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Dear Biomch-L subscribers,
Thanks to all for your helpful responses to my post on the above subject
(see below for original post) and apologies for the delay in sending
this in. I have compiled a summary of responses below from those happy
to have their messages posted. Also pls refer to #025983 for additional
response from Allan Carman (many thanks!).
There was agreement amongst several respondents that the marker set and
model employed should be chosen to reflect the outcome measures of
interest, and a general indication of preference for segment based 6DOF
modelling with functional estimations of joint centres of rotation in
this context.
There does not appear to be any standard protocol for placement on lower
limb prosthetic components, particularly those that do not resemble
anatomical counterparts either cosmetically or functionally (e.g.
running blades, energy store and release feet, SACH feet,
shock-absorbing pylons). The outcome-measure driven approach to
selecting landmarks certainly seems most appropriate, rather than trying
to exploit a generic model that cannot describe what's going on
functionally, but this limits comparison against other data sets both
within centre and across institutions.
Inter-limb kinematic comparisons (e.g. in the case of unilateral
amputees) are complicated in that you may be trying to compare two
systems that are geometrically and/or functionally different for a start
and any analysis from extracted data must account for this (a simple
example would be comparing peak transverse rotations from 6DOF data from
a sound thigh segment and a prosthetic one that is NOT subject to soft
tissue artefact). Zero conditions are particularly difficult to
establish with the different limb geometries/mechanisms and alignments
(these may be under investigation themselves).
I have been keen to explore the use of landmark-based 3D motion capture
for amputee assessment in a clinical context due to the lack of outcome
measures for higher activity amputee cohorts.
However, given the above issues on top of the general issues of
reliability of the method as a whole (pls see /?for a very useful
summary of this) maybe its application should be restricted to isolated
cases of interest where a higher level of control can be imposed, rather
than routine clinical work. ie. I should compromise on my generic model
and avoid /?comparing outside the context of the individual patient. I
haven't even begun to consider moments, powers and energy transfer
mechanisms!
Thanks once again for your input on this.
Kind regards
Jenny
----------------------------------------------
Dear Jenny Kent,
I am Pietro Garofalo. I spent my PhD activities at INAIL Prostheses
Centre (Bologna, Italy) dealing with exactly the same problems you
explained in your post.
Therefore it was very easy for me to understand your opinions, both for
the analysis of kinematics and kinetics.
I also definitely agree with you that all the research around amputee
should start from which is the clinical questions to answer to.
For this reason I would like to inform you that I recently completed my
PhD thesis in which, from one side, specific protocols were defined for
the analysis of amputees using stereophotogrammetry and, from the other
side, alternative solutions (in which also functional method are
involved) based on inertial sensors were proposed.
I am now in fact in Xsens Technologies B.V. and together with INAIL
Prostheses Centre the above research is still going on.
In particular, a protocol was recently proposed by for the 3D kinematics
measurements of gait analysis adopting inertial sensors.
See http://www.ncbi.nlm.nih.gov/pubmed/19911214 .
I invite you to contact Andrea Giovanni Cutti from INAIL Prostheses
Centre from which everything started and then, if you are interested, as
soon as my thesis will be printed out, you may receive a copy of it.
You can also have the possibility to meet Mr. Cutti at ISPO 2010
(Leipzig) on next May in which the application of the above protocol on
above-knee amputees received an oral presentation.
Of course I am open to further discussions (I really would like to
discuss on Biomech-L about this topic, which is still, in my opinion,
far from being established among the community).
Pietro Garofalo
Technical Product Manager - Movement Science
Xsens - 10 Years in Motion
----------------------------------------------
Dear Jenny Kent, I've been struggling on similar sorts of issues as
well, looking at amputees and patients wearing knee orthosis. We are
exploiting the recent protocol we've published recently (Leardini et al.
Gait Posture.
2007 Oct;26(4):560-71), also encouraged by a following quantitative
comparison (Ferrari et al Gait Posture. 2008 Aug;28(2):207-16), and a
recent study (under review) where relevant inter-session and
inter-examiner repeatability was found better than previous reports.
I've no solutions for you at the moment, but just these readings for
your knowledge. Do not hesitate for any further information.
Very kind regards,
************************************************** *******************
Alberto Leardini
************************************************** *******************
----------------------------------------------
My experience is in trying to build a functional anthropometric model to
use with CAD systems for design of worker/operator environments. While
reading of your efforts, I wondered if data has been collected on
pre-amputee subjects which could then be coordinated with post-amputee
subjects. I realize this may not be practical since, most likely, the
amputee most likely had a debilitating condition or injury that
necessitated the amputation. Knowing that a pre-amputee subject will
undergo amputation, one could place markers as necessary to provide
comparable locations for measurement post-amputation. I don't know if
this is of any value to you, but it did occur to me as I read your
query.
