MOTOR CONTROL DYSFUNCTION often requires that

43 Temporal Stride and Force Analysis of Cane-Assisted Gait in People With Hemiplegic Stroke Chia-Ling Chen, MD, PhD, Hsieh-Ching Chen, PhD, May-Kuen Wong, MD, Fuk-Tan Tang, MD, Rong-Shun Chen, PhD ABSTRACT. Chen C-L, Chen H-C, Wong M-K, Tang F-T, Chen R-S. Temporal stride and force analysis of cane-assisted gait in people with hemiplegic stroke. Arch Phys Med Rehabil 2000;81:43-8. From the Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, Taoyuan (C-L Chen, Wong, Tang); Department of Industrial Engineering and Management, Chaoyang University of Technology, Taichung (H-C Chen); and the Department of Power Mechanical Engineering, National Tsing-Hua University, Hsinchu (R-S Chen), Taiwan. Accepted in revised form March 30, 2000. Supported by the Taiwan National Science Council (grant no. NSC87-2213-E324-009). No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Hsieh-Ching Chen, PhD, Dept of Industrial Engineering and Management, Chaoyang University of Technology, 168 Gifeng E Rd, Wufeng, Taichung County 413, Taiwan, e-mail: hcchen@mail.cyut.edu.tw. 0003-9993/01/8201-6027$35.00/0 doi:10.1053/apmr.2001.18060 Objective: To understand the underlying biomechanics of temporal stride and force in people with hemiplegic stroke during cane-assisted walking. Design: Three forceplates, 6 cameras, and an instrumented cane were integrated to analyze the cane-assisted gait of people with hemiplegic stroke. Temporal-stride parameters, and peak vertical, anterior (propulsive), posterior (braking), and lateral shear forces, as well as propulsive-breaking impulses were analyzed. Setting: Chang Gung Memorial Hospital, Medical Center, Taiwan. Participants: Twenty people with hemiplegic stroke. Main Outcome Measures: Temporal-stride and force parameters. Results: All patients walked at a relatively slow speed, ranging from 4.2 to 35.8cm/s. The triple and double support occupied most of the gait cycle (GC), whereas the single support occupied only 10% of GC. The applied vertical, propulsive, braking, and lateral shear forces on either foot and the cane were 89.7% to 97.6%, 2.2% to 4.8%, 2.9% to 3.9%, and 5.5% to 6.7% body weight (BW), respectively. Patients applied less than 25% BW of peak vertical forces on the cane. They applied greater peak propulsive forces and impulses on the sound foot, while applying greater peak braking forces and impulses on the affected foot and cane. Conclusions: The cane provided support and a braking function for people with hemiplegic stroke. People with stroke walking with cane assistance rely mostly on the sound limb for propulsion, while using the affected limb and cane for braking. Data provided could be useful in assessing the nature of cane assistance and in planning therapeutic strategies for people with stroke. Key Words: Canes; Cerebrovascular disorders; Gait; Rehabilitation. 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation MOTOR CONTROL DYSFUNCTION often requires that people with hemiplegic stroke have assistance while walking. To provide more favorable walking conditions, the choice of a walking aid depends on the needs and deficits of each individual. 1 Walking aids such as canes are often prescribed for stroke patients who have an unstable gait, or whose muscles are weak, or who require a load reduction on weightbearing structures. 2 A simple regular cane may enable a stroke patient to walk more smoothly with greater stability and speed 1,3,4 or with less pain, fatigue, and damage to the supportive structures of the body. 1,3 Although there is a long history of cane usage by people with stroke, there is little quantitative information on the temporal stride and kinetic data of cane-assisted gait. Though some studies have reported on the forces applied on the cane or affected foot during cane-assisted gait, 1,4-10 only Murray et al 1 have reported an analysis of the cane-assisted gait of people with stroke. They reported that their 20 study subjects applied 1 or more brief peaks of force during cane-floor contact. However, only vertical forces were applied on the cane. To our knowledge, no researchers have comprehensively analyzed the temporal stride and kinetic data of cane-assisted gait in stroke patients. Force information related to cane usage can provide the information needed for cane prescriptions. 1 Milczarek et al 11 suggested that a standard cane has a significant effect on the postural sway of the center of pressure when standing balance is measured on a force platform. However, an indeterminacy problem is often encountered in analyzing the cane-assisted gait of hemiplegic stroke patients while using forceplates to measure foot-floor reaction forces. 