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Arc-flash is one of two hazards primarily associated with electrical systems. Due to its prevalence, the majority of arc-flash research has been dedicated to alternating-current (ac) electrical systems. However, direct-current (dc) electrical systems are becoming increasingly common, such as energy storage systems, solar photovoltaic panels, and dc microgrids. Thus, more research is needed to address the arc-flash hazards posed by dc electrical systems. Current dc arc-flash models are theoretical and lack empirical data compared with ac arc-flash models. This article presents models developed through empirical testing utilizing low-voltage (LV) station batteries. Furthermore, this article investigates possible interactions between dc arc-flash within LV battery systems and atmospheric conditions, such as temperature and relative humidity. In the end, this article provides information regarding the implementation of these models within American Electric Power's (AEP's) safety practices regarding batteries and dc panelboards.

Station batteries used as a backup source to supply station direct-current (dc) power to relays, etc., present a source of personnel exposure to dc arc flash. However, dc arc flash is less understood compared with the arc-flash phenomena that occur in alternating-current (ac) systems. Some models exist to quantify the potential hazards posed by dc electrical systems; however, there is little empirical data available. Additionally, the lower voltage and/or lower capacity station batteries are even less researched. As a result, a series of arc-flash tests were performed at the Dolan Technology Center of American Electric Power (AEP) utilizing two 125 Vdc batteries with rated capacities of 100 and 150 Ah. For these tests, working distance and gap width were used as independent variables. Upon the conclusion of testing, various relationships were analyzed to generate a predictive model for incident energy. This model serves as a compilation of the empirical data collected during testing and will contribute to future research efforts to better understand dc arc-flash incidents from station batteries.

MINI: This study compared clinical and patient-reported outcomes following transforaminal lumbar interbody fusion between patients who use or do not use marijuana. We found that patients who use marijuana are younger, but do not demonstrate any differences in preoperative or postoperative Oswestry disability index scores or rates of fusion.A retrospective cohort study.The purpose of this study was to evaluate marijuana usage and its effect on outcomes following transforaminal lumbar interbody fusion (TLIF).As marijuana becomes legalized throughout the United States, its medicinal and recreational usage is becoming more mainstream. Clinicians currently have little guidance regarding both short-term and long-term effects of marijuana usage on surgical interventions. While the rate of lumbar spinal fusion in the United States continues to grow, the effect of marijuana usage on fusion remains uncertain.One hundred two patients who underwent TLIF performed by the same surgeon were followed for 12 months. Patients were self-reported for marijuana usage (n = 36). Patient reported outcome measures included preoperative Oswestry disability index (ODI), 6-month ODI, and 12-month ODI, as well as length of stay (LOS), complications, return to operating room (OR), revision surgery, and confirmed fusion. Continuous variables were compared using the independent two-sample t test or analysis of variance (ANOVA), whereas categorical variables were analyzed using the chi-square or Fischer exact tests. Adjusted analysis was performed using a multivariate logistic regression model.Marijuana usage was associated with a younger population (P 0.001), but showed no difference regarding sex or body mass index compared with the non-usage group. There was no statistically significant difference in complications, return to OR, or revision surgery between groups. When controlling for factors such as age and preoperative ODI, multivariate analysis demonstrated that marijuana usage did not limit postoperative ODI reduction. The marijuana usage group demonstrated shorter LOS (2.42 vs. 3.00 d, P = 0.020). Fusion rates at 12 months were similar between groups (96% vs. 92.3%, P = 0.678). ODI was similar between groups at all time points.Perioperative outcomes were similar in patients who underwent TLIF regardless of marijuana usage.3.A retrospective cohort study. The purpose of this study was to evaluate marijuana usage and its effect on outcomes following transforaminal lumbar interbody fusion (TLIF). As marijuana becomes legalized throughout the United States, its medicinal and recreational usage is becoming more mainstream. Clinicians currently have little guidance regarding both short-term and long-term effects of marijuana usage on surgical interventions. While the rate of lumbar spinal fusion in the United States continues to grow, the effect of marijuana usage on fusion remains uncertain. One hundred two patients who underwent TLIF performed by the same surgeon were followed for 12 months. Patients were self-reported for marijuana usage (n = 36). Patient reported outcome measures included preoperative Oswestry disability index (ODI), 6-month ODI, and 12-month ODI, as well as length of stay (LOS), complications, return to operating room (OR), revision surgery, and confirmed fusion. Continuous variables were compared using the independent two-sample t test or analysis of variance (ANOVA), whereas categorical variables were analyzed using the chi-square or Fischer exact tests. Adjusted analysis was performed using a multivariate logistic regression model. Marijuana usage was associated with a younger population (P 0.001), but showed no difference regarding sex or body mass index compared with the non-usage group. There was no statistically significant difference in complications, return to OR, or revision surgery between groups. When controlling for factors such as age and preoperative ODI, multivariate analysis demonstrated that marijuana usage did not limit postoperative ODI reduction. The marijuana usage group demonstrated shorter LOS (2.42 vs. 3.00 d, P = 0.020). Fusion rates at 12 months were similar between groups (96% vs. 92.3%, P = 0.678). ODI was similar between groups at all time points. Perioperative outcomes were similar in patients who underwent TLIF regardless of marijuana usage. Level of Evidence: 3.

Study Design Retrospective cohort study Objective The purpose of this study was to evaluate safety in lumbar spinal fusion with tranexamic acid (TXA) utilization in patients using marijuana. Methods This was a retrospective cohort study involving a single surgeon’s cases of 1 to 4 level lumbar fusion procedures. Two hundred and ninety-four patients were followed for ninety days post-operatively. Consecutive patients were self-reported for daily marijuana use (n = 146) and compared to a similar cohort of patients who denied usage of marijuana (n = 146). Outcomes were collected, which included length of stay (LOS), estimated blood loss (EBL), post-operative myocardial infarction, seizures, deep venous thrombosis, pulmonary embolus, death, readmission, need for further surgery, infection, anaphylaxis, acute renal injury, and need for blood product transfusion. Results Patients in the marijuana usage cohort had similar age (58.9 years ±12.9 vs 58.7 years ±14.8, P = .903) and distribution of levels fused ( P = .431) compared to the non-usage cohort. Thromboembolic events were rare in both groups (marijuana usage: 1 vs non-usage: 2). Compared to the non-usage cohort, the marijuana usage cohort had a similar average EBL (329.9 ± 298.5 mL vs 374.5 ± 363.8 mL; P = .254). Multivariate regression modeling demonstrated that neither EBL (OR 1.27, 95% CI 0.64-2.49) nor need for transfusion (OR 1.56, 95% CI 0.43-5.72) varied between cohorts. The non-usage cohort had twice the risk of prolonged LOS compared to the marijuana usage cohort (OR 2.05, 95% CI 1.15-3.63). Conclusion Marijuana use should not be considered a contraindication for TXA utilization in lumbar spine surgery.

