Craig-Scott orthosis: a biochemical and functional evaluation

The Craig-Scott double upright knee ankle orthosis was subjected to a biomechanical evaluation which included analysis of the force interaction with the supported limb and a functional evaluation. The results were compared with data previously determined from biomechanical evaluations of other common orthoses. In the Craig-Scott design, the single application of the knee stabilizing force below the knee concentrates this force in a relatively small bony area, sometimes exceeding tolerance. This might be avoided by using a tibial closure with patellar tendon bearing features. The design was found to produce relatively low anatomic knee shear. In functional aspects such as donning, doffing, transfers and ambulation, the orthosis is essentially equivalent to other double upright designs. The rigidity of the orthosis with only a tibial band closure and a bail connecting the uprights was determined to be adequate. The limited number of bands and closures provides some advantages in reduced donning and doffing time; however, in the absence of posterior closures below the knee, the orthosis had a tendency to slide forward off the leg when transferring. This disadvantage was eliminated by adding a soft posterior closure below the knee, which produced a minimal increase in donning and doffing times.     

In vivo measurement of implant loads in a patient with a fractured vertebral body

For several medical interventions, increasing experience results in improved outcome. This finding may result from better patient selection or increased skill levels. This report examines whether there is a relationship between center experience and patient outcome for liver transplantation, and if so, whether the relationship is explained by patient or donor selection or level of experience required to obtain optimal results. The United Network for Organ Sharing Scientific Liver Transplant Registry includes all procedures performed in the United States since October 1987. The date of the first transplantation and the number of operations performed were used to define 42 new and 27 experienced centers. Within new centers, experience was quantified by the sequence number of each transplantation. Characteristics of 6,180 recipients and donors were compared between new and experienced centers using the chi 2 test for association. A linear trend test identified whether these characteristics varied with experience within new centers. The independent association between experience in new centers and perioperative mortality was examined using logistic regression. Patient and donor selection criteria differ between experienced and new centers and change within new centers as experience is gained. Adjusting for calendar year and various patient and donor characteristics, perioperative mortality rates decrease in new centers as experience is gained. After 20 transplantations are performed, perioperative mortality in new centers is not significantly different than that in experienced centers. Criteria for recipient and donor selection change as centers gain experience. Despite these differences and improvements that have occurred over time, increasing experience in centers performing liver transplantations is associated with reduced perioperative mortality.     

Modeling and simulation of paraplegic ambulation in a reciprocating gait orthosis

We developed a three dimensional, four segment, eight-degree-of-freedom model for the analysis of paraplegic ambulation in a reciprocating gait orthosis (RGO). Model development was guided by experimental analysis of a spinal cord injured individual walking in an RGO with the additional assistance of arm crutches. Body forces and torques required to produce a dynamic simulation of the RGO gait swing phase were found by solving an optimal control problem to track the recorded kinematics and ground reaction forces. We found that high upper body forces are required, not only during swing but probably also during double support to compensate for the deceleration of the body during swing, which is due to the pelvic thrust necessary to swing the leg forward. Other stimulations showed that upper body forces and body deceleration during swing can be reduced substantially by producing a ballistic swing. Functional neuromuscular stimulation of the hip musculature during double support would then be required, however, to establish the initial conditions needed in a ballistic swing.     

升力测量技术在减摇鳍控制系统中的应用

基于升力反馈控制减摇鳍系统,分析升力测量原理及所存在的非线性特性,并在升力控制减摇鳍伺服系统中采用升力/鳍角综合控制减摇鳍控制方法,修正升力反馈信号的检测问题.构建基于小波降噪的数据融合模型,该模型综合升力、鳍角传感器不同频带信息,消除信息之间的冗余和矛盾,利用信息之间的互补来获得对升力信号相对完整一致的描述.仿真结果表明,应用数据融合模型的控制系统在各种海况下均可达到良好平稳的减摇效果.     

