Mechanical effect of posterior wire or half-pin configuration on stabilization utilizing a model of circular external fixation of the foot

BACKGROUND: Numerous studies have addressed biomechanical characteristics of circular external fixation of long bones. The objective of the present study was to evaluate stabilization of a simulated foot model using external fixation with either calcaneal tensioned stopper wires or half-pins. METHODS: Fixation configurations of the calcaneus included two parallel wires, two wires crossing at either 30 degrees or 45 degrees, a 4-mm- and 5-mm-diameter single half-pin, or two half-pins inserted at a cross-angle of either 45 degrees or 90 degrees. All frames were tested in axial compression, anteroposterior (AP) bending, and mediolateral (ML) bending. RESULTS: An increase in wire cross-angle improved the axial and AP bending stabilization but had no influence on ML bending. Utilization of a single calcaneal half-pin instead of two cross-wires resulted in a considerable reduction in ML bending stabilization. Frame configurations with two half-pins substantially improved axial and ML bending stabilization. Due to the medial location of the metatarsal wire stopper, an increase in half-pin cross-angle significantly improved ML bending stiffness under lateral foot loading. Under the medial foot loading, however, the half-pin cross-angle had no effect on ML bending stabilization. Replacement of cross-wires with two half-pins significantly improved the AP bending stiffness only when the half-pin cross-angle was reduced to 45 degrees. In all modes of two half-pin frame loading, the half-pin diameter had a substantial effect on foot stabilization. CONCLUSIONS: Although the wire cross-angle, half-pin cross-angle, and half-pin diameter affect the stability of foot circular external fixation, the influence of these mechanical parameters on foot stabilization is dependent on the mode and location of loading. CLINICAL RELEVANCE: The results of the present mechanical testing can be utilized as a useful guideline for the optimization of circular external fixation of the foot.     

The diagnostic accuracy of computed tomography in pediatric chronic rhinosinusitis

OBJECTIVE: To determine the accuracy of computed tomography (CT) in the diagnosis of pediatric chronic rhinosinusitis (CRS). SETTING: Multi-institutional prospective dual cohort study. METHODS: Two cohorts of children undergoing CT of the paranasal sinuses were prospectively evaluated. The first cohort consisted of children undergoing CT in preparation for endoscopic sinus surgery (diseased group). The second cohort consisted of children undergoing CT for nonsinusitis reasons (nondiseased control group). Sinus CT scans were scored according to the Lund-MacKay system. Diagnostic accuracy was quantified with the receiver operating characteristic curve. Sensitivity, specificity, and predictive value analyses were conducted. RESULTS: A total of 66 pediatric patients (mean age, 8 years) were studied in the diseased group and exhibited a mean Lund score of 10.4 (95% confidence interval, 9.2-11.5); 192 control patients (mean age, 9 years) exhibited a mean Lund score of 2.8 (95% confidence interval, 2.4-3.2). The area under the curve for the receiver operating characteristic was 0.923 (P<.001), indicating excellent diagnostic accuracy. Adopting a Lund score cutoff of 5 to represent true disease, the CT scan demonstrated a sensitivity and specificity of 86% and 85%, respectively. Lund scores of 2 or less have an excellent negative predictive value, whereas Lund scores of 5 or greater have an excellent positive predictive value (ie, strongly indicate true disease). CONCLUSIONS: The sinus CT scan demonstrates excellent diagnostic accuracy for the diagnosis of pediatric CRS, with excellent sensitivity and specificity. However, its predictive value depends substantially on the base rate prevalence of CRS in the population being evaluated.     

Health effects associated with recreational coastal water use: urban versus rural California

We compared rates of reported health symptoms among surfers in urban North Orange County (NOC) and rural Santa Cruz County (SCC), California, during 2 winters (1998 and 1999) to determine whether symptoms were associated with exposure to urban runoff. NOC participants reported almost twice as many symptoms as SCC participants during the 1998 winter. In both study years, risk increased across symptom categories by an average of 10% for each 2.5 hours of weekly water exposure. Our findings suggest that discharging untreated urban runoff onto public beaches can pose health risks.     

