Assessment of instability in type B pelvic ring fractures.

Pelvic ring fractures have increased in incidence and operative fixation over the past several decades. These are dynamic injuries but decisions on operative management are still often made on the basis of static imaging. Expert opinion varies greatly on which injuries require fixation and how much fixation. Examination under anaesthesia has been shown to guide management of pelvic injuries by more accurately assessing levels of instability.

Characterization of transection spinal cord injuries by monitoring somatosensory evoked potentials and motor behavior.

Standardization of spinal cord injury (SCI) models is crucial for reproducible injury in research settings and their objective assessments. Basso, Beattie and Bresnahan (BBB) scoring, the traditional behavioral evaluation method, is subjective and susceptible to human error. On the other hand, neuro-electrophysiological monitoring, such as somatosensory evoked potential (SSEP), is an objective assessment method that can be performed continuously for longitudinal studies. We implemented both SSEP and BBB assessments on transection SCI model. Five experimental groups are designed as follows: left hemi-transection at T8, right hemi-transection at T10, double hemi-transection at left T8 and right T10, complete transection at T8 and control group which receives only laminectomy with intact dura and no injury on spinal cord parenchyma. On days 4, 7, 14 and 21 post-injury, first BBB scores in awake and then SSEP signals in anesthetized rats were obtained. Our results show SSEP signals and BBB scores are both closely associated with transection model and injury progression. However, the two assessment modalities demonstrate different sensitivity in measuring injury progression when it comes to late-stage double hemi-transection, complete transection and hemi-transection injury. Furthermore, SSEP amplitudes are found to be distinct in different injury groups and the progress of their attenuation is increasingly rapid with more severe transection injuries. It is evident from our findings that SSEP and BBB methods provide distinctive and valuable information and could be complementary of each other. We propose incorporating both SSEP monitoring and conventional BBB scoring in SCI research to more effectively standardize injury progression.

Vigilance Decrement and Enhancement Techniques: A Review.

This paper presents the first comprehensive review on vigilance enhancement using both conventional and unconventional means, and further discusses the resulting contradictory findings. It highlights the key differences observed between the research findings and argues that variations of the experimental protocol could be a significant contributing factor towards such contradictory results. Furthermore, the paper reveals the effectiveness of unconventional means of enhancement in significant reduction of vigilance decrement compared to conventional means. Meanwhile, a discussion on the challenges of enhancement techniques is presented, with several suggested recommendations and alternative strategies to maintain an adequate level of vigilance for the task at hand. Additionally, this review provides evidence in support of the use of unconventional means of enhancement on vigilance studies, regardless of their practical challenges.

Brain Connectivity Analysis Under Semantic Vigilance and Enhanced Mental States.

In this paper, we present a method to quantify the coupling between brain regions under vigilance and enhanced mental states by utilizing partial directed coherence (PDC) and graph theory analysis (GTA). The vigilance state is induced using a modified version of stroop color-word task (SCWT) while the enhancement state is based on audio stimulation with a pure tone of 250 Hz. The audio stimulation was presented to the right and left ears simultaneously for one-hour while participants perform the SCWT. The quantification of mental states was performed by means of statistical analysis of indexes based on GTA, behavioral responses of time-on-task (TOT), and Brunel Mood Scale (BRMUS). The results show that PDC is very sensitive to vigilance decrement and shows that the brain connectivity network is significantly reduced with increasing TOT, p < 0.05. Meanwhile, during the enhanced state, the connectivity network maintains high connectivity as time passes and shows significant improvements compared to vigilance state. The audio stimulation enhances the connectivity network over the frontal and parietal regions and the right hemisphere. The increase in the connectivity network correlates with individual differences in the magnitude of the vigilance enhancement assessed by response time to stimuli. Our results provide evidence for enhancement of cognitive processing efficiency with audio stimulation. The BRMUS was used to evaluate the emotional states of vigilance task before and after using the audio stimulation. BRMUS factors, such as fatigue, depression, and anger, significantly decrease in the enhancement group compared to vigilance group. On the other hand, happy and calmness factors increased with audio stimulation, p < 0.05.

