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Early fitting of the below knee amputee.

A comparison was made of the rehabilitation of patients undergoing below knee amputation during the calendar year 1982 on the orthopedic, general, and vascular surgical services at Parkland Hospital. Eight of nine trauma patients on the orthopedic service were fit with a temporary prosthesis and subsequently were fitted with a definitive prosthesis. Of the remaining 53 patients, only three were fitted with a temporary prosthesis and eventually 13 were fit with a definitive prosthesis. This experience identified a need for an alternative fitting method, which resulted in the design of a temporary, adjustable below knee prosthesis intended to be useful for a significant portion of the below knee population. Thus early ambulation is encouraged, possibly resulting in a higher percentage of successful ambulators. Gratifying early results with eight patients are described.

Amputation, Surgical↗

Early post-surgical prosthetic fitting with a pre-fabricated plastic limb.

Early prosthetic fitting and independent ambulation are major goals in the rehabilitation of amputees with early walking being extremely valuable in the physical and psychosocial rehabilitation of the amputee. With early resumption of weight bearing and ambulation, deterioration of postural reflexes can be prevented and the residual limb (stump) can be shaped for definitive prosthetic fitting. A new temporary prosthesis was evaluated in its use on new below-knee amputees. The prosthesis is a plastic, hollow form which fits over the conventional rigid, plaster postoperative dressing. It comes in one size and is cut to fit the patient. The prosthesis is readily available, needs little training for its application, can be re-used, and is inexpensive. Twenty-two consecutive patients treated at Hines Veteran's Administration Hospital and Loyola University Medical Center underwent below-knee amputations. All were determined to be potential walkers. The average age at surgery was 61 years with a range of 17 to 74 years. Amputation was performed for trauma in two patients and gangrene in the other 20. All wounds were dressed with conventional rigid, plaster dressings with cast changes five days postoperatively. The prefabricated temporary prosthesis was applied at the second cast application at an average of 8.1 days postoperatively with permanent prosthetic fitting at 7.7 weeks. There were no complications related to the use of the plastic temporary prosthesis. The use of a new plastic temporary prosthesis has been found to be advantageous in the early rehabilitation of below-knee amputees.

Adolescent↗

Cardiorespiratory fitness and the progression of carotid atherosclerosis in middle-aged men.

BACKGROUND: Good cardiorespiratory fitness has been associated with reduced risk for clinical events of atherosclerotic vascular diseases, but whether it is related to slower progression of early atherosclerosis is unclear. OBJECTIVE: To study the association between cardiorespiratory fitness and the progression of early carotid atherosclerosis. DESIGN: 4-year follow-up study. SETTING: Eastem Finland. PARTICIPANTS: Population-based sample of 854 men 42 to 60 years of age. MEASUREMENTS: Maximal oxygen uptake (VO2max [mL/kg per minute]) was measured directly by using respiratory gas exchange in a cycle ergometer exercise test. Carotid atherosclerosis was assessed by using B-mode ultrasonography. RESULTS: After adjustments for age, technical covariates, and cigarette smoking, VO2max had strong, inverse, and graded associations with 4-year increases in maximal intima-media thickness (IMT) (standardized regression coefficient beta = -0.120; P = 0.002), plaque height (beta = -0.140; P < 0.001), surface roughness (beta = -0.147; P < 0.001), and mean IMT (beta = -0.080; P = 0.035). These associations weakened but remained statistically significant after additional adjustment for systolic blood pressure, serum levels of apolipoprotein B, diabetes, and plasma fibrinogen levels. The increases in maximal IMT, surface roughness, and mean IMT (23%, 31%, and 100%, respectively) were larger among men in the lowest quartile of VO2max (<26.1 mL/kg per minute) than among those in the highest quartile (>36.2 mL/kg per minute). CONCLUSIONS: Good cardiorespiratory fitness is associated with slower progression of early atherosclerosis in middle-aged men. These findings are important because they emphasize that middle-aged men can be evaluated for cardiorespiratory fitness to estimate their future risk for atherosclerotic vascular diseases. Additional research is warranted to investigate a possible causal relationship between cardiorespiratory fitness and atherosclerosis.

