Roland Müller

Quantitative gait analysis after bilateral total knee arthroplasty with two different systems within each subject

The functional behavior of two kinematically different knee arthroplasty systems within each subject was studied by gait analysis (three-dimensional kinematics, kinetics, dynamic electromyography) in five elderly patients, 2 to 5 years after bilateral surgery. Clinical results were good, yet gait velocity was reduced (range, 0.57-1.1 m/s), with a shortened stride length and a decreased duration of single-limb stance in all subjects. Force plate recordings revealed an undynamic gait with slow loading, reduced modulation of the vertical forces, and poor fore/aft shears. Sagittal plane knee motion during gait was reduced in all subjects, with trunk and pelvic compensation patterns for foot clearance. Muscle activity around the knee was prolonged bilaterally, with activity modulation related to the motion pattern. Although the stride parameters were quite symmetric, there was a marked asymmetry of the motion pattern, with a side-to-side difference of peak knee flexion during stance and swing phase of up to 15 degrees. This finding, however, was not clearly related to the type of prosthesis. Even within one subject, significant side-to-side variability may persist, which leads to asymmetry of the motion pattern, unrelated to the kinematic design of the implant. Other factors, such as the patella-extensor mechanism, ligament balancing, leg-length discrepancy, proprioception, continuation of a preoperative habit, or a contralateral influence, may explain part of the asymmetry seen in these subjects.

Modulation of locomotor activity in complete spinal cord injury

The aim of this study was to evaluate the modulation of muscle activity during locomotor-like movements by different walking speeds in subjects with a motor complete spinal cord injury (SCI) compared to actively- and passively-walking control subjects without neurological deficit. Stepping movements on a treadmill were induced and assisted by a driven gait orthosis. Electromyographic (EMG) muscle activity of one leg (rectus and biceps femoris, tibialis anterior and gastrocnemius) was recorded and analyzed at three stepping velocities with similar body weight support in both subject groups. In SCI subjects, the EMG amplitude of biceps femoris, tibialis anterior and gastrocnemius was in general similar or weaker than in passively- and actively-stepping control subjects, but that of rectus femoris was larger. The degree of co-activation between tibialis anterior and gastrocnemius was higher in SCI than in control subjects. A significant velocity-dependent EMG modulation was present in all four-leg muscles in both subject groups. In SCI subjects, this EMG modulation was similar to that in actively stepping control subjects. It is concluded that in complete spastic SCI subjects, spinal neuronal circuits underlying locomotion can to a large extent adequately respond to a change in external drive to adapt the neuronal pattern to a new locomotion speed. The application of various speeds might enhance the effect of locomotor training in incomplete SCI subjects.

Virtual realities as motivational tools for robotic assisted gait training in children: A surface electromyography study

Patients active cooperation is essential to achieve good outcome in pediatric rehabilitation. Therefore, virtual environments were developed to enhance robotic assisted gait training. The purpose of this study was to evaluate virtual realities as motivational tools during robotic assisted gait training with children in the pediatric Lokomat®. Nine children with different gait disorders and eight healthy children participated in the study. Muscular effort of the lower leg was assessed by surface electromyography during a randomly designed training protocol with virtual realities. Self reported motivation was investigated with two questionnaires. Comparisons were drawn through repeated measurement Analysis of Variance and paired-t-tests. The logarithmic transformed data showed that the electromyographic activity output in both groups was significantly higher during tasks with virtual realities than during normal walking conditions. These results support that virtual realities seem to be efficient motivational tools to increase childrens muscular effort in the pediatric Lokomat®. The gaming aspect of virtual realities keeps children highly engaged during repetitive tasks.

