Evaluation of the biodynamic response of the hand-arm system and hand-tool designs: a brief review.

Hand-operated tools transmit a high magnitude of vibration exposure to the hand-arm system that causes occupational diseases. The health effects caused in various countries for the past years due to usage of hand tools are necessary to identify the occupational disorders. Researchers have conducted various studies on biological effects, hand-transmitted vibration exposure and biodynamic responses throughout the years. This article goes over each of these studies in detail, as well as identifying areas where more research is needed. The majority of studies deal with the following topics: general guidelines for hand-transmitted vibrations; assessment techniques of vibration exposure; hand-tool evaluation methods; influence of hand-tool design to overcome the biomechanical effects; and finite element modelling for quantifying vibration exposure. In response to this, understanding the biodynamic behaviour of the hand-arm system is useful for better ergonomic intervention in hand tools to reduce fatigue and increase comfort.

Simulation of L-4 lumbar spine model of motorist exposed to vibration from speed hump.

BACKGROUND: The motorcycle is often used in recurring travel between locations, dense traffic, poor conditioned roads and thus the repetitive loading on the musculoskeletal system of the rider leads to risk factors associated with musculoskeletal disorders. This study was aimed to examine the biomechanical response of the L-4 lumbar spine while riding the motorcycle on the speed hump at 20 km/h. METHODS: Three-dimensional (3D) model of the L-4 lumbar spine was reconstructed based on the CT scan data obtained from the subjects. Material properties of the L-4 lumbar spine were assumed to be isotropic and homogenous. Mesh convergence and sensitivity analyses were performed and validated before simulation. Static and dynamic analyses were accomplished using quasi-static and steady-state dynamic analyses. RESULTS: Static analysis results show that the highest stress concentrations were found around the pedicle and spinal canal. It is an expected commonplace for injuries because of loading. The dynamic simulation results showed the major resonance of the L-4 lumbar spine model is about 8-40 Hz. The stress, displacement, velocity, and acceleration value declines beyond 40 Hz as the frequency increases. CONCLUSIONS: The simulation specifies the symmetric and unsymmetrical distributions of vibration magnitude regions of the lumbar spine. This study provides the modelling of the lumbar spine (L-4) and validated the effect of overloading failure as well as identified the biomechanical behaviour.

Influence of handle shape and size to reduce the hand-arm vibration discomfort.

BACKGROUND: Non-automated tool handles transmit a large magnitude of vibration to operators' hands, causing discomfort and pain. Therefore, the need for a better handle design is a matter of prime concern to overcome musculoskeletal disorders such as hand-arm vibration syndrome. OBJECTIVE: This study aimed to examine the influence of handle shapes in reducing the transmission of hand-arm vibration. METHODS: Seven different handles were designed and fabricated using 3D printing technology at the SSN College of Engineering, with consideration for the anatomical shape of the hand. The frequency-weighted Root Mean Square (RMS) values of the vibration levels transmitted were recorded at the wrist of twelve subjects, unaffected by musculoskeletal disorders. Subjective ratings of vibration and comfort perception were measured using the Borg Scale of Perceived Exertion. RESULTS: The total vibration value (ahv) of each of the six novel prototype handles (B-G) was compared to that of the reference handle denoted handle-A. The vibration reductions for handles B to G respectively were 0.542 m/s2 (14.59%), 0.481 m/s2 (12.95%), 0.351 m/s2 (9.45%), 0.270 m/s2 (7.27%), 0.407 m/s2 (10.96%) and 0.192 m/s2 (5.17%). CONCLUSIONS: A significant level of vibration reduction was achieved by the prototype handles. Qualitative feedback from the study subjects suggests that they were not aware of the levels of vibration being transmitted to the hand with each handle.

Factors associated with recurrent stroke and recanalization in patients presenting with isolated symptomatic carotid occlusion.

BACKGROUND AND PURPOSE: Patients with symptomatic internal carotid artery (ICA) occlusion constitute a small proportion of stroke/transient ischaemic attack patients who are at increased risk of early stroke recurrence and poor outcome. The optimal medical treatment for patients with symptomatic ICA occlusion who are ineligible for thrombolysis or thrombectomy is unknown. METHODS: Consecutive patients presenting at a single center with newly diagnosed symptomatic ICA occlusion (not involving the circle of Willis) were retrospectively reviewed. Those treated with intravenous thrombolysis or intra-arterial thrombolysis/thrombectomy were excluded. Patients were divided into two groups based on whether they experienced recurrent in-hospital stroke. RESULTS: The selected study population (n = 33) represented a small (20.4%) proportion of all newly symptomatic carotid occlusions, who nevertheless had an elevated risk of recurrent stroke during admission (24.2%). Of the variables examined (age, gender, admission National Institutes of Health Stroke Scale score, vascular risk factors, atrial fibrillation, prior stroke/transient ischaemic attack and anticoagulation within 48 h of presentation), only anticoagulation was significantly associated with a lower risk of in-hospital recurrent stroke. Anticoagulated patients showed a decreased incidence of stroke recurrence within the first week (6.7% vs. 38.9%, P = 0.032) and fewer strokes or deaths at 1 month (13.3% vs. 47.1%, P = 0.040). Hemorrhagic transformation was not observed in any patient. On follow-up imaging, ICA recanalization was significantly more frequent in anticoagulated patients (46.2% vs. 9.1%, P = 0.047). CONCLUSION: Patients with newly diagnosed symptomatic ICA occlusion (not involving the circle of Willis) represent a small but high risk subgroup of patients with carotid occlusion. Early anticoagulation was associated with fewer recurrent strokes and increased ICA recanalization. Larger scale prospective studies may be justified.

Association of CT perfusion parameters with hemorrhagic transformation in acute ischemic stroke.

BACKGROUND AND PURPOSE: Prediction of hemorrhagic transformation in acute ischemic stroke could help determine treatment and prognostication. With increasing numbers of patients with acute ischemic stroke undergoing multimodal CT imaging, we examined whether CT perfusion could predict hemorrhagic transformation in acute ischemic stroke. MATERIALS AND METHODS: Patients with acute ischemic stroke who underwent CTP scanning within 12 hours of symptom onset were examined. Patients with and without hemorrhagic transformation were defined as cases and controls, respectively, and were matched as to IV rtPA administration and presentation NIHSS score (± 2). Relative mean transit time, relative CBF, and relative CBV values were calculated from CTP maps and normalized to the contralateral side. Receiver operating characteristic analysis curves were created, and threshold values for significant CTP parameters were obtained to predict hemorrhagic transformation. RESULTS: Of 83 patients with acute ischemic stroke, 16 developed hemorrhagic transformation (19.28%). By matching, 38 controls were found for only 14 patients with hemorrhagic transformation. Among the matched patients with hemorrhagic transformation, 13 developed hemorrhagic infarction (6 hemorrhagic infarction 1 and 7 hemorrhagic infarction 2) and 1 developed parenchymal hematoma 2. There was no significant difference between cases and controls with respect to age, sex, time to presentation from symptom onset, and comorbidities. Cases had significantly lower median rCBV (8% lower) compared with controls (11% higher) (P = .009; odds ratio, 1.14 for a 0.1-U decrease in rCBV). There was no difference in median total volume of ischemia, rMTT, and rCBF among cases and controls. The area under the receiver operating characteristic was computed to be 0.83 (standard error, 0.08), with a cutoff point for rCBV of 1.09. CONCLUSIONS: Of the examined CTP parameters, only lower rCBV was found to be significantly associated with a relatively higher chance of hemorrhagic transformation.