Logo for the Journal of Rehab R and D

Volume 46 Number 3, 2009
   Pages 435 — 446

Walking mechanics of persons who use reciprocating gait orthoses

William Brett Johnson, BE;1-2 Stefania Fatone, PhD, BPO (Hons);1* Steven A. Gard, PhD1-3

1Northwestern University Prosthetics Research Laboratory and Rehabilitation Engineering Research Program, Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University,
Chicago, IL; 2Department of Biomedical Engineering, Robert R. McCormick School of Engineering and Applied Science,
Northwestern University, Evanston, IL; 3Jesse Brown Department of Veterans Affairs Medical Center, Chicago, IL

Abstract — Although ambulation with a reciprocating gait orthosis (RGO) may provide physical benefits to people with lower-limb paralysis, the high metabolic energy cost associated with ambulation limits orthosis use. The purpose of this case series was to investigate the dynamics of ambulation with RGOs to identify and better understand the potential causes of the high energy cost. Data were acquired from five regular users of RGOs. Kinematics and kinetics were measured, and the moments and powers acting at the hips and shoulders calculated. All RGO users walked with a flexed trunk and bore a large proportion of body weight through the arms during single support. Moments at the shoulder encouraged trunk extension, while moments at the hip encouraged trunk flexion. An extension moment acted on the hip at the beginning of swing, which was antagonistic to the goal of swing and contradicted the intent of the reciprocal link: to advance the swing leg. These results suggest that characteristics of RGO ambulation are consistent across users. The relationship between posture, forces acting on the walking aids, and the action of the RGO reciprocal link should be further explored because these factors likely contribute to the high metabolic cost of ambulation with an RGO.

Key words: biomechanics,gait, gait analysis,hip-knee-ankle-foot orthosis,kinematics,kinetics,orthotic devices,lower-limb paralysis,rehabilitation,reciprocating gait orthosis,RGO biomechanics, gait, gait analysis, hip-knee-ankle-foot orthosis, kinematics, kinetics, orthotic devices, lower-limb paralysis, rehabilitation, reciprocating gait orthosis, RGO.


Abbreviations: 3-D = three-dimensional, COM = center of mass, GRF = ground reaction force, HGO = hip guidance orthosis, HKAFO = hip-knee-ankle-foot orthosis, IRGO = isocentric reciprocating gait orthosis, RGO = reciprocating gait orthosis, ROM = range of motion, VA = Department of Veterans Affairs, VACMARL = VA Chicago Motion Analysis Research Laboratory.
*Address all correspondence to Stefania Fatone, PhD, BPO (Hons); Northwestern University Prosthetics Research Laboratory and Rehabilitation Engineering Research Program, 345 E Superior Street, RIC 1441, Chicago, IL 60611; 312-238-6538; fax: 312-238-6510. Email:s-fatone@northwestern.edu
DOI:10.1682/JRRD.2008.01.0017
Introduction

Studies have shown that an upright posture and walking can benefit people with lower-limb paralysis. These benefits include reduced incidence of joint contractures, bone fractures, and pressure sores [1]; prevention of osteoporosis [2]; improved bowel function, urinary drainage, and peripheral circulation; and stimulation of leg growth for growing children [3]. Other studies have also claimed that upright ambulation has psychosocial advantages [4-6], such as improved interaction with peers [3] and the environment [5], more positive perception of the body, [6] and greater self-respect [4].

Many assistive devices have been developed to help people with lower-limb paralysis stand and walk. These devices range from the relatively simple, conventional hip-knee-ankle-foot orthosis (HKAFO) [7] to the more complex reciprocating gait orthosis (RGO) [8]. Both orthoses immobilize the knees and ankles in an appropriate standing alignment and allow ambulation with crutches or a walker. The conventional HKAFO also immobilizes the hip joint; hence, users usually adopt a swing-to or swing-through gait pattern. Other orthoses such as RGOs, the hip guidance orthoses (HGOs) [9], and the Walkabout orthosis (Polymedic; Ashmore, Gold Coast, Australia) [10] allow hip motion in the sagittal plane, which enables users to adopt a reciprocal gait pattern that is more similar to nondisabled walking than a swing-through gait pattern. While the HGO and Walkabout are designed with the intent of gravity advancing the swing leg [9-10], a special mechanism in the RGO, referred to as the reciprocal link, is intended to facilitate the reciprocal gait pattern by coupling motion of the two hip joints so that flexing one hip joint extends the contralateral hip, and vice versa.

Despite the perceived benefits of upright ambulation and the more cosmetic gait provided by RGOs, discontinu-ation of RGO use is high. Discontinuation of orthosis use ranges from 61 to 90 percent for children with myelomeningocele [11-12] and from 46 to 54 percent in adults with spinal cord injury [13-16]. Sykes et al. reported that adults who persevered in using RGOs considered the orthosis to be exercise equipment [12], which they used on average three times a week for approximately 2 hours. Many of the RGO users surveyed by Sykes et al. cited the effort needed to ambulate with the orthosis as the main reason for limiting RGO use [12].

