Able-bodied Controls Research Articles

Mediolateral angular momentum changes in persons with amputation during perturbed walking

Over 50% of individuals with lower limb amputation fall at least once each year. These individuals also exhibit reduced ability to effectively respond to challenges to frontal plane stability. The range of whole body angular momentum has been correlated with stability and fall risk. This study determined how lateral walking surface perturbations affected the regulation of whole body and individual leg angular momentum in able-bodied controls and individuals with unilateral transtibial amputation. Participants walked at fixed speed in a Computer Assisted Rehabilitation Environment with no perturbations and continuous, pseudo-random, mediolateral platform oscillations. Both the ranges and variability of angular momentum for both the whole body and both legs were significantly greater (p<0.001) during platform oscillations. There were no significant differences between groups in whole body angular momentum range or variability during unperturbed walking. The range of frontal plane angular momentum was significantly greater for those with amputation than for controls for all segments (p<0.05). For the whole body and intact leg, angular momentum ranges were greater for patients with amputation. However, for the prosthetic leg, angular momentum ranges were less for patients than controls. Patients with amputation were significantly more affected by the perturbations. Though patients with amputation were able to maintain similar patterns of whole body angular momentum during unperturbed walking, they were more highly destabilized by the walking surface perturbations. Individuals with transtibial amputation appear to predominantly use altered motion of the intact limb to maintain mediolateral stability.

Reduction in Torsional Stiffness and Strength at the Proximal Tibia as a Function of Time Since Spinal Cord Injury.

Spinal cord injury (SCI) is characterized by marked bone loss and a high rate of low-energy fracture around regions of the knee. Changes in the mechanical integrity of bone after SCI are poorly defined, and a better understanding may inform approaches to prevent fractures. The purpose of this study was to quantify reductions in torsional stiffness and strength at the proximal tibia as a function of time since SCI. Sixty adults with SCI ranging from 0 to 50 years of duration and a reference group of 10 able-bodied controls received a CT scan of the proximal tibia. Measures of integral bone mineral were calculated for the total proximal tibia, and localized measures of cortical and trabecular bone mineral were calculated for the epiphysis, metaphysis, and diaphysis. Torsional stiffness (K) and strength (T(ult)) for the total proximal tibia were quantified using validated subject-specific finite element models. Total proximal tibia measures of integral bone mineral, K, and T(ult) decreased exponentially (r(2) = 0.52 to 0.70) and reached a new steady state within 2.1 to 2.7 years after SCI. Whereas new steady-state values for integral bone mineral and K were 52% to 56% (p < 0.001) lower than the reference group, the new steady state for T(ult) was 69% (p < 0.001) lower than the reference group. Reductions in total proximal tibia measures occurred through a combination of trabecular and endocortical resorption, leaving a bone comprised primarily of marrow fat rather than hydroxyapatite. These findings illustrate that a short therapeutic window exists early (ie, 2 years) after SCI, during which bone-specific intervention may attenuate reductions in mechanical integrity and ultimately prevent SCI-related fragility fracture.

Step-to-step transition work during level and inclined walking using passive and powered ankle-foot prostheses.

Individuals with leg amputations who use passive prostheses have greater metabolic demands than non-amputees likely due to limited net positive work compared to a biological ankle. New powered ankle-foot prostheses can perform net positive mechanical work to aid push-off capabilities, which may reduce metabolic demands. Compare step-to-step transition work and metabolic demand during level and inclined walking using passive and powered ankle-foot prostheses. Repeated measures. Six individuals with transtibial amputation and six able-bodied controls walked at a standardized speed across level ground and up a 5° incline. Calculated measures included mechanical work during step-to-step transitions from the trailing prosthetic to leading intact limb, steady state metabolic rate, and ankle joint kinetics and kinematics. The powered prosthesis generated 63% greater trailing limb step-to-step transition work than the passive during level walking only (p = 0.004). Metabolic rate was lower with the powered prosthesis during level (p = 0.006) but not inclined walking (p = 0.281). The powered prosthesis increased ankle power compared to the passive, to the extent that power was normalized to controls during inclined walking and greater than controls during level walking. The powered prosthesis improved ankle power, metabolic rate, and step-to-step transition work on level ground, with few negative consequences on inclines. These results may be used to guide the development and use of actively powered prosthetic devices in high-functioning individuals. Overall, powered devices offer biomechanical and metabolic benefits over passive energy storage and return designs on level ground and perform as well as a passive model on inclines. The lower metabolic demand when using the powered device may delay fatigue for individuals with transtibial amputation when walking over level ground.