Acute effects of whole-body vibration on trunk muscles in young healthy adults

Little is known about the impact of whole body vibration (WBV) training on trunk muscles. Thus, this study investigated the acute effects of WBV on back and abdominal muscle activity. Twenty-five healthy subjects (24.7 ± 3.0 years, 17 men) conducted eight common static exercises for the back and abdominal muscles in a random order on a vibration platform, with and without vibration. Surface EMG was measured from back and abdominal muscles. Vibration-induced motion artefacts were removed from the EMG signal. Muscle activity with and without vibration was normalized to maximal voluntary contraction (MVC) and compared. The addition of vibration resulted in significant increases in muscle activity particularly in the exercises for the abdominal muscles of up to 7.2 ± 5.5% MVC (median ± semi-interquartile range). In the back muscles, the largest difference by adding vibration was 1.6 ± 1.4% MVC (median ± semi-interquartile range). The results of this study indicate a low to moderate increase in trunk muscle activation due to WBV. Presumably, this effect might depend on the distance from the corresponding muscle to the vibration platform and on how much the exercise position challenges body balance. However, the relevance of these findings has to be further investigated in training studies.

Measurement of muscle stiffness using robotic assisted gait orthosis in children with cerebral palsy: a proof of concept

Purpose. To evaluate the feasibility and reliability of a novel stiffness assessment tool implemented in the driven gait orthosis Paediatric Lokomat; to investigate the influence of single robotic-assisted gait training (RAGT) on muscle stiffness in children with cerebral palsy (CP). Methods. Ten children with spastic CP conducted a single standard RAGT session and stiffness was assessed before and after the RAGT. Nine of the ten subjects were tested twice on the same day to investigate test–retest reliability, intraclass correlation coefficients (ICCs), standard error of measurement (SEM), coefficient of variation of the method error (CVME) and resistive torques during passive leg movements (stiffness in Nm/°) were calculated. Results. ICCs showed high reliability (0.83–0.97) for hip and knee movements. SEM and CVME indicated 0.028–0.085 Nm/°, 9.5–23.0% of test–retest variability in hip and 0.018–0.064 Nm/°, 13.3–43.5% in knee measures. Using the assessment tool, a significant decrease in muscle stiffness in participants, especially in children with high levels of muscle tone, could be shown after a single session of RAGT. Conclusions. The assessment tool L-STIFF is a feasible tool for automated measurement of stiffness in children with CP, but it is not sensitive enough to record small changes in muscle tone.

Isometric back muscle endurance: An EMG study on the criterion validity of the Ito test

The validity of the Sorensen test as a measure for back muscle endurance is controversial due to a possible impact of hip extensor muscles. The aim of this study was to investigate the criterion validity of an alternative test (Ito test) compared to the Sorensen test. Both procedures were performed by 29 healthy subjects (11 women) for 5s and until exhaustion (randomized order). EMG activity was measured from 3 lumbar back and 3 hip extensor muscles. Muscular involvement in test positions was calculated as percentage of maximal voluntary contraction (MVC). Muscle fatigue was determined by the normalized regression coefficient of the median frequencies of the EMG power spectrum (NMF(slope)). Prediction of holding time by NMF(slope) values was investigated using regression analysis. In the test positions, the hamstring muscles were activated to a higher MVC percentage in the Sorensen than in the Ito test, while the iliocostalis muscle was less activated. Similarly, the iliocostalis (p=0.006) and the multifidi muscles (p=0.03) significantly contributed to predict holding time in the Ito test, whereas the multifidi muscles (p=0.001) and the semitendinosus muscle (p=0.046) did so in the Sorensen test. The results of this study indicate that the Ito test might present a valuable alternative for testing back muscle endurance in LBP patients.