Study Design:Break-even cost analysis.Objective:The goal of this study is to examine the cost-effectiveness of vancomycin powder for preventing infection following lumbar laminectomy.Methods:The product cost of vancomycin powder was obtained from our institution’s purchasing records. Infection rates and revision costs for lumbar laminectomy and lumbar laminectomy with fusion were obtained from the literature. A break-even analysis was then performed to determine the absolute risk reduction (ARR) in infection rate to make prophylactic application of vancomycin powder cost-effective. Analysis of lumbar laminectomy with fusion was performed for comparison.Results:Costing $3.06 per gram at our institution, vancomycin powder was determined to be cost-effective in lumbar laminectomy if the infection rate of 4.2% decreased by an ARR of 0.015%. Laminectomy with fusion was also determined to be cost-effective at the same cost of vancomycin powder if the infection rate of 8.5% decreased by an ARR of 0.0034%. The current highest cost reported in the literature, $44.00 per gram of vancomycin powder, remained cost-effective with ARRs of 0.21% and 0.048% for laminectomy and laminectomy with fusion, respectively. Varying the baseline infection rate did not influence the ARR for either procedure when the analysis was performed using the product cost of vancomycin at our institution.Conclusions:This break-even analysis demonstrates that prophylactic vancomycin powder can be highly cost-effective for lumbar laminectomy. At our institution, vancomycin powder is economically justified if it prevents at least one infection out of 6700 lumbar laminectomy surgeries.

Study Design Retrospective Objective To compare the rate of positive pathology on thoracic MRI ordered by surgical spine specialists to those ordered by nonsurgical spine specialists. Methods Outpatient thoracic MRIs from January–March 2019 were evaluated from a single academic health care system. Studies without a known ordering provider, imaging report, or patients with known presence of malignancy, multiple sclerosis, recent trauma, or surgery were excluded (n = 320). Imaging studies were categorized by type of provider placing the order (resident, attending, or advanced practice practitioner) and department. MRIs were deemed positive if they showed relevant pathology that correlated with indication for exam as determined by a radiologist. One-sided chi-squared analysis was performed to determine statistical significance. Results Overall, our data demonstrated 17.2% of studies with positive pathology. Compared to nonspecialty clinicians, subspecialists showed 35/184 (19.0%) positivity rate versus the non-specialist with 20/136 (14.7%) positivity rate (P = .156). Posthoc analysis demonstrated that surgical specialists who order thoracic MRIs yield significantly higher positivity rates at 19/79 (24.0%) compared to nonsurgical specialists at 36/241 (14.9%) (P < .05). Overall, neurosurgery demonstrated the highest rate of positive thoracic MRIs at 14/40 (35.0%). Comparison between the rate of positivity between physicians and advanced practitioners was insignificant (P > .05). Conclusions Clinical diagnosis of symptomatic thoracic spine degenerative disease requires an expert physical exam combined with careful attention to radiology findings. Although the percent of relevant pathology on thoracic MRI is low, our data suggests evaluation by a surgical specialist should precede ordering a thoracic spine MRI.

Study Design:Retrospective cohort study.Objectives:The objective of this study was to determine whether lower socioeconomic status was associated with increased resource utilization following anterior discectomy and fusion (ACDF).Methods:The National Inpatient Sample database was queried for patients who underwent a primary, 1- to 2-level ACDF between 2005 and 2014. Trauma, malignancy, infection, and revision surgery were excluded. The top and bottom income quartiles were compared. Demographics, medical comorbidities, length of stay, complications, and hospital cost were compared between patients of top and bottom income quartiles.Results:A total of 69 844 cases were included. The bottom income quartile had a similar mean hospital stay (2.04 vs 1.77 days, P = .412), more complications (2.45% vs 1.77%, P < .001), and a higher mortality rate (0.18% vs 0.11%, P = .016). Multivariate analysis revealed bottom income quartile was an independent risk factor for complications (odds ratio = 1.135, confidence interval = 1.02-1.26). Interestingly, the bottom income quartile experienced lower mean hospital costs ($17 041 vs $17 958, P < .001).Conclusion:Patients in the lowest income group experienced more complications even after adjusting for comorbidities. Therefore, risk adjustment models, including socioeconomic status, may be necessary to avoid potential problems with access to orthopedic spine care for this patient population.

Retrospective review of the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database years 2010 to 2015.Investigate which short-term outcomes differ for cervical laminoplasty and laminectomy and fusion surgeries.Conflicting reports exist in spine literature regarding short-term outcomes following cervical laminoplasty and posterior laminectomy and fusion. The objective of this study was to compare the 30-day outcomes for these two treatment groups for multilevel cervical pathology.Patients who underwent cervical laminoplasty or posterior laminectomy and fusion were identified in National Surgical Quality Improvement Program (NSQIP) based on Current Procedural Terminology (CPT) code: laminoplasty 63,050 and 63,051, posterior cervical laminectomy 63,015 and 63,045, and instrumentation 22,842. Propensity-adjusted multivariate regressions assessed differences in postoperative length of stay, adverse events, discharge disposition, and readmission.Three thousand seven hundred ninety-six patients were included: 2397 (63%) underwent cervical laminectomy and fusion and 1399 (37%) underwent cervical laminoplasty. Both groups were similar in age, sex, body mass index (BMI), American Society of Anesthesiologist Classification (ASA), Charleston Comorbidity Index (CCI), and had similar rates of malnutrition, chronic kidney disease, diabetes, chronic obstructive pulmonary disease, and history for steroid use. Age more than 70 and age less than 50 were not associated with one treatment group over the other (P 0.05). Compared with laminoplasty patients, laminectomy and fusion patients had increased lengths of stay (LOS) (4.5 vs. 3.7 d, P 0.01) and increased rates of adverse events (41.7% vs. 35.9%, P 0.01), discharge to rehab (16.4% vs. 8.6%, P 0.01), and skilled nursing facilities (12.2% vs. 9.7%, P = 0.02), and readmission (6.2% vs. 4.5%, P = 0.05). Both groups experienced similar rates of death, pulmonary embolus, deep vein thrombosis, deep and superficial surgical site infection, and reoperation (P 0.05 for all).Posterior cervical laminectomy and fusion patients were found to have increased LOS, readmissions, and complications despite having similar pre-op demographics and comorbidities. Patients and surgeons should consider these risks when considering surgical treatment for cervical pathology.3.