Somatosensory phenotype is associated with thalamic metabolites and pain intensity after spinal cord injury

Neuropathic pain is one of the most difficult consequences of spinal cord injury (SCI). The clinical correlates of the underlying mechanisms responsible for neuropathic pain are not well understood, although methods such as quantitative somatosensory testing (QST) or brain imaging have been used to further a mechanism-based understanding of pain. Our previous SCI study demonstrated a significantly lower glutamate-glutamine/myo-inositol ratio (Glx/Ins) in the anterior cingulate cortex in persons with severe neuropathic pain compared with those with less severe neuropathic pain or pain-free, able-bodied controls, suggesting that a combination of decreased glutamatergic metabolism and glial activation may contribute to the development of severe neuropathic pain after SCI. The present study aimed to determine the relationships between somatosensory function below the level of injury and low thalamic Glx/Ins in persons with intense neuropathic pain after SCI. Participants underwent QST and a 3 Tesla proton magnetic resonance spectroscopy. A cluster analysis including SCI participants resulted in 1 group (n = 19) with significantly (P < 0.001) greater pain intensity (6.43 ± 1.63; high neuropathic pain [HNP], and lower Glx/Ins [1.22 ± 0.16]) and another group (n = 35) with lower pain intensity ratings (1.59 ± 1.52, low neuropathic pain [LNP], and higher Glx/Ins [1.47 ± 0.26]). After correcting for age, QST indicated significantly greater somatosensory function in the HNP group compared with the LNP group. Our results are consistent with research suggesting that damage to, but not abolition of, the spinothalamic tract contributes to development of neuropathic pain after SCI and that secondary inflammatory processes may amplify residual spinothalamic tract signals by facilitation, disinhibition, or sensitization.