Walking with RGOs is slow and exhausting [17-18]. Studies have reported the oxygen cost of RGO walking to be 1.0 mL/kg/m at user-selected walking speeds ranging from 0.2 to 0.3 m/s [17-19] compared with 0.176 mL/kg/m at 1.28 m/s for nondisabled persons [20]. Bernardi et al. measured metabolic energy and calculated the mechanical energies for each body segment of 10 RGO users and reported that the mechanical work associated with RGO ambulation was significantly greater than that for nondisabled walking [18]. They concluded that the mechanical power required for walking with an RGO was a major cause of the high metabolic energy expenditure. However, the aspects of RGO gait dynamics that contributed to these mechanical inefficiencies remain unclear. Further understanding of the gait dynamics of RGO ambulation is needed for the high metabolic energy expenditure required of users to be reduced. This reduction would likely make the RGO a more useful device for people with paraplegia.

Unfortunately, only a few quantitative analyses of RGO gait dynamics are reported in the literature [7]. Although Bernardi et al. measured the trajectory of each body segment to calculate mechanical energy, they did not report these trajectories [18]. Whittle and Cochrane undertook one of the first dynamic analyses of people walking with RGOs with a group of 12 adults with thoracic-level lesions [21], reporting the range of rotational motion at the hip in the coronal and sagittal planes. They also reported the subjects' stride characteristics and the peak crutch force experienced over the gait cycle. Kawashima et al. reported the hip angles in the sagittal plane for the entire gait cycle [19], as well as the vertical ground reaction forces (GRFs) acting on the feet and crutches of 10 RGO users. Probably the most comprehensive study published to date was by Tashman et al. [22]. They measured the three-dimensional (3-D) kinetics and kinematics for a single RGO user during the single-support phase of stance and reported motion of the legs relative to a global frame and the pelvis, as well as the motion of the upper body relative to the pelvis. They also reported the GRFs acting on the subject's foot and crutches in three dimensions and calculated the forces and moments acting on the subject's hips and shoulders in three dimensions. These studies illustrate that although some dynamic analyses are available in the literature, they are generally limited to a single subject, dimension, or phase of the gait cycle.

We desire to develop an improved understanding of the gait dynamics of RGO users and to identify factors contributing to the high metabolic cost of RGO ambulation. Although ambulation may provide physical and psychological benefits, the high energy cost associated with orthotic ambulation currently prevents RGOs from being useful in daily living. The purpose of this case series was to investigate the dynamics of ambulation with RGOs, including characteristics that have not been previously presented for multiple subjects, to identify and better understand the potential causes of the high metabolic energy cost of RGO ambulation.

Methods

Motion data from five subjects (Table 1) were acquired at the Department of Veterans Affairs (VA) Chicago Motion Analysis Research Laboratory (VACMARL), which is equipped with an 8-camera digital RealTime motion capture system (Motion Analysis Corporation; Santa Rosa, California) for recording kinematic data and six force plates (Advanced Mechanical Technology, Inc; Watertown, Massachusetts) embedded flush in the floor of a 10 m walkway for measuring GRFs. Kinematic and kinetic data were sampled at 120 Hz. Subjects were included in the study if they regularly used an RGO because of lower-limb paralysis. Subjects under the age of 6 were excluded because they were not considered mature enough to follow the protocol. The Northwestern University Institutional Review Board approved this study, and informed consent was obtained from each individual before participation. Data were collected from subjects walking in their customary orthosis and using their customary walking aids (Table 1). Each subject underwent a clinical examination by a qualified orthotist who measured the passive range of motion (ROM) of the hip, knee, and ankle joints. The orthotist also measured hip flexion contractures and performed manual muscle tests on the lower-limb muscles as described by Kendall et al. (Table 2) [23]. Subjects voluntarily reported lesion level because access to their medical history was unavailable. In instances when subjects were uncertain about their lesion level, it was estimated from the results of their clinical examination.


Table 1.
Descriptive information of five study subjects.

Subject
No.
Sex
Age
 
Height
(cm)
Weight
(kg)
 
Pathology
 
Lesion
Level
RGO
Walking Aid

1
F
28
 
152
66
 
SCI
 
C7*
IRGO
Parallel bars
2
M
7
 
101
16
 
Spina bifida
 
T12*
IRGO
Crutches
3
M
21
 
173
71
 
SCI
 
T11*
ARGO
Anterior walker
4
F
12
 
129
36
 
Spina bifida
 
L3
IRGO
Crutches
5
F
8
 
92
18
 
Spina bifida
 
L3
IRGO
Reverse walker

*Reported by subject.
Based on evaluation by investigator.
ARGO = advanced reciprocating gait orthosis, C = cervical, F = female, IRGO = isocentric reciprocating gait orthosis, L = lumbar, M = male, RGO = reciprocating gait orthosis, SCI = spinal cord injury, T = thoracic.



