- Email: [email protected]
14 The use of two foot-floor models to examine the role of the ankle plantar flexors in the forward acceleration of normal gait
Abstracts frontal plane torques were no longer required to supplement the saglttal torques Howeber, the hip Internal rotation torque was found sigmftcantly higher for all the s”bJccts with the brace was on (HTT_IN, F=8.4, p c: O.OO),.
Discussion
and
Conclusion
The .ACL rehabdltated indwduals run wth lower ilexlon and extenston torques at the knee, their hnee extension and flexlon was achieved through the reversal effect from the acr~on at the hip and ankle Joints during the recovery phase. During the loaded, support phase of runnmg the ACL subjects used the frontal and transverse plane torques to compensate for thetr low torques m the sa81ttal plane, torques winch tend to destabllwo the ACI. Imolved knee The knee brace support increased the confidence of the ACL mdwduals for stablhty of the hncc and resulted m a more normal use of the knee Joint producmg higher knee flc~;lon and extension torques. This higher functionality of the knee ~“rnt m the saylttal plane had a slgntticant reduction effect on the frontal plane torques
Refcrcnces I. Branch ~1 aI. Am J Sports Med 17 3541 ( 19R9) 2. Andrlacchl & Birac. Chn Orthop Rel R~s 288 40-17 (1993) 3 Manno & Eberlc. Int Symp Blom m Sports. Budapest (1994) 4 5 De Vita et al. J of Blom De Viva ct aI, Mcd Scr Sports Euerc 24 797-806 (1992)
19 5X3-M
( IY9h) Acknowledgments
fhc authors want ,o thanh thu Natural Sucnce and Engmccrm8 Research Canada ils &I ils the Mcdws. Labom~o~ro d‘Ortheses et dc Protheses. Qoebcc. Canada. for their lin;tnclal support towards thus pr”Jea
Results
Quantifying Daily Load Bearing of Ground Reaction Forces Measured
Jonathan ‘Center for Locomotion “Department of Ohstenics
Activity:
Over
C”uncl1 of Montrcnl.
Figure
2
Force Peaks and Peak Histogram
from a 10 HI Ttial
fmm an “Active”
Subject.
Discussion Although the PFMD is considerably less accurate in measuring ground reaction force profiles than in-around force olatforms. data collected “sine this device have the ootential to orovide conside;able insight ‘into the mechanisms of honk remodeling It has’been hypothesized (Whalen et al., 1988, and Beaupre et aI., 1990) that bone response to daily mechanical load is much more a function of the magnitude of peak loads than the number of peaks. The large difference in higher magnitude peaks seen between the two subjects shown in figures 1 and 2 would clearly allow this hypothesis to be tested in a group of young women with diverse profiles of physical activity. Gaming a better understanding of the relationship between lower extremity loading and bone mineral changes could also be important in other situations. The weightless environment of spacenight leads to significantly reduced lower extremity loading, snd significant hone loss. At the other end of the spectrum. excessive loading of the lower extremities can lead 1” stress fractures. especially in PI risk populations such a.$ athletes and military recruits (Grimston et al., 1991) Exploration of these conditions. and others, appear to be within the realm of the PFMD.
References a Ten Hour
Day
M.S1, Peter R. Cavanagh, Ph.D.‘, and Thomas Lloyd. Ph.D.’ Studies, Penn State University, University Park, PA 16803 and Gynecology. Hershey Medical Center, Hershey, PA 17033
Intr”ducdon Many clinical applications of gait analysis require an e xamination of more than the single footground contact that is often sampled. For example, load bearing activities (LBA’s) play an tmpottant role in the development and maintenance of bone sttength but typical laboratory analysis gives no indication of cumulative loading. Decreased activity levels have been show” to reduce the stresses applied to bones, resulting in loss of bone mineral density (BMD), whereas increased activity levels re.stdted in increased BMD (Smith et al.. 1989, and Chiliheck et a& 1995). However, the exact naNm of the reIationship between long term lower extremity loadtng and bone remodeling is still poorly understood. This is due in large Part to the lack of a convenient, accurate. and reproducible meaos of measuring LBA’s doting daily activities. The device described by Bruit and Whalen (1994) offers many new possibilities for long term monitoring during unrest&ted activities of daily living. We have replicated their device and present initial results of data collected when this device was worn for a complete 10 hour day by adolescent women.