10 This problem is caused when a forceplate is unable to resolve all the forces simultaneously acting on it. For example, people who rely on cane assistance to walk and who adopt extremely short step lengths will inevitably step on a forceplate with both feet or with the cane and feet at the same time. 10 To understand the contribution of a cane to locomotion, it is necessary to analyze both vertical and anteroposterior (AP) shear forces. The analysis of vertical forces during gait provides information on weight bearing, and analysis of AP shear forces provides information on speed control. However, most studies of cane-assisted gait have reported vertical forces applied by the cane. 1,4-10 Only a few studies have evaluated the function of the cane in propulsion and braking the body by analyzing AP shear forces 6,7,10 and the parameter impulse in people with orthopedic problems or in nonimpaired subjects. 8,9 Although gait analysis is often used to evaluate quantitatively any patient with a walking disability, 12,13 we consider patients who rely on assistance to walk to be among the most rewarding with whom to apply gait analysis technology to improve gait quality or functional outcome. To understand the underlying biomechanics in people with hemiplegic stroke who walk with cane assistance, we first attempt to resolve the

44 CANE-ASSISTED GAIT ANALYSIS IN STROKE PATIENTS, Chen indeterminacy problems. Then we analyze the temporal-stride parameters and forces applied on the cane and both feet. METHODS Subjects People with hemiplegic stroke who are in stable condition and who walk with cane assistance were recruited for this study. Patients who met the following entry criteria were included: (1) unilateral hemiplegia caused by cerebral hemisphere stroke; (2) ages 40 to 65 years; (3) reliance on cane assistance to walk more than 20 meters; (4) the stroke was not a cerebellar or brain stem stroke; (5) exhibited cooperation and compliance in gait analysis; (6) no other peripheral or central nervous system dysfunction; (7) no active inflammatory or pathologic changes in the joints of the upper limb in the most recent 6 months; and (8) no active medical problems. This study was approved by our institutional review board. The study was explained to all the patients, who then gave informed consent. Twenty patients (14 men, 6 women), aged 42 to 62 years (mean standard deviation, 58 7yr), entered the study. The pathology of the stroke subjects included infarction in 7 and hemorrhage in 13 (middle cerebral arterial infarction in 3, corona radiata or basal ganglion infarction in 4, thalamic hemorrhage in 3, putaminal hemorrhage in 10). In addition to the type of stroke (infarction vs hemorrhage), associated diseases (eg, diabetes, hypertension, coronary artery disease), side of the hemiplegia, sensory function, and motor function evaluated by Brunnstrom s recovery stages 14 were recorded. The patients underwent analysis of their cane-assisted gait about 5.8 months (5.8 4.9mo), ranging from 1.2 to 17.3 months, poststroke. Instrumentation A Vicon 370 motion analysis system, a 3 AMTI forceplates, b and an instrumented cane were integrated. The Vicon 370 included 6 infrared cameras for kinematic data collection and a computer for data analysis. The forceplate system consisted of 3 AMTI biomechanic force platforms, 2 of Model OR6-5- 1000, and 1 of Model OR6-5-2000. Each forceplate could measure the 3 directional components of a force acting on it. The instrumented cane had 4 reflective markers, a strain gaugebased load cell, and a battery-operated bridge amplifier (MP- 200) c (fig 1). The cane is of single-foot design and is made of aluminum alloy with a plastic L-shaped handle (EN 640-075). d The instrumented cane was used to measure the magnitude of the contacting force along the cane as it was landing on the floor. Kinematic and kinetic data were collected simultaneously by using a 60Hz sampling rate. To resolve the indeterminacy problems, we used 2 approaches. One approach was to arrange the locations of the forceplates and to propose a guidance gait line. With a forceplate located laterally to the other 2 forceplates, a gait line along the junction of the 3 plates could be adopted to prevent the patient s 2 feet from landing on the same forceplate (fig 1). The gait line was a 2-cm wide red strip that adhered to the Fig. 1. Arrangement of forceplates and gait line, and the installation of the instrumented cane.

