DEVELOPING DIVERSITY IN MOTION ANALYSIS STUDIES

by Ed Biden, Vicky Chester, Bernard Hudgins, Wayne Albert and Jeremy Rickards,
University of New Brunswick, Canada

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Exterior of the Institute of Biomedical Engineering

The University of New Brunswick has had a more than forty-year history of activity in Biomedical Engineering beginning in the early 1960s when Robert N. Scott, a Professor in Electrical Engineering, began experiments in measurements of myo-electric signals with the purpose of developing alternative control systems for prosthetic limbs. In 2002 Dr. Scott, then Professor Emeritus, opened "R.N. Scott Hall" to house the Institute of Biomedical Engineering. The unit now includes a Vicon 512 motion analysis system as well as biological signals research, an upper limb prosthetics facility drawing amputees from across the four Atlantic Provinces of New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador, and an active group of staff, faculty and students.

The UNB lab team: Jeremy Rickards (seated) and standing left to right Usha Kuruganti, John Hayden, Yves Losier, Wayne Albert, Vicky Chester, Ed Biden, Martha Ross, Danny Lynch, Jennifer Pick

When it was founded formally in 1965 as the Bioengineering Institute, the primary interests were in the development of controls for powered upper limb prostheses. The expertise in myo-electric controls developed rapidly and UNB became, and still is, an internationally recognised centre for research in this area. Through the 1970s interests expanded to include hospital electrical safety, but the primary focus remained firmly in electrical engineering. The interests of the Institute broadened through the 1980s and 1990s to include biomechanics and ergonomics as the faculty group expanded from a small core of electrical engineers to one of the most broadly based groups at the University. Currently collaborators come from Engineering, Science, Arts, Forestry and Environmental Management and Kinesiology.
Motion analysis at UNB has been active, primarily in teaching, through the faculty of kinesiology since the 1970s using cine film for motion capture and a force platform. Mechanical Engineering had begun developing simple video-based two-dimensional motion analysis when a generous grant from the Ronald McDonald Children's Charities changed the direction in 1995 by supporting the purchase of a Vicon 140. This system with its three cameras, data station, and laptop computer formed the foundation for the current motion analysis activities. This portable system was used to study hypotonic children at the Stan Cassidy Centre for Rehabilitation (New Brunswick's Tertiary Rehabilitation Centre). It was also used to study joystick use by heavy equipment operators in simulated cab environments set up in an old soil mechanics laboratory of the Faculty of Forestry. Ergonomic studies of upper limb motions in normal limbed and upper limb prosthesis users were also investigated in this lab.
During this period the Institute was divided with the research activities concentrated on the UNB campus in a building built in 1900, and the clinical prosthetics group across town at the Stan Cassidy Centre. Neither site had space for a motion lab, and the soil mechanics lab once more became home for motion analysis activities.
In 2000 the Canada Foundation for Innovation funded, in partnership with the Atlantic Canada Opportunities Agency and the Provincial Government in New Brunswick, the purchase of the current Vicon 512 system. The funding was linked to building a substantial expansion to the on-campus site that would allow consolidation of all the aspects of the Institute, including a new motion analysis laboratory, under one roof.
During the planning and construction phase the Vicon 512 was installed in the soil mechanics laboratory. More linkages with the Stan Cassidy Centre for Rehabilitation led to an ongoing program studying gait in hypotonic children to assess the efficacy of orthotic treatments for children at an early stage in development. Links with the orthopaedics department of the Dr. Everett Chalmers Hospital, generated studies of total knee replacements and a growing interest in assessment of upper limb proprioception using dynamic tests.

