Early Clinical Results with the Hydroxyapatite-Coated Porous Lsf Total Hip System

The implant material hydroxylapatite (HA) has been shown in numerous studies to be highly biocompatible and to osseointegrate well with existing bone; however, the molecular mechanisms at work behind this osseointegration remain largely unexplored. One possibility is that the implant, exposed to the patient's blood during surgery, adsorbs known cell adhesive proteins such as fibronectin and vitronectin from the serum. Osteoblast precursors could then adhere to these proteins through integrin-mediated mechanisms. In the present study, we have used a quantitative ELISA assay to test the hypothesis that hydroxylapatite will adsorb more fibronectin and vitronectin from serum than two commonly used hard-tissue materials, commercially pure titanium, and 316L stainless steel. We further used the ELISA, as well as a standard cell adhesion assay, to test the hypothesis that increased protein adsorption will lead to better binding of purified integrins alpha5beta1 and alpha(v)beta3 and osteoblast precursor cells to the HA than to the metals. Our results show that fibronectin, vitronectin, alpha5beta1, alpha(v)beta3, and osteoblast precursor cells do indeed bind better to HA than to the metals, suggesting that improved integrin-mediated cell binding may be one of the mechanisms leading to better clinical bone integration with HA-coated implants.

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Hydroxylapatite binds more serum proteins, purified integrins, and osteoblast precursor cells than titanium or steel

Kilpadi

Chang

Bellis

2001

J. Biomed. Mater. Res.

400

227

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Histological and mechanical comparison of hydroxyapatite‐coated cobalt‐chrome and titanium implants in the rabbit femur

Friedman

Bauer

Garg

et al. 1995

J of Applied Biomaterials

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The purpose of this study was to compare hydroxyapatite (HA)-coated titanium (Ti) and HA-coated cobalt-chrome (CoCr) implants in the distal femur of the rabbit by evaluating bone apposition and interfacial shear strength. Bilateral cylindrical implants with a plasma sprayed 50-microns thick HA coating were press-fit into the metaphyseal cancellous bone of the lateral femoral condyles in a transverse fashion, and the animals were sacrificed at 2, 4, and 8 weeks postimplantation. Mechanical strength of the interface between HA and bone was measured using the pushout method. For histologic analysis, the fractional linear extent of bone apposition was quantitated. No differences were found in the interfacial shear strength between the Ti and CoCr at any time period. The amount of bone apposition increased significantly at each time interval for both substrate metals, but there were no significant differences between the two substrates at any of the time periods studied. The HA-coated CoCr implants performed in a similar manner to the HA-coated Ti implants, both mechanically and histologically, suggesting that HA-coated CoCr implants deserve further study as a viable alternative to Ti for the biological fixation of total joint components in orthopaedic surgery.

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Morphologic variation in plasma‐sprayed hydroxyapatite‐bioactive glass composite coatings in Hank's solution

Lin

Liu

1994

J. Biomed. Mater. Res.

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Pure hydroxyapatite (HA), pure bioactive glass (BG), and a new series of (HA/BG) composite coatings were plasma-sprayed onto a commercial Ti6A14V substrate. Changes in morphology and phases of these coatings after immersion in Hank's physiologic solution were investigated using XRD and SEM. Results indicated that the as-sprayed BG coating has an essentially amorphous structure with a very rough surface. After 7 days of immersion, the BG surface started to dissolve, and weak XRD peaks of apatite started to develop. Small amounts of CaO, beta-TCP, Ca4P2O5, as well as a glassy film, were found on the as-sprayed pure HA surface, most of which dissolved in 7 days. The XRD intensity of apatite in pure HA slowly increased with immersion time until, on the 10th day, the intensity started to drop, and 10 days later, the intensity rose again. This undiscovered "drop and rise" phenomenon was observed for the HA/BG composite coatings in an even more dramatic way. The presence of HA accelerates the dissolution of bioactive glass.

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Early Clinical Results with the Hydroxyapatite-Coated Porous Lsf Total Hip System

Cited by 11 publications

References 22 publications

Hydroxylapatite binds more serum proteins, purified integrins, and osteoblast precursor cells than titanium or steel

Hydroxylapatite binds more serum proteins, purified integrins, and osteoblast precursor cells than titanium or steel

Histological and mechanical comparison of hydroxyapatite‐coated cobalt‐chrome and titanium implants in the rabbit femur

Morphologic variation in plasma‐sprayed hydroxyapatite‐bioactive glass composite coatings in Hank's solution

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