Methodology The Personal Force Monitoring Device (PFMD) consists of a pair of capacitative force monitoring shoe insoles and a dual force monitor signal amplifier (Electronic Quantification, Inc.). a Tattletale microprocessor (Onset Computer. Inc.) with a four megabyte PCMCIA card for data storage. and an elastic waist belt to which these electronics are attached. The entire system is powered by four g-volt batteries, weighs only two pounds. and can be comfortably worn by a subject throughout the course of a full day’s activities. Ten hours of continuous data were collected from each of four subjects during unrestricted activities. Ground reaction forces were sampled at 25 Hz fmm both the left and tight feet. Data were downloaded from the PFMD to an IBM Pentittm (IBM, Inc.). and analyzed “sing routines developed in Matlab (The Mathworks. Inc.). MatIab routines were developed to convert the raw voltage data to percent body weight (CBW). In order to quantify the loading history for each subject, the Peak force values above 15 %BW were extracted from the force data and plotted in a histogram distribution. These histograms were generated by dividing the external loads into equally spaced catxgoties (or “bins”) from 15 ZBW to 300 %BW. and counting the number of peak forces that occurred within each bin.
Results Each of the four subjects demonstrated distinctly different patterns of loading over the course of the ten how day, and distinctly different distributions of peak loads were seen in the histograms of all four subjects as well. Slight differences in force distributions were also seen between the left and right feet of each subject. Sample plots of the loading peaks and resulting histograms for one foot of two of the subjects are shown in Figures 1 and 2. Note that the first subject was relatively inactive, while the second subject was a cross-country rttnner who practiced during the afternoon. Distinct periods of activity and inactivity can b-e seen in the Load-Time History plots of both subjects. The increased level of forces encountered by the second suhjrct are evident from both the Load-Time History and Peak Histogram plots. The number of force peaks greater than 125 ZBW experienced by the first subject was only 64. compared to 29X0 such peaks for the second subject.
Beaupre GS et sl. Joumol oJOrfhopardic Research. 8: 651 661. 1990. Breit GA nnd Whalen RT, Proceedings ofrhe 18th Annual Meeting of fhe American SocirN Biomechonics. 231 - 232. 1994. Chilibeck PD et nl.. Sporrs Medicine. 19: 103 122. 1995. Grimston S et 31.. Inremcrrionol Joorrmol oJSporrs Biomechnnics. 7: 293 309, 1991. Smith EL et al.. Bone undMinerolRrseorch. 6: 139 - 173. 1989. Whalen RT ct al.. J”~orcmrr/ oJBiom~hon~s. 21 (IO): 825 - 837. 1988.
The Use of Two Foot-floor Models in the Forward Thomas
M. Kc”“&. Karen National Institutes
to Examine Acceleration Lohmann of Health.
the Role of the Ankle of Normal Gait.
Plantar ’
Flexors
Siegel attd Steven J. Stanhope Bethesda. MD 20892
A biomechanical model was previously developed to estimate the relative contribution of each lower extremity joint to the forward acceleration of the upper body during gait (Kepplc et al. 1996). Application of the model revealed that the generation of forward velocity arose prunarily from plantar nexor push-off rather than through a controlled fall. In addition. the plantar tlexors produced il forward acceleration of the upper body during periods m which they were acting eccentricly. These results were in contradiction with some previous studies on the role of plantar nexors during gait (Simon et al. 1978. and Sutherland et al. 1980). A crucial assumption of the model was the constraint used to connect the model to the environment, The foot was connected to the floor at the center of pressure such that the foot could not translate into the ground. but could rotate freely. This assumption was equivalent to placing B visco-elastic element between the foot and the floor such that the translational stiffness was infmite but the rotational stiffness was zero. This somewhat unrealistic assumption could be responsible for overestimating the role of the plantar tlexors in the generation of forward acceleration (Bogart 1996). The purpose of this study was to examine the sensitivity of the biomechanical model to the foot-tloor constraints in order to clarify the role of the ankle plantar flexors in forward acceleration.
