The Open Orthopaedics Journal




ISSN: 1874-3250 ― Volume 13, 2019

Acid Etching and Plasma Sterilization Fail to Improve Osseointegration of Grit Blasted Titanium Implants



Mikkel Saksø*, Stig S Jakobsen, Henrik Saksø, Jørgen Baas, Thomas Jakobsen, Kjeld Søballe
Department of Orthopaedics, Aarhus University Hospital, Aarhus, Denmark

Abstract

Interaction between implant surface and surrounding bone influences implant fixation. We attempted to improve the bone-implant interaction by 1) adding surface micro scale topography by acid etching, and 2) removing surface-adherent pro-inflammatory agents by plasma cleaning. Implant fixation was evaluated by implant osseointegration and biomechanical fixation.

The study consisted of two paired animal sub-studies where 10 skeletally mature Labrador dogs were used. Grit blasted titanium alloy implants were inserted press fit in each proximal tibia. In the first study grit blasted implants were compared with acid etched grit blasted implants. In the second study grit blasted implants were compared with acid etched grit blasted implants that were further treated with plasma sterilization. Implant performance was evaluated by histomorphometrical investigation (tissue-to-implant contact, peri-implant tissue density) and mechanical push-out testing after four weeks observation time.

Neither acid etching nor plasma sterilization of the grit blasted implants enhanced osseointegration or mechanical fixation in this press-fit canine implant model in a statistically significant manner.

Keywords:: Acid etching, biocompatibility, endotoxin, implant surgery, grit blasting, plasma sterilization, titanium.


Article Information


Identifiers and Pagination:

Year: 2012
Volume: 6
First Page: 376
Last Page: 382
Publisher Id: TOORTHJ-6-376
DOI: 10.2174/1874325001206010376

Article History:

Received Date: 24/4/2012
Revision Received Date: 22/6/2012
Acceptance Date: 25/6/2012
Electronic publication date: 3/9/2012
Collection year: 2012

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© Saksø et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.


* Address correspondence to this author at the Orthopaedic Research Laboratory, Aarhus University Hospital, Nørrebrogade 44, DK – 8000 Aarhus C, Denmark; Tel: +45 8949 7471; Fax: +45 8949 7429; E-mail: Saksoe@gmail.com




INTRODUCTION

In the western world, more than 2% of the population over 60 years receive a total hip replacement [1 Lucht U. The Danish hip arthroplasty register Acta Orthop Scand 2000; 71(5 ): 433-9.] and each year one million hip replacements are inserted worldwide. Implant failure due to aseptic loosening is a serious, painful and potentially invalidating complication. 1 to 5% of all uncemented hip implants fail within fifteen years of implantation [2Overgaard S. Danish Hip Arthroplasty Register. Annual Report 2011 [Online] Available from http;//www.dhr.dk/Ny%20mapp e/rapporter/ DHR%20Aarsrapport_2011%20t_web.pdf.2011 ].

Rapid initial fixation of the implant is imperative to ensure long-term implant survival [3 Karrholm J, Borssen B, Lowenhielm G, Snorrason F. Does early micromotion of femoral stem prostheses matter? 4-7-year stereoradiographic follow-up of 84 cemented prostheses J Bone Joint Surg Br 1994; 76(6 ): 912-7.]. If the implant is not stable, micro motion between the implant and the surrounding bone will increase the risk of fibrous encapsulation of the implant [4 Aspenberg P, Herbertsson P. Periprosthetic bone resorption. Particles versus movement J Bone Joint Surg Br 1996; 78(4 ): 641-., 5 Soballe K, Hansen ES, Rasmussen H, Jorgensen PH, Bunger C. Tissue ingrowth into titanium and hydroxyapatite-coated implants during stable and unstable mechanical conditions J Orthop Res 1992; 10(2 ): 285-99.], which inhibits bone ingrowth and thus increases the risk of loosening of the implant.

The macro-scale porosity of the implant surface plays an important role in osseointegration of the implant [6 Bobyn JD, Pilliar RM, Cameron HU, Weatherly GC. The optimum pore size for the fixation of porous-surfaced metal implants by the ingrowth of bone Clin Orthop Relat Res 1980; (150): 263-70.]. Furthermore, in recent years the concept of using micro-scale topography to stimulate bone forming osteoblasts has been investigated by several different groups [7 Att W, Tsukimura N, Suzuki T, Ogawa T. Effect of supramicron roughness characteristics produced by 1- and 2-step acid etching on the osseointegration capability of titanium Int J Oral Maxillofac Implants 2007; 22(5 ): 719-28.-9 Zinger O, Zhao G, Schwartz Z, et al. Differential regulation of osteoblasts by substrate microstructural features Biomaterials 2005; 26(14 ): 1837-47.]. Applying micro-scale topographical changes onto clinically rough surfaces has, however, proven difficult.

