Fig. 2A
Fig. 2B3. Motor-functional
Characteristics of Hypertonicity
ﾊ1.
Background of orthopaedic selective spasticity-control surgery
ﾊﾊﾊ ﾊconcept
The most fundamental motor abnormality in cerebral palsy is
hypertonicity of the muscles including spasticity, rigidity and athetoid
movement. Spasticity is a reflection of hypertonicity accompanied by
increased deep tendon reflexes, clonus and a pathological plantar
response. Rigidity is interpreted as a condition of stiffness or
difficulty in the reciprocal movements of the joint which is caused
with concomitant contraction of the hypertonic muscles on both the
flexor and extensor sides. Rigidity in cerebral palsy is always
accompanied by spasticity and is different from the pure form of
rigidity as in Parkinsonism. Athetosis is also a movement disturbance
with clinical reflection of fluctuating hypertonicity in both the flexors
and extensors.
Here in this book, we have decided to use the term
"hypertonicity" for all entities which include all of these hypertonic
conditions and which are subjected to treatment by our surgery.
Hypertonicity results in hyperextension of the neck and trunk,
restricts reach-movement of the upper extremity, decreases skills of
the fingers and hand, induces dislocation of the hip, causes crouched
posture, scissors posture and windswept deformity, and then inhibits
stable sitting, standing and gait. Thus, a profound understanding of the
characteristics and consistency of the hypertonicity and the one being
subjected to surgery and physiotherapy is essential. We had an
opportunity to be aware of the functional consistency in hypertonicity
of the muscles in the process of treating motor disability surgically.
On the basis of these consistencies, attempts to reduce hypertonicity
have been carried out.
Clinical analysis of hypertonicity
Hypertonicity in the hip adductors:
Our consideration about consistency of the hypertonicity in
cerebral palsy was originally initiated with retrospective analysis of
the adductor release operation, which is one of the most common
operations for treatment of cerebral palsy.26
For adduction deformity of the hip, the gracilis, adductor longus
and adductor brevis have been considered, as the most responsible
muscles, and release of these three muscles including neurectomy of
the anterior branches of the obturator nerve had been advocated for
its correction, as an established procedure. However, experimentally,
we noted the fact that stability and style of the gait did not improve
in most of the patients who had anterior obturator neurectomy and
wondered whether the anterior obturator neurectomy is effective or
not in achieving gait stability and consequently in improving gait
pattern. To clarify these questions, we conducted a clinical
comparative study between a group in which adductor release and
anterior obturator neurectomy was performed and a group in which
only the gracilis and adductor longus were released.26
During this comparative study, a question arose about each of the
gracilis, adductor longus and adductor brevis which are different in
their length, their insertion and their origins as to, what the functional
differences between these three adductor muscles would be.
This study clearly demonstrated that the excessive abduction gait was
induced and no improvement in gait ability was seen in the group in
which all the three adductor muscles were sectioned or anterior
obturator neurectomy was combined with adductor tenotomy. We
noted the fact that if all of the adductor muscles were released, gait
became significantly unstable (Fig. 2AB).
Fig. 2: Deterioration in gait after anterior obturator neurectomy
2A: A 6-year-old boy
Spastic diplegia, ambulatory
Crouched gait with marked internal rotation was observed.
2B: Post-op
Internal rotation still remained. Both hips were abducted.
Deterioration in gait had increased. Both arms were raised
for balancing.
On the other hand, in the groups in which the adductor longus
and brevis were not released and the anterior branches of the obturator
nerve were not sectioned, stability was preserved and gait abilities
improved (Fig. 3AB).
Fig.3B
Fig.3B
Fig. 3: An 11-year-old girl
Spastic diplegia
3A: Crouched posture with adduction and internal rotation of the
hip and equinus of both the feet was observed.
3B: Post-op (OSSCS on hips, knees and feet)
Crouched posture was lessened and plantigrade feet were
obtained.
Another observation is that stability of the hip and body did
not decrease in the group in which the adductor longus and brevis
were not sectioned in spite of the release of the gracilis. This study
highlighted four interesting findings.
1) The adductor longus and brevis are muscles which stabilize the
hip joint, and keep the body upright while preventing unstable
gait. When these muscles were preserved, marked deterioration
in gait did not occur.
