JCLB-03774; No of Pages 5 Clinical Biomechanics xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Clinical Biomechanics journal homepage: www.elsevier.com/locate/clinbiomech
Brief report
Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses Toshiki Kobayashi a,⁎, Michael S. Orendurff a, Ming Zhang b, David A. Boone a a b
Orthocare Innovations, Mountlake Terrace, WA, USA Interdisciplinary Division of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Hong Kong, China
a r t i c l e
i n f o
Article history: Received 15 February 2014 Accepted 7 April 2014 Keywords: Amputation Direct measurement Gait Kinetic Malalignment SACH foot
a b s t r a c t Background: The alignment of transtibial prostheses has a systematic effect on the mean socket reaction moments in amputees. However, understanding their individual differences in response to alignment perturbations is also important for prosthetists to fully utilize the socket reaction moments for dynamic alignment in each unique patient. The aim of this study was to investigate individual responses to alignment perturbations in transtibial prostheses with solid-ankle-cushion-heel feet. Methods: A custom instrumented prosthesis alignment component was used to measure the socket reaction moments while walking in 11 amputees with transtibial prostheses under 17 alignment conditions, including 3° and 6° of flexion, extension, abduction, and adduction of the socket, 5 mm and 10 mm of anterior, posterior, lateral, and medial translation of the socket, and an initial baseline alignment. Coronal moments at 30% of stance and maximum sagittal moments were extracted for comparisons from each amputee. Findings: In the coronal plane, varus moment at 30% of stance was generally reduced by adduction or medial translation of the socket in all the amputees. In the sagittal plane, extension moment was generally increased by posterior translation or flexion of the socket; however, this was not necessarily the case for all the amputees. Interpretations: Individual responses to alignment perturbations are not always consistent, and prosthetists would need to be aware of this variance when addressing individual socket reaction moments during dynamic alignment in clinical setting. © 2014 Elsevier Ltd. All rights reserved.
1. Introduction The alignment of a transtibial prosthesis is tuned through bench, static and dynamic alignment (Blumentritt et al., 1999; Chow et al., 2006; Ikeda et al., 2012; Zahedi et al., 1986). Dynamic alignment of transtibial prostheses is iteratively tuned based on the amputee's reported comfort and prosthetist's observational evaluation of amputee's gait. While this is a highly subjective process, it is currently the accepted standard of clinical practice (Boone et al., 2012; Zahedi et al., 1986). Individual differences in an amputee's gait characteristics along with their individual perceived comfort levels make the dynamic alignment process more challenging for prosthetists. Prosthetic alignment is important because it relates to loading on the residual limb while walking (Kobayashi et al., 2013; Kobayashi et al., 2014b), and socket discomfort is an important issue for amputees (Klute et al., 2009). One way to quantify this loading is to measure forces and moments directly on the
prosthesis (Boone et al., 2013; Frossard et al., 2003; Neumann et al., 2013; Sanders et al., 1997). Previous studies investigated the effect of alignment perturbations on the group mean socket reaction moments in transtibial prostheses (Boone et al., 2013; Kobayashi et al., 2014a). Perturbations to socket alignment induced systematic changes in the mean socket reaction moments. However, individual data are also valuable because each amputee's gait pattern is unique and deviates to some extent from the group mean. In other words, no amputee's gait is average. To fully utilize the socket reaction moments for dynamic alignment in the clinical setting for individualized care, it is important for prosthetists to comprehend and familiarize themselves with individual variances in response to alignment perturbations in amputees. The aim of this study was to investigate individual responses to alignment perturbations in transtibial prostheses. 2. Methods
⁎ Corresponding author at: Orthocare Innovations, 6405 218th St. SW, Suite 301 Mountlake Terrace, WA 98043-2180, USA. E-mail addresses: [email protected], [email protected] (T. Kobayashi).
2.1. Participants Eleven individuals (1 female/10 males; 47(13) years old) who were users of unilateral transtibial prostheses with SACH (solid ankle cushion
http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002 0268-0033/© 2014 Elsevier Ltd. All rights reserved.
