4. Fundamentals of Motor Disabilities
1. Disorders of propulsive movements (Difficulty in alternation)
Co-ordination
Basically smooth reciprocal movements of each joint and smooth
alternation of each extremity bring about coordination in human
movement. In cerebral palsy, coordination is disturbed by both
difficulties in reciprocal movements of the joints and alternation of
each extremity.
Reciprocal movement
One of the most basic motor disorders in cerebral palsy is
difficulty in reciprocal movements in each joint. Forward propelling
such as in crawling and walking is caused by combined propulsive
movements of the trunk and extremities. Furthermore, propulsive
movements of the trunk, and upper and lower extremities are due to
propulsive movements in all the involved joints. Reciprocal
movements of the flexors and extensors in the involved joint cause
propulsive movements in each joint. So, if reciprocal movements of
the flexors and extensors are disturbed, propulsive flexion-extension
movements in each joint of the extremity is inhibited and thus,
forward propelling such as in crawling and walking is inhibited.
Basically, difficulty in reciprocal movement is caused by
shortened excursion of the flexors and extensors due to hypertonicity
in these muscles at each joint. So, in order to restore all propulsive
movements, reciprocal movements have to be restored by relieving
the shortened excursion of the flexors and extensors. In quadriplegic
patients, reciprocal movements are disturbed in all four extremities,
by shortened excursion of each flexors and extensors. In bipedal
patients, shortened stride is caused by difficulty in reciprocal
movements due to hypertonicity. In order to increase stride length,
the shortened excursion of the flexors and extensors should be
lengthened and reciprocal movements have to be restored.
Crossed pattern movement
Another problem, which disturbs forward propelling, is difficulty
in crossed pattern movements. The crossed pattern movements are a
matured movement in which the body is functionally separated into
four parts, and each part moves separately in a crossed manner,
while producing effective locomotion. In matured crawling in
human body, the forward swing of one side of the upper extremity
quickly leads the forward swing of the opposite side of the lower
extremity in a crossed manner. Then, the forward swing of the
upper extremity on the same side follows. This forward swing of the
upper extremity triggers the forward swing of the lower extremity
on opposite side in a crossed manner.
The primitive locomotion patterns such as total extension-flexion
movements (TLR), asymmetrical locomotion (ATNR), and
symmetrical locomotion (STNR) are movement patterns with
difficulty in crossed pattern movements in all the four extremities,
and also are the ones with difficulty in flexion-extension reciprocal
movements in each joint. To lessen these difficulties in propulsive
movements, phylogenetic development of propulsive movements in
humans is reconsidered and mechanics of crossed movement pattern
have to be analyzed.
Phylogenic development of propulsive movement
Propulsive muscles as a driving power:
The essentials of movements in all animals are that they are the
driving forces to find food and to survive. To drive the body
forwards, propulsive power is necessary. So, to produce propulsive
power, the vertebrates have developed a specific propulsive muscle
mechanism.
Originally, propulsive power is produced with extension
movements of the trunk and limbs by the extensors. The power of
these extensors is considered to thrust the body forwards. To
accomplish this extension movement, a prior flexed posture must be
provided by the activity of the flexors. Thus, the primitive reciprocal
flexion-extension movements must have been borne out of the
flexors and extensors in the vertebrates, producing the propelling
force for locomotion. Now, we can understand that these reciprocal
flexion-extension movements are the original forms of locomotion.
The huge paravertebral muscles located on both sides of the
vertebrae in the fish are propulsive muscles, enabling the fish to
swim easily. Here, longissimus muscles in the humans could be
vestigials of these propulsive muscles. Of course, multiarticular
paravertebral muscles observed in the reptiles and snakes are also
propulsive muscles. It is obvious that these big paravertebral
muscles have no antigravity activity. One can confirm this idea from
the fact that the fish cannot hold on to an upright posture, when
taken out of water and placed on the ground where the earth's gravity
is acting, although they have huge paravertebral muscles. Thus, it is
considered that the vertebrates had originally developed propulsive
paravertebral muscles on the sides of the vertebral structure for
locomotion.
