Maximilian Haenle

An extended spectrum bactericidal titanium dioxide (TiO2) coating for metallic implants: in vitro effectiveness against MRSA and mechanical properties.

Implant infections remain feared and severe complications after total joint arthroplasty. The incidence of multi-resistant pathogens, causing such infections, is rising continuously, and orthopaedic surgeons are confronted with an ever-changing resistance pattern. Anti-infectious surface coatings aim for a high local effective concentration and a low systemic toxicity at the same time. Antibacterial efficacy and biomechanical stability of a novel broad-spectrum anti-infectious coating is assessed in the present study. Antibacterial efficacy of a sol–gel derived titanium dioxide (TiO2) coating for metal implants with and without integrated copper ions as antibiotic agent was assessed against methicillin resistant Staphylococcus aureus (MRSA 27065). Both bacterial surface adhesion and growth of planktonic bacteria were assessed with bare and various TiO2-coated Ti6Al4V metal discs. Furthermore, bonding strength of the TiO2 surface coating, using standard testing procedures, as well as surface roughness were determined. We found a significant reduction of the bacterial growth rate for the coatings with integrated copper ions, with highest reduction rates observed for a fourfold copper TiO2-coating. Pure TiO2 without integrated copper ions did not reduce bacterial growth compared to uncoated Ti6Al4V. The coating was not detached from the substrate by standard adhesive failure testing, which indicated an excellent durability of the implant coating. The TiO2 coating with integrated copper ions could offer a new strategy for preventing implant-associated infections, with antibacterial properties not only against the most common bacteria causing implant infections but also against multiresistant strains such as MRSA.

Evaluation of Osseointegration of Titanium Alloyed Implants Modified by Plasma Polymerization

By means of plasma polymerization, positively charged, nanometre-thin coatings can be applied to implant surfaces. The aim of the present study was to quantify the adhesion of human bone cells in vitro and to evaluate the bone ongrowth in vivo, on titanium surfaces modified by plasma polymer coatings. Different implant surface configurations were examined: titanium alloy (Ti6Al4V) coated with plasma-polymerized allylamine (PPAAm) and plasma-polymerized ethylenediamine (PPEDA) versus uncoated. Shear stress on human osteoblast-like MG-63 cells was investigated in vitro using a spinning disc device. Furthermore, bone-to-implant contact (BIC) was evaluated in vivo. Custom-made conical titanium implants were inserted at the medial tibia of female Sprague-Dawley rats. After a follow-up of six weeks, the BIC was determined by means of histomorphometry. The quantification of cell adhesion showed a significantly higher shear stress for MG-63 cells on PPAAm and PPEDA compared to uncoated Ti6Al4V. Uncoated titanium alloyed implants showed the lowest BIC (40.4%). Implants with PPAAm coating revealed a clear but not significant increase of the BIC (58.5%) and implants with PPEDA a significantly increased BIC (63.7%). In conclusion, plasma polymer coatings demonstrate enhanced cell adhesion and bone ongrowth compared to uncoated titanium surfaces.

Assessment of cup position from plain radiographs: impact of pelvic tilting.

The acetabular cup position after total hip arthroplasty (THA) regarding its inclination and version angles are influential parameters concerning the postoperative range of motion and dislocation stability. Standard anterior-posterior X-rays remain an important diagnostic instrument to observe the postoperative outcome and to secure quality control after THA, where an optimal positioning of the patient is recommended when taking these X-rays. The purpose of this preliminary study was to determine the effect of pelvic tilting regarding the positioning calculation of the acetabular cup from standard radiographs using a modified method according to Pettersson et al. (Acta Radiol Diagn, 23:259–263, 1982). In our model experiment, we were able to show that pelvic tilting to either side causes a considerable difference between the radiographic and calculated version angles following approximately linear functions. However, pelvic tilting to either side, leads, regarding the calculation of the inclination, to an average deviation between radiographic and calculated inclination angles less than 2°.