CANE-ASSISTED GAIT ANALYSIS IN STROKE PATIENTS, Chen 45 Table 1: Subjects Demographic and Clinical Data Data Values n 20 Demographic data Age (yr) 58.4 6.9 Body height (cm) 160.6 7.9 Body weight (kg) 59.1 9.8 Gender: men 14 (70) Clinical data Associated disease 18 (90) Infarction 4 (20) Right hemiplegia 15 (75) Motor function: Brunnstrom s stages 4 12 (60) Sensory impairment 16 (80) Values are expressed as mean standard deviation for continuous variables, or n (%) for categoric variables. floor and extended from the starting to the ending positions. The starting and ending positions were located 1 meter from the forceplate area. The second approach was to use an instrumented cane such that indeterminacy problems could be resolved when the cane and a foot landed on the same forceplate. The cane measured the axial loading along the stick exerted by the hand and acting on the floor. It was calibrated to have a linear sensitivity of 50kgw/V and to ensure a maximum error of 0.25kgw under a low frequency dynamic load below 50kgw. With 1 foot and the cane loading on the same forceplate simultaneously, the net foot-floor reaction force was deducible by precisely ascertaining the cane-floor reaction. However, the magnitude of the axial force alone could not be applied to derive the net foot-floor reaction force without knowing the orientation of the force along the cane. Therefore, a 4-reflective marker set was attached to the cane to determine its orientation. Gait Analysis Procedures Before testing, the body weight of each dressed patient was measured by using a seated weight scale. The height of the cane was adjusted at the level of the patient s greater trochanter. Four reflective markers were attached to the patients great toes and lateral ankles, and the bridge amplifier for amplifying cane signals was attached to the waist with a belt. These markers were used to determine the landed foot position. The output of the amplifier was connected to the A/D interface of the Vicon system for data acquisition. Patients were asked to walk along a straight proposed gait line with their left and right feet separated on each side of the gait line. During testing, patients walked at a self-selected, comfortable speed, with a cane held in the sound hand. After 1 forward trial, each patient was told to turn around and to wait for the next start sign to take a backward trial. An attempt was considered a mistrial if the cane or either foot landed partially outside the forceplate. Three analyzable trials were saved for further data analysis. Data Analysis An analyzing program, coded by MATLAB software, e processed collected data files and provided temporal-stride and kinetic gait parameters. The temporal-stride analysis included walking speed, stride length, and time, and single-, double-, and triple-support periods. The triple-support period was defined as simultaneous weight bearing on both feet and the cane. The total single-support period was calculated as the sum of the single-support period on the affected foot, and the singlesupport period on the sound foot. Correspondingly, the total double-support period was calculated as the sum of the doublesupport period on both feet, the support period on the affected foot and cane, and the support period on the sound foot and cane. The sum of all support periods on the sound foot were determined as the total sound-foot support period. Those on the affected foot were determined as the total affected-foot support period, and those on the cane were determined as the total cane support period. These support periods were expressed as the percentage of gait cycle (% GC). The heel strike of the unaffected foot was defined as 0% of GC, and the next heel strike (initial contact) of the unaffected foot was defined as 100% of GC. The kinetic analysis included the peak forces and propulsive/ braking impulses of the foot-floor and cane-floor reaction. Peak forces were determined in terms of vertical, AP shear, and lateral shear forces on the affected feet, the sound feet, and the cane. Anterior shear forces work for propulsion and posterior shear forces work for braking. Thus, the propulsive phase was defined as the duration of propulsive forces applied, and the braking phase as the duration of braking forces applied. Integration of the anterior and posterior shear forces with respect to their phases resulted in values of propulsive and braking impulses, respectively. 