Etching of titanium implants enables the application of micro-topographical changes onto macro-scale porosities [10 Fandridis J, Papadopoulos T. Surface characterization of three titanium dental implants Implant Dent 2008; 17(1 ): 91-.]. In vivo studies have shown enhanced osseointegration of acid etched implants compared to non-etched controls [11 Cho SA, Park KT. The removal torque of titanium screw inserted in rabbit tibia treated by dual acid etching Biomaterials 2003; 24(20 ): 3611-7.-13 Klokkevold PR, Johnson P, Dadgostari S, Caputo A, Davies JE, Nishimura RD. Early endosseous integration enhanced by dual acid etching of titanium: a torque removal study in the rabbit Clin Oral Implants Res 2001; 12(4 ): 350-7.]. Furthermore, etching a grit blasted surface eliminates the inherent problem of ceramic particle residues thereby reducing the particle load in the peri-implant space.

In addition, superior implant biocompatibility may further improve osseointegration. Endotoxins are molecules from the cell walls of bacteria, that induce a massive inflammatory response from macrophages leading to fibrous capsule formation [14 Greenfield EM, Bi Y, Ragab AA, Goldberg VM, Nalepka JL, Seabold JM. Does endotoxin contribute to aseptic loosening of orthopedic implants? J Biomed Mater Res Part B Appl Biomater 2005; 72(1 ): 179-85.]. Implants surrounded by a fibrous capsule have an increased probability of loosening, compared to prostheses that are directly anchored in bone [15 Santavirta S, Xu JW, Hietanen J, et al. Activation of periprosthetic connective tissue in aseptic loosening of total hip replacements Clin Orthop Relat Res 1998; (352): 16-24.]. Endotoxins have previously been found extensively on the surface of commercially available implants [16 Ragab AA, Van De MR, Lavish SA, et al. Measurement and removal of adherent endotoxin from titanium particles and implant surfaces J Orthop Res 1999; 17(6 ): 803-9.]. Consequently, increasing the biocompatibility of implants osseointegration and reducing the probability of implant loosening by removal or inactivation of the endotoxins from the surface of the implants [14 Greenfield EM, Bi Y, Ragab AA, Goldberg VM, Nalepka JL, Seabold JM. Does endotoxin contribute to aseptic loosening of orthopedic implants? J Biomed Mater Res Part B Appl Biomater 2005; 72(1 ): 179-85.] by plasma sterilization appear promising [17 Tessarolo F, Caola I, Nollo G, Antolini R, Guarrera GM, Caciagli P. Efficiency in endotoxin removal by a reprocessing protocol for electrophysiology catheters based on hydrogen peroxide plasma sterilization Int J Hyg Environ Health 2006; 209(6 ): 557-65., 18 Lerouge S, Wertheimer MR, Yahia L'H. Plasma sterilization: a review of parameters, mechanisms, and limitations Plasmas Polym 2001; 6(3 ): 175-88.].

We hypothesized that acid etching improves early osseointegration and implant fixation of grit blasted titanium implants as evidenced by improved biomechanical implant fixation, increased formation of new bone, and decreased presence of fibrous tissue. Furthermore, we hypothesized that removing the bio-burden by plasma sterilization of the implants would improve these parameters additionally.

MATERIALS AND METHODOLOGY

Design

The study consisted of two separate sub-studies, both designed as paired animal studies. A total of ten skeletally mature Labrador dogs were used. Mean body weight was 34 kg [range 25 kg: 39 kg]. Mean age was 18 months [range 14-23 months]. Each dog had two implants inserted medially in the proximal part of the tibia. Each dog had four implants, so a total of 40 implants were used. The implants were inserted press-fit in cortico-cancellous bone. In the upper tibia site, we investigated the effect of surface etching on grit blasted implants. At the more distal tibia site we investigated the effect of combining surface etching and plasma sterilization on grit blasted implants. Due to denser bone quality, the upper tibia surgical site offered a better biomechanical implant fixation compared to the lower site (p=0.0098). Hence, no cross comparisons between the two sub-studies was performed. The observation time was four weeks (Fig. 1).

Fig. (1)

Schematic drawing of the placement of the implant pairs in the right and left tibia.



Animals and Surgical Procedure

Under general anesthesia, using sterile technique, the proximal part of tibia was exposed through an anteromedial extraarticular approach. Two Kirschner (K) wires were inserted perpendicular to the surface with 15.0 mm in between. The most proximal K wire was inserted with the implant centre 15 mm from the tibia plateau. The K-wires guided the 5.5 mm cannulated drill creating 11.0-mm-deep holes. Drilling was performed at two rotations per second to prevent thermal trauma to the bone. All bone debris and soft tissue was removed from the drill hole before the implant was inserted (press fit). Finally, the soft tissue was closed in layers. Pre-and postoperatively, the dogs were given one dose of Cefuroxim, 1.5 g intravenously, as antibiotic prophylaxis. A fentanyl transdermal patch (75 μg/h) lasting three days was given as postoperative analgesic treatment. The dogs were allowed full weight bearing postoperatively. The dogs were bred for scientific purposes, and the study was approved and monitored by the Danish Animal Research Committee (Fig. 2).

