- Email: [email protected]
Variation ratio: A new approach to assess changes in leg muscle EMG pattern
Abstracts possible. The subjects are thus constrained to walk in a reasonably energy efficient pattern. Subjects with L5 lesions have functioning abductors and are not subject to this constraint. and exhibit a variety &gait patterns, some of which do not minimise energy consumption. Thus as a group the mean energy expenditure is higher than in the L4 group. It is not clear why they adopt such patterns but they may be more comfortable or cosmetic. I f this is conjecture is correct then lower variability in the excursion of the CM might be expected in the L4 group than the L5 group. Figure 2 shows the standard deviations for the four groups confirming that this is the case. This is also observed in Duffy's oxygen cost data.
References Dully CM et al. (1996). Dev Med Child NeuroL 38:238-243 Saunders JBDM et al (t953) J Bone It Surg. 35A: 543-588 Jensen RK (1986) J Biomechanics. 19: 359-368. Eames MI-IA et al (1999) Hum Mov Sci. [in press] Duffy CM et al (1996b) Gait and Posture 4:34-38
77
were small and probably virtually indiscernible to the human eye. they implied that PD subjects had lost the rotatory component of their trunk while rising. It was not anticipated that large amount of trunk lateral flexion would be observed during STS in normal subjects. However, an impaired motor control system probably caused a larger range of lateral inclination in PD patients that would be an important feature to monitor Although Increased flexion of the trunk during STS seen in PD can be a potential threat to their balance, it could be a strategy helping them to eliminate or shorten the unstable phase by center of mass repositioning The pattern of internal bending of the trunk in frontal plane can be another compensatory mechanism in order to keep the body center of mass within the base of support to sustain the uptight balance at the termination of the task. It is hoped that during rehabilitation , the successful use of strategies aiming to increase the total range o f trunk axial rotation improve mobility of the trunk, which lead to functional improvements including ease of standing and walking.
References: l)Alexander NB, Schultz AB. Rising from a chair. Effects of age and functional ability, on performance biomechanics. J Gerontology 1991:46:M91-8 2)Lakke JPWF. Axial apraxia in Parkiuson's disease. J Neurological Sciences 1985;69:37-46
KINEMATICS ANALYSIS OF THE TRUNK MOTION DURING SIT TO STAND iN PARK1NSON' S DISEASE Dr ENikfekr*, Dr D. Playford,* Mr S. Attfield** * Rehabilitation Research Unit, Division of rehabilitation and ageing, Queen's Medical Center, University of Nnttingham ** Bioengineering Research Center, Derby Acute Hospitals NHS Trust.
K I N E M A T I C AND E L E C T R O M Y O G R A P H I C O U T C O M E AFTER B3A-ROTATIONPLASTY
IN PATIENTS
D. Rosenbaum, A. Hillmann, W. Winkelmanu Funktiousbereich Bcwegungsanalytik, Orthop~idische Klinik, Universit~it Miinster
Introduction: Parkinson's disease (PD) is a common neurological disorder which causes falls, difficulty with walking and standing from a seated position, arising from a combination of direct effects of the disease ( ie. bradykinesia, rigidity and pastural inflexibility) and indirect (e.g fixed flexed posture and pelvis and trunk immobility). Getting out of a chair is considered one of the most important functions which is a particularly difficult manoeuvre for patients with Parkinson's disease. There is considerable information available about lower limbs kinematics and kinetics during sit to stand (STS), but little is known about trunk control during this task. This study aimed to provide insights for both the analysis of performance deficits in PD patients and in the developments of specific rehabilitation programs. The main objective was to ascertain how the trunk kinematics parameters differ from normal subjects Once the pattern of movement has been identified we can define the impact of medical (L-dopa) and physiotherapy on the trunk movement and function. Methodology: Four PD patients and five healthy age matched control subjects studied in the gait laboratory at the Derbyshire Royal Infirmery. Instrumentation consisted of a six camera Elite motion analysis system ( B T S . Bioengineering Technology System, Milan, Italy) which tracked 9 retrureflective markers at 100 frames per second. Markers placed on the left and right acrumion process for shoulder movement and along the spine at the following levels C7, T3, T6, T9, TI2, L3 and sacrum. Subjects were then asked to sit on a height adjusted stall within the calibrated volume of the gait analysis system and ask to stand. Then l) angular displacement of the trunk relative to room-coordinate system in the sagittaI, frontal and transverse planes; 2) vertical and lateral linear displacement of the trunk levels; 3) angular displacement of upper segment relative to lower segment of the trunk in sagittal and frontal plane, were calculated using inhouse programmed algorithms and exported into Excel. The mean of the ten data sets was then produced.
