Profile of osteoarticular tuberculosis in children.

OBJECTIVE: To determine clinical profile of osteoarticular tuberculosis (TB) in children. METHODS: Cross-sectional analysis from 2007 to 2013. All patients diagnosed with bone TB, spinal TB or TB abscesses were included. RESULTS: Out of 1318 children with TB, 39 (2.96%) had osteoarticular TB, of which 16 (42%) had osteomyelitis, 8 (20.5%) had spinal involvement, 7 (17.9%) had TB synovitis, 2 (5.1%) had psoas abscess and 6 (15.4%) had abscesses. The mean age of presentation was 7.1 ± 3.5 years (range 2-14 years). Of the 33 cases in which a culture was done, 25 (64%) showed a positive culture. Drug sensitivity tests were done in 21 patients of which 10 (47.6%) tested were drug resistant, of which 4 (36.4%) were multidrug resistant (MDR), 2 (18.2%) were extensively drug resistant (XDR), 3 were pre-XDR (27.3%) and 1 was polyresistant (9.1%). Nine (23.1%) patients had TB in the past with a treatment duration of 8.3 ± 5.3 months. Contact with a TB patient had occurred in 10 (25.6%) cases. Associated pulmonary TB were seen in 6 (15.39%) and TB meningitis were seen in 1 (2.6%) patients. Surgical intervention was needed in 11 (28.2%) patients of which 5 (45.5%) underwent curettage, drainage was done in 1 (9.1%), arthrotomy in 4 (36.4%) and spinal surgery in 1 (9.1%) patient. CONCLUSION: Drug resistant osteoarticular TB is an emerging problem in children.

Functional hindrance due to spasticity in individuals with spinal cord injury during inpatient rehabilitation and 1 year thereafter.

STUDY DESIGN: Prospective cohort study. OBJECTIVE: To assess functional hindrance due to spasticity during inpatient rehabilitation and 1 year thereafter in individuals with spinal cord injury (SCI) and to determine factors that influence the hindrance. SETTING: Eight specialized rehabilitation centres in the Netherlands. METHODS: A total of 203 patients with recent SCI rated the hindrance they perceived due to spasticity in daily living at the start of active rehabilitation (t1), 3 months later (t2), at discharge (t3) and 1 year after discharge (t4). Hindrance was dichotomized into absent or negligible and present. Multilevel regression analyses were performed to determine the course of functional hindrance due to spasticity and its associations with possible determinants-namely, age, gender, cause, lesion level, motor completeness, spasticity and anti-spasticity medication. RESULTS: The percentage of individuals that indicated functional hindrance due to spasticity ranged from 54 to 62% over time and did not change significantly over time (Δt3t1 odds ratio (OR)=0.85, P=0.44; Δt3t2 OR=1.20, P=0.41; Δt3t4 OR=0.91, P=0.67). The percentage of individuals who experienced a lot of hindrance due to spasticity during specific activities ranged from 4 to 27%. The odds for experiencing functional hindrance due to spasticity were significantly higher for individuals with tetraplegia (OR=2.17, P=0.0001), more severe spasticity (OR=5.51, P<0.0001) and for those using anti-spasticity medication (OR=4.18, P<0.0001). CONCLUSION: Functional hindrance due to spasticity occurred in the majority of persons with SCI and did not change significantly during inpatient rehabilitation and 1 year thereafter. Factors that influence hindrance were determined.

Arm hand skilled performance in persons with a cervical spinal cord injury--long-term follow-up.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To assess development of arm hand skilled performance (AHSP) during and after in-patient rehabilitation in persons with cervical spinal cord injury (CSCI) and to determine factors that influence the outcome. SETTING: Eight rehabilitation centres in the Netherlands with specialised spinal cord injury departments. METHODS: AHSP was assessed using the Van Lieshout test (VLT) in persons admitted with recent CSCI. Assessment was carried out at the beginning (t1), after 3 months (t2), at the end (t3) of in-patient rehabilitation, and 1 and 5 years thereafter (t4, t5). Multilevel regression analysis was performed to determine development of AHSP and associations between AHSP and age, gender, motor completeness, lesion level (high or low CSCI), motor scores of upper extremity (MSUE), and pain in the tested arm. RESULTS: Fifty-five participants were included with mean age 38 years (range 18­64). There were 73% male, 80% had high CSCI (C3­C6) and 69% had motor complete lesion. Scores of VLT improved significantly during in-patient rehabilitation (mean: t1=25; t3=33) (P=0.005), scores remained unchanged at 1 year (t4=32) and 5 years (t5=32) (P=0.903) after in-patient rehabilitation. Motor completeness, MSUE and pain were significantly related to the VLT score (P<0.001, P<0.001, P=0.015, respectively). Age, gender and lesion level had no significant relationship. CONCLUSION: AHSP improved during in-patient rehabilitation. It was then stable during the next 5 years after discharge. Persons with an incomplete lesion, high MSUE and no pain in the tested arm perform best on the VLT.

