Lower Extremity Responses Research Articles

Comparative biofidelity of the Hybrid III and THOR 50th male ATDs under three restraint conditions during frontal sled tests

Objective The purpose of this study was to provide a whole-body biofidelity assessment of the Hybrid III (HIII) and THOR 50th percentile male anthropomorphic test devices (ATDs) during frontal sled tests, incorporating data from kinematics, chest deflection, and test buck reaction load cells. Additionally, the accuracy of the injury risk prediction capabilities for each ATD was evaluated against injuries observed in matched postmortem human surrogate (PMHS) tests. Methods Sled tests, designed to simulate a United States New Car Assessment Program (US-NCAP) frontal test, were conducted using the HIII, THOR, and 8 approximately 50th percentile male PMHS under 3 restraint conditions. The test buck was instrumented with load cells on the steering column, knee bolster supports, and foot supports. ATD and PMHS reaction force–time histories were quantitatively compared using the ISO/TS-18571 objective rating metric. Previously published biofidelity analyses of kinematic and chest deflection data from the same tests were combined with the reaction force analyses to perform an overall assessment of the comparative biofidelity of each ATD. Injury risk predictions from existing HIII and proposed THOR injury risk curves for the US-NCAP were compared to observed injuries. Results For the reaction forces, the HIII and THOR had similar levels of biofidelity on average, except for 2 locations. The HIII produced more biofidelic knee bolster support forces, and the THOR lap belt forces were more biofidelic. The comparative biofidelity of the ATDs also varied by body region. The THOR head response was more biofidelic, whereas the HIII thorax and lower extremity responses had higher biofidelity. When all body regions were pooled, the HIII was more biofidelic, but differences between ATDs were generally small. Both ATDs were able to predict the observed injuries, except for the HIII chest, HIII neck, and THOR neck, all of which underpredicted PMHS injury outcomes. Conclusions This study revealed that biofidelity assessed through response time histories and accuracy of injury risk predictions do not always align. Specifically, the HIII had marginally better time history biofidelity, whereas the THOR had better injury prediction. However, not all THOR responses could be fully assessed, so more work is needed to assess the THOR in complex loading environments.

Bilateral Motor Responses to Transcranial Magnetic Stimulation in Preterm Children at 9 Years of Age.

This study was aimed to evaluate motor tracts integrity in nondisabled preterm-born (PT) children at 9 years of age. Overall, 18 PT and 13 term-born (T) children without motor disability were assessed by transcranial magnetic stimulation (TMS). Motor-evoked potentials (MEPs) were measured bilaterally from the abductor pollicis brevis (APB) and the tibialis anterior (TA) muscles. Muscle responses could be stimulated from all patients. Overall, 83.3 and 23.1% of PT and T children, respectively, had mild clumsiness (p = 0.001). One PT and three T children had immediate bilateral responses in the upper extremities. Seven PT children had delayed ipsilateral APB responses after left and ten after right TMS. Three controls had delayed ipsilateral responses. Ipsilateral lower extremity responses were seen in one PT after right and two PT children and one T child after left TMS. The results did not correlate to groups, genders, clumsiness, or handedness. Children of PT and T may have bilateral motor responses after TMS at 9 years of age. Ipsilateral conduction emerges immediately or more often slightly delayed and more frequently in upper than in lower extremities. Bilateral motor conduction reflects developmental and neurophysiological variability in children at 9 years of age. MEPs can be used as a measure of corticospinal tract integrity in PT children.

Generalized motor inhibitory deficit in Parkinson's disease patients who freeze.

Freezing of gait is a disabling symptom of Parkinson's disease (PD) that involves failure to initiate and continue motor activity appropriately. PD disrupts fronto-basal ganglia circuitries that also implement the inhibition of responses, leading to the hypothesis that freezing of gait may involve fundamental changes in both initiation and inhibition of motor actions. We asked whether PD patients who show freezing of gait show selective deficits in their ability to inhibit upper and lower extremity reactions. We compared older healthy controls, older PD controls without freezing of gait, and older PD participants with freezing of gait, in stop-signal tasks that measured the initiation (go trials) and inhibition (stop trials) of both hand and foot responses. When only go trials were presented, all three groups showed similar initiation speeds across lower and upper extremity responses. When stop-signal trials were introduced, both PD groups slowed their reactions nearly twice as much as healthy controls. While this adjustment helped PD controls stop their actions as quickly as healthy controls, PD patients with freezing showed significantly delayed inhibitory control of both upper and lower extremities. When anticipating the need to stop their actions urgently, PD patients show greater adjustments (i.e., slowing) to reaction speed than healthy controls. Despite these proactive adjustments, PD patients who freeze show marked impairments in inhibiting both upper and lower extremity responses, suggesting that freezing may involve a fundamental disruption to the brain's inhibitory control system.

Case Studies of Transcranial Electrical Motor Evoked Potentials (TCeMEP) on Patients with Charcot-Marie-Tooth Disease during Posterior Spinal Instrumentation and Fusion

Neuromuscular disease can present many challenges to monitoring technologists in the operating room. This became evident when we received a request to monitor a patient with Charcot-Marie-Tooth disease during posterior spinal instrumentation and fusion for scoliosis. It has been well documented that the nerve conduction velocity is delayed with Charcot-Marie-Tooth disease (Pareyson et al. 2006). The latencies we normally encounter for somatosensory and motor evoked potentials for the upper extremity responses are between 15 and 20 msec, and for the lower extremity responses, are usually between 25 and 35 msec. Recording with a sweep of 100 msec, we assumed we could record a response with a significant delay. We never imagined we would need to increase the sweep time to 500 msec or more in order to record the responses from the lower extremities.

Proposal of injury risk curves for evaluating pedestrian femur/pelvis injury risk using EEVC upper legform impactor based on accident reconstruction

New injury risk curves for the evaluation of pedestrian femur and pelvic injury risk by means of the upper legform impactor of the European Enhanced Vehicle-Safety Committee (EEVC) developed by the Transport Research Laboratory are proposed in this study. Lower extremity responses related to the risk of pedestrian femur and pelvic fractures caused by the bonnet leading edge and wing contact in a real-world pedestrian accident, such as impact force and bending moment, were reconstructed in the present study using the EEVC upper legform impactor. The femur and pelvic injury risk curves were developed from application of the model of Weibull cumulative frequency to measured impact force and bending moment. The newly developed injury risk curves indicated that an impact force of 6.3 kN and a bending moment of 417 Nm measured by the EEVC upper legform impactor correspond to a 0.2 probability of femur and pelvic fractures. The injury risk curves also showed that an impact force of 7.5 kN and a bending moment of 510 Nm measured by the EEVC upper legform impactor correspond to a 0.5 probability of injuries.

New injury reference values determined for TRL legform impactor from accident reconstruction test

New injury reference values for evaluation of injury risk to pedestrian leg by means of the legform impactor with rigid leg and thigh developed by the Transport Research Laboratory (TRL) are proposed in the present study. Lower extremity responses related to the risk of pedestrian leg injuries induced by the bumper contact in a real-world pedestrian accident, such as knee angle and lower leg acceleration in the impact direction, were reconstructed using this legform impactor. The injury reference values for the TRL legform impactor for estimation of the risk of collateral ligament injury and tibia fracture were determined from application of t-test and the maximum likelihood method of logistic regression to these responses. Furthermore, the bumper areas that cause the most severe lower extremity injuries in car-pedestrian impacts were identified from in-depth accident databases in Japan.