Table 2.
Clinical measurements of study subjects' right and left hip, knee, and ankle joints and lower-limb muscle strengths.

Passive ROM (°)
Subject 1
Subject 2
Subject 3
Subject 4
Subject 5
Right
Left
Right
Left
Right
Left
Right
Left
Right
Left

Thomas Test
0
0
0
0
0
0
35
35
20
25
Hip Flexion
120
120
130
130
130
110
100
110
90
25
Hip Abduction (hip 0×)
30
30
50
50
25
25
20
20
0
10
   
 
 
 
 
 
 
 
 
 
Knee Flexion
WNL
WNL
WNL
WNL
130
130
NA
NA
WNL
WNL
Knee Extension (hip 0×)
5 HE
5 HE
0
0
5 HE
5 HE
25
20
5
10
   
 
 
 
 
 
 
 
 
 
Ankle Dorsiflexion (knee extended)
5 PF
5 PF
15
15
5
0
0
15
10
0
                     
Muscle Strength
Hip Flexion (hip 0×)
0
0
1
1
0
0
4
4
3
3
Hip Extension
(knee 0×)
0
0
0
0
0
0
NA
NA
0
0
Hip Extension
(knee 90×)
0
0
0
0
0
0
NA
NA
0
0
Hip Abduction
(hip 0×)
0
0
1
1
0
0
1
1
2
2
Knee Flexion (prone)
0
0
0
0
0
0
2
1
1
0
Knee Extension
(sitting)
0
0
0
0
0
0
3+
4
5
1

HE = hyperextension, NA = not available, PF = plantar flexion, ROM = range of motion, WNL = within normal limits.


We quantified motion of the body segments using passive reflective markers that were taped to the body and orthosis in the Helen Hayes configuration [24]. Markers were placed on the orthosis for the lower-limb segments and on the subject for the torso and upper-limb segments (Figure 1). Four markers were also placed on each walking aid. For dynamic trials, markers were located on the shoe over the dorsum of the foot between the second and third metatarsals immediately proximal to the metatarsal heads; on the shoe over the posterior calcaneus at the same height as the toe marker, lateral ankle joint, lateral knee joint, and right and left anterior superior iliac spines; and on the RGO over the sacrum. Thigh and shank markers were placed on the RGO. On the upper body, markers were placed on the acromion processes, lateral humeral condyles, and posterior wrist between the styloid processes. For static trials, markers were added to the medial ankle and knee joints. For consistency, the same laboratory personnel placed all markers on all subjects.


Figure 1. Example of marker placement used for all subjects.

Conventionally, force-plate measurements are only recorded when a foot or walking aid is exclusively and completely located on the force plate. Because of small step lengths or the use of walking aids, some of our subjects could not meet this criterion. Hence, force data were recorded when a foot or walking aid was completely and exclusively on a force plate during the single-support phase of stance. Force measurements were recorded from a minimum of five different foot strikes for each foot, unless the subject became too fatigued to continue the study. Anterior and posterior walkers were too large to fit on a single force plate. In those instances, force data for the anterior pair of walker legs were measured independ-ently from those of the posterior pair. Force data from each pair of legs were averaged separately, and we then summed the means to estimate the total GRF acting on the walker. For the subject who used parallel bars, force data were not measured.

EVa Real-Time software (Motion Analysis Corporation; Santa Rosa, California) was used to determine the 3-D position of each marker relative to the laboratory coordinate system during each frame of each trial. The raw coordinate data were filtered with a second-order bidirectional Butterworth low-pass filter with an effective cutoff frequency of 6 Hz, as suggested by Winter [25]. We used Orthotrak software (Motion Analysis Corporation, Santa Rosa, California) to calculate the joint angles, joint centers, and centers of mass (COMs) of body segments. Gait events were determined within Orthotrak.

We used custom programs (MATLAB, The MathWorks, Inc; Natick, Massachusetts) to calculate the velocities and accelerations of body segments and the forces, moments, and powers acting on the hips and shoulders. These calculations were based on a link segment model where each body segment, (thigh, foot, shank, etc.) was represented as a rigid link between two adjacent joints with a given mass and moment of inertia. The masses and radii of gyration for body segments were estimated from anthropomorphic data for nondisabled people [25] because corresponding data for people with lower-limb paralysis were not available. The motion of the segments and GRFs were used to calculate the minimum joint reaction forces. Forces and moments at the hip joints were calculated with traditional inverse dynamic equations. The sum of the forces acting on both shoulders was calculated from the measured motion of the trunk and the calculated forces acting at both hips as

Equation for the sum of the forces

where symbol for the f force. = forces, m = mass, a = acceleration, and g = the acceleration due to gravity. Both hip and shoulder forces created moments (M) about the trunk COM that were calculated in the sagittal plane according to

Equation for calculating the sagittal plane., (2)

where symbol for the distance from the trunk = the distance from the trunk COM to the stance hip joint or the midpoint between the shoulder joints and symbol for the f force. is the sum of the forces acting at the stance hip or both shoulders, respectively. We then used velocities to calculate the power generated at the hip joints during swing phase. The translational power generated at the hip was calculated as the dot product of the force vector acting at the stance hip joint and the linear velocity of the hip-joint center. Similarly, we calculated the rotational power generated at the hip by taking the dot product of the hip moment and the angular velocity of the hip joint.

