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Objective: The aim of this study was to identify the effect of induced knee flexion during gait on the kinematics and temporal-spatial parameters during walking by a patient with spinal cord injury (SCI) through the application of an isocentric reciprocating gait orthosis (IRGO) with a powered knee mechanism. Methods: Two orthoses were considered and evaluated for an ISCI subject with a T8 level of injury. An IRGO was initially manufactured by incorporating drop lock knee joints and was fabricated with custom molded AFOs to block ankle motion. This orthosis was also adapted with electrically-activated knee joints to provide active knee extension and flexion when disengaged. Results: Walking speed, stride length and cadence were increased 37.5%, 11% and 26%, respectively with the new orthosis as compared to using the IRGO. The vertical and horizontal compensatory motions reduced compared to mechanical IRGO. At end of stance phase, knee joint flexion was 37.5° for the AKIRGO compared to 7° of movement when walking with the IRGO. The overall pattern of walking produced was comparable to that of normal human walking. Conclusion: Knee flexion during swing phase resulted in an improved gait performance and also reduction in compensatory motions when compared to a mechanical IRGO.

Keywords: Gait, powered knee mechanism, spinal cord injury

Introduction

Various types of orthoses have been designed specifically for use by patients suffering from paraplegia. The traditional design of orthosis known as the knee ankle foot orthosis (KAFO) is the most commonly supplied orthosis and is

normally used bilaterally. The addition of a pelvic band and orthotic hip joints and a thoracolumbar superstructure in patients with high level lesions to control the trunk and pelvis motion is known as a hip knee ankle foot orthosis (HKAFO). Patients can walk with these devices with their knees locked and using their trunk musculature and crutches to facilitate reciprocal walking. The disadvantage of these orthoses is the ungainly gait associated with them due to the knees being locked and the high energy consumption of walking needed to produce the reciprocating motion at the hips, plus a very low walking speed [1].

There was therefore a need to develop orthoses which provided reciprocal walking by applying a linkage between the hip joints, rather than being independently controlled by the patient, whilst still keeping the legs in extension. This led to the development of reciprocating gait orthoses (RGOs) [2–4] which provided reciprocal walking by using either a

CASE STUDY

The effect of an isocentric reciprocating gait orthosis incorporating an active knee mechanism on the gait of a spinal cord injury patient: A single case study

Mokhtar Arazpour1, Monireh Ahmadi Bani1, Ahmad Chitsazan2, Farhad Tabatabai Ghomshe1, Reza Vahab Kashani1 & Stephen William Hutchins3

1University of Social Welfare and Rehabilitation Science, Orthotics and Prosthetics, Tehran, Iran, Islamic Republic of, 2Amirkabir University of Technology (Tehran polytechnic), biomedical engineering, Tehran, Iran, Islamic Republic of, and 3University of Salford, IHSCR, Faculty of Health and Social Care, Salford, UK

Correspondence: Reza Vahab Kashani, University of Social Welfare and Rehabilitation Science, Tehran, Iran, Islamic Republic of. E-mail: Vahab_kashani@yahoo.com

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• Powered orthosis could be used by spinal cord injury subjects.

• A major advantage of this new orthotic mechanism was regeneration of knee movement closer to that of normal human walking.

• The IRGO with a powered knee joint mechanism improved the speed of walking, step length, cadence and vertical displacement in a spinal cord injury patient which also produced near-normal knee joint angle patterns during gait.

Implications for Rehabilitation

(Accepted April 2012)

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linkage or cables connecting the orthotic hip joints. In this way, whilst one hip was flexing, the contralateral was forced to extend. Another version was developed which used gravity and low friction laterally stable orthotic hip joints to allow the hip joints to flex during swing phase using gravitational forces, known as the hip guidance orthoses (HGO) [5]. The advanced reciprocating gait orthosis (ARGO) was a further development which used springs to aid sit to stand.

All these have historically enabled paraplegic patients to ambulate. However, an excessively high energy consumption due to the need to use trunk muscles via crutches to ambulate, and high loading on upper limb joints has been demonstrated by subjects with spinal cord injury (SCI) when walking with such devices [6–11]. In addition, they were all designed to hold the knees locked in extension which meant difficulty in swing through whilst providing toe clearance.

