Aspirin venous thromboembolism chemoprophylaxis is effective after revision arthroplasty for periprosthetic joint infection (MOS: Dr. Michael Flierl)
Summary: In this study, the rate of VTE in the postoperative setting of revision total joint arthroplasty for periprosthetic joint infection (PJI; only cases that met MSIS criteria were included) was investigated. Efficacy of different anticoagulation regimens was also assessed. In the 5-year study period, 232 cases of revision TJA for PJI were identified. Low-dose aspirin was used in 14 cases, high-dose aspirin was used in 87 cases, and other anticoagulation treatments were used in 131 cases. Of the 232 patients, 9% (n = 21) had a prior history of DVT, none of whom developed a new VTE during chemoprophylaxis treatment. The incidence of VTE after revision surgery was 6% (n=15; DVT=11, PE=4). VTE rates were not significantly different between the three anticoagulation regimen groups (p=0.835). When the aspirin groups were combined, VTE rates between aspirin and other treatments was not significant (p=0.642). Among culture-positive cases, there was a weak, positive correlation between VTE (DVT and/or PE) and postoperative length of stay (ρ=0.267, p<0.001); similarly, in culture-negative cases, there was a moderate, positive association between prior history of a DVT and postoperative length of stay (ρ=0.439, p=0.018). In this study population, both low-dose and high-dose aspirin demonstrated similar rates of VTE, compared to other anticoagulants, indicating that aspirin may be an effective form of chemoprophylaxis after revision arthroplasty for PJI.
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Antibacterial and osseointegrative efficacy of titania nanotube surfaces (MOS: Dr. Paul Fortin)
Summary: When periprosthetic infection (PJI) often occurs in patients who have undergone orthopaedic procedures, the complication can substantially increase patient care costs; specifically, PJI may lead to more clinic/hospital visits, multiple revision surgeries, long-term patient disability, and increased mortality. Previous studies have shown that titania nanotube (TiNT) surfaces demonstrate increased bone-implant contact (BIC), enhanced de novo bone formation, and greater implant pull-out forces than non-textured controls. This study evaluated in vitro antibacterial properties of TiNT surfaces, TiNT surfaces integrated with nanosilver (TiNT+Ag), and two current standard-of-care materials (titanium thermal plasma sprayed and titanium alloy surfaces; TPS and Ti, respectively). Following in vitro testing, New Zealand White rabbits received bilateral antegrade implantation of intramedullary tibial implants with one of the four surface types. One tibia received a human clinical isolate of MRSA (105 CFU/mL) suspended in LB broth on the implant surface at the time of implantation (experimental limb), while the contralateral tibia received LB broth (no MRSA) (control limb). In a follow-on pilot study, a “therapeutic” cohort (TC) of rabbits underwent the same procedure, allowed infection to develop for 4 days, and then received vancomycin treatment (30 mg/kg; subcutaneous, twice per day) for 7 days. In vitro studies showed that when MRSA bacteria was directly seeded onto implant surfaces, there were lower MRSA counts on the TiNT groups at all timepoints and on the TiNT+Ag group at the 24 hr and 48 hr timepoints. TiNT surfaces with 110nm diameters showed the lowest bacteria counts compared to other nanotube diameters and were subsequently used for all in vivo work. In the in vivo experiment, sonication analysis showed that viable MRSA was greater on the TiNT and TiNT+Ag surfaces (104 CFU/mL, on average) vs. the Ti and TPS surfaces (103 CFU/mL, on average). In the TC, viable bacteria in the sonicant was approximately 102 to 103 CFU/mL for TiNT+Ag and TiNT implants, compared to 104 CFU/mL in the TPS group. μCT analysis of infected limbs showed greatest BIC on TPS implants, followed by TiNT, TiNT+Ag, and Ti. Bone-implant contact (BIC) was significantly greater in TiNT+Ag vs. Ti implants (p=0.023) and TPS vs. TiNT+Ag implants (p=0.031). In the TC, BIC% was greatest in the TPS group (0.277%) and approximately equivalent in the Ti, TiNT, and TiNT+Ag groups (0.15%, 0.1%, and 0.086%, respectively). Analysis of histologic sections demonstrated TiNT+Ag had the greatest BIC%, on average, (41%, range, 18-60), followed by TiNT (33%; range, 12-53), Ti (15%; range, 0-34), and TPS (12%, range, 3-28). In the TC, BIC% was greatest in TiNT+Ag implants (24%), followed by TPS (16%), Ti (15%), and TiNT (8%). On average, Ti had the lowest GP% (6%; range, 2-13), followed by TiNT+Ag (9%, range 3-14), TPS (10%, range 3-21), and TiNT (13%, range 1-26). In the TC, Ti had the lowest GP% (3%), followed by TiNT (5%), TPS (8%), and TiNT+Ag (15%). Sonication analysis indicated that TPS and Ti implants had less viable bacteria; however, overnight incubations showed that the implants continued to grow bacteria after sonication, perhaps indicating that differential adhesion of bacteria or decreased biofilm formation of the various surfaces may have interfered with assessment of in vivo antimicrobial efficacy. Specifically, the authors hypothesize that during sonication, bacteria detach more readily from nanotube surfaces, resulting in increased viable MRSA in the sonicant of nanotube implants compared with sonicant from TPS and Ti implants. With a reduction in viable bacteria from nanotube surfaces following antibiotic treatment, MRSA clearance rates may improve with the NT surface modification. Titiania nanotube surfaces may provide improvement over current implant technologies by simultaneously enhancing osseointegration, especially in non-tapered applications (e.g. tibial trays, fusion cages), as well as antibacterial properties. Work was funded through the University of Michigan MTRAC for Life Sciences Innovation Hub.