Finally, all variables were ensemble averaged for each subject. For each variable, we normalized time by the duration of the gait cycle. Interpolated values from the variable were taken at fixed intervals on the normalized time scale. These values were then averaged at each interval over all the gait cycles. Data from RGO users were compared with those from a database of nondisabled ambulators.

Results

Temporal spatial data for each subject are shown in Table 3, along with the number of trials collected for each subject. None of the subjects asked to end the data collection prematurely because of fatigue. All subjects walked at freely selected speeds that were only about one-third of that typically adopted by nondisabled individuals. For all subjects, step length and cadence were found to be less than two-thirds of the mean value from nondisabled ambulators. RGO users tended to have substantially longer double-support phases compared with nondisabled persons (Figure 2).


Table 3.
Temporal spatial data and number of trials analyzed for each subject.

Subject
No.
Step Length (cm)
Cadence (steps/min)
Freely Selected Speed (m/s)
Trials Analyzed

1
24.6
38.6
0.19
6
2
40.7
56.9
0.39
5
3
27.0
17.4
0.08
11
4
33.2
60.4
0.34
9
5
23.1
72.3
0.29
10
Nondisabled
64.9
109.5
1.18
NA

NA = not available.



Figure 2. Mean sagittal plane kinematics for the trunk, shoulder, pelvis, and hip for all subjects from right heel strike to subsequent right heel strike.

Sagittal plane kinematics for the trunk, shoulders, pelvis, and hips are shown in Figure 2. Sagittal plane motion of the pelvis closely followed trunk motion, varying sinusoidally over time with a period equal to the step cycle (i.e., half a gait cycle). The RGO users walked with a continuously flexed trunk and moved their trunk through a larger flexion range than nondisabled ambulators. Generally, motion of the trunk and pelvis was out of phase with that exhibited by nondisabled individuals. Hip flexion occurred predominantly during single-support phases, with negligible motion during double-support phases. At the shoulder, subjects 2, 3, and 5 flexed their arms in a sinusoidal fashion like nondisabled individuals, except at twice the frequency.

Anterior, medial, and vertical GRFs acting on the stance foot and walking aids during single support are depicted in Figure 3. With the exception of subject 2, anterior GRFs acting on the stance foot of RGO users were small compared with nondisabled persons, remaining below 5 percent of body weight for most of single support. Overall, GRFs acting on the stance foot and walking aids of most subjects opposed forward motion during single support, with only two subjects (subjects 3 and 5) having anteriorly directed GRFs on the walking aids for any portion of single support. In the medial-lateral direction, most subjects had more laterally directed GRFs acting on their stance foot than nondisabled persons, with small lateral forces acting on the walking aids. Only two subjects (subjects 3 and 5) had medial GRFs acting on the walking aids during single support. All RGO users had smaller minimum vertical GRFs than nondisabled persons and experienced periods of single support during which they had less than half their body weight on the stance foot. The vertical GRFs acting on the walking aids reached a maximum of at least 50 percent of body weight.


Figure 3. Mean (a) anterior-posterior, (b) medial-lateral, and (c) vertical ground reaction forces (GRFs) acting on the stance foot and walking aids during single-support phase of stance for each subject. For walking aid data, sum of GRFs acting on both crutches or on all walker legs during single-support phase are shown.

Figure 4 illustrates the moments about the trunk COM caused by forces acting at the shoulders and the hips during single support. Forces acting at the shoulders promoted trunk extension moments for all subjects, while forces acting at the hips promoted trunk flexion moments for all subjects with the exception of subject 2. Figure 5 illustrates the moments generated at the hip joints during swing phase. While nondisabled persons experience hip flexion moments at the beginning of swing, all the RGO users experienced hip extension moments. Hip flexion moments tended to occur before midstance and were small than those of nondisabled persons.


Figure 4. Mean moments about trunk center of mass in sagittal plane caused by joint reaction forces at (a) shoulder and (b) hip during single-support phase for each subject.

Figure 5 .Mean moments occurring at hip in sagittal plane during swing phase for each subject. Gray band indicates hip moments (mean plus-minus 1 standard deviation) from nondisabled persons.

Figure 6 depicts the power generated at the hip during swing phase and the rate of work done on the leg by hip-joint reaction forces during swing phase. The power generated from hip moments was small and dissipative compared with the power from hip forces for most subjects. The power from hip forces demonstrated a sinusoidal pattern.