Adult↗

ABPM-FIT and CV-SORT: an easy-to-use software package for detailed analysis of data from ambulatory blood pressure monitoring.

We describe a non-profit software package for the computerized analysis of ambulatory blood pressure monitoring (ABPM) recordings, in order to make it available to researchers in cardiovascular physiology, pharmacology and medicine. The first program, ABPM-FIT, can load data from several ABPM devices directly as they are stored on disk, making complicated data conversion steps unnecessary. The program performs conventional linear analyses of ABPM data automatically by calculation of mean, SD, load (the percentage of data above a chosen limit), and highest and lowest readings in user-defisned day and night periods. In addition, the area under the parameter-time curve (AUC) and the weighted mean (AUC/time) is calculated for all parameters monitored. In a second step, ABPM-FIT performs a rhythm analysis by fitting partial Fourier series to the data. Only those hormonics are included which significantly reduce the residual variance of the fit. The parameters of these functions (mesor, amplitudes, acrophases), values derived from the composed curves (maximum and minimum, AUC) and their slopes (e.g. maximal increase and decrease) are calculated automatically and, if desired, saved on disk. The second program, CV-SORT, loads groups of result files saved by ABPM-FIT, allows the extraction of parameters of interest for further analyses and creates spreadsheets containing the selected values from groups of patients. In addition, CV-SORT performs simple statistics, and calculates group mean circadian blood pressure and heart rate profiles from individual Fourier curves, with SD, confidence intervals or percentiles. The features of both programs are shown in exemplary analyses of ABPM recordings.

Journal Article↗

Marginal fit of nickel-chromium copings before and after internal adjustments with duplicated stone dies and disclosing agent.

STATEMENT OF PROBLEM: Despite careful procedures, master stone dies may be damaged during laboratory procedures. The dentist routinely adjusts castings because the marginal fit of casting is not as accurate as on the dies. PURPOSE: This study evaluated the technique of internal adjustment of castings with use of duplicated stone dies and a disclosing agent to improve marginal fit discrepancy. MATERIAL AND METHODS: Thirty-two nickel-chromium copings were fabricated and simulated standard clinical and laboratory procedures with 2 variables: tooth preparation convergence angles of 6 and 18 degrees, with or without internal relief. Master stone dies and their duplicates were selected for coping construction and internal adjustment, respectively. A specimen positioning device was coupled with a Toolmakers microscope to allow reproducibility of measurements. Each coping was evaluated at 8 locations of its marginal perimeter, before and after internal adjustment. RESULTS: Marginal fit discrepancy of copings were significantly reduced with an internal adjustment technique (mean > 52%) for all experimental groups. Tooth preparations with greater convergence and internally relieved castings recorded a better marginal fit. CONCLUSION: The casting internal adjustment technique with use of duplicated stone dies and a disclosing agent substantially reduced marginal fit discrepancy.

Analysis of Variance↗

A method aimed at achieving passive fit in implant prostheses: case report.

PURPOSE: The aim of this article is to describe a technique that attempts to solve titanium-related problems while affording passive fit. MATERIALS AND METHODS: The method basically involves the manufacture of a cast titanium framework fitted onto titanium machined abutments. After verifying the passive fit of the framework presoldered to the abutments, Nd-YAG laser welding is completed in the laboratory. RESULTS: The aim of the technique is to secure the following clinical benefits: (1) use of titanium, as it is the best-suited material; (2) use of high-precision machined abutments; (3) laser welding and its advantages; and (4) achievement of passive fit. CONCLUSION: The technique described is adequate to achieve passive fit in implant prostheses using titanium and laser welding.

Acrylic Resins↗

Selecting the best-fit model of nucleotide substitution.