Analysis of the Release Characteristics of Cu-Treated Antimicrobial Implant Surfaces Using Atomic Absorption Spectrometry

New developments of antimicrobial implant surfaces doped with copper (Cu) ions may minimize the risk of implant-associated infections. However, experimental evaluation of the Cu release is influenced by various test parameters. The aim of our study was to evaluate the Cu release characteristics in vitro according to the storage fluid and surface roughness. Plasma immersion ion implantation of Cu (Cu-PIII) and pulsed magnetron sputtering process of a titanium copper film (Ti-Cu) were applied to titanium alloy (Ti6Al4V) samples with different surface finishing of the implant material (polished, hydroxyapatite and corundum blasted). The samples were submersed into either double-distilled water, human serum, or cell culture medium. Subsequently, the Cu concentration in the supernatant was measured using atomic absorption spectrometry. The test fluid as well as the surface roughness can alter the Cu release significantly, whereby the highest Cu release was determined for samples with corundum-blasted surfaces stored in cell medium.

A Model of Implant-Associated Infection in the Tibial Metaphysis of Rats

Objective. Implant-associated infections remain serious complications in orthopaedic and trauma surgery. A main scientific focus has thus been drawn to the development of anti-infective implant coatings. Animal models of implant-associated infections are considered helpful in the in vivo testing of new anti-infective implant coatings. The aim of the present study was to evaluate a novel animal model for generation of implant-associated infections in the tibial metaphysis of rats. Materials and Methods. A custom-made conical implant made of Ti6Al4V was inserted bilaterally at the medial proximal tibia of 26 female Sprague-Dawley rats. Staphylococcus aureus in amounts spanning four orders of magnitude and each suspended in 15 μl phosphate buffered saline (PBS) was inoculated into the inner cavity of the implant after the implantation into the defined position. Controls were treated accordingly with PBS alone. Animals were then followed for six weeks until sacrifice. Implant-associated infection was evaluated by microbiological investigation using swabs and determination of viable bacteria in the bone around the implant and the biofilm on the implants after sonification. Results. Irrespective of the initial inoculum, all animals in the various groups harbored viable bacteria in the intraoperative swabs as well as the sonication fluid of the implant and the bone samples. No correlation could be established between initially inoculated CFU and population sizes on implant surfaces at sacrifice. However, a significantly higher viable count was observed from peri-implant bone samples for animals inoculated with 106 CFU. Macroscopic signs of animal infection (pus and abscess formation) were only observed for implants inoculated with at least 105 CFU S. aureus. Discussion/Conclusion. The results demonstrate the feasibility of this novel animal model to induce an implant-associated infection in the metaphysis of rats, even with comparatively low bacterial inocula. The specific design of the implant allows an application of bacteria in reproducible numbers at well-defined contact sites to the animal bone.

Accuracy and reliability of different methods to evaluate the acetabular cup version from plain radiographs

PurposeThe purpose of this study was to compare different methods of evaluating the version of a metallic acetabular cup from plain radiographs and to compare them regarding their accuracy, inter- and intra-observer reliability.MethodsConventional anterior–posterior radiographs were taken of a phantom-model at different defined ante- and retroversion angles of the acetabular cup. The version angles of the acetabular cup were derived according to four different established methods from the radiographs by five independent examiners.ResultsWe were able to determine the radiographic version with the greatest accuracy according to a modified technique of Pettersson et al. Furthermore, we found the highest intra- and inter-observer reliability using this technique.ConclusionsA modified technique of Pettersson et al. broadens the spectrum of applicability for the radiographic evaluation of the version angle of metal-backed acetabular cups in comparison to the originally introduced method. In clinical practice, however, the significance of deriving the cup position from standard radiographs should not be over-estimated and therefore a computed tomography should be performed in certain critical cases.

