Functional studies on isolated mitochondria critically rely on the right choice of respiration buffer. Differences in buffer composition can lead to dramatically different respiration rates leading to difficulties in comparing prior studies. The ideal buffer facilities high ADP-stimulated respiratory rates and minimizes substrate transport effects so that the ability to distinguish between various treatments and conditions is maximal. In this study, we analyzed a variety of respiration buffers and substrate combinations to determine the optimal conditions to support mitochondrial function through ADP-stimulated respiration and uncoupled respiration using FCCP. The buffers consisted of a standard KCl based buffer (B1) and three modified buffers with chloride replaced by the K-lactobionate, sucrose, and the antioxidant taurine (B2) or K-gluconate (B3). The fourth buffer (B4) was identical to B2 except that K-lactobionate was replaced with K-gluconate. The substrate combinations consisted of metabolites that utilize different pathways of mitochondrial metabolism. To test mitochondrial function, we used isolated cardiac guinea pig mitochondria and measured oxygen consumption for three respiratory states using an Oroboros Oxygraph-2k. These states were the leak state (energized mitochondria in the absence of adenylates), ADP-stimulated state (energized mitochondria in the presence of saturating ADP concentrations), and uncoupled state (energized mitochondria in the presence of FCCP). On average across all substrate combinations, buffers B2, B3, and B4 had an increase of 16%, 26%, and 35% for the leak state, ADP-simulated state, and uncoupled state, respectively, relative to rates using B1. The common feature distinguishing these buffers from B1 is the notable lack of high chloride concentrations. Based on the respiratory rate metrics obtained with the substrate combinations, we conclude that the adenine nucleotide translocase, the dicarboxylate carrier, and the alpha-ketoglutarate exchanger are partially inhibited by chloride. Therefore, when the goal is to maximize ADP-stimulated respiration, buffers containing K-lactobionate or K-gluconate are superior choices compared to the standard KCl-based buffers.

Background: Displaced pediatric supracondylar humeral fractures (SCHFs) are stabilized after reduction by smooth pins. Although some SCHFs are biomechanically stable after lateral-only entry pinning (lateral pinning), an additional medial entry pin (cross-pinning) confers superior stabilization in some SCHFs. There is a recognized risk of iatrogenic ulnar nerve injury with medial entry pinning. The best existing evidence has estimated an iatrogenic ulnar nerve injury rate of approximately 3.4% in cross-pinning. In similar studies, the rate of iatrogenic nerve injury (all nerves) in lateral pinning is estimated at 1.9%. This study aimed to use a large, single-center, single-technique (mini-open) retrospective case series to determine the rate of iatrogenic ulnar nerve injury in cross-pinning.Methods: Patients undergoing percutaneous cross-pinning via the mini-open technique for SCHFs from 2007 to 2017 were retrospectively reviewed. Injury characteristics, operative variables, fixation technique, and complications, such as iatrogenic nerve injury, were recorded. Patients who underwent operative treatment at another hospital, had no postoperative follow-up, or died due to polytrauma were excluded.Results: In this study, 698 patients undergoing cross-pinning during the study period were identified. Patients treated with cross-pinning had severe fractures, including a total of 198 preoperative neurovascular injuries (28.4%), 32 patients (4.6%) with skin tenting, and 19 patients (2.7%) with open fractures. Iatrogenic nerve injury was reported in 3 cases (0.43%), all of which affected the ulnar nerve. In 2 of 3 cases of iatrogenic nerve injury, the ulnar nerve symptoms resolved at a mean follow-up of 15 weeks. Conclusions:The mini-open approach for medial pin insertion is safer than previous estimates. Here, in the largest single-center study of cross-pinning for SCHFs, the iatrogenic ulnar nerve injury rate of 0.43% was nearly 10 times lower than estimated rates from recent meta-analyses. Considering all nerves, the iatrogenic injury rate for this cross-pinning cohort was also lower than the estimated iatrogenic nerve injury rate for lateral pinning.