Results: The mean total range of motion observed in PD patients in transverse plane (11 ±0.2 degrees) was less than that observed in normal (3.7-*0.5 degrees) (unpaired t-test, p<0.001). During performing the task~ the normal subjects had a tendency to demonstrate a shredder rotation to the tight (external rotation), in contrast to the patiems whose shoulder mean position was only minimally rotated externally. The total mean range of motion in frontal plane calculated for normal trunk (2.2~:0.3 degrees) was significantly less (P<0.001) than the mean value measured in PD (4.85:0.3 degrees). Further analysis showed that also there was a remarkable difference with regard to upper and lower trunk segments between normal and PD groups. Both inclined with larger ranges of motion in PD than in normal. Measurement of lateral flexion of upper trunk segment relative to lower in PD indicated that the former inclined lateralIy Iess than the latter. This means that in the frontal identical In terms of sagittal _plane movement , the difference between mean trunk range of motion in PD (36.I±1 Idegrees) and normal (30.4-*l.5degrees) was highly significant (P<0.001). The present data suggested that there was less flexion in upper segment than the lower one in normal group. In the contrary , such a difference between two segments in PD was not significant.
Discussion: This study investigated sit to stand cycle in Parkinson's disease patients. The activity was examined under conditions as near normal as possible with few restraining condition Overall, it can be concluded that while the trunk in PD in sagittal and frontal Trunkrotationin TransverseplaneduringSTS
2t
Average lateral shift of trun k levels
t25.
INTRODUCTION Rotationplasty is a limb-salvage treatment modality for malignant bone tumours in children and adults. For different tumour localisations various modifications have been described (1,2). In those cases requiring a total resection of the femur (type BIIIa according to Winkelmann, 1996) the tibia is rotated by 180 ° and the lateral condyle is attached to the acetabular cup If this surgical technique is performed in young children the tibia is expected to develop a "femoral" head due to the loading situation. The result is a shortened leg that can be adapted to a conventional foot prosthesis with a customised shaft for the rotated foot. In the present study we investigated the gait and muscular function of these patients. METHODS Four patients (out of a total of 7 operated in our department) were seen in our Movement Analysis Lab between 4 and 7 years postoperatively. The patients (3 girls, 1 boy, 9 to 12 years old) walked along a 10 m long walkway at a self-salected comfortable speed. Kinematic and kinetic analyses were performed with a four camera MOTION ANALYSIS system and two strain-gage force plates. Surface EMG (NORAXON MYO 2000) was collected bilaterally from the hip muscles and from the thigh and shank muscles of the healthy and operated limb, respectively. RESULTS & DISCUSSION In general, a good gait function with normal gait velocity and stride length as well as a normal phase-related muscle activity (Fig. 1) could be observed. However, the trunk movement indicated a more or less pronounced Duchenne limping on the operated side and a certain weakness of the hip stabilising muscles that can be attributed to the surgical intervention (Tab. 1). Hip and knee range of motion were slightly reduced. Ground reaction force curves indicated a reduced loading and unloading during the stance phase. M R / i m a g e s revealed that the function depended on the extent of muscle resection that was oncologieally necessary as well as the training level of the remaining muscles X-rays revealed that the tibia had adapted to the altered loading conditions by developing a condyle which fit into the acetabular cup. CONCLUSION The results underline the general observation of a good functional restoration aider this type of rotationplasty. Even though the surgically unavoidable loss of stabilising muscles can be seen in the gait patterns the overall outcome and the demonstrated activity level of the patients underline the high degree of subjective satisfactiou of the patients.
Fig. 1: Comparison of thigh (healthy) and shank muscle (rotated limb) EMG patterns. 3o I
isoL Soleus
Rectus femoris
aO; ua
1~0~%.Gastrocnemius lateralia
during STS
as~
Ioo|Semitendinosus -,e!
" 0
20
40
60
S0
Persentageof STS cycle (%)
100
~o
. . . . . .