A region-based two-step P300-BMI in patients with spinocerebellar ataxia

Event Abstract Back to Event A region-based two-step P300-BMI in patients with spinocerebellar ataxia Kouji Takano1, Shiro Ikegami1, 2, Toshihiro Kawase1, Masahiro Nagao3, Tetsuo Komori4 and Kenji Kansaku1, 5* 1 Research Institute of National Rehabilitation Center for Persons with Disabilities, Department of Rehabilitation for Brain Function, Japan 2 Chiba University, Graduate School of Medicine, Japan 3 Tokyo Metropolitan Neurological Hospital, Department of Neurology, Japan 4 National Hakone Hospital, Japan 5 University of Electro-Communications, Japan Brain-machine interface (BMI) or brain-computer interface (BCI) is an interface technology that utilizes neurophysiological signals from the brain to control external machines or computers. We have developed a P300-based BMI system to support daily activities of persons with disabilities (Komatsu et al., 2008; Kansaku, 2011), and found that green/blue chromatic and luminance flicker matrices improved the BMI performance for able-bodied subjects and spinal cord injury patients (Takano et al, 2009; Ikegami et al., 2011). We also created a region-based 2-step speller, which has a larger flashing area than the conventional visual array. The first step used 2 × 3 regions (six choices), and the second step used 3 × 3 regions (nine choices). The bottom row was empty in the first step. We reported that the two-step procedure provided significantly increased accuracy compared with a conventional row/column speller for the amyotrophic lateral sclerosis patients (Ikegami et al., 2014). In this study, we investigated the performance of the region-based 2-step P300 BMI speller for spinocerebellar ataxia (SCA) patients and also for age- and sex-matched able-bodied control subjects. Eight SCA patients and 8 age- and sex-matched control subjects who had not trained in BMI operation before (52-72 years old; 2 men) participated in this study. They were required to input Japanese hiragana characters using the in-house P300-based BMI system. Eight channel EEG data was recorded, and a linear discriminant analysis distinguished a region that the subject gazed at from other regions of the matrix. Online accuracy was evaluated. The mean online accuracy was 70.6% for the SCA patients, and 69.5% for the able-bodied control subjects (the first step: 87.5% and 87.2%, the second step: 79.0% and 67.2%, respectively). The accuracy exceeded 70% in 5 out of 8 SCA patients and 6 out of 8 control subjects without significant training. In the 7 SCA patients whose accuracies exceeded 70% in the first step, the accuracy was significantly different between the first step and the second step (p = 0.0036). Such difference was not observed in the control subjects (p = 0.44). These results suggest that the region-based 2-step speller for P300-based BMI may be beneficial for SCA patients. Keywords: P300-BMI, spinocerebellar ataxia, brain-computer interface (BCI), Brain-machine interface (BMI), Amyotrophic lateral sclerosis (ALS) Conference: 2015 International Workshop on Clinical Brain-Machine Interfaces (CBMI2015), Tokyo, Japan, 13 Mar - 15 Mar, 2015. Presentation Type: Poster 1-4 Topic: Clinical Brain-Machine Interfaces Citation: Takano K, Ikegami S, Kawase T, Nagao M, Komori T and Kansaku K (2015). A region-based two-step P300-BMI in patients with spinocerebellar ataxia. Conference Abstract: 2015 International Workshop on Clinical Brain-Machine Interfaces (CBMI2015). doi: 10.3389/conf.fnhum.2015.218.00032 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Apr 2015; Published Online: 29 Apr 2015. * Correspondence: Dr. Kenji Kansaku, Research Institute of National Rehabilitation Center for Persons with Disabilities, Department of Rehabilitation for Brain Function, Tokorozawa, Saitama, Japan, kansakuk@dokkyomed.ac.jp Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Kouji Takano Shiro Ikegami Toshihiro Kawase Masahiro Nagao Tetsuo Komori Kenji Kansaku Google Kouji Takano Shiro Ikegami Toshihiro Kawase Masahiro Nagao Tetsuo Komori Kenji Kansaku Google Scholar Kouji Takano Shiro Ikegami Toshihiro Kawase Masahiro Nagao Tetsuo Komori Kenji Kansaku PubMed Kouji Takano Shiro Ikegami Toshihiro Kawase Masahiro Nagao Tetsuo Komori Kenji Kansaku Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. 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Modulation of hand aperture during reaching in persons with incomplete cervical spinal cord injury.

The intact neuromotor system prepares for object grasp by first opening the hand to an aperture that is scaled according to object size and then closing the hand around the object. After cervical spinal cord injury (SCI), hand function is significantly impaired, but the degree to which object-specific hand aperture scaling is affected remains unknown. Here, we hypothesized that persons with incomplete cervical SCI have a reduced maximum hand opening capacity but exhibit novel neuromuscular coordination strategies that permit object-specific hand aperture scaling during reaching. To test this hypothesis, we measured hand kinematics and surface electromyography from seven muscles of the hand and wrist during attempts at maximum hand opening as well as reaching for four balls of different diameters. Our results showed that persons with SCI exhibited significantly reduced maximum hand aperture compared to able-bodied (AB) controls. However, persons with SCI preserved the ability to scale peak hand aperture with ball size during reaching. Persons with SCI also used distinct muscle coordination patterns that included increased co-activity of flexors and extensors at the wrist and hand compared to AB controls. These results suggest that motor planning for aperture modulation is preserved even though execution is limited by constraints on hand opening capacity and altered muscle co-activity. Thus, persons with incomplete cervical SCI may benefit from rehabilitation aimed at increasing hand opening capacity and reducing flexor-extensor co-activity at the wrist and hand.

Reliability of surface EMG as an assessment tool for trunk activity and potential to determine neurorecovery in SCI.