Methodology A SIX cilmera Vicon system was used to measure five subjects walking at a self selected pace. The subjects were free of any impairment that might have affected their gait. Data from light mid-stance to right toe-off was used as input into a seven segment mechanical model (Kcpplc et al. 1996). The model was connected to the environment at the center of I ) infiiite translational stiffness with zero prcsswc using two mechanical constraints: rotilt1on31 .\oiiness and 2) infinite translational stiffness with infinite rotational stiffness.
ReslIlt.5 For all live subjects the estimated contributions of the ankle plant= flexors to the forward acceleration of the upper body were found to be smaller when the infmite rotational constraint was u\ed. (Data for one indicatwc subject are presented in Figure I.) However. for both mcchamcal models the ankle plantar llexors were found to produce an important contribution to forward accclera~on throughout the entire interval. In fact. m all subjects and Ibr both constraints. the plantar Ilexors produced forward accelerations during the mtcrwl ofccccntric activity immcdintely following mid-stance.
Discussion Trm wl, Figure
I - Force Peaks and Peak Histogrsm
II
from a 10 Hr Trial
Put .=c.w(saw, from an “Inactive”
Subiect.
It is believed that the zero rotational constraint model over-estimates and that the infmite rotational constmint model under-estmxttes the contribution of the ankle plantar flexors to forward acceleration. Because the contribution of the plantar flexors probably lies between
of
Abstracts these two estimates. it is clear that gravity does play some role in the generation 01 forward progression and normal gait may be. in pan, a controlled fall. However, both constraint models support the previously stated assertions that the ankle plantar flexors acttvely contribute to forward acceleration even during eccentric plantar flexor activity.
113 by significantly increasing their adduction moment between the first and second test periods. wO.001) The patients with increased pain responded by decreasing their adduction moment. Moreover, the change in adduction moment for the increased pain group was significantly different from the change in the adduction moment for the decreased pain group (pc.02) (Fiow
2). Discussion A reduction in pain caused an increase in the loads at the knee in patients with medial compartment artbmsis. The significant increase in knee adduction moment will have a substantial effect on the medial compartment load at the knee. Patients appear to adapt their gait in a manner that reduces the load on a painful area of the joint. Thus, care must be taken in the use of phammceuticals directed at reducing pain since it appears that a reduction in pain can be directly related to increased loading on the degenerative portions of the joints.
Figure I. Est~mzttes of the acceleration produced by the right ankle plantar flexors during the interval from right mid-stance to right toe-off (subject 3). The zero rotational constmint dara is represented by the solid line and the infinite rotationaldata is represented in the dashed line. References Bogart T. Personal correspondence, 1996. Kepple et al. Gut and Posture, in press. 1996. Simon et al. J Bone mulJoi~tt Sur,qery, 60:465-472. 1978. Sutherland et al. Bone und Jorn~ Svr,qery, 62: 354.363, 1980.
El
The Impact
of Osteonrtbritic
Knee
Pain on Dynamic
20 1 ,“C”...d
Loads
during
0a
0.rl..*.dP.h “I,%.
Lmnd.I” Il.‘.