Fig. (2)

Peri-operative picture showing the two implants inserted medially in the proximal part of the right tibia.



The Implants

The aluminum oxide (Al2O3) grit blasted implants (L = 10 mm, Ø = 6 mm) were made out of Ti-6Al-4V alloy (Depuy Inc., Warsaw, IN, USA). The implants had a central threaded hole which in combination with a threaded rod made it possible to handle and insert the implants without touching and thereby potentially polluting the implant surface. The implants were prepared as follows.

Acid etching: Acid etching was done at room temperature in an acidified NaF solution for six minutes. The implants were then rinsed with a 1% Alconox (Alconox, Inc., White Plains, NY, USA) and 2% Liquinox (Alconox, Inc., White Plains, NY, USA) detergent at 45ºC for 30 minutes. The implants were then rinsed three times in 15 minute cycles with RO-H2O at 45ºC. Finally the implants were dried at 60ºC.

Plasma sterilization: The plasma sterilization with pure O2 gas was performed in a 500 Watt plasma chamber (7200 RF Plasma Processing System; PVA TePla America, Inc.) with a gas flow rate of 250 standard cubic centimetres per minute (sccm) and a chamber pressure of 300 mTorr (40 x 10-5 bar). The cycle time was 30 minutes.

Passivation/gamma sterilization: After standard cleaning in the lab passivation of the implants was carried out using the validated (ASTM A967-05) manufacturing passivation process. Parts were passivated using 35% Nitric Acid at 60°C. The cleaning process involved a series of temperature controlled water baths. The samples were dried and packaged by trained employees in the clean room. Parts were then Gamma Sterilized using the same processing plant used for standard DePuy (Depuy Inc., Warsaw, IN, USA) Implants. All of these processes are validated manufacturing processes used for actual DePuy (Depuy Inc., Warsaw, IN, USA) Orthopaedic Implants.

The implants were packaged individually in glass vials with screw lids. The glass vials were packaged in two layers of sterile packaging and one layer of unsterile packaging (a cardboard box).

The implants were attached to the lid with a threaded rod screwed into the hole in the implant. This way the implants did not touch the inside of the glass vial and could be handled and inserted using the rod, without risk of polluting it with endotoxins from sterile gloves or instruments (Fig. 3).

Fig. (3)

SEM pictures of the implant surfaces: In picture d, crystals of aluminum oxide (Al2O3 particles) from the grit blasting are clearly visible. Pictures e and f show the pits created by the etching process and the pictures indicate that the majority of the particles has been removed by the etching process.



Specimen Preparation

After four weeks of observation the animals were sacrificed with an overdose of hyper saturated barbiturate and the proximal part of tibia was excised and cleaned and thereafter stored at –20°C. The outermost 0.5 mm of the implant-bone specimen interphase was cut off and discarded. The rest of the implant with surrounding bone was divided into two sections perpendicular to the long axis of the implant with a water-cooled diamond band saw (Exact Apparatebau, Nordenstedt, Germany). The outermost section was cut to a thickness of 3.5 mm and stored at –20°C pending mechanical testing [19 Linde F, Sorensen HC. The effect of different storage methods on the mechanical properties of trabecular bone J Biomech 1993; 26(10 ): 1249-52.]. The innermost part 6.0 mm was prepared for histomorphometry. The specimens were dehydrated in graded ethanol (70-100%) containing basic fucsin, and embedded in methylmetacrylate (Technovit 7200 VCL; Exact Apparatbau, Nordenstedt, Germany). Four vertical, uniform, random sections were cut with a hard-tissue microtome (KDG-95; MeProTech, Heerhugowaard, The Netherlands) around the center part of each implant as described by Overgaard et al. [20 Overgaard S, Soballe K, Jorgen H, Gundersen G. Efficiency of systematic sampling in histomorphometric bone research illustrated by hydroxyapatite-coated implants: optimizing the stereological vertical-section design J Orthop Res 2000; 18(2 ): 313-21.]. Before making the sections, each cylindrical implant was rotated randomly around its longitudinal axis. The sections were cut parallel to this axis. The 40-μm-thick sections were counterstained with 2% light green (BDH Laboratory Supplies, Poole, UK) and then mounted on glass [21 Gotfredsen K, Budtz-Jorgensen E, Jensen LN. A method for preparing and staining histological sections containing titanium implants for light microscopy Stain Technol 1989; 64(3 ): 121-7.]. This preparation provides red staining of non-calcified tissue and green staining of calcified tissues such as woven and lamellar bone.

