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Performance of walking orthosis for paraplegics
86
Gait & Posture PERFORMANCE
1995; 3: No 2
OF WALKING
ORTHOSIS
FOR PARAPLEGICS
M. Solomonow Bioengineering Laboratory Dept. of Orthopedic Surgery Louisiana State University Medical Center New Orleans, LA 70112 Several mechanical and muscle stimulation-based orthoses have been developed over the last two decades with the objective of allowing paraplegics some simple locomotion functions. Some of the orthoses have become available to the public through commercial sources (LLB. HGO, RGO, Parastep) while others are still undergoing clinical trials in research institutions (RGO & FES, Cleveland FES, Vienna FES). Two distinct classes and a hybrid thereof arc apparent: the Long Leg Brace (LLB) Hip Guidance Orthosis (HGO), and Reciprocating Gait Orthosis (RGO) are mechanical devices which rely on upper-body power for inducing the Iocomotion dictions, while the Parastep. Cleveland FES and Vienna FES systems are based mostly on locomotion elicited by elect&al stimulation of the paralyzed leg muscles. The hybrid systems utilize a mechanical brace simultaneously with electrical stimulation of the leg muscles as the major power source for locomotion (RGO & FES, HGO & FES), eliminating the need for upper body power. Over the years, experience with the devices described above shed light on the advantages of each one. Most mechanical devices seem to be bulky, but relatively reliabie while consuming 4-8 times the energy cost associated with locomotion of a normal healthy patient. The systems based on electical muscle stimulation alone are complex and experience reliability problems as well as energy cost in excess of 8 times that associated with normals. Locomotion distance is also a factor. Most paraplegics are able to walk longer distances with a mechanical ortbosis than when using an FES orthosis. The explanation is complex, but it mostly rests on the fact that electrical stimulation of muscle as it is exercised today elicits fatigue at a much faster rate than muscles under voluntary control. Also, we have to significantly refine the stimulation pattern of many leg muscles during the swing-stance cycles of gait in order to produce a smooth, stable and safe gait. The third approach, which includes the hybrid FES systems, seems to lead the field at the moment. These systems provide a stable and reliable low-energy standing function and simulataneously allow for fatigue-free locomotion by reducing the effect of the upper body with the use of short cycled electrical stimulation of selected large leg muscles. The Bioengineering Laboratory at LSU developed the RGO and the RGO & FES hybrid systems, and the latter has been tested on over 70 patients within the last five years. Briefly, the RGO is a hip, knee, and ankle foot orthosis which consists of a plastic AFO with extending aluminum uprights. During locomotion, the knees are kept in the locked position. The hip joints are interconnected by a pair of Bowtien cables which have two fimctions: to prevent hip extension during quiet standing and to create synergistic relations between the two hips during locomotion, e.g., hip flexion of one side is accompanied by con&al&& hip extension such that the swing phase of one leg is performed simultaneously with contralateral
COMPARISON VERTICAL
OF OVERGROUND AND TREADMILL GROUND REACTION FORCES
Car& Tucker, Scott C White Heather C&ins Depat. of Physical Therapy & Exerwe Science SUNY at Buffalo, ButTao, NY 14214
H. John Yac’c
PhyslcaI Therapy Graduate Program University of Iowa, Iowa City, IA 52242
push-otT, The hip joints are linked with a posterior alummum pelvic band, and uprights extend from the pelvic band bilaterally to the mid-thoracic area. The power required for locomotion is derived by surface electical stimulation of the rectus femoris muscle of one leg simultaneously with contralateral stimulation ofthe hamstrings. Since both muscles transmit forces across the hip joints (and the knees are locked in extension), hip flexion with contralateral hip extension is elicited. Quiet standing is supported by the mechanical exoskeleton (without stimulation) and standing up from a seated position is accomplished by simultaneous stimulation of the quadriceps and hamstrings of both legs. Results of our clinical experience provide the following data: Most patients were able to walk unintermpted for up to 600 meters. wh-hile several patients could walk up to 1500 meters. Over 75% of the patients could don-duff the system and stand up from the seated position without any aid from an able-bodied person. The locomotion coupled with electrical stimulation resulted in sigoifiamt reduction of joint contractures and spasticity in the legs, as well as an increase in cardiac output, stroke volume, and vital capacity. There was a marked decrease, a virtual elimination of pressure sores as well as a decrease in calcium concentration in the blood and urine samples, indicating that osteoporosis had been halted or reversed. Energy consumption studies of a group of patients with injuries ranging from T-1 to T-10 and with time elapsed since injury ranging from 1 to 20 years show that a 15% reduction in K&l/kg-m and KC&kg&n is present when FES is added to the RGO. Furthermore, comparison of the RGO & FES hybrid system to the RGO, HGO, LLB, and the Cleveland FES system show that the RGO-FES consumed the least energy with gradually increasing cost for the RGO, HGO, LLB, and the Cleveland FES system, respectively. The average optimal cadence was .21 mls, as patients selected it for their comfort Finally, while the RF0 & FES shows promise as a contemporary tool for rehabilitation It is difficult of paraplegics, much more research is necessary to improve present limitations. to replace the antigravity support, reliability, safety and function of mechamcal braces, yet their bulky and non-cosmetic aspects need to be gradually minimized and improved. At the same time, increased function is called for by patients. The ability to climb up and down stairs, walk on diverse terrain, and fbrther reduce energy consumption is necessary to improve patient acceptance of walking systems. Acknowledgement
This work was supported by the LSU Board of Regents with LEQSF Grants References
Solomonow, M., et al. Orthopedics 12:1309-1315,1989. Hirokawa, S., et al. Arch Physical Med. and Rehab. 71:6X7-694, Mars&is, B., et al. Arch Physical Med. and Rehab. 69:243-249, New, A., et al. Paraplegia 275-18, 1989
1990. 1988.