Figure 6. Mean sagittal plane power from (a) hip moments and (b) hip forces during swing phase for each subject.
Discussion

For this case series, we investigated the gait dynamics of RGO users to identify potential causes for the high metabolic energy costs that have been so frequently reported in the literature [17-19]. The subjects tested for this study reflected the variability typically observed in the population of RGO users with respect to age, pathology, walking aids used, etc. The data included variables that have not been previously presented for multiple subjects, such as sagittal plane trunk kinematics and hip moments and powers.

Despite substantial heterogeneity in the study sample, many gait characteristics were consistent. It was demonstrated that all five RGO users walked with a flexed trunk. Pelvic motion was coupled to that of the trunk by the RGO, and hip flexion angle remained constant, indicating that both legs were rotating along with the pelvis while maintaining contact with the ground. At the beginning of single support, the RGO users transferred the majority of their weight from the stance leg to the walking aids and elevated the swing-side pelvis upward to facilitate foot clearance by tilting the trunk laterally over the stance leg [18-19,21-22]. The trunk and pelvis also extended during this phase, which pushed the pelvis forward and extended the stance leg hip. This motion produced flexion of the swing leg hip. The swing leg then contacted the ground and the cycle began again.

All RGO users in this study demonstrated a reciprocating gait when ambulating with the RGO. Although a reciprocating gait is considered distinct from a swing-through gait, they appear to share similar dynamic characteristics. The motions of the arms and trunk are similar if the swing phase of the reciprocating gait is likened to the flight phase of the swing-through gait. The trunk flexes forward during double support and extends backward during swing/flight. Walking aids are moved forward during double support and used to bear a large portion of body weight during swing/flight. In people with lower-limb paralysis, the upper body appears to produce substantial power for both gaits. This finding may explain why Thomas et al. did not find a significant difference in oxygen cost between children who used a swing-through gait pattern and children who used a reciprocating pattern with an RGO [26]. Based on these considerations, perhaps a reciprocal gait could be considered a modified form of swing-through gait that alternately drags one leg behind the other.

Although the RGO renders the stance leg suitable for weight bearing by passively holding the lower limbs and torso upright, RGO users continue to bear a large portion of their body weight through the arms during single-limb support. Weight bearing through the arms likely contributes to the high energy expenditure associated with RGO ambulation, since studies have shown that upper-body musculature produces power less efficiently than lower-body musculature [27-29]. Our data suggest that the trunk posture of RGO users may encourage arm loading. All subjects in this study walked with a flexed trunk, extending during single support presumably to flex the swing leg. With the trunk flexed, forces at the hip promoted trunk flexion moments, but forces at the shoulder promoted trunk extension moments. Therefore, for RGO users to extend their trunk, forces at the shoulder must be increased to counteract the trunk flexion moments created by forces at the hip. This trunk extension is accomplished by users shifting their weight onto the walking aids. The net effect of this arm loading is that moments about the trunk are approximately balanced (Figure 4). Although, the moments created about the trunk COM by shoulder joint reaction forces are not on their own large enough to extend the trunk, they do contribute. Upper-body muscle action, which was not reported in this study, may also contribute to trunk extension.

Trunk orientation also alters the moment arm between the trunk COM and the hip and shoulder joints. If the trunk were in an extended position, the moment arm would change so that an upward force from the hip joint would lead to the desired trunk extension motion. This orientation may encourage weight-bearing through the stance leg rather than the walking aids, which in turn could decrease metabolic energy expenditure. Though not presently clear, RGO users may adopt a flexed trunk to ensure stability by increasing the base of support created by their feet and walking aids. The choice of walking aid and user technique should be further explored with respect to metabolic energy expenditure.

Trunk posture may also affect function of the reciprocal link, which is intended to harness flexion at one hip to facilitate extension of the other hip, and vice versa. However, since the trunk and pelvis are rigidly linked by the RGO, trunk flexion produces stance hip flexion, which in turn encourages swing hip extension through engagement of the reciprocal link. Our data demonstrate that for all subjects, the stance leg hip was flexed for most of single support and that an extension moment acted on the hip at the beginning of swing phase. This extension moment is antagonistic to the goal of swing, which is to advance the swing leg with hip flexion, and contradicts the intended purpose of the reciprocal link.

Based on an analysis of the tension generated in the cables that form the reciprocal link of an RGO, Dall et al. have also argued that the link does not assist in leg swing as traditionally thought [30]. Our results indicated that all subjects experienced small hip flexion moments compared with nondisabled persons. Without active hip flexors (or the presence of weak hip flexors-subjects 4 and 5), these hip flexion moments are assumed to be the result of the reciprocal link. However, the moment is too small to contribute substantially to swing, with the power generated by moments at the hip being much smaller than the power generated by hip-joint forces. Apparently, trunk and pelvis motion contributes more to leg swing than elements of the orthosis such as the reciprocal link. Hence, our results concur with those of Dall et al. in suggesting that the reciprocal link is minimally important in leg swing [30].