Histomorphometrical Evaluation

Blinded histomorphometric analysis was done using a stereological software program (C.A.S.T.-grid Olympus Denmark A/S, Ballerup, Denmark). Fields of vision from a light microscope were captured on a computer monitor and a user-specified grid was superimposed on the microscopic fields. Four vertical sections representative of each implant were analyzed and cumulated [20 Overgaard S, Soballe K, Jorgen H, Gundersen G. Efficiency of systematic sampling in histomorphometric bone research illustrated by hydroxyapatite-coated implants: optimizing the stereological vertical-section design J Orthop Res 2000; 18(2 ): 313-21.].

With the aid of the software, we defined two zones in the sections. Zone 1 stretches from the implant surface and 500 μm outwards into the surrounding tissue, and Zone 2 was defined starting 500 μm from the same implant outer surface line and extending another 500 μm outwards into the surrounding tissue.

In both zone 1 and 2 tissue volume fractions were quantified by point counting [22 Gundersen HJ, Bendtsen TF, Korbo L, et al. Some new, simple and efficient stereological methods and their use in pathological research and diagnosis APMIS 1988; 96(5 ): 379-94.]. On the implant surface, line intercept-technique with sine-weighted lines was used to estimate the bone-implant contact [23 Baddeley AJ, Gundersen HJ, Cruz-Orive LM. Estimation of surface area from vertical sections J Microsc 1986; 142(Pt 3): 259-76.].

Intra-observer variation was determined as coefficients of variation on double measurements on four randomly selected implants. All the coefficients were well within the expected range; however, defining small amounts of new bone on the implant surface and discriminating between new and lamellar bone close to the implant proved troublesome (new bone in zone 1 [24%], lamellar bone on the surface [52%]) (Fig. 4).

Fig. (4)

(A) Picture showing a histological cross section used for Histomorphometry. The close-up picture (B) shows Lamellar Bone (L) and New Bone (N) in contact with the implant surface. Marrow is marked (M).



Mechanical Testing

The thawed implants were tested for failure by axial push-out test on a MTS Bionics Test Machine (MTS, Eden Prairie, MN, USA). The specimens were placed on a metal support jig with a 7.4 mm diameter central opening. The implant was centralized over the opening, assuring a 0.7 mm distance between the implant and the support jig. The direction of loading was from the cortical surface inward. A preload of 2 N was applied to standardize contact conditions before initiating loading. We used a displacement rate of 5 mm/min with a 2,5 kN load cell. Load and deformation were registered by a personal computer. Each specimen length and diameter was measured with a micrometer screw gauge and used to normalize push-out parameters [24 Soballe K. Hydroxyapatite ceramic coating for bone implant fixation. Mechanical and histological studies in dogs Acta Orthop Scand Suppl 1993; 255: 1-58.]. Ultimate shear strength (MPa) was determined from the maximal force applied until failure of the bone-implant interface. Apparent stiffness (MPa/mm) was obtained from the slope of the linear section of the curve. Energy absorption (kJ/m2) was calculated from the area beneath the curve until failure.

Statistics

Histomorphometrical as well as mechanical data followed a normal distribution and a paired t-test was used to distinguish between groups. The data were presented as means with standard deviation (SD). Differences between means were considered statistically significant for p-values less than 0.05.

RESULTS

Surgery

All dogs were fully weight bearing within three days of surgery. No postoperative complications were seen, and no dogs were excluded during the observation period. No signs of infection were seen during the harvesting of the specimens.

Histomorphometrical Results (Tables 1 and 2)

Table 1

Sub-Study 1 (Upper Site)

Tissue Area and Volume Fractions

Surface (0 µm): Tissue Area Fraction in Percent

Zone 1 (0-500 µm): Tissue Volume Fraction in Percent

Zone 2 (500-1000 µm): Tissue Volume Fraction in Percent




Table 2

Sub-Study 2 (lower site).

Tissue Area and Volume Fractions

Surface (0 µm): Tissue Area Fraction in Percent

Zone 1 (0-500 µm): Tissue Volume Fraction in Percent

Zone 2 (500-1000 µm): Tissue Volume Fraction in Percent.




There were no statistically significant differences between Grit Blasted and Grit Blasted+Acid Etched (sub-study 1), or Grit Blasted and Grit Blasted+Acid Etched+Plasma Sterilized (sub-study 2) in regards to any of the tissues compared in any of the zones measured.

All implants were well osseointegrated, with almost 50% of the implant surface in direct bone contact in sub-study 1 (upper site) and almost 40% implant to bone contact in sub-study 2 (lower site). Furthermore, there was no fibrous tissue in the bone-implant interface in sub-study 1, and only 5% in sub-study 2.