Please cite this article as: Kobayashi, T., et al., Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002
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T. Kobayashi et al. / Clinical Biomechanics xxx (2014) xxx–xxx
heel) feet were recruited from the community. Their mean height was 168(8) cm and mean mass was 70(16) kg. The study was approved by the Human Subjects Ethics Committee of The Hong Kong Polytechnic University, and informed consent was obtained from each subject. 2.2. Procedures A custom instrumented prosthesis alignment component was used to measure the socket reaction moments (Fig. 1) (Boone et al., 2013). It was attached to the base of each amputee's prosthetic socket. The prosthesis was aligned based on the standard of current clinical practice (i.e. through agreement between the prosthetist and the amputee). Subsequently, the alignment was randomly perturbed in the sagittal and coronal planes by 3° and 6° (flexion, extension, abduction and adduction of the socket) and by 5 mm and 10 mm (anterior, posterior, medial and lateral translations of the socket). Each amputee was instructed to walk at a self-selected walking speed under each alignment condition. The sampling frequency for the data collection was 100 Hz. The data were sent wirelessly from the instrumented prosthesis alignment component to a computer. 2.3. Data processing The socket reaction moments were normalized temporally to stance with 1% increments using an interpolation with a cubic spline function. The socket reaction moments of three consecutive steps were normalized to body mass (Nm/kg) and averaged in each individual. Fig. 1 presents the mean sagittal and coronal socket reaction moment curves during stance collected from the 11 amputees with transtibial prostheses (Kobayashi et al., 2013). Two socket reaction moment parameters: the moment at 30% of stance phase from the coronal moment and the maximum moment from the sagittal moment were extracted to
investigate the individual responses to alignment perturbations (Fig. 1) (Boone et al., 2013). The two parameters for each participant and their mean were plotted as a function of alignment conditions in the coronal and sagittal planes (Figs. 2 and 3). Valgus moments in the coronal plane and extension moments in the sagittal plane were defined as positive. Cadence (steps/min) was also measured at the baseline alignment, and its correlation with maximum sagittal moments was analyzed by a Pearson's correlation analysis. 3. Results 3.1. Effect of coronal alignment perturbations on coronal moments The varus moment at 30% of stance was generally reduced by adduction or medial translation of the socket in all the participants (Fig. 2). For the coronal angle alignment perturbations, the ranges of moments at 30% were from − 0.254 to − 0.037 Nm/kg at 6° of abduction, from − 0.235 to − 0.012 Nm/kg at 3° of abduction, from − 0.175 to 0.054 Nm/kg at baseline alignment, from − 0.117 to 0.094 Nm/kg at 3° of adduction, and from − 0.049 to 0.183 Nm/kg at 6° of adduction (Fig. 2A). For the coronal translation alignment perturbations, the ranges of moments at 30% were from − 0.277 to − 0.008 Nm/kg at 10 mm of lateral translation, from −0.220 to 0.032 Nm/kg at 5 mm of lateral translation, from − 0.170 to 0.120 Nm/kg at 5 mm of medial translation and from −0.059 to 0.155 Nm/kg at 10 mm of medial translation (Fig. 2B). 3.2. Effect of sagittal alignment perturbations on sagittal moments The extension moment was generally increased by posterior translation or flexion of the socket; however, this was not necessarily the case for all the participants. Variable responses were observed more in angle
Fig. 1. The mean socket reaction moments of the eleven participants during stance in the sagittal and coronal plane at the baseline alignment (Kobayashi et al., 2013). The instrumented prosthesis alignment component is constructed with the following components. A: Tilt sensors, B: transverse rotation adjuster, C: force transducer, D: sagittal and coronal angle adjuster, E: sagittal and coronal translation adjuster, F: modular prosthesis connectors.
Please cite this article as: Kobayashi, T., et al., Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002
T. Kobayashi et al. / Clinical Biomechanics xxx (2014) xxx–xxx
3
A
B
Fig. 2. Individual responses of the coronal moments at 30% of stance to the (A) coronal angle alignment perturbations and (B) coronal translation alignment perturbations. External valgus moments were defined as positive, while external varus moments were defined as negative in the coronal socket reaction moments.