Periodontally accelerated osteogenic orthodontics combined with recombinant human bone morphogenetic protein-2: An outcome assessment.

CONTEXT: Periodontally accelerated osteogenic orthodontics (PAOO) combines alveolar corticotomy, bone graft materials, and the application of orthodontic forces for rapid correction of malocclusions. AIMS: The present study aims to primarily assess differences in orthodontic treatment duration, bone quality around corticotomy sites, postoperative healing, and subjective pain when corticotomy was done conventionally and with the placement of recombinant human bone morphogenetic protein-2 (rhBMP-2). SETTINGS AND DESIGN: Thirty individuals participated in this study. Individuals were randomly assigned into each of the following experimental groups; C + BMP: Corticotomy with 0.5 µg/mL rhBMP-2 and C: Corticotomy only. MATERIALS AND METHODS: Clinical parameters included recording the duration of the treatment period, visual analog scale scores and early wound healing index scores. The evaluation of bone density was performed at baseline, 3 months, and 6 months by using RVG. STATISTICAL ANALYSIS USED: Two-way analysis of variance and post hoc multiple comparison tests were used to compare data between test and control groups at different time points. RESULTS: rhBMP-2 application was effective in reducing the overall treatment time and resulted in an increase in bone density around corticotomy sites at the end of the treatment period when compared to conventional corticotomy procedure. Placement of rhBMP-2 neither delayed wound healing nor affected participant pain scores. CONCLUSIONS: From this trial conducted over a period of 6 months, rhBMP-2 has the potential to function as a regenerative material in PAOO.

Novel Modeling of Somatosensory Evoked Potentials for the Assessment of Spinal Cord Injury.

OBJECTIVE: Previous work has shown that differences in the somatosensory evoked potential (SEP) signals between a normal spinal pathway and spinal pathway affected by spinal cord injury (SCI) provide a means to study the degree of injury. This paper proposes a novel quantitative SCI assessment method using time-domain SEP signals. METHODS: A pruned and unstructured fit between SEP signals from a normal spinal pathway and a spinal pathway affected by SCI is developed using methods inspired by recent results in sparse reconstruction theory. The coefficients from the resulting fit are used to develop a quantitative assessment of SCI that is tested on actual SEP signals collected from rodents that have been subjected to partial and complete spinal cord transection. RESULTS: The proposed method provides a rich parametric measure that integrates SEP amplitude, time latency, and morphology, while exhibiting a high degree of correlation with existing subjective and quantitative SCI assessment methods. CONCLUSION: The proposed SCI encapsulates a model of the injury to quantify SCI. SIGNIFICANCE: The proposed SCI quantification method may be used to complement existing SCI assessment methods.

Natural Progression of Spinal Cord Transection Injury and Reorganization of Neural Pathways.

The spinal cord injury (SCI) transection model accurately represents traumatic laceration and has been widely used to study the natural history and reorganization of neuropathways and plasticity in the central nervous system (CNS). This model is highly reproducible, which makes it ideal for studying the progression of injury as well as endogenous recovery and plasticity in the CNS. Five experimental groups of transection injury were designed: left hemitransection; right hemitransection; double hemitransection; complete transection injuries; and laminectomy-only control. We used somatosensory evoked potentials (SSEPs) as an objective electrophysiological assessment tool and motor behavior testing (Basso, Beattie, and Bresnahan [BBB] scoring) to functionally assess the neural pathways post-injury. Histological examinations were carried out to investigate the extent of injury and spinal cord morphological changes. Significant (p < 0.05) electrophysiological changes were observed and were verified by an increase in SSEP amplitude in somatosensory cortices for all four injury groups during days 4 and 7 post-injury. Degree of plasticity among the groups was distinguished by changes in SSEP amplitude and BBB scores. Our results support our previous published findings (using a contusive model of SCI), which shows that the reorganization of neuropathways and plasticity persist in time and are not transient phenomena. SSEPs are a reliable tool to assess the functionality of neural pathways and their projections to higher CNS structures such as the cortices. They enable us to determine residual function and the changes within the CNS post-injury and consistently track these events over time. The results from our study provide supporting evidence for the presence of neuronal network reorganization and plasticity in the CNS after transection SCI.

