No announcement yet.

RE: pelvic orientation

This topic is closed.
  • Filter
  • Time
  • Show
Clear All
new posts

  • RE: pelvic orientation

    Dear Biomch-L readers/posters,

    In reply to Karin Rosenberg's question on pelvic orientation (or attitude, as
    I would prefer to call it) during stance, a very useful source is David H.
    Sutherland, Richard A. Olshen, Edmund N. Biden, and Marilynn P. Wyatt, "The
    Development of Mature Walking", MacKeith Press 1988, Blackwell/Oxford and J.B.
    Lippincott/Philadelphia. One of the authors is a Biomch-L subscriber, and
    the group is with the Children's Hospital in Frost Street, San Diego, Calif-
    ornia. Some time last year, I posted a review of this book to the list (Mike
    Whittle: my apologies -- I cannot seem to come around reviewing your book!).

    Note that their graphs are expressed in terms of so-called `planes of move-
    ment' (pp. 65-66):

    "We have chosen to consider the familiar, laboratory-oriented planes
    of movement used by physicians and physical therapists rather than more
    complex concepts such as *Eulerian movement*[*] which would be familiar
    only to engineers, mathematicians or physicists. A brief review will be
    given for readers who may not be accustomed to the terms. In the context
    of the laboratory, *sagittal* movement is in the direction of walk pro-
    gression and is best viewed from the side; *coronal* movement is from
    side tot side and is best viewed from the front or back; *transverse*
    movement is about a vertical axis and the ideal viewpoint, although im-
    practical, is from above or below the subject."

    "[*] *Eulerian movement* related to the motion of each segment (rigid body)
    to another or multiple other rigid bodies in space" [or to the spatial
    reference coordinate system -- HJW].

    Note that this approach is rather useful if the movement is the classical
    paradigm of level, straight walking along, e.g., the X-axis of a laboratory-
    defined, Cartesian coordinate system, for *segment* movement in particular
    (i.e., segment position and attitude expressed relative to the laboratory
    frame of reference). However, it is less attractive for *for joint movement*
    as defined in this approach (i.e., differences of corresponding segment angles)
    since these so-called `projection angles' will change even for a `fixed' joint
    (unless it is in the neutral attitude, with equal projection angles for the
    proximal and distal segments) if the subject as a whole -- or the laboratory
    reference coordinate system -- changes orientation, e.g., by a rotation about
    the vertical axis. Eulerian angles (or helical ones) do not suffer from this
    disadvantage. Here, the engineers/mathematicians/physicists do have a mis-
    sion, it seems.

    An intermediate solution would be to define `projection plane joint angles'
    as those angles where the attitude of a distal segment is viewed after re-
    aligment of the laboratory reference system with the proximal segment's
    coordinate system. This is, however, an interdisciplinary (`political')
    compromise ...

    Herman J. Woltring, Eindhoven/NL