alignment perturbations. For the sagittal angle alignment perturbations, the ranges of the maximum moments was 0.290 to 0.953 Nm/kg at 6° of extension, from 0.439 to 0.995 Nm/kg at 3° of extension, from 0.512 to 0.993 Nm/kg at baseline alignment, from 0.459 to 0.991 Nm/kg at 3°
of flexion, and from 0.509 to 1.061 Nm/kg at 6° of flexion (Fig. 3A). For the sagittal translation alignment perturbations, the ranges of the maximum moments was 0.400 to 0.861 Nm/kg at 10 mm of anterior translation, from 0.457 to 0.941 Nm/kg at 5 mm of anterior translation,
Please cite this article as: Kobayashi, T., et al., Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002
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T. Kobayashi et al. / Clinical Biomechanics xxx (2014) xxx–xxx
A
B
Fig. 3. Individual responses of the maximum sagittal moments to the (A) sagittal angle alignment perturbations and (B) sagittal translation alignment perturbations. External extension moments were defined as positive, while external flexion moments were defined as negative in the sagittal socket reaction moments.
from 0.568 to 0.995 Nm/kg at 5 mm of posterior translation, and 0.641 to 1.082 Nm/kg at 10 mm of posterior translation (Fig. 3B).
3.3. Correlations between cadence and sagittal maximum moments The Pearson's correlation analysis revealed a significant correlation between cadence and maximum sagittal moments at the baseline alignment with Pearson's r of 0.982 (P b 0.01) (Fig. 4).
4. Discussion This study investigated individual responses to alignment perturbations in 11 amputees with transtibial prostheses. The effect of sagittal alignment perturbations on the maximum sagittal moments was not as consistent as the effect of coronal alignment perturbations on the coronal moments at 30% of stance. This result suggested that when using the sagittal socket reaction moments for dynamic alignment, prosthetists would especially need to be cautious about individual differences
Please cite this article as: Kobayashi, T., et al., Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002
T. Kobayashi et al. / Clinical Biomechanics xxx (2014) xxx–xxx
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could be unique to some individuals even when wearing the same prosthetic foot type. Additional factors that might affect differences in individual responses to alignment perturbations may include gait pattern, stability, age, residual limb length, contracture, or strength of lowerlimb muscles. However, further study is required in this area. The effect of different types of prosthetic feet on the socket reaction moments should also be explored (Kobayashi et al., 2014a). 5. Conclusions The results of this study suggest that individual responses to the alignment perturbations may be less consistent among some amputees, and prosthetists would need to be aware of this variance when applying the socket reaction moments for dynamic alignment in the clinical setting. Further study is warranted for clinical implementation of the socket reaction moments for dynamic alignment to advance individual care of amputees. Conflict of interest Fig. 4. A correlation between maximum sagittal moments and cadence at baseline alignment.
in response to alignment adjustments in the sagittal plane. On the other hand, the coronal socket reaction moments generally showed consistent changes in response to alignment perturbations across the participants. Therefore, the coronal socket reaction moments would be a more reliable measure for dynamic alignment. However, for both sagittal and coronal alignment perturbations, some individuals showed fairly linear responses, while others showed some irregular, zigzag- or parabola-pattern responses. The significant correlation between cadence and maximum sagittal moments suggested that the magnitude of individual amputees' socket reaction moments could be influenced by an amputee's self-selected walking speed. However, the previous studies suggested that cadence did not solely explain the changes in the socket reaction moments induced by alignment changes (Boone et al., 2013; Kobayashi et al., 2014a). Sagittal translation alignment perturbations appeared to have more consistent and linear changes across the participants in comparison to sagittal angle alignment perturbations. For the sagittal translation alignment perturbations, 10 mm of posterior translation increased the sagittal maximum moment compared to 10 mm of anterior translation, except for Subject 5. For the sagittal angle