Mechanical and histological evaluation of hydroxyapatite-coated, titanium-coated and grit-blasted surfaces under weight-bearing conditions

Abstract

Cylindric titanium rods with different surfaces were axially implanted into the femora of sheep. The three surfaces were grit-blasted titanium, plasma-sprayed titanium and plasma-sprayed hydroxyapatite (HA). After 2 months, a 2-cm segment of the femoral shaft was completely resected to load the implant, and the animals were allowed full weight-bearing for 9 months. Biomechanical and histological evaluation of the implants was undertaken 2 months after implantation and 9 months after the segmental resection. The mechanical testings of well-fixed implants were performed 9 months after segmental resection. Loosening of 45% of the titanium-coated implants was observed in the first 3 weeks, but thereafter, no further loosening occurred. The HA-coated implants remained entirely fixed for 3 weeks, but thereafter, a progressively increasing incidence of loosening up to 55% after 9 months of loading was detected as subsidence on X-radiographs. The maximum push-out strength of the titanium-coated implants was 4.9 MPa compared with 2.3 MPa for HA-coated ones. No significant mechanical interlock between the grit-blasted surface and bone was observed. The HA coating was found to be delaminated in all unstable implants, whereas the titanium coating remained completely intact. Morphometric analyses of well-fixed rods showed complete bony ingrowth onto the HA surface, whereas the contact area between the bone and the two titanium surfaces was less than 40%. Concerning clinical significance bony ingrowth with long-term mechanical interlock between the implant surface and the bone cannot be achieved by grit-blasting or HA-coating.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanical and Histological Evaluation of Improved Grit-Blast Implant in Dogs: Pilot Study

“…Those fine-grit blast implants reported heretofore, however, had an average surface roughness of only 5.7 to 6.2 µm Ra [10,30] as compared to the present 33.4-µm roughness (Ra), and their maximum peak had a [10,30] as compared to the deep peak-to-valley contrasts in the present study. In sheep femora, a conventional grit blast implant having a roughness of 6.2 ± 0.9 µm Ra and a maximum peak of 43.5 ± 5.3 µm Ry was reported to result in complete failure in push-out tests [10]. Conversely, in our study, the surface roughening of the implant contributed vastly to favorable bone ongrowth to the implant, and this high rate of .…”

“…But, the fastness of such coatings is markedly reduced by fatigue, often ending in avulsion of the surface coating from the metallic substrate [16,31]. Uncoated grit blast implants, on the other hand, are notably weak in shear strength between the bone and implant [10,20,30]. Attempts to increase the roughness, or porosity, of the grit blast implants, have demonstrated that hydroxyapatite or A-W glass ceramic accelerated the vascularization and ossification within a short period after implantation [21,30].…”

“…Heretofore, in conventional grit blasted implants, the average surface roughness (Ra) has ranged from 5.7 µm to 6.2 µm with peaks (Ry) of 38.4-43.5 µm [10,30]. In the present work, we tested an improved grit blast titanium implant prepared with an average surface roughness of 33.4 µm and a wide contrast of 251.6 µm between the valleys and peaks, i.e., about ten times rougher than usual, designed with an especially bumpy surface of acutely articulated concavities, or craters.…”

Improved fixation of porous-coated versus grit-blasted surface texture of hydroxyapatite-coated implants in dogs

“…The experimental finding that HA coatings can delaminate from a grit-blasted surface might have clinical importance because retrievals have shown delamination of the HA coating and loosening of prosthetic components with grit-blasted surfaces (Collier et al 1993, Nilsson et al 1994, David et al 1995. However, the present study was performed in an unloaded model, which might affect findings from the mechanical test.…”

Fortifying the Bone-Implant Interface Part 1: An In Vitro Evaluation of 3D-Printed and TPS Porous Surfaces

“…For instance, plasma sprayed HA, the most common means to apply HA coatings, have been shown to delaminate from implants surfaces and to release particulates. 24,25 Further, plasma spraying is a line-of-site process that is unable to uniformly coat inner porous surface features. A recent option is to deliver HA in the form of nanoparticles, which may be beneficial in that HA is naturally found in this form.…”