In accordance with the Physician Payment Sunshine Act, all industry payments to physicians in the United States have become publicly available. Previous research has indicated that orthopedic surgeons receive the greatest amount of industry compensation compared with other surgical subspecialists. However, the relationship between this compensation and research productivity is less clear. This study sought to investigate the relationship between consulting fees paid to orthopedic surgeons and academic productivity. Using the Centers for Medicare & Medicaid Services Open Payments Database, this study identified 2555 orthopedic surgeons who received at least one industry consulting fee in 2015. Physicians who received total consulting fees of at least $20,000 (US) were stratified into the high payment group. The number of publications and the h-index for each physician were used as metrics of scholarly impact. Mean publication number and h-index for the high payment group were compared with all other physicians in the sample using an independent-samples t test. A total of 2555 orthopedic surgeons received consulting payments totaling $62,323,143 in 2015. The mean consulting payment was $24,393 (SD, $45,465). The publication number was greater for the high payment group (mean, 61.6; SD, 135.6) compared with all other physicians in the sample (mean, 36.1; SD, 95.6). Additionally, the mean h-index for the high payment group was 13.7 (SD, 14.3) compared with 10.0 (SD, 11.6) for all other orthopedic surgeons. These findings indicate that the orthopedic surgeons who receive more in industry consulting fees are also those who contribute most substantially to the body of orthopedic literature. [ Orthopedics . 2019; 42(3):137–142.]

Inverter-based distributed energy resources (DERs) can supply high-quality ac power in a microgrid due to their fast dynamic response. To achieve high reliability in an islanded microgrid, they are normally operated as voltage-controlled sources. However, the net load supplied by voltage-controlled inverter-based DERs can exceed their rated capacity, particularly during their transition from the grid-connected operation mode. Therefore, a comprehensive analysis of the DER survivability for overload conditions is crucial. Several experimental tests were conducted at the Consortium for Electric Reliability Technology Solutions Microgrid Testbed on the prime-mover powered inverter-based DER for learning about its survivability during overload conditions. In this paper, a thorough investigation of the inverter-based DER's survivability is carried out based on the prime-mover stalling phenomenon. Analytical expressions are derived for key design parameters of load-shedding algorithms, such as time-to-threshold frequency, maximum time delay , and maximum survivability time . The theoretical estimates are validated with the results obtained from the experimental testing. Furthermore, the minimum load-shedding estimate is determined for any prime-mover powered inverter-based DER to survive a transient overload condition.

Surgeons have increasingly adopted robotic-assisted lumbar spinal fusion due to indications that robotic-assisted surgery can reduce pedicle screw misplacement. However, the impact of robotic-assisted spinal fusion on patient outcomes is less clear.This study aimed to compare rates of perioperative complications between robotic-assisted and conventional lumbar spinal fusion.Retrospective cohort study.A total of 520 patients undergoing lumbar fusion were analyzed. The average ages of patients in the robotic-assisted versus conventional groups were 60.33 and 60.31, respectively (p=.987). Patients with a diagnosis of fracture, traumatic spinal cord injury, spina bifida, neoplasia, or infection were excluded.This study compared the rates perioperative major and minor complications for elective lumbar fusion between each cohort.This study screened hospital discharges in the United States from 2010 to 2014 using the National Inpatient Sample and the Nationwide Inpatient Sample (NIS). The International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedure codes were used to identify 209,073 patients who underwent conventional lumbar fusion (ICD 81.04-8) and 279 patients who underwent robotic-assisted lumbar fusion (ICD 81.04-8 and ICD 17.41, 17.49). Major and minor complications were identified using ICD-9-CM diagnosis codes. The robotic-assisted and conventional fusion groups were statistically matched on age, year, sex, indication, race, hospital type, and comorbidities. Univariate and multivariate logistic regression were used to compare risks of major and minor complications.We matched 257 (92.11%) robotic-assisted patients with an equal number of patients undergoing conventional lumbar fusion. Minor complications occurred in 16.73% of cases in the conventional group and 31.91% of cases in the robotic-assisted group (p.001). Major complications occurred in 6.61% of the conventional cases compared to 8.17% of robotic-assisted cases (p=.533). For robotic-assisted fusion, multivariate analysis revealed that there was no difference in the likelihood of major complications (OR=0.834, 95% CI=0.214-3.251) or minor complications (OR = 1.450, 95% CI=0.653-3.220).In a statistically matched cohort, patients who underwent robotic-assisted lumbar fusion had similar rates of major and minor complications compared to patients who underwent conventional lumbar fusion.

A synchronous generator-based distributed energy resource (DER) is commonly employed in microgrids due to its low cost and simple controls. However, there are many challenges to the DER operation when it is sized for supplying the critical loads alone in a microgrid. In particular, the DER would experience an overload condition during the microgrid transition from grid-connection to islanded operation, when the noncritical loads are also supplied momentarily. Therefore, it is very important to have a clear understanding on the survivability of a synchronous generator-based DER for transient overload conditions. Recently, experimental tests on survivability of the DER were carried out in the Consortium for Electric Reliability Technology Solutions Microgrid Testbed at American Electric Power. In this paper, an in-depth analysis of the synchronous generator-based DER operation during transient overload conditions is presented. The key relationships governing the system dynamic behavior of synchronous generator-based DER are analyzed to design the load shedding scheme for its survivability. Several case studies are illustrated to demonstrate the validity of the proposed load shedding method.

Retrospective Database Study.Investigate utilization of bone morphogenetic protein (BMP-2) between 2004 and 2014.The utilization, particularly off-label utilization, of BMP-2 has been controversial and debated in the literature. Given the concerns regarding cancer and potential complications, the risk benefit profile of BMP must be weighed with each surgical case. The debate regarding the costs and potential side effects of BMP-2 compared with autologous iliac crest bone harvest has continued.The National Inpatient Sample (NIS) database was queried for the use of BMP-2 (ICD-9-CM 84.52) between 2004 and 2014 across 44 states. The NIS database represents a 20% sample of discharges, weighted to provide national estimates. BMP-2 utilization rates in spine surgery fusion procedures were calculated as a fraction of the total number of thoracic, lumbar, and sacral spinal fusion surgeries performed each year.Between 2004 and 2014, BMP-2 was utilized in 927,275 spinal fusion surgeries. In 2004, BMP-2 was utilized in 28.3% of all cases (N=48,613). The relative use of BMP-2 in spine fusion surgeries peaked in 2008 at 47.0% (N=112,180). Since then, it has continued to steadily decline with an endpoint of 23.6% of cases in 2014 (N=60,863).Throughout the United States, the utilization of BMP-2 in thoracolumbar fusion surgeries increased from 28.3% to 47.0% between 2004 and 2008. However, from 2008 to 2014, the utilization of BMP-2 in thoracolumbar spine fusion surgeries decreased significantly from 47.0% to 23.4%. While this study provides information on the utilization of BMP-2 for the entire United States over an 11-year period, further research is needed to the determine the factors affecting these trends.