Brain source localization in the presence of leadfield perturbations.

This paper studies the performance of the recently developed G-MUSIC algorithm as applied to the problem of brain source localization. G-MUSIC is a form of weighted MUSIC that performs better in scenarios where only limited sample support is available. Two transfer function based calibration algorithms are also developed to estimate the location of neural activity in the brain accurately when the measured leadfield is perturbed. The localization performance of G-MUSIC is compared to traditional MUSIC and quantified in terms of the localization error. Simulations suggest that G-MUSIC can offer significantly improved localization accuracy over conventional MUSIC.

ERP signal estimation from single trial EEG.

Non-invasive EEG recordings are subject to effects such as surface conduction, resulting in very low signal to noise ratio (SNR). The conventional approach of using signal averaging to improve the SNR cannot be used for single trial EEG estimation. As such, this paper proposes a beamforming based technique that can be used to improve the signal quality from a signal trial EEG measurement. Results on experimental data show that the proposed technique can successfully isolate the signal of interest from background processes.

Effect of isoflurane on somatosensory evoked potentials in a rat model.

Somatosensory evoked potentials (SEPs) are widely used in the clinic as well as research to study the functional integrity of the different parts of sensory pathways. However, most general anesthetics, such as isoflurane, are known to suppress SEPs, which might affect the interpretation of the signals. In animal studies, the usage of anesthetics during SEP measurements is inevitable due to which detailed effect of these drugs on the recordings should be known. In this paper, the effect of isoflurane on SEPs was studied in a rat model. Both time and frequency properties of the cortical recordings generated by stimulating the tibial nerve of rat's hindlimb were investigated at three different isoflurane levels. While the anesthetic agent is shown to generally suppress the amplitude of the SEP, the effect was found to be nonlinear influencing more substantially the latter part of waveform. This finding will potentially help us in future work aiming at separating the effects of anesthetics on SEP from those due to injury in the ascending neural pathways.

Cognitive workload estimation due to vague visual stimuli using saccadic eye movements.

Visual perception is affected by the quality of stimulus. In this paper, we investigate the rise in cognitive workload of an individual performing visual task due to vague visual stimuli. We make use of normalized average peak saccadic velocity to estimate the cognitive workload. Results obtained from 16 human subjects show that the mean of peak saccadic velocity increases with workload indicating that faster saccades are required to obtain information as the workload increases. This technique should find application in assessment of vigilance and cognitive performance in many demanding professional, industrial and transportation situation.

Quantification of the bone healing process using information of B-Mode ultrasound image.

Ultrasound provides a promising non-invasive, safe, objective means of monitoring and quantifying bone healing. In this paper, the relationship between the ultrasound image intensity and the acoustic impedance was exploited to develop a quantitative measure towards assessment and monitoring of the bone healing process. Information theoretic criterion (KLD) was used to quantify the degree of bone healing using the intensity histogram of the callus region obtained from B-Mode ultrasound. Results from a pilot experimental study, show that the proposed method is capable of accurately quantifying the degree of bone healing.

Histogram based quantification of spinal cord injury level using somatosensory evoked potentials.

This paper uses an entropy based metric to study the somatosensory evoked potential (SEP) in rodents afflicted with focal demyelination spinal cord injury (SCI). It has been shown that amplitude characteristics of the SEP signal are a strong indicator of the integrity of the spinal cord sensory pathways. Compared to conventional correlation based metrics, the metric used in this paper exploits the amplitude histogram of SEP signals to provide a robust assessment of the different degrees of demyelination in the spinal cord. Results are presented using actual SEP signals collected on rodents with various levels of SCI.