2) The gracilis is not related to the stability of the hip and is also not
related to keeping the body upright. Even if this muscle was
sectioned, deterioration in gait did not occur.
3) Adduction deformity was considerably corrected with release of
the gracilis while preserving of the adductor longus and brevis.
The gracilis can be considered to be one of the hyperactive
muscles in the hip adductors in cerebral palsy.
4) Adduction deformity could be considerably corrected in spite of
preservation of the adductor longus and brevis. This fact suggests
that the adductor longus and brevis are less hyperactive and not
so much related to adduction deformity.
These four findings suggested that there are definite differences
in motor-function and in hypertonicity between the adductor longus
and brevis (one-joint muscle) and the gracilis (two-joint muscle)
(Fig. 4). Speculation at this point was that the multiarticular gracilis
is not related to stability functionally, and can be rather hyperactive
in cerebral palsy causing adduction deformity, whereas the short
monoarticular adductor longus and brevis are muscles with activities
to stabilize the hip and to keep the body upright and are less
hyperactive in cerebral palsy.
Fig. 4
Fig. 4: Differences in antigravity and propulsive functions of
adductor brevis, adductor longus and gracilis
(1) The adductor brevis has most antigravity and least propulsive
activities.
(2) In the adductor longus, the muscle fibers originating from the
more proximal portions have more antigravity and less
propulsive activities, while the fibers originating from the
more distal portions have less antigravity and more propulsive
activities. Each fiber is arranged regularly from the proximal
short fibers with no tendon fiber, to the long fibers with
tendon fibers.
(3) The gracilis has least antigravity and most propulsive activities.
Functional differences between the psoas and the iliacus
and their attitudes in hypertonicity:
Flexion deformity of the hip is one of the main problems in
treatment of cerebral palsy. For correction, iliopsoas division was
reported by Bleck et al. However, postoperative weakness in upward
and forward flexion of the hip during crawling and gait presented
difficulty for effective forward and upward swing of the lower
extremity. To prevent this unpleasant complication, Bleck
recommended iliopsoas recession. Here, iliopsoas tendon
is transferred to the anterior part of the joint capsule. However,
results were not so satisfactory, still causing weakening of the hip
flexor and difficulty in forward swing of the limb. Therefore, we were
obliged to conduct a review of hip surgery. In the review of iliopsoas
division surgery, we noticed the fact that the iliopsoas is divided into
two muscles: The multiarticular psoas and the monoarticular iliacus.
These two muscles are different in their form, length and origin.
The psoas is long with a long tendinous insertion.
It runs from the vertebral origins to the lesser trochanter crossing
many joints such as the intervertebral joints and hip joint. Therefore,
the psoas can be called, as a multiarticular muscle. On the other
hand, the iliacus is short with a short tendinous insertion. It
crosses only the hip joint from the iliac bone to the lesser trochanter.
Thus, the iliacus can be called a monoarticular muscle. It thickly
covers the femoral head in the frontal area of the joint and this
coverage seems to stabilize the femoral head in a concentric position.
On the basis of these analyses, we had conducted selective psoas
lengthening while preserving the iliacus as a hip-stabilizer.27
Comparative study between the group in which the iliopsoas
tendon was totally divided and the one in which the psoas tendon
was selectively lengthened clearly demonstrated the differences in
walking form and stability between the two groups. Here,
circumduction gait and difficulty in forward and upward hip-flexion
due to weakness in hip-flexors were observed only in the total
division group (Fig. 5AB),
Fig. 5A
Fig. 5B
Fig. 5: A 7-year-old boy. Spastic diplegia, Non-ambulatory
5A: Crouched posture,
Crouched posture with adduction and internal rotation of
the hips, flexion of the knees and equinus deformity of the
feet was observed.
5B: Post-op
Iliopsoas section was done at insertion to the lesser
trochanter. He improved functionally to an ambulatory level.
But, adduction and circumduction gait due to weakness of
hip flexors remained.
whereas circumduction gait and
deterioration in gait were not observed in latter group. Flexion
power for upward and forward swing was maintained in the selective
psoas-lengthening group and gait was not deteriorated (Fig.6AB).27
This suggests that the iliacus contributes to body-support, hip
stability and antigravity hip-flexion.