Biomechanical Results (Table 3)

Table 3

Data of Mechanical Parameters: Strength, Energy, Stiffness




By gross observation, all implants were well anchored in the bone. The mechanical testing confirmed this observation.

The implants in sub study 1, which were placed more proximally in the tibia were significantly better anchored in all three mechanical parameters (strength, energy and stiffness) than the implants in sub study 2 at the more distal tibial location. No statistically significant mechanical differences were found within the two individual sub studies.

DISCUSSION

The purpose of this study was to improve implant osseointegration and thereby long-term implant survival by two different approaches. One approach was applying micro-textural changes on gritblasted implant surfaces by acid etching. The other approach was the removal of surface-adherent pro-inflammatory agents by plasma sterilization.

We showed that neither etching alone, nor etching combined with plasma sterilization improved the osseointegration and the fixation of the grit blasted titanium implants in a press-fit canine implant model.

The canine implant model was chosen because canine cancellous bone closely resembles human cancellous bone [25 Aerssens J, Boonen S, Lowet G, Dequeker J. Interspecies differences in bone composition, density, and quality: potential implications for in vivo bone research Endocrinology 1998; 139(2 ): 663-70.]. The paired design of the two sub-studies eliminates the influence of interindividual differences between the test animals. All implants were placed extra-articularly and not exposed to direct loading, which limits this model in its representation of a clinical joint replacement. The model is, however, well established and has in numerous publications shown a good ability to detect subtle differences in mechanical fixation and osseointegration caused by surface modifications [26 Daugaard H, Elmengaard B, Bechtold JE, Soballe K. Bone growth enhancement in vivo on press-fit titanium alloy implants with acid etched microtexture J Biomed Mater Res A 2008; 87(2 ): 434-0.-28 Zainali K, Danscher G, Jakobsen T, et al. Effects of gold coating on experimental implant fixation J Biomed Mater Res A 2009; 88(1 ): 274-80.]. Grit-blasted implants were chosen because they represent a well-recognized, clinically applied surface for uncemented joint replacement components [29 Delaunay C, Kapandji AI. Survival analysis of cementless gritblasted titanium total hip arthroplasties J Bone Joint Surg Br 2001; 83(3 ): 408-13., 30 Goldberg VM, Stevenson S, Feighan J, Davy D. Biology of grit-blasted titanium alloy implants Clin Orthop Relat Res 1995; (319): 122-9.].

Previous studies have shown positive effects of acid etching of titanium implants, using a similar canine implant model [26 Daugaard H, Elmengaard B, Bechtold JE, Soballe K. Bone growth enhancement in vivo on press-fit titanium alloy implants with acid etched microtexture J Biomed Mater Res A 2008; 87(2 ): 434-0.]. However, both the baseline treatment of the implants and the etching technology were different. Daugaard et al. used a dual etching technique on a chemically milled surface, whereas we used single etching on a commercial available grit blasted surface. Better performing control coatings together with a slightly increased under-drilling (0.1 mm – 0.5 mm) in our setting may explain the increased bone-to-implant contact in our study (more than 50% in both groups in sub-study 1) compared to Daugaard et al. (control: 18.4%, etched: 36.2%). This excellent degree of osseointegration may have been difficult to further improve.

As previously reported, we also observed that etching reduced the amount of grit blasting debris on the implant surface [31 Szmukler-Moncler S, Testori T, Bernard JP. Etched implants: a comparative surface analysis of four implant systems J Biomed Mater Res Part B Appl Biomater 2004; 69(1 ): 46-57.]. We did not see any short-term benefits of this in terms of osseointegration and early implant fixation.

Although clearing the implant surface of endotoxin theoretically would improve osseointegration, we found no positive effect of plasma sterilizing the etched implants. This may very well reflect the fact that there is a dose dependent response to endotoxin. Endotoxin tends to accumulate on polyethylene, and the negative effect of polyethylene wear particles can partly be ascribed to surface-adherent endotoxin [32 Cho DR, Shanbhag AS, Hong CY, Baran GR, Goldring SR. The role of adsorbed endotoxin in particle-induced stimulation of cytokine release J Orthop Res 2002; 20(4 ): 704-13.].

Furthermore, after insertion of an endotoxin free implant, endogenous endotoxins will adhere to its surface. If an implant contaminated with exogenous endotoxin is inserted, some of the endotoxin will be cleared from the implant. This potentially establishes a comparable steady state concentration of endotoxin on the surface of both intervention and control implants [33 Tatro JM, Taki N, Islam AS, et al. The balance between endotoxin accumulation and clearance during particle-induced osteolysis in murine calvaria J Orthop Res 2007; 25(3 ): 361-9.].