have a flatter appearance with maximum force values (Fl t b-3) being reduced and the minimum force duing mid stance (F2) bring higher. Si&icant diierences were observed in F2 and F3 at the normal and fast speeds (Table 1). The only significant difierensc in the timing of the forces was for F3 during slow walking (Table 1).
---~
_~ --.--
-. -
INTRODUCTION ‘Ike treadmill has been advocated as a device that offers many attractive possibilities for gait retraining. The possibility of differences between overground (OG) and treadmill (TM) g&
however, lingers as a deterrent to using the TM while a number of studies have compared the biomechmics of TM and UG gait these shldies have mainIy focused on kinemahc, energy, and EMG data (Arsenault et al., 1986). Little is known about the kinetics of treadmill gait. The purpose of this study was to compare the vertical ground reaction forces for TM and OG walking. Given the similarities in other biomechanical measures identified in previous studies, it was hypoulesixd that the vertical forces would not be diiexent.
%OFSIIWE
I I.
METHODOLOGY
Figure 1 Interxubject Twenty four subjects (age 23-42 p), recruited this study. Informed
consent was obtained
from the University
community participated
ensemble averaged force partems for fast walking.
in
&om all subjects.
Subjects walked OG on a 12 m walkway containing 2 K&&r force plates located in the center of the walkway and staggered to capture consecutive foot contacts. A pair of photo detectors connected to a timer and situated 2.5 m apart were used to measure fonvard velocity. For TM waudng subjects wa&ed on a force measuring TM that contained 2 force plates mounted in tandem (Kistler
I I
Inc.).
The cadence of each subject was documented with them walking at their waral speed OG. 4 metronome was used to vary the subjecrs’ cadence by +i- 20 to obtain data for fat and slow walking. During TM walking a metronome was used to maintain cadence equivalent to the OG tcids. Treadmill speed for each of the trials was set according to the calculated speed during the OG ttiak. Data from the force plates were AID converted at 500 Hz and filtered at 100 Hz. using BIOWARE (Kistler Inc). A modified software routine was used to separate out individual foot cmttacts during treadmiU gait. Vertical force data were compared for the left and right foot contacts on five repeated trials OG and on 5 randomly selected foot confact pairs obtained from the TM over a 30 s data coUection interval. Selected measures were compared using a repeated mea.mces ANOVA @<.05). RESULTS Representative results for the intersubject ensemble averaged data comparing OG to TM gait at the fast walking speed is shown in Figure 1. The vertical force curve for TM walking tends to
Table 1 Comparison Flmax
of averaged magnitude and timing of vertical ground reaction forces
F2max T 0 T 13.2 5.5’ 5.9* 120 6.9’ 7.2’ 10.6 85 86 * mdicates where significant di&rences WEE” F N S
0 13 3 12 I 108
F3max Tlmax 0 T 0 T 11.2 ll.5’ 205 200 11.7’ 11.1’ 21 4 210 107 104 239 241 occurred between OG and
T2ma.x 0 T 51 I 500 492 484 44.1 44 3 TM gait.