In an attempt to reduce these problems, paraplegic patients routinely use lateral tilt or lifting of the trunk as compensa-tory motions to provide propulsion. One of the major reasons for these problems is positioning of the knee in extension and locking of this joint during ambulation [12]. Improvements in the mechanical design [13], the development of hybrid orthoses [14,15] and also the advent of active powered knee joints [16,17] have been proposed as conservative approaches to solve the problem of providing knee flexion during swing phase of gait by paraplegic patients.

Many studies have focused on improvement of orthosis design. Stallard et al. increased lateral stiffness in HGOs and reported that the physiologic cost index (PCI) of patients was reduced [18,19]. Ljzerman et al. demonstrated that when fron-tal plane alignment whilst using an ARGO was altered from 6 degrees of adduction to neutral or 3 degrees of abduction, crutch forces measured during walking decreased [19]. Winchester et al. reported that the PCI of gait was 28% lower in the IRGO as compared to RGO due to its reciprocating link [20]. Harvey et al. also announced the rate of this parameter was lower in the IRGO compared to the walkabout orthosis [21].

Greene and Grant observed that knee flexion produced more ground clearance and fewer compensatory motions compared to a fixed extended knee during walking [13]. Edwards and Bataweel [14] demonstrated that lack of knee flexion during swing phase of gait was the main reason for orthosis rejection and production of fatigue when used by paraplegic subjects. They subsequently developed a weight bearing control knee joint by adapting an ARGO in con-junction with use of functional electrical stimulation (FES), which resulted in a reduction of energy consumption by a T6 paraplegic subject. However, Baardman et al. reported no reduction in energy consumption and compensatory motions using a knee flexion mechanism in an ARGO [22]. Yang et al. reported that the efficacy of walking was optimized when sub-jects used knee flexion, ankle plantar flexion and a 2:1 ratio of hip flexion to extension during walking [23].

Active orthoses have the potential to reduce energy con-sumption and improve the aesthetics of walking by paraplegic patients [17,24]. The use of McKibben muscles (pneumatic artificial muscles) in KAFOs [25] and IRGOs [16], as well as motorized SCKAFOs [26] and motorized ARGOs [27]

are examples of activated orthoses previously developed. Improvement in walking speed and step length has been reported in spinal cord injury patients when walking with a motorized knee joint in an ARGO [27]. However, most previ-ously developed orthoses have been bulky and heavy. The use of lighter-weight orthoses, using modular and energy-efficient electrically actuators, could feasibly improve the efficiency of walking by SCI patients.

This present study focused on the effect of induced knee flexion in a single SCI subject during gait, and formed part of a larger study in the design and construction of a novel powered orthosis. The purpose of this study was to identify the effect of an activated knee joint mechanism added to an IRGO on the speed of walking, step length, cadence, compensatory motions and sagital plane knee angle when utilized by a single SCI subject.

Method

Subject and experimental protocolThe subject was a 22-year-old woman with a T8 incomplete spinal cord injury, who had been injured 4 years before this evaluation. The patient was initially fitted with an IRGO with drop lock knee joints that were attached to custom molded AFOs manufactured using 5 mm copolymer polypropylene. She subsequently used the orthosis in combination with a walking frame periodically in her home and during physi-cal therapy sessions. Walking with this orthosis proved to be more comfortable than the HKAFO which had been used pre-viously, as ambulation with the HKAFO required the utiliza-tion of excessive compensatory motions and a perceived high energy cost. In order to further improve her gait, an active electrically powered knee joint actuator was also developed (Figure 1), which was specifically designed to be attached to the mechanical knee joints of the IRGO.