Propulsive mechanism:
It is obvious from observations of all propulsive movements of
the vertebrates that the propelling force of the body is produced by
the power of extensor muscles of the trunk and extremities. All the
driving force for swimming in the fish, jumping in the frogs,
running inn the animals and humans are also produced by the
extension force of the extensors. So, in order is to drive the entire
body of the animals and humans forward, the extensors are needed
to develop more powerfully than the flexors. The flexion
movements of the limbs and trunk are also necessary, in order to
provide the flexed posture from which the succeeding extension
movements of propulsion are initiated. The flexors can be small and
weak compared to the extensors, since they are only used for
positioning the extremities in flexion without driving the whole
body forwards. In most of the vertebrates, the extensors are located
on the dorsal side of the body, and are big, thick and strong,
whereas the flexors are located on the ventral side of the body, and
are small, thin and weak. The differences in muscle size and
strength between extensors and flexors explain that the force of the
extensors are necessary for propelling the whole body weight
forwards, whereas the flexors are used only for positioning the
extremities without driving the whole body directly. These
differences clearly explain the reason why extensor pattern is
predominant in cerebral palsy.
Now, it is well understood that these propulsive muscles are
anatomically multiarticular. Representatives of these multiarticular
muscles are the paravertebral muscles located just along the
vertebrae. They act mostly for propulsion in the fish. Antigravity
monoarticular muscles are not well developed in the fish. Only
small muscles are developed and located near the dorsal and
abdominal fins. In the amphibians, most of the muscles are still
multiarticular, though poor monoarticular muscles are already
differentiated. They prefer living in water, where strong gravity
does not work upon them. At this level, propulsive mechanism by
multiarticular muscles is still dominant.
Propulsive locomotion
with crossed movement:
In the amphibians, primitive antigravity monoarticular muscles
are poorly developed. These muscles make individual crossed and
alternate movements in all the four extremities possible, resulting
in an effective locomotion. The amphibians such as salamander
use crawling movements in crossed and alternate pattern with separated
movements of all the four extremities, especially in water. The
crossed movements are a well organized locomotion, supported by
combined activities of the multiarticular muscles and the monoarticular
muscles, making locomotion on the ground and in water feasible
for amphibians, reptiles and mammals (Fig. 10).
Propulsive mechanism inherent in the humans
Total extension movement:
Total extension movements are usually latent in humans, covered
by fully developed antigravity activities. These movements are seen
at the starting position of backstroke in swimming, in which total
extension force is used for propulsion in supine position. These
movements are mostly reproduced in newborn babies, in the form of
backward thrust with extension of the extremities and trunk in
supine position, in which antigravity movements are not sufficiently
facilitated (Fig. 26).
Hemilateral extension-flexion movements:
These movements are also latent in humans, covered by a
well-developed antigravity activity, but this can be seen in wheel
chair movement. Backward locomotion with unilateral extension of
the body and lower extremity in wheel chair can be a form of this
primitive locomotion in supine position. Antigravity activity is not
necessary in this locomotion. Ontogenetically, these movements can
also be reproduced in babies, in the form of backward locomotion
in supine position where body movements are longitudinally divided
into two parts. They propel themselves changing the side of
extension in the extremities and trunk.
Symmetrical locomotion:
Symmetrical locomotion is usually latent, but seen, in special
situations, such as the breast stroke, rowing a boat and jumping on
a vaulting box, where strong propulsions of the body are required.
Body movements are divided into the two parts (upper and lower)
which flex and extend alternately. This locomotion is also
reproduced in babies in the form of symmetrical crawl where they
propel themselves, extending and flexing both upper and lower
extremities symmetrically.
