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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6044_Библиотеки_им_академика_М_И_Перельмана.pdf
19 The Cervico-Cephalic Interaction
199
that removes audio-visual orientation landmarks. Subjects are asked to walk on the
spot at their preferred speed for at least 30 s. Claussen and Claussen [7] used a
metronome in his experiments, but in our experiment the subjects walked at their
preferred speed to avoid the sound of a metronome distracting them. dCCG gives
qualitative information on the pattern of absolute movement and analyses the
following parameters for each marker and for the coupled head and shoulder (trunk)
markers:
Convex mirror
Camera
Rotor
Miners helmet
with head lamps
Eye mask
Shoulder lamp
Radar image like CGP
Fig. 19.1 A schematic representation of CGP (craniocorpography). Subjects walk on place in a
dark room, and movements of the light bulbs placed on the head (helmet) and shoulder impress the
film in an instant Polaroid camera in order to obtain four light traces on a black imagine
200
D.C. Alpini et al.
• Total distance: total distance (in cm) traced by the marker during body
movement.
• Speed: mean marker global speed (cm/s).
• Lateral speed: mean marker lateral component speed (cm/s).
• Longitudinal speed: mean marker longitudinal component.
• Global speed (cm/s).
• Head rotation: represents the absolute difference of head rotation in the transver-
sal plane from the beginning to the end of the test.
• Shoulder rotation: is the absolute difference of trunk rotation from the beginning
to the end of the test.
• Spin body: it shows the relative position of the head with respect to the trunk
during the stepping test.
• Index of coordination (%): because marker movement is composed of longitudi-
nal (body forward projection) and lateral (body sway) components, it compares
the two components to calculate lateral dispersion of body movement during
forward progression.
Due to the complexity of the data analysed for each marker, a coefficient of performance (CP) was calculated to simplify the cut-off between normal and pathological tests. CP clearly identified an abnormal stepping pattern.
Fig. 19.2 Two passive reflective markers (front and rear) are set at the extremities of a stick
attached to a worker’s hardhat, while two markers (left and right) are attached on rigid shoulder
supports
19 The Cervico-Cephalic Interaction
Fig. 19.2 (continued)
201
By means of dCCG, Alpini et al. [10] investigated 25 healthy subjects and 33
WAD’s patients. Whiplash patients were classified as chronic (more than 6 months
after injury) and recent (less than 6 months after injury). Clear differences
between healthy subjects and patients were seen and three different patterns were
detected:
• Pattern A: patients appeared similar to normals but quantitative analysis showed
significant differences with paradoxical head over-stabilization (collar-effect).
• Pattern B: with decreased head stability.
• Pattern C: with decreased head stabilization and reduced displacements of the
body.
Whiplash patients presented also different abnormal findings with respect to the
different parameters considered, but all of those with pattern B or C showed abnormal
CP, that to say whiplash patients presented a specific abnormality in head-to- trunk
stabilization. Head destabilization following whiplash may be correlated to a central
failure of head anticipatory stabilization. Anticipatory postural adjustments mean
that the onset of postural change occurred before the onset of the postural disturbance
due to the movement. Thus, a feedforward postural control is associated with movement control, which prevents the posture and equilibrium disturbances associated
with movement performance from taking place. From these data, it seems that sensorimotor mechanisms progressively lose the ability to maintain head posture during
movement with a progressive alteration of movement pattern of the whole body the
longer the interval after trauma. Thus, while pain and neck stiffness are more frequent
202
D.C. Alpini et al.
in the early period from trauma, complex disorganization of dynamic equilibrium
seem to be a more significant feature later. Complete pattern disruption was evident
in patients with pattern C in which head velocity was increased, rotation of the shoulder and body torsion increased and dynamic control of body centre of mass lacking,
which lead to a nonprogressive or sometimes a backward stepping pattern.
Decreasing body forward progression may also be due to direct involvement of
thoracic and cervical muscle proprioceptive disturbance. Only in patients with a
indicate that the specific locomotor task was not disturbed. Thus, the CP is consistent with and can indicate normality of stepping control.
Different stepping patterns in different subjects after similar injuries may be
explained by the intermodular model of postural control that may be controlled both
in a bottom-up and in a top-down manner according to the task and the environment.
In this way, whiplash could lead to significant alterations of dynamic postural control in those subjects preferentially organized with a top-down posture control.
In order to estimate the effects of cervical proprioception disturbance in WAD
group, only ‘chronic’ patients, with a trauma which occurred more than 6 months
before examination and still suffering neck pain and dizziness, were considered. All
the subjects, with eyes closed, walked on place on rigid surface (RIG) and on foam
(FOAM). In RIG test, head stabilization is depending on vestibular and proprioceptive cues, while in FOAM test, improved vestibular control of head stabilization is
required. Both NORM and WAD adopted a personal frequency of steps; the dura-
tion of test depends on the cadence of the subject considered since almost 60 steps
and 35 s were required. An optoelectronic system ELite (BTS Bioengineering
S.p.a.) (sample rate 25 Hz) [11] composed of two CCD cameras mounting wideangle objectives (C-Mount ¼″ with 2.8 mm focal length) was used. The two cameras captured the movement of six passive markers placed on the subject (three
(front, rear, head) were fixed on an helmet referring to the head and three (left, right,
shoulder) were attached on two rigid shoulder supports defining the trunk)
(Fig. 19.3).