Kinematic coupling relationships exist between non-adjacent segments of the foot and ankle of healthy subjects.

Pathologies of foot and ankle structures affect the kinematics at the site of the impaired structure but also influence kinematics elsewhere in the foot and ankle. An understanding of kinematic coupling relationships in the foot could provide insight into mechanisms that explain differences in foot and ankle kinematics between healthy and pathological subjects. The aim of this study was to explore foot and ankle kinematic coupling relationships between adjacent and non-adjacent segments of healthy subjects and evaluate individual variability of and effect of walking speed on these relationships. Gait of 14 subjects was recorded at comfortable and two slower walking speeds to assess individual foot kinematics during stance phase. A qualitative evaluation of the coupling relationships was made using angle-angle plots to determine their consistency, i.e. changes in movement direction of each segment occurred at the same time and the plot returned along the same line after the turning point. The Pearson correlation coefficient of determination (R(2)) was used to provide a quantitative evaluation of coupling. Individual variability was assessed with the coefficient of variation (CV). The Friedman-test was used to test the effect of walking speed. Consistent coupling relationships were observed between hindfoot in/eversion and hallux plantar/dorsiflexion (R(2) 0.7, CV 0.2), between hindfoot in/eversion and forefoot ab/adduction (R(2) 0.5, CV 0.3) and between leg rotation and midfoot collapse/elevation (R(2) 0.5, CV 0.4). Less or non-consistent coupling relationships were observed between the other studied segments. Walking speed significantly influenced coupling relationships between hindfoot and midfoot.

Foot and ankle kinematics in rheumatoid arthritis: influence of foot and ankle joint and leg tendon pathologies.

OBJECTIVE: From early onset of the disease, patients with rheumatoid arthritis (RA) experience walking impairments. Pathologic effects of RA on foot and ankle structures have been studied clinically, but little is known as to how they relate to kinematic changes during gait. The aim of this study was to explore the relationship between clinically observed pathologies of foot and ankle joints and leg tendons and the corresponding gait kinematics. METHODS: The gait of 25 subjects with varying stages of RA was recorded and foot and ankle kinematics were assessed. Magnetic resonance imaging was performed for each subject: first metatarsophalangeal (MTP) joint, midfoot, and hindfoot synovitis, erosion scores, and leg tendon involvement were determined. The joint alignment and motion score represented daily clinical assessment. The 95% confidence intervals of the Spearman's correlation coefficient tests were used to explore the relationships between the clinical and kinematic parameters. RESULTS: Maximum first MTP joint dorsiflexion at preswing was related to reduced first MTP joint passive motion, first MTP joint synovitis and erosion, midfoot synovitis and erosion, and hindfoot erosion. Midfoot pronation range of motion during single stance was related to subtalar alignment and Achilles tendon involvement. Hindfoot eversion range of motion during single stance was related to subtalar alignment and peroneus longus tendon involvement. Involvement of the tibialis posterior tendon could not be identified as an independent factor influencing foot or ankle kinematics. CONCLUSION: Our findings suggest moderate to strong relationships between foot and ankle gait kinematics and structural pathologies.

Long-term patient satisfaction after reconstructive upper extremity surgery to improve arm-hand function in tetraplegia.