Motorized knee IRGO prototypeThe IRGO (initially proposed by Motlock et al.) used a rocker bar link which greatly reduced the inherent friction in the system in preference to the previously-used cable system. Its structure has been shown to be simple, lightweight and comfortable when used by paraplegic patients [19,20] and was therefore chosen for use in this study. To more closely match the kinematics of normal human locomotion at the knee, a powered orthotic knee joint actuator was developed using a Maxon Motor EC30 actuator (Maxon, Switzerland) with a planetary gearbox utilizing a reduction ratio of 110. This actuator provided adequate torque to provide joint rotation in the lower limbs of the SCI subject during walking. One rechargeable 24 V battery (Lipo Battery, Thunder Power RC G6 Pro Lite 25C 5400 mAh 6-Cell/6S) was used in this orthosis. The operation of the motor was controlled via a switch. The right and left switches (for right and left knee joints) were placed on the handle of the walker. The knee joint therefore moved when the appropriate switch was pushed. The actuator held the knee in extension in stance and then allowed flexion during swing. The total weight of prototype of orthosis was 8.9 kg.

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Analysis proceduresA calibrated 6-camera Vicon 370 motion analysis system (Oxford Metrics, UK) with a frequency of 100 HZ was used to collect bilateral lower limb kinematics via capturing the loca-tions of reflective markers placed on the orthosis and trunk. Reflective markers were used in the lower extremity and on the trunk using the gait analysis. Markers were placed bilater-ally on, or on the othosis directly over the point of the fol-lowing areas: the greater trochanter, the lateral condyle of the femur, the fibular head, the lateral malleolus, the point above the centre of the second metatarsal on the toe box of the shoe, the ASIS, the superior/posterior edge of the calcaneus (on the heel counter of the shoe), and the jugular notch, the spinous process of the seventh cervical vertebrae and on the acromio-clavicular joints. Lower extremity markers were placed on the uprights of the orthosis or the thermoplastic superstructure directly over the anatomical points.

The patient used the powered knee IRGO for 3 months to learn how to walk with the new orthosis, following a period of training and accommodation, prior to agreeing to be evalu-ated using clinical gait analysis. Through tests, the SCI patient demonstrated she could walk safely with the new powered orthosis. Physical therapy sessions were conducted during training with powered knee orthosis.

The study compared the mechanical IRGO which used drop lock knee joints to the powered IRGO which used elec-trically motorized knee joints. The subject walked along a 6 m walkway when wearing each of the two types of orthosis in turn. Before data acquisition, the subject donned the ortho-ses and performed practice walks in a straight path along the walk way. After the subject announced she was ready to pro-vide test walks, she undertook three gait analysis evaluations. It was ensured that the subject stepped on the same platform with the same foot during data collection. Subjects walked

with a hand-held walking frame in this study for safety. Walking experiments were performed in the Biomechanics Laboratory of ergonomic department of University of Social Welfare and Rehabilitation Science. Patient performed one set of walking trials in the IRGO and then returned for a second set of walking trials once the orthosis had been adapted with the actuator. The subject volunteered for the study and was allowed to exclude herself from the study at any time. Before participation in the study, the subject read and approved a statement acknowledging informed consent. Ethics commit-tee of University of Social Welfare and Rehabilitation Science approved performance of this study.

Results

When the paraplegic subject walked with the activated knee IRGO (AKIRGO), she anecdotaly experienced less effort to walk when compared to the mechanical IRGO. The mean spatio-temporal parameters for the subject when wearing the IRGO and AKIRGO are showed in Table I. Walking speed was 37.5% faster with new orthosis as compared to using IRGO. Walking with the AKIRGO showed in an 11% longer stride length. The cadence of walking with the AKIRGO increased by 26% and the vertical and horizontal displacement of the pelvis reduced compared to mechanical IRGO (Figure 2).

In comparing the means of knee angle over the trials in walking with IRGO and the AKIRGO, at end of stance phase (approximately 45% of the gait cycle), knee joint flexion was 37.5° for the AKIRGO compared to 7° movement when walk-ing with the IRGO. Knee flexion during swing increased in walking with the new AKIRGO compared to mechanical IRGO (Table II and Figure 3).

Discussion

Knee flexion is one of the mechanisms used in smoothing the pathway of the body’s COM and decreasing the energy consumption of walking [23,28,29]. A major advantage of this new orthotic mechanism was regeneration of knee movement closer to that of normal human walking. Our orthosis was developed for use by paraplegic patients. These subjects require high stability and safety in stance, and therefore a knee mechanism designed to lock during stance and provide knee joint motion during swing phase whilst incorporated within a proven orthotic device was thought to be a logical development.

