Vertebral Metrics
Application of a Non-invasive System to Analyse Vertebrae Position using Two
Seating Platforms
Ana Teresa Gabriel
1
, Cláudia Quaresma
1
, Mário Forjaz Secca
1,2
and Pedro Vieira
1
1
LIBPhys-UNL, Departamento de Física, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Caparica,
Portugal
2
Ressonância Magnética – Caselas, Lisboa, Portugal
Keywords: Spine, Medical Device, Non-invasive, Vertebrae Position.
Abstract: The study of the biomechanical changes in the spinal column is particularly important in modern society since
they are considered the main responsible for back pain. Vertebral Metrics is an instrument that aims the global
evaluation of the spinal column. Noninvasively and semi-automatically, this image processing based system
allows the identification of X, Y and Z position of each spinal process on standing position. The analysis of
vertebraes position using two different seating platforms through the application of Vertebral Metrics is the
aim of this work. Along the paper the main stages concerning to the study will be described. Nine volunteers
were recruited and an ergonomic chair and a bench were used to perform the study. Results show that
differences in vertebrae position are not relevant when sitting in the ergonomic sit or in the lab. Also, spinal
curvatures as well as lateral deviations of the spine were properly represented from data collected with
Vertebral Metrics. The study proved that Vertebral Metrics has a huge potential to perform the analysis of
the spinal curvatures.
1 INTRODUCTION
Spinal column is an essential component of human
body promoting support and protection functions.
Also, trunk and limbs movements are provided by the
spine (Seeley et al., 2003).
Back pain has long been a relevant problem in
modern society. The number of people affected by
this symptom increases every year (Manek and
MacGregor, 2005). Previous studies pointed out that
50% to 80% of the individuals experience at least one
episode of back pain during their lifetime (Rubin,
2007). From those 80% to 90% are caused by
mechanical spinal disorders (Najm et al., 2003;
Quaresma et al., 2010). Congenital malformations,
sedentary lifestyle, posture and incorrect physical
exercise have a great contribution for the mechanical
disorders (Jordão et al., 2011).
An important tool to identify the spinal problem
and delineate the appropriate methodologies is the
study of the spinal curvatures. Radiological
techniques are the most widely used methods for
assessing the spinal column however they use
ionizing radiation. Thus, these techniques must be
carefully applied (Harlick et al., 2007; Pinel-Giroux
et al., 2006).
Ionizing radiation free devices are needed to
evaluate, in a global way, the spinal column.
Although many non-invasive devices have been
developed to assess the spinal column most of them
does not allow the three-dimensional evaluation of
the spine. In addition, those who allow a 3D analysis
are extremely expensive as the methods that use
infrared cameras (Hinman, 2004).
Vertebral Metrics – National patent PT/103990,
European patent PCT/IB2009/005018 and American
patent US20110004125 - is a non-invasive system
designed to identify the spatial position of the spinal
apophysis from the first cervical to the first sacral
vertebrae in the standing position. Using a fluorescent
marker to identify the skin projection above the spinal
processes, recognition is achieved with software
capable of distinguish the marks (Gabriel et al.,
2015a; Gabriel et al., 2015b). Due to its versatility the
equipment can have several applications from
screening and prevention to monitoring the
intervention methodologies for each clinical case.
Gabriel, A., Quaresma, C., Secca, M. and Vieira, P.
Vertebral Metrics - Application of a Non-invasive System to Analyse Vertebrae Position using Two Seating Platforms.
DOI: 10.5220/0005790202350240
In Proceedings of the 9th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2016) - Volume 1: BIODEVICES, pages 235-240
ISBN: 978-989-758-170-0
Copyright
c
2016 by SCITEPRESS Science and Technology Publications, Lda. All rights reser ved
235
The aim of this paper is to present a study
concerning to the application of Vertebral Metrics in
the sitting position. Sedentary lifestyle is a significant
concern of modern society and seating position is one
of the most adopted positions. In addition, the
majority of the occupational activities are carried out
in that position.
According to studies performed by Chen et al.