Evaluation of levator muscle integrity in ptosis with levator force measurement

PURPOSE: To determine the efficacy of the force the levator muscle can generate as a diagnostic tool for ascertaining the cause of ptosis. METHODS: A total of 187 patients with ptosis were evaluated clinically, their levator force was measured, and each ptotic eyelid subsequently had surgical correction. At each step, patients received a diagnosis of congenital or acquired (history- dependent) aponeurotic, myogenic, neurogenic, or mechanical ptosis. To measure the levator force, a clamp placed on the upper eyelid lashes was attached to a force transducer. The maximum force generated on upgaze was recorded as the levator force. Data from healthy subjects were used to determine whether each levator muscle of the ptotic eyelids produced normal or less than normal force. The correct diagnosis was considered to be the diagnosis based on the findings at the time of surgery. The diagnosis of each patient with ptosis determined by eyelid excursion, eyelid excursion plus examination, levator force, and the levator force plus examination results were compared with the correct diagnosis. RESULTS: Eyelid excursion predicted the correct diagnosis 78.2% of the time. When eyelid excursion was combined with the examination results, the diagnosis was correct 84.0% of the time. Levator force predicted the correct diagnosis 95.2% of the time. When levator force was combined with the examination, the diagnosis was correct 97.9% of the time. CONCLUSION: Diagnosis of the cause of ptosis based on levator force measurement is significantly more accurate than when the diagnosis is based on eyelid excursion, even when information obtained on examination also is considered. Levator force measurement should be an integral part of ptosis evaluation.     

The measurement of oxygen in vivo using EPR techniques

The measurement of pO2 in vivo using EPR has some features which have already led to very useful applications and this approach is likely to have increasingly wide and effective use. It is based on the effect of oxygen on EPR spectra which provides a sensitive and accurate means to measure pO2 quantitatively. The development of oxygen-sensitive paramagnetic materials which are very stable, combined with instrumental developments, has been crucial to the in vivo applications of this technique. The physical basis and biological applications of in vivo EPR oximetry are reviewed, with particular emphasis on the use of EPR spectroscopy at 1 GHz using particulate paramagnetic materials for the repetitive and non-invasive measurement of pO2 in tissues. In vivo EPR has already produced some very useful results which have contributed significantly to solving important biological problems. The characteristics of EPR oximetry which appear to be especially useful are often complementary to existing techniques for measuring oxygen in tissues. These characteristics include the capability of making repeated measurements from the same site, high sensitivity to low levels of oxygen, and non-invasive options. The existing techniques are especially useful for studies in small animals, where the depth of measurements is not an overriding issue. In larger animals and potentially in human subjects, non-invasive techniques seem to be immediately applicable to study phenomena very near the surface (within 10 mm) while invasive techniques have some very promising uses. The clinical uses of EPR oximetry which seem especially promising and likely to be undertaken in the near future are long-term monitoring of the status and response to treatment of peripheral vascular disease and optimizing cancer therapy by enabling it to be modified on the basis of the pO2 measured in the tumour.     

In-shoe biaxial shear force measurement: the Kent shear system

Involvement of the nail unit in pemphigus vulgaris is thought to be uncommon. However, trachyonychia, nail atrophy, onychomadesis, onycholysis, nail bed erosion, onychoschizia, subungual haemorrhage, nail pitting, nail plate discoloration, cross-ridging of nail plate, Beau's line and paronychia have been reported. These manifestations may be due either to secondary extension of the bulla adjacent to the nail or primary involvement of the nail bed, nail matrix and nail fold. We report four patients with pemphigus vulgaris who developed paronychia with a corresponding exacerbation of their cutaneous lesions. Nail fold biopsy and direct immunofluorescence revealed features of permphigus vulgaris. Treatment with immunosuppressive agents showed simultaneous improvement of both cutaneous and nail lesions.     

Coercive force, texture, and fracture in a low-carbon steel tube

The coercive force and crystallographic texture in a tube made from ferrite low-carbon steel are studied after fatigue and tensile tests during fracture after cyclic loading by hydraulic pressure. The texture was studied using synchrotron radiation (transmission geometry) by constructing three-dimensional distribution function of orientations. The typical texture of rolling of the ferrite steel is maximal in the median cross section of the tube wall, and the highest texture intensity is due to deformation preceding fracture. The coercive force is found to increase in portions neighboring to the fracture zone.     

