News and Research




Bacterial Biofilms on Electrochemically Active Cathodic Titanium Surfaces

Jin Guo

Bacterial infection is a major concern in orthopedic implants that may lead to implant failure and revision. The resistance of bacterial biofilms to antibiotics increases the difficulties of fighting against infections. In this work, the effects of electrochemical reduction reactions on bacterial biofilm cultured on electrochemically active metal surfaces were investigated to better understand the mechanism of bacterial response to reduction electrochemistry. The influence of voltage and electrolyte were studied on the cellular behavior of E. coli HM22 cultured on commercially pure titanium (cpTi) surfaces held at cathodic voltages. Relatively weak potentials at -1 V (vs. Ag/AgCl) could significantly reduce the cell viability in saline solution after 24 hours compared to controls at open circuit potential (OCP, in the range of -0.2 V to -0.38 V vs. Ag/AgCl) (p < 0.05). However, bacterial biofilms cultured on cpTi surfaces in LB media require more negative voltage (below -1.2 V) to induce significant killing efficacy. On the other hand, the cellular response was correlated with the electrochemical properties of titanium-oxide-solution interface through methods like electrochemical impedance spectroscopy (EIS) and current density monitoring. The electrochemical impedance of the oxide-bacteriasolution interface was dependent on the presence of applied voltage. Sustained voltage treatment at -1 V decreased the impedance of titanium-oxide-bacteria interface in both LB media and NaCl solution at 0.1 Hz than those at OCP (p<0.05). In LB media, the presence of bacterial biofilm significantly reduced the average current density experienced by cpTi surfaces at -1 V compared to controls without cells at -1 V in 24 hours (p < 0.05). Significant morphological changes were found after voltage treatment in NaCl solution and LB media. In general, ruptured cells after voltage treatment at -1 V in NaCl solution ended in less length, width and height than control cells at OCP (p<0.05). The applied potential at -1 V decreased the length and height of all the cells in LB media after time-lapse photography compared to those of untreated controls (p<0.05). Finally, time-lapse photography, which could assess cellular movement of bacteria under voltage treatment in real time, was utilized and proved to be an effective method of cellular investigation besides LIVE/DEAD assay, scanning electron microscope (SEM) and atomic force microscopy (AFM). Average bacterial cell velocity significantly increased once -1 V voltage treatment started and then dropped in two hours in NaCl solution (p<0.05), while no such difference was seen during the test in LB media.




New cosurface capacitive stimulators for the development of active osseointegrative implantable devices

Marco P. Soares dos Santos1,2,* , Ana Marote3,* , T. Santos4, JoãoTorrão2, A. Ramos1,2, JoséA. O. Simões2, OdeteA. B. daCruz e Silva3, Edward P. Furlani5,6, Sandra I.Vieira3,† & JorgeA. F. Ferreira1,2,†

Non-drug strategies based on biophysical stimulation have been emphasized for the treatment and prevention of musculoskeletal conditions. However, to date, an effective stimulation system for intracorporeal therapies has not been proposed. This is particularly true for active intramedullary implants that aim to optimize osseointegration. The increasing demand for these implants, particularly for hip and knee replacements, has driven the design of innovative stimulation systems that are effective in bone-implant integration. In this paper, a new cosurface-based capacitive system concept is proposed for the design of implantable devices that deliver controllable and personalized electric field stimuli to target tissues. A prototype architecture of this system was constructed for in vitro tests, and its ability to deliver controllable stimuli was numerically analyzed. Successful results were obtained for osteoblastic proliferation and differentiation in the in vitro tests. This work provides, for the first time, a design of a stimulation system that can be embedded in active implantable devices for controllable bone-implant integration and regeneration. The proposed cosurface design holds potential for the implementation of novel and innovative personalized stimulatory therapies based on the delivery of electric fields to bone cells. 




What Are the Rates and Causes of Hospital Readmission After Total Knee Arthroplasty?

William W. Schairer, BA, Thomas P. Vail, MD, and Kevin J. Bozic, MD, MBA


Total knee arthroplasty (TKA) and related interventions such as revision TKA and the treatment of infected TKAs are commonly performed procedures. Hospital readmission rates are used to measure hospital performance, but risk factors (both medical and surgical) for readmission after TKA, revision TKA, and treatment for the infected TKA have not been well characterized.


We measured (1) the unplanned hospital readmission rate in primary TKA and revision TKA, including antibiotic-spacer staged revision TKA to treat infection. We also evaluated (2) the medical and surgical causes of readmission and (3) risk factors associated with unplanned hospital readmission.


This retrospective cohort study included a total of 1408 patients (1032 primary TKAs, 262 revision TKAs, 113 revision of infected TKAs) from one institution. All hospital readmissions within 90 days of discharge were evaluated for timing and cause. Diagnoses at readmission were categorized as surgical or medical. Readmission risk was assessed using a Cox proportional hazards model that incorporated patient demographics and medical comorbidities.


