A laboratory batch reactor test for assessing nonspeciated volatile organic compound biodegradation in activated sludge.

The relative rates of biodegradation and stripping and volatilization of nonspeciated volatile organic compounds (VOCs) in wastewater treated with aerobic activated-sludge processes can be quantified using a newly developed procedure. This method was adapted from the original aerated draft tube reactor test that was developed to measure biodegradation rate constants for specific volatile pollutants of interest. The original batch test has been modified to include solid-phase microextraction (SPME) fibers for sampling in the gas phase. The experimental procedure using SPME fibers does not require specific identification and quantitation of individual pollutants and can be used to evaluate wastewater with multiple VOCs. To illustrate use of this procedure, laboratory experiments were conducted using biomass and wastewater or effluent from three activated-sludge treatment systems. Each experiment consisted of two trials: a stripping-only trial without biomass and a stripping plus biodegradation trial using biomass from the activated-sludge unit of interest. Data from the two trials were used to quantify the rates of biodegradation by difference. The activated-sludge systems tested were a laboratory diffused-air reactor treating refinery wastewater, a full-scale surface aerated reactor treating a petrochemical wastewater, and a full-scale diffused-air reactor treating a variety of industrial effluents. The biodegradation rate constant data from each laboratory batch experiment were used in model calculations to quantify the fraction emitted (fe) and the fraction biodegraded (fbio) for each system. The fe values ranged from a maximum of 0.01 to a maximum of 0.32, whereas fbio values ranged from a minimum of 0.40 to a minimum 0.95. Two of these systems had been previously tested using a more complicated experimental approach, and the current results were in good agreement with previous results. These results indicate that biodegradation rate constant data from this laboratory method can be successfully used to predict the fate of VOCs in field-scale treatment units, and thus could potentially be used for demonstration of compliance with wastewater VOC emission regulations.

Clinical failure after posterior wall acetabular fractures: the influence of initial fracture patterns.

OBJECTIVE: To determine radiographic and clinical features that predict rapid failure after open reduction and internal fixation of posterior wall acetabular fractures. DESIGN: Retrospective radiographic review and patient follow-up study. SETTING: University hospital. PATIENTS: Forty-two patients with posterior wall acetabular fractures. INTERVENTION: Open reduction and internal fixation. MAIN OUTCOME MEASURES: Radiographs, Merle D'Aubigné scores, Musculoskeletal Functional Assessment. RESULTS: Eleven patients had complete loss of joint space by one year postinjury; eight of these individuals required reconstructive surgery. These patients more commonly had fractures with comminution of three fragments or more (p = 0.001) or fracture into the subchondral arc at the level of the acetabular roof (p = 0.045). CONCLUSION: Poor outcomes after open reduction and internal fixation are associated with certain types of posterior wall fracture patterns.

Nonoperative management of dens fracture nonunion in elderly patients without myelopathy.

STUDY DESIGN: A retrospective review of elderly patients treated without surgery for chronic mobile nonunions of the odontoid process. Patients were observed on an annual basis with clinical examinations and flexion/extensions plain film radiographs. OBJECTIVES: To evaluate the clinical and radiographic results of elderly patients without myelopathy treated without surgery for dens fracture nonunion. SUMMARY OF BACKGROUND DATA: Because of the risk of progressive myelopathy or sudden neurologic injury, many surgeons recommend operative stabilization for patients with mobile dens nonunions who are able to withstand an operation. There is, however, a lack of information about the radiographic and neurologic progression of dens nonunions. Although a less aggressive surgical approach has been recommended by some authors for elderly or medically compromised patients with acute fractures, long-term follow-up evaluation of patients with resulting nonunions has not been reported. METHODS: A series of elderly patients with chronic, unstable, dens nonunions without myelopathy were treated with a nonoperative treatment protocol. Patients were informed of the nature of their lesion, including the risk of acute or chronic spinal cord injury and the options for operative treatment. Patients were evaluated yearly for clinical and radiographic progression. No intervention to slow progression of atlantoaxial instability was undertaken. RESULTS: None of the patients developed myelopathic symptoms during the follow-up period, and no patient experienced more than a 1 mm radiographic increase in atlantoaxial excursion. None of the reported patients had less than 14 mm available for the spinal cord in either flexion or extension at the start of clinical monitoring. CONCLUSIONS: Although further follow-up evaluation is needed, the authors believe on the basis of this review that this treatment protocol may be considered for patients who are poor candidates for surgical fusion.