Patient: Male, 19-year-old Final Diagnosis: Opioid withdrawal syndrome Symptoms: Fever • knee effusion • knee joint pain Medication: — Clinical Procedure: ACL reconstruction • knee aspiration Specialty: Anesthesiology • Orthopedics and Traumatology • Pharmacology and Pharmacy • Sports Medicine • Surgery Objective: Unusual clinical course Background: A short course of opioid narcotics is often prescribed for postoperative anterior cruciate ligament (ACL) reconstruction pain management. Unfortunately, there is a well-documented incidence of opioid withdrawal syndrome (OWS) following short-term use of these medications. OWS can present with symptoms such as influenza-like illness. It is important to differentiate OWS from infectious illnesses, especially after surgery. Case Report: We present a case of OWS in a patient who underwent ACL reconstruction 7 days prior. The patient’s OWS symptoms were similar to symptoms of a postoperative infection. The knee was aspirated, and the analysis of the aspirate was not concerning for an infection. The patient’s symptoms spontaneously resolved on postoperative day 10. This is the first documented case of OWS mimicking ACL reconstruction joint infection. Conclusions: OWS after surgery may present with symptoms similar to joint infection. It is important to consider OWS as a potential complication after surgery and differentiate it from infection to avoid any further unnecessary invasive treatments for the patient.

Arc flash is one of two hazards primarily associated with electrical systems. Due to its prevalence, the majority of arc flash research has been dedicated to alternating current (AC) electrical systems. However, direct current (DC) electrical systems are becoming increasingly common, such as electrical storage systems (ESSs), solar photovoltaic (PV) panels, and high-voltage (HV) DC transmission lines. Thus, more research is needed to address the arc flash hazards posed by DC electrical systems. Current DC arc flash models are theoretical and lack empirical data compared with AC arc flash models. This paper presents models developed through empirical testing utilizing low-voltage (LV) station batteries. Furthermore, this paper investigates possible interactions between DC arc flash within LV battery systems and atmospheric conditions, such as temperature and relative humidity. Lastly, the paper provides information regarding the implementation of these models within American Electric Power’s (AEP’s) safety practices regarding batteries and DC panelboards.

Study Design: Retrospective review of a single institution. Objective: To determine if resting leg pain level is a predictor of success for indirect decompression in the setting of lumbar spinal stenosis, with lower levels of rest pain correlating with greater likelihood of successful indirect decompression. Methods: Reviewed anterior or lateral lumbar interbody fusions from T12 to L5-S1 patients with a posterior-based pedicle screw-rod construct. Patients were separated into 2 groups based on a preoperative response to Oswestry Disability Index (ODI) Question 7 regarding level of pain at rest in the supine position. Responses of 0 to 2 (minimal rest pain) were group 1 (n = 54) and responses of 3 to 5 (significant rest pain) were group 2 (n = 16). Results: Preoperative difference was detected between groups 1 and 2, in ODI (38 vs 63, P < .001) and Numeric Rating Scale (NRS) back (6.8 vs 7.9, P = .023). Three-month NRS leg and back scores were significantly lower in group 1 (leg, 1.9 vs 4.8, P < .001; back, 3.5 vs 6.4, P = .001). A significant difference was further noted in the percentage decrease in NRS leg and back scores from pre- to 3 months postoperatively between groups 1 and 2 (leg, 68.4% vs 22.7%, P < .001; back, 40.0% vs 7.4%, P = .012). Group 1 reached minimal clinically important difference for leg pain more often than group 2 (83.3% vs 43.8%, P = .001). Conclusion: Preoperative assessment of rest pain level in the supine position has a significant association with reduction in NRS leg and back scores in patients undergoing indirect decompression for lumbar spinal stenosis. This tool may successfully indicate which patients will be candidates for indirect decompression with interbody fusion from an anterior or lateral approach.

Prospectively collected survey study OBJECTIVE.: The aim of this study was to determine the consistency with which spinopelvic parameters (SPP) are determined in patients with lumbosacral transitional vertebrae (LSTV).The incidence of LSTV in the general population is as high as 35.6%. The often fixed nature of LSTV relative to the pelvis, but lumbar-type appearance, may lead to differential use of the S1 endplate when performing SPP assessment. This could have significant impact on SPP derived from these landmarks, resulting in considerable variation in surgical planning and decision-making.Twenty patients demonstrating LSTV on standing lateral 36-inch spinal radiographs were randomly arranged and independently analyzed by 16 experienced spine surgeons using the same computer software. Pelvic incidence (PI), pelvic tilt (PT), lumbar lordosis (LL), and T1 pelvic angle (TPA) were captured. Two weeks after the first assessment, surgeons repeated the measurements after image sequence re-randomization. Intraclass correlation coefficient (ICC) was calculated to evaluate interobserver reliability (IOR) for each SPP. Intraobserver reliability (IAOR) was assessed through an average Pearson correlation coefficient for each parameter for each surgeon.Sixteen surgeons completed initial measurements. IOR was poor for TPA (0.35, 95% confidence interval [CI] 0.20, 0.58) and PI (0.42, 95% CI 0.26, 0.65) and fair for LL (0.67, 95% CI 0.51, 0.82), and PT (0.63, 95% CI 0.47, 0.81). Fourteen surgeons completed phase-2 measurements to assess IAOR. Average parameter PPC showed excellent IAOR (LL 0.86, TPA 0.77, PI 0.78, PT 0.86). Kappa coefficient showed fair agreement for raters choosing the same endplate for measurement (Phase 1: 0.38, Phase 2: 0.32). By patient, the percentage of raters that chose the S1 endplate for measurement varied from 6.3% to 85.7%.Significant variability exists when surgeons measure SPP in patients with LSTV. These parameters are critical in determining the goals of surgical reconstruction and such variability may have considerable implications for radiographic goals and outcomes of surgical reconstruction.4.

