An in vivo evaluation of bone response to three implant surfaces using a rabbit intramedullary rod model.

Our study was designed to evaluate osseointegration among implants with three surface treatments: plasma-sprayed titanium (P), plasma-sprayed titanium with hydroxyapatite (PHA), and chemical-textured titanium with hydroxyapatite (CHA). Average surface roughness (Ra) was 27 microns for the P group, 17 microns for the PHA group, and 26 microns for the CHA group. Bilateral distal intramedullary implants were placed in the femora of thirty rabbits. Histomorphometry of scanning electron microscopy images was used to analyze the amount of bone around the implants at 6 and 12 weeks after implantation. Greater amounts of osseointegration were observed in the hydroxyapatite-coated groups than in the noncoated group. For all implant surfaces, osseointegration was greater at the diaphyseal level compared to the metaphyseal level. No significant differences were seen in osseointegration between the 6 and 12 week time points. Although the average surface roughness of the P and the CHA groups was similar, osseointegration of the CHA implants was significantly greater. The results of this in vivo lapine study suggest that the presence of an hydroxyapatite coating enhances osseointegration despite similarities in average surface roughness.

Effects of hydroxyapatite on titanium foam as a bone ingrowth surface in acetabular shells: a canine study.

This study investigated a highly porous titanium foam with and without a PeriApetite coating as an alternative surface for implant fixation. Twelve mongrel canines received staged total hip replacements under International Animal Care and Use Committee (IACUC) approval from our institution. Animals were randomly placed in three- or six-month groups for sacrifice. Seventeen total hips were available for evaluation. The area and depth of ingrowth was measured by SEM. At three months, PeriApetite Ti foam had 37% more depth and almost 10% more bone ingrowth. Both groups were found not to be different at the six-month mark with over 36% of ingrowth calculated on SEM. The results prove not only that titanium foam is a viable ingrowth surface but also that PA coating can enhance the time to bony incorporation.

Bone response to a novel highly porous surface in a canine implantable chamber.

Long-term survival of uncemented hip components is dependent upon successful biological fixation. This study examined a new prosthetic surface treatment consisting of a highly porous open structure of commercially pure titanium, Tritanium Dimensionalized Metal; its overall porosity is approximately 65-70%. With the use of an implantable chamber in dogs, the effects of this treatment on bone ingrowth and strength of attachment were compared to both titanium (overall porosity of 30-35%) and cobalt chrome beads (overall porosity of 35-40%), with and without hydroxyapatite coating. At 6 and 12 weeks, chambers were explanted and specimens underwent high-resolution radiographic imaging and mechanical testing. At 12 weeks, Tritanium surfaces had greater bone penetration and tensile strength than remaining surface types. Over 40% of the Tritanium specimens had a tensile strength greater than 500 N, exceeding the testing capability of the servohydraulic equipment. The highly porous Tritanium surfaces allow for a far greater amount of bone ingrowth than beaded surfaces, and may create a geometry that enhances mechanical strength. Tritanium Dimensionalized Metal surface treatment may result in a clinically valuable implant fixation surface to induce rapid ingrowth and a strong bone-implant interface, contributing to increased implant survivorship.