8,9 The force was expressed as the percentage of body weight (% BW), and the impulse was expressed as % BW/s. RESULTS The demographic data and clinical data of the 20 subjects are listed in table 1. Temporal-Stride Parameters Patients walked at a relatively slow speed (4.2 35.8cm/s), at short-stride length (22.4 52.4cm), and at long-stride time (1.3 6.1s) (table 2). High variations were found in all 3. The tripleand total double-support periods occupied approximately 90% GC, and total single-support periods occupied approximately 10% GC, and were mainly contributed to by the sound foot. The total support period on the sound foot (88% GC) was 18% GC longer than the support periods on either the affected foot or the cane. Peak Forces and Propulsive and Braking Impulses and Phases Patients applied only 7% to 25% BW of peak vertical forces on the cane, though they applied 76% to 100% BW of peak Table 2: Temporal-Stride Parameters in Stroke Patients Mean SD Range Walking speed (cm/s) 15.5 7.9 4.2 35.8 Stride length (cm) 37.5 9.3 22.4 52.4 Stride time (s) 2.9 1.2 1.3 6.1 Support periods (% GC) Single support period: total 10.0 10.3.0 33.9 Sound foot 9.8 10.4.0 33.9 Affected foot.2.7.0 3.1 Double support period: total 51.8 10.4 35.9 71.0 Both feet 20.7 8.3 6.3 36.2 Sound foot and cane 19.8 11.7.0 41.3 Affected foot and cane 11.4 5.0 6.8 21.7 Triple support period 39.7 13.2 25.4 87.2 Total support period Sound foot 88.4 4.8 78.4 93.2 Affected foot 70.5 8.5 57.4 85.5 Cane 69.3 11.7 47.3 92.1

46 CANE-ASSISTED GAIT ANALYSIS IN STROKE PATIENTS, Chen Table 3: Peak Forces, and Propulsive and Breaking Impulses and Phases on Either Foot and Cane in Stroke Patients Sound Foot Affected Foot Cane Peak forces (% BW) Vertical force 97.6 2.8 89.7 6.6 12.7 4.7 Propulsive force 4.8 1.6 2.2 1.5.4.4 Braking force 2.9 1.5 3.9 1.8.6.6 Lateral shear force 5.5 1.6 6.7 1.6.7.5 Impulses (% BW/s) Propulsive impulse 3.7 1.8 1.0 1.1.2.1 Braking impulse 1.1.9 2.4 1.4.5.8 Phases (% GC) Propulsive phase 65.9 12.2 33.6 19.7 28.7 12.0 Braking phase 35.4 12.5 65.4 19.2 70.7 11.8 Values are expressed as mean standard deviation. vertical forces on either foot (table 3). The averaged peak vertical forces applied to either foot was less than BW because they applied 12.7% BW of averaged peak vertical forces on the cane. The timing of peak vertical force on the cane was nearly identical to the timing of peak vertical force of the affected foot at midstance. Greater propulsive impulses were applied on the sound foot, whereas greater braking impulses were applied on the affected foot and cane (table 3). Patients applied greater peak propulsive forces and longer propulsive phases (66% GC) on the sound foot, but applied greater peak braking forces and longer braking phases ( 65% GC) on the affected foot and cane. The sum of the averaged propulsive impulses on the affected foot (1.0% BW/s) and of those on the cane (0.2% BW/s) were approximately equal to the averaged peak braking forces on the sound foot (1.1% BW/s). Conversely, the sum of averaged braking impulses on the affected foot (2.4% BW/s) and of those on the cane (0.5% BW/s) were approximately equal to the averaged propulsive impulses on the sound foot (3.7% BW/s). Correspondingly, similar results were obtained for the relationships between the propulsive and braking forces. Although medial shear forces were relatively small and neglectable, lateral shear forces were 0.7% to 6.7% BW on either foot and cane. Four examples of applied forces, showing the range of variability in the signals, by subjects with hemiplegic stroke are shown in figure 2. DISCUSSION People with hemiplegic stroke who walk with a cane have relatively slower velocities, shorter stride lengths, lesser cadences, and longer stride time. The averaged walking speed in our patients was only 15.5cm/s, but it was reported to be 106cm/s in normal subjects, 15 73cm/s in unassisted people with hemiplegic stroke, 15 and 55 to 60cm/s in people with orthopedic problems with cane assistance. 6,7 This suggests that people with stroke in this study had poor gait performance or functional status. Our results are consistent with those of Murray et al, 1 who reported an average stride time of 2.04 seconds and a total cane support period of 68% GC. 1 These parameters were 2.9 seconds, and 69.3% GC, respectively, in our study. In this study, we first defined the triple-support period for the cane-assisted gait; previous studies only reported the total cane support period, 1,7,16 or single- and double-support periods. 