lMC”Mgs M.1,
B9w.udc.n )I.,,’
Figure 2. The average change in adduction moment between pain groups. * indicates significant difference, p
Acknowledgments: SCOR Grant AR39239-08 Force
29 patients with knee pain and radiographic evidence of medial compartment osteoarthritis were included in this study. They were 13 males and I6 females with an average age of 61fIO years (range 40-74). The patients for the study were selected from a larger group of patients enrolled in a double blinded study in which patients were given either an NSAID or placebo. The first gait test was performed atier patients were taken off any NSAID or analgesics for two weeks. The subjects were then given either an NSAID or placebo and a second gait test was performed two weeks later. IRB approval and informed consent from all subjects were obtained. The instrumentation included a two-camera optoelectronic system for motion analysis and a multi-component force plate. Measurements of joint reaction moment, intersegmental angles. and temporal relationships were obtained over a range of self-selected walking speeds.[2] Pain was measured clinically by use of the Hospital for Special Surgery Rating Form (HSS). Based on changes in HSS knee scores, the patients were divided into three groups on the basis of whether their pain was increased by at least ten points, decreased by at least ten points, or unchanged over the two-week trial period. The group with increased pain (n=5) had an average change in pam score of -24+8 out of a possible 50 while the group with decreased pain had an average change in pain score of 19?7 (Figure i). Higher HSS pain scores actually indicate lower pain levels Statistical methods included use of paired t-tests for differences between visits while independent t-tests were utilized for differences between groups. A significance level of 0.05 was used. Results
measurement of the he&trike transient in normal walking El M&haelW w&&,MD,PhD The University of Tennessee at Chattanooga, Chattanooga, Tennessee 37403 Siskin Hospital for Physical Rehabilitation, Chattanooga, Tennessee 37403 Introduction The “heelstrike transient” is an acceleration wave which passes up the lib, immediately after initial contact (Simon et al., 1981). It has been suggested that it may cause a variety of disorders, including overuse injuries, chronic backache, osteoarthritis and prosthetic loosening (Pratt, 1989). The present study was devoted to identifying this and other peaks in the ground reaction force (GRF) immediately following initial contact, and to make a preliminary estimate of its magnitude in normal individuals The study forms part of an ongoing investigation into the heelstrike transient, its measurement, and its attenuation by viscoelastic materials, either in shoe construction or as insoles. Methodology A single-case study wa,s performed to determine the characteristics of the GRF immediately following initial contact, in a single individual (male, age 52, weight 70 kg) walking under three conditions, barefoot, in leather street shoes with hard rubber heels, and in the same shoes with “Cambion” viscoelastic insoles (Magister Corporation, Chattanooga). The magnitude of the heelstrike transient in barefoot walking was also measured beneath both feet of 10 normal adults (5 male, 5 female, age range 2%62), during 3 walks each. In both studies, each individual walked at a self-selected speed across a pair of force platforms with a resonant frequency in excess of 6OOHz (Bettec, Worthington, Ohio), the outputs from which were sampled by analog-to-digital converter, without filtration, at either SOOHz or 1OOOHz The data from the force platforms were zeroed to the no-load condition, and used to calculate the vector magnitude in the sagittal plane. The beginning and end ofthe heelstrike were defined, using an algorithm based on the magnitude and rate of change of force. These points were joined by an interpolation line on the force/time plot (Fig I), and the heelstrike magnitude was defined as
of knee joint pain responded
platform
He&trike
0 pain and a key determinant The patients with decreased
TJ, ORS Trans., 15:557,1990 TP, JBJS, 64A:l328, 1982.
Gait
Methodology
loading
Wocnml~. 11.1,
Figure 1. The average change in HSS score between pain groups. * indicates significant difference, p< 0.001
I. Schnitzer 2. Andriacchi
The mechanical factors influencing the progression of osteoarthritis (OA) at the knee joint are not well understood. In particular. the impact of pain on joint loading could have a significant impact on the progression of osteoarthritis at the knee. One goal in the treatment of OA has been to decrease the pain and inflammation of the involved joints, often times through pharmaceutical intervention. Pain in an osteoarthtitic knee during walking is believed to induce a protective biomechanical response that reduces the load on the joint.[l] The purpose of this study was to test the hypothesis that a relationship exists between pain and joint loading in patients with medial compartment attbrosis of the knee joint.
was found between adduction moment).
I ,.I”
References
J. D.E. Hurwitz, R.C. Janik, J. -sander, T.P. Andriacchi. T.J. Schnitzer, G.B.J. Andersson Department of Orthopedic Surgery Rush Presbyterran-St. Luke’s Medical Center Chicago, IL 60612
An inverse relationship during gait (the external
I Y-l.