STUDY DESIGN: There is a paucity of literature about satisfaction after reconstructive surgery to improve upper limb function in persons with tetraplegia. The present literature describes mainly functional outcomes. OBJECTIVES: To evaluate long-term satisfaction after reconstructive upper extremity surgery in persons with tetraplegia. SETTING: Two rehabilitation centers in the Netherlands. METHOD: A three-part questionnaire consisting questions regarding satisfaction, activities, occupation, changes in functional ability and willingness to undergo the surgeries again was used. Internal reliability of the questionnaire was verified by factor analysis and calculation of Cronbach's alpha. RESULTS: In total, 39 out of 55 persons (70.9%) participated in the study. The participants' responses to questions about satisfaction, activities and occupation were positive in 73.5, 67.6 and 35.0%, respectively. Nearly 81% improved their functional ability. Approximately 65% of the participants were willing to undergo elbow extension surgery again and 77.1% expressed their willingness to undergo hand/wrist surgery again. Significant positive correlation was found between willingness to have surgery again and improvement in activities and occupation: Spearman's correlation coefficients: activities-elbow extension 0.63 (P=0.003), activities-hand/wrist 0.57 (P<0.001), occupation-elbow extension 0.53 (P=0.025), occupation-hand/wrist 0.57 (P=0.001). Differences between the subgroups who would have surgery again and those who would refrain were also significant; one-way analysis of variance for activities (F=9.54, P<0.01) and for occupation (F=6.60, P<0.02). CONCLUSION: In the Netherlands, the majority of persons with tetraplegia who underwent reconstructive upper extremity surgery were satisfied with the results. This was related to improvement in activities and occupation.

Foot and ankle joint kinematics in rheumatoid arthritis cannot only be explained by alteration in walking speed.

Rheumatoid arthritis (RA) manifests itself in the foot and ankle of RA patients. The foot and ankle joint kinematics of these patients differ from that of healthy subjects. However, the factors that lead to these differences are not yet fully understood. The aim of this study was to analyse the effect of walking speed and the disease process on foot and ankle joint kinematics of RA subjects. Gait recordings of 23 RA and 14 age-matched healthy subjects were performed and their foot and ankle joint kinematics were analysed during the stance phase of the gait cycle. Stance phase characteristics of the group of RA subjects and of the group of healthy subjects were compared. The healthy subjects walked at 100% (Vc), 75% (V75) and 50% (V50) of their comfortable walking speed. In a multi-level linear model significant differences between the two groups due to the factors walking speed and the disease process were analysed. The ankle dorsi-flexion, medial arch and hallux abduction motion at single-stance and toe-off were only influenced by the walking speed. The hallux maximum flexion at toe-off and the midfoot supination at single-stance were influenced by both the walking speed and the disease process. The hindfoot eversion motion at single-stance was only influenced by the disease process. In conclusion, the reduction of walking speed of RA subjects compared to healthy subjects does not explain all of the observed foot and ankle kinematics differences.

The effects of walking speed on forefoot, hindfoot and ankle joint motion.

BACKGROUND: Foot and ankle joint kinematic differences have been identified between healthy subjects and subjects with various pathologies suffering from foot and ankle impairments. Changes in temporal factors such as walking speed and double stance time are also found in these pathological conditions. As such, in theory, these factors would also influence the kinematics and hence make it difficult to ascertain the effects of the disease on the kinematics. The aim of this study was to analyse foot and ankle kinematics from gait recordings of healthy subjects walking at comfortable and slower speeds. METHODS: Gait patterns of 14 healthy subjects were recorded. The subjects were first asked to walk at a comfortable speed and then at predefined speeds of 75% and 50% of their comfortable walking speed respectively. Temporal variables were calculated. Foot and ankle joint kinematics were determined from marker-recordings. FINDINGS: The subjects walked at mean velocities of 1.28 m/s, 0.97 m/s and 0.65 m/s. With decreasing walking speed the minimum tibio-talar plantar-flexion and maximum hallux dorsi-flexion at toe-off decreased significantly between 3 degrees and 9 degrees. The minimum medial arch at toe-off and minimum midfoot supination at mid-stance were significantly affected by the walking speed. The corresponding individual session differences were small (1 degrees -2 degrees), but the reliability was high and hence the differences were considered clinically relevant. INTERPRETATION: Walking speed significantly affected foot and ankle kinematics. Studies aiming to improve the understanding of the effects of foot and ankle pathologies on foot and ankle kinematics should take the walking speed into account.

Stop using the Ashworth Scale for the assessment of spasticity.