Direct measurement of hydrogen bonding in DNA nucleotide bases by atomic force microscopy

We have used self-assembled purines and pyrimidines on planar gold surfaces and on gold-coated atomic force microscope (AFM) tips to directly probe intermolecular hydrogen bonds. Electron spectroscopy for chemical analysis (ESCA) and thermal programmed desorption (TPD) measurements of the molecular layers suggested monolayer coverage and a desorption energy of about 25 kcal/mol. Experiments were performed under water, with all four DNA bases immobilized on AFM tips and flat surfaces. Directional hydrogen-bonding interaction between the tip molecules and the surface molecules could be measured only when opposite base-pair coatings were used. The directional interactions were inhibited by excess nucleotide base in solution. Nondirectional van der Waals forces were present in all other cases. Forces as low as two interacting base pairs have been measured. With coated AFM tips, surface chemistry-sensitive recognition atomic force microscopy can be performed.     

平板剪切机剪切力的光电测定分析法

本文介绍了一种光电混合测定方法。由于被分析的剪切机设备结构紧凑、被测零件又不允许破坏以及连杆在工作时处于二向应力状态等特点,用单一的电测方法不能得到测定结果。为此,本文应用光弹性分析理论及电测理论的综合讨论,导出了一组混合测定法的计算公式,从而为复杂工程问题的载荷实测提供了一种分析方法。     

Gait function in spastic hemiparetic patients walking barefoot, with firm shoes, and with ankle-foot orthosis

Cortical spreading depression is a wave of electrical and biochemical changes that spreads across the cerebral cortex. It has been hypothesized to be an important underlying cause of the visual disturbances occurring during the migraine aura, but this is difficult to test in animals or humans. We created a computational model of cortical spreading depression and found that during the wave of biochemical changes the spatial pattern of neural activity broke up into irregular patterns of lines and small patches of highly activated elements. The corresponding visual disturbances that would be produced by these patterns of neural activity resemble the hallucinations reported during the migraine aura, providing strong support for the cortical spreading depression hypothesis of migraine. The model also makes the testable prediction that these hallucinations move at an exponentially increasing speed across the visual field.     

Optimisation of a polarised X-ray source for the in vivo measurement of platinum in head and neck tumours

There is a continuing need to improve the understanding of kinetics of platinum-based chemotherapeutic agents, such as cisplatin and paraplatin. Although these agents demonstrate highly effective anti-cancer activity, they also have associated, often dose-limiting, side-effects such as nephrotoxocity. In vivo X-ray fluorescence (XRF) has been proven to be a suitable technique for measuring the uptake of these agents in tumour and critical organs, but radioisotope based systems have not found their way into routine clinical use due to their rapid increase in minimum detection limit (MDL) with depth. Polarised X-rays offer a solution to this problem by reducing the scattered background, which not only reduces the MDL, but also allows the intensity of the source to be increased without saturating the detector electronics. This paper describes the development and optimisation of a polarised XRF system for in vivo measurement of platinum in head and neck tumours, whose response to cisplatin is often unpredictable. The polarised X-ray source comprises a clinical X-ray therapy unit (the Pantak DXT-300) with removable purpose-built collimators. Optimisation studies have concentrated upon the operating voltage, polariser material and additional filtering. The optimum voltage was found to lie within the range 200-300 kV for all polarising materials. There was no significant difference using copper, aluminium or iron as the polariser. Increasing the additional filtering improved the MDL for a preset number of counts, but decreased the count-rate significantly, resulting in unacceptably long counting times. An MDL of 9 ppm was achieved for a phantom depth of 2 cm, using a copper polariser, 0.25 mm of tin filtering and an operating voltage of 220 kV. TLD measurements showed that the corresponding skin dose was 6 mGy. These results indicate a factor of improvement in the MDL from the previous 99mTc system, for a factor of two lower skin dose. The detection limit achieved is the lowest reported to date, and is considered adequate for a comprehensive patient study. It is anticipated that this will yield better information and the pharmacokinetics of platinum compounds and will lead to optimisation of both chemo and radiotherapy treatment. Additionally this technique can be easily integrated into any radiotherapy based department.     

