title: Porous titanium particles for acetabular reconstruction in total hip replacement show extensive bony armoring after 15 weeks. A loaded in vivo study in 10 goats.
abstract: OBJECTIVE
  The bone impaction grafting technique restores bone defects in total hip replacement. Porous titanium particles (TiPs) are deformable, like bone particles, and offer better primary stability. We addressed the following questions in this animal study: are impacted TiPs osteoconductive under loaded conditions; do released micro-particles accelerate wear; and are systemic titanium blood levels elevated after implantation of TiPs?
  
  
  METHODS
  An AAOS type-III defect was created in the right acetabulum of 10 goats weighing 63 (SD 6) kg, and reconstructed with calcium phosphate-coated TiPs and a cemented polyethylene cup. A stem with a cobalt chrome head was cemented in the femur. The goats were killed after 15 weeks. Blood samples were taken pre- and postoperatively.
  
  
  RESULTS
  The TiP-graft layer measured 5.6 (SD 0.8) mm with a mean bone ingrowth distance of 2.8 (SD 0.8) mm. Cement penetrated 0.9 (0.3-1.9) mm into the TiPs. 1 reconstruction showed minimal cement penetration (0.3 mm) and failed at the cement-TiP interface. There were no signs of accelerated wear, metallic particle debris, or osteolysis. Median systemic titanium concentrations increased on a log-linear scale from 0.5 (0.3-1.1) parts per billion (ppb) to 0.9 (0.5-2.8) ppb (p=0.01).
  
  
  CONCLUSIONS
  Adequate cement pressurization is advocated for impaction grafting with TiPs. After implantation, calcium phosphate-coated TiPs were osteoconductive under loaded conditions and caused an increase in systemic titanium concentrations. However, absolute levels remained low. There were no signs of accelerated wear. A clinical pilot study should be performed to prove that application in humans is safe in the long term.
authors.affiliation: Department of Orthopaedics, Radboud University Medical Centre, Nijmegen.
authors.forename: Lucas H B
authors.initials: LH
authors.lastname: Walschot
authors.forename: René
authors.initials: R
authors.lastname: Aquarius
authors.forename: Nico
authors.initials: N
authors.lastname: Verdonschot
authors.forename: Pieter
authors.initials: P
authors.lastname: Buma
authors.forename: B Willem
authors.initials: BW
authors.lastname: Schreurs
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000818:Animals; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D016025:Bone Transplantation / Q000009:adverse effects / Q000379:methods; D002130:Calcium Phosphates / Q000494:pharmacology; D002484:Cementation / Q000379:methods; D020099:Coated Materials, Biocompatible / Q000494:pharmacology; D004195:Disease Models, Animal; D006041:Goats; D006622:Hip Prosthesis / Q000009:adverse effects*; D008422:Materials Testing; D010014:Osteolysis / Q000209:etiology*; D020959:Polyethylene / Q000494:pharmacology; D016062:Porosity; D011475:Prosthesis Failure / Q000009:adverse effects*; D019651:Plastic Surgery Procedures / Q000009:adverse effects; D014025:Titanium / Q000009:adverse effects* / Q000097:blood
chemical_list: D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; D020959:Polyethylene; C020243:calcium phosphate; D014025:Titanium