AIM: Many studies have been performed on the methodological qualities of the (modified) Ashworth Scale but overall these studies seem inconclusive. The aim of this study was to investigate the construct validity and inter-rater reliability of the Ashworth Scale (AS) for the assessment of spasticity in the upper and lower extremities. METHOD: A cross-sectional study on spasticity in the elbow flexors (part 1) and knee extensors (part 2) was carried out. In both parts AS was assessed while muscle activity and resistance were recorded simultaneously in patients with upper motor neuron syndrome. Each patient was measured by three raters. RESULTS: 30 patients participated, 19 in each part of the study. For elbow flexor muscles, AS was not significantly associated with electromyographic parameters, except for rater 2 (rho = 0.66, p<0.01). A significant moderate association was found with resistance (0.54< or = rho < or =0.61, p<0.05). For knee extensors, AS scores were moderately associated with muscle activity (0.56< or = rho < or =0.66, p<0.05) and also with resistance (0.55< or = rho < or =0.87, p<0.05). The intraclass correlation coefficient for absolute agreement was 0.58 for elbow flexors and 0.63 for knee extensors. In linear mixed model analysis, the factor rater appeared to be highly associated with AS. CONCLUSION: The validity and reliability of the AS is insufficient to be used as a measure of spasticity.

Perception of lower limb spasticity in patients with spinal cord injury.

STUDY DESIGN: Cross-sectional study. OBJECTIVE: To study the manifestation of spasticity in daily life of the patients with spinal cord injury, their perception of spasticity and spasticity-related discomfort. SETTING: Rehabilitation center in the Netherlands. METHODS: Twenty-six patients with motor complete spinal cord injury (SCI) and spasticity in the lower limbs completed a questionnaire. The following outcome measures were used: manifestation of spasticity, activities during which spasticity occurs, perceived degree of spasticity and resulting discomfort, measured with visual analog scale (VAS) and Borg scale, respectively. RESULTS: In general, spasticity manifested as extensor spasms (84.6%), flexor spasms and/or clonus (both 69.2%), and less often as continuous tension (57.7%). The registered activities were categorized into five main groups: 'changing position' was the largest group (22.0%) with a median VAS of 6.8 (range: 2.5-9.5) and median Borg scale of 3.0 (range: 1.0-7.0). Other groups of activities were 'making a transfer' (20.7%), 'activities of daily living' (17.1%), 'being active' (17.1%) and 'stable body position' (12.2%). The overall correlation between VAS and Borg was moderate (Spearman's rho=0.53, P=0.005). CONCLUSIONS: Patients with complete SCI experienced several manifestations of spasticity, extensor spasms being the most common. Many daily life activities elicited different manifestations of spasticity. The experienced discomfort was only moderately related to the perceived degree of spasticity during an activity. Possibly, the discomfort is influenced by other factors than the perceived spasticity alone.

Measuring change in arm hand skilled performance in persons with a cervical spinal cord injury: responsiveness of the Van Lieshout Test.

OBJECTIVES: To asses whether the Van Lieshout Test (VLT) is responsive to measure changes in arm hand skilled performance (AHSP) over time during active rehabilitation in persons with cervical spinal cord injury (C-SCI) and in different subgroups of persons with C-SCI according to lesion completeness and to lesion level. STUDY DESIGN: Longitudinal cohort study. SETTING: Spinal Cord Injury Units in eight rehabilitation centres across the Netherlands. METHODS: In the present study, data from a national SCI cohort study are used. Data from the VLT, the Grasp Release Test (GRT), the Functional Independence Measure (FIM) and the Quadriplegia Index of Function (QIF) were recorded at three moments during active rehabilitation: at the start of active rehabilitation (t1), 3 months after t1 (t2) and at discharge (t3). Data have been analysed using three responsiveness measures, that is, the standardized response mean, the effect size and comparison of test scores measured at different times. RESULTS: The VLT is responsive for the intervals t1-3, t1-2 and t2-3. The VLT can be used to measure changes in AHSP in persons with a C-SCI with an American Spinal Injury Association Impairment Scale (AIS) A or B score or an AIS C or D score, as well as in persons with a C3-C6 lesion or a C7-T1 lesion. The responsiveness of the VLT is significantly correlated to the GRT, but not to the FIM and the QIF. CONCLUSION: The VLT is responsive in measuring changes in AHSP during rehabilitation in persons with C-SCI.

Demographics of the Dutch multicenter prospective cohort study 'Restoration of mobility in spinal cord injury rehabilitation'.