Despite the relevant role of models of nucleotide substitution in phylogenetics, choosing among different models remains a problem. Several statistical methods for selecting the model that best fits the data at hand have been proposed, but their absolute and relative performance has not yet been characterized. In this study, we compare under various conditions the performance of different hierarchical and dynamic likelihood ratio tests, and of Akaike and Bayesian information methods, for selecting best-fit models of nucleotide substitution. We specifically examine the role of the topology used to estimate the likelihood of the different models and the importance of the order in which hypotheses are tested. We do this by simulating DNA sequences under a known model of nucleotide substitution and recording how often this true model is recovered by the different methods. Our results suggest that model selection is reasonably accurate and indicate that some likelihood ratio test methods perform overall better than the Akaike or Bayesian information criteria. The tree used to estimate the likelihood scores does not influence model selection unless it is a randomly chosen tree. The order in which hypotheses are tested, and the complexity of the initial model in the sequence of tests, influence model selection in some cases. Model fitting in phylogenetics has been suggested for many years, yet many authors still arbitrarily choose their models, often using the default models implemented in standard computer programs for phylogenetic estimation. We show here that a best-fit model can be readily identified. Consequently, given the relevance of models, model fitting should be routine in any phylogenetic analysis that uses models of evolution.

Algorithms↗

Aerobic fitness effects in fibromyalgia.

OBJECTIVE: To compare 2 exercise modalities, aerobic fitness training and stretching exercises, in patients with fibromyalgia (FM) in relation to function, pain, quality of life, depression, and anxiety, and to correlate the cardiorespiratory fitness gain with symptom improvement. METHODS: Seventy-six women with FM between 18 and 60 years old were randomized to either an aerobic program or stretching program, for 20 weeks. They were evaluated at the beginning of the program and after 10 and 20 weeks in relation to the improvement of aerobic fitness, flexibility, function, Fibromyalgia Impact Questionnaire (FIQ), Short-form Health Survey (SF-36), and depression and anxiety levels. Ventilatory anaerobic threshold (VT) and maximum oxygen uptake (VO2max) were determined by expired gas analyses. RESULTS: Aerobic exercise was superior to stretching in relation to VO2 max, VT, function, depression, pain, and the emotional aspects and mental health domains of SF-36. Patients in the stretching group showed no improvement in depression, "role emotional," and "mental health." No association was noted between improvement in aerobic fitness as measured by VT and the improvement of pain, function, or scores in FIQ and SF-36. CONCLUSION: Our results confirm that aerobic exercise is beneficial to patients with FM, but the cardiorespiratory fitness gain is not related to improvement of FM symptoms.

Adolescent↗

Rasch fit statistics as a test of the invariance of item parameter estimates.

The invariance of the estimated parameters across variation in the incidental parameters of a sample is one of the most important properties of Rasch measurement models. This is the property that allows the equating of test forms and the use of computer adaptive testing. It necessarily follows that in Rasch models if the data fit the model, than the estimation of the parameter of interest must be invariant across sub-samples of the items or persons. This study investigates the degree to which the INFIT and OUTFIT item fit statistics in WINSTEPS detect violations of the invariance property of Rasch measurement models. The test in this study is a 80 item multiple-choice test used to assess mathematics competency. The WINSTEPS analysis of the dichotomous results, based on a sample of 2000 from a very large number of students who took the exam, indicated that only 7 of the 80 items misfit using the 1.3 mean square criteria advocated by Linacre and Wright. Subsequent calibration of separate samples of 1,000 students from the upper and lower third of the person raw score distribution, followed by a t-test comparison of the item calibrations, indicated that the item difficulties for 60 of the 80 items were more than 2 standard errors apart. The separate calibration t-values ranged from +21.00 to -7.00 with the t-test value of 41 of the 80 comparisons either larger than +5 or smaller than -5. Clearly these data do not exhibit the invariance of the item parameters expected if the data fit the model. Yet the INFIT and OUTFIT mean squares are completely insensitive to the lack of invariance in the item parameters. If the OUTFIT ZSTD from WINSTEPS was used with a critical value of | t | > 2.0, then 56 of the 60 items identified by the separate calibration t-test would be identified as misfitting. A fourth measure of misfit, the between ability-group item fit statistic identified 69 items as misfitting when a critical value of t > 2.0 was used. Clearly relying solely on the INFIT and OUTFIT mean squares in WINSETPS to assess the fit of the data to the model would cause one to miss one of the most important threats to the usefulness of the measurement model.

