Oleg Vesnovsky

Are locking screws advantageous with plate fixation of humeral shaft fractures? A biomechanical analysis of synthetic and cadaveric bone.

Objectives: To investigate whether locking screws offer any advantage over nonlocking screws for plate fixation of humeral shaft fractures for weight-bearing applications. Design: Mechanical evaluation of stiffness in torsion, bending, and axial loading and failure in axial loading in synthetic and cadaveric bone. Setting: Biomechanical laboratory in an academic medical center. Methods: We modeled a comminuted midshaft humeral fracture in both synthetic and cadaveric bone. Humeri were plated posteriorly. Two study groups each used identical 10-hole, 3.5-mm locking compression plates that can accept either locking or nonlocking screws. The first group used only nonlocking screws and the second only locking screws. Stiffness testing and failure testing were performed for both the synthetic bones (n = 6) and the cadaveric matched pairs (n = 12). Fatigue testing was set at 90,000 cycles of 440 N of axial loading. Main Outcome Measures: Torsion, bending, and axial stiffness and axial failure force after cyclic loading. Results: With synthetic bones, no significant difference was observed in any of the 4 tested stiffness modes between the plates with locking screws and those with nonlocking screws (anteroposterior, P = 0.51; mediolateral, P = 0.50; axial, P = 0.15; torsional, P = 0.08). With initial failure testing of the constructs in axial loading, both plates failed above anticipated physiologic loads of 440 N (mean failure load for both constructs >4200 N), but no advantage to locking screws was shown. The cadaveric portion of the study also showed no biomechanical advantage of locking screws over nonlocking screws for stiffness of the construct in the 4 tested modes (P > 0.40). Fatigue and failure testing showed that both constructs were able to withstand strenuous fatigue and to fail above anticipated loads (mean failure >3400 N). No difference in failure force was shown between the 2 groups (P = 0.67). Conclusions: Synthetic and cadaveric bone testing showed that locking screws offer no obvious biomechanical benefit in this application.

Performance Testing of Huber Needles for Coring of Port Septa

The Food and Drug Administration received complaints of Huber needles creating cores in the septa of ports of gastric banding devices. One of these complaints represented a cluster of similar events, even though no deviations from design specifications or recommended practices were subsequently identified by the manufacturer. The authors conducted this comparative investigation of off-the-shelf Huber needles and ports from several manufacturers to determine if engineering parameters could be identified that could account for the coring complaints. Huber needles from ten manufacturers were evaluated for coring using intravascular access ports from five manufacturers. A detailed optical analysis was also performed to identify needle features that would possibly account for coring. The majority of the tested needles performed as they should, i.e., they perforated the port septa without creating cores. However, needles that did produce cores were found to have sharp edges at the heel edge of the needle lumen, the edge of the ground bevel opposite from the needle tip that opens to the inner surface of the cannula tube. Manufacturing processes, which dulled or rounded the sharp heel of the bevel after bevel grinding, prevented coring. As a result of this investigation one manufacturer voluntarily recalled their product and another manufacturer implemented coring testing as part of their quality control. To prevent coring needles from entering the market as a result of manufacturing flaws, optical inspection of the heel edge and coring testing should be performed as part of routine quality control.

Performance Testing of Fast Read Digital Thermometers

Body temperature monitoring of humans has been an important tool for diagnosing infections, detecting fever, monitoring thermoregulation functions during surgical procedures, and assessing postsurgery recovery. Temperature is measured at various body sites including the pulmonary artery, rectum, bladder, distal esophagus and nasopharynx, sublingual surface of the tongue, under the armpit, tympanic membrane, and forehead. Inexpensive, off-the-shelf digital thermometers are generally used to measure temperature orally or under the arm. Currently, many such thermometers are available with a “fast read” capability, where they produce temperature readings in 5–10 s. In a previous study [1], we used a custom-designed, small thermistor bead-based thermometer (NIST traceable) and a computer data acquisition system to measure and record temperatures at a rate of 7 Hz (“reference thermometer”). Therefore, the reference thermometer records the temperature rise (transient data) from the initial contact with the skin until equilibrium. The small bead ensures rapid heat transfer and accurate temperature measurements. Relevant temperature measurements required at least 20 s, even with a sophisticated design and expensive support electronics. In this study we conducted clinical temperature measurement research on children to evaluate the accuracy of three off-the-shelf digital thermometers (brands A, B, and C) compared to our reference thermometer [1]. The off-the-shelf thermometers state that 5–11 s are required to produce a temperature measurement, depending on the brand. All of the off-the-shelf thermometers claimed an accuracy of 60.2 F; while one manufacturer (brand A) specified that the accuracy was achieved in a water bath. Also some manufacturers stated that the axillary measurements will be lower than the oral measurements: 1 F for brand A and 1–2 F for brand C. Our experience with our reference thermometer indicates that longer than 5–11 s would be needed to measure body temperature with the claimed accuracy. The purpose of this study was to investigate the accuracy of the fast read thermometers compared to our reference thermometer.