alignment perturbations, 6° of flexion increased the sagittal maximum moment compared to 6° of extension, except for Subjects 3 and 5. Both posterior translation and flexion of the socket position the foot more anteriorly, resulting in increases in the maximum moment potentially due to a longer forefoot lever arm. However, the data from this study suggest that an amputee would respond to the angle and translation alignment perturbations differently. The differences in the moment patterns during walking may be related to socket fit, with some individuals exhibiting a broad plateau of alignments that have little effect on the peak moments, while others change slightly with each perturbation. This suggests a tolerance for alignment changes in some, while others exhibit a highly sensitive response to alignment changes. Previous work has shown that broad ranges of angle alignment changes are acceptable to some amputees (Zahedi et al., 1986). Further, the perception of the resultant kinetic consequences of alignment perturbations (i.e. changes in tissue loads) in amputees has been demonstrated to be quite imprecise (Boone et al., 2012). However, the reason for this is unknown. All participants used SACH feet for data collection. Therefore, the results of this study suggested that responses to alignment perturbations
Authors of the manuscript (Kobayashi T, Orendurff MS, and Boone DA) are currently employees of the company that manufactures the Europa™ (formerly known as Smart Pyramid™), a prosthesis component developed to measure socket reaction moments. Acknowledgment This project was supported by an internal research grant of The Hong Kong Polytechnic University. References Blumentritt, S., Schmalz, T., Jarasch, R., Schneider, M., 1999. Effects of sagittal plane prosthetic alignment on standing trans-tibial amputee knee loads. Prosthet. Orthot. Int. 23, 231–238. Boone, D.A., Kobayashi, T., Chou, T.G., Arabian, A.K., Coleman, K.L., Orendurff, M.S., Zhang, M., 2012. Perception of socket alignment perturbations in amputees with transtibial prostheses. J. Rehabil. Res. Dev. 49, 843–854. Boone, D.A., Kobayashi, T., Chou, T.G., Arabian, A.K., Coleman, K.L., Orendurff, M.S., Zhang, M., 2013. Influence of malalignment on socket reaction moments during gait in amputees with transtibial prostheses. Gait Posture 37, 620–626. Chow, D.H., Holmes, A.D., Lee, C.K., Sin, S.W., 2006. The effect of prosthesis alignment on the symmetry of gait in subjects with unilateral transtibial amputation. Prosthet. Orthot. Int. 30, 114–128. Frossard, L., Beck, J., Dillon, M., Chappell, M., Evans, J., 2003. Development and preliminary testing of a device for the direct measurement of forces and moments in the prosthetic limb of transfemoral amputees during activities of daily living. J. Prosthet. Orthot. 15, 135–142. Ikeda, A.J., Reisinger, K.D., Malkush, M., Wu, Y., Edwards, M.L., Kistenberg, R.S., 2012. A priori alignment of transtibial prostheses: a comparison and evaluation of three methods. Disabil. Rehabil. Assist. Technol. 7, 381–388. Klute, G.K., Kantor, C., Darrouzet, C., Wild, H., Wilkinson, S., Iveljic, S., Creasey, G., 2009. Lower-limb amputee needs assessment using multistakeholder focus-group approach. J. Rehabil. Res. Dev. 46, 293–304. Kobayashi, T., Orendurff, M.S., Zhang, M., Boone, D.A., 2013. Effect of alignment changes on sagittal and coronal socket reaction moment interactions in transtibial prostheses. J. Biomech. 46, 1343–1350. Kobayashi, T., Arabian, A.K., Orendurff, M.S., Chou, T.G., Boone, D.A., 2014a. Effect of alignment changes on socket reaction moments while walking in transtibial prostheses with energy storage and return feet. Clin. Biomech. 29, 47–56. Kobayashi, T., Orendurff, M.S., Arabian, A.K., Rosenbaum-Chou, T.G., Boone, D.A., 2014b. Effect of prosthetic alignment changes on socket reaction moment impulse during walking in transtibial amputees. J. Biomech. 47, 1315–1323. Neumann, E.S., Brink, J., Yalamanchili, K., Lee, J.S., 2013 Aug 6. Use of a load cell and forcemoment curves to compare transverse plane moment loads on transtibial residual limbs: a preliminary investigation. Prosthet Orthot Int.. http://dx.doi.org/10.1177/ 0309364613497048. Sanders, J.E., Miller, R.A., Berglund, D.N., Zachariah, S.G., 1997. A modular six-directional force sensor for prosthetic assessment: a technical note. J. Rehabil. Res. Dev. 34, 195–202. Zahedi, M.S., Spence, W.D., Solomonidis, S.E., Paul, J.P., 1986. Alignment of lower-limb prostheses. J. Rehabil. Res. Dev. 23, 2–19.