T3max 0 T 813 802 806 795 78.73 75.5’
DISCUSSION The pdimimry re.&s ofthis study demonstrate kinetic differences in the vertica1 ground reaction forces for OG and TM walking. These differences suggest that when walking on a TM peak vertical forces during pushoff (53) was reduced by an average of 5.1% and F2 may be increased by an average of 9.7% compared to OG walking. These differences are not explained by praiow kinematic and EMG studxs (Isacson et al., 1986) and require further research to uncover the underlying mechanisms. REFERENCES
Gait & Posture PERFORMANCE
1995; 3: No 2
OF WALKING
ORTHOSIS
FOR PARAPLEGICS
M. Solomonow Bioengineering Laboratory Dept. of Orthopedic Surgery Louisiana State University Medical Center New Orleans, LA 70112 Several mechanical and muscle stimulation-based orthoses have been developed over the last two decades with the objective of allowing paraplegics some simple locomotion functions. Some of the orthoses have become available to the public through commercial sources (LLB. HGO, RGO, Parastep) while others are still undergoing clinical trials in research institutions (RGO & FES, Cleveland FES, Vienna FES). Two distinct classes and a hybrid thereof arc apparent: the Long Leg Brace (LLB) Hip Guidance Orthosis (HGO), and Reciprocating Gait Orthosis (RGO) are mechanical devices which rely on upper-body power for inducing the Iocomotion dictions, while the Parastep. Cleveland FES and Vienna FES systems are based mostly on locomotion elicited by elect&al stimulation of the paralyzed leg muscles. The hybrid systems utilize a mechanical brace simultaneously with electrical stimulation of the leg muscles as the major power source for locomotion (RGO & FES, HGO & FES), eliminating the need for upper body power. Over the years, experience with the devices described above shed light on the advantages of each one. Most mechanical devices seem to be bulky, but relatively reliabie while consuming 4-8 times the energy cost associated with locomotion of a normal healthy patient. The systems based on electical muscle stimulation alone are complex and experience reliability problems as well as energy cost in excess of 8 times that associated with normals. Locomotion distance is also a factor. Most paraplegics are able to walk longer distances with a mechanical ortbosis than when using an FES orthosis. The explanation is complex, but it mostly rests on the fact that electrical stimulation of muscle as it is exercised today elicits fatigue at a much faster rate than muscles under voluntary control. Also, we have to significantly refine the stimulation pattern of many leg muscles during the swing-stance cycles of gait in order to produce a smooth, stable and safe gait. The third approach, which includes the hybrid FES systems, seems to lead the field at the moment. These systems provide a stable and reliable low-energy standing function and simulataneously allow for fatigue-free locomotion by reducing the effect of the upper body with the use of short cycled electrical stimulation of selected large leg muscles. The Bioengineering Laboratory at LSU developed the RGO and the RGO & FES hybrid systems, and the latter has been tested on over 70 patients within the last five years. Briefly, the RGO is a hip, knee, and ankle foot orthosis which consists of a plastic AFO with extending aluminum uprights. During locomotion, the knees are kept in the locked position. The hip joints are interconnected by a pair of Bowtien cables which have two fimctions: to prevent hip extension during quiet standing and to create synergistic relations between the two hips during locomotion, e.g., hip flexion of one side is accompanied by con&al&& hip extension such that the swing phase of one leg is performed simultaneously with contralateral
COMPARISON VERTICAL
OF OVERGROUND AND TREADMILL GROUND REACTION FORCES
Car& Tucker, Scott C White Heather C&ins Depat. of Physical Therapy & Exerwe Science SUNY at Buffalo, ButTao, NY 14214
H. John Yac’c
PhyslcaI Therapy Graduate Program University of Iowa, Iowa City, IA 52242
push-otT, The hip joints are linked with a posterior alummum pelvic band, and uprights extend from the pelvic band bilaterally to the mid-thoracic area. The power required for locomotion is derived by surface electical stimulation of the rectus femoris muscle of one leg simultaneously with contralateral stimulation ofthe hamstrings. Since both muscles transmit forces across the hip joints (and the knees are locked in extension), hip flexion with contralateral hip extension is elicited. Quiet standing is supported by the mechanical exoskeleton (without stimulation) and standing up from a seated position is accomplished by simultaneous stimulation of the quadriceps and hamstrings of both legs. Results of our clinical experience provide the following data: Most patients were able to walk unintermpted for up to 600 meters. wh-hile several patients could walk up to 1500 meters. Over 75% of the patients could don-duff the system and stand up from the seated position without any aid from an able-bodied person. The locomotion coupled with electrical stimulation resulted in sigoifiamt reduction of joint contractures and spasticity in the legs, as well as an increase in cardiac output, stroke volume, and vital capacity. There was a marked decrease, a virtual elimination of pressure sores as well as a decrease in calcium concentration in the blood and urine samples, indicating that osteoporosis had been halted or reversed. Energy consumption studies of a group of patients with injuries ranging from T-1 to T-10 and with time elapsed since injury ranging from 1 to 20 years show that a 15% reduction in K&l/kg-m and KC&kg&n is present when FES is added to the RGO. Furthermore, comparison of the RGO & FES hybrid system to the RGO, HGO, LLB, and the Cleveland FES system show that the RGO-FES consumed the least energy with gradually increasing cost for the RGO, HGO, LLB, and the Cleveland FES system, respectively. The average optimal cadence was .21 mls, as patients selected it for their comfort Finally, while the RF0 & FES shows promise as a contemporary tool for rehabilitation It is difficult of paraplegics, much more research is necessary to improve present limitations. to replace the antigravity support, reliability, safety and function of mechamcal braces, yet their bulky and non-cosmetic aspects need to be gradually minimized and improved. At the same time, increased function is called for by patients. The ability to climb up and down stairs, walk on diverse terrain, and fbrther reduce energy consumption is necessary to improve patient acceptance of walking systems. Acknowledgement
This work was supported by the LSU Board of Regents with LEQSF Grants References
Solomonow, M., et al. Orthopedics 12:1309-1315,1989. Hirokawa, S., et al. Arch Physical Med. and Rehab. 71:6X7-694, Mars&is, B., et al. Arch Physical Med. and Rehab. 69:243-249, New, A., et al. Paraplegia 275-18, 1989
1990. 1988.
