Wear-and-tear knee osteoarthritis affects over 27 million of the US population for ages over 50 (Lawrence 2008) and about 37% of age over 60 (NHANES III, 2006). In Taiwan, the statistics are about ...
Recently, various designs and material manufactured interspinous process devices (IPDs) are on the market in managing symptomatic lumbar spinal stenosis (LSS). However, atraumatic fracture of the intervening spinous process has been reported in patients, particularly, double or multiple level lumbar decompression surgery with IPDs. This study aimed to biomechanically investigate the effects of few commercial IPDs, namely DIAM TM , Coflex TM , and M-PEEK, which were implanted into the L2-3, L3-4 double-level lumbar spinal processes. A validated finite element model of musculoskeletal intact lumbar spinal column was modified to accommodate the numerical analysis of different implants. The range of motion (ROM) between each vertebra, stiffness of the implanted level, intra stress on the intervertebral discs and facet joints, and the contact forces on spinous processes were compared. Among the three implants, the Coflex system showed the largest ROM restriction in extension and caused the highest stress over the disc annulus at the adjacent levels, as well as the sandwich phenomenon on the spinous process at the instrumented levels. Further, the DIAM device provided a superior loading-sharing between the two bridge supports, and the M-PEEK system offered a superior load-sharing from the superior spinous process to the lower pedicle screw. The limited motion at the instrumented segments were compensated by the upper and lower adjacent functional units, however, this increasing ROM and stress would accelerate the degeneration of un-instrumented segments.
Aims The aim of this study was to observe the degradation process and therapeutic effect of drug-eluting biodegradable biliary stents (DBBS), and to evaluate sequential changes in their mechanical properties.
To investigate whether whole-body reaching (WBR) could be a task with adequate and gradable dynamic balance challenges for stroke patients.A total of 23 subjects with hemiplegia, after their first stroke, participated in this study. The degree of dynamic balance challenges of WBR was graded by varying the distance to the targets that the subjects had to reach. A foot-pressure measurement system was used to measure the amount of center-of-pressure shift during performance of WBR and sit-to-stand transfer. The Berg Balance Scale (BBS) was administered, and the BBS total score was calculated. Static and dynamic BBS subscores were separately calculated to further understanding of the subject performance regarding balance. Paired t tests were used to examine the effects of target distance on center-of-pressure shift. Correlations between measures of center-of-pressure shift during performance of WBR and of sit-to-stand transfer, BBS total score, BBS static subscores, and BBS dynamic subscores and measures of center-of-pressure shift during performance of sit-to-stand transfer were analyzed.Significant effects of distance on three of the variables representing amount of center-of-pressure shift were found (P < 0.05). The correlations between WBR and sit-to-stand transfer were positive and moderate. The correlations between WBR and sit-to-stand transfer were stronger when the subjects were reaching for a closer target than when reaching for a farther target. The correlations between WBR and BBS total score were weak to moderate; the correlations between WBR and three scores of the BBS across target distance were inconsistent; and the correlations were higher when the subjects were reaching for a farther target than when reaching for a closer target.WBR for targets at different distances imposed graded dynamic balance challenges on stroke patients and might be an appropriate dynamic balance measure. However, WBR, as applied in this study, showed limitations in measuring the lateral dynamic stability of stroke patients.
The cerebral cortex provides sensorimotor integration and coordination during motor control of daily functional activities. Power spectrum density (PSD) based on electroencephalography (EEG) has been employed as an approach that allows an investigation of the spatial-temporal characteristics of neuromuscular modulation; however, the biofeedback mechanism associated with cortical activation during motor control remains unclear among elderly individuals. Thirty one community-dwelling elderly participants were divided into low fall-risk potential (LF) and high fall-risk potential (HF) groups based upon the results obtained from a receiver operating characteristic analysis of the ellipse area of the center of pressure. EEG was performed while the participants stood on a 6-degree-of-freedom Stewart platform, which generated continuous perturbations and done either with or without the virtual reality scene. The present study showed that when there was visual stimulation and poor somatosensory coordination, a higher level of cortical response was activated in order to keep postural balance. The elderly participants in the LF group demonstrated a significant and strong correlation between postural-related cortical regions; however, the elderly individuals in the HF group did not show such a relationship. Moreover, we were able to clarify the roles of various brainwave bands functioning in motor control. Specifically, the gamma and beta bands in the parietal–occipital region facilitate the high-level cortical modulation and sensorimotor integration, whereas the theta band in the frontal–central region is responsible for mediating error detection during perceptual motor tasks. Finally, the alpha band is associated with processing visual challenges in the occipital lobe. With a variety of motor control demands, increment in brainwave band coordination is required to maintain postural stability. These investigations shed light on the cortical modulation of motor control among elderly participants with varying fall-risk potentials. The results suggest that, although elderly adults may be without neurological deficits, inefficient central modulation during challenging postural conditions could be an internal factor that contributes to the risk of fall. Furthermore, training that helps to improve coordinated sensorimotor integration may be a useful approach to reduce the risk of fall among elderly populations or when patients suffer from neurological deficits.
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