Microgrids with distributed energy resources are being favored in various communities to lower the dependence on utility-supplied energy and cut the CO2 emissions from coal-based power plants. This paper presents a co-optimization strategy for distributed energy resource planning to minimize total annualized cost at the maximal fuel savings. Furthermore, the proposed scheme aids the community microgrids in satisfying the requirements of U.S. Department of Energy (DOE) and state renewable energy mandates. The method of Lagrange multipliers is employed to maximize fuel savings by satisfying Karush-Kuhn-Tucker conditions. With the Fourier transform and particle swarm optimization, the right mix of distributed energy resources is determined to decrease the annualized cost. A case study to test the proposed scheme for a community microgrid is presented. To validate its effectiveness, an economic justification of the solution and its comparison with HOMER Pro are also illustrated., 10 pages, 7 figures, 8 tables, journal

Microgrids with increased penetration of renewables experience serious challenges due to large frequency excursions under power system disturbances. An energy storage system can provide frequency regulation, but the effectiveness depends on whether it is configured for the grid-forming or grid-following mode of operation. For this purpose, two critical parameters are studied for frequency regulation in distribution systems; first, the initial rate-of-change-of-frequency (ROCOF), and second, the minimum value of frequency, also known as frequency nadir, following a load change. The aim of this paper is to identify analytical methods for accurately calculating the frequency parameters like ROCOF and frequency nadir. Reduced-order models are developed to determine the frequency deviation against power system disturbances. The results are verified against simulation models validated by testing at the Consortium for Electric Reliability Technology Solutions Microgrid test bed.

This paper presents a novel modified Viterbi algorithm to identify the optimal distribution system restoration plan for improving the grid resiliency. In the proposed algorithm, the switching operations performed for system restoration are the states with the minimum bus voltage being seen as the cost metric for each state and the extent of load recovery as the observed event. When full load recovery is spotted, the dynamic programming algorithm stops, thereby giving the least number of switching pairs necessary for system restoration. Moreover, an improved flexible switching pair operation is employed to maintain the radial nature of distribution system. Several case studies are presented for verifying the performance of the proposed strategy. Multi-fault conditions are considered in testing the system restoration scheme on 33-bus and 69-bus distribution systems. Furthermore, the effects of integrating distributed energy resources and microgrid systems are analyzed., Comment: 10 pages, 11 figures, 7 tables, journal

Village or community microgrids are being encouraged to improve resiliency against unexpected events. They also improve energy efficiency and reliability of power delivery to critical loads. However, many protection challenges exist in making the shift away from conventional distribution systems. In this paper, a multilayered protection strategy is presented for developing a community microgrid in a village within the 69-bus distribution system. The proposed strategy is verified by simulation studies in MATLAB/Simulink against various fault conditions. A comparison between the proposed strategy and existing distribution protection schemes is also provided.

For a microgrid with a mix of distributed energy resources (DERs), major challenges on its survivability are found in the islanded condition. In particular, a sudden loss of generation or a large and fluctuating load could force the microgrid to operate near its capacity limits. Such a situation can cause a cascading collapse of the mixed-source microgrid, even when the load demand is within the system's power rating. This condition was observed during several tests carried out at the Consortium for Electric Reliability Technology Solutions Microgrid Test Bed. This paper analyzes the root causes behind the collapse. It highlights that the capacity of a low-inertia system to support load changes is contributed by faster responding DERs initially. Therefore, the microgrid is particularly susceptible if the faster responding DERs do not have adequate reserve margin. Two control methods are evaluated for providing safeguards to these DERs and prevent the system collapse.

Station batteries used as a backup source to supply station direct-current (DC) power to relays, etc., present a source of personnel exposure to DC arc flash. DC arc flash is less understood compared with the arc flash phenomena that occur in alternating-current (AC) systems. Some models exist to quantify the potential hazards posed by DC electrical systems; however., there is little empirical data available. Additionally., the lower-voltage and/or lower-capacity station batteries are even less researched. As a result., a series of arc flash tests were performed at Dolan Technology Center of American Electric Power (AEP) utilizing two 125 V dc batteries with rated capacities of 100 Ah and 150 Ah. For these tests, working distance and gap width were used as independent variables. Upon the conclusion of testing, various relationships were analyzed to generate a predictive model for incident energy. This model serves as a compilation of the empirical data collected during testing and will contribute to future research efforts to better understand DC arc flash incidents from station batteries.

Objectives Lateral lumbar interbody fusion (LLIF) is increasingly being utilized in isolation to achieve a large surface-area interbody fusion with an indirect decompression for spinal stenosis. This retrospective chart review was done to determine the viability of performing stand-alone (SA) LLIF. Methods Forty-nine patients at least 18 years of age with minimum one-year follow-up at a single institution underwent SA-LLIF using minimally invasive surgery (MIS) approach without further posterior surgery between 2011 and 2015. One to five-level fusions were included. Retrospective review of surgical outcomes and radiographic parameters were examined preoperatively, acutely postoperatively and at 1 year postoperatively. Results Forty-nine patients (102 spinal segments) underwent SA-LLIF. Fusion levels ranged from one to five with a mean of 2.1 ± 2.1. Mean blood loss was 68 ± 63.2cc and mean surgical time was 143.4 ± 66.5 minutes. Fifty-seven percent had undergone prior spine surgery unrelated to their index procedure. Complication rate was 38.9% and reoperation rate was 20.4%. No difference in complication rates was noted between constructs with three or more levels fused versus less than three levels fused. At one-year, significant improvement was noted with pelvic tilt, pelvic incidence, and lumbar lordosis. Conclusions SA-LLIF is an optional MIS treatment of stable degenerative disc disease and spinal stenosis, with good one-year correction and maintenance of radiographic parameters. With complication rate of 38.9% and reoperation rate of 20.4%, true benefit of forgoing posterior supplemental fixation may be questioned.