STUDY DESIGN: A multicenter prospective cohort study. OBJECTIVE: To compare the demographic data of the included population with other studied spinal cord injury (SCI) populations in the international literature. SETTING: Eight Dutch rehabilitation centers with a specialized SCI unit. METHODS: A total of 205 individuals with SCI participated in this study. Information about personal, lesion and rehabilitation characteristics were collected at the beginning of active rehabilitation by means of a questionnaire. RESULTS: The research group mainly consisted of men (74%), of individuals with a paraplegia (59%), and had a complete lesion (68%). The SCI was mainly caused by a trauma (75%), principally due to a traffic accident (42%). The length of clinical rehabilitation varied between 2 months and more than a year, which seemed to be dependent on the lesion characteristics and related comorbidity. CONCLUSIONS: The personal and lesion characteristics of the subjects of the multi-center study were comparable to data of other studies, although fewer older subjects and subjects with an incomplete lesion were included due to the inclusion criteria 'age' and 'wheelchair-dependent'. The length of stay in rehabilitation centers in The Netherlands was longer compared to Denmark but much longer than in eg Australia and the USA.

The effect of walking aids on muscle activation patterns during walking in stroke patients.

The purpose of this study was to investigate changes in muscle activation patterns with respect to timing and amplitude that occur when subjects with stroke walk with and without a walking aid. This knowledge could help therapists in deciding whether or not patients should use a cane or quad stick while walking. Thirteen patients suffering from a first unilateral ischemic stroke participated in the study. Surface electromyography (SEMG) of the erector spinae, gluteus maximus, gluteus medius, vastus lateralis, semitendinosus, gastrocnemius and tibialis anterior of the affected side were measured during three different conditions: (1) walking without a walking aid, (2) walking with a cane and (3) walking with a quad stick. Timing and amplitude parameters of the activation patterns were quantified using an objective burst detection algorithm and statistically evaluated. Results showed a statistically significant and clinically relevant decrease in burst duration of both erector spinae and tibialis anterior when walking with a cane. The amplitude of the vastus lateralis and tibialis anterior dropped when patients walked with a cane and quad stick. The use of a cane should be considered when therapy is given to stroke patients to achieve normal muscle activation patterns.

Rectus femoris surface myoelectric signal cross-talk during static contractions.

The clinical application of EMG requires that the recorded signal is representative of the muscle of interest and is not contaminated with signals from adjacent muscles. Some authors report that surface EMG is not suitable for obtaining information on a single muscle but rather reflects muscle group function [J. Perry, C.S. Easterday, D.J. Antonelli, Surface versus intramuscular electrodes for electromyography of superficial and deep muscles. Physical Therapy 61 (1981) 7-15]. Other authors report however, that surface EMG is adequate to determine individual muscle function, once guidelines pertaining to data acquisition are followed [D.A. Winter, A.J. Fuglevand, S.E. Archer. Cross-talk in surface electromyography: theoretical and practical estimates. Journal of Electromyography and Kinesiology 4 (1994) 15-26]. The aim of this study was to determine whether surface EMG was suitable for monitoring rectus femoris (RF) activity during static contractions. Five healthy subjects, having given written informed consent, participated in this trial. Surface and fine wire EMG from the rectus femoris and the vastus lateralis (VL) muscles were recorded simultaneously during a protocol of static contractions consisting of knee extensions and hip flexions. Ratios were used to quantify the relationship between the surface EMG amplitude value and the fine wire EMG amplitude value for the same contraction. The results showed that hip flexion contractions elicited RF activation only and that knee extension contractions elicited fine wire activity in VL only. When the relationship between RF surface and RF fine wire electrodes was compared for hip flexion and knee extension contractions, it was observed that for all subjects, there was a tendency for increased RF surface activity in the absence of RF fine wire activity during knee extensions. It was concluded that the activity recorded by the RF surface electrode arrangement during knee extension consisted of EMG from the vastii, i.e., cross-talk and that vastus intermedius was the most likely origin of the erroneous signal. Therefore it is concluded that for accurate EMG information from RF, fine wire electrodes are necessary during a range of static contractions.

Is rectus femoris really a part of quadriceps? Assessment of rectus femoris function during gait in able-bodied adults.

There is conflicting evidence as to the precise activation pattern of the rectus femoris (RF) muscle during gait in able-bodied subjects. The aim of this study was to determine precise activation pattern of RF during gait in a healthy adult population. Surface and fine wire EMG from RF and vastus lateralis (VL) were recorded simultaneously at different walking speeds in five able-bodied subjects. The results of fine wire EMG showed that, at normal walking speed, RF was active only during the stance-to-swing transition. At faster speeds, increased levels of RF activity were seen during the same transition period. At the fastest speed, there was some activity during terminal stance, in addition to that at stance-to-swing transition, that could be attributed to rapid hip extension and thereby a rapid stretch of RF. However, the RF surface EMG signal was found to exhibit a bi-phasic pattern whilst walking at all different self-selected speeds. A burst of EMG activity recorded at initial contact on the surface signal but not on fine wire EMG, was due to cross-talk from vastus intermedius (VI). A close similarity was observed between the surface EMG patterns of VL and RF. VL surface and fine wire EMG profiles were identical for all the self-selected speeds with a main peak of activity beginning in terminal swing and ceasing in mid-stance. We conclude that RF is active only during stance-to-swing transition and the activity during swing-to-stance transition, as described in the literature, is very probably due to cross-talk.