Figure 1. Activated knee mechanism that used with IRGO.

Table I. Spatio-temporal parameters with IRGO and powered IRGO (± standard deviation).

Walking with IRGO

Walking with IRGO with

activated knee joints Averaged change

Speed of walking (m/s)

0.24 ± 0.01 0.33 ± 0.03 37.5% increase

Step length (cm) 38.4 ± 1.7 41.5 ± 3.0 11% increaseCadence (steps/min)

19 ± 15.6 24 ± 12.7 26% increase

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The results demonstrated that, at swing phase, the knees were at near the normal flexion angle of 37.5°. This strategy may have been responsible for reducing pelvic elevation and pelvic lateral swing in walking of the SCI patient. A previous study by Ferrarin et al. demonstrated an 8 degree reduction of vertical displacement of the COM when paraplegic patients wore a new hip joint in an RGO [30]. Ohta et al. reported only reduction of vertical and horizontal compensatory motions

when a powered hip actuator in an ARGO was activated, but the influence of a powered knee joint on compensatory motions was not assessed directly [27].

Paraplegic patients do not have the facility of knee flexion or extension during walking with current mechanical orthoses (e.g. RGOs, HKAFO), but in the case of AKIRGO, knee joint movements were enabled during swing phase of gait. A maximum knee flexion angle of 37.5° was attained with the new orthosis, whilst during walking with the IRGO; this parameter was reduced to 7° flexion due to deformation of orthosis. This corresponds with the results demonstrated by Kim et al., who reported the mean of this parameter using the UKJ-PGO to be 43 ± 5 degrees [16].

The speed of walking was substantialy altered by the pow-ered compared to the unpowered IRGO, as the use of the external power source increased gait velocity. This parameter

Table II. Knee angle (degree) with IRGO and IRGO with activated knee mechanism.

Walking with IRGOWalking with IRGO with

activated knee mechanismRight Left Mean Right Left mean

Extension 6° 8° 7° 8° 10° 9°Flexion 0° 0° 0° 37° 38° 37.5°

Figure 3. Flexion and extension of knee joint for SCI patient walking with mechanical IRGO and IRGO with activated knee mechanism.

Figure 2. Lateral and vertical compensatory motion for SCI patient walking with mechanical IRGO and IRGO with activated knee mechanism.

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has been quoted as being 1.13 m/s in normal walking [31]. Walking speed has been shown to increase by 16% in a pow-ered gait orthosis (PGO) using unlockable knee joints com-pared to locked knee joint [16], and in a separate study, the mean walking velocity was increased when comparing an IRGO with the knees in the locked position to one adapted with stance control knee joints from 0.11 m/s to 0.23 m/s [32].

One of the drawbacks of walking with a mechanical RGO is the need for forward trunk inclination. Forward excursion of trunk was only slightly lower in the powered IRGO walking test condition in this study, while speed of walking was increased. An increase in the step length observed in this study, agrees with results demonstrated by Rasmussen et al., who reported step length was greater in an IRGO with SCOs added when compared to an IRGO with locked knees [31]. Ohta et al. also reported that a powered ARGO increased this parameter as compared to mechanical ARGO in 5 paraplegic patients [27].

Walking cadence in normal human gait is 100 ± 10 steps/min [32]. Due to their physical condition, most paraplegic patients can only walk with assistive devices. When the IRGO was used, this mean was 19 steps/min, while in the AKIRGO condition this mean increased by 26%. This value dem-onstrated in one study using a PGO with locked knee joint was 33 ± 2 steps/min and increased 10% when walking with unlockable knee joints [15].

Evaluation of the new system presented in this study gave the research group confidence to expand the walking to tri-als to a further group of SCI volunteer subjects. This should also include the analysis of physiological measurements and upper limb loadings when comparing the AKIRGO to the mechanical IRGO and also to demonstrate the advantages of the activated knee joint mechanism for spinal cord injury patient ambulation. Using an IRGO with an activated knee joint mechanism anecdotaly reduced patient’s efforts to walk. Evaluation of energy consumption in SCI subjects and also crutch forces when walking with the PAIRGO will form the next phase of this research.

