Successful Two-Stage Exchange Arthroplasty for Periprosthetic Infection Following Total Knee Arthroplasty: The Impact of Timing on Eradication of Infection

Background: Periprosthetic joint infection (PJI) represents a serious complication following total knee arthroplasty. In the setting of chronic infections, the two-staged approach has traditionally been the preferred treatment method. The aim of this study was to determine the optimal period of rest between the first and second stage. Furthermore, we analyzed potentially outcome-relevant parameters, such as general and local conditions and the presence of difficult-to-treat or unidentified microorganisms, with regard to their impact on successful treatment of PJI.Patients and Methods: We performed a retrospective analysis of prospectively collected data for all patients treated for PJI at our institution. Seventy-seven patients who had undergone two-stage revision arthroplasty for PJI of the knee were included into the study. Antibiotic-loaded cement spacers were used for all patients.Results: After a median follow-up time of 24.5 months, infection had reoccurred in 14 (18.7%) patients. A prolonged spacer-retention period of more than 83 days was related to a significantly higher proportion of reinfections. Furthermore, significant compromising local conditions of the prosthetic tissue and surrounding skin, as well as repeated spacer-exchanges between first- and second-stage surgery, negatively influenced the outcome. Neither the patients'' age nor gender exerted a significant influence on the outcome regarding reinfection rates for patients'' age or gender.Conclusions: We observed the best outcome regarding infection control in patients who had undergone second-stage surgery within 12 weeks after first-stage surgery. Nearly 90% of these patients stayed free from infection until the final follow-up. An increased number of performed spacer-exchanges and a bad local extremity grade also had a negative impact on the outcome.     

Atrial function in the Fontan circulation: comparison with invasively assessed systemic ventricular filling pressure

The International Journal of Cardiovascular Imaging - Abnormal atrial mechanics in biventricular circulations have been associated with elevated left heart filling pressures. Similar associations...     

Microstructure and long-term stability of solder joints on nickel-plated aluminium formed during short soldering times

Within this work, we demonstrate that an easy soldering process in combination with wet chemical coating is suitable to realize a strong and reliable solder interconnection of Al substrates, even at short soldering times <5 s in ambient air. The microstructure of solder joints on wet chemically treated aluminum foils is investigated. A single and double zincate pre-treatment are compared to activate the Al surface, followed by electroless Ni plating. The quality of the solderable Ni surface is characterized by contact angle measurements, yielding good wettability (<60°), which is also achieved after isothermally heating (250 °C) the Ni-coated Al foils for 100 min. The microstructure of the Sn62Pb36Ag2 solder joints is investigated by SEM and EDX of cross sections, directly after soldering as well as after isothermal aging at 85 °C. Under the used soldering conditions, with a soldering temperature at about 280 °C, diffusion zones <500 nm were identified. Nonetheless, high peel forces after soldering >5 N mm⁻¹ show stable values under aging conditions of 85 °C for 1000 hours. This could be correlated to a mixed fracture pattern, promoting the high adhesion due to the absence of a dominant failure mechanism.

High mechanical reliability of tin-based solder joints processed by joining copper and nickel-coated aluminium with short soldering times in ambient air.     

Intermittent PTH administration and mechanical loading are anabolic for periprosthetic cancellous bone

The purpose of this study was to determine the individual and combined effects on periprosthetic cancellous bone of intermittent parathyroid hormone administration (iPTH) and mechanical loading at the cellular, molecular, and tissue levels. Porous titanium implants were inserted bilaterally on the cancellous bone of adult rabbits beneath a loading device attached to the distal lateral femur. The left femur received a sham loading device. The right femur was loaded daily, and half of the rabbits received daily PTH. Periprosthetic bone was evaluated up to 28 days for gene expression, histology, and µCT analysis. Loading and iPTH increased bone mass by a combination of two mechanisms: (1) Altering cell populations in a pro‐osteoblastic/anti‐adipocytic direction, and (2) controlling bone turnover by modulating the RANKL‐OPG ratio. At the tissue level, BV/TV increased with both loading (+53%, p < 0.05) and iPTH (+54%, p < 0.05). Combined treatment showed only small additional effects at the cellular and molecular levels that corresponded to a small additive effect on bone volume (+13% compared to iPTH alone, p > 0.05). This study suggests that iPTH and loading are potential therapies for enhancing periprosthetic bone formation. The elucidation of the cellular and molecular response may help further enhance the combined therapy and related targeted treatment strategies. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:163–173, 2015.

     

Characterization of a ceramide-activated protein kinase: stimulation by tumor necrosis factor alpha.

Recent investigations have identified a signal-transduction system involving sphingomyelin and derivatives. In this paradigm, sphingomyelin hydrolysis by a sphingomyelinase generates ceramide, which may be converted to the protein kinase C inhibitor sphingosine or to ceramide 1-phosphate. Ceramide may have second-messenger function because it induces epidermal growth factor receptor phosphorylation, presumably on Thr-669 in A-431 cells. The present studies describe a kinase that may mediate ceramide action. With a 19-amino acid epidermal growth factor receptor peptide containing Thr-669, a membrane-bound activity that phosphorylated the peptide was detected in A-431 cells. Activity was linearly related to ATP (0.3-300 microM) and peptide concentration (0.02-1 mg/ml), possessed a physiologic pH optimum (pH 7.0-7.4), and was Mg(2+)-dependent. Other cations--Ca2+, Mn2+, and Zn(2+)--were ineffective. Natural and synthetic ceramide induced time- and concentration-dependent enhancement of kinase activity. Ceramide (0.5 microM) increased kinase activity 2-fold by 30 s, and activity remained elevated for at least 15 min. As little as 0.001 microM ceramide was effective, and 1 microM ceramide induced maximal phosphorylation. Sphingosine was similarly effective. Because tumor necrosis factor (TNF) alpha rapidly induces sphingomyelin hydrolysis to ceramide during monocytic differentiation of HL-60 cells, its effects on kinase activity were assessed. Kinase activity was increased 1.5-fold at 5 min and 2-fold at 2 hr in membranes derived from TNF-stimulated cells. The effective concentration range was 3 pM-30 nM TNF. Exogenous ceramide induced a similar effect. In sum, these studies demonstrate the existence of an unusual Mg(2+)-dependent ceramide-activated protein kinase that may mediate some aspects of TNF-alpha function.