(Chen et al., 2006), a significant change in spinal
curvature is found in a sitting position, causing a
forward displacement of the lumbar spine, increased
thoracic kyphosis and a decrease in pelvic angle. It
contributes to a posterior pelvic tilt. They concluded
that the pressure on the intervertebral discs is larger
in this position than in the standing position, which is
explained by the pelvis rotation. This causes a change
in the biomechanics of the spinal column, leading to
a pressure increasing in the lumbar intervertebral
discs. The sitting posture is highly stressful because it
requires large static work of the muscles involved.
During the study nine volunteers were recruited
and vertebrae’s configuration was analysed in the
sitting position using two seating platforms - an
ergonomic seat and a lab seat. The ergonomic seat is
prescribed by physicians as a good posture promoter
in sitting position. Lab seats are widely used however
as they do not have a lumbar support they stimulate
bad postures. The main goal of the study is to quantify
postural differences between the two sitting
platforms.
2 MATERIALS AND METHODS
2.1 Vertebral Metrics
For a better understanding of the object of this study
the considered axis system will be defined as follows:
the transversal distance is X coordinate, the antero-
posterior distance is Y coordinate and the height is the
Z coordinate (Figure 1).
Figure 1: Mechanical apparatus of Vertebral Metrics and
axis system.
Vertebral Metrics system consists of a vertical
positioner – Z positioner - and a horizontal positioner
– X positioner – with a bracket coupled. A stereo
vision system and two ultraviolet lights are fixed on
the bracket in specific positions. A resolution better
than 1 mm in each direction is provided by the stereo
vision system. Therefore two monochromatic video
cameras are fixed side by side in the horizontal
support. The cameras (model UI-3480ML from
IDS™) are 47 mm from each other. They have
2560x1920 pixels resolution and a lens with 12 mm
of focal distance (Optica Goyo from IDS™).
Hardware is controlled by software that was specially
developed for that purpose. Communication
functions as well as the user interface were defined in
Visual Studio™ (Gabriel, 2015b).
A fluorescent marker is used to identify the spinal
processes above the skin. When excited by ultraviolet
light this dye emits a well-known wavelength – 635
whereas the ultraviolet light emits at 400 nm. Image
processing algorithms were implemented in Matlab™
to recognize the fluorescent marker and determine the
spatial coordinates of each point. To simplify the
definition of the image processing algorithms an
optical filter (BP635 from MedOpt™) was coupled to
each camera. The optical filters selectively transmit
light in a particular range of wavelengths - from 600
nm to 700 nm - while blocking the remainder.
Therefore the fluorescent marks stand out in the
pictures acquired by the cameras which allowed the
definition of less demanding image processing
algorithms (Gabriel, 2015b).
In the beginning of each scan, the mechanical
structure must be positioned under the point that
identifies the first sacral vertebrae. This step is
performed by a physician using the user interface.
When the previous condition is accomplished the
physician should press the Start Button to initialize
data collection. Thereby an automatic cyclical
process is carried out by software. During that process
a pair of images is acquired simultaneously by the
cameras and then the mechanical structure moves
upwards. After 50 mm the equipment stops and
another pair of images is acquired by the cameras.
Sequential images are recorded in a folder to be
posteriorly analysed by image processing algorithms.
The algorithms will identify the fluorescent marks
and determine its tridimensional coordinates. It is
noteworthy that data acquisition is completed in such
a short period of time – between 30 and 40 seconds -
because image processing is performed after a
complete full scan of the spine (Gabriel et al., 2015b).
Data collection with Vertebral Metrics becomes
available a table with the 3D coordinates of each
BIODEVICES 2016 - 9th International Conference on Biomedical Electronics and Devices
236
spinal process as well as a 3D representation of these
points. By definition, first sacral vertebrae is always
considered the reference – its coordinates are (0,0,0)
– and the other vertebraes coordinates represent
relative positions comparing with the reference.