10
20
Figure I Method heelstrike magnitude
transient
Tirn3°ma of calculating
40
50 the
0
20
40 TmE;;
Figure 2: GRF in sagittal (see text for letter codes)
100
120 140
plane, barefoot
Discussion
and
Conclusion
The .ACL rehabdltated indwduals run wth lower ilexlon and extenston torques at the knee, their hnee extension and flexlon was achieved through the reversal effect from the acr~on at the hip and ankle Joints during the recovery phase. During the loaded, support phase of runnmg the ACL subjects used the frontal and transverse plane torques to compensate for thetr low torques m the sa81ttal plane, torques winch tend to destabllwo the ACI. Imolved knee The knee brace support increased the confidence of the ACL mdwduals for stablhty of the hncc and resulted m a more normal use of the knee Joint producmg higher knee flc~;lon and extension torques. This higher functionality of the knee ~“rnt m the saylttal plane had a slgntticant reduction effect on the frontal plane torques
Refcrcnces I. Branch ~1 aI. Am J Sports Med 17 3541 ( 19R9) 2. Andrlacchl & Birac. Chn Orthop Rel R~s 288 40-17 (1993) 3 Manno & Eberlc. Int Symp Blom m Sports. Budapest (1994) 4 5 De Vita et al. J of Blom De Viva ct aI, Mcd Scr Sports Euerc 24 797-806 (1992)
19 5X3-M
( IY9h) Acknowledgments
fhc authors want ,o thanh thu Natural Sucnce and Engmccrm8 Research Canada ils &I ils the Mcdws. Labom~o~ro d‘Ortheses et dc Protheses. Qoebcc. Canada. for their lin;tnclal support towards thus pr”Jea
Results
Quantifying Daily Load Bearing of Ground Reaction Forces Measured
Jonathan ‘Center for Locomotion “Department of Ohstenics
Activity:
Over
C”uncl1 of Montrcnl.
Figure
2
Force Peaks and Peak Histogram
from a 10 HI Ttial
fmm an “Active”
Subject.
Discussion Although the PFMD is considerably less accurate in measuring ground reaction force profiles than in-around force olatforms. data collected “sine this device have the ootential to orovide conside;able insight ‘into the mechanisms of honk remodeling It has’been hypothesized (Whalen et al., 1988, and Beaupre et aI., 1990) that bone response to daily mechanical load is much more a function of the magnitude of peak loads than the number of peaks. The large difference in higher magnitude peaks seen between the two subjects shown in figures 1 and 2 would clearly allow this hypothesis to be tested in a group of young women with diverse profiles of physical activity. Gaming a better understanding of the relationship between lower extremity loading and bone mineral changes could also be important in other situations. The weightless environment of spacenight leads to significantly reduced lower extremity loading, snd significant hone loss. At the other end of the spectrum. excessive loading of the lower extremities can lead 1” stress fractures. especially in PI risk populations such a.$ athletes and military recruits (Grimston et al., 1991) Exploration of these conditions. and others, appear to be within the realm of the PFMD.
References a Ten Hour
Day
M.S1, Peter R. Cavanagh, Ph.D.‘, and Thomas Lloyd. Ph.D.’ Studies, Penn State University, University Park, PA 16803 and Gynecology. Hershey Medical Center, Hershey, PA 17033
Intr”ducdon Many clinical applications of gait analysis require an e xamination of more than the single footground contact that is often sampled. For example, load bearing activities (LBA’s) play an tmpottant role in the development and maintenance of bone sttength but typical laboratory analysis gives no indication of cumulative loading. Decreased activity levels have been show” to reduce the stresses applied to bones, resulting in loss of bone mineral density (BMD), whereas increased activity levels re.stdted in increased BMD (Smith et al.. 1989, and Chiliheck et a& 1995). However, the exact naNm of the reIationship between long term lower extremity loadtng and bone remodeling is still poorly understood. This is due in large Part to the lack of a convenient, accurate. and reproducible meaos of measuring LBA’s doting daily activities. The device described by Bruit and Whalen (1994) offers many new possibilities for long term monitoring during unrest&ted activities of daily living. We have replicated their device and present initial results of data collected when this device was worn for a complete 10 hour day by adolescent women.