Reliability and validity study. This study investigates the responsiveness and reliability of the brain motor control assessment (BMCA) as a standardized neurophysiological assessment tool to: (i) characterize trunk neural activity in neurologically-intact controls; (ii) measure and quantify neurorecovery of trunk after spinal cord injury (SCI). Kessler Foundation Research Center, West Orange, NJ. A standardized BMCA protocol was performed to measure surface electromyography (sEMG) recordings for seven bilateral trunk muscles on 15 able-bodied controls during six maneuvers (inhalation, exhalation, neck flexion, jendrassik, unilateral grip). Additionally, sEMG recordings were analyzed for one chronic SCI individual before electrical stimulation (ES), after ES of the lower extremities while supine, and after active stand training using body-weight support with bilateral ES. sEMG recordings were collected on bilateral erector spinae, internal and external obliques, upper and middle trapezius, biceps and triceps. For each maneuver a voluntary response index was calculated: incorporating the magnitude of sEMG signal and a similarity index (SI), which quantifies the distribution of activity across all muscles. Among all maneuvers, the SI presented reproducible assessment of trunk-motor function within (ICC: 0.860-0.997) and among (P⩾0.22) able-bodied individuals. In addition, potential changes were measured in a chronic SCI individual after undergoing two intensive ES protocols. The BMCA provides reproducible characterization of trunk activity in able-bodied individuals, lending credence for its use in neurophysiological assessment of motor control. Additionally, the BMCA as an assessment tool to measure neurorecovery in an individual with chronic SCI after intense ES interventions was demonstrated.

Cortical Activation During Visual Illusory Walking in Persons With Spinal Cord Injury: A Pilot Study

To determine the location of cortical activation during a visual illusion walking paradigm, a recently proposed treatment for spinal cord injury (SCI)-related neuropathic pain, in persons with SCI compared with able-bodied controls. Pilot experimental functional magnetic resonance imaging (fMRI) trial. Outpatient rehabilitation clinic. Persons with paraplegia (n=3) and able-bodied participants (n=5) were included in this study. Not applicable. Cortical activation as measured by the blood oxygenation level-dependent method of fMRI. During visually illusory walking there was significant activation in the somatosensory cortex among those with SCI. In contrast, able-bodied participants showed little to no significant activation in this area, but they showed activation in the frontal and premotor areas. Treatment modalities for SCI-related neuropathic pain that are based on sensory input paradigms (eg, virtual walking, visual illusory walking) may work by targeting the somatosensory cortex, an area that has been previously found to functionally reorganize after SCI.

The relationship between body composition and femoral neck osteoporosis or osteopenia in adults with previous poliomyelitis

Articles in the literature describing the association between body composition and osteoporosis in subjects with poliomyelitis are scarce. To assess the relationship between body composition and femoral neck osteoporosis or osteopenia in adults with previous polio. After excluding postmenopausal women, 44 polio (mean age ± standard deviation, 46.1 ± 3.3 years) and 44 able-bodied control volunteers (47.0 ± 4.0 years) participated in the study. Each participant's femoral neck bone mineral density (FNBMD) and whole body composition were measured using dual-energy X-ray absorptiometry. With local reference BMD values of normal young adults installed in the instrument, we obtained T-score values that depended on each FNBMD value. A T-score value of ≤-1.0 indicated decreased T-score, including osteoporosis (T-score ≤ -2.5) and osteopenia (-1.0 to -2.5). This study conducted logistic regression analyses to find factors associated with osteoporosis and osteopenia. Based on the FNBMD T-score values, 60.0% of middle-aged men with polio had osteoporosis. In adjusted logistic regression analyses, total lean tissue mass (Adjusted odds ratio [95% confidence interval], 0.74 [0.56-0.99], P < 0.05) and male gender (947.16 [6.02-148,926.16], P < 0.01) were important factors associated with decreased T-score in polio group. Osteoporosis or osteopenia is a common medical problem for middle-aged men with polio. Reduced total lean tissue mass seems to be one of the important factors associated with osteoporosis or osteopenia among subjects with polio. Further research for a clinical tool to assess lean tissue mass for subjects with polio is needed.

Does EMG control lead to distinct motor adaptation?