2.2 Application Protocol
The application of Vertebral Metrics to analyse
vertebrae position using two seating platforms is the
main goal of this work. Thus an ergonomic sit and a
lab sit were used consecutively to perform the study
(
Figure 2). Nine volunteers – eight male and one
female - aged between 18 and 27 years old and with
no associated pathology were recruited. Letters from
A to I were used to identify the volunteers.
Procedures, purposes and risks associated with the
study were explained and informed consent was
obtained from each volunteer before participation.
Tests were performed in the Instrumentation for
Medicine Laboratory under a project lead by
FCT/UNL.
Figure 2: Seating platforms: a) ergonomic sit; b) lab sit.
Before data collection, the spinal processes were
identified by the physician. In each individual twenty
spinal processes were identified – from the sixth
cervical vertebrae to the first sacral vertebrae – and
five consecutive scans were performed using the
ergonomic sit followed by five consecutive scans
using the lab sit. The first five cervical vertebraes
were not identified because their skin projection was
covered by hair. The fluorescent marker spreads
when applied above hair. Thus, the marks are not
identified by the image processing algorithms as they
are optimized to recognize circular shapes only. This
problem will be addressed in the future with a better
method to place the markers.
Figure 3 shows volunteer
C during the data acquisition process with both
seating platforms.
It is noteworthy that he number of subjects (nine
volunteers) as well as the number of consecutive
scans (five for each subject in each sitting platform)
was set based on what was considered correct given
the data acquisition time and the reasonable number
of measurements.
Figure 3: Data collection: a) ergonomic sit; b) lab sit.
3 RESULTS
Collected data was carefully analysed in order to
evaluate vertebrae position differences between the
two seating platforms used along the study.
As five scans were performed to each platform,
the first approach included the determination of
means and standard deviations. Spinal processes are
represented by 3 coordinates – X, Y and Z – and we
performed five scans with each seating platform so
mean value and standard deviation were calculated
for each coordinate of each vertebrae. Several
standard deviation values obtained are bigger than
system resolution – 1 mm in each spatial direction. As
the sound of the repositioning movement of the
mechanical apparatus was identified by the
volunteers, postural adjustments performed during
this periods are the main responsible for the
unexpected values. Furthermore, the standard
deviation increases in the upward region which is
explained by the larger spinal mobility in the thoracic
and cervical area. Besides the previous constraints the
3D coordinates obtained in each independent scan of
the spine are not affected by the movement artefacts.
Postural adjustments are insignificant during the 30
seconds required for a complete scan. In these
circumstances, a comparison of vertebrae coordinates
mean values does not make any sense. An alternative
approach involved the analysis of the first scan for
both situations. First scan was chosen because
volunteers were extremely focused in stay perfectly
still in the begging of each test. Nevertheless any
other scan could have been analysed. Spinal process
position observed from the coronal and sagittal planes
are shown in Figure 4 and Figure 5, respectively.
Vertebral Metrics - Application of a Non-invasive System to Analyse Vertebrae Position using Two Seating Platforms
237
Figure 4: Vertebrae position observed from the coronal
plane: a) volunteer A; b) volunteer B; c) volunteer C; d)
volunteer D; e) volunteer E; f) volunteer F; g) volunteer G;
h) volunteer H; i) volunteer I.
Spinal curvatures information is not
comprehensive by observing vertebrae position from
the coronal plane – x0z. Nevertheless this view is
useful to analyse lateral deviations of the spine.
Although Figure 4 b, c, d, e, f and g present an
identical shape regarding to lateral deviations
between both seating platforms, there is no link on
Figure 5: Vertebrae position observed from the sagittal
plane: a) volunteer A; b) volunteer B; c) volunteer C; d)
volunteer D; e) volunteer E; f) volunteer F; g) volunteer G;
h) volunteer H; i) volunteer I.
which platform contributes to a bigger deviation.
Lateral deviation differences as well as the absence of
a standard may be explained by movement artefacts.
Changing the seat implies up and sit down which
leads to postural changes.