Please cite this article as: Kobayashi, T., et al., Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002
Contents lists available at ScienceDirect
Clinical Biomechanics journal homepage: www.elsevier.com/locate/clinbiomech
Brief report
Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses Toshiki Kobayashi a,⁎, Michael S. Orendurff a, Ming Zhang b, David A. Boone a a b
Orthocare Innovations, Mountlake Terrace, WA, USA Interdisciplinary Division of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Hong Kong, China
a r t i c l e
i n f o
Article history: Received 15 February 2014 Accepted 7 April 2014 Keywords: Amputation Direct measurement Gait Kinetic Malalignment SACH foot
a b s t r a c t Background: The alignment of transtibial prostheses has a systematic effect on the mean socket reaction moments in amputees. However, understanding their individual differences in response to alignment perturbations is also important for prosthetists to fully utilize the socket reaction moments for dynamic alignment in each unique patient. The aim of this study was to investigate individual responses to alignment perturbations in transtibial prostheses with solid-ankle-cushion-heel feet. Methods: A custom instrumented prosthesis alignment component was used to measure the socket reaction moments while walking in 11 amputees with transtibial prostheses under 17 alignment conditions, including 3° and 6° of flexion, extension, abduction, and adduction of the socket, 5 mm and 10 mm of anterior, posterior, lateral, and medial translation of the socket, and an initial baseline alignment. Coronal moments at 30% of stance and maximum sagittal moments were extracted for comparisons from each amputee. Findings: In the coronal plane, varus moment at 30% of stance was generally reduced by adduction or medial translation of the socket in all the amputees. In the sagittal plane, extension moment was generally increased by posterior translation or flexion of the socket; however, this was not necessarily the case for all the amputees. Interpretations: Individual responses to alignment perturbations are not always consistent, and prosthetists would need to be aware of this variance when addressing individual socket reaction moments during dynamic alignment in clinical setting. © 2014 Elsevier Ltd. All rights reserved.
1. Introduction The alignment of a transtibial prosthesis is tuned through bench, static and dynamic alignment (Blumentritt et al., 1999; Chow et al., 2006; Ikeda et al., 2012; Zahedi et al., 1986). Dynamic alignment of transtibial prostheses is iteratively tuned based on the amputee's reported comfort and prosthetist's observational evaluation of amputee's gait. While this is a highly subjective process, it is currently the accepted standard of clinical practice (Boone et al., 2012; Zahedi et al., 1986). Individual differences in an amputee's gait characteristics along with their individual perceived comfort levels make the dynamic alignment process more challenging for prosthetists. Prosthetic alignment is important because it relates to loading on the residual limb while walking (Kobayashi et al., 2013; Kobayashi et al., 2014b), and socket discomfort is an important issue for amputees (Klute et al., 2009). One way to quantify this loading is to measure forces and moments directly on the
prosthesis (Boone et al., 2013; Frossard et al., 2003; Neumann et al., 2013; Sanders et al., 1997). Previous studies investigated the effect of alignment perturbations on the group mean socket reaction moments in transtibial prostheses (Boone et al., 2013; Kobayashi et al., 2014a). Perturbations to socket alignment induced systematic changes in the mean socket reaction moments. However, individual data are also valuable because each amputee's gait pattern is unique and deviates to some extent from the group mean. In other words, no amputee's gait is average. To fully utilize the socket reaction moments for dynamic alignment in the clinical setting for individualized care, it is important for prosthetists to comprehend and familiarize themselves with individual variances in response to alignment perturbations in amputees. The aim of this study was to investigate individual responses to alignment perturbations in transtibial prostheses. 2. Methods
⁎ Corresponding author at: Orthocare Innovations, 6405 218th St. SW, Suite 301 Mountlake Terrace, WA 98043-2180, USA. E-mail addresses: [email protected], [email protected] (T. Kobayashi).
2.1. Participants Eleven individuals (1 female/10 males; 47(13) years old) who were users of unilateral transtibial prostheses with SACH (solid ankle cushion
http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002 0268-0033/© 2014 Elsevier Ltd. All rights reserved.