A feasibility study of remote consultation to determine suitability for surgery in stroke rehabilitation.

We studied knowledge transfer for the determination of the suitability of stroke patients for a specialist surgical procedure (split anterior tibial tendon transfer). Gait analysis data from patients at a general hospital were discussed with an expert in another country using personal computers, an ISDN connection (128 kbit/s) and TCP/IP-based communication tools. The key issue was whether the staff in the general hospital became better able to determine suitability for surgery. Twelve patients were studied. In three of the first four cases the advice of the remote expert changed the plan for surgery. After that the treatment plans did not change after consultation. After eight cases the local clinicians did not need to ask for further advice. There was a rapid increase in skill in determining suitability for surgery. The experience and skills of the local clinicians were thought to increase more rapidly than would have been the case without the consultations with a remote expert.

Lumbar and lumbosacral tuberculous spondylodiscitis in adults. Redefining the indications for surgery.

We have reviewed, retrospectively, 66 adult patients who were treated for lumbar or lumbosacral tuberculosis. A total of 45 had a paravertebral or epidural abscess, 24 had clinical instability and 18 presented with a radiculopathy, of which six also had a motor deficit. The diagnosis was usually made on clinical and radiological grounds and they were followed up until there were clinical and radiological signs of full recovery. Conservative treatment with antituberculous drugs was successful in 55 patients (83%). None had persistent instability, radiculopathy or neurological compromise. We feel that tuberculous spondylodiscitis, especially in the lumbar spine, can usually be satisfactorily managed conservatively and that there are few indications for surgical treatment.

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.

Biomechatronics--assisting the impaired motor system.

Biomechatronics concerns the interdisciplinary field of interaction with the human neuromuscular-skeletal system with the objective to assist impaired human motor control. In this field technology is developed that integrates neuroscience, robotics, interface and sensor technology, dynamic systems and control theory. The primary issue in this field concerns the concepts of assisting impaired human motor function. The secondary, derived, issue concerns possible methods of interfacing with the human body at all hierarchical levels of the human motor system. The application of motor assist systems may serve several goals: it can take over part of the affected motor control, enable the physiological motor system to perform the desired function or aid in training the impaired physiological system. The progress in these issues are reviewed and their potential implications for assistance of the impaired human motor system are discussed.

Assessment of rectus femoris function during initial swing phase.

The normal human gait cycle is divided into two phases, namely, stance and swing. The objective of stance is to provide support, stability and propulsion and that of swing is to provide ground clearance and limb advancement. Knee flexion is essential during swing to lift the foot off the ground for limb advancement. The complex mechanisms involved in producing limb advancement can produce excessive knee flexion at faster walking speeds. Under these circumstances the shank needs to be decelerated to reduce the amount of knee flexion. It is assumed that rectus femoris (RF) is active for a very short period at the beginning of the swing phase (Perry J. Gait Analysis-Normal and Pathological Gait. Slack Incorporated, USA, 1992; Scott L, Ringwelsky D, Carroll N. Transfer of rectus femoris: effects of transfer site on moment arms about the knee and hip. J Biomech 27;1994:1201-1211) and the amount of this activation is proportional to the walking speed and thus to the generated knee moment and the angular acceleration of the lower limb segments. However, there is very little evidence to support these assumptions. The objective of this study was to study this relationship. Quantified electromyogram of RF and vastus lateralis (VL), using surface electrodes, were examined, body mounted kinematic sensors such as seismic accelerometers and gyroscopes were used to measure segments' angular accelerations and the net muscular knee torque calculated from the kinematics of the segments at various speeds. The results showed that RF and VL work independent of each other during the initial swing phase. The amount of RF activity is clearly related to walking speed. The muscle activity increases with increasing walking speed. The relationship between the angular acceleration of the shank and the amount of RF activity is linear. The active knee moment, as a function of the shank's angular acceleration, shows the same high correlation to the EMG signal of RF.