Richard F. Sesek

Progress in Vibrotactile Threshold Evaluation Techniques: A Review

Vibrotactile threshold (VT) testing has been used for nearly a century to investigate activation of human somatosensory pathways. This use of vibrotactile stimuli provides a versatile tool for detecting peripheral neuropathies, and has been broadly used for investigation of carpal tunnel syndrome. New applications include investigation of drug-induced neuropathies and diabetes-related neuropathies. As a feedback device, the vibrotactile stimuli could be used as an information delivery system for rehabilitative feedback devices for upper limb musculoskeletal disorders or as information channels for the visually impaired. This review provides a comprehensive review of the advancement in VT measurement techniques over time and a comparison of these techniques in terms of various hardware features used and the testing protocols implemented. The advantages and limitations of these methods have been discussed along with specific recommendations for their implementation and suggestions for incorporation into clinical practice.

Impact of Isothermal Aging on the Long-Term Reliability of Fine-Pitch Ball Grid Array Packages With Different Sn-Ag-Cu Solder Joints

A direct and deleterious effect on packaging reliability has been observed during elevated temperature isothermal aging for fine-pitch ball grid array (BGA) packages with Sn-1.0Ag-0.5Cu (SAC105), Sn-3.0Ag-0.5Cu (SAC305), and Sn-37Pb solder ball interconnects. Package sizes ranging from 19 mm with 0.8-mm-pitch BGAs to 5 mm with 0.4-mm-pitch μ BGAs with three different board finishes (ImSn, ImAg, and SnPb) were evaluated. The aging temperatures were 25°C, 55°C, 85°C, and 125°C, applied for a period of 6 mo. Subsequently, the specimens were thermally cycled from -40°C to 125°C with 15-min dwell times at the high temperature. Weibull analysis of failures versus cycle number show a ~ 50% reduction in package lifetimes when aged at 125°C compared to the same at room temperature, with less dramatic but measurable reductions in lifetime at 85°C and even 55°C. In contrast, the reliability performance of Sn-37Pb is much more stable over time and temperature. The degradation was observed for both SAC alloys on all tested package sizes and board finishes. For the 19-mm SAC105 case, for example, there was a 53% (32%) reduction of characteristic lifetime at 125°C (85°C) compared to room temperature aging. The trends were in the expected directions; namely, the reliability was reduced when using higher aging temperatures, smaller solder balls, and SAC105. The dominant failure mode can be associated with the growth of Cu6Sn5 intermetallic compounds during the aging, particularly on the pad side.

Morphometry of the lower lumbar intervertebral discs and endplates: comparative analyses of new MRI data with previous findings

PurposeVariability of the human lower lumbar geometry is related to complications of disc arthroplasty surgery. Accurate morphometric descriptions are essential for the design of artificial intervertebral discs to ensure good prothesis-vertebra contact and better load distribution, and can improve spinal biomechanics. Unfortunately, current knowledge of the lower lumbar geometry is limited either in the representativeness of sample populations or the accuracy and comprehensiveness of measurements. The objective of this study was to establish an accurate and reliable measurement protocol, provide a comprehensive database of lower lumbar geometry, and compare and summarize geometric data as reported in the literature.MethodsT2-weighted magnetic resonance imaging (MRI) scans of lower lumbar spine (L3–S1), taken from 109 adult subjects, were anonymized from the digital archive of a local hospital. A total of 318 intervertebral discs and 590 endplates met the inclusion criteria and were studied. Linear and planar measurements were performed using OsiriX software, and analyzed using split plot factorial (SPF) analysis of variance (ANOVA), independent student t tests, paired sample t tests, and Tukey’s honest significant difference (HSD) post hoc tests.ResultsExcellent intra- and inter-observer reliabilities were achieved using the proposed measurement protocol. The results of this study indicated that male subjects had significantly larger geometric dimensions. L5/S1 discs had the smallest geometric dimensions compared to the discs at other two levels. Significant craniocaudal differences were found in endplate morpohometry. The error associated with using ellipsoid methods was quantified at each lower lumbar level. A large comprehensive database compiling lower lumbar geometry from many studies was established. This study provides geometric data for the female subjects at the L5/S1 level, previously lacking in the literature.ConclusionThis study demonstrates the potential of using MRI data to establish a standard measurement protocol for morphometric quantification of the lower lumbar intervertebral discs and vertebral endplates. These results are invaluable in characterizing comprehensive lower lumbar morphometry, which may provide crucial information for planning spinal surgeries, designing artificial intervertebral discs, and for biomechanical modeling of the low lack.

A survey of the prevalence of fatigue, its precursors and individual coping mechanisms among U.S. manufacturing workers

Advanced manufacturing has resulted in significant changes on the shop-floor, influencing work demands and the working environment. The corresponding safety-related effects, including fatigue, have not been captured on an industry-wide scale. This paper presents results of a survey of U.S. manufacturing workers for the: prevalence of fatigue, its root causes and significant factors, and adopted individual fatigue coping methods. The responses from 451 manufacturing employees were analyzed using descriptive data analysis, bivariate analysis and Market Basket Analysis. 57.9% of respondents indicated that they were somewhat fatigued during the past week. They reported the ankles/feet, lower back and eyes were frequently affected body parts and a lack of sleep, work stress and shift schedule were top selected root causes for fatigue. In order to respond to fatigue when it is present, respondents reported coping by drinking caffeinated drinks, stretching/doing exercises and talking with coworkers. Frequent combinations of fatigue causes and individual coping methods were identified. These results may inform the design of fatigue monitoring and mitigation strategies and future research related to fatigue development.

