Browsing by Author "Narayanan, Ajay"
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Item Exploring a Novel, Non-Invasive Treatment for Prosthetic Joint Infection(2018-01-23) Narayanan, Ajay; Wang, Qi; Pybus, Christine; Shaikh, Sumbul; Munaweera, Imalka; Sturge, Carolyn; Chopra, Rajiv; Greenberg, DavidPeriprosthetic joint infection (PJI) is a very prevalent consequence of implant surgery. The surface of the prosthesis provides a favorable environment for the growth of bacterial biofilms, which are notorious for being resistant to conventional antibiotics. The current treatment for PJI involves re-opening the surgical site and replacing the prosthesis, a very costly procedure that diminishes patient quality of life. Recently, a non-invasive procedure has been developed that utilizes high frequency alternating magnetic fields (AMF) to destroy biofilms via induction heating. Our research was focused on both optimizing and further characterizing the cytotoxicity of this treatment method on Staphylococcus aureus and Pseudomonas aeruginosa, two biofilm-forming pathogens commonly implicated in PJI. The organisms used for these experiments were Staphylococcus aureus and Pseudomonas aeruginosa. Biofilms were grown on stainless steel rings or washers, to model the surface of implanted prosthetics. P. aeruginosa was grown statically in MH2 media at 37°C for 48 hours. S. aureus was grown statically in Tryptic Soy Broth media supplemented with 0.5% glucose and 3.0% NaCl at 37°C for 48 hours. Soaking the stainless steel ring/washer in a 20% Human Plasma solution overnight at 4°C greatly enhanced S. aureus biofilm formation. AMF continuous dosing was performed at 20 watts, up to 15 minutes. AMF intermittent dosing was performed using 1 second duration, 670 watt pulses every 10 minutes, up to 6 hours. The results indicated that S. aureus biofilms were eradicated more effectively than P. aeruginosa biofilms when treated with intermittent AMF exposure. Specifically, there was a 2.6-log reduction in S. aureus biofilm CFU after 30 minutes of AMF exposure, with CFUs reaching the limit of detection after 3 hours. Corresponding studies in P. aeruginosa showed a 1.3-log reduction in biofilm CFU after 30 minutes of AMF exposure, with CFUs not reaching the limit of detection after 6 hours. In an ongoing study, ciprofloxacin was administered alongside AMF exposure to investigate any potential synergistic effects on P. aeruginosa biofilm eradication. While the data produced this summer was exclusively in vitro, the results give insight on how AMF might be applied in the clinical treatment of PJI. The observed cytotoxicity combined with the non-invasive nature of AMF suggest significant promise for a much more desired method of PJI treatment for common pathogens.Item Subcutaneous Fat Thickness as a Risk Factor for Return to OR in Total Knee Arthroplasties(2018-01-23) Prabhakar, Pooja; Narayanan, Ajay; Swann, Matthew; Estrera, KennethBACKGROUND: Total knee arthroplasty (TKA) is an increasingly common procedure performed in the United States. Post-operative complications after TKA, such as unplanned returns to the operating room for an infection or implant failure, can result in high morbidity for patients. Presently, several patient factors are used to identify higher risk patients prior to surgery, such as body mass index (BMI), although these have limitations. However, the amount of subcutaneous tissue at the surgical site affords an objective evaluation of the degree of surgical exposure required at the time of the operation. Increased amounts of subcutaneous tissue may lead to a prolonged dissection, which may increase rates of infection, which could result in unplanned returns to the OR. The aim of this study is to determine whether subcutaneous fat thickness as measured on pre-operative radiographs is a risk factor for return to OR for TKAs. METHODS: This is an IRB-approved, retrospective review of a series of 596 total knee arthroplasties at two hospitals in a large urban setting over a 2-year period (2010-2011). Pre-operative AP knee radiographs were reviewed and measurements were taken using the same imaging software. A medial knee adipose tissue (MKAT) score was calculated using the ratio of the total width of the distal femoral metaphysis perpendicular to the anatomic axis and the width of the medial adipose tissue along the same plane. Additional variables recorded included gender, ethnicity, diagnosis, laterality, pre-operative BMI, date of last follow-up, return to OR, revision, and deceased status. RESULTS: 596 patients were included in the analysis, of which 24 patients (4%) had an unplanned return to the OR within 3 months of the index operation. In this group, the average pre-op BMI was 32.9 and the average MKAT score was 0.46. The MKAT score was not significantly associated with return to OR (p = 0.15). Age and BMI were the only variables that were significantly associated with return to OR (p = 0.01 and 0.005). CONCLUSIONS: MKAT scores on pre-operative AP knee radiographs are not significantly associated with increased return to OR after primary TKA. The limitations of this study include its retrospective nature and small study population. Although we did not find a statistically significant difference between the two groups, this data is useful in that it can assist with surgical decision making. This data suggests that patients with increased subcutaneous tissue about the knee are not at increased risk of return to the OR after primary TKA.