4 We found that triple and double support occupied most of the GC, whereas single support occupied only 10% GC, which is less than in Kuan et al. 4 The reason may be that our patients relied on a cane to walk, but their patients could walk without a cane. Thus, the sound foot contributed the most to the single support of our patients and the sound foot with either the affected foot or a cane contributed mainly to the double-support period. These findings suggest that only the sound limb can provide good single-support weight bearing, whereas the affected limb needs the help of a cane, the sound limb, or both, to provide the double or triple support needed for adequate stability of the body for people with stroke who must walk with a cane. The cane provides support for the affected limb of stroke patients because the peak vertical force application on the cane occurs closely to the instance of peak force application on the affected foot at midstance. The averaged peak vertical cane force applied by our stroke subjects (12.7% BW) was comparable with that reported by Murray 1 (16% BW), but it was much lower than that reported for people with orthopedic problems. 1,7,17 This may relate to the nature and severity of the disabled limb resulting from the cerebrovascular accident, which causes both motor and sensory deficits. Thus, a regular cane may provide sensory feedback for people with stroke through the proprioceptive or tactile sensory input of the sound hand. Some studies have suggested that a cane reduces postural sway, 11,18 through sensory input to the hand and arm or through contact cues at the fingertips, 18 or it improves confidence 19 when contact force levels are inadequate to provide physical support of the body. We found that a cane provided only limited support with less than 25% BW for people with stroke, though either lower limb could provide weight bearing with more than 75% BW. Our findings may imply that, for safety, a cane is better for people with hemiplegic stroke only when peak vertical cane forces are less than 25% BW. Jebsen 20 agreed that a cane should not be used if the force applied exceeds 20% to 25% BW, because the cane is then too unstable. Another function of a cane is to provide a braking effort to restrain forward motion onto the sound limb. All patients applied braking impulses (mean, 0.5% BW/s) larger than propulsive impulses (mean, 0.2% BW/s) on the cane because of greater applied braking forces and longer braking phases. To achieve a reasonably constant velocity, subjects must generate or transmit approximately equal amounts of propulsive and braking impulses. That is, people with hemiplegic stroke rely mostly on the sound limb to provide propulsive efforts to help forward motion, whereas they rely on the affected limb and cane to provide braking efforts to restrain the forward motion. Other studies 1,9 have suggested that people with orthopedic problems use the cane to provide more propulsive functions. Bennett et al 9 found that this population group applied greater propulsive impulses (mean, 0.8% BW/s) than braking impulses (mean, 0.4% BW/s), whereas subjects in Murray s study 1 applied peak vertical forces on the cane during the push-off phase. This might have occurred because a cane provides a compensatory propulsive effort to push forward off of the affected limb to reduce the pain in people with orthopedic problems, whereas it helps the affected limb decelerate the sound limb for people with stroke. CONCLUSION The cane provides both support and braking for people with hemiplegic stroke. Patients walking with a cane rely mostly on the sound limb for propulsion and use the affected limb and cane for braking. This study provides gait data with which to assess the nature and degree of assistance needed by people with stroke, to measure the improvement resulting from various therapeutic procedures, to establish criteria for prescriptions of canes, and to train patients in optimal cane use. This is important because people with stroke walking with a cane want

Fig 2. Vertical (left) and propulsive [ ] and breaking [ ] forces (right) of the feet and cane of 4 persons with hemiplegic stroke walking at different speeds.

