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  • replies to : how to define upper limb technical array?

    Date: Fri, 4 Jul 1997 08:58:26 -0300

    I'm a doctoral candidate, preparing for thesis experiments, and am faced
    with the question of whether to use individual markers mounted on definable
    "landmarks" on the upper limbs, or whether one is better using
    technical arrays of markers on a common base. While individually mounted
    markers are generally self-explanatory (except how to define the
    limb segments based on the surface markers), I wonder
    how to mount, stabilize and place technical array groupings.
    I am assuming the arrays would be placed on the upper arm, forearm and
    My questions are:
    1) Schmidt et al. (1994) suggest using "foam rubber", and elsewhere I have
    read of neoprene. Sounds HOT. Why not a lighter material like tubigrip
    (cotton-rubber bandage material)? Would the flexibility of such a
    material allow too much individual marker movement?

    2) How are the arrays mounted and stabilized on differently sized arms
    - are markers on the arrays moved to be proportionally located similarly
    on small and large segments?
    - does consistency of marker placement on the "base" material matter if a
    "calibration" is made with markers over joints?
    - what assumptions of joint centres does such a calibrating technique

    3) What information would potentially be lost by using technical arrays
    rather than individual markers?

    I will be using a 3 camera VICON 140 system for recording arm
    movements during activities of daily living.
    Your suggestions and comments are most appreciated. I will post a
    summary of the replies.


    Firstly, I apologize for the incomplete reference in my note. Schmidt
    et al. (1994) was by Schmidt, R. Disselhorst-Klug, C., Silny, J.,
    Rau, G., "Measurement of Cardan Angles and Helical Axis at wrist and elbow
    joints during free upper extremity movements", in the Proceedings of the
    4th International Symposium on 3D Analysis of Human Movement, Grenoble, France
    (4 pages long, but I don't have page number) ....

    In direct response to my questions:
    1. on what sort of base material may one mount technical arrays
    - on just about anything... rigid materials or flexible ones
    - Liduin Meershoek mentioned mounting them on velcro strips for the arm
    segments and elastic bandage for the hand
    - the work out of Oxford University tends to use rigid bases,
    although possibly flexible ones may be used. (Leardini)
    - markers may be raised to some distance from the skin, or essentially
    at skin level. (3cm up wiht 5-8 cm span between each of 4 in a unique
    pattern per limb - Williams)
    - rigid based systems may be mounted using tape and secured with
    elasticated bandage (Williams).

    2. one may size arrays according to arm size, but most important is
    visibility and calibrating the system to individual joint centres (all..)
    - joint centre locations can be determined during arm swing movements
    - Williams gives some detail of geometry

    3. information potentially lost is particularly in terms of longitudinal
    rotation of segments... if arrays are placed near the proximal limb end,
    they will not measure it, however the greater intermarker distance the
    more one may encounter movement due to being on extreme locations...

    Among the key points raised:
    * Research has been done on marker arrays by Cappozzo et al. (references
    attached) as well as at Oxford University by J. Williams, Alberto
    Leardini and their colleagues.
    * rigid based arrays may not be the best idea (Leardini)
    * technical arrays do allow doing calibration after recording instead of
    before (Williams)
    * scaling arrays for the arm size is good, and may allow better
    visibility of markers
    * a calibration motion (like swinging the arm) can help define joint centres

    Edited original text of the replies sent (by author) follows...
    Thank you all for your assistance!
    Nancy Black __|~_)_I__)_|~_
    Ecole de genie )_ __)_|_)__ __)
    Universite de Moncton | )____) | EMAIL:
    Moncton, New Brunswick \\___|____|____|____// FAX: (506) 858-4082
    E1A 3E9 CANADA \\ // PHONE: (506) 858-4079
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~