Please cite this article as: Kobayashi, T., et al., Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002
2
T. Kobayashi et al. / Clinical Biomechanics xxx (2014) xxx–xxx
heel) feet were recruited from the community. Their mean height was 168(8) cm and mean mass was 70(16) kg. The study was approved by the Human Subjects Ethics Committee of The Hong Kong Polytechnic University, and informed consent was obtained from each subject. 2.2. Procedures A custom instrumented prosthesis alignment component was used to measure the socket reaction moments (Fig. 1) (Boone et al., 2013). It was attached to the base of each amputee's prosthetic socket. The prosthesis was aligned based on the standard of current clinical practice (i.e. through agreement between the prosthetist and the amputee). Subsequently, the alignment was randomly perturbed in the sagittal and coronal planes by 3° and 6° (flexion, extension, abduction and adduction of the socket) and by 5 mm and 10 mm (anterior, posterior, medial and lateral translations of the socket). Each amputee was instructed to walk at a self-selected walking speed under each alignment condition. The sampling frequency for the data collection was 100 Hz. The data were sent wirelessly from the instrumented prosthesis alignment component to a computer. 2.3. Data processing The socket reaction moments were normalized temporally to stance with 1% increments using an interpolation with a cubic spline function. The socket reaction moments of three consecutive steps were normalized to body mass (Nm/kg) and averaged in each individual. Fig. 1 presents the mean sagittal and coronal socket reaction moment curves during stance collected from the 11 amputees with transtibial prostheses (Kobayashi et al., 2013). Two socket reaction moment parameters: the moment at 30% of stance phase from the coronal moment and the maximum moment from the sagittal moment were extracted to
investigate the individual responses to alignment perturbations (Fig. 1) (Boone et al., 2013). The two parameters for each participant and their mean were plotted as a function of alignment conditions in the coronal and sagittal planes (Figs. 2 and 3). Valgus moments in the coronal plane and extension moments in the sagittal plane were defined as positive. Cadence (steps/min) was also measured at the baseline alignment, and its correlation with maximum sagittal moments was analyzed by a Pearson's correlation analysis. 3. Results 3.1. Effect of coronal alignment perturbations on coronal moments The varus moment at 30% of stance was generally reduced by adduction or medial translation of the socket in all the participants (Fig. 2). For the coronal angle alignment perturbations, the ranges of moments at 30% were from − 0.254 to − 0.037 Nm/kg at 6° of abduction, from − 0.235 to − 0.012 Nm/kg at 3° of abduction, from − 0.175 to 0.054 Nm/kg at baseline alignment, from − 0.117 to 0.094 Nm/kg at 3° of adduction, and from − 0.049 to 0.183 Nm/kg at 6° of adduction (Fig. 2A). For the coronal translation alignment perturbations, the ranges of moments at 30% were from − 0.277 to − 0.008 Nm/kg at 10 mm of lateral translation, from −0.220 to 0.032 Nm/kg at 5 mm of lateral translation, from − 0.170 to 0.120 Nm/kg at 5 mm of medial translation and from −0.059 to 0.155 Nm/kg at 10 mm of medial translation (Fig. 2B). 3.2. Effect of sagittal alignment perturbations on sagittal moments The extension moment was generally increased by posterior translation or flexion of the socket; however, this was not necessarily the case for all the participants. Variable responses were observed more in angle
Fig. 1. The mean socket reaction moments of the eleven participants during stance in the sagittal and coronal plane at the baseline alignment (Kobayashi et al., 2013). The instrumented prosthesis alignment component is constructed with the following components. A: Tilt sensors, B: transverse rotation adjuster, C: force transducer, D: sagittal and coronal angle adjuster, E: sagittal and coronal translation adjuster, F: modular prosthesis connectors.
Please cite this article as: Kobayashi, T., et al., Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002
T. Kobayashi et al. / Clinical Biomechanics xxx (2014) xxx–xxx
3
A
B
Fig. 2. Individual responses of the coronal moments at 30% of stance to the (A) coronal angle alignment perturbations and (B) coronal translation alignment perturbations. External valgus moments were defined as positive, while external varus moments were defined as negative in the coronal socket reaction moments.