48 CANE-ASSISTED GAIT ANALYSIS IN STROKE PATIENTS, Chen to know what the possibility is of discarding their canes and how to improve their gait performance. Analysis of cane-assisted gait in stroke patients can provide an understanding of the biomechanics of canes and underlying motor control. The techniques of analysis we used can also be applied to other neurologic diseases in which patients have short step lengths and require a cane with which to walk. Acknowledgments: The authors thank B.W. Lu and K.D. Hou for their technical assistance. References 1. Murray MP, Seireg AH, Scholtz RC. A survey of the time, magnitude and orientation of forces applied to walking sticks by disabled men. Am J Phys Med 1969;48:1-13. 2. Joyce BM, Kirby RL. Canes, crutches, and walkers. Am Fam Physician 1991;43:535-42. 3. Blount WP. Don t throw away the cane. J Bone Joint Surg Am 1956;38:695-708. 4. Kuan TS, Tsou JY, Su FC. Hemiplegic gait of stroke patients: the effect of using a cane. Arch Phys Med Rehabil 1999;80:777-84. 5. Klenerman L, Hutton WC. A quantitative investigation of the forces applied to walking sticks and crutches. Rheumatol Rehabil 1973;12:152-8. 6. Ely DD, Smidt GL. Effect of cane on variables of gait for patients with disorders. Phys Ther 1977;57:507-12. 7. Edwards BG. Contralateral and ipsilateral cane usage by patients with total knee or hip replacement. Arch Phys Med Rehabil 1986;67:734-40. 8. Opila KA, Nicol AC, Paul JP. Forces and impulse during aided gait. Arch Phys Med Rehabil 1987;68:715-22. 9. Bennett L, Murray MP, Murphy EF, Sowell TT. Locomotion assistance through cane impulse. Bull Prosthet Res 1979;10(31):38-47. 10. Winter DA, Deathe AB, Halliday S, Ishac M, Olin M. A technique to analyse the kinetics and energetics of cane-assisted gait. Clin Biomech 1993;8:37-43. 11. Milczarek JJ, Kirby RL, Harrison ER, MacLeod DA. Standard and four-footed canes: their effect on the standing balance of patients with hemiparesis. Arch Phys Med Rehabil 1993;74:281-5. 12. Winter DA. Biomechanics and motor control of human movement. New York: Wiley; 1990. 13. Perry J. Gait analysis: normal and pathological function. Thorofare (NJ): Slack; 1992. 14. Brunnstrom S. Movement therapy in hemiplegia: a neurophysiological approach. New York: Harper & Row; 1970. 15. Von Schroeder HP, Coutts RD, Lyden PD, Billings E Jr, Nickel VL. Gait parameters following stroke: a practical assessment. J Rehabil Res Dev 1995;32:25-31. 16. Wall JC, Ashburn A. Assessment of gait disability in hemiplegics. Scand J Rehabil Med 1979;11:95-103. 17. Engel J, Amir A, Messer E, Caspi I. Walking cane designed to assist partial weight bearing. Arch Phys Med Rehabil 1983;64: 386-8. 18. Jeka JJ. Light touch contact as a balance aid. Phys Ther 1997;77: 476-87. 19. Deans E, Ross M. Relationships among cane fitting function and falls. Phys Ther 1993;73:494-504. 20. Jebsen RH. Use and abuse of ambulation aids. JAMA 1967;199: 63-8. Suppliers a. Oxford Metrics Ltd, Unit 14, 7 West Way, Botley, Oxford, OX2 0JB, UK. b. Advanced Mechanical Technology Inc, 176 Waltham St, Watertown, MA 02172. c. Anima Corp, 65-1, Sec. 3, Simoishihara, Chyofu-Shi, Tokyo, Japan. d. E.N.S.D. Corp, 389-1, Ruei Ching Rd, Taoyuan City, 330 Taiwan. e. MathWorks, Inc, 3 Apple Hill Dr, Natick, MA 01760.