Crossed pattern:
Crossed and alternate patterns of movements are seen in various
phases of human locomotion. Bipedal alternate movements are a
highly matured form of crossed and alternate patterns of
locomotion. Mermaid and four-point crawl with crossed and
alternate pattern in babies are reproductions of crossed pattern
movements seen in the amphibians, reptiles and mammals.
Thus, various types of locomotion are latently included in
human bipedal locomotion. With these mechanisms of locomotion,
the purpose to reach to various objects can be accomplished. Reach
activities in the upper extremities can also be included in this
propulsive activity.
Dysfunction of propulsive mechanism in cerebral palsy
Disturbance of propulsive mechanism in each joint (Rigidity):
As previously mentioned, propulsive mechanism is brought
about by reciprocal flexion-extension movements. In cerebral palsy,
reciprocal flexion- extension movements are inhibited by
concomitant contractions of the hypertonic agonists and antagonists.
Hypertonicity of the extensors inhibits smooth movements of
flexion, while hypertonicity of the flexors inhibits smooth
movements of extension. These concomitant inhibitions cause
rigidity of the joints, while shortening stride length, reducing range
of motion in flexion and extension of the limbs, losing smoothness
of the joint movement and disturbing effective propulsion. In order
to activate propulsive movements of the body in gross motor
functions, such as turnover, crawling, kneeling, walking and reach
activities, it is necessary to relieve rigidity of the joints, increase
range of motion at each joint, and elicit smooth movements of the
joints, by selective release of the hypertonic muscles on both flexor
and extensor sides (Fig. 16AB, 18AB).
Difficulty in crossed and alternate pattern movement:
Another mechanism which disturbs the effective propulsive
movements is non-separated movements of the extremities observed
in total extension and flexion patterns such as tonic labyrinthine
reflex, asymmetric tonic neck reflex and symmetric tonic neck
reflex. These non-separated movements cause difficulty in
alternation and make locomotion quite ineffective. In severely
involved patients, these non-separated locomotion movements with
difficulty in alternation are combined with difficulty in
flexion-extension movements in the extremities and in rotation
movements in the spine, and cause abnormal postures, called as
tonic labyrinthine reflex, asymmetric tonic neck reflex and
symmetric tonic neck reflex. In order to restore effective propulsive
locomotion in turnover, crawling, and kneeling, it is also essential
to gain separate crossed pattern movements, by activating
antigravity muscles, then separating the non-separated movement
and facilitating alternation, by the use of orthopaedic selective
spasticity-control surgery (Fig. 16AB, 19AB, 23AB). Thus,
orthopaedic selective spasticity-control surgery is effective for
regaining coordination of movements in cerebral palsy and for
gaining smooth propulsive movements.
2. Disorders of antigravity (body-supporting) movement
Another most serious disability of cerebral palsy is loss of
antigravity activities, caused by paralysis of the antigravity
monoarticular muscles. The monoarticular muscles differentiated
from the multiarticular muscles in the process of phylogenetic
development are paralyzed, causing decrease in antigravity activities.
This antigravity activity is the same entity, called as the righting
activity or righting reaction, in the field of neurology. The
antigravity mechanism has matured in the vertebrates over a period
of development, enabling the mammals to move in quadrupedal
locomotion and the humans to keep upright bipedal posture. So, in
order to facilitate antigravity activity in cerebral palsy, the entity of
antigravity mechanism has to be analyzed, phylogenetically,
ontogenetically and motor-function-wise.
Development of antigravity activities
What does antigravity activity mean?:
We have mentioned that propulsive movements are indispensable
for survival of the vertebrates. Furthermore, in order to move
effectively, the vertebrates have to develop some antigravity
activities, such as keeping the body in prone and upright positions,
so as to keep the body away from ground in quadrupedal
locomotion (Fig. 20B, 40C, 41B, 70AB).