Powered prostheses are controlled using electromyographic (EMG) signals, which may introduce high levels of uncertainty even for simple tasks. According to Bayesian theories, higher uncertainty should influence how the brain adapts motor commands in response to perceived errors. Such adaptation may critically influence how patients interact with their prosthetic devices; however, we do not yet understand adaptation behavior with EMG control. Models of adaptation can offer insights on movement planning and feedback correction, but we first need to establish their validity for EMG control interfaces. Here we created a simplified comparison of prosthesis and able-bodied control by studying adaptation with three control interfaces: joint angle, joint torque, and EMG. Subjects used each of the control interfaces to perform a target-directed task with random visual perturbations. We investigated how control interface and visual uncertainty affected trial-by-trial adaptation. As predicted by Bayesian models, increased errors and decreased visual uncertainty led to faster adaptation. The control interface had no significant effect beyond influencing error sizes. This result suggests that Bayesian models are useful for describing prosthesis control and could facilitate further investigation to characterize the uncertainty faced by prosthesis users. A better understanding of factors affecting movement uncertainty will guide sensory feedback strategies for powered prostheses and clarify what feedback information best improves control.

Greatly increased prevalence of esophageal dysmotility observed in persons with spinal cord injury.

The effects of spinal cord injury (SCI) on esophageal motility are largely unknown. Furthermore, due to the complete or partial loss of sensory innervation to the upper gastrointestinal tract, a symptom-based diagnosis of esophageal dysmotility is problematic in the SCI population. To determine the prevalence and characterize the type of motility disorders observed in persons with chronic SCI compared with that of able-bodied (AB) controls based on esophageal pressure topography isometrics acquired by high-resolution manometry and categorized by application of the Chicago Classification. High-resolution manometry of the esophagus was performed in 39 individuals: 14 AB, 12 with paraplegia (level of injury between T4-T12) and 13 with tetraplegia (level of injury between C5-C7). A catheter containing multiple pressure sensors arranged at 360° was introduced into the esophagi of subjects at a distance that allowed visualization of both the upper esophageal sphincters (UES) and lower esophageal sphincters (LES). After a period to acquire pressures at baseline, subjects were asked to perform 10 wet swallows with 5-mL boluses of isotonic saline while esophageal pressure and impedance were being recorded. No significant differences were noted for gender, age, or body mass index between AB and SCI groups. Twenty-one of 25 (84%) subjects with SCI had at least one motility abnormality: 12% with Type II achalasia, 4% with Type III achalasia, 20% with esophagogastric junction outflow obstruction, 4% with the hypercontractile esophagus, and 48% with peristaltic abnormalities (weak peristalsis with small or large defects or frequent failed peristalsis). In contrast, only 7% (1 out of 14) of the AB subjects had any type of esophageal motility disorder. Despite the lack of subjective complaints and clinical awareness, esophageal dysmotility appears to be a highly prevalent condition in persons with SCI. The use of new and improved techniques, as well as a more stringent classification system, permitted the identification of the presence of nonspecific motility disorders in almost all SCI subjects, including four individuals who were previously undiagnosed with achalasia. Future work in persons with SCI is required to clarify the clinical impact of this observation and to study potential associations between esophageal dysmotility, gastroesophageal reflux disease, and pulmonary function. An increased awareness of esophageal dysfunction in the SCI population may lead to the development of new clinical guidelines for the diagnosis, prevention, and treatment of these largely unrecognized disorders.

Bone mass and hormone analysis in patients with spinal cord injury: evidence for a gonadal axis disruption.

Bone loss is a constant finding in patients with spinal cord injury (SCI). We sought to evaluate potential modifiable factors that could lead to bone loss in complete motor paraplegia by examining gonadal axis hormones, vitamin D status, and bone markers. This is a cross sectional. It includes SCI Outpatient. Twenty-nine chronic male patients with SCI were compared with 17 age-matched, able-bodied men. The bone mineral density (BMD) of lower limbs and lumbar spine were measured using dual x-ray absorptiometry. Parathormone, 25-hydroxyvitamin D [25(OH)D], collagen type I C-terminal telopeptide (CTX), and sexual hormone were measured. Patients with SCI had lower BMD at the inferior limbs sites. CTX showed an inverse relationship with the time since injury. Patients had lower free T levels (SCI, 12.00 ± 2.91 vs controls, 19.51 ± 5.72; P ≤ .001), and the majority (72%) had normal/low levels of gonadotropins. Low T, however, was not related to low bone mass in patients with SCI. In the controls, the 25(OH)D level was positively correlated with the T and with the lumbar spine BMD, but these correlations were not observed in the SCI. Impairment of testicular function after SCI was indicated by the low levels of T and the loss of correlation between T and 25(OH)D levels; this correlation was present in the able-bodied controls. Inappropriate levels of gonadotropins were identified in most patients, featuring a hypogonadotropic hypogonadism and suggesting a disruption of the pituitary-gonadal axis. T concentrations might not be an effective target for bone loss therapy.