I C7
T3
T6
?-9
T12
L3
Trunk segments
planes moved with greater range of motion, its movement in transverse plane ( axial rotation) was restricted as compared to normal subjects. Although the figures obtained
"
I°°[
-
lao~ Bieens rereads
Gastroenemius medialis
Peronens Iongus
50
o
~
~
~
,L
_ol o
70
40
~o
Be
1oo% I
78
Abstracts
Tab. 1: Kinematic & kinetic results (m ~an _+SD) Kinematic & Kinetic Parameters Affected limb l'runk Movement (o) 10.9_+1.3 Hip ROM (o)
Contralateral limb 3.0_+0.7
39.7+~9.2
Knee ROM (o) I "tForce Maximum (%BW)
54A-+5.8
50.8_+7.7
67.1+_.2.5
121,3_+10.7
136.8+~20.4
Force Minimum (% BW)
75.85=9.6
62.0+18.1
Z"a Force Maximum (%BW)
106.3_+6.4
121.8+13.4
Impulse (% of contralateral side)
74_+10
100
Stride length (m)
1.36+0.15
Relative stride length (% height) Gait Velocity (m/s)
95.0_+8.5 1.28_+.0.18
Results AII three tested variables, VR, CV and R, were able to differentiate an improvement of leg muscle EMG pattern during training. However, only the VR and the CV detected the significance of the improvement of patients with a small improvement. As expected a correlation analysis showed a tight relationship between VR, CV and R. A partial correlation between VR, CV and R revealed that the VR contains most information relating to changes in EM because the correlation between CV and R drops to nearly zero if the influence of the VR on this correlation is controlled. If only the mean EMG profiles are compared, as was done with R, much information contained in the single step profiles is lost, with VR and the CV this is not the case. Discussion Because of the above arguments we decided to use the VR as an amplitude-independent measure of the similarity between the patients' and healthy subjects' EMG profiles (Erni et at., 1998). The VR is now used as a standard analysis for the improvement of locomotor function after treadmill training in our clinic.
REFERENCES
1. Winkelmann W (1996) Rotationplasty. Orthopedic Clinics of North America 27(3):
503-523. 2. Winkelmaun W (1986). Hip rotationplasty for malignant tumors of the proximal part of the femur. J Bone Joint Surg [Am] 68-A: 362-9.
Session 11 Miscellaneous II
Acknowledgments This work was supported by grants from the Swiss National Science Foundation (No 3100-042899.95) and the Intemafional Research Institute for Paraplegia (P 16/93). References
Barbeau, H., and Rossignol, S. (1994). Enhancement of locomotor recovery following spinal cord injury. Curr. (?pin. Neurol., 7:517-524. Diets, V., Colombo, G. and Jensen, L. (1994). Locomotor activityin spinal man. The Lancet, 344(8932): 1260-1263. Dietz, V., Colombo. G., Jensen, L. and Baumgartoer,L. (1995). Locomotor capacity of spinal cord in paraplegic patients. Annals of Neurology, 37(5):574-582.
V A R I A T I O N R A T I O : A N E W A P P R O A C H T O ASSESS CHANGES IN LEG MUSCLE EMG P A T T E R N
G. Colombo, Th. Emi and V. Dietz Paraplegic Centre, University Hospital Balgrist, Fomhstr. 340, CH-8008 Ziirich, Switzerland Introduction Treadmill training is a welI established therapy for incomplete spinal cord injured patients. Recent studies have demonstrated an improvement of locomotor fimefion to be associated with an increase in EMG activity in leg extensor muscles in both complete and incomplete paraplegic patients but only the incomplete do profit functionaly (Dietz et at. 1994, 1995; Wemig et al., 1995). To show the effects of the training, EMG activity was recorded once a week while the patients were walking on the treadmill. The root mean square of the EMG (EMG RMS) was calculated during defined periods of the stap cycle. Changes in leg muscle EMG activity were analyzed using theses values as a function of training. It was shown that during the course of the training a significant increase in EMG RMS occurred in some leg muscles. A s the EMG RMS is amplitudedependent, it is influenced by several variables which differ between and also within subjects and even from day to day. Therefore, statistical analysis of RMS data may not always be appropriate. Furthermore, EMG R_MS provides little information about changes of.the modulation of EMG activity. The aim of this study was to utiIise amplitude-independant EMG analysis techniques in the hope that they would reveal recovery of the patients' EMG activity (overall EMG modulation; EM) towards that of healthy subjects. Three possible analysis techniques were considered: the Pearson correlation coefficient (R), the variation ratio (VR) (Harshler & Milner, 1978) and the coefficient of variation (CV). Methods Data was collected from 6 patients with either complete or incomplete paraplegia. They underwent a daily locomotor training on a treadmill. EMG recordings were made weekly from the medial gastroanemius and tibialis anterior muscles. Physiotherapists were assisting the leg movements but their involvement was kept to a minimum. The patients' body weight was partially unloaded