As with many mechanical systems, a certain degree of backlash is present in the reciprocal link. Ballistic movement of the swing leg within the backlash of the reciprocal link may help explain the smaller moments calculated at the hip and the larger power generated by the hip-joint reaction forces than by hip moments. The motion of the pelvis and the force of gravity may flex the leg before the reciprocal link can fully engage. Trunk flexion may predispose the link to hip extension so that the link has to overcome the entire extent of the backlash before it can promote hip flexion. If the trunk were extended at the beginning of swing phase, the reciprocal link may be engaged in flexion and contribute more to leg swing.

We do not advocate that the reciprocal link is completely without merit; our current knowledge about the function of the reciprocal link is too limited to assess definitively. Several authors have hypothesized that the link may have some utility during the double-support phase of walking [17,30]. For example, Dall et al. suggested that the link may help keep the trunk upright by preventing bilateral hip flexion [30]. Unfortunately, this study cannot contribute further to exploring the action of the reciprocal link during double support because of insufficient data during this gait cycle period. In some of our subjects, because of small step lengths or the use of walking aids, force-plate measurements could only be recorded when a foot or walking aid was exclusively and completely located on the force plate, i.e., during single support. Additional studies are required that specifically investigate the role of the reciprocal link in RGO ambulation.

Like many previous studies of RGO ambulation, a limitation of this case series was the small and heterogeneous sample population. Having such a diverse population introduces a multitude of uncontrolled variables, including the different strength to mass ratios between adults and children, different passive ROMs of the joints, varying degrees of spasticity, different levels of muscle control and sensation, and different bases of support and maneuverability provided by the various walking aides. While little research has been conducted to quantify the effects of these different variables on the gait mechanics of RGO users, one particular study reported a significant relationship between lesion level and walking speed, hip ROM, and peak crutch force [17]. Therefore, we recognize that these uncontrolled variables can interfere with the interpretation of the results from this investigation. However, we believe that the simplest explanation for the observed consistency in certain gait characteristics across this study's sample population comes from the traits the subjects have in common and not from their differences. Indeed, with such a diverse population, the list of common traits among the subjects is small but vital, consisting of the RGO itself. In this way, the diversity in the subject sample along with the consistency of gait characteristics increases this study's generalizability because it suggests that aspects of ambulation exist with an RGO that are consistent across RGO users regardless of age, lesion level, type of RGO, and walking aid used.

Sources of measurement error included marker placement and assumptions regarding anthropometry. Marker placement on the pelvis was particularly difficult for the subjects who used an isocentric RGO (IRGO), because the corset and rocker bar prevented direct placement of a marker on the sacrum as required by the Helen Hayes marker set [24]. Since the pivot point of the IRGO rocker bar was located over the sacrum, the sacral marker was placed on the pivot, separating the sacral marker from the sacrum by about 3 cm. As a result, relative motion between the orthosis and the subject could affect measurements of pelvic tilt and hip flexion and, consequently, introduce error in the calculations of hip flexion moments and rotational hip-joint power. However, the average relative motion between the sacral marker on the orthosis and the pelvic markers on the subjects was found to be <1 cm, which is comparable with the relative motion found between two markers placed directly on the skin of the lower limbs of nondisabled people [31]. Therefore, the error introduced by the marker placement used in this study is no greater than that in gait analyses that use the traditional Helen Hayes marker set.

We used anthropomorphic approximations for nondisabled people to estimate the masses, COMs, and radii of gyration of the lower limbs because such information could not be found for people with lower-limb paralysis. Atrophy of the lower limbs due to disuse renders these estimates prone to error, particularly overestimation of segment masses. Overestimating the leg mass inflates the hip-joint forces and moments and, consequently, the power generated at the hip. However, the possibility that hip moments may actually be smaller than those calculated strengthens the argument that small moments at the hip indicate limited action of the reciprocal link in RGO ambulation. The errors associated with inaccurate COM and radii of gyration are more difficult to predict. If accelerations are small, errors are probably not as significant.

Although none of our subjects requested a rest period during the data collection trials, the known exhaustive nature of ambulating with RGOs prevents the dismissal of fatigue as a possible source of error. However, little is known about how fatigue affects the gait pattern of RGO users.

The results of this case series suggest a number of additional investigations are required to further increase our understanding of RGO gait. Studies should further investigate the effects of posture on arm loading, energy expenditure, and the reciprocal link to determine if trunk flexion contributes to arm loading and increases metabolic energy expenditure. Additionally, we need to determine whether users who ambulate with an extended trunk posture may increase hip flexion moments during swing through action of the reciprocal link. Furthermore, backlash within the reciprocal link and its effect on hip moments should also be investigated. This additional information may improve RGO design or user technique and therefore result in more functional and efficient ambulation with RGOs.

Conclusions

Analyses of the dynamics of ambulation with RGOs indicate consistent gait characteristics across users, such as persistent trunk flexion and the pattern of load bearing during the single-support phase of stance. The results of this case series suggest that the relationship between posture, forces acting on the walking aids, and the action of the reciprocal link should be explored further because these factors likely contribute to the high metabolic cost of ambulation with an RGO.

