Harvesting local cylinder autograft from adjacent vertebral body for anterior lumbar interbody fusion: surgical technique, operative feasibility and preliminary clinical results

Autogenous iliac crest has long served as the gold standard for anterior lumbar arthrodesis although added morbidity results from the bone graft harvest. Therefore, femoral ring allograft, or cages, have been used to decrease the morbidity of iliac crest bone harvesting. More recently, an experimental study in the animal showed that harvesting local bone from the anterior vertebral body and replacing the void by a radio-opaque beta-tricalcium phosphate plug was a valid concept. However, such a concept precludes theoretically the use of posterior pedicle screw fixation. At one institution a consecutive series of 21 patients underwent single- or multiple-level circumferential lumbar fusion with anterior cages and posterior pedicle screws. All cages were filled with cancellous bone harvested from the adjacent vertebral body, and the vertebral body defect was filled with a beta-tricalcium phosphate plug. The indications for surgery were failed conservative treatment of a lumbar degenerative disc disease or spondylolisthesis. The purpose of this study, therefore, was to report on the surgical technique, operative feasibility, safety, benefits, and drawbacks of this technique with our primary clinical experience. An independent researcher reviewed all data that had been collected prospectively from the onset of the study. The average age of the patients was 39.9 (26-57) years. Bone grafts were successfully harvested from 28 vertebral bodies in all but one patient whose anterior procedure was aborted due to difficulty in freeing the left common iliac vein. This case was converted to a transforaminal interbody fusion (TLIF). There was no major vascular injury. Blood loss of the anterior procedure averaged 250 ml (50-350 ml). One tricalcium phosphate bone plug was broken during its insertion, and one endplate was broken because of wrong surgical technique, which did not affect the final outcome. One patient had a right lumbar plexopathy that was not related to this special technique. There was no retrograde ejaculation, infection or pseudoarthrosis. One patient experienced a deep venous thrombosis. At the last follow up (mean 28 months) all patients had a solid lumbar spine fusion. At the 6-month follow up, the pain as assessed on the visual analog scale (VAS) decreased from 6.9 to 4.5 (33% decrease), and the Oswestry disability index (ODI) reduced from 48.0 to 31.7 with a 34% reduction. However, at 2 years follow up there was a trend for increase in the ODI (35) and VAS (5). The data in this study suggest that harvesting a cylinder of autograft from the adjacent vertebral body is safe and efficient. Filling of the void defect with a beta-tricalcium phosphate plug does not preclude the use of posterior pedicle screw stabilization.

Osseointegration of hollow cylinder based spinal implants in normal and osteoporotic vertebrae: a sheep study

INTRODUCTION: Osteoporosis is not only responsible for an increased number of metaphyseal and spinal fractures but it also complicates their treatment. To prevent the initial loosening, we developed a new implant with an enlarged implant/bone interface based on the concept of perforated, hollow cylinders. We evaluated whether osseointegration of a hollow cylinder based implant takes place in normal or osteoporotic bone of sheep under functional loading conditions during anterior stabilization of the lumbar spine. MATERIALS AND METHODS: Osseointegration of the cylinders and status of the fused segments (ventral corpectomy, replacement with iliac strut, and fixation with testing implant) were investigated in six osteoporotic (age 6.9 +/- 0.8 years, mean body weight 61.1 +/- 5.2 kg) and seven control sheep (age 6.1 +/- 0.2 years, mean body weight 64.9 +/- 5.7 kg). Osteoporosis was introduced using a combination protocol of ovariectomy, high-dose prednisone, calcium and phosphor reduced diet and movement restriction. Osseointegration was quantified using fluorescence and conventional histology; fusion status was determined using biomechanical testing of the stabilized segment in a six-degree-of-freedom loading device as well as with radiological and histological staging. RESULTS: Intact bone trabeculae were found in 70% of all perforations without differences between the two groups (P = 0.26). Inside the cylinders, bone volume/total volume was significantly higher than in the control vertebra (50 +/- 16 vs. 28 +/- 13%) of the same animal (P<0.01), but significantly less (P<0.01) than in the near surrounding (60 +/- 21%). After biomechanical testing as described in Sect. "Materials and methods", seven spines (three healthy and four osteoporotic) were classified as completely fused and six (four healthy and two osteoporotic) as not fused after a 4-month observation time. All endplates were bridged with intact trabeculae in the histological slices. CONCLUSIONS: The high number of perforations, filled with intact trabeculae, indicates an adequate fixation; bridging trabeculae between adjacent endplates and tricortical iliac struts in all vertebrae indicates that the anchorage is adequate to promote fusion in this animal model, even in the osteoporotic sheep.

