Porous titanium particles for acetabular reconstruction in total hip replacement show extensive bony armoring after 15 weeks

Abstract

Background and purpose— 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?Animals and 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).Interpretation —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.

New biomaterials for orthopedic implants

“…Under loaded conditions, CaP-coated porous Ti particles have also been evaluated in goats to reconstruct AAOS type-III defects in the acetabulum. 199 By 4 weeks postimplantation, new bone was found to penetrate throughout the whole depth of the graft layer, both through the larger interparticle pores and through the smaller-sized intraparticle pores. No Ti microparticles or macrophageor osteoclast-induced osteolysis was observed.…”

The Biological Approach in Acetabular Revision Surgery: Impaction Bone Grafting and a Cemented Cup

“…Several other research groups have investigated the use of biomaterials in revision THA and some of them found successful results, even after a longer follow-up (24). We also investigated if titanium particles could be used in combination with bone chips for impaction, or even as a complete bone graft substitute in combination with a cemented cup (25–27). From a mechanical point of view these impacted titanium particles had a superior primary stability in synthetic acetabular models compared with bone particles (25).…”

“…Also, in a bone chamber model, incorporation of these impacted titanium chips was rapid, relatively complete and well predictable. Even in a realistic acetabular model and in vivo experiments in goats, the outcomes appeared promising (26, 27). However, before clinical application, more clinical research has to be performed.…”