ACKNOWLEDGMENTS

Author Contributions:

Study concept and design: W. B. Johnson.

Analysis and interpretation of data: W. B. Johnson, S. A. Gard, S. Fatone.

Drafting of manuscript: S. Fatone, W. B. Johnson.

Critical revision of manuscript for important intellectual content: S. A. Gard.

Financial Disclosures: The authors have declared that no competing interests exist.

Funding/Support: This material was based on work supported by the National Institute on Disability and Rehabilitation Research of the U.S. Department of Education under grant H133E030030. The opinions in this publication are those of the grantee and do not necessarily reflect those of the U.S. Department of Education.

Additional Contributions: We acknowledge the use of the VACMARL of the Jesse Brown VA Medical Center, Chicago, Illinois, and the assistance of Rebecca Stine, MS, in collecting the data. We would also like to thank Luciano Dias, MD; Shubhra (Sue) Mukherjee, MD; Nicholas Gryfakis, MS; and the staff of the Children's Memorial Hospital spina bifida clinic, Chicago, Illinois, for helping to recruit subjects.

Participant Follow-Up: The authors do not plan to inform participants of the publication of this study.

REFERENCES
1. Mazur JM, Shurtleff D, Menelaus M, Colliver J. Orthopaedic management of high-level spina bifida. Early walking compared with early use of a wheelchair. J Bone Joint Surg Am. 1989;71(1):56-61. [PMID: 2643608]
2. Rosenstein BD, Greene WB, Herrington RT, Blum AS. Bone density in myelomeningocele: the effects of ambulatory status and other factors. Dev Med Child Neurol. 1987; 29(4):486-94. [PMID: 3678627]
3. Bromley I. Tetraplegia and paraplegia: a guide for physiotherapists. 2nd ed. New York (NY): Churchill Livingstone; 1981.
4. McAdam R, Natvig H. Stair climbing and ability to work for paraplegics with complete lesions-a sixteen-year follow-up. Paraplegia. 1980;18(3):197-203. [PMID: 7413242]
5. Rose GK, Henshwa JT. A swivel walker for paraplegics: medical and technical considerations. Biomed Eng. 1972; 7(9-2):420-25. [PMID: 4680587]
6. Guest RS, Klose KJ, Needham-Shropshire BM, Jacobs PL. Evaluation of a training program for persons with SCI paraplegia using the Parastep 1 ambulation system: Part 4. Effect on physical self-concept and depression. Arch Phys Med Rehabil. 1997;78(8):804-7. [PMID: 9344297]
DOI:10.1016/S0003-9993(97)90191-X
7. Fatone S. A review of the literature pertaining to KAFOs and HKAFOs for ambulation. J Prosthet Orthot. 2006; 18(7):P137-68. DOI:10.1097/00008526-200606001-00003
8. Douglas R, Larson PF, D'Ambrosia R, McCall R. The LSU reciprocating gait orthosis. Orthopedics. 1983;6:834-39.
9. Butler PB, Major R. The ParaWalker: A rational approach to the provision of reciprocal ambulation for paraplegic patients. Physiotherapy. 1987;73(8):393-97.
10. Kirtley C, McKay SK. Total design of the "Walkabout": a new paraplegic walking orthosis. in: Seventh World Congress of the International Society for Prosthetics and Orthotics; 1992 Jun 28-Jul 3; Chicago, Illinois. Alexandria (VA): International Society for Prosthetics and Orthotics; 1992. p. 39.
11. Katz-Leurer M, Weber C, Smerling-Kerem J, Rottem H, Meyer S. Prescribing the reciprocal gait orthosis for myelomeningocele children: a different approach and clinical outcome. Pediatr Rehabil. 2004;7:(2)105-9.
[PMID: 15204581]
DOI:10.1080/13638490310001654745
12. Sykes L, Edwards J, Powell ES, Ross ER. The reciprocating gait orthosis: long-term usage patterns. Arch Phys Med Rehabil. 1995;76(8):779-83. [PMID: 7632135]
DOI:10.1016/S0003-9993(95)80534-6
13. Franceschini M, Baratta S, Zampolini M, Loria D, Lotta S. Reciprocating gait orthoses: a multicenter study of their use by spinal cord injured patients. Arch Phys Med Rehabil. 1997;78(6):582-86. [PMID: 9196464]
DOI:10.1016/S0003-9993(97)90422-6
14. Middleton JW, Yeo JD, Blanch L, Vare V, Peterson K, Brigden K. Clinical evaluation of a new orthosis, the `walkabout,' for restoration of functional standing and short distance mobility in spinal paralysed individuals. Spinal Cord. 1997;35(9):574-79. [PMID: 9300961]
DOI:10.1038/sj.sc.3100459