Minimally invasive surgery (MIS) correction for adult spinal deformity (ASD) may reduce the need the need for postoperative skilled nursing facility (SNF) or inpatient rehabilitation (IR) placement following surgery. The likelihood of requiring placement in a facility rather than home disposition may be influenced by various factors. In addition, the associations between discharge location and outcomes and complication rates have not been elucidated in these patients. In this study, we aimed to define factors predicting disposition to an SNF/IR and to elucidate the rates of complications occurring in patients sent to home versus to a facility.A retrospective review of a multicenter ASD database, which included patients who underwent surgery between 2009 and 2014. Inclusion criteria were age18 years, MIS as part of index surgery, location of discharge, and at least 1 of the following: pelvic tilt20°, sagittal vertical axis5 cm, pelvic incidence-lumbar lordosis mismatch10, or lumbar scoliosis20°. Patients with a 2-year follow-up were included. Preoperative demographic and radiographic data, postoperative (30 day) complications, and health-related quality of life were analyzed.A total of 182 patients met our inclusion criteria, including 113 who were discharged to home and 69 who were discharged to an SNF/IR. Older patients (50 years) were more likely to be discharged to an SNF/IR (P = 0.043). Those aged70 years were 6-fold more likely to go to an SNF/IR. No association was identified between discharge to an SNF/IR and any radiographic parameters except preoperative pelvic tilt (odds ratio [OR], 1.11; P = 0.009). Staged cases were more likely to be discharged to an SNF/IR (OR, 3.24; 95% confidence interval, 1.11-9.46; P = 0.032); otherwise, there was no difference in levels treated, operating time, estimated blood loss, osteotomy, or length of hospital stay. Patients requiring discharge to an SNF/IR had a higher rate of complications (58% vs. 39.8%; P = 0.017), including major complications (19.5% vs. 42%; P = 0.001), perioperative complications (14.2% vs. 31.9%; P = 0.004) and infections (3.5% vs. 13%; P = 0.016). Patients discharged to an SNF/IR had a higher rate of revision (19.5% vs. 33%; P = 0.035). Health-related quality of life measures were similar regardless of disposition.Older patients and those undergoing staged MIS deformity correction have a higher likelihood of postoperative disposition to an SNF/IR. Complications occurred more commonly in those patients requiring transfer to an SNF/IR after hospitalization.

We conducted a study to determine if knowledge of implant cost affects fixation method choice in the management of stable intertrochanteric hip fractures. We retrospectively reviewed the cases of 119 patients treated with a sliding hip screw (SHS; Versafix), a short Gamma nail (SGN), or a long Gamma nail (LGN). Of the 119 fractures, 71 were treated before implant costs were revealed, and 48 afterward. The 2 groups were similar in age, sex, fracture types, American Society of Anesthesiologists physical status classification, and preinjury ambulatory status. SHS was used in 38.0% of the before cases and 27.1% of the after cases, SGN in 29.6% of the before cases and 45.8% of the after cases, and LGN in 32.4% of the before cases and 27.1% of the after cases. Changes in implant use were not statistically significant. SHS was favored for 31-A1.1, 31-A1.2, and 31-A2.1 fractures in the before group but only for 31-A1.2 fractures in the after group. Gamma nails of both sizes were preferred in the after group for 31-A1.1, 31-A1.3, and 31-A2.1 fractures. At our institution, surgeon knowledge of implant cost did not affect fixation method choice in the management of stable intertrochanteric hip fractures.

With great interest, we read the response to our article, “Robotic-assisted pedicle screw placement fails to reduce overall postoperative complications in fusion surgery”. We would like to thank the authors for their time and attention to our work. We would also like to thank Dr. Theodore for his innovative contributions to the field of robotic-assisted spinal surgery. It is our opinion that the response underscores the significance of our study while correctly characterizing its limitations.

Adult spinal deformity is a common disorder with an increasing clinical and societal impact based on the aging demographic throughout the world. Adult spinal deformity in the adult population has a significant and measurable impact on health-related quality of life. A significant proportion of this affected populace will require treatment in some form or another. In general, the first-line of treatment is non-operative, but a subset will require operative intervention. Once surgical intervention is chosen, there are numerous methods that may provide surgeons with adequate tools for successful outcomes. The purpose of this review article is to discuss the importance of adult deformity in the spectrum of disorders that affect the spine, to define specific considerations that are useful in guiding an evidence-based approach to care, and to elaborate on the variety of surgical techniques for which to address the issue of spinal deformity.

BACKGROUND CONTEXT Conflicting reports exist in spine literature regarding short-term outcomes following cervical laminoplasty and posterior laminectomy and fusion. PURPOSE The objective of this study was to compare the 30-day outcomes for these two treatment groups for multilevel cervical pathology. STUDY DESIGN/SETTING Retrospective review of the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database years 2010-2015. PATIENT SAMPLE A total of 3,796 patients were included: 2,397 (63%) underwent cervical laminectomy and fusion and 1,399 (37%) underwent cervical laminoplasty. OUTCOME MEASURES Patient demographics, comorbidities, complications and outcomes compared between patients undergoing cervical laminoplasty or laminectomy and fusion. METHODS Patients who underwent cervical laminoplasty or posterior laminectomy and fusion were identified in the NSQIP database from 2010 to 2015 based on Current Procedural Terminology (CPT) code. Laminoplasty CPT codes included 63050 and 63051. Posterior cervical laminectomy CPT codes included 63015, 63045, and instrumentation was denoted by CPT code 22842. Patients with preoperative sepsis, wound infection, pneumonia, cancer, emergency cases and trauma, and surgery within the last 30days were excluded. Patient demographics and comorbidities were compared using bivariate logistic regression. Propensity-adjusted multivariate regressions were performed to assess differences in postoperative length of stay, adverse events, discharge disposition and readmission. RESULTS A total of 3,796 patients were included: 2,397 (63%) underwent cervical laminectomy and fusion and 1,399 (37%) underwent cervical laminoplasty. Both groups were similar in age, gender, body mass index (BMI), American Society of Anesthesiologists (ASA) score and Charlson Comorbidity Index (CCI) (P>.05 for all). Both groups had similar rates of malnutrition, chronic kidney disease (CKD), diabetes, chronic obstructive pulmonary disease, and history for steroid use. Age >70 and age .05 for all). Compared with laminoplasty patients, laminectomy and fusion patients had increased lengths of stay (LOS) (4.5vs. 3.7days, P .05 for all). Patients with CKD that underwent laminectomy and fusion had higher rates of transfusion (6.8vs. 20.4%, P=.05). Patients older than 70 that underwent laminectomy and fusion experienced high rates of urinary tract infection (6.4vs. 2.6%, P=.02). CONCLUSIONS Posterior cervical laminectomy and fusion patients were found to have increased LOS, readmissions, and complications despite having similar preoperative demographics and comorbidities. Patients and surgeons should consider these risks when considering surgical treatment for cervical pathology.