Stulberg classification system for evaluation of Legg-Calvé-Perthes disease: intra-rater and inter-rater reliability.

BACKGROUND: Researchers and clinicians commonly use the classification system of Stulberg et al. as a basis for treatment decisions during the active phase of Legg-Calvé-Perthes disease because of its putative utility as a predictor of long-term outcome. It is generally assumed that this system has an acceptable degree of reliability. This assumption, however, is not convincingly supported by the literature. METHODS: The purpose of the present study was to assess the inter-rater and intra-rater reliability of the classification system of Stulberg et al. with use of a pre-test, post-test design. During the pre-test phase, nine raters independently used the system to evaluate the radiographs of skeletally mature patients who had been managed for Legg-Calvé-Perthes disease. The intervention between the pre-test and post-test phases consisted of a consensus-building session during which all raters jointly arrived at standardized definitions of the various joint structures that are assessed with use of the classification system. The effect of these definitions on reliability then was assessed by reevaluating the radiographs during the post-test phase. RESULTS: The pre-test intra-rater reliability coefficients ranged from 0.709 to 0.915, and the post-test coefficients ranged from 0.568 to 0.874. The pre-test inter-rater reliability coefficients ranged from 0.603 to 0.732, and the post-test coefficients ranged from 0.648 to 0.744. Contributing to the variance was a lack of agreement concerning the assessment of joint structures and the way in which the raters translated these evaluations into a classification according to the system of Stulberg et al. CONCLUSIONS: Although intra-rater reliability was marginally acceptable, the degree of variability between the classifications assigned by different raters even after the intervention - calls into question the reliability of the system of Stulberg et al.; consequently, the validity of any treatment decisions, outcome evaluations, or epidemiological studies based on this system is also in question.

Adhesion mediated by bonds in series.

Cell adhesion in physiological situations and biotechnological applications is often mediated through serial protein/protein linkages. The adhesion strength of cell/substrate contacts through receptor/ligand bonds in series is explored with a simple mathematical model and quantified with an experimental adhesion assay. A deterministic, mass-action model is developed to describe the attachment and detachment of cell/substrate contacts through single and serial bonds. The experimental system is comprised of protein-coated beads, soluble antibody linkers, and an antibody-coated glass surface. Using the Radial-Flow Detachment Assay, the adhesion strengths of bead/substrate contacts through single and serial linkages are measured. Taken together, this work shows that the specific adhesion strength of the cell/substrate contacts comprised of two receptor/ligand bonds in series is less than the specific adhesion strength of the cell/substrate contacts comprised of either of the bonds separately. In addition, the force to rupture contacts comprised of bonds in series varies with the concentration of the solution linker. The model predicts that the locus of linkage fracture location has only a mild dependence on the ratio of relative bond affinities.

Use of knee braces in sport. Current recommendations.