Antigravity mechanisms help the vertebrates to keep itself in
prone position, raise the body away from the ground and support the
body in the upright posture, against gravity. There are definite
differences between antigravity abilities in each vertebrate. The
fishes, which can keep themselves prone only in water where strong
gravity is negated, have poor antigravity activities. The amphibians,
which can keep their bodies in prone position on ground, have a
relatively developed antigravity activity. Mammals have
well-developed antigravity activities to keep the trunk away from
the ground for quadrupedal locomotion. Humans have highly
developed antigravity activities to keep the body in an upright
posture. So better the antigravity activities, better are the motor
abilities. Humans are the vertebrates, which have developed the
highest antigravity activities such as bipedal locomotion in an erect
posture (Fig. 1ABCD).
Primitive antigravity mechanism (righting):
In fish, small antigravity muscles are developed around the fins
of the back and abdomen. They keep the body in a prone position
in water, and effectively help forward swimming (Fig. 27). The
muscles attached to the back fins can be the original form of the
long and short rotatores of the human spine, while the muscles
attached to the abdominal fin are the original form of hip adductors
and abductors which keep the body in a prone position. However,
antigravity activities at this level are too small, and cannot act
outside water, where strong forces of gravity act. They cannot keep
the body in prone position, or move it in crossed pattern on the
ground and outside water.
Fig. 27
Antigravity activities to keep the body in prone position:
Crawling on the ground is propulsive movements supported by
strong antigravity activities. Since strong forces of gravity from the
ground, act on the body, strong antigravity mechanisms are needed,
to keep the body prone and to drive the body forwards in prone
position. Turnover is also another important antigravity activity to
turn the body into prone position. The vertebrates have developed
strong antigravity abilities to enable themselves to crawl on the
ground in prone position. The antigravity mechanism to keep the
body in prone position is due to antigravity activities of the
monoarticular muscles, such as adductors and abductors of the hips
and shoulders and rotators of the trunk (Fig. 10, 28, 45). Turnover
movements are also made feasible by antigravity activities of the
monoarticular muscles, such as adductors and abductors of the
extremities, as well as rotators of the trunk (Fig. 36, 37, 38). Thus,
prone locomotion in the amphibians is supported by antigravity
activities of the monoarticular muscles in the extremities and trunk.
Antigravity activities to keep the body in prone position and to turn
the body to prone position are called, as a righting reaction in
neurological terminology.
Fig 28. Under construction
Antigravity activities to keep the body in the quadrupedal position:
Quadrupedal posture is a well-developed antigravity posture for
locomotion. Locomotion with both fore feet and hind feet is a
propulsive movement with well-developed antigravity activity. Most
of the mammals have gained this antigravity mechanism, to raise
their body from the ground, and make more effective locomotion
feasible as well as to change their postures on the ground (Fig. 7A,
10, 70B).
There are great differences in antigravity activity between
quadrupedal locomotion and mermaid crawl locomotion. In
mermaid crawl, the body is on the ground. Activities of the flexor
and extensor muscles for forward locomotion are predominant, and
are used to drive the body forwards. As the trunk is supported on
the ground in this level, body-supporting mechanisms on the
extremities are not necessary. Also as the trunk is on the ground,
quick movements are not possible. On the other hand, in the
quadrupedal locomotion on both the fore feet and hind feet, the
monoarticular muscles in the flexors, extensors, adductors and
abductors are well developed while stabilizing the proximal joints,
such as the shoulders, elbows, hips and knees, and keep the body
away from the ground (Fig. 20B, 40C, 41B). This results in more
quick and effective locomotion and makes change of posture
feasible.
Bipedal standing:
Now, human species, which had already developed quadrupedal
locomotion in the process of evolution, began to gain highly
developed antigravity abilities, such as bipedal standing and
walking. In standing, motor functions in upright posture are due to
development of strong antigravity muscles in the lower extremities
(Fig. 10). In the hip, the gluteus maximus, medius and minimus are
well developed, and make upright standing feasible (Fig. 54, 55). In
the knee, the vastus medialis, lateralis and intermedius are well
developed and they make it possible to keep the knee in full
extension (Fig. 55). In the feet, the soleus muscle is well developed
and supports the weight of the human body (Fig. 55). To raise the
lower extremity upwards, the iliacus in the hip, the tibialis anterior
and peroneus brevis in the leg are also well-developed (Fig. 55
middle). In the spine, long and short rotatores and multifidus
muscles are developed and these muscles keep the body upright
(Fig. 1AB, 45). These muscles are all short monoarticular muscles.