alignment perturbations. For the sagittal angle alignment perturbations, the ranges of the maximum moments was 0.290 to 0.953 Nm/kg at 6° of extension, from 0.439 to 0.995 Nm/kg at 3° of extension, from 0.512 to 0.993 Nm/kg at baseline alignment, from 0.459 to 0.991 Nm/kg at 3°
of flexion, and from 0.509 to 1.061 Nm/kg at 6° of flexion (Fig. 3A). For the sagittal translation alignment perturbations, the ranges of the maximum moments was 0.400 to 0.861 Nm/kg at 10 mm of anterior translation, from 0.457 to 0.941 Nm/kg at 5 mm of anterior translation,
Please cite this article as: Kobayashi, T., et al., Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002
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T. Kobayashi et al. / Clinical Biomechanics xxx (2014) xxx–xxx
A
B
Fig. 3. Individual responses of the maximum sagittal moments to the (A) sagittal angle alignment perturbations and (B) sagittal translation alignment perturbations. External extension moments were defined as positive, while external flexion moments were defined as negative in the sagittal socket reaction moments.
from 0.568 to 0.995 Nm/kg at 5 mm of posterior translation, and 0.641 to 1.082 Nm/kg at 10 mm of posterior translation (Fig. 3B).
3.3. Correlations between cadence and sagittal maximum moments The Pearson's correlation analysis revealed a significant correlation between cadence and maximum sagittal moments at the baseline alignment with Pearson's r of 0.982 (P b 0.01) (Fig. 4).
4. Discussion This study investigated individual responses to alignment perturbations in 11 amputees with transtibial prostheses. The effect of sagittal alignment perturbations on the maximum sagittal moments was not as consistent as the effect of coronal alignment perturbations on the coronal moments at 30% of stance. This result suggested that when using the sagittal socket reaction moments for dynamic alignment, prosthetists would especially need to be cautious about individual differences
Please cite this article as: Kobayashi, T., et al., Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002
T. Kobayashi et al. / Clinical Biomechanics xxx (2014) xxx–xxx
5
could be unique to some individuals even when wearing the same prosthetic foot type. Additional factors that might affect differences in individual responses to alignment perturbations may include gait pattern, stability, age, residual limb length, contracture, or strength of lowerlimb muscles. However, further study is required in this area. The effect of different types of prosthetic feet on the socket reaction moments should also be explored (Kobayashi et al., 2014a). 5. Conclusions The results of this study suggest that individual responses to the alignment perturbations may be less consistent among some amputees, and prosthetists would need to be aware of this variance when applying the socket reaction moments for dynamic alignment in the clinical setting. Further study is warranted for clinical implementation of the socket reaction moments for dynamic alignment to advance individual care of amputees. Conflict of interest Fig. 4. A correlation between maximum sagittal moments and cadence at baseline alignment.
in response to alignment adjustments in the sagittal plane. On the other hand, the coronal socket reaction moments generally showed consistent changes in response to alignment perturbations across the participants. Therefore, the coronal socket reaction moments would be a more reliable measure for dynamic alignment. However, for both sagittal and coronal alignment perturbations, some individuals showed fairly linear responses, while others showed some irregular, zigzag- or parabola-pattern responses. The significant correlation between cadence and maximum sagittal moments suggested that the magnitude of individual amputees' socket reaction moments could be influenced by an amputee's self-selected walking speed. However, the previous studies suggested that cadence did not solely explain the changes in the socket reaction moments induced by alignment changes (Boone et al., 2013; Kobayashi et al., 2014a). Sagittal translation alignment perturbations appeared to have more consistent and linear changes across the participants in comparison to sagittal angle alignment perturbations. For the sagittal translation alignment perturbations, 10 mm of posterior translation increased the sagittal maximum moment compared to 10 mm of anterior translation, except for Subject 5. For the sagittal angle alignment perturbations, 6° of flexion increased the sagittal maximum moment compared to 6° of extension, except for Subjects 3 and 5. Both posterior