Utility of an image-based technique to detect changes in joint congruency following simulated joint injury and repair: an in vitro study of the elbow.

BACKGROUND: Investigating joint mechanics is important when determining the etiology of osteoarthritis, as degenerative changes are thought to occur due to altered joint mechanics. The objective of this study was to demonstrate the utility of an x-ray computed tomography-based approach to evaluate joint congruency in the setting of subtle kinematic alterations, employing an in vitro model of collateral ligament repair of the elbow. METHODS: Active and passive elbow flexion was performed in 4 and 5 fresh-frozen cadaveric upper extremities respectively using an elbow motion simulator in the valgus gravity dependent positions. The collateral ligaments were sectioned and repaired. A registration and inter-bone distance algorithm were then used to examine ulnohumeral joint congruency (quantified as surface area) throughout elbow flexion. Valgus angulation was also measured. FINDINGS: Following ligament sectioning and repair, there was a 1.2±1.0° increase in valgus angulation in active flexion and a 21.2±26.2% decrease in surface area. In passive flexion, valgus angulation increased 3.3±2.2° and surface area decreased 57.9±39.9%. INTERPRETATION: The technique described to quantify joint congruency proved to be sensitive enough to detect large changes in joint surface interactions inspite of only small changes in traditionally measured kinematics. These changes in joint congruency may, in part, explain the high incidence of arthritis that has been reported following ligament injuries of the elbow, even in the absence of clinically detectable instability. This technique, when adapted for in vivo use, will be a useful tool to evaluate joint function and the effectiveness of treatments non-invasively.

Lidar system model for use with path obscurants and experimental validation.

When lidar pulses travel through a short path that includes a relatively high concentration of aerosols, scattering phenomena can alter the power and temporal properties of the pulses significantly, causing undesirable effects in the received pulse. In many applications the design of the lidar transmitter and receiver must consider adverse environmental aerosol conditions to ensure the desired performance. We present an analytical model of lidar system operation when the optical path includes aerosols for use in support of instrument design, simulations, and system evaluation. The model considers an optical path terminated with a solid object, although it can also be applied, with minor modifications, to cases where the expected backscatter occurs from nonsolid objects. The optical path aerosols are characterized by their attenuation and backscatter coefficients derived by the Mie theory from the concentration and particle size distribution of the aerosol. Other inputs include the lidar system parameters and instrument response function, and the model output is the time-resolved received pulse. The model is demonstrated and experimentally validated with military fog oil smoke for short ranges (several meters). The results are obtained with a lidar system operating at a wavelength of 0.905 microm within and outside the aerosol. The model goodness of fit is evaluated using the statistical coefficient of determination whose value ranged from 0.88 to 0.99 in this study.

Effect of chronic beta-blockade on peri-operative outcome in patients undergoing non-cardiac surgery: an analysis of observational and case control studies.

Little is known about the effect of chronic beta-adrenoceptor antagonist therapy during the peri-operative period in patients undergoing non-cardiac surgery. We conducted a literature review to identify studies examining the relationship between chronic therapy and adverse peri-operative outcome. Eighteen studies were identified in which it was possible to ascertain the incidence of adverse cardiac outcomes in those patients who were and were not receiving chronic beta-blocker therapy. None of the studies demonstrated a protective effect of chronic beta-blockade. The results of these studies were then combined and a cumulative odds ratio calculated for the likelihood of myocardial infarction, cardiac death and major cardiac complications. Patients receiving chronic beta-blocker therapy were more likely to suffer a myocardial infarction (p < 0.05). These findings differ from the published effects of acute beta-blockade. Reasons for this discrepancy are considered.

Infective endocarditis due to the CDC group M6 bacillus.

Although staphylococcal endocarditis has occasionally been associated with a TTP-like syndrome, a similar syndrome has not been reported with endocarditis due to aerobic gram-negative rods. We report a case of subacute bacterial endocarditis with a thrombocytopenic syndrome that at first resembled TTP which was due to an unusual gram-negative rod. This case emphasizes the need for repeated examination of the bacteremic patient to detect the changing murmurs of endocarditis.

Photodecomposition of DDA.

The photodecomposition of aqueous solutions of 2,2-bis (p-chlorophenyl) acetic acid (DDA) was slow in sunlight and rapid in the laboratory, producing p,p'-dichlorobenzophenone (DCB), p-chlorobenzaldehyde, p-chlorophenol, and several unidentified polar products. p,p'-Dichlorobenzilic acid, and p,p'-dichlorobenzhydrol gave rise to the same photoproducts, while bis-(p-chlorophenyl) methane (DDM) and chlorogenzilate were converted only to DCB. DCB and p-chlorogenzaldehyde proved to be resistant to photodegradation but gradually produced p-chlorobenzoic acid which, in turn, formed p-hydroxybenzoic and benzoic acids, probably the last environmentally detectable links in the long chain of DDT degradation to CO2 and water. High pressure liquid chromatography (HPLC) proved to be ideal for separating and quantitating the parent compounds and their photoproducts directly from the aqueous photolysates or from methanol solutions of the isolates and standards.