BIODEVICES 2016 - 9th International Conference on Biomedical Electronics and Devices
238
Figure 5 allows the analysis of spinal curvatures
by observing vertebrae position form the sagittal
plane – y0z. Similar to what was found in the analysis
of lateral deviations there is no standard on the
results. Once again movement artefacts have
contributed to the unexpected results. However spinal
curvatures have an identical shape in both cases.
At last another type of analysis was performed. To
the X and Y coordinates separately, distances between
vertebrae position in lab seat and the ergonomic seat
were calculated. In Figure 6 a scheme of the referred
distance in X direction just to one vertebrae is
presented in order to understand which distance - ∆
- we are determining. The same method was used to
calculate distances in Y direction.
Figure 6: Scheme of the calculated distance in X direction.
Mean and standard deviation were determined for
the X and Y coordinate each vertebrae considering the
five acquisitions performed with both seats in each
volunteer. Moreover mean and standard deviation
were determined for each vertebrae considering all
the acquisition performed in all volunteers. Table 1
presents the results obtained for the second condition.
In both cases mean values are smaller than the
deviation so it is not possible to conclude the
adjustment carried out by each seating platform.
By observing the aforementioned table it is found
that
|
∆
|
increases along the spinal column, namely
from S1 until C6 vertebraes. As ∆ represents the
difference between the lab seat and ergonomic seat
(

−

), negative values indicate
that, in general, the lateral deviation of the spine is
greater to the ergonomic chair. The same correlation
is identified to the standard deviation. High values of
this parameters are explained by interpersonal
differences. Regarding to the Y coordinate, there is no
standard in ∆ and it was found an increase in the
standard deviation. Again this is explained by
interpersonal differences.
Table 1: Mean and standard deviation of distance between
X vertebrae position in the lab sit and the ergonomic sit and
distance between Y vertebrae position in the lab sit and the
ergonomic sit for all acquisitions in all volunteers.
∆
(mm)
(mm)
∆
(mm)
∆
(mm)
S1
0.00 0.00 0.00 0.00
L5
-0.35 0.79 -1.44 2.84
L4
-0.48 1.45 -2.07 3.81
L3
-0.54 2.47 -3.07 5.62
L2
-0.82 3.17 -3.12 6.93
L1
-1.09 3.88 -1.78 8.31
T12
-1.48 4.61 -0.96 9.44
T11
-1.83 5.37 -0.03 9.73
T10
-1.82 5.89 0.40 11.18
T9
-2.25 6.65 2.37 12.62
T8
-2.49 7.30 3.22 13.20
T7
-2.75 7.77 4.20 14.73
T6
-3.06 8.05 5.41 15.80
T5
-3.10 8.16 5.49 17.29
T4
-3.40 9.12 3.57 15.93
T3
-3.40 9.80 6.76 20.45
T2
-4.38 10.46 -0.64 22.17
T1
-4.91 11.06 6.85 21.95
C7
-5.81 11.64 5.73 22.30
C6
-6.28 12.10 6.73 23.33
4 CONCLUSIONS
Vertebral Metrics is a non-invasive equipment
developed by our research group. It was primarily
designed to identify the spatial position of the spinal
processes from the first cervical to the first sacral
vertebrae in the standing position.
Present another application of the equipment - the
analysis of vertebrae position using two seating
platforms - is the object of this study. Nine volunteers
were recruited and five acquisitions with the
ergonomic sit followed by five acquisitions using the
lab sit were performed. Collected data was carefully
analysed and results show that there are no significant
differences in vertebrae position when sitting on the
ergonomic sit or in the lab sit. Also a standard was not
found regarding to the use of the two platforms.
Postural adjustments when the seat was changed
contributed to the lack of uniformity.
A complete scan of the spine takes about 30
seconds while the automatic repositioning of the
Vertebral Metrics - Application of a Non-invasive System to Analyse Vertebrae Position using Two Seating Platforms
239
mechanical structure to return to the initial position
takes 15 seconds approximately. Thus the time
required to perform five consecutive acquisitions is
about 4 minutes which is too long for any person
stand perfectly still. Although Vertebral Metrics not
touch the volunteer’s backs, motion artefacts were
identified between scans. Postural adjustments
performed during the repositioning of the mechanical
structure are the cause of the artefacts.