    Date: Mon, 7 Jul 1997 10:16:19 +0200
    From: Liduin Meershoek

    I have been using some upper limb markes arrays with VICON. We mounted them
    with velcro strips (upper arm, fore arm) and elastic bandage (hand). The
    elastic bandage was painted black to prevent false reflections. We used
    different arrays for large and small arms to get them better stabilized. The
    placement of your markers will influence the sensitivety to measurement
    errors. The best placement is with equal distances between the markers,
    however this might interfere with the recognition and/or the movements.
    During calibration your define local coordinate systems through bony
    landmarks. The major assumption is that the system (bony landmarks-marker
    array) is rigid. You can calculate the rotation axis from the movements (van
    den Bogert et al. J.Biomech 27:1477-1488) or assume that they are parallel
    with your local coordinate axis. In the latter case you can define a 'zero'
    position with all local coordinate systems parallel and calculate
    Euler-Cardanic rotations to represent flexion/extension, ab/adduction,
    endo/exorotation. This assumes that the rotation axis are mutually
    perpendicular and the sequence will influence your results.
    You should place your forearm array either as distal as possible (we did) or
    as proximal as possible. In this way pro- and suppination will either be
    between the upper and forearm arrays or between the forearm and hand and not
    somewhere in between.
    You will loss information about rigidity of the segment. However using
    individual markers you cannot differentiate between skin displacement and
    nonrigidity so I don't know whether you really loss something.

    Liduin Meershoek
    Vakgroep Functionele Morfologie
    Faculteit Diergeneeskunde
    Universiteit Utrecht
    Yalelaan 1
    3584 CL Utrecht
    the Netherlands
    tel. 030-2534324

    Date: Mon, 7 Jul 1997 10:19:21 GMT0BST
    From: Ingram Murray

    I read your email query to Biomech-L with great interest. I am
    currently in the early stages of a PhD, also looking into motion of
    the upper limb. It would seem that we are both at a similar stage of
    work as I currently am trying to decide upon the best method of
    marker placement and axis definition. I am afraid I haven't yet got
    the knowledge to answer any of your questions, but I am very
    interested in hearing of the replies you receive. I take it from
    your mention of a "calibration" with markers over joints that you are
    using a technique similar to that used by Cappozzo (1991), Cappozzo
    et al (1995) for measuring movement of the lower limb ? I myself was
    considering the use of a modified version of this method for studying
    the upper limb.
    I think it would be interesting to keep in touch as we seem to be
    working in a very similar area. Could you possibly also let me know
    the full title for the paper you cite in your email (Schmidt et al
    (1994)) as I have not read it and can't seem to find it through my
    usual literature search.

    Bye for now.....
    Ingram Murray
    Room M25
    Stephenson Building
    University of Newcastle upon Tyne
    NE1 7RU

    Tel: 0191 222 6193
    Fax: 0191 222 8600
    AND THEN: (after I requested details on the articles Ingram had cited):
    Date: Mon, 7 Jul 1997 15:29:23 GMT0BST
    From: Ingram Murray

    Hi again,
    The references for the two papers I mentioned are:

    Aurelio Cappozzo :- Three-dimensional analysis of human
    walking:Experimental methods and associated artifacts. :- Human
    Movement Science 10 (1991) p 589-602

    A Cappozzo, F Catani, U Della Croce, A leardini:- Position and
    orientation in space of bones during movement: anatomical frame
    definition and determination. :- Clinical Biomechanics Vol.10, No.4
    (1995) pp171-178

    Have got my hands on a copy of the Grenoble Symposium Proceedings.
    The authors do indeed seem to have taken the idea of "calibrating"
    using markers attached for one frame only and then removed, as
    suggested by Cappozzo for the lower limb. I am interested however in
    measuring motion at the shoulder as well as the elbow and wrist so
    would have to take the method a bit further.
    Thanks anyway for the reference.
    Ingram Murray

    Date: Fri, 4 Jul 97 21:46:35 UT
    From: John Williams

    As you will know from Ed. Biden I have done quite a lot of work on upper limb
    markers in Oxford and if you are interested would be happy to send you part of
    my DM thesis which is relevant to your work. You might perhaps talk to Ed as
    well! Please contact me directly if you want this info.