Calibration↗

[The effect of tooth preparation design on the CAD/CAM all-ceramic coping crown's fitness].

OBJECTIVE: To study the effect of tooth preparation design on fitness of CAD/CAM all-ceramic coping crown. METHODS: The tooth preparation comprised 2 types of occlusal convergence (10 degrees, 20 degrees), 2 margin forms (shoulder, chamfer). The MC coping were milled by Cerec 2 CAD/CAM system, cemented, embedded, sectioned, and measured at 10 sites to obtain the data of margin, shoulder, axial surface, occlusal surface fitness. RESULTS: The coping's fitness was influenced by convergence angle and margin form. The coping's fitness was very nice (101.7 approximately 127.9) microm when the coping with 20 degrees occlusal convergence angle. Those coping with 20 degrees occlusal convergence and chamfer margin in tooth preparation provided the best fitness, its cement film thickness in margin was (40.1 +/- 11.8) microm. CONCLUSIONS: The 20 degrees occlusal convergence and chamfer margin can be used for CAD/CAM all-ceramic crown in clinical application.

Computer-Aided Design↗

Consequences of an interference fit on the fixation of porous-coated tibial components in total knee replacement.

A linearly elastic, axisymmetrical finite-element model was developed in an attempt to explain observed long-term patterns of growth of bone into tibial components. This model, which represents a portion of the tibial tray, one peg, and the surrounding cancellous bone, was used to examine two conditions of fixation in the immediate postoperative period. The first was characterized by the use of an interference fit for initial fixation of the component and the second, by the use of an interference fit with the hole in the bone deeper than the length of the peg. Two conditions of long-term fixation were also examined. In one, the bone was assumed to have grown into all of the porous coating. In the other, the bone was assumed to have grown only into the peg, and a layer of fibrous tissue was assumed to have developed between the tray and the bone. An interference fit between the peg and the cancellous bone produced considerable residual radial stresses in the bone. These stresses provide conditions that are favorable for ingrowth of bone into the pegs because the bone at the interface is stressed, and these stresses inhibit relative motion at the bone-peg interface. However, the interference fit of the peg relieved the stresses in the cancellous bone under the tray of the implant. Lack of stress at this interface is consistent with relative motion and subsequent formation of a layer of fibrous tissue. Deepening of the hole for the peg in the cancellous bone did not diminish the effects of the interference fit. Stresses in the bone under the metal tray were relieved when a layer of fibrous tissue under the tibial tray was represented in the model.

Biomechanical Phenomena↗

Viral phenotype and fitness.

The fitness is a parameter defining the replicative adaptation of an organism to its environment. Recently, the HIV research field has shown renewed interest in the replicative capacity of human immunodeficiency virus type 1 (HIV-1) due to the potential impact of ex vivo viral fitness on population size, drug resistance, and disease progression. In the absence of antiretroviral therapy, strains containing drug-resistance mutations have a reduced fitness compared to the wild-type (wt) quasispecies within the population. Therefore, selective pressure of drug therapy leads to dramatic shifts in the quasispecies distribution and fitness of those mutants with decreased sensitivity to the respective antiretrovirals. Even if the presence of drug resistance mutations can decrease the viral fitness and explain a sustained CD4+T cell count in presence of high viral load, the current treatment guidelines advocate a switch in antiretroviral treatment regimens following the emergence of primary drug resistant mutations and possibly prior to selection of compensatory changes.

Adaptation, Biological↗

Localization of interictal spikes using SAM(g2) and dipole fit.