Clinical relevanceIn this study, improvements in the speed of walking, step length, cadence and vertical displacement in a spinal cord injury patient were observed when walking with the IRGO with a powered knee joint mechanism which also produced near-normal knee joint angle patterns during gait.

According to the efficacy of this new joint mechanism on improving gait performance parameters, it is anticipated that this activated orthosis will improve the energy consumption of gait when compared to an un-adapted IRGO. In future clinical work, it is planned to synchronize powered hip and activated knee joints to design and construct a novel powered orthosis for walk-ing in SCI patients. There will also be a need to interview SCI subjects to determine their satisfaction with the new orthosis.

Conclusions

This study presents a novel powered knee joint mechanism for use in an IRGO that has been used to provide knee flexion during walking by a SCI subject. The results confirm that knee

flexion during swing phase results in an improvement of gait performance and reduction in compensatory mechanisms when compared IRGO with a drop lock knee joint mechanism. The main functional aims of the new AKIRGO were to provide knee stability in stance and free motion of joint during swing. This study demonstrated that the new design can provide this func-tion. Once the design is further developed to provide ambulation with synchronized and powered orthotic hip and knee joints, SCI subjects must be interviewed to determine their satisfaction with both the cosmetic and functional aspects of the orthosis.

Declaration of interest

The authors report no conflicts of interest. This research received no specific grant from any funding agency.

References 1. Leung AK, Wong AF, Wong EC, Hutchins SW. The Physiological Cost

Index of walking with an isocentric reciprocating gait orthosis among patients with T(12) - L(1) spinal cord injury. Prosthet Orthot Int 2009;33:61–68.

2. Lissons M, editor. Advanced reciprocating gait orthosis in paraplegic patients 1992.

3. Motlock W. Principles of orthotic management for child and adult para-plegia and clinical experience with the isocentric RGO. proceeding of 7th world congress of the international society in prosthetic and orthot-ics. 1992:28.

4. Douglas R, Larson P, D’ambrosia R, McCall R. The LSU reciprocation-gait orthosis. Orthopedics. 1983;6:834–838.

5. Rose GK. The principles and practice of hip guidance articulations. Prosthet Orthot Int 1979;3:37–43.

6. Gellman H, Chandler DR, Petrasek J, Sie I, Adkins R, Waters RL. Carpal tunnel syndrome in paraplegic patients. J Bone Joint Surg Am 1988;70:517–519.

7. 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;33:409–415.

8. Massucci M, Brunetti G, Piperno R, Betti L, Franceschini M. Walking with the advanced reciprocating gait orthosis (ARGO) in thoracic para-plegic patients: energy expenditure and cardiorespiratory performance. Spinal Cord 1998;36:223–227.

9. 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;78:582–586.

10. 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;35:585–589.

11. Sykes L, Edwards J, Powell ES, Ross ER. The reciprocating gait orthosis: long-term usage patterns. Arch Phys Med Rehabil 1995;76:779–783.

12. McMillan AG, Kendrick K, Michael JW, Aronson J, Horton GW. Preliminary evidence for effectiveness of a stance control orthosis. JPO: Journal of Prosthetics and Orthotics. 2004;16:6.

13. Greene PJ, Granat MH. A knee and ankle flexing hybrid orthosis for paraplegic ambulation. Med Eng Phys 2003;25:539–545.

14. Edwards J, Bataweel A. Hybrid system for upright mobility with unlockable orthotic knee for knee bending during swing phase. Neuroprosthetics: from basic research to clinical applications Monaco: Springer-Verlag. 1996:523–530.

15. Solomonow M, Baratta R, Hirokawa S, Rightor N, Walker W, Beaudette P, Shoji H, D’Ambrosia R. The RGO Generation II: muscle stimulation powered orthosis as a practical walking system for thoracic paraplegics. Orthopedics 1989;12:1309–1315.

