Cervical muscle dysfunction in the chronic whiplash associated disorder grade II (WAD-II).

STUDY DESIGN: In a cross-sectional study, surface electromyography measurements of the upper trapezius muscles were obtained during different functional tasks in patients with a chronic whiplash associated disorder Grade II and healthy control subjects. OBJECTIVES: To investigate whether muscle dysfunction of the upper trapezius muscles, as assessed by surface electromyography, can be used to distinguish patients with whiplash associated disorder Grade II from healthy control subjects. SUMMARY OF BACKGROUND INFORMATION: In the whiplash associated disorder, there is need to improve the diagnostic tools. Whiplash associated disorder Grade II is characterized by the presence of "musculoskeletal signs." Surface electromyography to assess these musculoskeletal signs objectively may be a useful tool. METHODS: Normalized smoothed rectified electromyography levels of the upper trapezius muscles of patients with whiplash associated disorder Grade II (n = 18) and healthy control subjects (n = 19) were compared during three static postures, during a unilateral dynamic manual exercise, and during relaxation after the manual exercise. Coefficients of variation were computed to identify the measurement condition that discriminated best between the two groups. RESULTS: The most pronounced differences between patients with whiplash associated disorder Grade II and healthy control subjects were found particularly in situations in which the biomechanical load was low. Patients showed higher coactivation levels during physical exercise and a decreased ability to relax muscles after physical exercise. CONCLUSIONS: Patients with whiplash associated disorder Grade II can be distinguished from healthy control subjects according to the presence of cervical muscle dysfunction, as assessed by surface electromyography of the upper trapezius muscles. Particularly the decreased ability to relax the trapezius muscles seems to be a promising feature to identify patients with whiplash associated disorder Grade II. Assessment of the muscle (dys)function by surface electromyography offers a refinement of the whiplash associated disorder classification and provides an indication to a suitable therapeutic approach.

Estimation uncertainty in ensemble averaged surface EMG profiles during gait.

This paper reports on a theoretical investigation into some of the properties of ensemble averaged electromyographic profiles (EAEPs) which are frequently applied in gait analysis. The study treats the quantification of the surface EMG signal by means of a linear envelope detector as an estimation problem. The surface EMG signal obtained in gait analysis is modelled as an amplitude modulated Gaussian random signal with a limited bandwidth, and the smoothed rectified EMG (SRE) signal at a given instant is interpreted as an estimate of the local standard deviation over a short time-averaging interval. An equivalent impulse response for the linear envelope detector's lowpass filter is introduced. This allows the prediction of the detector's response to the modulated EMG signal. The results show that stochastic estimation errors may contribute considerably to the observed variability in EAEPs. They also explain how these errors depend on the spectral characteristics of the EMG signal, the design of the lowpass filter in the linear envelope detector and on the time course of a muscle's myoelectric activity.

Application of a dual channel peroneal nerve stimulator in a patient with a "central" drop foot.

Dropped foot is a common mobility problem amongst patients after a cerebro vascular accident. The condition arises from paresis of the muscles that control the foot movement during the swing phase of gait. If the abnormal movement is not compensated for, it results in a significant decrease in the mobility and hence quality of life. Compensation for the drop foot can be achieved through the application of functional electrical stimulation. To date, in the clinical environment, the stimulation has been applied through electrodes placed on the skin over the common peroneal nerve, and using a single channel implant device. It is well known that with these techniques it is difficult to establish a balanced response of the foot. An implantable dual channel system for stimulation of the deep and superficial peroneal nerve has now been developed for patients with a drop foot following a stroke. By stimulation of the two branches of the common peroneal nerve separately it is possible to achieve a precisely balanced dorsal flexion and eversion of the foot. Stimulation occurs via small bipolar electrodes which are placed subepineural. After successful tests on animals we have now started the two channel peroneal nerve stimulator implantation in patients. The preliminary results of the first implants are presented.

Artificial-reflex stimulation for FES-induced standing with minimum quadriceps force.

A control strategy is proposed to decrease quadriceps activity during standing. Modified on/off (or artificial reflex) control is used: a non-numerical or finite-state control scheme based on feedback of knee angle and angular velocity. The control strategy is evaluated in paraplegic patients in an experimental setup using transcutaneous stimulation. The stability of the system and its sensitivity to various control parameters are determined. It is concluded that the control scheme will enable reduction of muscle force independent of additional mechanical bracing or specific posture, and may result in continuous dynamic activation of muscle.

