BackgroundFemoral nerve (FNB) and adductor canal blocks (ACB) are used in the setting of total knee arthroplasty (TKA), but neither has been demonstrated to be clearly superior. Although dynamometer studies have shown ACBs spare perioperative quadriceps function when compared to FNBs, ACBs have been widely adopted in orthopaedic surgery without significant evidence that they decrease the risk of perioperative falls.MethodsAll patients who received single-shot FNB (129 patients) or ACB (150 patients) at our institution for unilateral primary TKA from April 2014 to September 2015 were retrospectively reviewed for perioperative falls or near-falls during physical therapy and inpatient care.ResultsThere were significantly more “near-falls” with documented episodes of knee buckling in the FNB group (17 vs 3, P = .0004). These patients’ first buckling episode occurred at an average of 21.1 hours postoperatively (standard deviation 5.83, range 13.83-41.15). There were no significant differences in pain scores between the 2 groups at any of the time periods measured; however, patients in the FNB group consumed significantly fewer opioids on postoperative day 1 than the ACB group (59 morphine equivalents vs 73, P = .004).ConclusionsA significantly higher rate of near-falls with knee buckling during in-hospital physical therapy was discovered in the FNB group. With increasing numbers of TKAs being performed on a “fast-track” discharge model, these results must be seriously considered, particularly in patients planning to go home the same day, to reduce the risk of postoperative falls. These data support the recent clinical data trend favoring ACB over FNB in orthopaedic surgery.

Scale-up of sediment microbial fuel cells (SMFCs) is important to generating practical levels of power for undersea devices. Sustained operation of many sensors and communications systems require power in the range of 0.6 mW to 20 W. Small scale SMFC systems evaluated primarily in the laboratory indicate power densities for typical graphite plate anodes on the order of 10-50 mW m 22 . However, previous work also suggests that SMFC power production may not scale directly with size. Here, we describe a combination of lab and field studies to evaluate scale up for carbon fabric anodes with a projected surface area ranging from 25 cm 2 to 12 m 2 . The results indicate that power generation scales almost linearly with anode size up to about 1-2 m 2 of projected surface area. Our model suggests that anodes larger than this can experience significant reduction in power density, confirming laboratory observations. These results suggest that the majority of losses along the anode surface occur closest to the electronics, where the amount of current passing along an anode is the greatest. A multi-anode approach is discussed for SMFCs, suggesting that scale-up can be achieved using segmented anode arrays.

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.