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2-D Video Gait Analysis Protocol

Discussion in 'Biomechanics, Sports and Foot orthoses' started by drdebrule, Dec 11, 2006.

  1. drdebrule

    drdebrule Active Member

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    I am a podiatrist considering purchasing a multi-camera set up with 2-D gait analysis software ( Simi Zflo motion, Dartfish etc) to improve clinical outcomes for patients (not research). What kinematic data, angles or events should a podiatrist measure (capture) for analysis and how does this change your orthotic prescriptions? If you have an established protocol for this type of analysis, I would greatly apprectiate your advice. :)


    Michael B. DeBrule, DPM
    Marshall, MN 56258
  2. Craig Payne

    Craig Payne Moderator

    Michael - Welcome to Podiatry Arena.

    This is a problem a lot of us are wrestling with. What angle(s) do we need to know that will actualy alter the treatment (presumably an orthotic) provided. I commented on some of this in this thread: Digital video and pressure mapping in Private Practice. Even knowing the "pronation angle" is not an issue, as altering rearfoot motion with a foot orthoses is not assciated with outcomes (see Foot orthoses outcomes and kinematic changes )

    The two things I do with a digital video is observe the Bojsen-Mollor axis transfer, as the lack of it does alter the way I cast for foot orthoses (see Bojsen-Mollor high gear/low gear ) and observe for symmetry of heel lift timing as that can alters the choice of materials under the heel (see Asymmetrical density heel raises)
  3. Admin2

    Admin2 Administrator Staff Member

  4. Michael:

    Before one considers using video in their practice, one should first ask the following questions:

    1. What is the goal of using video? Is it for marketing purposes and "quick" analyses or are you actually going to want to take the time to try and analyze the information with a software program or some other analytical method so that this information will change your orthosis prescription/treatment?

    2. What is the amount you are willing to spend on a system?

    3. Will the video analysis be performed on a treadmill or overground?

    4. Will you be wanting to purchase software that is linked to the video camera?

    5. How much are you going to charge the patient for different types of video analysis?

    6. Will you need to hire extra staff for the extra work and extra patient setup time created by doing video analysis?

    7. Will the amount you are charging for the video analysis pay for the extra staffing that video analysis will probably require in your office?

    8. What are you going to tell your patient when their symptoms have improved with foot orthoses but their kinematics that you analyzed before and after receiving their orthoses have not changed? In other words, maybe you should be investing in a pressure mat/pressure insole system to measure the kinetics of gait instead of or in addition to the video analysis you are considering.

    As for me, I utilized slow motion video analysis (in black and white) quite a bit during my biomechanics fellowship at CCPM to teach students, but have rarely used it since. Video analysis just doesn't make sense in my busy practice, with the current office space I have, since I think that my eyes still work pretty well in being able to see many things that may or may not be visible using 2D video analysis. In other words, video analysis would probably slow me down, make me need to hire another staff person, and require that I move to another, larger office. In addition, I would probably only occasionally change my orthosis prescription because of video analysis. However, I can imagine that in many communities and in many practices and for many podiatrists, video analysis could be a big practice builder, could add interest to the practice, and better yet, could allow the podiatrist to make better decisions in treating their patients with foot orthoses or other types of therapy.
    Last edited: Dec 13, 2006
  5. Blo

    Blo Member


    I am one of the software engineers for Contemplas – your post highlights one of the reasons why we developed our dedicated gait analysis software "TEMPLO". Unlike other motion analysis products it offers a real, pre-defined gait analysis protocol, developed by podiatrists, physicians and sports scientists. You can also setup your own protocol or modifiy a pre-defined one, save it and reuse it in every day business.
    This concept makes you much faster and produces more reliable results because the software helps doing the same procedure with each patient.

    The system also integrates the most common pressure distribution measurement systems.
    Have a look at CONTEMPLAS motion analysis (www.contemplas.com) or send a PM if you need further information.

    Contemplas GmbH, Germany
    Last edited: Dec 13, 2006
  6. Blo

    Blo Member

    Kevin, video analysis does not replace your eyes. But the most important point is that the customers/patients are not able to do the same. Video analysis helps providing information to the customers and "proving" the things you want to tell them.
    So video analysis improves your technical results (perhaps just a little bit) but it also has commercial relevance.