using a parachute harness connected to an overhead crane. The same recordings were taken from I6 healthy subjects walking on the treadmill. All signals were sampled at 600Hz and individual step cycles, triggered by the impact of the right heel, were normalized to a relative time scale of one step cycle starting and ending with the fight heel strike. Each step cycle consisted of 1001 temporal points. The EMG signal was rectified and for each stride the EMG profile was normalized by setting its mean to 100%. The patients' mean EMG over 16 strides of each recording session was calculated for each muscle. For each of the 16 healthy subjects the mean EMG over 100 strides was calculated and from this the grand mean for all 16 healthy subjects was calculated. To compare the patients' EM with the healthy subjects' EM during gait, three different techniques were used: A) Pearsons' correlation coefficient: This was calculated between the patients' mean EMG profile of each session and the healthy subjects grand mean EMG profile. B) Variation ratio: Calculated according to Hershler & Milner (1978). The VR provides a measure of the repeatability of a waveform over a given number of identical gait cycles. The more similar the pafients' and the healthy subjects' EM the smaller the VR. C) Coefficient of variation: can be considered as a measure of the variance-to-signal ratio. The CV for each measurement session was calculated over the same 32 EMG profiles that were used to calculate the VR. Smaller CV are indicative of similarities between waveforms.
Emi; Th., Colombo, G (1998). Locomotortraining in paraplegic patients: a new approach to asses changes m leg muscle EMG patterns. Electroencephalography and clinical Neuropbysiology 109: 135-139.
Herschler, C. and Miiner, M. (1978). An optimality criterion for processing electromyographic(EMG) signalsrelating to human locomotion. [EEE Trans. Biomed, Eng., BME-25(5):413-420. Wemig, A,, i'?Iiillcr,S., Nanassy, A, and Cagol, E, (1995). Lauiband therapy based on 'rules of spinal locomotion' is effective in spinaI cord-injuredpersons. Eur. £ Neurosci., 7:823-829.
QUANTIFICATION OF NON-STANDARD E M G PATTERNS A.L. Hof, W. Grimmius, H. Elzinga and J.P.K. Halbertsma Laboratory of Human Movement Analysis, Dept. of Rehabilitation, University Hospital PO box 30.001 9700 RB Groningen, The Netherlands. E-mail: [email protected] In many gait laboratories routinely surface electromyograms (EMGs) are recorded from patients during gait. A standard procedure is to process these into averaged rectified EMG patterns (Kleissen et al., 1997). To see if there is any abnormality, these averaged patterns can be compared to standard patterns of healthy subjects, obtained from literature (Winter 1991) or obtained in the own laboratory (Hof and Kleissen, i997). The comparison is usually done at sight: guided by experience an individual EMG pattern is classified as normal, mildly abnormal, or abnormal. The purpose of the present study is to find an objective method to perform this classification: first, to give an objective method to classify a pattern as standard or non-standard and, second, to give a measure of the deviation from the standard. METHODS Standard averaged EMG patterns were obtained from two groups of ten healthy young subjects for fourteen muscles. The time scale was normalised into 100 percentage points of a complete stride. For each subject 10 steps were averaged, the data for the 10 subjects were averaged to obtain the grand average or 'standard' pattern E,dp). An individual averaged EMG patiems e,~dp) is first normalised to the standard pattern by determining the individual gain factor gmi and dividing by it:
e'~,(p) = % (p)/g,,~
(1)
The indexes denote: m for the muscles, i for the individuals, andp for the time scale, expressed as percentage of a complete stride (starting at heel contact). Gain factor gml can be determined by linear regression (with zero intercept) of the individual e~i(p) with the standard
Edp). Next m the standard average pattern E~(p), also the upper limit Hm(p) and lower limit L,dp) were obtained from the group of normal subjects. To this end first the individual patterns were normalised according to (2) and from these 10 normalised patterns the upper and lower limit of the range were estimated for every p from the 25 and 75-th percentile values: H (p) = 1.5- e~0~5(p) - 0.5. e~0.25(p)
(2)
L~ (p) = 1.5. e2o.2s (p) - 0.5. e2o.7, (p)
In addition, L~(p) is limited to be above zero. To obtain a measure for the 'non-standardness' of an individual averaged EMG pattern, first the p's are obtained for which the e*mdp) is outside the range between Lm(p) and Hm(p). Then the difference between the individual normalised EMG and the standard pattern are squared over these outlying points t)o,i, summed and divided by the summed square of the standard pattern. Finally the square root of this ratio is taken.