    John Williams MA DM FRCS(Orth)
    9, Dobson Close,
    Hall Lane,
    Appley Bridge,
    WN6 9ES

    Tel: 01257 256379 (Home)
    Tel: 01257 252211 (Work)
    Date: Tue, 8 Jul 1997 14:20:51 -0300 (ADT)
    From: Nancy Black
    To: John Williams

    I have read a copy of your DM thesis, and have thus far based my marker
    placement (individual markers) on those you suggested, given your
    extensive checks on skin movement etc. However: since for my ADL
    activities, the medial epicondyle of the humerus is very
    rarely visible, I thought about using the lateral epicondyle which is
    consistently visible, but upon further checking, is almost colinear with
    the origin of the brachioradialis and the insertion of the deltoid markers.
    Hence one of the reasons I thought about considering technical arrays.
    The other reason was / is your suggestion that likely such arrays may be
    more exact than individually mounted markers. This is particularly
    interesting and important to me since I am not an orthopaedic surgeon and
    likely have a relatively large error in placement associated with each
    marker as a result.
    Unfortunately, I have not yet been able to find a full definition of what
    one is looking for in a technical array. Ex. Should markers be placed
    consistently as much as possible between subjects (ie. mounting markers
    onto a sleeve which is already on the subject, trying to place markers
    relative to bony landmarks (or other landmarks) .. .or should markers be
    permenantly anchored on the sleeve,... or does it make a difference? I'm
    assuming that indeed a calibration of the technical array must precede
    recording sessions... I have a copy of the abstract of your poster from
    CORS in Quebec City, 1996, but this doesn't give me much information. to
    go on (A. Leardini suggested it...). Are there other documents I should be
    consulting? I recently
    ordered a copy of Cappozzo et al. (1995 - Clinical Biomechanics), but it
    will take a while for it to reach me here...
    ---------- his reply:
    Date: Wed, 9 Jul 97 21:47:09 UT
    From: John Williams

    With regard to technical markers the nice thing about them is that the
    calibration is done at the end so you can play around with the position of
    them until you get good visualisation of the markers in the array, then
    collect your data and then dot he calibration. Make the technical markers
    with four markers on the array and make sure that it has a unique pattern i.e.
    it is not a mirror image about one axis. Make then not too big or else they
    wobble and not too small or else the markers merge. The ones I played with in
    Oxford were about 3cm off the base plate and about 5-8 cm in span. (ask
    Alberto or one of the Oxford people to measure them as they are still in the
    lab somewhere -Danielle used them last). I attached then to people with a
    combination of double sided tape on the 4x3 cm bases and a circumferential
    band of elasticated bandage (approx 8cm wide).

    I suggest you contact Alberto Leardini about his/Bologna's CAST routine for
    further details.

    From: Nancy Black
    Sent: 09 July 1997 23:06

    What I had been considering were basically
    arrays against the skin (rather than at a distance away from the
    segment). Ed (Biden) is encouraging me to instead move
    one of my upper limb markers to say the body of the biceps muscle (to
    make the 3 non-colinear). We will see the results of that and then I'll
    make a final decision.
    --------- his reply:
    Date: Fri, 11 Jul 97 01:33:08 UT
    From: John Williams

    I would be wary of placing markers on muscles that may change shape and size
    during motion.


    Date: Tue, 8 Jul 1997 07:19:03 -0300 (ADT)
    From: "Movement Analysis Lab."

    I've been doing some work in Oxford in order to apply the 'anatomical
    landmark calibration' technique (first introduced for lower limb: Cappozzo
    et al. Clin Biomech 1995) to the kinematics of the upper limb. We designed
    and manufactered technical arrays in order to be able to collect upper limb
    segment positions during several reaching tasks. It would not difficult for
    you to find the abstract of the preliminary results presented at the last
    year Canadian Orthopaedic Research Society (Quebec, May 1996).
    Good luck
    Alberto Leardini