Cameras acquired the movement of the subject in the whole reference volume
3
that is about 1.5 m
from a close range. The rough 3D data were filtered with an
adaptative low-pass lter (Butterworth – maximum cut-off frequency: 5 Hz); then
some parameters were computed, extrapolated from those used in the 2D analysis
with some improvements and innovation. The following parameters were
calculated:
• Global displacement [cm]: geometrical distance from the starting and the ending
position of the rigid body.
• Speed [cm/s]: ratio between the path (sum of the geometrical distances between
the positions assumed by the rigid body frame by frame) and the duration of the
test.
• Rotation [degrees]: rotation angle of the rigid body in the horizontal plane, com-
puted using ZYX Eulerian convention.
• Spin Body: sum of the of rotation angles of head and trunk in the horizontal
plane.
TH
19 The Cervico-Cephalic Interaction
Fig. 19.3 Six markers
placed on the subjects: 1
mFront, 2 mRear, 3 mHead,
4 mLeft, 5 mRight, and
6 mShoulder. 1, 2 and 3 are
fixed on a rigid helmet
referring to the head, while
the others are attached on two
rigid shoulder supports
defining the trunk
6
203
1
3
42
5
• Disharmony: it represents the capability of the subject to keep the same stepping
frequency during the test. High values of this parameter indicate an incapability
to keep the same pace during the test.
• Steps per minute: number of steps made in the trial normalized with the duration
of the test in minutes. The number of steps was computed starting from the lat-
eral path. In particular the change of sign of the first derivative of this variable
was assumed to be a step. So the sum of all these changes normalized to the
duration of the trial corresponds to the step per minute parameter.
• Index of coordination (IOC): ratio between an ideal path and the global path.
• Instability: it is the capability of the subject to maintain the same position after
the double step. High values indicate the incapability to stay on the place during
the test. In particular, instability is the ratio between the ideal path (previously
computed) projected onto the two components lateral and longitudinal and the
number of barycenters of cluster of data.
• Coefficient of performance (CP) was implemented (see Eq. 19.1). It is defined as
the normalized sum of the statistically meaningful parameters (N).
p
P
TO
0.05
k
Parameter
Parameter
k
EALTHY
j
(19.1)
Log
NN
CP
=
∑
=K 1
All the parameters, with the only exception of rotations and trunk lateral dis-
placement, show higher values in WAD than in NORM (Fig. 19.4).
204
Closed eyes foam
12
10
Whiplash
0
CP
CP for WAD people
D.C. Alpini et al.
Median: Box: 25 %, 75 %: Whishker: Min, Max
8
6
4
2
0
Fig. 19.4 Head and trunk lateral/longitudinal instability: comparison between healthy subjects
and whiplash people. Data are expressed as median, 25th and 75th percentiles (box) and maximum
and minimum values (whisker). All the differences are statistically meaningful
4
3.5
3
2.5
2
1.5
1
0.5
Fig. 19.5 Coefficient of performance for whiplash people: each subject presents higher value
than normalcy
All the parameters that presented significant differences were used to calculate
H Lat instability H Lon instability T Lon instabilityT Lat instability
Healthy
CP. Figure 19.5, shows that CP increases 57 % in WAD people with respect to
NORM (the median values of the normalcy is about 1).
Stepping on a foam requires optimization of vestibular control. Generally speak-
ing, findings show that WAD are disturbed in keeping the segment head to trunk
19 The Cervico-Cephalic Interaction
205
during locomotion as a rigid body. While in healthy people sensorimotor control is
as efficient despite surface conditions, in whiplash people vestibular system seems
no more able to provide adequate head control if it is not sufficiently supplied by
podalic cues.
The hypothesis of rigid bodies is also useful to lead the analysis on the three
anatomical components of some of the described parameters since it allows to
define the subject reference system. As a matter of fact, the CP is able to well characterize the two groups, with high values of CP in WAD (Fig. 19.5), making feasible
a possible clinical application of this tool.
WAD present lower (not statistically significant) rotations due to their lower step
frequency and to the duration of the test that is shorter than healthy people and so it
is probably stopped before the beginning of rotation.
dCCG (2D and 3D) have been performed by means of prototypes. A CCG
commercial equipment is CMS 70P (Zebris, Tubingen). It consists of a measuring sensor with integrated revaluation electronics and stand, a PC plug-in card.