Cylinder wall waste heat recovery from liquid-cooled internal combustion engines utilizing thermoelectric generators

This report is a dissertation proposal that focuses on the energy balance within an internal combustion engine with a unique coolant-based waste heat recovery system. It has been predicted by the U.S. Energy Information Administration that the transportation sector in the United States will consume approximately 15 million barrels per day in liquid fuels by the year 2025. The proposed coolant-based waste heat recovery technique has the potential to reduce the yearly usage of those liquid fuels by nearly 50 million barrels by only recovering even a modest 1% of the wasted energy within the coolant system. The proposed waste heat recovery technique implements thermoelectric generators on the outside cylinder walls of an internal combustion engine. For this research, one outside cylinder wall of a twin cylinder 26 horsepower water-cooled gasoline engine will be implemented with a thermoelectric generator surrogate material. The vertical location of these TEG surrogates along the water jacket will be varied along with the TEG surrogate thermal conductivity. The aim of this proposed dissertation is to attain empirical evidence of the impact, including energy distribution and cylinder wall temperatures, of installing TEGs in the water jacket area. The results can be used for future research on larger engines and will also assist with proper TEG selection to maximize energy recovery efficiencies.

Implementation of a Variable Compression Ratio Mechanism in a Four Cylinder Engine

Ever since the invention of the internal combustion engine, generating more power and achieving better efficiency has been a major goal for the designers. Variable compression ratio technology is way to achieve those goals. This paper will discuss the method of varying the compression ratio of an inline 4-cylinder engine through the use of a 4-bar linkage and gear mechanism. This mechanism was proven to easily vary the compression ratio of the engine and shows promise of becoming a technology used for future engine designer.

Analysis of in-cylinder pressure transducer data quality utilizing a SIDI turbocharged engine

In-cylinder pressure transducers have been used for decades to record combustion pressure inside a running engine. However, due to the extreme operating environment, transducer design and installation must be considered in order to minimize measurement error. One such error is caused by thermal shock, where the pressure transducer experiences a high heat flux that can distort the pressure transducer diaphragm and also change the crystal sensitivity. This research focused on investigating the effects of thermal shock on in-cylinder pressure transducer data quality using a 2.0L, four-cylinder, spark-ignited, direct-injected, turbo-charged GM engine. Cylinder four was modified with five ports to accommodate pressure transducers of different manufacturers. They included an AVL GH14D, an AVL GH15D, a Kistler 6125C, and a Kistler 6054AR. The GH14D, GH15D, and 6054AR were M5 size transducers. The 6125C was a larger, 6.2mm transducer. Note that both of the AVL pressure transducers utilized a PH03 flame arrestor. Sweeps of ignition timing (spark sweep), engine speed, and engine load were performed to study the effects of thermal shock on each pressure transducer. The project consisted of two distinct phases which included experimental engine testing as well as simulation using a commercially available software package. A comparison was performed to characterize the quality of the data between the actual cylinder pressure and the simulated results. This comparison was valuable because the simulation results did not include thermal shock effects. All three sets of tests showed the peak cylinder pressure was basically unaffected by thermal shock. Comparison of the experimental data with the simulated results showed very good correlation. The spark sweep was performed at 1300 RPM and 3.3 bar NMEP and showed that the differences between the simulated results (no thermal shock) and the experimental data for the indicated mean effective pressure (IMEP) and the pumping mean effective pressure (PMEP) were significantly less than the published accuracies. All transducers had an IMEP percent difference less than 0.038% and less than 0.32% for PMEP. Kistler and AVL publish that the accuracy of their pressure transducers are within plus or minus 1% for the IMEP (AVL 2011; Kistler 2011). In addition, the difference in average exhaust absolute pressure between the simulated results and experimental data was the greatest for the two Kistler pressure transducers. The location and lack of flame arrestor are believed to be the cause of the increased error. For the engine speed sweep, the torque output was held constant at 203 Nm (150 ft-lbf) from 1500 to 4000 RPM. The difference in IMEP was less than 0.01% and the PMEP was less than 1%, except for the AVL GH14D which was 5% and the AVL GH15DK which was 2.25%. A noticeable error in PMEP appeared as the load increased during the engine speed sweeps, as expected. The load sweep was conducted at 2000 RPM over a range of NMEP from 1.1 to 14 bar. The difference in IMEP values were less 0.08% while the PMEP values were below 1% except for the AVL GH14D which was 1.8% and the AVL GH15DK which was at 1.25%. In-cylinder pressure transducer data quality was effectively analyzed using a combination of experimental data and simulation results. Several criteria can be used to investigate the impact of thermal shock on data quality as well as determine the best location and thermal protection for various transducers.