BACKGROUND CONTEXT Intra-wound application of vancomycin powder has demonstrated dramatic reductions of infection rate following lumbar laminectomy and fusion. The economic benefit of this prophylactic protocol has been previously validated for laminectomy and fusion, but the cost-effectiveness is less clear for lumbar laminectomy alone. PURPOSE The goal of this study is to demonstrate that application of vancomycin powder is a cost-effective method for preventing infection following lumbar laminectomy. STUDY DESIGN/SETTING Break-even cost analysis. OUTCOME MEASURES This study determined the magnitude by which the rate of infection following lumbar laminectomy alone and lumbar laminectomy and fusion would need to be reduced by in order to make application of vancomycin powder cost effective. METHODS The product cost of vancomycin powder was obtained from our institution's purchasing records. Total charges for lumbar laminectomy and lumbar laminectomy and fusion, rates of infection, and cost of revision were obtained from the literature. A break-even analysis [break-even infection rate=(initial infection rate−cost of protocol)/cost of treatment] was then performed to determine the absolute risk reduction (ARR) in infection rate to make prophylactic application of vancomycin powder cost effective. RESULTS Costing $3.06 per gram at our institution, vancomycin powder was determined to be cost-effective in lumbar laminectomy if the infection rates of 4.2% decreased by an ARR of 0.015%. Laminectomy and fusion was also determined to be cost effective at the same cost of vancomycin powder if the infection rate of 8.5% decreased by an ARR of 0.0034%. At the current highest cost reported in the literature, $44.00 per gram of vancomycin powder remained cost-effective with respective ARRs of 0.21% and 0.048% for laminectomy and laminectomy and fusion. Varying the baseline infection rate did not influence the ARR for either procedure when the analysis was performed using the product cost of vancomycin at our institution. CONCLUSIONS This break-even analysis demonstrates that prophylactic intra-wound application of vancomycin powder can be highly cost effective not only for lumbar laminectomy and fusion, but also for laminectomy alone. At our institution's price point, use of vancomycin powder is economically justified if it prevents at least one infection out of 6,700 lumbar laminectomy surgeries. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

For a microgrid with a mix of distributed energy resources (DERs), major challenges on its survivability are found in the islanded condition. In particular, a sudden loss of generation or a large and fluctuating load could force the microgrid to operate near its capacity limits. Such a situation can cause a cascading collapse of the system, even when the load demand is within the DER's kW rating — as observed during several tests at the Consortium for Electric Reliability Technology Solutions (CERTS) Microgrid Test Bed. This paper analyzes the prime-mover stalling phenomena behind the system collapse. It highlights how the reserve margin of the system is lowered during transient conditions. Furthermore, two control methods are evaluated to resolve the microgrid collapse problem.

Obesity complicates a number of diseases through mechanisms that are poorly defined. Mobilization and recruitment of progenitor cells to pathological sites is an important factor in disease progression. Here, we analyzed the influence of obesity on the systemic circulation of CD34(+) cell populations and correlated frequencies of cells displaying previously established cell marker signatures with the BMI. Comparative analysis of peripheral blood mononuclear cells (PBMC) from 12 nonobese (BMI30 kg/m(2)) and 14 obese (BMI30 kg/m(2)) disease-free donors by flow cytometry revealed that obesity is associated with a fivefold increased frequency of circulating progenitor cells (CPC), a population consisting of hematopoietic and endothelial precursors. Our data also indicate that obesity is associated with increased frequency of circulating mesenchymal stromal progenitor cells (MSC). In contrast, the frequencies of mature endothelial cells (EC) and CD34-bright leukocytes are unaffected by obesity. Combined, our results indicate that obesity promotes mobilization of progenitor cells, which may have clinical relevance.

BACKGROUND CONTEXT Anterior cervical discectomy and fusion (ACDF) is the most common surgical treatment for cervical disc pathology. However, recent evidence has demonstrated superior outcomes with cervical disc arthroplasty (CDA). PURPOSE This study aims to compare inpatient cost and length of stay (LOS) between cervical disc arthroplasty and anterior cervical discectomy and fusion. STUDY DESIGN/SETTING Retrospective cohort study. PATIENT SAMPLE A total of 676 patients were analyzed (338 ACDF and 338 CDA). The average patient ages for ACDF and CDA were 49.15 years and 49.11 years, respectively (p=.957). Only elective hospital admissions were included in this sample. Patients in the ACDF group were limited to those with one to two level fusions. OUTCOME MEASURES This study compared the ACDF and CDA cohorts on high-end hospital charges and prolonged inpatient length of stay. METHODS This study screened over 35 million hospital discharges in the United States from 2010 to 2014 using the National Inpatient Sample and the Nationwide Inpatient Sample. The International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedure codes were used to identify 75,377 patients who underwent ACDF of two or three vertebrae (ICD 81.02 and 81.62), and 387 patients who underwent CDA (ICD 84.62). The ACDF and CDA groups were statistically matched based on age, year of procedure, sex, indication for surgery, race, hospital type, and comorbidities. Mean hospital charges and LOS for each cohort were calculated and compared using the Kruskal Wallis H test. Univariate and multivariate logistic regression were used to compare high-end cost and prolonged LOS between the cohorts, defined as patients with LOS and total hospital charges greater than the 75th percentile of the respective means. RESULTS We matched 338 (87.34%) CDA patients with patients who underwent ACDF. The average LOS was greater for CDA (x=1.56, SD=0.946) compared to ACDF (x=1.43, SD=1.12; p=.001). Additionally, the average inpatient hospital charges for CDA were $21,320 (SD=10,854) compared to $16,123 (SD=8,499) for ACDF (p CONCLUSIONS Patients who underwent ACDF had significantly lower LOS and hospital charges than a statistically matched CDA cohort. This conclusion directly contradicts recent findings in the literature, although this study is the first to use a large cohort-matched analysis. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

BACKGROUND CONTEXT Surgeons have increasingly adopted robotic-assisted lumbar spinal fusion due to indications that robotic-assisted surgery can reduce the percentage of misplaced screws. However, the impact of robotic-assisted spinal fusion on patient outcomes is less clear. PURPOSE This study aims to compare rates of perioperative complications between robotic-assisted and conventional lumbar spinal fusion. STUDY DESIGN/SETTING Retrospective cohort study. PATIENT SAMPLE A total of 520 patients undergoing lumbar fusion were analyzed. The average ages of patients in the robotic-assisted versus conventional groups were 60.33 and 60.31, respectively (p=.987). Patients with a diagnosis of fracture, traumatic spinal cord injury, spina bifida, neoplasia, or infection were excluded. OUTCOME MEASURES This study compared the rates perioperative major and minor complications for elective lumbar fusion between each cohort. METHODS This study screened over 35 million hospital discharges in the United States from 2010 to 2014 using the National Inpatient Sample and the Nationwide Inpatient Sample (NIS). The International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedure codes were used to identify 209,073 patients who underwent conventional lumbar fusion (ICD 81.04-8) and 279 patients who underwent robotic-assisted lumbar fusion (ICD 81.04-8 and ICD 17.41, 17.49). Major and minor perioperative complications were identified using ICD-9-CM diagnosis codes. Patient mortality was determined using the uniform bill patient disposition. The robotic-assisted and conventional fusion groups were statistically matched on age, year of procedure, sex, surgical indication, race, hospital type, and comorbidities. Mean hospital cost and length of stay (LOS) for each cohort were calculated and compared using the Kruskal Wallis H test. Univariate and multivariate logistic regression were used to compare risks of major and minor complications between the cohorts. RESULTS We matched 260 (93.19%) robotic-assisted patients with patients undergoing conventional lumbar fusion. Too few patients in each cohort died to report the mortality rate based on NIS minimum reporting standards. Minor complications occurred in 16.9% of the conventional group and 32.7% of the robotic-assisted group (p CONCLUSIONS In a statistically matched cohort, patients undergoing robotic-assisted elective lumbar fusion had similar rates of major and minor complications compared to patients who underwent conventional lumbar fusion. Additionally, patients in the robotic-assisted cohort had significantly longer LOS and incurred greater hospital costs. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