translation and flexion of the socket position the foot more anteriorly, resulting in increases in the maximum moment potentially due to a longer forefoot lever arm. However, the data from this study suggest that an amputee would respond to the angle and translation alignment perturbations differently. The differences in the moment patterns during walking may be related to socket fit, with some individuals exhibiting a broad plateau of alignments that have little effect on the peak moments, while others change slightly with each perturbation. This suggests a tolerance for alignment changes in some, while others exhibit a highly sensitive response to alignment changes. Previous work has shown that broad ranges of angle alignment changes are acceptable to some amputees (Zahedi et al., 1986). Further, the perception of the resultant kinetic consequences of alignment perturbations (i.e. changes in tissue loads) in amputees has been demonstrated to be quite imprecise (Boone et al., 2012). However, the reason for this is unknown. All participants used SACH feet for data collection. Therefore, the results of this study suggested that responses to alignment perturbations
Authors of the manuscript (Kobayashi T, Orendurff MS, and Boone DA) are currently employees of the company that manufactures the Europa™ (formerly known as Smart Pyramid™), a prosthesis component developed to measure socket reaction moments. Acknowledgment This project was supported by an internal research grant of The Hong Kong Polytechnic University. References Blumentritt, S., Schmalz, T., Jarasch, R., Schneider, M., 1999. Effects of sagittal plane prosthetic alignment on standing trans-tibial amputee knee loads. Prosthet. Orthot. Int. 23, 231–238. Boone, D.A., Kobayashi, T., Chou, T.G., Arabian, A.K., Coleman, K.L., Orendurff, M.S., Zhang, M., 2012. Perception of socket alignment perturbations in amputees with transtibial prostheses. J. Rehabil. Res. Dev. 49, 843–854. Boone, D.A., Kobayashi, T., Chou, T.G., Arabian, A.K., Coleman, K.L., Orendurff, M.S., Zhang, M., 2013. Influence of malalignment on socket reaction moments during gait in amputees with transtibial prostheses. Gait Posture 37, 620–626. Chow, D.H., Holmes, A.D., Lee, C.K., Sin, S.W., 2006. The effect of prosthesis alignment on the symmetry of gait in subjects with unilateral transtibial amputation. Prosthet. Orthot. Int. 30, 114–128. Frossard, L., Beck, J., Dillon, M., Chappell, M., Evans, J., 2003. Development and preliminary testing of a device for the direct measurement of forces and moments in the prosthetic limb of transfemoral amputees during activities of daily living. J. Prosthet. Orthot. 15, 135–142. Ikeda, A.J., Reisinger, K.D., Malkush, M., Wu, Y., Edwards, M.L., Kistenberg, R.S., 2012. A priori alignment of transtibial prostheses: a comparison and evaluation of three methods. Disabil. Rehabil. Assist. Technol. 7, 381–388. Klute, G.K., Kantor, C., Darrouzet, C., Wild, H., Wilkinson, S., Iveljic, S., Creasey, G., 2009. Lower-limb amputee needs assessment using multistakeholder focus-group approach. J. Rehabil. Res. Dev. 46, 293–304. Kobayashi, T., Orendurff, M.S., Zhang, M., Boone, D.A., 2013. Effect of alignment changes on sagittal and coronal socket reaction moment interactions in transtibial prostheses. J. Biomech. 46, 1343–1350. Kobayashi, T., Arabian, A.K., Orendurff, M.S., Chou, T.G., Boone, D.A., 2014a. Effect of alignment changes on socket reaction moments while walking in transtibial prostheses with energy storage and return feet. Clin. Biomech. 29, 47–56. Kobayashi, T., Orendurff, M.S., Arabian, A.K., Rosenbaum-Chou, T.G., Boone, D.A., 2014b. Effect of prosthetic alignment changes on socket reaction moment impulse during walking in transtibial amputees. J. Biomech. 47, 1315–1323. Neumann, E.S., Brink, J., Yalamanchili, K., Lee, J.S., 2013 Aug 6. Use of a load cell and forcemoment curves to compare transverse plane moment loads on transtibial residual limbs: a preliminary investigation. Prosthet Orthot Int.. http://dx.doi.org/10.1177/ 0309364613497048. Sanders, J.E., Miller, R.A., Berglund, D.N., Zachariah, S.G., 1997. A modular six-directional force sensor for prosthetic assessment: a technical note. J. Rehabil. Res. Dev. 34, 195–202. Zahedi, M.S., Spence, W.D., Solomonidis, S.E., Paul, J.P., 1986. Alignment of lower-limb prostheses. J. Rehabil. Res. Dev. 23, 2–19.
Please cite this article as: Kobayashi, T., et al., Individual responses to alignment perturbations in socket reaction moments while walking in transtibial prostheses, Clin. Biomech. (2014), http://dx.doi.org/10.1016/j.clinbiomech.2014.04.002