As to a uniform data collection, I would envision markers located on
torso, pelvis, upper leg, lower leg, and foot. These would not just be
at the joints, but at equally spaced distances between the joints. In
this way you be able to track markers in images that would be consistent
across subjects. The difficult part is determining what locations and
how to consistently locate them. The soft tissue placement is of course
a most difficult complication to making measures consistent.
One of the issues I repeatedly encountered while attempting to build CAD
manikins was the lack of consistent data collection. The landmarks were
always pretty well defined, but the authors rarely collected all the
same ones making the collation of data nearly impossible. Not all the
necessary data involved the markers, but involved other measures such as
age, height, and weight associated with each individual set of markers
and data collected. Again, none of this may be of use to you.
Hopefully, these anecdotal comments may suggest some paths of
investigation.
Good luck in your endeavors.
Charles Gidcumb
Human Engineering
The Boeing Company
-------------------------------------------------
In the end any marker set will give you the appropriate data about the
movement of the prosthesis, the question of the rotation of the foot
segment/knee segment is where the axes are and hence where you would
place the coordinate system.
Functional joint centres will help to some point but using a segment
based system is likely to be more fruitful than a HH based system. It
really depends on what your primary outcome measures for the gait data
are.
Richard Jones
Senior Lecturer in Clinical Biomechanics / Director of the Salford Gait
laboratory Directorate of Prosthetics & Orthotics and Podiatry
----------------------------------------------
----------------------------------------------
ORIGINAL POST
Dear Biomch-L subscribers,
I'm doing some work on the use of biomechanical models and marker sets
to study the kinematics of lower limb amputees. My efforts were
initially geared towards selecting an appropriate marker set for amputee
analysis that could also be applied broadly to all patient groups and
healthy subjects (as normative controls) to facilitate comparison, with
both clinical and research applications in mind. This would comprise a
standard configuration that could be built upon for specific
applications that require additional segments/parameters to be analysed,
but would ensure data collection uniformity as far as possible.
A lit search I conducted brought up many studies on individual amputees
or amputee cohorts using a variety of marker sets, although the majority
appeared to be some form of Helen Hayes derivative. On the prosthetic
side markers were commonly placed on mechanical centres of rotation
where obvious (e.g. on single axis joints) or "estimated from the sound
side".
I was concerned about the appropriateness of the use of several of the
common models and methods when analysing amputee function, particularly
when directly comparing the function/movement of prosthetic and sound
limbs. Examples of such applications would be comparing prosthetic gait
to normative data, evaluating limb symmetry (is this appropriate
anyway?! I'm doubtful in most cases, esp when it concerns unilateral
amputees), and comparing components that function differently
mechanically (e.g. 4-bar knee vs single axis knee, SACH foot vs foot
with articulated ankle joint).
I imagine it may be possible to achieve more reliable/valid results (and
a system that may be applied more universally) with joint centres
determined functionally, technical markers for tracking segmental
movement and perhaps the addition of extra markers to monitor relative
movement of the residual limb with respect to the socket (although I
won't even attempt to touch on the issues of placement and treatment of
soft tissue artefact here..). Regarding the selection/development of a
model that will enable prosthetic components that have not been designed
to reproduce natural segment movement to be adequately represented (e.g.
SACH foot, running blades) and that will allow different limb alignments
to be compared (where the neutral condition at joints may be altered by
nature of the study) I am a little lost. I anticipate when I begin to
consider the analysis of joint moments, torques and powers, which
undoubtedly will open yet another can of worms, I will be even more so.
I suspect that my idea of a universally applied base marker set and
model may be unrealistic, even given an allowance for additional
markers/segments for specific analyses, and that with amputee cohorts
kinematic models will have to be more specifically geared towards the
question that the analysis is required to answer.
I would be very grateful if anyone has any thoughts or advice to share
on the subject. I remember there was a very relevant presentation and
discussion at the CMAS UKI annual meeting and conference in Edinburgh
2009 - I am aware that there may be groups specifically looking into it
and I was wondering if there have been any recent developments that I
have not come across. I'll happily post a summary of replies - please
let me know if you'd prefer not to appear in it!
