evaluated with a simulated femoral head, two types of cement, (low and high viscosity) and two cementing techniques: direct (cement apposition directly on the femoral head) and indirect (cement poured into the femoral component).
  
  
  RESULTS
  High-viscosity cement showed homogeneous distribution over the entire femoral head. Low-viscosity cement showed a massive polar concentration with insufficient, if not absent, distribution in the equatorial zone.
  
  
  CONCLUSIONS
  Polar cement concentration could be a risk factor for early implant failure due to two effects on the femoral head: biological (excessive local exothermic reaction could cause osteocyte necrosis) and biomechanical (which could lead to uneven load distribution on the femoral head).
authors.affiliation: Ortopedia e Traumatologia, Ospedale Santo Spirito, Rome, Italy. francesco.falez@francescofalez.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Falez
authors.forename: Fabio
authors.initials: F
authors.lastname: Favetti
authors.forename: Filippo
authors.initials: F
authors.lastname: Casella
authors.forename: Matteo
authors.initials: M
authors.lastname: Papalia
authors.forename: Gabriele
authors.initials: G
authors.lastname: Panegrossi
mesh_terms: D000328:Adult; D019644:Arthroplasty, Replacement, Hip; D002484:Cementation; D005265:Femoral Neck Fractures / Q000209:etiology; D006622:Hip Prosthesis; D006801:Humans; D066298:In Vitro Techniques; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000209:etiology / Q000601:surgery; D010020:Osteonecrosis / Q000209:etiology; D011183:Postoperative Complications; D011475:Prosthesis Failure; D012086:Reoperation; D014947:Wounds and Injuries / Q000150:complications