Bony integration of titanium implants with a novel bioactive calcium titanate (Ca4Ti3O10) surface treatment in a rabbit model

Nowadays total joint replacement is an indispensable component of modern medicine. The surfaces characteristics of cementless prostheses may be altered to achieve an accelerated and enduring bony integration. Classic surface coatings bear the risk of loosening or flaking from the implant body. This risk is excluded by the chemical conversion of the naturally existing TiO(2) surface layer into calcium titanate. The aim of this experimental animal study was to investigate the bony integration of implants with a new calcium titanate surface (Ca(4)Ti(3)O(10)) compared with a conventional standard Ti6Al4V surface. Cylindrical implants, made of titanium alloy (Ti6Al4V) were implanted in both lateral femoral condyles of New Zealand white rabbits. In each animal, an implant with and without surface treatment was inserted in a blinded manner. Animals were sacrificed after 4, 12, and 36 weeks, respectively. The axial pull-off forces were determined for 25 animals using a universal testing machine (Zwick Z010, Ulm, Germany). Furthermore, a histological analysis of the bony integration of the implants was performed in 12 specimens. In general, the pull-off forces for untreated and treated implants increased with longer survival times of the rabbits. No significant difference could be shown after 4 weeks between treated and untreated implants. After 12 weeks, the treated implants revealed a statistical significant higher pull-off force. After 36 weeks, the pull-off forces for treated and untreated implants aligned again. Titanium implants treated with calcium titanate, may offer an interesting and promising implant surface modification for endoprosthetic implants. They might lead to an accelerated osseointegration of total hip and knee replacements.

[Periprosthetic infections following total hip replacement with ESBL-forming bacteria: importance for clinical practice].

Implant infections remain feared and severe complications after total hip replacement. An even higher rate of periprosthetic infections can be observed after revision surgery in comparison to primary total hip replacement. An additional threat for patients with artificial joints arises from the fact that bacteria resistant to a multitude of antibiotics are encountered with increasing frequency in the hospital setting.Among these the enterobacteria producing extended spectrum β-lactamases (ESBL) are the second most frequent group of multiresistant pathogens. ESBLs are enzymes which possess the ability to hydrolyse third and fourth generation cephalosporins resulting in a distinctive resistance against these antibiotics. Even though ESBLs were first described in the early 1980s and now represent pathogens of utmost importance in intensive care units, they have been hardly considered in orthopedic and trauma surgery.In the present manuscript we provide an overview of the epidemiology and diagnostics of ESBL-expressing bacteria and demonstrate the difficulties in managing implant-associated infections with resistant bacteria. Furthermore, we emphasize the importance of recognizing ESBL-positive bacteria as increasingly important pathogens which require special precautions and treatment. Clinical evaluations suggest that ESBLs in orthopedic and trauma surgery are not a rare phenomenon any more.ZusammenfassungPeriprothetische Infektionen stellen eine gefürchtete Komplikation nach endoprothetischem Hüftgelenkersatz dar. Ein gesteigertes Infektionsrisiko besteht nach Wechseloperationen im Vergleich zur primären Implantation einer Hüftendoprothese. Weiterhin stellen die zunehmenden Resistenzen von Hospitalkeimen eine zusätzliche Bedrohung für den Patient und die endoprothetische Versorgung dar.Extended-spectrum-β-Laktamase- (ESBL-)bildende Enterobakterien sind unter den multiresistenten Hospitalismuskeimen die am zweithäufigsten gefundenen Erreger. ESBL sind bakterielle Enzyme, welche die Fähigkeit besitzen, Cefalosporine der dritten und vierten Generation zu hydrolysieren und zur Ausbildung entsprechender Resistenzen beizutragen. Obwohl ESBL-bildende Bakterien bereits in den frühen 1980er Jahren erstmals beschrieben wurden, fanden sie bisher kaum spezifische Beachtung in der Orthopädie und Unfallchirurgie.Im vorliegenden Artikel geben wir einen Überblick zur Epidemiologie und Diagnose von ESBL-Bildnern und zeigen die Schwierigkeiten bei der Behandlung periprothetischer Infektionen mit multiresistenten Bakterien auf. Weiterhin werden die im Zusammenhang mit ESBL-Bildnern besonderen hygienischen Maßnahmen und Therapieformen vorgestellt. Aufgrund eigener Erhebungen gehen wir davon aus, dass Infektionen mit ESBL-produzierenden Bakterien in der Orthopädischen Chirurgie keine Seltenheit mehr darstellen.AbstractImplant infections remain feared and severe complications after total hip replacement. An even higher rate of periprosthetic infections can be observed after revision surgery in comparison to primary total hip replacement. An additional threat for patients with artificial joints arises from the fact that bacteria resistant to a multitude of antibiotics are encountered with increasing frequency in the hospital setting.Among these the enterobacteria producing extended spectrum β-lactamases (ESBL) are the second most frequent group of multiresistant pathogens. ESBLs are enzymes which possess the ability to hydrolyse third and fourth generation cephalosporins resulting in a distinctive resistance against these antibiotics. Even though ESBLs were first described in the early 1980’s and now represent pathogens of utmost importance in intensive care units, they have been hardly considered in orthopedic and trauma surgery.In the present manuscript we provide an overview of the epidemiology and diagnostics of ESBL-expressing bacteria and demonstrate the difficulties in managing implant-associated infections with resistant bacteria. Furthermore, we emphasize the importance of recognizing ESBL-positive bacteria as increasingly important pathogens which require special precautions and treatment. Clinical evaluations suggest that ESBLs in orthopedic and trauma surgery are not a rare phenomenon any more.