15. Scivoletto G , Petrelli A, Lucente LD, Giannantoni A, Fuoco U, D'Ambrosio F, Filippini V. One year follow up of spinal cord injury patients using a reciprocating gait orthosis: preliminary report. Spinal Cord. 2000;38(9):555-58.
[PMID: 11035478]
DOI:10.1038/sj.sc.3101047
16. Jaspers P, Peeraer L, van Petegem W, van der Perre G. The use of an advanced reciprocating gait orthosis by paraplegic individuals: a follow-up study. Spinal Cord. 1997; 35(9):585-89. [PMID: 9300963]
DOI:10.1038/sj.sc.3100462
17. Hirokawa S, Grimm M, Le T, Solomonow M, Baratta RV, Shoji H, D'Ambrosia RD. Energy consumption in paraplegic ambulation using the reciprocating gait orthosis and electric stimulation of the thigh muscles. Arch Phys Med Rehabil. 1990;71(9):687-94. [PMID: 2375676]
18. Bernardi M, Canale I, Castellano V, Di Filippo L, Felici F, Marchetti M. The efficiency of walking of paraplegic patients using a reciprocating gait orthosis. Paraplegia. 1995; 33(7):409-15. [PMID: 7478731]
19. Kawashima N, Taguchi D, Nakazawa K, Akai M. Effect of lesion level on the orthotic gait performance in individuals with complete paraplegia. Spinal Cord. 2006;44(8):487-94. Erratum in: Spinal Cord. 2006;44(8):522.
[PMID: 16550216]
DOI:10.1038/sj.sc.3101916
20. Bernardi M, Macaluso A, Sproviero E, Catellano V, Coratella D, Felici F, Rodio A, Piacentini MF, Marchetti M, Ditunno JF Jr. Cost of walking and locomotor impairment. J Electromyogr Kinesiol. 1999;9(2):149-57. Erratum in: J Electromyogr Kinesiol. 1999;9(3):235. [PMID: 10098715]
DOI:10.1016/S1050-6411(98)00046-7
21. Whittle MW, Cochrane GM. A comparative evaluation of the hip guidance orthosis (HGO) and the reciprocating gait orthosis (RGO). Health Equipment Information No. 192. London (UK): National Health Service Procurement Directorate; 1989.
22. Tashman S, Zajac FE, Perkash I. Modeling and simulation of paraplegic ambulation in a reciprocating gait orthosis. J Biomech Eng. 1995;117(3):300-308. [PMID: 8618383]
DOI:10.1115/1.2794185
23. Kendall FP, McCreary EK, Provance PG. Muscles testing and function: With posture and pain. 4th ed. Baltimore (MD): Williams & Wilkins; 1993.
24. Kadaba MP, Ramakrishnan HK, Wootten ME. Measurement of lower extremity kinematics during level walking. J Orthop Res. 1990;8(3):383-92. [PMID: 2324857]
DOI:10.1002/jor.1100080310
25. Winter DA. Biomechanics and motor control of human movement. 2nd ed. New York (NY): John Wiley and Sons, Inc; 1990.
26. Thomas SS, Buckon CE, Melchionni J, Magnusson M, Aiona MD. Longitudinal assessment of oxygen cost and velocity in children with myelomeningocele: comparison of the hip-knee-ankle-foot orthosis and the reciprocating gait orthosis. J Pediatr Orthop. 2001;21(6):798-803.
[PMID: 11675558]
DOI:10.1097/00004694-200111000-00019
27. Glasheen JW, McMahon TA. Arms are different from legs: Mechanics and energetics of human hand-running. J Appl Physiol. 1995;78(4):1280-87. [PMID: 7615434]
28. Kang J, Robertson RJ, Goss FL, Dasilva SG  , Suminski RR, Utter AC, Zoeller RF, Metz KF. Metabolic efficiency during arm and leg exercise at the same relative intensities. Med Sci Sports Exerc. 1997;29(3):377-82. [PMID: 9139177]
DOI:10.1097/00005768-199703000-00013
29. Vokac Z, Bell H, Bautz-Holter E, Rodahl K. Oxygen uptake/heart rate relationship in leg and arm exercise, sitting and standing. J Appl Physiol. 1975;39(1):54-59.
[PMID: 1150592]
30. Dall PM, Müller B, Stallard I, Edwards J, Granat MH. The functional use of the reciprocal hip mechanism during gait for paraplegic patients walking in the Louisiana State University reciprocating gait orthosis. Prosthet Orthot Int. 1999; 23(2):152-62. [PMID: 10493143]
31. Cappozzo A, Catani F, Leardini A, Benedetti MG , Della Croce UD. Position and orientation in space of bones during movement: Experimental artefacts. Clin Biomech (Bristol, Avon). 1996;11(2):90-100. [PMID: 11415604]
DOI:10.1016/0268-0033(95)00046-1
Submitted for publication January 31, 2008. Accepted in revised form August 29, 2008.

Go to TOP

Go to the Table of Contents of Vol. 46 No. 3

Last Reviewed or Updated  Friday, August 28, 2009 7:32 AM

Valid XHTML 1.0 Transitional