  7. drdebrule

    drdebrule Active Member

    Thank you all for your responses. Professor Kirby makes some interesting points from a practice management perspective. Craig Payne also makes good points about low gear high gear toe off and heel timining.

    I understand 2-D video may confirm for your patient things that can already can be seen with your own eyes: lateral trunk bend, abductory twist, limb length check (head tilt, shoulder drop, arm swing, pelic tilt), hip circumduction, upper body sway, dropfoot, severe lack of knee extension etc.

    Off the top of my head I would guess the key angle (events) in 2-D video are follows:
    ankle at contact, hindfoot during loading, knee (contact, late stance, swing flexion), ankle plantarflexion during pushoff, hip extenstion at end of single support, time to heel off (lift), low/high gear or vertical toe off strategy, timing and amount of great toe dorsiflexion. flexion of torso, arm swing, stride length... Again the real question is how will these measurements and observations change your prescription for foot orthotics? What will you learn that you don't already know from an F-scan or similar pressure analaysis system?

    I invite more people to respond to this thread like Craig Payne. Please demonstrate or argue how 2-D video has changed your prescriptions and improved clinical outcomes.

    Thank you all very much for your thoughful responses,

  8. David Smith

    David Smith Well-Known Member

    Dear Mike

    I can see that 2D video would be a useful tool for reviewing a subject's gait in many situations eg reviewing to aid prescription, reviewing with other health proffesionals, sending reports, discussing certain point about the gait with the patient/customer and as a before and after reference. This may very useful for rehabilitation therapy where the patient and clinician can monitor and review progress. I can also see the usefulness in sports applications where the sportsman needs to see how he is moving in relation to how he is actually moving and so modify. However using the video to make quantitative measurements is wrong! When viewing a patient's gait in real life you can view in 3D, move around the patient and make educated, experienced and intuitive evaluations, which do not rely on exact measurements. Lets call this is a kind of fuzzy logic, whereas when you start being precise and logical about your quantitative data then you are, I would think, intending to make precise analysis and logical conclusions. This is where you will be open to all kinds of misinterpretation of data. Even if you can reproduce and repeat the mesurements and show statistical confidence it is likely that the results will still be wrong. Precisely and accurately measuring a certain action recorded on 2D video to produce a data set does not mean the data set is a reliable characterisation of the true action it is just a reliable characterisation of the recorded image.
    When biomechanists started analysing film data they quickly realised the they could not reliably characterise the gait in a simple way. They developed rigorous protocol to locate, coordinate and define the relative positions of axex sets during gait, they devepoped rigorous protocol to mark the joint and limb in certain ways so as to be able to identify the position of each axis set of interest and then use complicated mathematics to analyse the data sets, which took hundreds of hours to produce manually. The very same thing is now done using video and computers but the time taken to produce a data set is only a few minutes. Even so it can take many hours to analyse the data to produce meaningful and useful conclusions. Why would this be done if it were easy to just measure some yellow lines drawn on a 2D video image.

    Look at Blo's atavar, can you tell how much inversion there is in the STJ and how would this affect the measurement of the ankle dorsiflexion when using the lateral border as a reference, what if the knee was internally rotated also?

    Sounds simple enough, saggital plane view of hip extension. Relative to what?
    The ground, the pelvis? ok the pelvis, but how will you define where the pelvis is in space, is it tilted rotated flexed, if any of these occur how will it effect the measurement of hip extension. How will you identify the position of the hip joint in the first place.
    You could make relative qualitative conclusions about hip extension, say before and after intervention, and this may be useful.

    Step length, that sounds like an easy one. But where do you place the camera not for a frontal view obviously, so a saggital view sounds right yes?
    Very nice if the person walks in a perfect saggital plane. But with this patient while the right leg swings thru quite normally the left abducts considerably and the foot toes out. So what is the step length? is it the oblique distance between the feet or is it the horizontal distance between the feet as seen by the camera.
    I believe that due to its relative inexpensiveness this technology is being used out of context and promoted for the wrong purpose.

    Cheers Dave Smith

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