References Dully CM et al. (1996). Dev Med Child NeuroL 38:238-243 Saunders JBDM et al (t953) J Bone It Surg. 35A: 543-588 Jensen RK (1986) J Biomechanics. 19: 359-368. Eames MI-IA et al (1999) Hum Mov Sci. [in press] Duffy CM et al (1996b) Gait and Posture 4:34-38
77
were small and probably virtually indiscernible to the human eye. they implied that PD subjects had lost the rotatory component of their trunk while rising. It was not anticipated that large amount of trunk lateral flexion would be observed during STS in normal subjects. However, an impaired motor control system probably caused a larger range of lateral inclination in PD patients that would be an important feature to monitor Although Increased flexion of the trunk during STS seen in PD can be a potential threat to their balance, it could be a strategy helping them to eliminate or shorten the unstable phase by center of mass repositioning The pattern of internal bending of the trunk in frontal plane can be another compensatory mechanism in order to keep the body center of mass within the base of support to sustain the uptight balance at the termination of the task. It is hoped that during rehabilitation , the successful use of strategies aiming to increase the total range o f trunk axial rotation improve mobility of the trunk, which lead to functional improvements including ease of standing and walking.
References: l)Alexander NB, Schultz AB. Rising from a chair. Effects of age and functional ability, on performance biomechanics. J Gerontology 1991:46:M91-8 2)Lakke JPWF. Axial apraxia in Parkiuson's disease. J Neurological Sciences 1985;69:37-46
KINEMATICS ANALYSIS OF THE TRUNK MOTION DURING SIT TO STAND iN PARK1NSON' S DISEASE Dr ENikfekr*, Dr D. Playford,* Mr S. Attfield** * Rehabilitation Research Unit, Division of rehabilitation and ageing, Queen's Medical Center, University of Nnttingham ** Bioengineering Research Center, Derby Acute Hospitals NHS Trust.
K I N E M A T I C AND E L E C T R O M Y O G R A P H I C O U T C O M E AFTER B3A-ROTATIONPLASTY
IN PATIENTS
D. Rosenbaum, A. Hillmann, W. Winkelmanu Funktiousbereich Bcwegungsanalytik, Orthop~idische Klinik, Universit~it Miinster
Introduction: Parkinson's disease (PD) is a common neurological disorder which causes falls, difficulty with walking and standing from a seated position, arising from a combination of direct effects of the disease ( ie. bradykinesia, rigidity and pastural inflexibility) and indirect (e.g fixed flexed posture and pelvis and trunk immobility). Getting out of a chair is considered one of the most important functions which is a particularly difficult manoeuvre for patients with Parkinson's disease. There is considerable information available about lower limbs kinematics and kinetics during sit to stand (STS), but little is known about trunk control during this task. This study aimed to provide insights for both the analysis of performance deficits in PD patients and in the developments of specific rehabilitation programs. The main objective was to ascertain how the trunk kinematics parameters differ from normal subjects Once the pattern of movement has been identified we can define the impact of medical (L-dopa) and physiotherapy on the trunk movement and function. Methodology: Four PD patients and five healthy age matched control subjects studied in the gait laboratory at the Derbyshire Royal Infirmery. Instrumentation consisted of a six camera Elite motion analysis system ( B T S . Bioengineering Technology System, Milan, Italy) which tracked 9 retrureflective markers at 100 frames per second. Markers placed on the left and right acrumion process for shoulder movement and along the spine at the following levels C7, T3, T6, T9, TI2, L3 and sacrum. Subjects were then asked to sit on a height adjusted stall within the calibrated volume of the gait analysis system and ask to stand. Then l) angular displacement of the trunk relative to room-coordinate system in the sagittaI, frontal and transverse planes; 2) vertical and lateral linear displacement of the trunk levels; 3) angular displacement of upper segment relative to lower segment of the trunk in sagittal and frontal plane, were calculated using inhouse programmed algorithms and exported into Excel. The mean of the ten data sets was then produced.