Even though acid etching did not improve the initial osseointegration in this study, the reduction of alumina particles on the implant surface may prove beneficial long-term by reducing the amount of particulate metal in the periprosthetic tissue [34 Bohler M, Kanz F, Schwarz B, et al. Adverse tissue reactions to wear particles from Co-alloy articulations, increased by alumina-blasting particle contamination from cementless Ti-based total hip implants. A report of seven revisions with early failure J Bone Joint Surg Br 2002; 84(1 ): 128-36.]. In clinical practice, only a small portion (10% to 20%) of the un-cemented press-fit implant surface is in bone contact [35 Geesink RG. Osteoconductive coatings for total joint arthroplasty Clin Orthop Relat Res 2002; (395): 53-65.]. Therefore improvement of the remaining 80% - 90% should be investigated in a model where ‘over-drilling’ introduces a small gap between the bone and the implant surface. Analysis of the bone/implant interface directly after implant insertion could be interesting to perform in future studies. This would provide a base line level of bone contact before the four weeks observation time. Furthermore, to test the effect of the bio burden, it would be relevant to perform a dose-response study.

CONCLUSION

Neither acid etching nor plasma sterilization of the grit blasted implants enhanced osseointegration or mechanical fixation in this press-fit canine implant model in a statistically significant manner. Two theoretically attractive ways of improving implants performance failed to prove efficiency in this press-fit canine implant model. All implants performed extremely well both in regards of osseointegration and mechanical fixation presenting a likely explanation for the lack of any proven benefits by acid etching and plasma sterilization.

ACKNOWLEDGEMENT

The authors would like to thank Depuy Orthopaedics Inc. for financial and material support. The authors would also like to thank laboratory technicians Jane Pauli and Annette Milton for excellent laboratory work.

CONFLICT OF INTEREST

The author(s) confirm that this article content has no conflicts of interest.

ABBREVIATIONS

AE  = Acid Etched
GB  = Grit Blasted
K-wire  = Kirschner wire: sterilized, sharpened, smooth stainless steel pin
KJ  = Kilo Joule = 1000 Joule. Joule is the SI-unit of energy
kN  = Kilo Newton = 1000 Newton
MPa  = Megapascal = 1.000.000 Pascal. Pascal is the SI-unit of presure
N  = Newton: Newton is the SI-unit of force
PS  = Plasma Sterilized
SD  = Standard Deviation

