Implant infection is an increasing problem in orthopedic surgery, especially due to progressive antibiotic resistance and an aging population with rising numbers of implantations. As a consequence, new strategies for infection prevention are necessary. In the previous study it was hypothesized that laser-structured implant surfaces favor cellular adhesion while hindering bacterial ongrowth and therewith contribute to reduce implant infections. Cuboid titanium implants (0.8 × 0.8 × 12 mm³, n=34) were used. Seventeen were laser-structured by ultra-short pulsed laser ablation to create a spike structure; the others were polished and served as controls. In general anesthesia, implants were inserted in rat tibiae and infected with a S. aureus suspension. During a 21 day postoperative follow-up, daily clinical control was performed. Radiographs were taken at day 14 and day 21. After euthanasia, bacterial load and biofilm formation on the implant surface was evaluated semi quantitatively by confocal laser scanning microscopy and computational acquisition of bacteria and cells by Imaris®-software. Additionally, histology of the surrounding bone was performed. Clinically, no differences were observed between the groups. However, contrary to our hypothesis, bacterial load was increased in the laser-structured implant group although cellular adhesion was even more pronounced. Radiographical and histological evaluations showed increased bone alterations in the group with laser-structured implants compared to the control group. These findings did not confirm prior in vitro studies, where a reduction of bacterial load was found for similar surfaces and demonstrate the necessity of in vivo trials prior to the clinical use of new materials.

Aim

The aim of this study was to establish an implant-associated osteomyelitis model in rats with the ability to quantify biofilm formation on implants for prospective evaluation of antibacterial effects on micro-structured implant surfaces.

Understanding the cause of failure of total knee arthroplasties (TKA) is essential in guiding clinical decision making and adjusting treatment concepts for revision surgery. The purpose of the study was to determine current mechanisms of failure of TKA and to describe changes and trends in revision surgery over the last 10 years.

A retrospective review was done on all patients who had revision total knee arthroplasty during a 10-year period (2000–2009) at one institution. The preoperative evaluation in conjunction with the intraoperative findings was used to determine causes of failure. All procedures were categorizes as Sharkey et al. described previously. The data was analyzed regarding the cause of failure and displaying the incidence and trends over the last 10 years.

1225 surgeries were done in the time period with a steady increase of procedures per year (34 procedures in 2000 to 196 in 2009). The most common cause of revision TKA was aseptic failure in 65% and septic failure in 31% of the reviewed cases. However, we could observe a steady proportional increase of the septic classified revisions over the time. Both categories could be subdivided to specific causes of failure including aseptic loosening (24%), anterior knee pain (20%), instability (6,4%), arthrofibrosis (4,9%), PE wear (3,6%), malpositioning/malrotation (2,7%) periprosthetic fracture (2,0%) and other (4,6%), or in early (12,9%), late (15,4%) or low-grade infection (3,3%), respectively. Complementary to the classification Sharkey et al. described in 2002 we identified new subcategories of failure: malrotation (since 2003), Low-Grade-Infection (since 2006), allergic failure/loosening (since 2006), Mid-Flexion-Instability (since 2007), soft tissue impingement (since 2009). The incidence of the classic aseptic loosening due to PE wear shows a clear decrease in the last 10 years whereas we could observe an increase of the new diagnosis of instability, malrotation or low-grade-infection as determined cause of failure.

The detailed analysis of the failure mechanism in total knee arthroplasty is important to understand the clinical problem and to adjust treatment strategies. We were able to complement present classifications and give a first overview on the incidence for specific causes of failure. Our data shows changes in the indication for surgery over the time and compared to the collective of Sharkey et al. from 1997–2000. This might be due to new diagnostic methods and better implant materials as well as to a generally increased awareness of the specific mechanism of TKA failure.