Results: The mean total range of motion observed in PD patients in transverse plane (11 ±0.2 degrees) was less than that observed in normal (3.7-*0.5 degrees) (unpaired t-test, p<0.001). During performing the task~ the normal subjects had a tendency to demonstrate a shredder rotation to the tight (external rotation), in contrast to the patiems whose shoulder mean position was only minimally rotated externally. The total mean range of motion in frontal plane calculated for normal trunk (2.2~:0.3 degrees) was significantly less (P<0.001) than the mean value measured in PD (4.85:0.3 degrees). Further analysis showed that also there was a remarkable difference with regard to upper and lower trunk segments between normal and PD groups. Both inclined with larger ranges of motion in PD than in normal. Measurement of lateral flexion of upper trunk segment relative to lower in PD indicated that the former inclined lateralIy Iess than the latter. This means that in the frontal identical In terms of sagittal _plane movement , the difference between mean trunk range of motion in PD (36.I±1 Idegrees) and normal (30.4-*l.5degrees) was highly significant (P<0.001). The present data suggested that there was less flexion in upper segment than the lower one in normal group. In the contrary , such a difference between two segments in PD was not significant.
Discussion: This study investigated sit to stand cycle in Parkinson's disease patients. The activity was examined under conditions as near normal as possible with few restraining condition Overall, it can be concluded that while the trunk in PD in sagittal and frontal Trunkrotationin TransverseplaneduringSTS
2t
Average lateral shift of trun k levels
t25.
INTRODUCTION Rotationplasty is a limb-salvage treatment modality for malignant bone tumours in children and adults. For different tumour localisations various modifications have been described (1,2). In those cases requiring a total resection of the femur (type BIIIa according to Winkelmann, 1996) the tibia is rotated by 180 ° and the lateral condyle is attached to the acetabular cup If this surgical technique is performed in young children the tibia is expected to develop a "femoral" head due to the loading situation. The result is a shortened leg that can be adapted to a conventional foot prosthesis with a customised shaft for the rotated foot. In the present study we investigated the gait and muscular function of these patients. METHODS Four patients (out of a total of 7 operated in our department) were seen in our Movement Analysis Lab between 4 and 7 years postoperatively. The patients (3 girls, 1 boy, 9 to 12 years old) walked along a 10 m long walkway at a self-salected comfortable speed. Kinematic and kinetic analyses were performed with a four camera MOTION ANALYSIS system and two strain-gage force plates. Surface EMG (NORAXON MYO 2000) was collected bilaterally from the hip muscles and from the thigh and shank muscles of the healthy and operated limb, respectively. RESULTS & DISCUSSION In general, a good gait function with normal gait velocity and stride length as well as a normal phase-related muscle activity (Fig. 1) could be observed. However, the trunk movement indicated a more or less pronounced Duchenne limping on the operated side and a certain weakness of the hip stabilising muscles that can be attributed to the surgical intervention (Tab. 1). Hip and knee range of motion were slightly reduced. Ground reaction force curves indicated a reduced loading and unloading during the stance phase. M R / i m a g e s revealed that the function depended on the extent of muscle resection that was oncologieally necessary as well as the training level of the remaining muscles X-rays revealed that the tibia had adapted to the altered loading conditions by developing a condyle which fit into the acetabular cup. CONCLUSION The results underline the general observation of a good functional restoration aider this type of rotationplasty. Even though the surgically unavoidable loss of stabilising muscles can be seen in the gait patterns the overall outcome and the demonstrated activity level of the patients underline the high degree of subjective satisfactiou of the patients.
Fig. 1: Comparison of thigh (healthy) and shank muscle (rotated limb) EMG patterns. 3o I
isoL Soleus
Rectus femoris
aO; ua
1~0~%.Gastrocnemius lateralia
during STS
as~
Ioo|Semitendinosus -,e!
" 0
20
40
60
S0
Persentageof STS cycle (%)
100
~o
. . . . . .