Determining critical design parameters for improved body temperature measurements: a new method and clinical study.

Readily available store brand, or “home,” thermometers are used countless times in the home and clinic as a first diagnostic measure of body temperature. Measurement inaccuracies may lead to unnecessary medical visits or medication (false positives), or, potentially worse, lack of intervention when a person is truly sick (false negatives). A critical first step in the design process is to determine the shortcomings of the existing designs. For this project, we evaluated the accuracy of three currently available store brand thermometers in a pediatric population. The accuracies of the thermometers were assessed by comparing their body temperature predictions to those measured by a specially designed and calibrated and fast-responding reference thermometer. The reference thermometer was placed at the measurement site simultaneously with the store brand thermometer and recorded the temperature at the measurement site continuously. More than 300 healthy or sick pediatric subjects were enrolled in this study. Temperatures were measured at both the oral and axillary (under the arm) sites. The store brand thermometer measurements characteristically deviated from the reference thermometer temperature after 120 s, and the deviations did not follow a consistent pattern. The Brand C thermometers had the greatest deviations of up to 3.7 F (2.1 C), while the Brand A thermometers had the lowest deviations; however, they still deviated by up to 1.9 F (1.1 C). The data showed that the tested store brand thermometers had lower accuracy than the 60.2 F (0.1 C) indicated in their Instructions for Use. Our recorded reference (transient) data showed that there was a wide variation in the transient temperature profiles. The store brand thermometers tested stated in their documentation that they are able to predict a body temperature based on transient temperature values over the first 5–10 s of measurements, implying that they use an embedded algorithm to extrapolate to the steady-state temperature. Significant deviations from the maximum temperature after time t 1⁄4 4.6t0.63 illustrated that the transient temperature profiles may not be represented by an exponential function with a single time constant, t0.63. The accuracy of those embedded algorithms was not confirmed by our study, since the predicted body temperatures do not capture the large variations observed over the initial 10 s of the measurements. A thermometer with an error of several degrees Fahrenheit may result in a false positive or negative diagnosis of fever in children. The transient temperature measurements from our clinical study represent unique and critical data for helping to design the next generation of readily available, highly accurate, home thermometers. [DOI: 10.1115/1.4041589]

Evaluating Accuracy of Digital Thermometers Using a Tissue Phantom Mimicking Normal and Fever Environments

Body temperature monitoring is an important tool for helping clinicians diagnose infections, detect fever, monitor thermoregulation functions during surgical procedures, and assess postsurgery recovery. Commercially available (“store brand”) fast read thermometers have been developed to predict body core temperatures based on the first few seconds of temperature recordings either orally or under the arm. Our recent clinical study [1] demonstrated temperature variations from one body site to another and their deviations from the true body core temperature. Our study was the first where temperature transients were recorded in a clinical setting by a fast responding reference thermometer—based on a thermistor bead sensor—at two body sites. It is also the first time the reference thermometer was placed simultaneously with a store brand digital thermometer to evaluate the digital thermometer’s algorithm-based temperature predictions. There was a large temperature measurement variation between the reference and store brand thermometers during the initial 10 s of measurement. Compared to the measurements from the reference thermometer after 120 s, the store brand thermometers routinely overestimated or underestimated the actual temperature by up to 2 C in both healthy and sick patients. The predictive algorithm apparently does not capture the initial temperature variations; therefore, the accuracies of the store brand thermometers used were questionable. The objective of this study was to develop a tissue-equivalent human upper arm phantom as a system to simulate different clinical thermal conditions of a human body to evaluate the performance of store brand digital thermometers.

Evaluation of Temperature Transients at Various Body Temperature Measuring Sites Using a Fast Response Thermistor Bead Sensor

Body temperature monitoring of humans has been an important tool for helping clinicians diagnose infections, detect fever, monitor thermoregulation functions during surgical procedures, and assess post-surgery recovery.1–3 Fever itself is typically not considered a disease. It is a response of the body to a disease, which is often inflammatory in nature. Elevation of the set point at the body temperature control center, the brain hypothalamus, is caused by circulating pyrogens produced by the immune system responding to diseases. Since the brain hypothalamus is not easily accessed by thermometers, other body locations have been identified as alternative measuring sites. Those sites include the pulmonary artery, rectum, bladder, distal esophagus and nasopharynx, sublingual surface of the tongue, under the armpit, tympanic membrane, and forehead.Copyright