In vivo monitoring of implant osseointegration in a rabbit model using acoustic sound analysis.

Implant osseointegration can currently only be assessed reliably post mortem. A novel method that relies on the principle of acoustic sound analysis was developed to enable examination of the longitudinal progress of osseointegration. The method is based on a magnetic sphere inside a hollow cylinder of the implant. By excitation using an external magnetic field, collision of the sphere inside the implant produces a sound signal. Custom‐made titanium implants equipped thusly were inserted in each lateral femoral epicondyle of 20 New Zealand White Rabbits. Two groups were investigated: Uncoated, machined surface versus antiadhesive surface; and calcium phosphate‐coated surface versus antiadhesive surface. The sound analysis was performed postoperatively and weekly. After 4 weeks, the animals were euthanized, and the axial pull‐out strengths of the implants were determined. A significant increase in the central frequency was observed for the loose implants (mean pull‐out strength 21.1 ± 16.9 N), up to 6.4 kHz over 4 weeks. In comparison, the central frequency of the osseointegrated implants (105.2 ± 25.3 N) dropped to its initial value. The presented method shows potential for monitoring the osseointegration of different implant surfaces and could considerably reduce the number of animals needed for experiments.

Quantification of osseointegration of plasma-polymer coated titanium alloyed implants by means of microcomputed tomography versus histomorphometry.

A common method to derive both qualitative and quantitative data to evaluate osseointegration of implants is histomorphometry. The present study describes a new image reconstruction algorithm comparing the results of bone-to-implant contact (BIC) evaluated by means of µCT with histomorphometry data. Custom-made conical titanium alloyed (Ti6Al4V) implants were inserted in the distal tibial bone of female Sprague-Dawley rats. Different surface configurations were examined: Ti6Al4V implants with plasma-polymerized allylamine (PPAAm) coating and plasma-polymerized ethylenediamine (PPEDA) coating as well as implants without surface coating. After six weeks postoperatively, tibiae were explanted and BIC was determined by µCT (3D) and afterwards by histomorphometry (2D). In comparison to uncoated Ti6Al4V implants demonstrating low BIC of 32.4% (histomorphometry) and 51.3% (µCT), PPAAm and PPEDA coated implants showed a nonsignificant increase in BIC (histomorphometry: 45.7% and 53.5% and µCT: 51.8% and 62.0%, resp.). Mean BIC calculated by µCT was higher for all surface configurations compared to BIC detected by histomorphometry. Overall, a high correlation coefficient of 0.70 (p < 0.002) was found between 3D and 2D quantification of BIC. The μCT analysis seems to be suitable as a nondestructive and accurate 3D imaging method for the evaluation of the bone-implant interface.