New measures for increasing energy efficiency and reducing CO2 emissions are being introduced by several nations to tackle the growing concerns on climate change. This paper presents optimal distributed energy resource (DER) planning for establishing microgrids. Such microgrid systems are devised for industrial sites and campus communities in the United States after evaluating location specific DER options. These are designed to maximize fuel consumption savings, besides meeting the U.S. Department of Energy (DOE) requirements and state renewable energy mandates. A qualitative evaluation of various types of DERs is presented cogitating factors like cost, environment, fuel consumption, controllability, longevity and government policy. Furthermore, the method of Lagrange Multipliers is used to determine the optimal allocation of DERs for microgrids. Due consideration is given to various factors such as climatic conditions, prevailing energy resources, and environmental regulations. The planning strategy presented in this paper can be extended to other conditions with minimal adjustments.

This paper investigates the benefits of smart loads in an industrial microgrid. Such smart loads offer the microgrid greater flexibility to regulate frequency for large fluctuating load scenarios, commonly encountered in industrial plants. A case study of stone crushing facility is analyzed when it is fed by natural gas engine driven generator sets (also known as ‘gensets’). The problem of genset stalling is addressed in this work, and a solution of deploying smart loads is presented. Furthermore, smart load algorithms are proposed to restore the services at industrial sites in a timely manner.

Natural gas powered distributed energy resources (DERs) are gaining more popularity due to the recent discoveries of huge natural gas reserves in several places. These DERs however suffer from the tendency to stall under large load fluctuations owing to the fuel map limits present in the engine governors and the inherent time lag in torque production. A critical analysis of the stalling causes is conducted for a natural gas engine powered synchronous generator (referred as genset) that was installed in the CERTS Microgrid. The grazing phenomenon is explored for analyzing the stalling behavior. Simulation studies are performed for different test case scenarios, and it is shown that such DER units can operate reliably near their rated capacity without stalling if the load changes are effected in a proper manner. The ability to handle load changes in such gensets without the need for any load reliefs is analyzed and the possible solutions are discussed for avoiding such stalling occurrence.

Dysplasia epiphysealis hemimelica (DEH), or Trevor’s disease, is an osteocartilaginous epiphyseal overgrowth typically occurring in children. The literature reports 6 adult cases and none describe recurrence requiring additional procedures. We present a new-onset proximal tibial DEH in an adult recurring approximately 3 years after open excision. A 39-year-old female presented with a history of right knee pain, swelling, and instability. Physical examination revealed a firm proximal tibial mass. Computed tomography (CT) imaging showed an exophytic, lobulated, sclerotic mass involving the anterolateral margin of the lateral tibial plateau. Magnetic resonance imaging was suggestive of an osteochondroma. The patient underwent curettage of the lesion due to its periarticular location. Histology revealed benign and reactive bone and cartilage consistent with periosteal chondroma. Two and a half years later, the patient presented with a firm, palpable mass larger than the initial lesion. CT revealed a lateral tibial plateau sclerotic mass consistent with recurrent intra-articular DEH. A complete excision was performed and histology showed sclerotic bone with overlying cartilage consistent with exostosis. DEH is a rare epiphyseal osteocartilaginous outgrowth frequently occurring in the long bones of children less than 8 years old. DEH resembles an osteochondroma due to its pediatric presentation and similar histologic appearance. Adult-onset cases comprise less than 1% of reported cases. Recurrence rate after surgical intervention is unknown. Only 1 such case, occurring in a child, has been described. Clinicians contemplating operative treatment for DEH should note the potential for recurrence and consider complete excision. A follow-up period of several years may be warranted to identify recurrent lesions.

Background and purpose Although plating is considered to be the treatment of choice in distal tibia fractures, controversies abound regarding the type of plating for optimal fixation. We conducted a systematic review to evaluate and compare the outcomes of locked plating and non-locked plating in treatment of distal tibia fractures. Patients and methods A systematic review was conducted using PubMed to identify articles on the outcomes of plating in distal tibia fractures that were published up to June 2012. We included English language articles involving a minimum of 10 adult cases with acute fractures treated using single-plate, minimally invasive techniques. Study-level binomial regression on the pooled data was conducted to determine the effect of locking status on different outcomes, adjusted for age, sex, and other independent variables. Results 27 studies met the inclusion criteria and were included in the final analysis of 764 cases (499 locking, 265 non-locking). Based on descriptive analysis only, delayed union was reported in 6% of cases with locked plating and in 4% of cases with non-locked plating. Non-union was reported in 2% of cases with locked plating and 3% of cases with non-locked plating. Comparing locked and non-locked plating, the odds ratio (OR) for reoperation was 0.13 (95% CI: 0.03–0.57) and for malalignment it was 0.10 (95% CI: 0.02–0.42). Both values were statistically significant. Interpretation This study showed that locked plating reduces the odds of reoperation and malalignment after treatment for acute distal tibia fracture. Future studies should accurately assess causality and the clinical and economic impact of these findings.

This paper presents a new methodology for quantifying compressor endwall blockage and an approach, using this quantification, for defining the links between design parameters, flow conditions, and the growth of blockage due to tip clearance flow. Numerical simulations, measurements in a low-speed compressor, and measurements in a wind tunnel designed to simulate a compressor clearance flow are used to assess the approach. The analysis thus developed allows predictions of endwall blockage associated with variations in tip clearance, blade stagger angle, inlet boundary layer thickness, loading level, loading profile, solidity, and clearance jet total pressure. The estimates provided by this simplified method capture the trends in blockage with changes in design parameters to within 10 percent. More importantly, however, the method provides physical insight into, and thus guidance for control of, the flow features and phenomena responsible for compressor endwall blockage generation.