SAM(g2) is an automated analysis that transforms the MEG data into a functional image of spike-like activity, giving the source waveforms for those locations. Since the source waveforms estimated by SAM have higher signal-to-noise ratio (SNR) than does the raw MEG data, it is possible to automatically mark the location and timing of each spike for comparisons with dipole fit procedures. Both SAM(g2) and equivalent current dipole (ECD) fits were used to analyze MEG interictal spike recordings in 10 patients with cortical dysplasias and medial temporal lobe epilepsy. The ECD fit locations obtained by manual spike classification and latency marking were compared with those found by automated SAM(g2) procedures. When the SNR of interictal activity was high (compared to the background) with a clear single focus, there was excellent agreement between the ECD cluster location and the SAM(g2) maximum. However, when the SNR of spikes was low, manual single ECD location scatter was larger than SAM(g2) reconstructions. When multiple independent interictal spike loci were present, there was some disagreement between SAM(g2) and ECD scatter in the cases of low SNR spikes. When SAM(g2) indicated multiple coupled spike loci, the residual variance for the dipole fit was high and its scatter unacceptably large--even for multiple dipole models. This study demonstrates that SAM(g2) is equivalent to ECD fit for localizing interictal spikes when there is a single locus and good SNR. Further studies are required to validate cases in which there are multiple spike loci or poor SNR.

Action Potentials↗

Rapid evolutionary escape by large populations from local fitness peaks is likely in nature.

Fitness interactions between loci in the genome, or epistasis, can result in mutations that are individually deleterious but jointly beneficial. Such epistasis gives rise to multiple peaks on the genotypic fitness landscape. The problem of evolutionary escape from such local peaks has been a central problem of evolutionary genetics for at least 75 years. Much attention has focused on models of small populations, in which the sequential fixation of valley genotypes carrying individually deleterious mutations operates most quickly owing to genetic drift. However, valley genotypes can also be subject to mutation while transiently segregating, giving rise to copies of the high fitness escape genotype carrying the jointly beneficial mutations. In the absence of genetic recombination, these mutations may then fix simultaneously. The time for this process declines sharply with increasing population size, and it eventually comes to dominate evolutionary behavior. Here we develop an analytic expression for N(crit), the critical population size that defines the boundary between these regimes, which shows that both are likely to operate in nature. Frequent recombination may disrupt high-fitness escape genotypes produced in populations larger than N(crit) before they reach fixation, defining a third regime whose rate again slows with increasing population size. We develop a novel expression for this critical recombination rate, which shows that in large populations the simultaneous fixation of mutations that are beneficial only jointly is unlikely to be disrupted by genetic recombination if their map distance is on the order of the size of single genes. Thus, counterintuitively, mass selection alone offers a biologically realistic resolution to the problem of evolutionary escape from local fitness peaks in natural populations.

Biological Evolution↗

Character displacement as the "best of a bad situation": fitness trade-offs resulting from selection to minimize resource and mate competition.

Character displacement has long been considered a major cause of adaptive diversification. When species compete for resources or mates, character displacement minimizes competition by promoting divergence in phenotypes associated with resource use (ecological character displacement) or mate attraction (reproductive character displacement). In this study, we investigated whether character displacement can also have pleiotropic effects that lead to fitness trade-offs between the benefits of avoiding competition and costs accrued in other fitness components. We show that both reproductive and ecological character displacement have caused spadefoot toads to evolve smaller body size in the presence of a heterospecific competitor. Although this shift in size likely arose as a by-product of character displacement acting to promote divergence between species in mating behavior and larval development, it concomitantly reduces offspring survival, female fecundity, and sexual selection on males. Thus, character displacement may represent the "best of a bad situation" in that it lessens competition, but at a cost. Individuals in sympatry with the displaced phenotype will have higher fitness than those without the displaced trait because they experience reduced competition, but they may have reduced fitness relative to individuals in allopatry. Such a fitness trade-off can limit the conditions under which character displacement evolves and may even increase the risk of "Darwinian extinction" in sympatric populations. Consequently, character displacement may not always promote diversification in the manner that is often expected.

Animals↗

Intraspecific hybridization and the recovery of fitness in the native legume Chamaecrista fasciculata.