This article provides a review of the progress that has been made on the biomechanical, functional performance and epidemiological investigations into the effectiveness of prophylactic knee braces (PKBs) since the position statement against their use was issued in 1987 by the American Academy of Orthopaedics and a review of this subject was last published in Sports Medicine in 1989 by Montgomery and Korziris. The evolution of the salient design features of three surrogate knee models are reviewed along with the results of PKB effectiveness and safety factor testing. While still too limited in scope to be totally realistic, major advances have been made in the sophistication of the present biomechanics laboratory testing conditions. The on-the-field functional performance effects of wearing a knee brace are not always manifest in all individuals. The efficacy of PKBs remains in question but recent studies have taught us enough to put their use into perspective. While they may play some role, PKBs probably represent the least important factor in influencing the likelihood that a medial collateral ligament (MCL) sprain will occur. On the other hand, there is no evidence that such braces put added valgus pressure on some knees, or that wearing a brace is associated with an increased frequency or severity of knee or ankle injury. All else being equal, from the biomechanical studies, we know that whilst some braces are better than others, currently available PKBs can provide 20 to 30% greater resistance to a lateral blow, with the possibility that the anterior cruciate ligament (ACL) is given even greater protection than the MCL. This appears to be true when the lateral blow is of sufficient magnitude to cause significant medial joint line opening, but is not as great at the very lowest levels of impact. Regardless of the material they are made of, the most effective PKBs are those sufficiently stiff to prevent an external blow at the joint line from causing brace hinge contact with the knee tissues. Based on the superior results of the custom-fit functional braces, the most important future design feature appears to be the sizing and fitting of the thigh and tibial cuffs. On the negative side, the presence of a brace may slow an athlete's straight-ahead sprint speed and cause early fatigue to its wearer. This effect appears to vary from one brace to another according to its weight, design features, and pressure from the leg and thigh straps. However, it appears that knee braces do have the potential to restrict performance of the athlete for high-speed running but the effect is related to several factors. The weight of the brace resultant friction of the hinges, completeness of fit, and tightness of straps appear to be important. The most measurable effects include: increased muscular relaxation pressures; increased energy expenditure; and a related increase in blood lactate levels, maximal torque output, oxygen consumption and heart rate. On the other hand, experienced brace wearers and larger, stronger individuals displayed fewer, or no effects of donning a brace. Improvements in the protectiveness of the PKB are likely to accompany improvements in the ability to contour the braces to fit each individual's leg in the equipment room without the added expense of the cast-moulding process. Further improvement may be realised by friction-free polycentric joints, as well as an attachment system that minimises thigh and calf soft tissue compression perhaps by incorporating the braces into the trousers of the uniform to provide suspension from the waist.

Acetabular fractures classification of Letournel and Judet--a systematic approach.

After a background understanding of the classification of Judet and Letournel and the radiographic anatomy of the pelvis, the majority of acetabular fractures are readily classified by utilizing the steps as outlined above. We feel that a systematic, stepwise approach to classifying acetabular fractures into larger groups and then subclassifying these groups will help simplify the application of the Letournel and Judet classification. Try using this method, and your ability to classify these fractures will improve.

Heterogeneity and probabilistic binding contributions to receptor-mediated cell detachment kinetics.

Biospecific cell adhesion is mediated by receptor-ligand bonds. Early theoretical work presented a deterministic analysis of receptor-mediated cell attachment and detachment for a homogeneous cell population. However, initial comparison of a deterministic framework to experimental detachment profiles of model "cells" (antibody-coated latex beads) did not show qualitative or quantitative agreement (Cozens-Roberts, C., D.A. Lauffenburger, and J.A. Quinn. 1990. Biophys. J. 58:857-872). Hence, we determine the contributions of population heterogeneity and probabilistic binding to the detachment behavior of this experimental system which was designed to minimize experimental and theoretical complications. This work also corrects an error in the numerical solution of the probabilistic model of receptor-mediated cell attachment and detachment developed previously (Cozens-Roberts, C., D.A. Lauffenburger, and J.A. Quinn. 1990. Biophys J. 58:841-856). Measurement of the population distribution of the number of receptors per bead has enabled us to explicitly consider the effect of receptor number heterogeneity within the cell-surface contact area. A deterministic framework that incorporates receptor number heterogeneity qualitatively and quantitatively accounts in large part for the model cell detachment data. Using measured and estimated parameter values for the model cell system, we estimate that about 90% of the observed kinetic detachment behavior originates from heterogeneity effects, while about 10% is due to probabilistic binding effects. In general, these relative contributions may differ for other systems.

Hospital foundation finds ups-and-downs has benefits.

Like any brand new venture, this hospital foundation found its first year development effort had successes and failures. The author describes how experience will provide a sure base of steady growth.