Many thanks
Jenny Kent
Higher Scientific Officer
Centre for Human Performance, Rehabilitation and Sports Medicine DMRC
Headley Court Epsom, Surrey UK
e: DMRC-HSO1@mod.uk
Thanks to all for your helpful responses to my post on the above subject
(see below for original post) and apologies for the delay in sending
this in. I have compiled a summary of responses below from those happy
to have their messages posted. Also pls refer to #025983 for additional
response from Allan Carman (many thanks!).
There was agreement amongst several respondents that the marker set and
model employed should be chosen to reflect the outcome measures of
interest, and a general indication of preference for segment based 6DOF
modelling with functional estimations of joint centres of rotation in
this context.
There does not appear to be any standard protocol for placement on lower
limb prosthetic components, particularly those that do not resemble
anatomical counterparts either cosmetically or functionally (e.g.
running blades, energy store and release feet, SACH feet,
shock-absorbing pylons). The outcome-measure driven approach to
selecting landmarks certainly seems most appropriate, rather than trying
to exploit a generic model that cannot describe what's going on
functionally, but this limits comparison against other data sets both
within centre and across institutions.
Inter-limb kinematic comparisons (e.g. in the case of unilateral
amputees) are complicated in that you may be trying to compare two
systems that are geometrically and/or functionally different for a start
and any analysis from extracted data must account for this (a simple
example would be comparing peak transverse rotations from 6DOF data from
a sound thigh segment and a prosthetic one that is NOT subject to soft
tissue artefact). Zero conditions are particularly difficult to
establish with the different limb geometries/mechanisms and alignments
(these may be under investigation themselves).
I have been keen to explore the use of landmark-based 3D motion capture
for amputee assessment in a clinical context due to the lack of outcome
measures for higher activity amputee cohorts.
However, given the above issues on top of the general issues of
reliability of the method as a whole (pls see /?for a very useful
summary of this) maybe its application should be restricted to isolated
cases of interest where a higher level of control can be imposed, rather
than routine clinical work. ie. I should compromise on my generic model
and avoid /?comparing outside the context of the individual patient. I
haven't even begun to consider moments, powers and energy transfer
mechanisms!
Thanks once again for your input on this.
Kind regards
Jenny
----------------------------------------------
Dear Jenny Kent,
I am Pietro Garofalo. I spent my PhD activities at INAIL Prostheses
Centre (Bologna, Italy) dealing with exactly the same problems you
explained in your post.
Therefore it was very easy for me to understand your opinions, both for
the analysis of kinematics and kinetics.
I also definitely agree with you that all the research around amputee
should start from which is the clinical questions to answer to.
For this reason I would like to inform you that I recently completed my
PhD thesis in which, from one side, specific protocols were defined for
the analysis of amputees using stereophotogrammetry and, from the other
side, alternative solutions (in which also functional method are
involved) based on inertial sensors were proposed.
I am now in fact in Xsens Technologies B.V. and together with INAIL
Prostheses Centre the above research is still going on.
In particular, a protocol was recently proposed by for the 3D kinematics
measurements of gait analysis adopting inertial sensors.
See http://www.ncbi.nlm.nih.gov/pubmed/19911214 .
I invite you to contact Andrea Giovanni Cutti from INAIL Prostheses
Centre from which everything started and then, if you are interested, as
soon as my thesis will be printed out, you may receive a copy of it.
You can also have the possibility to meet Mr. Cutti at ISPO 2010
(Leipzig) on next May in which the application of the above protocol on
above-knee amputees received an oral presentation.
Of course I am open to further discussions (I really would like to
discuss on Biomech-L about this topic, which is still, in my opinion,
far from being established among the community).
Pietro Garofalo
Technical Product Manager - Movement Science
Xsens - 10 Years in Motion
----------------------------------------------
Dear Jenny Kent, I've been struggling on similar sorts of issues as
well, looking at amputees and patients wearing knee orthosis. We are
exploiting the recent protocol we've published recently (Leardini et al.
Gait Posture.
2007 Oct;26(4):560-71), also encouraged by a following quantitative
comparison (Ferrari et al Gait Posture. 2008 Aug;28(2):207-16), and a
recent study (under review) where relevant inter-session and
inter-examiner repeatability was found better than previous reports.
I've no solutions for you at the moment, but just these readings for
your knowledge. Do not hesitate for any further information.
Very kind regards,
************************************************** *******************
Alberto Leardini
************************************************** *******************
----------------------------------------------
My experience is in trying to build a functional anthropometric model to
use with CAD systems for design of worker/operator environments. While
reading of your efforts, I wondered if data has been collected on
pre-amputee subjects which could then be coordinated with post-amputee
subjects. I realize this may not be practical since, most likely, the
amputee most likely had a debilitating condition or injury that
necessitated the amputation. Knowing that a pre-amputee subject will
undergo amputation, one could place markers as necessary to provide
comparable locations for measurement post-amputation. I don't know if
this is of any value to you, but it did occur to me as I read your
query.