have a flatter appearance with maximum force values (Fl t b-3) being reduced and the minimum force duing mid stance (F2) bring higher. Si&icant diierences were observed in F2 and F3 at the normal and fast speeds (Table 1). The only significant difierensc in the timing of the forces was for F3 during slow walking (Table 1).
---~
_~ --.--
-. -
INTRODUCTION ‘Ike treadmill has been advocated as a device that offers many attractive possibilities for gait retraining. The possibility of differences between overground (OG) and treadmill (TM) g&
however, lingers as a deterrent to using the TM while a number of studies have compared the biomechmics of TM and UG gait these shldies have mainIy focused on kinemahc, energy, and EMG data (Arsenault et al., 1986). Little is known about the kinetics of treadmill gait. The purpose of this study was to compare the vertical ground reaction forces for TM and OG walking. Given the similarities in other biomechanical measures identified in previous studies, it was hypoulesixd that the vertical forces would not be diiexent.
%OFSIIWE
I I.
METHODOLOGY
Figure 1 Interxubject Twenty four subjects (age 23-42 p), recruited this study. Informed
consent was obtained
from the University
community participated
ensemble averaged force partems for fast walking.
in
&om all subjects.
Subjects walked OG on a 12 m walkway containing 2 K&&r force plates located in the center of the walkway and staggered to capture consecutive foot contacts. A pair of photo detectors connected to a timer and situated 2.5 m apart were used to measure fonvard velocity. For TM waudng subjects wa&ed on a force measuring TM that contained 2 force plates mounted in tandem (Kistler
I I
Inc.).
The cadence of each subject was documented with them walking at their waral speed OG. 4 metronome was used to vary the subjecrs’ cadence by +i- 20 to obtain data for fat and slow walking. During TM walking a metronome was used to maintain cadence equivalent to the OG tcids. Treadmill speed for each of the trials was set according to the calculated speed during the OG ttiak. Data from the force plates were AID converted at 500 Hz and filtered at 100 Hz. using BIOWARE (Kistler Inc). A modified software routine was used to separate out individual foot cmttacts during treadmiU gait. Vertical force data were compared for the left and right foot contacts on five repeated trials OG and on 5 randomly selected foot confact pairs obtained from the TM over a 30 s data coUection interval. Selected measures were compared using a repeated mea.mces ANOVA @<.05). RESULTS Representative results for the intersubject ensemble averaged data comparing OG to TM gait at the fast walking speed is shown in Figure 1. The vertical force curve for TM walking tends to
Table 1 Comparison Flmax
of averaged magnitude and timing of vertical ground reaction forces
F2max T 0 T 13.2 5.5’ 5.9* 120 6.9’ 7.2’ 10.6 85 86 * mdicates where significant di&rences WEE” F N S
0 13 3 12 I 108
F3max Tlmax 0 T 0 T 11.2 ll.5’ 205 200 11.7’ 11.1’ 21 4 210 107 104 239 241 occurred between OG and
T2ma.x 0 T 51 I 500 492 484 44.1 44 3 TM gait.
T3max 0 T 813 802 806 795 78.73 75.5’
DISCUSSION The pdimimry re.&s ofthis study demonstrate kinetic differences in the vertica1 ground reaction forces for OG and TM walking. These differences suggest that when walking on a TM peak vertical forces during pushoff (53) was reduced by an average of 5.1% and F2 may be increased by an average of 9.7% compared to OG walking. These differences are not explained by praiow kinematic and EMG studxs (Isacson et al., 1986) and require further research to uncover the underlying mechanisms. REFERENCES