Multiphase Screen Development

This honors thesis research project was the study and development of a compact separation device for the oil and gas industry involving a multiphase cylindrical screen filter. Cylindrical screens can be used for solids removal in multiphase flow in upstream oil and gas applications. This study focused on cylindrical wire-wrap screen test unit design and performance characterization to determine volumetric flow rate and pressure drop correlations. The project goals were met with research, test unit design, CFD modeling, calculations, and physical testing. The comprehensive testing will take place during the summer of 2013 and is planned to consist of building the designed flowloop and housing and using high capacity pumps to achieve higher flow rates. Multiphase testing will be performed with water, air, and sand particles and flow and pressure effects will be evaluated for solids filtering over time.

Prostate cancer: to screen or not to screen?

Unfortunately, interim analyses of the long-awaited ERSPC and PLCO trial data have generated conflicting conclusions. Here, two European authors speculate as to the reasons underlying this contradiction, while highlighting clinically relevant points that are supported by both studies. Particular attention is paid to the potential consequences of overdiagnosis and overtreatment.

Secondary arterial hypertension: when, who, and how to screen?

Secondary hypertension refers to arterial hypertension due to an identifiable cause and affects ∼5-10% of the general hypertensive population. Because secondary forms are rare and work up is time-consuming and expensive, only patients with clinical suspicion should be screened. In recent years, some new aspects gained importance regarding this screening. In particular, increasing evidence suggests that 24 h ambulatory blood pressure (BP) monitoring plays a central role in the work up of patients with suspected secondary hypertension. Moreover, obstructive sleep apnoea has been identified as one of the most frequent causes. Finally, the introduction of catheter-based renal denervation for the treatment of patients with resistant hypertension has dramatically increased the interest and the number of patients evaluated for renal artery stenosis. We review the clinical clues of the most common causes of secondary hypertension. Specific recommendations are given as to evaluation and treatment of various forms of secondary hypertension. Despite appropriate therapy or even removal of the secondary cause, BP rarely ever returns to normal with long-term follow-up. Such residue hypertension indicates either that some patients with secondary hypertension also have concomitant essential hypertension or that irreversible vascular remodelling has taken place. Thus, in patients with potentially reversible causes of hypertension, early detection and treatment are important to minimize/prevent irreversible changes in the vasculature and target organs.

The Impact of a Brief Intervention on Medical Students' Readiness to Screen for DV - Changes in Decisional Balance and Self-Efficacy

Introduction: Domestic violence (DV) affects millions of Americans each year. Yet, there is a dearth of theory-based DV curricula, resulting in physicians unprepared to screen for DV. This study utilized a survey based on constructs from the Transtheoretical Model to assess the readiness of first- and second-year medical students to screen for DV. Information from this survey will be used to help institutionalize DV education into the medical curriculum. [See PDF for complete abstract]

Health Care Providers' Training Needs Related to Human Trafficking: Maximizing the Opportunity to Effectively Screen and Intervene

Human trafficking is a complex and multifaceted problem that takes the form of economic, physical and sexual exploitation of people, both adults and children, who are reduced to simple products for commerce. Human trafficking in the United States also has both a domestic and an international aspect. Health care providers are in a unique position to screen for victims of trafficking and may provide important medical and psychological care for victims while in captivity and thereafter. Trafficked persons are likely to suffer a wide spectrum of health risks that reflect the unique circumstances and experiences in a trafficked victim’s life. Although trafficked victims typically have experienced inadequate medical care, once contact is made by the victim with the health care professionals, the opportunity then exists to identify, treat, and assist such victims. The range of services and supports required to appropriately respond to human trafficking victims once identified is broad and typically goes beyond just what is immediately provided by the health care professional and includes safe housing, legal advice, income support, and, for international victims, immigration status related issues. An informed and responsive community is necessary to serve both the international and domestic victims of human trafficking, and needs assessments demonstrated a number of barriers that hindered the delivery of effective services to human trafficking victims. One of the consistent needs identified to combat these barriers was enhanced training among all professionals who might come in contact with human trafficking victims. We highlight the efforts of the Houston Rescue and Restore Coalition (HRRC), a local grassroots non-profit organization whose mission focuses on raising awareness of human trafficking in the Greater Houston Metropolitan area. HRRC responded to the consistent recommendation from various community needs assessments for additional training of front line professionals who would have the opportunity to identify human trafficking victims and supported the design and pilot testing of a health professions training program around human trafficking. Dissemination of this type of training along with careful evaluation and continued refinement will be one way for health care professionals to engage in a positive manner with human trafficking victims.

Using micropower impulse radar technology to screen for pneumothorax: an international bi-institutional study. Corrigendum

In an article in the December 2012 issue of The Journal of Trauma and Acute Care Surgery, several author names were misprinted.