These observations show that standing ability mostly depends on
full development of these antigravity monoarticular muscles
(Fig. 1AB). Of course, skeletal changes too along with muscular
development are indispensable for standing. Now, the human
species has achieved an elaborate bipedal locomotion system, with
the development of antigravity muscles. At the same time, humans
have also a developed highly organized central nervous system in
layers in the brain, besides the development of musculo-skeletal
system.
Development of skill-related movements in the upper extremity:
In the process of development, human species shifted their living
style to the arboreal life in the forest, from the quadrupedal
locomotion on the field. At this stage, the functions of the upper
extremities have developed enormously. The process of this
evolution will be discussed later.
Dysfunction of the antigravity activities in cerebral palsy
Paralysis of the monoarticular muscles:
It is understandable that the monoarticular muscles, which have
been differentiated in the process of development, are easily
paralyzed by damage of the central nervous system, resulting in
decreased antigravity activities. In the hip joints, insufficiency of
the gluteus maximus, medius and minimus will result in
disturbances in gaining full extension and achieving standing in
erect posture. Similarly in the knee, insufficiency of the vastus
lateralis and medialis will result in disturbance in gaining full
extension, causing flexed posture such as crouched posture and
crawling postures. Also in the feet and ankle, insufficiency of the
soleus muscles and short plantar flexors results in disturbances in
standing ability. With weakness of the deltoid and pectoralis major
in the shoulder, and the brachialis and triceps brachii in the elbow,
combined with weakness of antigravity muscles of the knees and
hips, crawling on hands and knees will deteriorate. With paralysis
of the monoarticular muscles in the upper extremity, the skills are
definitely damaged. Turnover activity is also damaged with loss of
antigravity activities of the monoarticular pectoralis major, teres
major, obliquus internus abdominis and adductors and abductors of
the hip. Thus, difficulties in the gross movements of turnover,
mermaid crawl, quadrupedal crawl, standing and bipedal
locomotion are induced, and its severity depends on the degree of
weakness of the monoarticular muscles.
Inhibition of activities of the monoarticular muscles by
hypertonicity of the antagonistic multiarticular muscles:
The another important and interesting feature in muscular
activity observed in cerebral palsy is that activity of the
monoarticular muscles is depressed, by hypertonicity of the
antagonistic multiarticular muscles. This finding definitely presents
us a great opportunity to facilitate antigravity activities of the
weakened monoarticular muscles, by decreasing the hypertonicity
of the multiarticular antagonists. In hip joints, activities of the
monoarticular gluteus maximus muscle can be facilitated by the
release of the antagonistic psoas and rectus femoris and effective
erect posture can be attained. In patients with difficulty in crawling
on hands and knees by hyperextension of the hips, antigravity
activities of the monoarticular iliacus, adductor longus and brevis
and anterior part of the gluteus medius can be facilitated by
proximal release of the antagonistic semimembranosus. Thereby,
effective crawl on hands and knees can be made feasible. In the
patient with difficulty in mermaid crawl due to retraction
(hypertonicity) of the shoulder, antigravity activities of the
monoarticular deltoid muscle can be activated by release of the
antagonistic latissimus dorsi. Hence, forward flexion of the upper
extremities is facilitated, and forward crawl in crossed pattern can
be attained.
Thus, by understanding the consistency and characteristics of
weakness and hypertonicity of various muscles, and by application
of these considerations to surgery, that is orthopaedic selective
spasticity-control surgery, improvements in various types of motor
dysfunction can be realized.
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