The effect of powered prosthesis control signals on trial-by-trial adaptation to visual perturbations.

Powered prostheses have the potential to restore abilities lost to amputation; however, many users report dissatisfaction with the control of their devices. The high variability of the EMG signals used to control powered devices likely burdens amputees with high movement uncertainty. In able-bodied subjects uncertainty affects adaptation, control, and feedback processing, which are often modeled using Bayesian statistics. Understanding the role of uncertainty for amputees might thus be important for the design and control of prosthetic devices. Here we quantified the role of uncertainty using a visual trial-by-trial adaptation approach. We compared adaptation behavior with two control interfaces meant to mimic able-bodied and prosthesis control: torque control and EMG control. In both control interfaces, adaptation rate decreased with high feedback uncertainty and increased with high mean error. However, we did observe different patterns of learning as the experiment progressed. For torque control, subjects improved and consequently adapted slower as the experiment progressed, while no such improvements were made for EMG control. Thus, EMG control resulted in overall adaptation behavior that supports Bayesian models, but with altered learning patterns and higher errors. These findings encourage further studies of adaptation with powered prostheses. A better understanding of the factors that alter learning patterns and errors will help design prosthesis control systems that optimize learning and performance for the prosthesis user.

Assessing complexity of heart rate variability in people with spinal cord injury using local scale exponents.

Detrended fluctuation analysis (DFA) has been widely used to study dynamics of heart rate variability (HRV), which provides a quantitative parameter, the scaling exponent a, to represent the correlation properties of RR interval series. However, it has been demonstrated that HRV exhibits complex behavior that cannot be fully described by a single exponent. This study aimed to investigate whether local scale exponent α(t) with t being the time scale can reveal new features of HRV that cannot be reflected by DFA coefficients. To accurately estimate α(t), we developed an approach for correcting a(t) at small scales and verified the approach using simulated signals. We studied HRV in 12 subjects with spinal cord injury and 14 able-bodied controls during sitting and prone postures. The results showed that α(t) provides complementary views of HRV, suggesting that it may be used to evaluate the effects of SCI-induced autonomic damage on HRV.

Can external lateral stabilization reduce the energy cost of walking in persons with a lower limb amputation?

The aim of this study was to examine whether impaired balance control is partly responsible for the increased energy cost of walking in persons with a lower limb amputation (LLA). Previous studies used external lateral stabilization to evaluate the energy cost for balance control; this caused a decrease in energy cost, with concomitant decreases in mean and variability of step width. Using a similar set-up, we expected larger decreases for LLA than able-bodied controls. Fifteen transtibial amputees (TT), 12 transfemoral amputees (TF), and 15 able-bodied controls (CO) walked with and without external lateral stabilization provided via spring like cords attached to the waist. Effects of this manipulation on energy cost, step parameters, and pelvic motion were evaluated between groups. TT (-5%) and CO (-3%) showed on average a small reduction in energy cost when walking with stabilization, whereas TF exhibited an increase in energy cost (+6.5%) The difference in the effect of stabilization was only significant between TT and TF. Step width, step width variability, and medio-lateral pelvic displacement decreased significantly with stabilization in all groups, especially in TT. Contrary to expectations, external lateral stabilization did not result in a larger decrease in the energy cost of walking for LLA compared to able-bodied controls, suggesting that balance control is not a major factor in the increased cost of walking in LLA. Alternatively, the increased energy cost with stabilization for TF suggests that restraining (medio-lateral) pelvic motion impeded necessary movement adaptations in LLA, and thus negated the postulated beneficial effects of stabilization on the energy cost of walking.