REFERENCES

[1] Lucht U. The Danish hip arthroplasty register Acta Orthop Scand 2000; 71(5 ): 433-9.
[2] Overgaard S. Danish Hip Arthroplasty Register. Annual Report 2011 [Online] Available from http;//www.dhr.dk/Ny%20mapp e/rapporter/ DHR%20Aarsrapport_2011%20t_web.pdf.2011
[3] Karrholm J, Borssen B, Lowenhielm G, Snorrason F. Does early micromotion of femoral stem prostheses matter? 4-7-year stereoradiographic follow-up of 84 cemented prostheses J Bone Joint Surg Br 1994; 76(6 ): 912-7.
[4] Aspenberg P, Herbertsson P. Periprosthetic bone resorption. Particles versus movement J Bone Joint Surg Br 1996; 78(4 ): 641-.
[5] Soballe K, Hansen ES, Rasmussen H, Jorgensen PH, Bunger C. Tissue ingrowth into titanium and hydroxyapatite-coated implants during stable and unstable mechanical conditions J Orthop Res 1992; 10(2 ): 285-99.
[6] Bobyn JD, Pilliar RM, Cameron HU, Weatherly GC. The optimum pore size for the fixation of porous-surfaced metal implants by the ingrowth of bone Clin Orthop Relat Res 1980; (150): 263-70.
[7] Att W, Tsukimura N, Suzuki T, Ogawa T. Effect of supramicron roughness characteristics produced by 1- and 2-step acid etching on the osseointegration capability of titanium Int J Oral Maxillofac Implants 2007; 22(5 ): 719-28.
[8] Owen GR, Jackson J, Chehroudi B, Burt H, Brunette DM. A PLGA membrane controlling cell behaviour for promoting tissue regeneration Biomaterials 2005; 26(35 ): 7447-56.
[9] Zinger O, Zhao G, Schwartz Z, et al. Differential regulation of osteoblasts by substrate microstructural features Biomaterials 2005; 26(14 ): 1837-47.
[10] Fandridis J, Papadopoulos T. Surface characterization of three titanium dental implants Implant Dent 2008; 17(1 ): 91-.
[11] Cho SA, Park KT. The removal torque of titanium screw inserted in rabbit tibia treated by dual acid etching Biomaterials 2003; 24(20 ): 3611-7.
[12] Hacking SA, Harvey EJ, Tanzer M, Krygier JJ, Bobyn JD. Acidetched microtexture for enhancement of bone growth into porouscoated implants J Bone Joint Surg Br 2003; 85(8 ): 1182-9.
[13] Klokkevold PR, Johnson P, Dadgostari S, Caputo A, Davies JE, Nishimura RD. Early endosseous integration enhanced by dual acid etching of titanium: a torque removal study in the rabbit Clin Oral Implants Res 2001; 12(4 ): 350-7.
[14] Greenfield EM, Bi Y, Ragab AA, Goldberg VM, Nalepka JL, Seabold JM. Does endotoxin contribute to aseptic loosening of orthopedic implants? J Biomed Mater Res Part B Appl Biomater 2005; 72(1 ): 179-85.
[15] Santavirta S, Xu JW, Hietanen J, et al. Activation of periprosthetic connective tissue in aseptic loosening of total hip replacements Clin Orthop Relat Res 1998; (352): 16-24.
[16] Ragab AA, Van De MR, Lavish SA, et al. Measurement and removal of adherent endotoxin from titanium particles and implant surfaces J Orthop Res 1999; 17(6 ): 803-9.
[17] Tessarolo F, Caola I, Nollo G, Antolini R, Guarrera GM, Caciagli P. Efficiency in endotoxin removal by a reprocessing protocol for electrophysiology catheters based on hydrogen peroxide plasma sterilization Int J Hyg Environ Health 2006; 209(6 ): 557-65.
[18] Lerouge S, Wertheimer MR, Yahia L'H. Plasma sterilization: a review of parameters, mechanisms, and limitations Plasmas Polym 2001; 6(3 ): 175-88.
[19] Linde F, Sorensen HC. The effect of different storage methods on the mechanical properties of trabecular bone J Biomech 1993; 26(10 ): 1249-52.
[20] Overgaard S, Soballe K, Jorgen H, Gundersen G. Efficiency of systematic sampling in histomorphometric bone research illustrated by hydroxyapatite-coated implants: optimizing the stereological vertical-section design J Orthop Res 2000; 18(2 ): 313-21.
[21] Gotfredsen K, Budtz-Jorgensen E, Jensen LN. A method for preparing and staining histological sections containing titanium implants for light microscopy Stain Technol 1989; 64(3 ): 121-7.
[22] Gundersen HJ, Bendtsen TF, Korbo L, et al. Some new, simple and efficient stereological methods and their use in pathological research and diagnosis APMIS 1988; 96(5 ): 379-94.
[23] Baddeley AJ, Gundersen HJ, Cruz-Orive LM. Estimation of surface area from vertical sections J Microsc 1986; 142(Pt 3): 259-76.
[24] Soballe K. Hydroxyapatite ceramic coating for bone implant fixation. Mechanical and histological studies in dogs Acta Orthop Scand Suppl 1993; 255: 1-58.
[25] Aerssens J, Boonen S, Lowet G, Dequeker J. Interspecies differences in bone composition, density, and quality: potential implications for in vivo bone research Endocrinology 1998; 139(2 ): 663-70.
[26] Daugaard H, Elmengaard B, Bechtold JE, Soballe K. Bone growth enhancement in vivo on press-fit titanium alloy implants with acid etched microtexture J Biomed Mater Res A 2008; 87(2 ): 434-0.
[27] Elmengaard B, Bechtold JE, Soballe K. In vivo study of the effect of RGD treatment on bone ongrowth on press-fit titanium alloy implants Biomaterials 2005; 26(17 ): 3521-6.
[28] Zainali K, Danscher G, Jakobsen T, et al. Effects of gold coating on experimental implant fixation J Biomed Mater Res A 2009; 88(1 ): 274-80.
[29] Delaunay C, Kapandji AI. Survival analysis of cementless gritblasted titanium total hip arthroplasties J Bone Joint Surg Br 2001; 83(3 ): 408-13.
[30] Goldberg VM, Stevenson S, Feighan J, Davy D. Biology of grit-blasted titanium alloy implants Clin Orthop Relat Res 1995; (319): 122-9.
[31] Szmukler-Moncler S, Testori T, Bernard JP. Etched implants: a comparative surface analysis of four implant systems J Biomed Mater Res Part B Appl Biomater 2004; 69(1 ): 46-57.
[32] Cho DR, Shanbhag AS, Hong CY, Baran GR, Goldring SR. The role of adsorbed endotoxin in particle-induced stimulation of cytokine release J Orthop Res 2002; 20(4 ): 704-13.
[33] Tatro JM, Taki N, Islam AS, et al. The balance between endotoxin accumulation and clearance during particle-induced osteolysis in murine calvaria J Orthop Res 2007; 25(3 ): 361-9.
[34] Bohler M, Kanz F, Schwarz B, et al. Adverse tissue reactions to wear particles from Co-alloy articulations, increased by alumina-blasting particle contamination from cementless Ti-based total hip implants. A report of seven revisions with early failure J Bone Joint Surg Br 2002; 84(1 ): 128-36.
[35] Geesink RG. Osteoconductive coatings for total joint arthroplasty Clin Orthop Relat Res 2002; (395): 53-65.