Fig. 6A
Fig. 6B
Fig. 6: A 5-year-old boy
Spastic diplegia, non-ambulatory,
6A: Crouched posture with marked flexion and adduction
deformity of the hips was observed.
6B: Seven years after iliopsoas lengthening, proximal lengthening
of the rectus femoris, proximal lengthening of the
semimembranosus, distal intramuscular lengthening of the
rectus femoris, posterior release of the knee and posterior
release of the foot and ankle (OSSCS). He is now a
community ambulator with crutches. He is also an independent
ambulator in the house.
Another observation was also made. Although psoas was
sectioned in the latter group, there was no loss of stability. Thus, this
finding suggests that psoas is not contributing to body support, hip
stability and antigravity hip-flexion.
These studies also revealed another four interesting findings to
us:
1) The iliacus is a muscle that stabilizes the hip, supports the body
and flexes the thigh upwards against gravity. The iliacus can
therefore be called an antigravity flexor.
2) The psoas has no functions to stabilize the hip, keep
body upright and to flex the thigh against gravity. Therefore, the
psoas can be called a non-antigravity flexor.
3) The hypertonicity in hip-flexors was markedly relieved by the
lengthening of the psoas. This fact showed that the psoas was one
of the hyperactive muscles in the hip-flexors in the patients with
cerebral palsy.
4) The flexion deformity could be appropriately decreased in spite
of preservation of the iliacus. This fact demonstrates that the
monoarticular iliacus is less hyperactive and is not much
related to flexion deformity.27
So, we could notice the similarity in form, function and attitude
in hypertonicity, between the short monoarticular adductor brevis
and iliacus. They are short, monoarticular and least hypertonic. Both
muscles work to stabilize the hip and support the body. These
observations led us to a hypothesis that monoarticular muscles with
short tendon fibers or without tendon fibers act to keep the body
upright and are less hyperactive in cerebral palsy.
We can also see the same similarity between gracilis and psoas
muscles. They are multiarticular muscles with long tendonfibers, do
not act to keep the body upright, and are comparatively hyperactive in
cerebral palsy. These observations provided us a basis for
broadening the hypothesis to the level that the multiarticular muscles
do not act to keep the body stable in upright position and are
comparatively hyperactive in cerebral palsy causing abnormal
postures. Here, at this point, the working concept that the
monoarticular muscles are antigravity (body-supporting) while the
multiarticular muscles are non-antigravity, was initiated.26,27 Now
this hypothesis had to be confirmed in other parts of the body.
Functional differences between the gastrocnemius and the soleus
muscle:
Equinus deformity is another serious problem presented due to
hypertonicity of the plantar flexors in the foot and ankle. For
correction, Achilles tendon lengthening or heel cord advancement
has been recommended. However, overlengthening of the Achilles
tendon often leads to calcaneo-valgus deformity due to weakness of
the plantar flexors especially in diplegic or quadriplegic patients.
Stability of the ankle to keep the leg and thigh in upright posture is
incredibly damaged.35 Patients were usually not satisfied with the
functional results even if the deformity was corrected. On the other
hand, appropriate-looking lengthening of the Achilles tendon easily
causes recurrence. It is extremely difficult to achieve a long lasting
stable foot with Achilles tendon lengthening.
To remedy this situation, hypothesis previously introduced was
applied for the treatment in our hospital. The triceps surae muscle
can be separated into two muscle groups: one is the multiarticular
gastrocnemius and the other is the monoarticular soleus. We
assumed that the multiarticular gastrocnemius is a non-antigravity
muscle and more hyperactive in cerebral palsy causing equinus
deformity, whereas the monoarticular soleus is an antigravity muscle
and related to stability of the foot supporting the lower extremities
and trunk in stable upright posture.
On the basis of this hypothesis, a follow-up study of the results
of selective gastrocnemius recession was done. Results were quite
satisfactory (Fig. 3AB, 25AB). The deformity was effectively
corrected and stability had been considerably facilitated.28-30
There was no loss of stability (Fig. 99AB, 107AB, 108AB).