Overall, remarkable differences were not found in
vertebrae position regarding to the use of an
ergonomic seating or a lab seating. Also results does
not allow to conclude the adjustment performed by
each seat. However, spinal curvatures as well as
lateral deviations are properly viewed from data
collected with Vertebral Metrics.
The study proved that Vertebral Metrics has a
strong potential to become a powerful tool to evaluate
the spinal column curvatures in standing or sitting
position. This unique and already patented device will
avoid unnecessary invasive methodologies as well as
qualified staff for screening and prevention of spinal
disorders because it will allow repeated scans without
causing damage to the individuals. Vertebral Metrics
will also became available the definition of the most
appropriate intervention methodologies to each
particular clinical case.
ACKNOWLEDGEMENTS
The authors express gratitude for the precious
collaboration of the ten volunteers recruited to
perform this study. Also the author would like to
acknowledge NGNS – Ingenious Solutions for the
support provided during the development of
Vertebral Metrics.
REFERENCES
Chen, P.L., Dumas, G.A., Smith, J.T., Leger, A.,
Plamondon, A., Mcgrath, M.Y., Tranmer, J.E., 2006.
Analysis of self reported problematic tasks for pregnant
women. In Ergonomics, 49 (3): 282-291. PUBMED.
Gabriel, A., Quaresma, C. and Vieira, P., 2015a.
VertebralMetrics - Automation of a Non-invasive
Instrument to Analyse the Spine. In Proceedings of the
International Conference on Biomedical Electronics
and Devices (BIODEVICES-2015), 150-155.
SCITEPRESS.
Gabriel, A., Quaresma, C., Secca, M.F. and Vieira, P.,
2015b. VertebralMetrics - Automation of a Non-
invasive Instrument to Analyse the Spine. In World
Congress on Medical Physics and Biomedical
Engineering, June 7-12, 2015, Toronto, Canada,
51:1286-1289. SPRINGER.
Harlick, J.C., Milosavljevic, S., Milburn, P.D., 2007.
Palpation identification of spinous processes in the
lumbar spine. In Man Ther 12(1):56-62. PUBMED.
Hinman, M.R. 2004. Comparison of Thoracic Kiphosis and
Postural Stiffness in Younger and Older Women. In
Spine J. 4(4):413-417. PUBMED.
Jordão, A., Duque, P., Quaresma, C. and Vieira, P., 2011.
Development of Vertebral Metrics – An instrument to
study the vertebral column. In Proceedings of the
International Conference on Biomedical Electronics
and Devices (BIODEVICES-2011), 224-229.
SCITEPRESS.
Manek, N.J., MacGregor, A.J., 2005. Epidemiology of back
disorders: prevalence, risk factors and prognosis. In
Curr Opin Rheumatol 17(2):134-140. PUBMED.
Najm, W., Seffinger, M., Mishra, S. et al., 2003. Content
validity of manual spinal palpatory exams – A
systematic review. In BMC Complementary Altern Med
3:1. PUBMED.
Pinel-Giroux, F.M., Mac-Thiong, J.M., de Guise, J.A. et
al., 2006. Computorized assessment of sagittal
curvatures of spine – Comparison between Cobb and
tangent circles techniques. In J Spinal Disord Tech
19(7):507-512. PUBMED.
Quaresma, C., João, F., Fonseca, M. et al., 2010.
Comparative evaluation of the tridimensional spine
position measured with a new instrument (Vertebral
Metrics) and an optoelectronic system of
stereophotogrammetry. In Med Biol Eng Comput
48(11):1161-1164. SPRINGER.
Rubin, D.F., 2007. Epidemiology and risk factor for spine
pain. In: Neulor Clin 25(2):353-371. ELSEVIER.
Seeley, R., Stephens, T., Tate, P., 2003. Anatomia e
Fisiologia, Lusociência, Loures, 6
th
edition.
BIODEVICES 2016 - 9th International Conference on Biomedical Electronics and Devices
240