Martin Ellenrieder

Evaluation of electric field distribution in electromagnetic stimulation of human femoral head.

Electromagnetic stimulation is a common therapy used to support bone healing in the case of avascular necrosis of the femoral head. In the present study, we investigated a bipolar induction screw system with an integrated coil. The aim was to analyse the influence of the screw parameters on the electric field distribution in the human femoral head. In addition, three kinds of design parameters (the shape of the screw tip, position of the screw in the femoral head, and size of the screw insulation) were varied. The electric field distribution in the bone was calculated using the finite element software Comsol Multiphysics. Moreover, a validation experiment was set up for an identical bone specimen with an implanted screw. The electric potential of points inside and on the surface of the bone were measured and compared to numerical data. The electric field distribution within the bone was clearly changed by the different implant parameters. Repositioning the screw by a maximum of 10 mm and changing the insulation length by a maximum of 4 mm resulted in electric field volume changes of 16% and 7%, respectively. By comparing the results of numerical simulation with the data of the validation experiment, on average, the electric potential difference of 19% and 24% occurred when the measuring points were at a depth of approximately 5 mm within the femoral bone and directly on the surface of the femoral bone, respectively. The results of the numerical simulations underline that the electro-stimulation treatment of bone in clinical applications can be influenced by the implant parameters.

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.

Spondylodiscitis of the lumbar spine in a non-immunocompromised host caused by Yersinia enterocolitica O:9

Here presented is an extremely rare case of a spinal osteomyelitis (L5–S1) with epidural empyema in a non-immunocompromised 62-year-old man caused by Yersinia enterocolitica O:9. The infection occurred acutely and required immediate surgical treatment. Y. enterocolitica was cultured from the empyema fluid, wound swabs of the intervertebral disc L5–S1 and stool cultures. Following the surgical decompression and antibiotic treatment, the patient recovered completely, without neurological deficits. A review of the literature revealed only sparse cases of spondylodiscitis due to other Y. enterocolitica serogroups. To our knowledge, we report here the first case of a spondylodiscitis of the lumbar spine caused by Y. enterocolitica serovar O:9 in a non-immunocompromised patient.

Periprothetische Infektionen nach Hüfttotalendoprothese mit ESBL-bildenden Bakterien

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.

Prospective comparative clinical study of ceramic and metallic femoral components for total knee arthroplasty over a five-year follow-up period

BACKGROUND The aim of this prospective comparative study was to evaluate the clinical and radiological outcomes of a TKA system, comparing a ceramic (BIOLOX® delta) and metallic (Co28Cr6Mo) femoral component over a five-year follow-up period. METHODS Forty-three TKA patients (17 metallic and 26 ceramic femoral components) were enrolled in the study. Clinical and radiological evaluations were performed preoperatively and at three, 12, 24 and 60months postoperatively, using the HSS-, WOMAC- and SF36-Scores, in addition to standardized X-rays. RESULTS The HSS-Score improved significantly from 58.7±12.7 points preoperatively to 88.5±12.3 points at five-years postoperative in the ceramic group, and 60.8±7.7 to 86.2±9.4 points in the metallic group. WOMAC- and SF-36-Scores showed significant improvement over time in both groups. There were no significant differences between groups for HSS-, WOMAC- and SF-36-Scores, nor for range of motion (p≤0.897) at any follow-up evaluation. Furthermore, radiological evaluation showed no implant loosening or migration in either group. CONCLUSIONS Mid-term outcomes for the ceramic femoral components demonstrated good clinical and radiological results, as well as comparable survivorship to the metallic femoral component of the same total knee system, and to other commonly used metallic total knee systems. Therefore, ceramic knee implants may be a promising solution for the population of patients with osteoarthritis and metal sensitivity. Long-term studies are required in order to confirm the positive mid-term clinical results, and to follow the implant survival rate in regard to the enhanced wear resistance of ceramic implants.

Treatment of acetabular defects during revision total hip arthroplasty - preliminary clinical and radiological outcome using bone substitute materials

Acetabular defects are a particular challenge during THR revision. Defects may be filled with autologous bone grafts, allografts or synthetic bone substitute materials. In this preliminary, retrospective study, 22 patients were treated with an oval shaped revision cup and a combination of synthetic bone substitute materials, namely hydroxyapatite and beta-tricalcium phosphate. The postoperative outcome was evaluated regarding the functional clinical outcome and quality of life using the Harris hip score, the WOMAC and the SF-36. Signs of loosening and changes of the implant position were evaluated from plain radiographs. Follow up examinations were performed after an average duration of 20.5 months (7-33 months). Postoperatively, we found a significant increase of the Harris hip score, and an increase in both the SF-36 and the WOMAC scores (without statistical significance). No radiographic signs of loosening were evident at the time of follow up. The use of synthetic bone substitute materials offers a possible alternative to the use of autologous and allogenic bone grafts in acetabular revision surgery. Further randomised controlled long-term studies are needed to verify the promising short-term results and to determine potential side effects, such as possible third body wear.

Bacteriology swabs in primary total knee arthroplasty

Objective: An early detection of possible periprosthetic infection may lead to an earlier and potentially less invasive treatment of infected total knee arthroplasty TKA). The purpose of the present study was to evaluate retrospectively our current, affordable clinical practice of intra-operative swab taking during primary TKA. Methods: A total of 206 primary TKA were analysed retrospectively for intra-operative bacteriology swabs and subsequent periprosthetic infection. All bacteriology swabs were obtained in a standardized manner including a tissue sample. Data was statistically evaluated concerning standard descriptive statistics and using the chi-square test. Results: Bacteria were identified in 43.4% with coagulase-negative staphylococci being the most frequently isolated pathogens (52.2%). Regarding the contingency tables and chi-squared tests, generally no association was found between positive intra-operative swabs and subsequent periprosthetic infection as well as all other parameters investigated (timing of the antibiotic prophylaxis and pre-operative laboratory results). Conclusions: Bacteriology swabs during primary total knee arthroplasty are no adequate measure to predict subsequent periprosthetic infections, even if augmented with a tissue sample.

Two-stage revision of implant-associated infections after total hip and knee arthroplasty

Septic loosening of total hip and knee endoprostheses gains an increasing proportion of revision arthroplasties. Operative revisions of infected endoprostheses are mentally and physically wearing for the patient, challenging for the surgeon and a significant economic burden for healthcare systems. In cases of early infection within the first three weeks after implantation a one-stage revision with leaving the implant in place is widely accepted. The recommendations for the management of late infections vary by far. One-stage revisions as well as two-stage or multiple revision schedules have been reported to be successful in over 90% of all cases for certain patient collectives. But implant associated infection still remains a severe complication. Moreover, the management of late endoprosthetic infection requires specific logistics, sufficient and standardized treatment protocol, qualified manpower as well as an efficient quality management. With regard to the literature and experience of specialized orthopaedic surgeons from several university and regional hospitals we modified a commonly used treatment protocol for two-stage revision of infected total hip and knee endoprostheses. In addition to the achievement of maximum survival rate of the revision implants an optimisation of the functional outcome of the affected artificial joint is aimed for.