Incidence of Intravenous Medication Errors in a Chinese Hospital

OBJECTIVES The purpose of this study was to explore intravenous (IV) medication errors in a Chinese hospital. The specific objectives were to 1) explore and measure the frequency of IV medication errors by direct observation and identify clues to their causes in Chinese hospital inpatient wards and 2) identify the clinical importance of the errors and find the potential risks in the preparation and administration processes of IV medications. METHODS A prospective study was conducted by using the direct observational method to describe IV medication errors on two general surgery patient wards in a large teaching hospital in Beijing, China. A trained observer accompanied nurses during IV preparation rounds to detect medication errors. The difference in mean error rates between total parenteral nutrition (TPN) and non-TPN medications was tested by using the Mann-Whitney U test. RESULTS A final total of 589 ordered IV doses plus 4 unordered IV doses as prepared and administered to the patients was observed from August 3, 2010, to August 13, 2010. The overall error rate detected on the study ward was 12.8%. The most frequent errors by category were wrong dose (5.4%), wrong time (3.7%), omission (2.7%), unordered dose (0.7%), and extra dose (0.3%). Excluding wrong time errors, the error rate was 9.1%. Non-TPN medications had significantly higher error rates than did TPN medications including wrong time errors (P = 0.0162). CONCLUSIONS A typical inpatient in a Chinese hospital was subject to about one IV error every day. Pharmacists had a very limited role in ensuring the accuracy of IV medication preparation and administration processes.

The Low Back Cumulative Trauma Index Development of a Low Back Disorder Exposure Assessment Tool Based on Fatigue Failure Theory

Recent evidence strongly suggests that force and repetition interact in a consistent manner to affect the risk of musculoskeletal disorders (MSDs), likely due to an underlying fatigue failure process in affected tissues. However, no MSD tools to date have been based on fatigue failure theory. The present proposal describes a basis for incorporating fatigue failure theory in a new low back exposure assessment tool: the Low Back Cumulative Trauma Index (LBCTI), and provides an illustration of the effectiveness of such an approach using an existing database on low back disorder (LBD) risk. The LBCTI demonstrated a dose-response relationship to LBD risk.

Improving the risk assessment capability of the revised NIOSH lifting equation by incorporating personal characteristics

The impact of manual material handling such as lifting, lowering, pushing, pulling and awkward postures have been studied, and models using these external demands to assess risk of injury have been developed and employed by safety and health professionals. However, ergonomic models incorporating personal characteristics into a comprehensive model are lacking. This study explores the utility of adding personal characteristics such as the estimated L5/S1 Intervertebral Disc (IVD) cross-sectional area, age, gender and Body Mass Index to the Revised NIOSH Lifting Equation (RNLE) with the goal to improve risk assessment. A dataset with known RNLE Cumulative Lifting Indices (CLIs) and related health outcomes was used to evaluate the impact of personal characteristics on RNLE performance. The dataset included 29 cases and 101 controls selected from a cohort of 1022 subjects performing 667 jobs. RNLE risk assessment was improved by incorporation of personal characteristics. Adding gender and intervertebral disc size multipliers to the RNLE raised the odds ratio for a CLI of 3.0 from 6.71 (CI: 2.2-20.9) to 24.75 (CI: 2.8-215.4). Similarly, performance was either unchanged or improved when some existing multipliers were removed. The most promising RNLE change involved incorporation of a multiplier based on the estimated IVD cross-sectional area (CSA). Results are promising, but confidence intervals are broad and additional, prospective research is warranted to validate findings.

An Optimization Framework for Job Rotation to Better Assess the Impact on Overall Risk

We aim to study the potential of job rotation schemes to improve worker safety. To this end, we developed a novel optimization framework based on a recently proposed fatigue-failure model for musculoskeletal disorder (MSD) risk evaluation. We then employed it to conduct an illustrative case study. We demonstrate that the effect of job rotation is highly dependent on the composition of the job pool. Namely, if the job pool contains high-risk tasks (e.g., those carrying greater than 90% probability of developing a disorder), then it may be impossible to observe any risk improvement with rotations alone. On the other hand, if all jobs are already relatively low-risk, then a rotation may be very helpful in achieving risk equity.

Evaluating the Linear Integration Method of Estimating Cumulative Loading Using an Eccentric Exercise

The ability to quantify cumulative exposure is critically in understanding dose-response relationship in the development of work-related musculoskeletal disorders. Different integration methods have been used in estimating cumulative loading (force or torque). The general objective of cumulative loading integration methods has been to sum the loading exposure for each individual task, calculate by multiplying the magnitude of the task loading times the task duration, and develop an “area under the curve”. An assumption of this linear integration model is that short time exposure to high forces will result in a similar level of damage as relatively long-time exposure to low forces. In this study, three loading groups of eccentric exercise with the same “area under the curve” were performed by thirty participants (ten in each group). Relaxed elbow angle and maximum isometric voluntary contractions (MIVC) were collected before, immediately after, and 2, 4, 8 days after the exercise. The relaxed elbow angle and the changes in MIVC were significantly impacted by the loading group. This result suggests that the linear integration method of estimating cumulative loading may underestimate the impact of high force loading in terms of cumulative muscle damage.

Lumbar Muscle Fatigue Analysis Using Sorensen Test with Different Upper Body Offload Conditions

The Sorensen test has been widely used in assessing the isometric endurance of trunk muscles. In this study, a modified Sorensen test was performed using four different upper body offload conditions (0%, 25% 50% and 75%) and surface EMG (sEMG) was used to determine fatigue characteristics in lumbar muscles. Results showed that the offloading of the upper body has a statistically significant impact on the slope of the EMG median frequency, which is representative of lumbar muscle fatigue responses. The first 25% offloading significantly decreased the fatigue response in the lumbar region. In addition, the 25% offload condition was significantly different from the 75% offload condition. However, the slopes of 25% and 50% offload conditions are not statistically different from each other and same for 50% and 75% offload conditions.