The unplanned readmission rate for the entire cohort was 4% at 30 days and 8% at 90 days. At 90 days postoperatively, revision of an infected TKA had the highest readmission rate, followed by revision TKA, with primary TKA having the lowest rate. Approximately three-fourths of readmissions were the result of surgical causes, mostly infection, arthrofibrosis, and cellulitis, whereas the remainder of readmissions were the result of medical causes. Procedure type (primary TKA versus revision TKA or staged treatment for infected TKA), hospital stay more than 5 days, discharge destination, and a fluid/electrolyte abnormality were each associated with risk of unplanned readmission.


Patients having revision TKA, whether for infection or other causes, are more likely to have an unplanned readmission to the hospital than are patients having primary TKA. When assessing hospital performance for TKA, it is important to distinguish among these surgical procedures. 




Periprosthetic joint infection: Current concept

Vinay K Aggarwal, Mohammad R Rasouli, and Javad Parvizi

Periprosthetic joint infection (PJI) is one of the most devastating and costly complications following total joint arthroplasty (TJA). Diagnosis and management of PJI is challenging for surgeons. There is no “gold standard” for diagnosis of PJI, making distinction between septic and aseptic failures difficult. Additionally, some of the greatest difficulties and controversies involve choosing the optimal method to treat the infected joint. Currently, there is significant debate as to the ideal treatment strategy for PJI, and this has led to considerable international variation in both surgical and nonsurgical management of PJI. In this review, we will discuss diagnosis and management of PJI following TJA and highlight some recent advances in this field. 




Electrical stimulation may offer alternative to antibiotics for wound treatment

by Catharine Paddock PhD

Researchers have developed a way of using electrical stimulation in wound dressing that may offer an effective alternative to antibiotics. They found their approach nearly eliminated all of a multi-drug-resistant bacterium that is often found in infections that are hard to treat. 




The Effect of pH on the Extracellular Matrix and Biofilms

Eleri M. Jones,1 Christine A. Cochrane,1 and Steven L. Percival

Significance: Chronic wounds become caught in a state of inflammation causing an increase in levels of degrading proteases, which destroy components of the extracellular matrix (ECM) that are essential for the wound healing process. This review aims to highlight and provide readers with an overview of what is currently known about the role of pH and its effect on the ECM and biofilms within healing and nonhealing wounds.

Recent Advances: The pH profiles of healthy skin, acute wounds, and chronic wounds differ significantly. Chronic wounds have an alkaline pH whereas healthy skin has a slightly acidic pH. Although there is evidence on the effect of pH on protease production and bacterial proliferation in wounds, there is little evidence to show its effect on ECM synthesis and degradation.

Critical Issues: The implications for the complex nature of chronic wounds are that no single treatment is relevant for all wounds, but rather a combination of methodologies must be adopted. It is known that pH of a wound reduces throughout the stages of healing, suggesting that wound pH measurements could be beneficial to identify nonhealing wounds earlier and decide on the most appropriate course of treatment.

Future Direction: Wound healing is a very complex process with multiple factors known to play a role. All aspects of the nonhealing wound (defective ECM, pH, microbial invasion, and excess proteases) need to be taken into account when investigating or clinically treating a chronic wound. Full Article >>




Chronic Wound Biofilm Model

Kasturi Ganesh, Mithun Sinha, Shomita S. Mathew-Steiner, Amitava Das, Sashwati Roy, and Chandan K. Sen

Significance: Multispecies microbial biofilms may contribute to wound chronicity by derailing the inherent reparative process of the host tissue. In the biofilm form, bacteria are encased within an extracellular polymeric substance and become recalcitrant to antimicrobials and host defenses. For biofilms of relevance to human health, there are two primary contributing factors: the microbial species involved and host response which, in turn, shapes microbial processes over time. This progressive interaction between microbial species and the host is an iterative process that helps evolve an acute-phase infection to a pathogenic chronic biofilm. Thus, long-term wound infection studies are needed to understand the longitudinal cascade of events that culminate into a pathogenic wound biofilm.

Recent Advances: Our laboratory has recently published the first long-term (2 month) study of polymicrobial wound biofilm infection in a translationally valuable porcine wound model.

Critical Issues: It is widely recognized that the porcine system represents the most translationally valuable approach to experimentally model human skin wounds. A meaningful experimental biofilm model must be in vivo, include mixed species of clinically relevant microbes, and be studied longitudinally long term. Cross-validation of such experimental findings with findings from biofilm-infected patient wounds is critically important. 

Future Directions: Additional value may be added to the experimental system described above by studying pigs with underlying health complications (e.g., metabolic syndrome), as is typically seen in patient populations. Full Article >>