Retinal bipolar cells: contrast encoding for sinusoidal modulation and steps of luminance contrast

Contrast encoding for sinusoidal modulations of luminance contrast was investigated by intracellular recording in the intact salamander retina. In what appears to be the first study of this kind for vertebrate bipolar cells, responses of the central receptive-field mechanism of cone-driven cells to modulation of 3 Hz were analyzed quantitatively via both signal averaging and a Fast Fourier Transform (FFT) while the retina was light adapted to 20 cd/m2. Depolarizing and hyperpolarizing bipolar cells showed very similar encoding. Both responded with sinusoidal waveforms whose amplitude varied linearly with modulation depths ranging up to 7-8%. The slope of the modulation/response curve was very steep in this range. Thus, the contrast gain was high, reaching values of 6-7, and the half-maximal response was achieved at modulations of 9% or less. At modulations above approximately 15%, the responses typically showed strong compressive nonlinearity and the waveform was increasingly distorted. At maximum modulation, the higher harmonics of the FFT constituted about 30% of the amplitude of the fundamental. Measurements were also made for cones and horizontal cells. Both cell types showed predominantly linear responses and low contrast gain, in marked contrast to bipolar cells. These results suggest that the high contrast gain and strong nonlinearity of bipolar cells largely arise postsynaptic to cone transmitter release. Further experiments were performed to compare responses to contrast steps versus those to sinusoidal modulation. In the linear range, we show that the contrast gains of cones and horizontal cells are low and virtually identical for both steps and sinusoidal modulations. In bipolar cells, on the other hand, the contrast gain is about two times greater for steps than that for the 3-Hz sine waves. These results suggest that mechanisms intrinsic to bipolar cells act like a high-pass filter with a short time constant to selectively emphasize contrast transients over slower changes in contrast.     

The partners in care approach to ethics outcomes in quality improvement programs for depression

OBJECTIVE: Patient centeredness and equity are major quality goals, but little is known about how these goals are affected by efforts to improve the quality of care. The authors describe an approach to addressing these goals in a randomized trial of quality improvement for depressed primary care patients. METHODS: For four ethics goals (autonomy, distributive justice, beneficence, and avoiding harm), the authors identify intervention features, study measures, and hypotheses implemented in Partners in Care, a randomized trial of two quality improvement interventions, relative to usual care and summarize published findings pertinent to these outcomes. RESULTS: To implement an ethics framework, modifications were required in study design and in measures and analysis plans, particularly to address the autonomy and justice goals. Extra resources were needed for sample recruitment, for intervention and survey materials, and to fund an ethics coinvestigator. The interventions were associated with improvements in all four ethics areas. Patients who received the interventions were significantly more likely to receive the treatment they had indicated at baseline as their preferred treatment (autonomy goal). Intervention-associated benefits occurred more rapidly among sicker patients and extended to patients from ethnic minority groups, resulting in a reduction in ethnic-group disparities in health outcomes relative to usual care (distributive justice goal). The interventions were associated with improved quality of care and health outcomes (beneficence goal) and with reduced use of long-term minor tranquilizers (goal of avoiding harm). CONCLUSION:S: It is feasible to explicitly address ethics outcomes in quality improvement programs for depression, but substantial marginal resources may be required. Nevertheless, interventions so modified can increase a practice's ability to realize ethics goals.     

Elevated neuron number in the limbic thalamus in major depression

OBJECTIVE: The mediodorsal and anteroventral/anteromedial nuclei of the thalamus are brain regions of interest in the study of mood disorders because they connect subcortical limbic system structures such as the amygdala with the prefrontal, cingulate, and temporal cortices. Anatomical abnormalities have been observed both in the amygdala and in the aforementioned cortical regions in affective disorder patients. Neuroanatomical studies of the thalamus have rarely been conducted in patients with mood disorders. METHOD: Postmortem tissue from the Stanley Foundation Brain Bank was obtained from subjects diagnosed with major depressive disorder, bipolar disorder, and schizophrenia as well as a nonpsychiatric comparison group (N=10-13 per group). The optical disector stereological procedure was used to count neurons in the mediodorsal and anteroventral/anteromedial nuclei of the thalamus in each brain. RESULTS: There were significantly more neurons in the mediodorsal (37%) and anteroventral/anteromedial (26%) nuclei in subjects with major depressive disorder relative to the nonpsychiatric comparison subjects. Neuron numbers and volumes in these limbic thalamic nuclei were normal in the schizophrenia and bipolar subjects. CONCLUSIONS: The data indicate that there is an elevation in total neuron number in the limbic thalamus that is specific for major depressive disorder. This represents the first report of a neuropsychiatric disorder being associated with an increase in total regional neuron number. The present findings, along with recent data, indicate that significant anatomical and functional abnormalities are present in limbic circuits in major depressive disorder.