    Movement Analysis Lab.
    Department of Orthopaedic Surgery - Istituto Ortopedico Rizzoli
    Via Di Barbiano, 1/10 40136 Bologna, ITALY
    tel: ++39 51 6366520 (secretary)
    ++39 51 6366571 (direct)
    fax: ++39 51 583789
    > I had seen the abstract form the CORS meeting in Quebec 1996, but what I
    > have is simply a 1 paragraph summary (Poster #71, isn't it, p. 61 of the
    > ringed document...? it was a photocopy from a colleague, so I can't be
    > sure this was the proceedings as such). If you have a more detailed
    > description of the array you manufacture, I would be most interested in
    > receiving it. I wonder if it would be appropriate for activities of
    > daily living where the forearms tend to be rotated toward the centre of
    > the body, as well as for reaching activities?
    > Since posting my message to biomch-l I have ordered a copy of Cappozzo et
    > al.'s Clinical Biomechanics 1995 article.
    > Thank you again for your response, and your assistance.
    > Nancy
    Date: Wed, 9 Jul 1997 05:34:33 -0300 (ADT)
    From: "Movement Analysis Lab."

    yes, the arrays were designed to be seen during many actvities: reaching
    objects above or in front the subject, touching the head or the back, etc.
    Anyway, we just pointed out that 'technical' arrays instead of direct
    landmark location of the markers would allow for a better visibility of the
    markers, particularly in large range of motion such those necessary for the
    upper limb. At that time we manufactered rigid arrays (constant distances
    between markers). Now I would be more for deformable arrayes, as those
    obtained just stucking markers on the skin, of course in positions suitable
    to be seen in every body segment position during the activity under
    analysis. So that the only criteria of the design would be marker visibility
    and easy-to-track. I would suggest to define your own arrays according to that.
    No much more of that was included in the abstract.
    Please do not hesitate to contact me for further suggestions.
    Alberto Leardini

    Date: Wed, 09 Jul 1997 08:46:05 +1000
    From: Richard Smith

    I think the main question you have to answer is "What do you want to
    measure with the markers?". I you place an array on the limb (either
    forearm or upper arm) using a base it will move with the "average" skin
    surface at that point, probably in the middle because the array must not
    interfere with joint movement. If you look at the skin movement at this
    point during rotation about a longitudinal axis you will see that it moves
    only about half the distance that the humerus moves (as indicated by
    rotation at the elbow joint). My solution (for the upper arm) has been to
    use a shoulder marker and two markers on the lateral and medial
    epicondyles. This is not perfect by any means but I think it is more
    representative of upper arm movement than an array in the middle of the
    arm. For the forearm the same: two markers at the wrist joint.
    To define the axes you could video a "neutral" position and make all your
    angles relative to that position. Place the limb in the anatomical position
    relative to the lab axes, video a few frames, track and calculate the
    rotations required to bring a temporary segment axis system to being
    parallel with the lab axes. This transformation can then be used to
    calculate a segment fixed axis system. The two segment fixed systems can
    then be used to calculate the relative angle between the two segments. If
    you only want relative angles then you don't have to worry about joint
    centres and translations.
    If you have only three cameras and you are doing extreme rotations you may
    have to resort to your own suggestion to avoid to many lost markers.
    Good luck,



    Date: Wed, 9 Jul 1997 13:19:38 -0300 (ADT)
    From: "Ed Biden (BioMed)"

    Before the issue of technical markers goes too far, I have a real problem
    with them in terms of begin able to use them for routine clinical
    assessments. Having a technical array generally means a fairly bulky and
    to some extent, "in the way" arrangement which can be a problem especially
    with smaller children, or others who are readily distractable. I
    personally view a technical array as a poor second choice if there is any
    sensible way to do the tests with anatomical markers.


    And on a related note:
    Date: Sun, 13 Jul 1997 21:52:51 +0200
    From: (Carolyn Anglin) Eric Nodwell
    To: 'Nancy Black'

    One of the most difficult problems with markers on the arm is simply being
    able to see them in at least 2 cameras at all times. I would therefore
    check this out before you finalise anything.

    I'm very attracted to technical arrays since it's somewhat of a pain to attach
    individual markers. However, I can foresee two problems: for the sake of
    accuracy you want the markers to be widely spaced, but that may make it more
    difficult to attach or to hold steady. The main goal, whether you're you're
    using individual markers or technical arrays is to relate the markers to
    joint centres. Van der Helm et al. (several papers) suggest relating the
    markers to known bony landmarks such that data from different centres can
    be easily compared and swapped. You also have to decide ahead of time
    whether you care about scapular movement. Some programs don