The measuring procedure is based on the exact determination of the 3D position of small ultrasound transmitters as markers, by measurement of the sound
pulse time. The measuring system operates up to distance of 2 m. Markers are
attached in a standard manner by means of adhesive patches to the hip, knee,
ankle and ball of the foot on both sides of the body. To determine the gait
phases, thin foot contact switches are stuck to the heel and the ball of the foot.
The left and the right side of the body are measured in succession. After the
interactive selection of the time segments to be analysed, a report is automatically prepared. Here, angles of the joints, the foot rotation and the lateral movements of the extremities are presented as time-dependent curves and as
maximum values. The individual gait phases, the step length, the cadence and
the average speed are evaluated. Information about instabilities is obtained
from the averaged and normalized curves of all individual steps and their standard deviation.
Experiments performed with dCCG suggest that the most specific parameter able
to discriminate between normal and pathological cervico-cephalic control is the
ratio between head and trunk displacements. It is so possible to detect directly head
and trunk sagittal (Y) and lateral (X) movements using a commercial equipment
(Delos, Turin, Italy) that uses two accelerometers 2D sensitive [12], respectively,
fixed to the occiput and to the sternum (Fig. 19.6).
Delos equipment records 20″ body segments movements each test. The following parameters are calculated:
• Total displacement of each segment (degrees) in X and Y plane.
• Bi-dimensional total displacements of the body segment. In this way a
stabilogram- like imagine can be obtained (Fig. 19.7).
• X and Y velocities (degrees/s) for each segment.
• Head-to-trunk stability index (ratio between X or Y head and trunk displace-
ment). A ratio <1 indicates stabilization of the head with respect of the trunk.
Normal values range from 0.6 to 0.8. Values around 1 are considered border line,
while ratio >1 are pathological.
206
Fig. 19.6 An accelerometer
is fixed on the head and the
other on the trunk in order to
record sagittal and lateral
displacements of the two
body segments
D.C. Alpini et al.
Two standard tests allow to investigate head-to-trunk stabilization:
• Head Stabilization Stance Test: evaluation of head-to-trunk stabilization during quiet
steady stance (H-STAN) with eyes open and closed on firm and foam surfaces
• Stepping Test (STEP): evaluation of skill to maintain head stable with respect to
the trunk during walking on place
19.2.1 H-STAN
Maintaining postural stability involves coordination of mechanical components of
the limbs, the trunk and the head and sensorimotor antigravitary network, and it
requires a correct perception either of the position of whole body with respect to the
environment or the reciprocal position of each body segment. In quiet stance body
segments are aligned along vertical axis, and they are theoretically stabilized one
with respect to the other (e.g. head with respect to the trunk) during body oscillations that occur along the ankles maintaining upright position (Fig. 19.8).
19 The Cervico-Cephalic Interaction
Fig. 19.7 Stabilogram-like images obtained during a standard five-conditions (eyes open and
closed on firm and foam surface, head retroflexion) posturographic test by means of trunk
accelerometer
207
In whiplash patients, this test is as frequently abnormal in eyes-closed condition
on foam as the trauma is recent, that to say that cervical muscles are not able to counteract trunk sway in order to maintain body as a whole rigid inverted pendulum.
Head and trunk sway are represented as superimposed cones. In normals (left)
head cone is smaller than trunk cone and head-to-trunk ratio is less than 1, while in
a patient (right) the pattern is reversed.
19.2.2 STEP
Patients were requested to quietly walk on place in a quiet room in two different
conditions: eyes open and eyes closed.
Different findings have been noted regarding dynamic head stabilization during
walking on place. Human walking is a complex activity, and maintenance of equilibrium is a particularly challenging task for the human postural control system because
our centre of mass is located a considerable distance from the supporting surface and
for a major period of the walking cycle the body is supported by a single limb with
the centre of gravity (CG) passing outside the base of support. During locomotion,
alignment and respective balance control of each superimposed segment have to be
continuatively controlled in order to provide head stabilization (Fig. 19.9).
In chronic whiplash, patient’s abnormal head-to-trunk pattern in X and or Y plane
can be recorded with same frequency of the experimental data obtained by dCCG.
208
x plane ratio 0.8
x plane ratio 1.4
s
D.C. Alpini et al.
Fig. 19.8 H-STAN
30.2°
Head
velocity
degrees/s
53.8°
Fig. 19.9 As in Fig. 19.8 at
left a normal STEP test and at
right a pathological tests with
increased head sway with
respect to the trunk
37.8°
Head-to-trunk
Tr unk
velocity
degrees/s
Head-to-trunk
284.6°
322.5° 258
Trunk
velocity
308
Head-to-trunk
x plane ratio 1.2
39.6°
Head
velocity
degrees/
19.3 Smooth Pursuit Neck Torsion Test (SPNT)
Whiplash produces a complex disturbance of sensorimotor control of oculomotion,
balance and locomotion, involving both peripheral and central processing of eyehead- neck coordination [13].
Head-to-trunk
x plane ratio 0.8