Methodology The Personal Force Monitoring Device (PFMD) consists of a pair of capacitative force monitoring shoe insoles and a dual force monitor signal amplifier (Electronic Quantification, Inc.). a Tattletale microprocessor (Onset Computer. Inc.) with a four megabyte PCMCIA card for data storage. and an elastic waist belt to which these electronics are attached. The entire system is powered by four g-volt batteries, weighs only two pounds. and can be comfortably worn by a subject throughout the course of a full day’s activities. Ten hours of continuous data were collected from each of four subjects during unrestricted activities. Ground reaction forces were sampled at 25 Hz fmm both the left and tight feet. Data were downloaded from the PFMD to an IBM Pentittm (IBM, Inc.). and analyzed “sing routines developed in Matlab (The Mathworks. Inc.). MatIab routines were developed to convert the raw voltage data to percent body weight (CBW). In order to quantify the loading history for each subject, the Peak force values above 15 %BW were extracted from the force data and plotted in a histogram distribution. These histograms were generated by dividing the external loads into equally spaced catxgoties (or “bins”) from 15 ZBW to 300 %BW. and counting the number of peak forces that occurred within each bin.
Results Each of the four subjects demonstrated distinctly different patterns of loading over the course of the ten how day, and distinctly different distributions of peak loads were seen in the histograms of all four subjects as well. Slight differences in force distributions were also seen between the left and right feet of each subject. Sample plots of the loading peaks and resulting histograms for one foot of two of the subjects are shown in Figures 1 and 2. Note that the first subject was relatively inactive, while the second subject was a cross-country rttnner who practiced during the afternoon. Distinct periods of activity and inactivity can b-e seen in the Load-Time History plots of both subjects. The increased level of forces encountered by the second suhjrct are evident from both the Load-Time History and Peak Histogram plots. The number of force peaks greater than 125 ZBW experienced by the first subject was only 64. compared to 29X0 such peaks for the second subject.
Beaupre GS et sl. Joumol oJOrfhopardic Research. 8: 651 661. 1990. Breit GA nnd Whalen RT, Proceedings ofrhe 18th Annual Meeting of fhe American SocirN Biomechonics. 231 - 232. 1994. Chilibeck PD et nl.. Sporrs Medicine. 19: 103 122. 1995. Grimston S et 31.. Inremcrrionol Joorrmol oJSporrs Biomechnnics. 7: 293 309, 1991. Smith EL et al.. Bone undMinerolRrseorch. 6: 139 - 173. 1989. Whalen RT ct al.. J”~orcmrr/ oJBiom~hon~s. 21 (IO): 825 - 837. 1988.
The Use of Two Foot-floor Models in the Forward Thomas
M. Kc”“&. Karen National Institutes
to Examine Acceleration Lohmann of Health.
the Role of the Ankle of Normal Gait.
Plantar ’
Flexors
Siegel attd Steven J. Stanhope Bethesda. MD 20892
A biomechanical model was previously developed to estimate the relative contribution of each lower extremity joint to the forward acceleration of the upper body during gait (Kepplc et al. 1996). Application of the model revealed that the generation of forward velocity arose prunarily from plantar nexor push-off rather than through a controlled fall. In addition. the plantar tlexors produced il forward acceleration of the upper body during periods m which they were acting eccentricly. These results were in contradiction with some previous studies on the role of plantar nexors during gait (Simon et al. 1978. and Sutherland et al. 1980). A crucial assumption of the model was the constraint used to connect the model to the environment, The foot was connected to the floor at the center of pressure such that the foot could not translate into the ground. but could rotate freely. This assumption was equivalent to placing B visco-elastic element between the foot and the floor such that the translational stiffness was infmite but the rotational stiffness was zero. This somewhat unrealistic assumption could be responsible for overestimating the role of the plantar tlexors in the generation of forward acceleration (Bogart 1996). The purpose of this study was to examine the sensitivity of the biomechanical model to the foot-tloor constraints in order to clarify the role of the ankle plantar flexors in forward acceleration.