I C7
T3
T6
?-9
T12
L3
Trunk segments
planes moved with greater range of motion, its movement in transverse plane ( axial rotation) was restricted as compared to normal subjects. Although the figures obtained
"
I°°[
-
lao~ Bieens rereads
Gastroenemius medialis
Peronens Iongus
50
o
~
~
~
,L
_ol o
70
40
~o
Be
1oo% I
78
Abstracts
Tab. 1: Kinematic & kinetic results (m ~an _+SD) Kinematic & Kinetic Parameters Affected limb l'runk Movement (o) 10.9_+1.3 Hip ROM (o)
Contralateral limb 3.0_+0.7
39.7+~9.2
Knee ROM (o) I "tForce Maximum (%BW)
54A-+5.8
50.8_+7.7
67.1+_.2.5
121,3_+10.7
136.8+~20.4
Force Minimum (% BW)
75.85=9.6
62.0+18.1
Z"a Force Maximum (%BW)
106.3_+6.4
121.8+13.4
Impulse (% of contralateral side)
74_+10
100
Stride length (m)
1.36+0.15
Relative stride length (% height) Gait Velocity (m/s)
95.0_+8.5 1.28_+.0.18
Results AII three tested variables, VR, CV and R, were able to differentiate an improvement of leg muscle EMG pattern during training. However, only the VR and the CV detected the significance of the improvement of patients with a small improvement. As expected a correlation analysis showed a tight relationship between VR, CV and R. A partial correlation between VR, CV and R revealed that the VR contains most information relating to changes in EM because the correlation between CV and R drops to nearly zero if the influence of the VR on this correlation is controlled. If only the mean EMG profiles are compared, as was done with R, much information contained in the single step profiles is lost, with VR and the CV this is not the case. Discussion Because of the above arguments we decided to use the VR as an amplitude-independent measure of the similarity between the patients' and healthy subjects' EMG profiles (Erni et at., 1998). The VR is now used as a standard analysis for the improvement of locomotor function after treadmill training in our clinic.
REFERENCES
1. Winkelmann W (1996) Rotationplasty. Orthopedic Clinics of North America 27(3):
503-523. 2. Winkelmaun W (1986). Hip rotationplasty for malignant tumors of the proximal part of the femur. J Bone Joint Surg [Am] 68-A: 362-9.
Session 11 Miscellaneous II
Acknowledgments This work was supported by grants from the Swiss National Science Foundation (No 3100-042899.95) and the Intemafional Research Institute for Paraplegia (P 16/93). References
Barbeau, H., and Rossignol, S. (1994). Enhancement of locomotor recovery following spinal cord injury. Curr. (?pin. Neurol., 7:517-524. Diets, V., Colombo, G. and Jensen, L. (1994). Locomotor activityin spinal man. The Lancet, 344(8932): 1260-1263. Dietz, V., Colombo. G., Jensen, L. and Baumgartoer,L. (1995). Locomotor capacity of spinal cord in paraplegic patients. Annals of Neurology, 37(5):574-582.
V A R I A T I O N R A T I O : A N E W A P P R O A C H T O ASSESS CHANGES IN LEG MUSCLE EMG P A T T E R N
G. Colombo, Th. Emi and V. Dietz Paraplegic Centre, University Hospital Balgrist, Fomhstr. 340, CH-8008 Ziirich, Switzerland Introduction Treadmill training is a welI established therapy for incomplete spinal cord injured patients. Recent studies have demonstrated an improvement of locomotor fimefion to be associated with an increase in EMG activity in leg extensor muscles in both complete and incomplete paraplegic patients but only the incomplete do profit functionaly (Dietz et at. 1994, 1995; Wemig et al., 1995). To show the effects of the training, EMG activity was recorded once a week while the patients were walking on the treadmill. The root mean square of the EMG (EMG RMS) was calculated during defined periods of the stap cycle. Changes in leg muscle EMG activity were analyzed using theses values as a function of training. It was shown that during the course of the training a significant increase in EMG RMS occurred in some leg muscles. A s the EMG RMS is amplitudedependent, it is influenced by several variables which differ between and also within subjects and even from day to day. Therefore, statistical analysis of RMS data may not always be appropriate. Furthermore, EMG R_MS provides little information about changes of.the modulation of EMG activity. The aim of this study was to utiIise amplitude-independant EMG analysis techniques in the hope that they would reveal recovery of the patients' EMG activity (overall EMG modulation; EM) towards that of healthy subjects. Three possible analysis techniques were considered: the Pearson correlation coefficient (R), the variation ratio (VR) (Harshler & Milner, 1978) and the coefficient of variation (CV). Methods Data was collected from 6 patients with either complete or incomplete paraplegia. They underwent a daily locomotor training on a treadmill. EMG recordings were made weekly from the medial gastroanemius and tibialis anterior muscles. Physiotherapists were assisting the leg movements but their involvement was kept to a minimum. The patients' body weight was partially unloaded using a parachute harness connected to an overhead crane. The same recordings were taken from I6 healthy subjects walking on the treadmill. All signals were sampled at 600Hz and individual step cycles, triggered by the impact of the right heel, were normalized to a relative time scale of one step cycle starting and ending with the fight heel strike. Each step cycle consisted of 1001 temporal points. The EMG signal was rectified and for each stride the EMG profile was normalized by setting its mean to 100%. The patients' mean EMG over 16 strides of each recording session was calculated for each muscle. For each of the 16 healthy subjects the mean EMG over 100 strides was calculated and from this the grand mean for all 16 healthy subjects was calculated. To compare the patients' EM with the healthy subjects' EM during gait, three different techniques were used: A) Pearsons' correlation coefficient: This was calculated between the patients' mean EMG profile of each session and the healthy subjects grand mean EMG profile. B) Variation ratio: Calculated according to Hershler & Milner (1978). The VR provides a measure of the repeatability of a waveform over a given number of identical gait cycles. The more similar the pafients' and the healthy subjects' EM the smaller the VR. C) Coefficient of variation: can be considered as a measure of the variance-to-signal ratio. The CV for each measurement session was calculated over the same 32 EMG profiles that were used to calculate the VR. Smaller CV are indicative of similarities between waveforms.