Here again, the hypothesis that the multiarticular muscles are
non-antigravity, whereas the short monoarticular muscles are
antigravity has been proved to be reliable and to be also applicable
clinically in treatment of the equinus deformity. Historically,
selective gastrocnemius release was already advocated by many
surgeons and has gained popularity.31-34 This popularity also
supports our hypothesis.
Functional difference between the monoarticular and
the multiarticular muscles
Thus, the clinical analysis of the hip-adductors, hip-flexors
and plantar flexors of the foot enabled us to formulate the working
concept that muscles in the vertebrate body are grossly divided into
two groups: the multiarticular muscle group and the monoarticular
muscle group. The monoarticular muscles can be considered the
muscles which are antigravity to keep or support the body in
upright posture and therefore they can be called
body-supporting or antigravity muscles (Fig. 7A). Anatomically,
each short monoarticular muscle is located around the joint,
surrounding and wrapping the joint. Therefore, these short
monoarticular muscles seem to play an important role in keeping
the joints stable.
Fig.7A
Fig. 7: Functional difference between the multiarticular muscle and
monoarticular muscles
7A: The monoarticular muscles are antigravity muscles, supporting
the body in the upright and quadrupedal postures against
gravity. Supporting activities of the monoarticular muscles
make propulsive and transfer activities of the multiarticular
muscles effective and fast.
On the other hand, it can be considered that the
long multiarticular muscles are the ones without antigravity
activities (Fig.7B). Here, a question arises as to what does the
activity of the multiarticular muscle mean motor-function-wise
without antigravity function? Is there any activity without
antigravity activities in humans?
Careful observations disclose that movements of flexion and
extension without antigravity activity on the horizontal plane are
observed in
the movements of the mermaid crawl in babies in whom vertical
antigravity movements such as the four-point quadrupedal crawl is
still not activated.35 Flexion and extension movements without
antigravity activity can also be observed at the propelling phase of
patients with delay in motor development and in severely involved
patients with cerebral palsy (Fig. 13A, 14A, 17, 21A). In these
patients, activity of the antigravity monoarticular muscles is still
not attained and three-dimensional crawl such as the four-point
crawl is not possible. This primitive and non-antigravity propelling
movement seems to be caused by activity of the multiarticular
muscles. Therefore, multiarticular muscles are considered the
body-propelling muscles which propel the body forwards on a
horizontal plane without body-supporting activities(Fig. 7B).
Fig.7B
Fig. 7: Functional
difference between the multiarticular muscle and
ﾊﾊﾊﾊﾊ monoarticular muscles
ﾊﾊ7B: The multiarticular muscles are propulsive muscles, propelling
ﾊﾊﾊﾊﾊﾊthe body forwards without antigravity activities.
The interesting point is that the monoarticular and multiarticular muscles are mostly coexisting in various parts of the body.35,61 In the quadriceps femoris, the monoarticular vastus medialis, lateralis and intermedius and the biarticular rectus femoris are co-existing. The monoarticular vastus medialis, lateralis and intermedius are considered to be antigravity knee-extensors whereas the multiarticular rectus femoris is considered to be a propulsive extensor which contributes to body propelling on a horizontal plane. This consideration could be applied clinically for treatment of extension deformity of the knee. Here, the biarticular rectus femoris is selectively released for correction of recurvatum deformity while preserving supporting activities of the vastus medialis, vastus lateralis and vastus intermedius (Fig. 23AB, 25AB). Insufficiency of the quadriceps was not induced in this knee-extensor release surgery.36 In the finger flexors, the monoarticular interossei can be considered to be antigravity supporters of the finger-joints in on-hands posture at quadrupedal locomotion. On the other hand, the multiarticular flexor digitorum profundus and superficialis can be considered to act only in propulsive movements at mermaid crawl in forward locomotion. It is suspected that voluntary and fine movements of the hand and fingers developed with development of the interossei when the human started arboreal life. When the hand is paralyzed, the multiarticular muscles become hyperactive and can inhibit activities of monoarticular interossei and disturb antigravity and voluntary activities of the fingers. On the basis of this consideration, selective release of the multiarticular muscles was done and activation of fine movements of the hand and fingers was achieved (Fig. 8ABCD, 9, 65AB, 73AB, 75AB, 79AB, 83AB, 141AB).37-41
Fig.8A Preop
Fig.8B Preop EMG
Fig.8C Postop
Fig.8D Postop EMG
Fig. 8: Treatment of rigidity of hand caused by co-contractions of
extensors and flexors
8A: 18-year-old male, Athetosis quadriplegia
Involuntary movement and deformities of the fingers, thumb
and wrist with rigidity were characteristic.