Lab set up for comparison of Vicon with other measurement systems

R.N. Scott Hall was opened in the spring of 2002 while the last phases of construction were still underway. The new motion analysis laboratory opened at the same time with progressive phases completing the installation of the motion system, force platforms, etc..
A unique aspect of the laboratory is the range of use that it receives and the number of setups that are required for the research projects. This diversity of use is supported by a very strong technical team within the Institute as well as through the work of well-motivated graduate students and faculty.
Experimental work currently underway includes upper extremity analyses, lower extremity analyses and whole body experiments. Upper limb projects include ergonomic assessments of the postures and motions involved in using computer pointing devices. A graduate student in the Faculty of Kinesiology has recently invented a new computer input device, which is at the patent pending stage. The uniqueness of the device is that it places the upper limb and hand in a very natural and non-stressing posture. The Vicon system is being used to quantify the degree of motion, time spent in less than ideal postures and the time spent holding a static posture while performing functional computer tests. The markers placed on the hand, forearm, upper arm, shoulder and head will provide the necessary upper body kinematics necessary to determine the ergonomic concerns associated with each input device.
A very interesting application underway in conjunction with the Orthopaedics Department of the local regional hospital is the assessment of proprioception using dynamic rather than static tasks. Typical assessments of proprioception involve positioning a limb and then either applying a small motion and assessing the person's ability to detect movement, or moving the limb passively and having the subject being tested indicate when some previous position has been achieved. The use of the Vicon 512 enables tests where a person can perform a pointing or tracking task with markers applied and then retest with the subject blindfolded while the motions are replicated. Tracking the markers in 3D provides a measure of how close the person is to the previous track or location without providing any sensory clues. We are using this technique to examine shoulder proprioception in individuals with and without shoulder injury, and will eventually use it to document changes after shoulder repair.
Lower extremity projects include a continuing study of children with low tone conditions. New Brunswick has a relatively large concentration of children with such conditions, many of whom receive regular physiotherapy and orthotic treatment at the Stan Cassidy Centre for Rehabilitation. Joint research between the Rehab Centre and the Institute of Biomedical Engineering is assessing the walking patterns of these children with and without orthotic treatment. Quite aggressive orthotic treatment is used for children with low tone conditions with the objective of having them meet motor control milestones on a timeline similar to children without this sort of problem. The project, now running for several years, assesses children prior to orthotic use and then tracks their changes with and without their braces. So far, results have shown support for the Stan Cassidy therapeutic approach. This year, a new study will examine the effectiveness of serial casting techniques in children with spastic cerebral palsy. Of interest is whether range of motion increases in the ankle after the first series of casts, and if so, how long does this benefit remain? Most patients demonstrated improved sagittal ankle joint angles and moments when walking with braces versus without. The stability provided by the brace not only improved the motion of the foot, but also had dramatic changes in more proximal segments such as the thigh and pelvis in some children. These initial findings lend support to SCCR's treatment of hypotonic gait.
Working with the Orthopaedics Department we are assessing a technique to measure motion of total knee replacement components using surface markers. Initial work demonstrated the ability to reproduce measurements made using radiography. The current project is comparing a group of people with total knee replacements against an age-matched control population to assess systematic difference between the two groups. We have observed the total knee-replaced group to be very consistent in the angles measured using the Vicon system. Verification of measurements using radiographs suggest that Vicon measures were accurate to within 3 to 6 degrees. Substantial antero-posterior motion was observed in the implants that sacrificed the cruciate ligaments now being compared to people with normal knees.

Full body model in ergonomic assessment of repetitive lifting

Tracking a lifting task

Recent collaborations with the Faculty of Kinesiology have included whole body assessment of lifting tasks. The complexities of industrial lifting and manual material handling poses great challenges for 3D motion capture. One challenge is that camera setup needs to accommodate the large performance volume. Some tasks require that a box be lifted from the floor and then placed on a shoulder height shelf located at a 135 degree turn to the lifting position. Secondly, creativity is required in recreating industrial tasks as conveyor belts and shelving units occlude the camera views. To combat this, thin black wire has been strung across the lifting space to simulate shelving units, thereby being unobtrusive to the opto-electric cameras. Currently a research team in the Faculty of Kinesiology is conducting a comparison of 3D kinematic and kinetic models using Vicon, an electromagnetic motion tracking system and video capturing techniques. The Vicon system is being used as the 'gold standard' to validate models developed in the other motion tracking methods. Ergonomic practitioners performing work assessments need to use video based analysis, which is a legitimate tool when developed using robust modelling from systems such as the Vicon 512.
One very substantial challenge for our laboratory is the problem of being able to reposition cameras depending on the studies to be performed. The applications described above range from those where the active volume is the size of a desktop, to multi-metre dimensions for walking or ergonomic evaluations. A promising technique to allow quick repositioning of cameras is to record the relative locations of either the L-frame calibration object or some other array of markers in each camera view. This is done by placing a transparent sheet of film over the computer screen while the "live monitor" function is active, and marking the locations of the markers on the L-frame or of markers on some other object once the cameras have been set up in an acceptable position. Relocation later with reasonable accuracy can be achieved by putting the marked transparent film back on the screen while the "live monitor" is active and the L frame or other object is repositioned in its original orientation. The camera is adjusted until the points match the marked points recorded earlier. This method also allows the camera arrangement to be moved within the room while maintaining the same relative locations of the cameras by simply placing the L-frame or other calibration object in a different position. Detailed tests of this technique are underway to establish how accurately cameras may be relocated.
Vicon provides a strong base for biomechanics research within our Institute. We look forward to coming upgrades to our system to make it even more functional, and to the growing applications of the system by users throughout the University.