Total body chlorine: calibration of the in vivo neutron activation measurement

Total body chlorine (TBCI), used to estimate the extracellular space, is measured by delayed-gamma neutron activation (DGNA) using the reaction 37Cl(n, gamma)38Cl, at Brookhaven National Laboratory. During the calibration process, we noticed that different values were obtained when different amounts of Cl were placed in the phantom. This non-linear relationship is due to the thermal neutron flux suppression by the thermal neutron capture reaction 35Cl(n, gamma)36Cl. Monte Carlo simulations confirm the results of phantom measurements showing an inverse relationship between the Cl content in the phantom and the gamma-ray yield per gram Cl. Thus, it is important to calibrate the DGNA system for TBCl using phantom standards containing an amount of Cl close to that expected in the individual undergoing measurement.     

Renal blood flow: measurement in vivo with rapid spiral MR imaging

PURPOSE: To evaluate the use of stent-grafts for the percutaneous closure of arteriovenous fistulas that develop after cardiac catheterization. MATERIALS AND METHODS: From January 1994 to November 1997, 14 arteriovenous fistulas in 13 patients (eight men, five women; age range, 46-65 years; mean age, 53.5 years) were treated. Eleven fistulas were situated between the deep femoral artery and the common femoral vein, and three fistulas were between the superficial femoral artery and the common femoral vein. All fistulas were closed with stent-grafts positioned in the artery at the level of the fistula. RESULTS: The percutaneous treatment of arteriovenous fistulas was successful in all cases. The findings at angiography performed after the procedure demonstrated the closure of the fistulas and the correct positioning of the prostheses; veins were no longer visible. One complication occurred--a partial thrombosis of the common femoral vein at the puncture site after manual compression. CONCLUSION: On the basis of the preliminary data, the authors believe that the percutaneous closure of arteriovenous fistulas with stent-grafts is a safe and effective alternative to conventional surgery.     

Computer simulation of the dynamics of a human arm and orthosis linkage mechanism

BACKGROUND: A prospective study was conducted to evaluate the clinical usefulness of three-dimensional (3D) surface-shaded maps for routine practice of myocardial perfusion single-photon emission computed tomography (SPECT) by comparison with 2D slices and 2D bull's-eye qualitative analysis. METHODS AND RESULTS: Angiograms were performed on 201 consecutive patients, 155 with coronary artery disease (CAD) and 46 with no significant CAD. One-day 201TI stress/rest-reinjection protocol was performed in 110 patients, and 1-day 99mTc-sestamibi or tetrofosmin stress/rest protocol was performed in 91. The stress protocol was either exercise or dipyridamole (0.56 mg/kg) infusion. Three-dimensional surface maps were obtained by using a threshold for the transaxial data at 50%, 55%, 60%, 65%, and 70% of the maximum pixel value in the first 60 patients. Interpretation of 3D maps was based on the presence of a complete (transmural-looking) perfusion hole within the myocardial wall; doubtful patterns were considered pathologic or normal. Good diagnostic values were found for the 50% to 60% thresholds, but the 60% setting showed the best concordance with multislice and bull's-eye analysis; higher values drastically degraded the specificity. Considering doubtful patterns as normal clarified interpretation and led to a small loss in sensitivity but high gain in specificity. Applied to the whole population, the 3D maps using a 60% threshold provided similar diagnostic value to detect CAD as did conventional and bull's-eye analysis. Moreover, the 3D maps showed a trend toward higher specificity and a proportionally smaller decrease in sensitivity (sensitivity: 92.9%, 90.3%, 89.7%; specificity: 45.6%, 50.0%, 58.7% for tomograms, bull's-eye analysis, and 3D maps, respectively), especially for the detection of left anterior descending and right CAD. Multivessel disease was detected in an identical manner. Three-dimensional maps might improve detection of perfusion defects in the basal regions. However, 3D maps were found to be less sensitive than slices and particularly bull's-eye analysis for the reversibility of stress defects. CONCLUSIONS: Three-dimensional surface display of myocardial perfusion is a valuable independent tool for determining presence, extent, and location of CAD. It can convey useful first-look information to the referring physician, especially through a cine-rotational motion (as done in our practice through use of a floppy disk.