Methodology A SIX cilmera Vicon system was used to measure five subjects walking at a self selected pace. The subjects were free of any impairment that might have affected their gait. Data from light mid-stance to right toe-off was used as input into a seven segment mechanical model (Kcpplc et al. 1996). The model was connected to the environment at the center of I ) infiiite translational stiffness with zero prcsswc using two mechanical constraints: rotilt1on31 .\oiiness and 2) infinite translational stiffness with infinite rotational stiffness.
ReslIlt.5 For all live subjects the estimated contributions of the ankle plant= flexors to the forward acceleration of the upper body were found to be smaller when the infmite rotational constraint was u\ed. (Data for one indicatwc subject are presented in Figure I.) However. for both mcchamcal models the ankle plantar llexors were found to produce an important contribution to forward accclera~on throughout the entire interval. In fact. m all subjects and Ibr both constraints. the plantar Ilexors produced forward accelerations during the mtcrwl ofccccntric activity immcdintely following mid-stance.
Discussion Trm wl, Figure
I - Force Peaks and Peak Histogrsm
II
from a 10 Hr Trial
Put .=c.w(saw, from an “Inactive”
Subiect.
It is believed that the zero rotational constraint model over-estimates and that the infmite rotational constmint model under-estmxttes the contribution of the ankle plantar flexors to forward acceleration. Because the contribution of the plantar flexors probably lies between
of
Abstracts these two estimates. it is clear that gravity does play some role in the generation 01 forward progression and normal gait may be. in pan, a controlled fall. However, both constraint models support the previously stated assertions that the ankle plantar flexors acttvely contribute to forward acceleration even during eccentric plantar flexor activity.
113 by significantly increasing their adduction moment between the first and second test periods. wO.001) The patients with increased pain responded by decreasing their adduction moment. Moreover, the change in adduction moment for the increased pain group was significantly different from the change in the adduction moment for the decreased pain group (pc.02) (Fiow
2). Discussion A reduction in pain caused an increase in the loads at the knee in patients with medial compartment artbmsis. The significant increase in knee adduction moment will have a substantial effect on the medial compartment load at the knee. Patients appear to adapt their gait in a manner that reduces the load on a painful area of the joint. Thus, care must be taken in the use of phammceuticals directed at reducing pain since it appears that a reduction in pain can be directly related to increased loading on the degenerative portions of the joints.
Figure I. Est~mzttes of the acceleration produced by the right ankle plantar flexors during the interval from right mid-stance to right toe-off (subject 3). The zero rotational constmint dara is represented by the solid line and the infinite rotationaldata is represented in the dashed line. References Bogart T. Personal correspondence, 1996. Kepple et al. Gut and Posture, in press. 1996. Simon et al. J Bone mulJoi~tt Sur,qery, 60:465-472. 1978. Sutherland et al. Bone und Jorn~ Svr,qery, 62: 354.363, 1980.
El
The Impact
of Osteonrtbritic
Knee
Pain on Dynamic
20 1 ,“C”...d
Loads
during
0a
0.rl..*.dP.h “I,%.
Lmnd.I” Il.‘.
