Implant Pushout and Pullout Tests

Berzins, Aivars; Sumner, Dale R.

doi:10.1201/9781420073560.ch29

Cited by 17 publications

(16 citation statements)

References 18 publications

(25 reference statements)

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“…The forces that are measured by biomechanical pullout testing arise from the new bone in contact with the implant (BIC) as well as the bone in between the implant threads (peri-implant bone). Therefore, the three parameters of ultimate force, stiffness and work to failure that are generated from biomechanical testing, provide information about the mineralized tissue in the BIC and/or peri-implant bone [62]. Ultimate force is a measure of the failure of the mineralized tissue within the threads and is therefore dominated by the peri-implant bone.…”

Section: Discussionmentioning

confidence: 99%

Surface contaminants inhibit osseointegration in a novel murine model

Bonsignore

Colbrunn

Tatro

et al. 2011

Bone

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Surface contaminants, such as bacterial debris and manufacturing residues, may remain on orthopaedic implants after sterilization procedures and affect osseointegration. The goals of this study were to develop a murine model of osseointegration in order to determine whether removing surface contaminants enhances osseointegration. To develop the murine model, titanium alloy implants were implanted into a unicortical pilot hole in the mid-diaphysis of the femur and osseointegration was measured over a five week time course. Histology, backscatter scanning electron microscopy and x-ray energy dispersive spectroscopy showed areas of bone in intimate physical contact with the implant, confirming osseointegration. Histomorphometric quantification of bone-to-implant contact and peri-implant bone and biomechanical pullout quantification of ultimate force, stiffness and work to failure increased significantly over time, also demonstrating successful osseointegration. We also found that a rigorous cleaning procedure significantly enhances bone-to-implant contact and biomechanical pullout measures by two-fold compared with implants that were autoclaved, as recommended by the manufacturer. The most likely interpretation of these results is that surface contaminants inhibit osseointegration. The results of this study justify the need for the development of better detection and removal techniques for contaminants on orthopaedic implants and other medical devices.

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Section: Discussionmentioning

confidence: 99%

Surface contaminants inhibit osseointegration in a novel murine model

Bonsignore

Colbrunn

Tatro

et al. 2011

Bone

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“…No differences in interface stiffness or maximum load were found between the two different foam implants at any of the time points in the study, suggesting the difference in pore size between the two titanium foams did not affect the mechanical response. The failure mode of the foam implants suggests that push-out testing may not have been the most appropriate method to compare mechanical characteristics of bone apposition between the implants, due to the difference in compressive modulus 24,25 between the foam implants (~3 GPa) and the more dense sintered beaded implants (~10 GPa) 26.…”

Section: Discussionmentioning

confidence: 99%

Osseointegration into a novel titanium foam implant in the distal femur of a rabbit

et al. 2009

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A novel porous titanium foam implant has recently been developed to enhance biological fixation of orthopaedic implants to bone. The aim of this study was to examine the mechanical and histological characteristics of bone apposition into two different pore sizes of this titanium foam (565 and 464 micron mean void intercept length) and to compare these characteristics to those obtained with a fully porous conventionally sintered titanium bead implant. Cylindrical implants were studied in a rabbit distal femoral intramedullary osseointegration model at time zero and at 3, 6, and 12 weeks. The amount of bone ingrowth, amount of periprosthetic bone, and mineral apposition rate of periprosthetic bone measured did not differ among the three implant designs at 3, 6, or 12 weeks. By 12 weeks, the interface stiffness and maximum load of the beaded implant was significantly greater than either foam implant. No significant difference was found in the interface stiffness or maximum load between the two foam implant designs at 3, 6, or 12 weeks. The lower compressive modulus of the foam compared to the more dense sintered beaded implants likely contributed to the difference in failure mode. However, the foam implants have a similar compressive modulus to other clinically successful coatings, suggesting they are nonetheless clinically adequate. Additional studies are required to confirm this in weight-bearing models. Histological data suggest that these novel titanium foam implants are a promising alternative to current porous coatings and should be further investigated for clinical application in cementless joint replacement.

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“…For assessment of implant fixation strength we used a pull‐out test rather than a push‐out test because it was much simpler to maintain the direction of force in line with the implant, given the small size of the specimens. Pull‐out and push‐out tests give comparable results when the tests are performed appropriately and the force data are normalized to the nominal surface area of the implant in contact with tissue 26. Use of the pull‐out test, while providing perhaps the most important outcome measurement, was destructive and did not permit use of histology to corroborate the μCT findings.…”

Section: Discussionmentioning

confidence: 99%

Saline irrigation does not affect bone formation or fixation strength of hydroxyapatite/tricalcium phosphate‐coated implants in a rat model

et al. 2005

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Intramembranous bone regeneration is critical to implant fixation. In cementless joint replacement (as opposed to cemented joint replacement), saline irrigation is not typically performed during surgery so that the osteogenic stimulus provided by the marrow is preserved. Several groups are now using the rat marrow ablation model to study intramembranous bone regeneration and implant fixation. In this model, the marrow contents are mechanically disrupted, and debris is often cleared by saline irrigation, a step that appears inconsistent with the clinical situation. Furthermore, in contrast to conventional wisdom, it has been reported that saline irrigation enhanced bone-implant contact and peri-implant bone formation in the rat model (Ishizaka et al. Bone 1996;19:589-594), although mechanical fixation of the implant was not investigated. Accordingly, the present study was performed to determine if saline irrigation leads to enhanced mechanical fixation of implants in the rat model. Forty-eight 400 to 450 g male rats were divided equally into two groups. The treatment group, in contrast to the control group, received saline irrigation in the ablated medullary canal prior to placement of hydroxyapatite/tricalcium phosphate-coated implants. Eight animals in each group were killed at 2, 4, or 8 weeks after implantation, at which time the specimens were analyzed by micro computed tomography to measure bone formation around the implant, followed by a mechanical pull-out test to measure the strength of fixation of the implant. As expected, there was increased fixation strength over time, but there were no significant differences in peri-implant bone volume, bone-implant contact, or implant fixation strength between the two groups. Thus, we found no effect of saline irrigation on bone formation or implant fixation strength in this study in which the implant had an osteoconductive coating.

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Implant Pushout and Pullout Tests

Cited by 17 publications

References 18 publications

Surface contaminants inhibit osseointegration in a novel murine model

Surface contaminants inhibit osseointegration in a novel murine model

Osseointegration into a novel titanium foam implant in the distal femur of a rabbit

Saline irrigation does not affect bone formation or fixation strength of hydroxyapatite/tricalcium phosphate‐coated implants in a rat model

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