8B: Extensors and flexors showed simultaneous co-contractions
regardless of the swing and stance phases.
8C: After OSSCS, rigidity and deformity of the fingers, thumb
and wrist were reduced, and dexterity of the fingers attained.
8D: Postoperatively on electromyography, hyperactivity of the
extensors and flexors were reduced.
Fig. 9
Fig. 9: Electromyography of normal hand
The extensor digitorum communis and flexor digitorum
superficialis are acting separately and reciprocally, in
swing and stance phases.
From these facts, it is proved clinically that the monoarticular
muscles such as interossei and flexor pollicis brevis are closely
related to voluntary movements while the multiarticular muscles are
not related to voluntary and fine movements.41,42
The biceps brachii and the brachialis muscles also coexist in
the upper arms. The monoarticular brachialis is considered to be an
antigravity elbow flexor whereas the multiarticular biceps brachii
is considered to be a body-propelling elbow-flexor and hyperactive
in cerebral plasy. In the triceps brachii, the monoarticular medial
and lateral heads are considered to be antigravity, whereas the
biarticular long head is considered to be a body-propelling
elbow-extensor and hyperactive in cerebral palsy. Similarly,
selective release of the multiarticular biceps brachii and triceps
brachii was done to control spasticity and rigidity and to restore
dexterity of the elbow (Fig. 66AB, 69AB, 72AB). Stability and
dexterity of the elbow were restored and the hypothesis can be
considered to be reliable.42,61
In the trunk, the monoarticular short rotatores and
multiarticular longissimus thoracis and iliocostalis are co-existing.
The short rotatores can be identified as antigravity muscles while
the longissimus thoracis and iliocostalis can also be identified as
non-antigravity propelling muscles. Clinically for correction of
scoliosis, hyperactive muscles namely the multiarticular
longissimus thoracis and iliocostalis were totally sectioned as they
were contributing factors. Clinically, the deformity was corrected
and there was no loss of stability after release of these
multiarticular muscles (Fig. 128AB, 129AB). The upright posture
of the spine did not collapse at all. Here, also, the short
monoarticular muscles could be proved to be antigravity muscles.
35,43,61
Functional differences between the multiarticular and
monoarticular muscles can be observed in the process of
phylogenetic development. In the fish, there are few small
monoarticular muscles; hence, there is very little antigravity activity.
Only small monoarticular muscles are developed around the back
and in the abdominal fins. In amphibians, most of the muscles in
the whole body are still multiarticular, but the monoarticular
muscles have gradually been differentiated around the spine and
extremities. Hence, antigravity ability to keep the body prone in
water and waterfront developed. In reptiles, the monoarticular
muscles have developed considerably, and so sufficient antigravity
activities to crawl on the ground have been obtained. In mammals,
the monoarticular muscles are well developed and accordingly,
sufficient antigravity activities to run and raise the trunk away
from the ground developed. Thus, it is considered that antigravity
ability of the vertebral body developed, in accordance with
development of the monoarticular muscles (Fig.10).35,61
When we analyze the article "The vertebrate Body, edited by
Romer," we can notice the fact that the monoarticular muscles
have developed gradually, according to phylogenetic development.
We could conclude that the monoarticular muscles have gradually
differentiated and developed from the multiarticular muscles in the
process of development.44
Fig.10: Development of antigravity muscles
At amphibian level, multiarticular muscles are well
developed. According to phylogenetic development,
long and short monooartiicular muscles have developed
and more elaborate antigravity posture have been
accomplished in reptiles, mammals and primates.