Endorsements



"Open access will revolutionize 21st century knowledge work and accelerate the diffusion of ideas and evidence that support just in time learning and the evolution of thinking in a number of disciplines."


Daniel Pesut
(Indiana University School of Nursing, USA)

"It is important that students and researchers from all over the world can have easy access to relevant, high-standard and timely scientific information. This is exactly what Open Access Journals provide and this is the reason why I support this endeavor."


Jacques Descotes
(Centre Antipoison-Centre de Pharmacovigilance, France)

"Publishing research articles is the key for future scientific progress. Open Access publishing is therefore of utmost importance for wider dissemination of information, and will help serving the best interest of the scientific community."


Patrice Talaga
(UCB S.A., Belgium)

"Open access journals are a novel concept in the medical literature. They offer accessible information to a wide variety of individuals, including physicians, medical students, clinical investigators, and the general public. They are an outstanding source of medical and scientific information."


Jeffrey M. Weinberg
(St. Luke's-Roosevelt Hospital Center, USA)

"Open access journals are extremely useful for graduate students, investigators and all other interested persons to read important scientific articles and subscribe scientific journals. Indeed, the research articles span a wide range of area and of high quality. This is specially a must for researchers belonging to institutions with limited library facility and funding to subscribe scientific journals."


Debomoy K. Lahiri
(Indiana University School of Medicine, USA)

"Open access journals represent a major break-through in publishing. They provide easy access to the latest research on a wide variety of issues. Relevant and timely articles are made available in a fraction of the time taken by more conventional publishers. Articles are of uniformly high quality and written by the world's leading authorities."


Robert Looney
(Naval Postgraduate School, USA)

"Open access journals have transformed the way scientific data is published and disseminated: particularly, whilst ensuring a high quality standard and transparency in the editorial process, they have increased the access to the scientific literature by those researchers that have limited library support or that are working on small budgets."


Richard Reithinger
(Westat, USA)

"Not only do open access journals greatly improve the access to high quality information for scientists in the developing world, it also provides extra exposure for our papers."


J. Ferwerda
(University of Oxford, UK)

"Open Access 'Chemistry' Journals allow the dissemination of knowledge at your finger tips without paying for the scientific content."


Sean L. Kitson
(Almac Sciences, Northern Ireland)

"In principle, all scientific journals should have open access, as should be science itself. Open access journals are very helpful for students, researchers and the general public including people from institutions which do not have library or cannot afford to subscribe scientific journals. The articles are high standard and cover a wide area."


Hubert Wolterbeek
(Delft University of Technology, The Netherlands)

"The widest possible diffusion of information is critical for the advancement of science. In this perspective, open access journals are instrumental in fostering researches and achievements."


Alessandro Laviano
(Sapienza - University of Rome, Italy)

"Open access journals are very useful for all scientists as they can have quick information in the different fields of science."


Philippe Hernigou
(Paris University, France)

"There are many scientists who can not afford the rather expensive subscriptions to scientific journals. Open access journals offer a good alternative for free access to good quality scientific information."


Fidel Toldrá
(Instituto de Agroquimica y Tecnologia de Alimentos, Spain)

"Open access journals have become a fundamental tool for students, researchers, patients and the general public. Many people from institutions which do not have library or cannot afford to subscribe scientific journals benefit of them on a daily basis. The articles are among the best and cover most scientific areas."


M. Bendandi
(University Clinic of Navarre, Spain)

"These journals provide researchers with a platform for rapid, open access scientific communication. The articles are of high quality and broad scope."


Peter Chiba
(University of Vienna, Austria)

"Open access journals are probably one of the most important contributions to promote and diffuse science worldwide."


Jaime Sampaio
(University of Trás-os-Montes e Alto Douro, Portugal)

"Open access journals make up a new and rather revolutionary way to scientific publication. This option opens several quite interesting possibilities to disseminate openly and freely new knowledge and even to facilitate interpersonal communication among scientists."


Eduardo A. Castro
(INIFTA, Argentina)

"Open access journals are freely available online throughout the world, for you to read, download, copy, distribute, and use. The articles published in the open access journals are high quality and cover a wide range of fields."


Kenji Hashimoto
(Chiba University, Japan)

"Open Access journals offer an innovative and efficient way of publication for academics and professionals in a wide range of disciplines. The papers published are of high quality after rigorous peer review and they are Indexed in: major international databases. I read Open Access journals to keep abreast of the recent development in my field of study."


Daniel Shek
(Chinese University of Hong Kong, Hong Kong)

"It is a modern trend for publishers to establish open access journals. Researchers, faculty members, and students will be greatly benefited by the new journals of Bentham Science Publishers Ltd. in this category."


Jih Ru Hwu
(National Central University, Taiwan)


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