As to a uniform data collection, I would envision markers located on
torso, pelvis, upper leg, lower leg, and foot. These would not just be
at the joints, but at equally spaced distances between the joints. In
this way you be able to track markers in images that would be consistent
across subjects. The difficult part is determining what locations and
how to consistently locate them. The soft tissue placement is of course
a most difficult complication to making measures consistent.
One of the issues I repeatedly encountered while attempting to build CAD
manikins was the lack of consistent data collection. The landmarks were
always pretty well defined, but the authors rarely collected all the
same ones making the collation of data nearly impossible. Not all the
necessary data involved the markers, but involved other measures such as
age, height, and weight associated with each individual set of markers
and data collected. Again, none of this may be of use to you.
Hopefully, these anecdotal comments may suggest some paths of
investigation.
Good luck in your endeavors.
Charles Gidcumb
Human Engineering
The Boeing Company
-------------------------------------------------
In the end any marker set will give you the appropriate data about the
movement of the prosthesis, the question of the rotation of the foot
segment/knee segment is where the axes are and hence where you would
place the coordinate system.
Functional joint centres will help to some point but using a segment
based system is likely to be more fruitful than a HH based system. It
really depends on what your primary outcome measures for the gait data
are.
Richard Jones
Senior Lecturer in Clinical Biomechanics / Director of the Salford Gait
laboratory Directorate of Prosthetics & Orthotics and Podiatry
----------------------------------------------
----------------------------------------------
ORIGINAL POST
Dear Biomch-L subscribers,
I'm doing some work on the use of biomechanical models and marker sets
to study the kinematics of lower limb amputees. My efforts were
initially geared towards selecting an appropriate marker set for amputee
analysis that could also be applied broadly to all patient groups and
healthy subjects (as normative controls) to facilitate comparison, with
both clinical and research applications in mind. This would comprise a
standard configuration that could be built upon for specific
applications that require additional segments/parameters to be analysed,
but would ensure data collection uniformity as far as possible.
A lit search I conducted brought up many studies on individual amputees
or amputee cohorts using a variety of marker sets, although the majority
appeared to be some form of Helen Hayes derivative. On the prosthetic
side markers were commonly placed on mechanical centres of rotation
where obvious (e.g. on single axis joints) or "estimated from the sound
side".
I was concerned about the appropriateness of the use of several of the
common models and methods when analysing amputee function, particularly
when directly comparing the function/movement of prosthetic and sound
limbs. Examples of such applications would be comparing prosthetic gait
to normative data, evaluating limb symmetry (is this appropriate
anyway?! I'm doubtful in most cases, esp when it concerns unilateral
amputees), and comparing components that function differently
mechanically (e.g. 4-bar knee vs single axis knee, SACH foot vs foot
with articulated ankle joint).
I imagine it may be possible to achieve more reliable/valid results (and
a system that may be applied more universally) with joint centres
determined functionally, technical markers for tracking segmental
movement and perhaps the addition of extra markers to monitor relative
movement of the residual limb with respect to the socket (although I
won't even attempt to touch on the issues of placement and treatment of
soft tissue artefact here..). Regarding the selection/development of a
model that will enable prosthetic components that have not been designed
to reproduce natural segment movement to be adequately represented (e.g.
SACH foot, running blades) and that will allow different limb alignments
to be compared (where the neutral condition at joints may be altered by
nature of the study) I am a little lost. I anticipate when I begin to
consider the analysis of joint moments, torques and powers, which
undoubtedly will open yet another can of worms, I will be even more so.
I suspect that my idea of a universally applied base marker set and
model may be unrealistic, even given an allowance for additional
markers/segments for specific analyses, and that with amputee cohorts
kinematic models will have to be more specifically geared towards the
question that the analysis is required to answer.
I would be very grateful if anyone has any thoughts or advice to share
on the subject. I remember there was a very relevant presentation and
discussion at the CMAS UKI annual meeting and conference in Edinburgh
2009 - I am aware that there may be groups specifically looking into it
and I was wondering if there have been any recent developments that I
have not come across. I'll happily post a summary of replies - please
let me know if you'd prefer not to appear in it!
Many thanks
Jenny Kent
Higher Scientific Officer
Centre for Human Performance, Rehabilitation and Sports Medicine DMRC
Headley Court Epsom, Surrey UK
e: DMRC-HSO1@mod.uk