The rate of disuse osteopenia in admitted, non-weight-bearing patients.

Disuse osteopenia is a well-recognized consequence of prolonged physical inactivity, but its rate after orthopaedic injuries necessitating non-weight-bearing is not well studied. The purpose of this study was to estimate the rate of disuse osteopenia at the lumbar spine and proximal femur in patients with lower extremity trauma admitted to the hospital. We performed a retrospective chart review of patients with lower extremity trauma with a period of strict non-weight-bearing between completion of two computed tomography (CT) scans. The radiodensity of the proximal femur or lumbar vertebrae was measured from the earliest and latest available CT scans within the non-weight-bearing timeframe. The change in estimated bone mineral density (eBMD) was calculated as a proxy for disuse osteopenia. A total of 189,111 patients were screened, with 17 patients in the proximal femur group and 15 patients in the lumbar spine group meeting inclusion and exclusion criteria. The average rate of change in eBMD of the proximal femur was a decrease of 7.54 HU/day, 95% confidence interval (CI) [3.65, 11.43]. The average rate of change in eBMD of the lumbar spine was an increase of 1.45 HU/day, 95% CI [-3.15, 6.06]. In admitted, non-weight-bearing orthopaedic trauma patients, our novel study suggests that the proximal femur experiences disuse osteopenia during periods of non-weight-bearing, although this finding was not observed at the lumbar spine. The clinical significance of this data underscores the important consideration of disuse osteopenia by all physicians when caring for patients that may require non-weight-bearing restrictions.

Complete Killing of Agar Lawn Biofilms by Systematic Spacing of Antibiotic-Loaded Calcium Sulfate Beads.

Background: Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA) are the major causative agents of acute and chronic infections. Antibiotic-loaded calcium sulfate beads (ALCSB) are used in the management of musculoskeletal infections such as periprosthetic joint infections (PJI). Methods: To determine whether the number and spatial distribution of ALCSB are important factors to totally eradicate biofilms, ALCSBs containing vancomycin and tobramycin were placed on 24 h agar lawn biofilms as a single bead in the center, or as 16 beads placed as four clusters of four, a ring around the edge and as a group in the center or 19 beads evenly across the plate. Bioluminescence was used to assess spatial metabolic activity in real time. Replica plating was used to assess viability. Results: For both strains antibiotics released from the beads completely killed biofilm bacteria in a zone immediately adjacent to each bead. However, for PA extended incubation revealed the emergence of resistant colony phenotypes between the zone of eradication and the background lawn. The rate of biofilm clearing was greater when the beads were distributed evenly over the plate. Conclusions: Both number and distribution pattern of ALCSB are important to ensure adequate coverage of antibiotics required to eradicate biofilms.

Effects of loading concentration, blood and synovial fluid on antibiotic release and anti-biofilm activity of bone cement beads.

Antibiotic loaded cement beads are commonly used for the treatment of biofilm related orthopaedic periprosthetic infections; however the effects of antibiotic loading and exposure of beads to body fluids on release kinetics are unclear. The purpose of this study was to determine the effects of (i) antibiotic loading density (ii) loading amount (iii) material type and (iv) exposure to body fluids (blood or synovial fluid) on release kinetics and efficacy of antibiotics against planktonic and lawn biofilm bacteria. Short-term release into an agar gel was evaluated using a fluorescent tracer (fluorescein) incorporated in the carrier materials calcium sulfate (CaSO4) and poly methyl methacrylate (PMMA). Different fluorescein concentrations in CaSO4 beads were evaluated. Mechanical properties of fluorescein-incorporated beads were analyzed. Efficacy of the antibiotics vancomycin (VAN) or tobramycin (TOB) alone and in combination was evaluated against lawn biofilms of bioluminescent strains of Staphylococcus aureus and Pseudomonas aeruginosa. Zones of inhibition of cultures (ZOI) were measured visually and using an in-vivo imaging system (IVIS). The influence of body fluids on release was assessed using CaSO4 beads that contained fluorescein or antibiotics and were pre-coated with human blood or synovial fluid. The spread from the beads followed a square root of time relationship in all cases. The loading concentration had no influence on short-term fluorescein release and pre-coating of beads with body fluids did not affect short-term release or antibacterial activity. Compared to PMMA, CaSO4 had a more rapid short term rate of elution and activity against planktonic and lawn biofilms. This study highlights the importance of considering antibiotic loading and packing density when investigating the clinical application of bone cements for infection management.