Sleep quality and the risk of work injury: a Swiss case-control study

Sleep problems are a well‐known risk factor for work injuries, but less is known about which vulnerable populations are most at risk. The aims of this study were to investigate the association between sleep quality and the risk of work injury and to identify factors that may modify the association. A case–control study including 180 cases and 551 controls was conducted at the University Hospital in Basel, Switzerland, from 1 December 2009 to 30 June 2011. Data on work injuries and sleep quality were collected. Adjusted odds ratios and 95% confidence intervals of the association between sleep quality and work injury were estimated in multivariable logistic regression analyses and were stratified by hypothesized effect modifiers (age, gender, job risk, shift work, sleep duration and working hours). Poor sleep quality was associated significantly with work injury of any type (P < 0.05) and with being caught in particular (P < 0.05). The association between poor sleep quality and work injury was significantly higher for workers older than 30 years (odds ratio>30 1.30 versus odds ratio≤30 0.91, P < 0.01), sleeping 7 h or less per night (odds ratio≤7 1.17 versus odds ratio>7 0.79, P < 0.05) and working 50 h or more per week (odds ratio≥50 1.79 versus odd ratio<50 1.10, P < 0.01). Work injury risk increased with increasing severity of sleep problems (P < 0.05). Prior work injury frequency increased with decreasing sleep quality (P < 0.05). Older age, short sleep duration and long working hours may enhance the risk of work injuries associated with sleep quality.

Leg surface electromyography patterns in children with neuro-orthopedic disorders walking on a treadmill unassisted and assisted by a robot with and without encouragement.

BackgroundRobot-assisted gait training and treadmill training can complement conventional physical therapy in children with neuro-orthopedic movement disorders. The aim of this study was to investigate surface electromyography (sEMG) activity patterns during robot-assisted gait training (with and without motivating instructions from a therapist) and unassisted treadmill walking and to compare these with physiological sEMG patterns.MethodsNine children with motor impairments and eight healthy children walked in various conditions: (a) on a treadmill in the driven gait orthosis Lokomat®, (b) same condition, with additional motivational instructions from a therapist, and (c) on the treadmill without assistance. sEMG recordings were made of the tibialis anterior, gastrocnemius lateralis, vastus medialis, and biceps femoris muscles. Differences in sEMG amplitudes between the three conditions were analyzed for the duration of stance and swing phase (for each group and muscle separately) using non-parametric tests. Spearman’s correlation coefficients illustrated similarity of muscle activation patterns between conditions, between groups, and with published reference trajectories.ResultsThe relative duration of stance and swing phase differed between patients and controls, and between driven gait orthosis conditions and treadmill walking. While sEMG amplitudes were higher when being encouraged by a therapist compared to robot-assisted gait training without instructions (0.008 ≤ p-value ≤ 0.015), muscle activation patterns were highly comparable (0.648 ≤ Spearman correlation coefficients ≤ 0.969). In general, comparisons of the sEMG patterns with published reference data of over-ground walking revealed that walking in the driven gait orthosis could induce more physiological muscle activation patterns compared to unsupported treadmill walking.ConclusionsOur results suggest that robotic-assisted gait training with therapeutic encouragement could appropriately increase muscle activity. Robotic-assisted gait training in general could induce physiological muscle activation patterns, which might indicate that this training exploits restorative rather than compensatory mechanisms.

Sleep problems and work injury types: a study of 180 patients in a Swiss emergency department.

INTRODUCTION Sleep problems present a risk for work injuries and are a major occupational health concern worldwide. Knowledge about the influence of sleep problems on work injury patterns is limited. Therefore, the aim of this study was to identify potential associations between different types of work injuries and sleep quality, sleep duration, and daytime sleepiness. METHODS In this hospital-based study, 180 male and female patients with work injuries were recruited at the Emergency Department of the University Hospital Basel, Switzerland, from December 1st 2009 to June 30th 2011. The data on work injury characteristics, sleep problems, and potential confounders, such as demographic, health, lifestyle, occupational and environmental factors, were collected. Multivariable logistic regression analyses were performed to investigate the relationship between sleep problems and various types of work injury. RESULTS Each dimension of sleep problems - sleep quality, sleep duration and daytime sleepiness - was a significant risk factor for at least one type of work injury. The strongest association was found for musculoskeletal injuries and falls with short sleep duration (odds ratio [OR] 5.41, 95% confidence interval [CI] 1.81-16.22). The standardised scores of the Pittsburgh sleep quality index (PSQI) and the Epworth sleepiness scale (ESS) did not discriminate between injury types. CONCLUSION Employees with sleep problems were more likely to suffer from certain types of work injuries. This should be considered by employers monitoring work injuries and implementing prevention measures in the companys health and safety management.