lMC”Mgs M.1,
B9w.udc.n )I.,,’
Figure 2. The average change in adduction moment between pain groups. * indicates significant difference, p
Acknowledgments: SCOR Grant AR39239-08 Force
29 patients with knee pain and radiographic evidence of medial compartment osteoarthritis were included in this study. They were 13 males and I6 females with an average age of 61fIO years (range 40-74). The patients for the study were selected from a larger group of patients enrolled in a double blinded study in which patients were given either an NSAID or placebo. The first gait test was performed atier patients were taken off any NSAID or analgesics for two weeks. The subjects were then given either an NSAID or placebo and a second gait test was performed two weeks later. IRB approval and informed consent from all subjects were obtained. The instrumentation included a two-camera optoelectronic system for motion analysis and a multi-component force plate. Measurements of joint reaction moment, intersegmental angles. and temporal relationships were obtained over a range of self-selected walking speeds.[2] Pain was measured clinically by use of the Hospital for Special Surgery Rating Form (HSS). Based on changes in HSS knee scores, the patients were divided into three groups on the basis of whether their pain was increased by at least ten points, decreased by at least ten points, or unchanged over the two-week trial period. The group with increased pain (n=5) had an average change in pam score of -24+8 out of a possible 50 while the group with decreased pain had an average change in pain score of 19?7 (Figure i). Higher HSS pain scores actually indicate lower pain levels Statistical methods included use of paired t-tests for differences between visits while independent t-tests were utilized for differences between groups. A significance level of 0.05 was used. Results
measurement of the he&trike transient in normal walking El M&haelW w&&,MD,PhD The University of Tennessee at Chattanooga, Chattanooga, Tennessee 37403 Siskin Hospital for Physical Rehabilitation, Chattanooga, Tennessee 37403 Introduction The “heelstrike transient” is an acceleration wave which passes up the lib, immediately after initial contact (Simon et al., 1981). It has been suggested that it may cause a variety of disorders, including overuse injuries, chronic backache, osteoarthritis and prosthetic loosening (Pratt, 1989). The present study was devoted to identifying this and other peaks in the ground reaction force (GRF) immediately following initial contact, and to make a preliminary estimate of its magnitude in normal individuals The study forms part of an ongoing investigation into the heelstrike transient, its measurement, and its attenuation by viscoelastic materials, either in shoe construction or as insoles. Methodology A single-case study wa,s performed to determine the characteristics of the GRF immediately following initial contact, in a single individual (male, age 52, weight 70 kg) walking under three conditions, barefoot, in leather street shoes with hard rubber heels, and in the same shoes with “Cambion” viscoelastic insoles (Magister Corporation, Chattanooga). The magnitude of the heelstrike transient in barefoot walking was also measured beneath both feet of 10 normal adults (5 male, 5 female, age range 2%62), during 3 walks each. In both studies, each individual walked at a self-selected speed across a pair of force platforms with a resonant frequency in excess of 6OOHz (Bettec, Worthington, Ohio), the outputs from which were sampled by analog-to-digital converter, without filtration, at either SOOHz or 1OOOHz The data from the force platforms were zeroed to the no-load condition, and used to calculate the vector magnitude in the sagittal plane. The beginning and end ofthe heelstrike were defined, using an algorithm based on the magnitude and rate of change of force. These points were joined by an interpolation line on the force/time plot (Fig I), and the heelstrike magnitude was defined as
of knee joint pain responded
platform
He&trike
0 pain and a key determinant The patients with decreased
TJ, ORS Trans., 15:557,1990 TP, JBJS, 64A:l328, 1982.
Gait
Methodology
loading
Wocnml~. 11.1,
Figure 1. The average change in HSS score between pain groups. * indicates significant difference, p< 0.001
I. Schnitzer 2. Andriacchi
The mechanical factors influencing the progression of osteoarthritis (OA) at the knee joint are not well understood. In particular. the impact of pain on joint loading could have a significant impact on the progression of osteoarthritis at the knee. One goal in the treatment of OA has been to decrease the pain and inflammation of the involved joints, often times through pharmaceutical intervention. Pain in an osteoarthtitic knee during walking is believed to induce a protective biomechanical response that reduces the load on the joint.[l] The purpose of this study was to test the hypothesis that a relationship exists between pain and joint loading in patients with medial compartment attbrosis of the knee joint.
was found between adduction moment).
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References
J. D.E. Hurwitz, R.C. Janik, J. -sander, T.P. Andriacchi. T.J. Schnitzer, G.B.J. Andersson Department of Orthopedic Surgery Rush Presbyterran-St. Luke’s Medical Center Chicago, IL 60612
An inverse relationship during gait (the external
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Figure 2: GRF in sagittal (see text for letter codes)
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plane, barefoot