Genetic incompatibilities and low offspring fitness are characteristic outcomes of hybridization between species. Yet, the creative potential of recombination following hybridization continues to be debated. Here we quantify the outcome of hybridization and recombination between adaptively divergent populations of the North American legume Chamaecrista fasciculata in a large-scale field experiment. Previously, hybrids between these populations demonstrated hybrid breakdown, suggesting the expression of adaptive epistatic interactions underlying population genetic differentiation. However, the outcome of hybridization ultimately rests on the performance of even later generation recombinants. In experiments that compared the performance of recombinant F6 and F2 generations with nonrecombinant F1 and parental genotypes, we observed that increasing recombination had contrasting effects on different life-history components. Lifetime fitness, defined as the product of survivorship and reproduction, showed a strong recovery of fitness in the F6. The overall gain in fitness with increased recombination suggests that hybridization and recombination may provide the necessary genetic variation for adaptive evolution within species. We discuss the mechanisms that may account for the gain in fitness with recombination, and explore the implications for hybrid speciation and phenotypic evolution.

Biological Evolution↗

Cementless press-fit cup. Principles, experimental data, and three-year follow-up study.

The concept of the press-fit cup includes an operative defect as small as possible, achievement of intrinsic stability by press-fit, and surface coating by an orderly, oriented wire mesh coating. The design is a modified hemisphere with flattening in the pole area and oversized cup diameter. A first series of press-fit cups were fitted with titanium nitride-coated stainless steel mesh. The manufacturing of such chemically pure titanium has only recently become feasible. Animal experiments using mountain sheep have shown an increase in the stability of the press-fit cup within the acetabulum with time and progressive bony ingrowth; this was verified in cups retrieved at autopsy. Three hundred eighty-seven first-generation titanium nitride-coated stainless steel mesh implants have been reviewed with a follow-up time of 12 to 39 months (average, 16.6 months). There were no intraoperative complications related to the cup. The roentgenographic follow-up study of 330 (85.1%) hips showed only a single case with a radiolucent line in all zones (1-3) as a roentgenographic sign of loosening, i.e., fibrous ingrowth. Two cups had to be revised due to insufficient primary stability and tilting.

Acetabulum↗

Psychiatric conditions in worker fitness and risk evaluation.

This chapter has reviewed the specific techniques of measuring fitness for work in individuals with psychiatric impairment. The discussion also considered the estimate of risk associated with various specific conditions and diagnoses. The use of psychiatric measures in work-fitness estimation is warranted in the following situations: 1. applicants with known or suspect history of psychiatric disorder; 2. employees returning to work after an episode of emotional illness or substance abuse; 3. employees referred to the medical department by management for evaluation of performance decrement, absence, abrupt indebtedness, unusual behavior, etc.; and 4. individuals evaluated for high stress or high risk jobs. Applicants' evaluations begin with a thorough medical history, a physical examination, a mental status examination, and basic laboratory studies. The personal history must include a complete work history, with particular attention paid to job duration and reasons for leaving employment. The mental status may be extended by specialized scales, e.g., the Griffiths work behavior rating scale. Unless an applicant has evidence of cognitive dysfunction, the usual battery of psychometric tests will not be helpful. Instruments that measure self-concept and ego strength, e.g., the Stotsky-Weinberg Sentence Completion Test and Miskimins Self-Goal-Other Test, may assist in resolving difficult questions about work fitness, especially in people with a history of schizophrenia. When an employee returns to work after an episode of psychiatric illness, the major questions for the occupational physician are: Is this person capable of returning to his current job? If not, what type of work is he capable of performing? In this instance, the fitness evaluation must add management data about the job to medical data about the patient. The patient-job fit is the crucial issue. For example, a socially-isolated, withdrawn paranoid schizophrenic functioned adequately for years as a third-shift computer operator. The scale of his operational responsibilities allowed him to work alone most of the time, a work environment unsatisfactory to most people but quite suitable for him. To aid in maintaining patient compliance with the treating physician's regimen, the patient should be asked to authorize release of medical information about the illness and to allow continued contact between the occupational physician and the treating doctor. Regularly scheduled follow-up visits are very helpful in maintaining patients on the job. They should include a brief interval history, an abbreviated mental status, relevant laboratory data (e.g., urine chromatography), and support.(ABSTRACT TRUNCATED AT 400 WORDS)

Humans↗