Dynamic stability of superior vs. inferior body segments in individuals with transtibial amputation walking in destabilizing environments

Interestingly, young and highly active people with lower limb amputation appear to maintain a similar trunk and upper body stability during walking as able-bodied individuals. Understanding the mechanisms underlying how this stability is achieved after lower-leg amputation is important to improve training regimens for improving walking function in these patients. This study quantified how superior (i.e., head, trunk, and pelvis) and inferior (i.e., thigh, shank, and feet) segments of the body respond to continuous visual or mechanical perturbations during walking. Nine persons with transtibial amputation (TTA) and 12 able-bodied controls (AB) walked on a 2 m × 3 m treadmill in a Computer Assisted Rehabilitation Environment (CAREN). Subjects were perturbed by continuous pseudo-random mediolateral movements of either the treadmill platform or the visual scene. TTA maintained a similar local and orbital stability in their superior body segments as AB throughout both perturbation types. However, for their inferior body segments, TTA subjects exhibited greater dynamic instability during perturbed walking. In TTA subjects, these increases in instability were even more pronounced in their prosthetic limb compared to their intact leg. These findings demonstrate that persons with unilateral lower leg amputation maintain upper body stability in spite of increased dynamic instability in their impaired lower leg. Thus, transtibial amputation does significantly impair sensorimotor function, leading to substantially altered dynamic movements of their lower limb segments. However, otherwise relatively healthy patients with unilateral transtibial amputation appear to retain sufficient remaining sensorimotor function in their proximal and contralateral limbs to adequately compensate for their impairment.

Ultrasonographic measurement of the acromiohumeral distance in spinal cord injury: Reliability and effects of shoulder positioning

ObjectiveTo investigate the reliability of ultrasonographic measurement of acromiohumeral distance (AHD) and the effects of shoulder positioning on AHD among manual wheelchair users (MWUs) with spinal cord injury (SCI) and an able-bodied control group.MethodsTen MWUs with SCI and 10 able-bodied subjects participated in this study. The ultrasonographic measurements of AHD from each subject were obtained by two raters during passive and active scapular plane arm elevation in neutral, 45°, 90° with and without resistance and in a weight relief raise position. The measurements were recorded again by each rater using the same procedures after a 30-minute time interval. All raters were blinded to each other's measurements.SettingUniversity Laboratories and Veteran Affairs Healthcare System.ResultsIntra-rater (intraclass correlation coefficient, ICC > 0.83) and inter-rater (ICC > 0.78) reliability was excellent for both the MWUs with SCI and able-bodied groups across all arm positions except for the 45° position in the control group for one of the raters (intra-rater: ICC < 0.40 and inter-rater: ICC < 0.60). AHD significantly reduced when the shoulder was in the 90° arm elevated positions with or without resistance.ConclusionFindings from our study demonstrated that ultrasonography is a reliable means to evaluate AHD in both able bodied and individuals with SCI, who are known to have significant shoulder pathology. This technique could be used to develop reference measures and to identify changes in AHD caused by interventions.

Increased Central Arterial Stiffness Explains Baroreflex Dysfunction in Spinal Cord Injury

After cervical spinal cord injury (SCI), orthostatic hypotension and intolerance commonly ensue. The cardiovagal baroreflex plays an important role in the acute regulation of blood pressure (BP) and is associated with the onset of presyncope. The cardiovagal baroreflex is dysfunctional after SCI; however, this may be influenced by either increased stiffening of the arteries containing the stretch-receptors (which has been shown in SCI) or a more downstream neural mechanism (i.e., solitary nucleus, sinoatrial node). Identifying where along this pathway baroreflex dysfunction occurs may highlight a potential therapeutic target. This study examined the relationship between spontaneous cardiovagal baroreflex sensitivity (BRS) and common carotid artery (CCA) stiffness in those with high level SCI before and after midodrine (alpha1-agonist) administration, as well as in able-bodied controls, to evaluate: (1) the role arterial stiffening plays mediating baroreflex function after SCI and (2) the effect of normalizing BP on these parameters. Three to five min recordings of beat-by-beat BP and heart rate, as well as 30 sec duration recordings of CCA diameter were used for analysis. All participants were tested supine and during upright-tilt. Arterial stiffness (β-stiffness index) was elevated in those with SCI when upright (+12%; p<0.05). Further, β-stiffness index was negatively related to reduced BRS in those with SCI when upright (R2=0.55; p<0.05), but not in able-bodied persons. Normalizing BP did not improve BRS or CCA stiffness. This study clearly shows that reduced BRS is closely related to increased arterial stiffness in the population with SCI.

