Time-series observations and a phytoplankton manipulation experiment were combined to test the hypothesis that phytoplankton succession effects changes in bacterial community composition. Three humic lakes were sampled weekly May-August and correlations between relative abundances of specific phytoplankton and bacterial operational taxonomic units (OTUs) in each time series were determined. To experimentally characterize the influence of phytoplankton, bacteria from each lake were incubated with phytoplankton from one of the three lakes or no phytoplankton. Following incubation, variation in bacterial community composition explained by phytoplankton treatment increased 65%, while the variation explained by bacterial source decreased 64%. Free-living bacteria explained, on average, over 60% of the difference between phytoplankton and corresponding no-phytoplankton control treatments. Fourteen out of the 101 bacterial OTUs that exhibited positively correlated patterns of abundance with specific algal populations in time-series observations were enriched in mesocosms following incubation with phytoplankton, and one out of 59 negatively correlated bacterial OTUs was depleted in phytoplankton treatments. Bacterial genera enriched in mesocosms containing specific phytoplankton assemblages included Limnohabitans (clade betI-A), Bdellovibrio and Mitsuaria. These results suggest that effects of phytoplankton on certain bacterial populations, including bacteria tracking seasonal changes in algal-derived organic matter, result in correlations between algal and bacterial community dynamics.

BACKGROUND: Rising health care expenditures and declining reimbursements have generated interest in providing interventions of value. The use of external fixation is a commonly used intermediate procedure for the staged treatment of unstable fractures. External fixator constructs can vary in design and costs based on selected component configuration. The objective of this study was to evaluate cost variation and relationships to injury and noninjury characteristics in temporizing external fixation of tibial plateau fractures. We hypothesize that construct costs are highly variable and present no noticeable patterns with both injury and noninjury characteristics. METHODS: A retrospective review of tibial plateau fractures treated with initial temporizing external fixation between 2010 and 2016 at 2 Level I trauma centers was conducted. Fracture and patient characteristics including age, body mass index, AO/OTA classification, and Schatzker fracture classification were observed with construct cost. In addition, injury-independent characteristics of surgeon education, site of procedure, and date of procedure were evaluated with construct cost. Factors associated with cost variation were assessed using nonparametric comparative and goodness-of-fit regression tests. RESULTS: Two hundred twenty-one patient cases were reviewed. The mean knee spanning fixator construct cost was $4947 (95% confidence interval = $4742–$5152). The overall range in construct costs was from $1848 to $11,568. The mean duration of use was 16.4 days. No strong correlations were noted between construct cost and patient demographics (r2 = 0.02), fracture characteristics (r2 = 0.02), or injury-independent characteristics (r2 = 0.10). Finally, there was no significant difference between constructs of traumatologists and other orthopaedic surgeon subspecialists (P = 0.12). CONCLUSIONS: Temporizing external fixation of tibial plateau is a high-cost intervention per unit of time and exhibits massive variation in the mean cost. This presents an ideal opportunity for cost savings by reducing excessive variation in implant component selection. LEVEL OF EVIDENCE: Level III. Retrospective Cohort.

Objective: To determine the total cost for a 30-day episode of care for high-energy tibial plateau fractures and the aspects of care associated with total cost.Design: Time-driven activity-based costing analysis.Setting: One Level 1 adult trauma center. Patients:One hundred twenty-one patients with isolated, bicondylar tibial plateau fractures undergoing staged treatment were reviewed.Primary Outcome: Total cost.Results: A total of 85 patients were included and most sustained Schatzker VI fractures (n = 66, 77%). All patients were treated with biplanar external fixation before definitive fixation. A total of 26 patients (31%) were discharged to skilled nursing facilities, and 37 patients (43%) were not discharged between procedures. Total cost for a 30day episode of care was $22,113 6 4056. External fixation components ($5952, 26.9%), length of hospital stay ($5606, 25.4%), discharge to skilled nursing facility (SNF) ($3061, 13.8%), and definitive fixation implants ($2968, 13.4%) contributed to the total cost. The following were associated with total cost: patient discharged to SNFs (P , 0.001), patient remaining inpatient after external fixation (P , 0.001), days of admission for open reduction internal fixation (ORIF) (P = 0.005), days spent with external fixation (P , 0.001), days in a SNF after ORIF (P , 0.001), and external fixation component cost (P , 0.001). Conclusions:External fixation component selection is the largest contributor to cost of a 30-day episode of care for high-energy bicondylar tibial plateau fractures. Reduction in cost variability may be possible through thoughtful use of external fixation components and care pathways.

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