Emi; Th., Colombo, G (1998). Locomotortraining in paraplegic patients: a new approach to asses changes m leg muscle EMG patterns. Electroencephalography and clinical Neuropbysiology 109: 135-139.
Herschler, C. and Miiner, M. (1978). An optimality criterion for processing electromyographic(EMG) signalsrelating to human locomotion. [EEE Trans. Biomed, Eng., BME-25(5):413-420. Wemig, A,, i'?Iiillcr,S., Nanassy, A, and Cagol, E, (1995). Lauiband therapy based on 'rules of spinal locomotion' is effective in spinaI cord-injuredpersons. Eur. £ Neurosci., 7:823-829.
QUANTIFICATION OF NON-STANDARD E M G PATTERNS A.L. Hof, W. Grimmius, H. Elzinga and J.P.K. Halbertsma Laboratory of Human Movement Analysis, Dept. of Rehabilitation, University Hospital PO box 30.001 9700 RB Groningen, The Netherlands. E-mail: [email protected] In many gait laboratories routinely surface electromyograms (EMGs) are recorded from patients during gait. A standard procedure is to process these into averaged rectified EMG patterns (Kleissen et al., 1997). To see if there is any abnormality, these averaged patterns can be compared to standard patterns of healthy subjects, obtained from literature (Winter 1991) or obtained in the own laboratory (Hof and Kleissen, i997). The comparison is usually done at sight: guided by experience an individual EMG pattern is classified as normal, mildly abnormal, or abnormal. The purpose of the present study is to find an objective method to perform this classification: first, to give an objective method to classify a pattern as standard or non-standard and, second, to give a measure of the deviation from the standard. METHODS Standard averaged EMG patterns were obtained from two groups of ten healthy young subjects for fourteen muscles. The time scale was normalised into 100 percentage points of a complete stride. For each subject 10 steps were averaged, the data for the 10 subjects were averaged to obtain the grand average or 'standard' pattern E,dp). An individual averaged EMG patiems e,~dp) is first normalised to the standard pattern by determining the individual gain factor gmi and dividing by it:
e'~,(p) = % (p)/g,,~
(1)
The indexes denote: m for the muscles, i for the individuals, andp for the time scale, expressed as percentage of a complete stride (starting at heel contact). Gain factor gml can be determined by linear regression (with zero intercept) of the individual e~i(p) with the standard
Edp). Next m the standard average pattern E~(p), also the upper limit Hm(p) and lower limit L,dp) were obtained from the group of normal subjects. To this end first the individual patterns were normalised according to (2) and from these 10 normalised patterns the upper and lower limit of the range were estimated for every p from the 25 and 75-th percentile values: H (p) = 1.5- e~0~5(p) - 0.5. e~0.25(p)
(2)
L~ (p) = 1.5. e2o.2s (p) - 0.5. e2o.7, (p)
In addition, L~(p) is limited to be above zero. To obtain a measure for the 'non-standardness' of an individual averaged EMG pattern, first the p's are obtained for which the e*mdp) is outside the range between Lm(p) and Hm(p). Then the difference between the individual normalised EMG and the standard pattern are squared over these outlying points t)o,i, summed and divided by the summed square of the standard pattern. Finally the square root of this ratio is taken.