Functional difference between the monoarticular
and multiarticular muscles can also be shown in electromyographic
studies. In our electromyographic study of the triceps surae, a
difference in activities between the gastrocnemius and soleus is
clearly demonstrated. The gastrocnemius is active only in
accelerating phases called terminal stance and heel-off phase in
which mostly the propelling force acts, whereas the soleus is active
both in the antigravity supporting phase called mid-stance phase
and accelerating phase of heel-off (Fig. 11).35,61 Thus, the soleus
is considered to act to support the body at the stance phase during
which antigravity activities are needed.
Fig.11.Electromyelographic difference between gastrocnemiu and soleus
The gastrocnemius acts, in the end of stance phase and push-off phase (accelerating phase). This muscle is considered to be an accelerating (propelling) muscle. The soleus acts in the whole stance phase as well as in the push-off phase. This muscle is considered to act in the supporting phase of the body during gait. Thus, the gastrocnemius can be considered a propelling muscle wheras the soleus can be considered an antigravity muscle with function of body support. Electromyographically, careful observation discloses much evidence that the short monoarticular muscles have antigravity activities which support the body upright against gravity while the long multiarticular muscles have propulsive activities which propel the body forwards and don't have antigravity activities. In Fig. 12, you can see that short monoarticular vastus medialis and soleus act to support the body at semiflexed antigravity posture, but long biarticular rectus femoris and gastrocnemius do not do so. On the contrary at the propulsive extension of the heel-off position in the same joints, both these monoarticular and biarticular muscles act together without any significant difference (Fig.12). These differences between the two muscles on electromyography clearly demonstrate that the short monoarticular muscles are body supporting antigravity muscles while the long multiarticular muscles are body propelling muscles.
Fig.12 Differences of antigravity activities between the
monooarticular and multiarticular muscles
in crouched standing posture
In the knee flexed position, antigravity activities are
most essential to prevent collapse of the joint in the hips, knees
and ankle. Here, in this position, the monoarticular vastus
medialis and soleus are mostly functioning, whereas the
multiarticular rectus femoris and gastrocnemius are less
active. These finding are evidences which prove that the
monoarticular muscles are antigravity muscles related to
body-supporting activities.
Thus, accumulation of these clinical, motor developmental,
motor-functional and electromyographic analyses has provided us
the basis for broadening the scope of OSSCS.
Paralysis of the monoarticular muscles and hypertonicity of
multiarticular muscles in cerebral palsy
In the previous clause, we presented the observation that
hypertonicity in cerebral palsy is caused by hyperactivity of the
multiarticular muscles such as the gracilis and psoas. We also
proposed a concept that the monoarticular muscles are the
body-supporting (antigravity) muscles. Furthermore, we present
another hypothesis that monoarticular muscles with antigravity
activities are paralyzed or weakened in cerebral palsy depending
on the extent of cerebral damage resulting in damage of antigravity
activities such as standing and kneeling. This hypothesis can be
applied to understand the cause of equinus deformity in cerebral
palsy. The weakness of the monoarticular dorsiflexors such as the
tibialis anterior and peroneus brevis and tertius are factors causing
equinus deformity. This equinus makes weight-bearing base of the
foot narrow and consequently induces instability. Another
important aspect of equinus deformity is that the antigravity soleus
is paralyzed and weakened. Although paralysis and weakness of the
soleus cannot be directly measured, this can however be clearly
demonstrated by the difficulty in keeping the body in an upright
posture such as standing, sitting and kneeling. Instability in
equinus deformity can be caused by the weakness of the soleus as
well as by narrowing of the weight-bearing base in the feet.
These hypotheses could also be used to understand the factors
that contribute to the crouched posture. The monoarticular
extensors such as the gluteus maximus and adductor magnus are
paralyzed, or weakened and this paralysis or weakness
consequently results in a crouched posture. Hence, the crouched
posture is caused both by hypertonicity of the multiarticular
muscles such as psoas and rectus femoris and by concomitant
paralysis or weakness of the antigravity monoarticular extensors
such as the gluteus maximus and adductor magnus.