Background: Stabilization of the medial column is vital in preventing the loss of fixation and malunion in displaced pediatric supracondylar humeral fractures (SCHFs). The preferred percutaneous pin configuration for medial column fixation remains controversial between medial pinning (cross-pinning) and additional lateral-based pinning. The intraoperative internal rotation stress test (IRST) has been proposed to reliably determine the optimal fixation strategy for each unique fracture. This study evaluated the impact of implementing the IRST on both the choice of pin configuration and institution-wide complications in pediatric patients treated operatively for SCHFs.Methods: Pediatric patients undergoing percutaneous pinning for SCHFs between 2007 and 2017 at a single center were retrospectively reviewed. The IRST was made a universal institutional practice in 2013. Patients were divided into 2 groups for analysis: (1) patients who underwent treatment before the IRST was implemented in 2013 (the pre-IRST group), and (2) patients who were treated after the IRST was implemented in 2013 (the IRST group). Subgroup analysis was completed for patients in the IRST group who were treated with cross-pinning or 3 lateral-based pins.Results: In this study, 820 patients in the pre-IRST group and 636 patients in the IRST group were included. After the IRST implementation, the rate of loss of fixation fell from 1.2% to 0% (p = 0.003), and the reoperation rate fell from 3.3% to 0.2% (p < 0.001). No cases resulted in a loss of fixation after the adoption of the IRST. The number of patients treated with cross-pinning decreased significantly from 53.2% to 31.6% (p < 0.001) after the IRST implementation, yet cross-pinning continued to be used for more severe fractures. Complication rates within the IRST group were not significantly different (p > 0.05) between cross-pinning and 3 lateral-based pins.Conclusions: In the largest cohort reported on to date, to our knowledge, institutional implementation of the IRST resulted in a significant reduction in the use of cross-pinning. Although the usage of cross-pinning decreased, crosspinning was still used frequently in the most severe fractures. The IRST use also resulted in significantly fewer complications such as loss of fixation after institution-wide implementation of the IRST for treating pediatric SCHFs.

Background: Elbow fractures are the most common pediatric fractures requiring operative treatment. To date, few studies have examined what annual factors drive pediatric elbow fracture incidence and no studies have examined which annual factors drive elbow fracture severity or resource utilization. The goal of this study was to not only document the annual patterns of pediatric elbow fracture incidence and severity but also the impact of these patterns on resource utilization in the emergency department, emergency medical service transportation, and the operating room (OR). Methods: Retrospective cohort study of 4414 pediatric elbow fractures from a single tertiary hospital (2007 to 2017). Exclusion criteria included outside treatment or lack of diagnosis by an orthopaedist. Presentation information, injury patterns, transport, and treatment requirements were collected. Pearson correlations were used to analyze factors influencing fracture incidence, severity, and resource utilization.Results: Pediatric elbow fracture incidence positively correlated with monthly daylight hours, but significantly fewer elbow fractures occurred during summer vacation from school compared with surrounding in school months. While fewer overall fractures occurred during summer break, the fractures sustained were greater in severity, conferring higher rates of displacement, higher risk of neurovascular injury, and greater needs for emergency transportation and operative treatment. Yearly, elbow fractures required 320.6 OR hours (7.7% of all pediatric orthopaedic OR time and 12.3% of all pediatric orthopaedic operative procedures), 203.4 hospital admissions, and a total of 4753.7 miles traveled by emergency medical service transportation to manage. All-cause emergency department visits were negatively correlated with daylight hours, inversing the pattern seen in elbow fractures. Conclusion: Increased daylight, while school was in session, was a major driver of the incidence of pediatric elbow fractures. While summer vacation conferred fewer fractures, these were of higher severity. As such, increased daylight correlated strongly with monthly resource utilization, including the need for emergency transportation and operative treatment. This study provides objective data by which providers and administrators can more accurately allocate resources.