Tu1973 Esophageal Dysmotility Is Highly Prevalent in Persons With SCI Compared to Able-Bodied Controls As Identified With High-Resolution Manometry and the Use of the Chicago Classification

BACKGROUND: A paucity of information exists with regard to the effects of spinal cord injury (SCI) on esophageal motility. Due to the complete or partial loss of sensory innervation to the esophagus, a symptom-based diagnosis of esophageal dysmotility is often delayed, if even appreciated, although some degree of occult impaired motility is likely to be present. AIM: To compare the incidence and to determine the differences in esophageal motility parameters between persons with chronic SCI and able-bodied controls by the use of high resolution manometry (HRM) and the Chicago Classification (CC). METHODS: HRM was performed in 39 asymptomatic individuals: 14 able-bodied controls (AB) and 25 SCI subjects (level of injury between C5-T10). A catheter that contained multiple pressure sensors which were arranged at 360 degrees was introduced into the esophagi of subjects at a distance that permitted both the upper (UES) and lower (LES) esophageal sphincters to be captured. After a baseline period to assess basal pressures, each subject was asked to perform 10 wet swallows of 5 ml boluses of isotonic saline while esophageal pressure and impedance were recorded. Esophageal topography parameters (EPT) were calculated using analysis software and two independent reviewers classified the manometric findings according to the CC. RESULTS: There were no significant differences in gender, age or BMI between AB and SCI groups. Eighty-four % (21 out of 25) of the SCI subjects studied were diagnosed with at least one motility abnormality: 12% with Type II achalasia, 4% with Type III achalasia, 20% with EGJ outflow obstruction, 4%with a hypercontractile esophagus, and 48%with peristaltic abnormalities (i.e., weak peristalsis with small or large defects or frequent failed peristalsis). In contrast, only 7% (1 out of 14) of the AB subjects was diagnosed with any type of motility disorder (hypercontractile esophagus). CONCLUSION: Despite the lack of subjective complaints or clinical awareness, esophageal dysmotility appears to be relatively prevalent in the SCI population. The use of new and improved esophageal manometry techniques and a more stringent classification system permitted the presence of wide array of motility disorders in almost all subjects with SCI to be identified, including achalasia that went previously undiagnosed in 4 subjects. Future work will be required to clarify the clinical

A region-based two-step P300-based brain–computer interface for patients with amyotrophic lateral sclerosis

The P300-based brain-computer interface (BCI) is designed to help patients with motor disabilities to control their environment, and it has been used successfully in patients with amyotrophic lateral sclerosis (ALS). However, some ALS patients were unable to use the visual P300-BCI with the conventional row/column presentation. In this study, we evaluated the effect of a newly developed region-based two-step P300 speller, which has a larger flashing area than the conventional visual array. Seven ALS patients and seven age- and sex-matched able-bodied control subjects were required to input hiragana characters using our P300 BCI system. We prepared two types of input procedures, the conventional row/column (RC) speller and the two-step speller, and evaluated their online performance. The mean online accuracy of the ALS patients was 24% for the RC condition and 55% for the two-step condition. The accuracy of the control subjects was 71% and 83% for the RC and two-step condition, respectively. Accuracy in ALS patients was significantly lower than that in the control subjects, and the new visual stimuli significantly increased accuracy of ALS patients. Using the new speller, two ALS patients showed an initial accuracy sufficient for practical use (>70%). The other two ALS patients, who performed better in the first trial using the new speller, continued to experience the BCI system, and their mean accuracy increased to 92%. The two-step procedure for the visual P300 BCI system provided significantly increased accuracy for ALS patients compared with a conventional RC speller. The new region-based two-step P300 speller was effective in ALS patients, and the system may be beneficial to expand their range of activities.