In flexion deformity of the fingers, the multiarticular flexors
such as flexor digitorum profundus and superficialis are hypertonic,
inducing a grasping deformity as in crawling locomotion (Fig. 8AB,
69AB, 73AB, 75AB). On the other hand, the monoarticular
muscles such as the interossei that are antigravity and participate in
fine movement of the fingers are paralyzed. Therefore, the intrinsic
minus hand with hyperextension of the MP joint becomes
predominant (Fig. 8A, 73A, 75A, 79A).41 In these situations, the
most important concern is how to facilitate the antigravity
activities of these weakened monoarticular muscles.
Inhibition of antigravity activities of the monoarticular muscles,
by hypertonicity of the antagonistic multiarticular muscles
The most interesting finding in muscular activity in cerebral
palsy is that antigravity activities of the monoarticular muscles are
mostly depressed by hypertonicity of the antagonistic
multiarticular muscles. In flexion deformity of the hip, antigravity
activities of the gluteus maximus are markedly decreased by
hypertonicity of the antagonistic psoas and rectus femoris, resulting
in weakness of the gluteus maximus (Fig.2A, 3A, 5A, 6A, 87A,
95A). In adduction deformity of the hip, activities of the abductors
such as the gluteus medius and minimus are also depressed by
hypertonicity of the antagonistic adductors such as the gracilis,
semitendinosus and semimembranosus, thereby weakening the
gluteus medius and minimus (Fig. 2A, 3A, 5A, 6A, 13A, 22A).
In equinus deformity, antigravity activities of the tibialis
anterior are depressed by hypertonicity of the gastrocnemius and
other plantar flexors. Hence, weakness of the antagonistic tibialis
anterior is induced (Fig. 3A, 6A, 23A, 24A, 99A, 107A, 120A).
Thus, it becomes rather obvious that hypertonicity of the
multiarticular muscles not only causes hypertonic postures and
deformities, but also weakens the antagonistic monoarticular
muscles.
So, we proposed another working concept that antigravity
and voluntary activity of the monoarticular muscles can easily be
depressed by hyperactivity of the multiarticular antagonists. On
the basis of this concept, we could find a possible path to
facilitate activity of these monoarticular muscles with appropriate
releases of these multiarticular antagonist muscles (Fig. 3AB, 6AB,
23AB, 24AB, 71AB, 73AB, 75AB, 99AB, 107AB, 120AB,
124AB, 128AB, 141AB).30,35,40,41,45,61
Hypertonicity in the monoarticular muscles
We have confirmed that hypertonicity in cerebral palsy is
basically caused by hyperactivity of the multiarticular muscles.
However, clinically, the monoarticular muscles with significant
hypertonicity are co-existing. Now, let us take the adductor longus
muscle as an example. From our working concept, the adductor
longus can be considered an antigravity muscle. Clinically,
when the adductor longus was totally sectioned in the diplegic
patients, deterioration in ambulatory gait and serious instability
resulted even though the adductor brevis was preserved. If the
preoperative condition was unstable, instability became more
predominant (Fig. 2AB). Therefore, it seems essential to preserve
the antigravity activities of these muscles to secure an excellent
result in these ambulatory patients (Fig. 3AB)
However, it is also true that if we preserve this muscle
completely in severely paralyzed patients with scissors posture,
adequate correction cannot be achieved because of hypertonicity of
this muscle. Even in the monoarticular adductor longus, the muscle
fibers could also be hypertonic. So, to reduce hypertonicity of this
muscle, similarity of the hyperactive behaviors of monoarticular
and multiarticular muscles observed were considered.
The adductor longus is a unipennate muscle which arises from the
linea aspera on the posterior aspect of the femur and is attached to the
pubic bone. Each muscle fiber is arranged regularly from the
proximal short muscles fibers with no tendons to the distal long
muscle with long tendon fibers. Morphologically, the muscle fibers
with long tendon fibers arises from most distal portion of the femur
whereas the muscle fibers with short or no tendon fibers arises from
most proximal part of the femur. So, it is observed that even in the
same adductor longus muscle, muscle fibers with long tendon fibers
and the muscle fibers with short tendon or no tendon fibers co-exist
and are distributed regularly according to the length of the tendon
fibers (Fig. 4).
Functionally, the muscle fibers arising from proximal part of
the femur with no tendon fibers or shorter tendon fibers can be
considered to be the muscle fibers with more antigravity activities.