16. Kim G, Kang S, Ryu J, Mun M, Kim K. Unlockable knee joint mecha-nism for powered gait orthosis. International Journal of Precision Engineering and Manufacturing. 2009;10:83–89.

17. Yakimovich T, Lemaire ED, Kofman J. Preliminary kinematic evaluation of a new stance-control knee-ankle-foot orthosis. Clin Biomech (Bristol, Avon) 2006;21:1081–1089.

Dis

abil

Reh

abil

Ass

ist T

echn

ol D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y M

emor

ial U

nive

rsity

of

New

foun

dlan

d on

11/

10/1

3Fo

r pe

rson

al u

se o

nly.

266 M. Arazpour et al.

Disability and Rehabilitation: Assistive Technology

18. Stallard J, Major RE. The influence of orthosis stiffness on paraplegic ambulation and its implications for functional electrical stimulation (FES) walking systems. Prosthet Orthot Int 1995;19:108–114.

19. IJzerman M, Baardman G, Holweg G, Hermens H, Veltink P, Boom H, et al. The influence of frontal alignment in the advanced reciprocating gait orthosis on energy cost and crutch force requirements during paraplegic gait. Basic and Applied Myology. 1997;7:123–130.

20. Winchester PK, Carollo JJ, Parekh RN, Lutz LM, Aston JW Jr. A com-parison of paraplegic gait performance using two types of reciprocating gait orthoses. Prosthet Orthot Int 1993;17:101–106.

21. Harvey LA, Davis GM, Smith MB, Engel S. Energy expenditure during gait using the walkabout and isocentric reciprocal gait orthoses in per-sons with paraplegia. Arch Phys Med Rehabil 1998;79:945–949.

22. Baardman G, Ijzerman M, Hermens H, Veltink P, Boom H, Zilvold G. Knee flexion during the swing phase of orthotic gait in paraplegia. Design and evaluation of a hybrid orthosis for people with paraplegia Joint PhD thesis by Baardman G, Ijzerman MJ. 1996:73–94.

23. Yang L, Condie DN, Granat MH, Paul JP, Rowley DI. Effects of joint motion constraints on the gait of normal subjects and their implications on the further development of hybrid FES orthosis for paraplegic per-sons. J Biomech 1996;29:217–226.

24. Dollar A, Herr H. Lower extremity exoskeletons and active ortho-ses: Challenges and state-of-the-art. Robotics, IEEE Transactions on. 2008;24:144–158.

25. Sawicki GS, Ferris DP. A pneumatically powered knee-ankle-foot ortho-sis (KAFO) with myoelectric activation and inhibition. J Neuroeng Rehabil 2009;6:23.

26. Font-Llagunesa JM, Pàmies-Vilàa R, Alonsob J, Lugrísc U. Simulation and Design of an Active Orthosis for an Incomplete Spinal Cord Injured Subject. 2011.

27. Ohta Y, Yano H, Suzuki R, Yoshida M, Kawashima N, Nakazawa K. A two-degree-of-freedom motor-powered gait orthosis for spinal cord injury patients. Proc Inst Mech Eng H 2007;221:629–639.

28. Saunders JB, Inman VT, Eberhart HD. The major determinants in nor-mal and pathological gait. J Bone Joint Surg Am 1953;35-A:543–558.

29. Inman VT, Ralston HJ, Todd F. Human walking: Williams & Wilkins; 1982.

30. Ferrarin M, Rabuffetti M, Pedotti A, Ferarin M, Quintern J, Reiner R. On the improvement provided by hip transversal rotation on para-plegic gait walking with reciprocating orthosis. Neuroprosthetics: from basic research to clinical applications Monaco: Springer-Verlag. 1996:493–502.

31. Rasmussen AA, Smith KM, Damiano DL. Biomechanical evaluation of the combination of bilateral stance-control knee-ankle-foot orthoses and a reciprocating gait orthosis in an adult with a spinal cord injury. JPO: Journal of Prosthetics and Orthotics. 2007;19:42.

32. Robinson JL, Smidt GL. Quantitative gait evaluation in the clinic. Phys Ther 1981;61:351–353.

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