View Full Version : Summary of marker sets and gait models

07-06-2007, 12:49 AM
Hello Again,

I am encouraged by Dr Greiner's remarks, because in many respects, they reflect the way I've approached human movement biomechanics. My experience in clinical gait analysis suggests to me that there are, in general, two schools of thought: (1) those who believe the value in uniformity outweighs technical limitations of an historic model, and (2) those who believe the potential for increased accuracy in a patient-specific model outweighs the challenges in comparing across patients and facilities.

I have been very much influenced by my career path. When I started in biomechanics, there were no "off-the-shelf" software applications that would perform the necessary analyses. So, I worked to understand from first principles (anatomy, physiology, physics, engineering) how best to model a particular activity, within the technical constraints of the time. It has therefore been a natural step for me to explore new modeling techniques that I believe would benefit the patients referred to my laboratory. This influenced my choice of post-processing software that allowed me the freedom to create my own models, while describing in sufficient detail the calculations performed "behind the scenes."

I have been influenced also by my colleagues who feel comfortable with conventional techniques, and who worry about moving in a new direction. In our laboratory, we diligently compared our new data sets with those from conventional techniques, to understand model-based differences, and submitted these to peer-review before using the new techniques clinically. I feel this was sufficient for our clinical service, independent of whether the rest of the gait analysis community followed our lead.

In my experience, this is where my perspective clashed with some of my colleagues. Where they would argue that the conventional gait model has been validated, I would argue that it has been popular, but not necessarily validated. (Across the literature, and across software, it is not even as uniform as some would think.) Where they would argue that skin movement and palpation errors could be overcome by global optimization techniques, I would argue that this pre-supposes motions that may not truly represent those of a patient, and that generalized six degree-of-freedom techniques were more likely to show patient-specific problems.

While writing this, I just read a post by Mike Schwartz, who has blended conventional and functional modeling techniques, in a very productive clinical and research environment. Gillette's success would also suggest that we need not all perform the exact same analyses to provide a very useful service to our patients.

Please note that these thoughts are my opinions, which may or may not be shared by my employers.

Best regards,

Frank L Buczek Jr, PhD
Branch Chief, HELD/ECTB
National Institute for Occupational
Safety and Health (NIOSH)
1095 Willowdale Road MS 2027
Morgantown, WV 26505
304-285-5966 voice, 304-285-6265 fax