Simultaneous measurement of surface EMG and movements for clinical use.

A system for simultaneous measurement of surface EMG, joint movement and temporal parameters of gait has been developed for clinical use. Some design constraints, imposed by the clinical situation, are indicated. Multiple cycles of movement are recorded and averaged patterns of muscle activation and joint movements are determined. Data processing runs concurrently with data acquisition, so that the results are available for clinical interpretation immediately after the measurement. Instrumentation, signal processing and software are described and some examples of application of the system for evaluation of therapies and functional aids are presented. It is proposed that clinically relevant quantitative information can be obtained by comparison of different recordings of the individual patient rather than comparison with patterns found with normal subjects.

Distribution of psychological aspects in subgroups of chronic low back pain patients divided on the score of physical performance.

This study investigates whether different subgroups of chronic low back pain patients (CLBPs) differ in psychological aspects assessed with the Symptom Checklist (SCL-90) and the Multidimensional Pain Questionnaire (MPI-DLV). Four subgroups of CLBPs are discerned using the results of lumbar dynamometry: 1. Patients with performances lower than healthy subjects (expected performance; n = 45). 2. Patients with performances comparable to healthy subjects (normal performance; n = 18). 3. Patients with inconsistent test behaviour (submaximal performance; n = 6). 4. Patients with performances that could be either maximal or submaximal (gray-zone performance; n = 10). Significant differences in psychological aspects were found between patients with submaximal and patients with expected performances but not between patients with normal and patients with expected performances. All patients with submaximal performance report a high degree of psychological distress, in contrast to 30% of those with normal performance and 20% of those with expected performance. Because of the differences found in psychological aspects between the CLBP subgroups, it is thought that a physical screening together with a psychological screening provides better insight in the two aspects of the deconditioning syndrome and thus can give better treatment indications than a physical screening alone.

Daily hassles and stress vulnerability in patients with a whiplash-associated disorder.

The objectives of this study were to examine the self-reported, daily problems of patients with a whiplash-associated disorder (WAD) and a healthy control group, with the hypothesis that WAD patients would report more person-dependent hassles and perceive them as more serious than the healthy control group, due to the prior experience of a whiplash injury. In addition, it was expected that the person-independent seriousness rating would be elevated, reflecting the increased vulnerability of WAD patients to common stressors. Finally, a strong relationship was expected between frequency or seriousness of daily problems on the one hand and level of distress on the other. Forty-seven WAD patients seeking treatment and 47 matched healthy control participants completed the everyday problem checklist (EPCL). The level of distress was measured by the symptom checklist (SCL-90). As expected, most EPCL-scores in the WAD group were higher than the scores of the healthy participants. Regression analysis further revealed that 61% of the variance in general distress in the WAD group could be explained by EPCL scores and educational background. Chronic WAD patients report a high stress load, which is related specifically to personal functioning after the whiplash injury. In addition, WAD patients (especially those with a low educational level) appear to be more vulnerable and react with more distress than healthy people to all kinds of stressors. Stress responses probably play an important role in the maintenance or deterioration of whiplash-associated complaints.

A low-cost FES exercise bicycle for training paraplegics at home.

The success of FES exercise programmes for training paraplegic muscles at home depends highly upon the availability of reliable, easy-to-use and inexpensive training equipment. For endurance training, FES bicycle exercisers are well accepted. However, they are not suited for home use due to the high expense of commercially available equipment. This paper describes the development of a FES exercise bicycle for use at home. It consists of a standard bicycle ergometer with minimum modifications. The exerciser can be used by the patient sitting in the wheelchair, and may be used with any two-channel muscle stimulator.

A new gait analysis system for clinical use in a rehabilitation center.

A semi-portable system based on a microcomputer has been developed to measure the vertical reaction forces on both feet during walking. Eight capacitive force transducers are attached to each sole of the patients' shoes. This allowed the forces to be measured for several consecutive steps during a walk of 20 sec. This article describes the principles of operation of the force transducers and the associated electronic system. It also shows data processing procedures and gives a review of the available methods of data presentation. Recordings of the walking pattern of three patients with different diagnostics are presented and discussed to demonstrate the usefulness of the new gait analysis system in a rehabilitation center.