It has more similarity to the muscle fibers of the adductor brevis in
muscle length and in function. On the other hand, the muscle fibers
arising from the distal part of the femur with longer tendon fibers can
be considered to be the muscle fibers with more propulsive and
less antigravity activities. It has also more similarity in length and
function to that of the gracilis. Based on the observation that
multiarticular muscles are propulsive and more hyperactive in
cerebral palsy and short muscles with short or no tendon such as
monoarticular muscles are antigravity and less hyperactive, it can
be concluded that the long muscle fibers with long tendon fibers
are more hyperactive whereas the short muscle fibers with no or
short tendon fibers are less hyperactive and have more antigravity
activities (Fig. 4). Clinically, this hypothesis could be useful. In
patients with mild or moderate adduction deformity of the hip
in the ambulatory level, the muscle fibers with long tendon of the
adductor longus should be selectively released with intramuscular
lengthening and hyperactivity of the long muscle fiber with long
tendon fibers could be selectively reduced (Fig. 4). If hyperactivity of
the adductor longus was selectively relieved in this way,
antigravity activities of the short monoarticular muscle fibers could
be preserved and stability in standing will not be disturbed (Fig. 3B,
6B). We should avoid total section of the adductor longus in the
patients with potential of independent or crutch ambulation,
because this will destroy the antigravity stability of the muscles.
We could also see similar functional differences in
hyperactivity between the long muscles fibers with tendon fubers and
short muscle fibers without tendon fibers in the other monoarticular
muscles such as the adductor pollicis, flexor pollicis brevis, interossei,
brachialis, soleus and iliacus (Fig. 8AB, 73AB, 87AB, 107AB).
When the muscle fibers with tendon are sectioned with intramuscular
tenotomy, hyperactivity is lessened but stability and fine motor skills
will be preserved due to the unreleased short muscle fibers in these
muscles (Fig.8C).41,61 From these clinical observations, we could
confirm that in one muscle belly, muscle fibers with various lengths
are regularly differentiated and distributed in the form of unipennate
or bipennate muscles.
Now, we could conclude that the antigravity and propulsive
activities are different in each fiber and depend on its length and
form. When we apply this conclusion for treatment, we will be
able to control the spasticity and athetosis appropriately even in
monoarticular muscles by selectively releasing the tendon of the
long muscle fibers and preserving muscle fibers without tendon
fibers.
We have now progressed to a new level where we can
understand that hypertonicity in the cerebral palsy can be basically
caused not only by hyperactivity of the multiarticular muscles, but
also by hyperactivity of the long monoarticular muscles with long
tendon fibers. At the surgery, tendinous portion of the long
monoarticular muscles can also be selectively released by the use
of intramuscular tenotomy.30,35,41,61
Propulsive activity versus antigravity activity
From all these various observations, it can be concluded that
antigravity activity is a mechanism to support and keep the body in
an upright posture. Here, the body supporting activity can be
called antigravity activity. It has been already mentioned that
antigravity activities are brought about by combined activities of
the monoarticular muscles such as the adductor brevis and longus,
iliacus, gluteus maximus, medius and minimus, soleus, deltoid,
brachialis and flexor pollicis brevis. We also noted the fact that
muscle fibers with more antigravity activity and ones with less
antigravity activity characteristic are distributed regularly in
unipennate and bipennate muscles. It can be understood that this
antigravity activity is reserved in the vertebrate animals to increase
the efficiency of the propulsive activities on the ground. It also
seems logical to consider that this antigravity mechanism has
developed along with the maturation of the central nervous system.
Propulsive activity is another important mechanism that
propels the body forwards. This has been vital for the survival of
species, providing opportunities for the vertebrate animal in search
of their food.
The human being is a vertebrate animal having two fundamental
movements: Propulsive movements and antigravity movements
(Fig.1AB, 7AB, 10, 11, 12). Cerebral palsy is a condition in
which the antigravity muscles are paralyzed with disturbance in
antigravity activities. It is also a condition in which the propulsive
muscles are affected with hypertonicity on both flexor and extensor
sides with inhibition of reciprocal and alternate propulsive
movements (Fig. 1C).
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