The effect of a prototype feedback and passive spinal support device on spinal loading during load handling tasks in healthy subjects and low back pain patients.

Low-back pain (LBP) is often termed a pandemic of the modern world and
represents a large socioeconomic burden. Epidemiological studies have shown
that physically demanding jobs correlate with prevalence of LBP and
exaggeration of symptoms. One way to target this problem is to develop
technologies that either augment or substitute human physical abilities and
prevent negative effects on the human body. Most of the assistive devices that
have been developed so far mainly focus on augmenting the motion of the arms.
Recently these devices have been extended to the trunk. Several studies have
found that wearing assistive devices that passively support the users* trunk
movements reduces spinal loading during lifting, bending and static holding
tasks. However, the actual effect on spine loading has not yet been assessed.
Moreover, most devices have not been tested beyond the laboratory, and there
are still some concerns regarding discomfort, practicality and usability. In
addition, the potential of integrated real-time feedback on spine motion and
spine loading has not been explored and systems have not yet been tested for
effectiveness in low back pain patients.

The objective of this project is to design and test a novel assistive device to
ultimately prevent low-back pain in able-bodied workers and to support workers
with low-back pain who are re-integrating in the vocational setting. In this
project, two different assistive devices will be evaluated: 1) a feedback
system based on force sensors and an inertial motion capture system providing
feedback about physical risk factors measured in real-time 2) a passive
exoskeleton that is able to support the weight of the trunk and prevent awkward
trunk postures. In doing so, the effects of the system on spinal loading are
evaluated in terms of L5S1 spinal compression forces, lumbar angles and
accelerations, and co-contraction. Furthermore the effects of wearing the
device on work performance (effort, productivity and comfort) and daily
activity performance (5 common daily tasks) will be investigated. Finally,
feasibility of using the system, and satisfaction in using the system will be
analysed in the working environment of the subjects.
*

This cross-sectional study will be divided into three parts. Part I will test
the effectiveness in terms of in limiting spinal movement and load of the
lumbar spine of the device in healthy people only. These experiments will be
performed in a mock-up laboratory setting at the Vrije Universiteit Amsterdam
over a period of 18 months.
It is expected, that part I will show that the device never increases but only
reduces spine motion and spine loading without substantial negative side
effects. If this holds true, the device is safe to be tested with people who
suffer from recurrent low back pain. Then, a second assessment of the device
will be conducted at the Vrije Universiteit Amsterdam, including employees who
suffer from recurrent low back pain (Part II).
In part III, feasibility and satisfaction of using the device will be assessed.
These tests will be performed in the working environment of the subjects, hence
on site (various work locations).

Parts I and II: Laboratory testing
The effectiveness of spinal load reduction, the work performance and the daily
activity performance when wearing the assistive device will be tested in a
mock-up laboratory setting.

Measurements will be taken in two sessions. In the first session, a
classification of the subjects will be conducted. Participants will fill in the
Work Productivity and Activity Impairment Questionnaire, The Owestry Disability
Index and the RAND-36 Questionnaire. Furthermore, a first familiarisation of
wearing the assistive device will be given and a pain rating during the
familiarisation will be filled in by the subjects to adjust the device and by
that ensuring good comfort in the following session.

In the second session subjects will perform a task cycle with a number of
sequenced load handling tasks. In order to arrive at a variety of tasks and to
guarantee intrinsically safe load handling, we will base our task selection on
the revised NIOSH lifting equation which was developed to determine a
recommended weight limit for a specific task. A number of 30 different tasks
will be used to simulate lifting and lowering tasks and 10 different tasks will
be used to simulate pulling, pushing and carrying tasks. Subjects will perform
the task cycle without and with wearing the SPEXOR device. To assess
effectiveness of the assistive device spinal movement and load will be
determined using measured forces in the shoes and by measuring body kinematics
with Xsens sensors, i.e. matchbox-size inertial sensor units, attached with
rubber bands to body segments. Forces will be measured by force platforms and
body kinematics and kinetics by using an optical motion capture system
(Optotrak). Additionally, EMG activity of the main trunk muscles (Erector
Spinae, Multifidus, Rectus Abdominus and External Obliques) will be recorded,
placing electrodes on the respective muscles based on SENIAM recommendations.

In order to assess work performance, heart rate will be recorded over the whole
task cycle and the subject will be asked for rating of perceived exertion,
using the Borg Rating of Perceived Exertion (RPE) and perceived local
discomfort, using the Local Perceived Discomfort Scale (LPD). Furthermore, the
time to complete the whole task cycle will be measured to assess a change in
productivity due to the device.
Daily activity performance will be analysed by including 5 common daily tasks.

1) Self-Paced Walk Test : time needed to cover a specified distance (sec)
2) Stair Climb Test: time needed to complete the test (sec)
3) Six-Minute Walk Test: travelled distance (m)
4) Sit-To-Stand Test: total number of complete Sit-Stand-Sit cycles in one
minute.
5) Timed Up and Go: time needed to complete the test, consisting of stand up,
walk 5 meters, turn, return to chair, and sit down (sec)

Participants will perform these tasks with and without the assistive device to
monitor whether the device limits performance on these activities.


Part III: Field testing
Feasibility and user satisfaction will be tested at the work site of the
included participants in two sessions. In the first session each participant
will wear the device for a full day while performing normal working activities.
Usability will be assessed with the System Usability Scale (SUS) and the Users*
Impression Questionnaire (see Addendum 1) that will be filled in by the
subjects after the working day.
User satisfaction will be assessed in the second session using the PGIC
questionnaire (Patients* Global Impression Of Change) and semi-structured
interviews based on the ICF (International Classification of Functioning)
framework. Satisfaction of rehabilitation professionals will be assessed using
the CGIC questionnaire (Clinicians* Global Impression of Change).

see study design

Since the SPEXOR exoskeleton will either passively assist or monitor movement
and give feedback in case of unfavourable loading or motion, both systems only
intend to reduce loading on the spine and therefore will not result in
overloading of the spine. In addition all tasks are within the accepted NIOSH
safety limits. When testing, all tasks will be adapted so that individual
limits are not exceeded with or without the device. During measurements,
participants will be instructed that they can, at any time, ask for further
load or motion reductions, or skip parts of the tasks. Hence, the risk
associated with participation is negligible to low. Testing will take only one
day. Both, healthy worker and worker with recurrent low back pain may benefit
from the results of this study in the way that an effective assistive device
can be used to prevent healthy worker from low back pain and to reintegrate
people with recurrnet low back pain in their vocational setting.