The influence of the reciprocal hip joint link in the Advanced Reciprocating Gait Orthosis on standing performance in paraplegia.

The effect of reciprocally linking the hip hinges of a hip-knee-ankle-foot orthosis on standing performance was studied in a comparative trial of the Advanced Reciprocating Gait Orthosis (ARGO) and an ARGO in which the Bowden cable was removed (A_GO). Six male subjects with spinal cord injury (SCI) at T4 to T12 level participated in the study, which was conducted using a single case experimental design. Standing balance, the ability to handle balance disturbances (standing stability), and the performance of a functional hand task during standing were assessed in both orthosis configurations in the order A_GO-ARGO-A_GO-ARGO. No significant differences with respect to standing performance were found for the two orthosis configurations. However, the results indicate that the crutch force needed for maintaining balance during various tasks, especially for quiet standing with two crutches, may be much higher in the orthosis without Bowden cable. Therefore, it is very likely that the reciprocal hip joint link in the ARGO provides a substantial and clinically relevant reduction of upper body effort required for standing under functional conditions.

The influence of the reciprocal cable linkage in the advanced reciprocating gait orthosis on paraplegic gait performance.

A wide variety of mechanical orthoses is available to provide ambulation to paraplegic patients. Evaluation of energy cost during walking in each of these devices has been acknowledged as an important topic in this field of research. In order to investigate the benefits of a ballistic swing on gait performance in the Advanced Reciprocating Gait Orthosis (ARGO) a study was conducted in which the ARGO was compared with an orthosis with freely swinging legs. This Non Reciprocally linked Orthosis (NRO) was obtained by removing the reciprocal linkage in the subjects' own ARGOs. Subsequently, flexion/extension limits were mounted to permit adjustment of stride length. Six male paraplegic subjects with lesions ranging from T4 to T12 were included in the study. A single case experimental design (B-A-B-A) was conducted in order to improve internal validity. Biomechanical and physiological parameters were assessed and the subjects' preference for either ARGO or NRO was determined. It was found that large inter-individual differences produced insufficient evidence in this study to draw general conclusions about difference in energy expenditure between both orthoses. However, individual analysis of the results showed a reduction of oxygen cost (range: 4%-14%) in the NRO in T9 and T12 lesions, while oxygen cost in subjects with T4 lesions increased markedly (22% and 40%). It is concluded that patients with low level lesions could benefit in terms of oxygen lost from removing the reciprocal cable linkage in the ARGO. However, only one subject preferred the NRO for walking, whereas none of the subject chose the NRO for use in daily living activities. Removal of the reciprocal cable linkage in the ARGO may not be desirable for these patients.

Comparative trials on hybrid walking systems for people with paraplegia: an analysis of study methodology.

A new orthosis (SEPRIX) which combines user friendliness with low energy cost of walking has been developed and will be subject to a clinical comparison with conventional hip-knee-ankle-foot orthoses. In designing such comparative trials it was considered it may be worthwhile to use previous clinical studies as practical examples. A literature search was conducted in order to select all comparative trials which have studied two walking systems (hip-knee-ankle-foot orthoses) for patients with a complete thoracic lesion. Study population, intervention, study design, outcome measurement and statistical analyses were examined. Statistical power was calculated where possible. Of 12 selected studies, 7 were simple A-B comparisons, 2 A-B comparisons with a replication, 2 cross-over trials and 1 nonrandomised parallel group design, the last of which was considered internally invalid due to severe confounding by indication. All A-B comparisons were considered internally invalid as well, since they have not taken into account that a comparison of two orthoses requires a control for aspecific effects (like test effects) which may cause a difference. Statistical power could only be examined in 4 studies and the highest statistical power achieved in one study was 47%. It is concluded that statistical power was too low to be able to detect differences. Even analysis through interval estimation showed that the estimation of the difference was too imprecise to be useful. Since the majority of the surveyed papers have reported small studies (of only 4-6 patients), it is assumed that lack of statistical power is a more general problem. Three possibilities are discussed in order to enhance statistical power in comparative trials, i.e. multicentre studies, statistical pooling of results and improving the efficiency of study design by means of interrupted time series designs.