Growth in Pediatric Orthopaedics

The height gauge is to the orthopaedic specialist what the stethoscope is to the cardiologist (2,3).
In children younger than 5 years, standing height is measured with the
child lying down because in this age group this position is both easier
and more reliable (18).

Between birth and maturity, the body will grow by
approximately 1.20 meters (m), or even 1.30 m. Growth is brisk up to
the age of 5 years. After that, it slows considerably until the onset
of puberty, which occurs at approximately 11 years in girls and 13
years in boys. At 2 years of age, the standing height is approximately
50% of the adult height, at 5 years of age it is approximately 60%, by
the age of 9 years approximately 80%, and at puberty approximately 86%.
In this latter period, standing height increases more rapidly.

Standing height is a global marker and is composed of two specific measurements known as subischial height (i.e., the growth of the lower limbs) and sitting height (i.e., the growth of the trunk) (10,18).
These two different regions often grow at different rates at different
times, which is valuable information for decisions in orthopaedics.
Values for the standing heights of girls and boys at various ages are
given in Tables 2.1 and 2.2. The percentages of standing and sitting heights attained at various ages are given in Tables 2.3 and 2.4.

In children younger than 2 years, the sitting height is
measured with the child lying down for the same reasons that the
standing height is also measured supine in this age group (10,18) (Fig. 2.1).
After the age of 2 years, the child to be measured should be placed on
a stool or table at a convenient height. The most important
consideration of all is that the child should always be measured under
the same conditions using the same measuring instruments. The sitting
height averages 34 cm at birth, and averages 88 cm for girls and 92 cm
for boys at the end of growth.

In patients with scoliosis, it can be instructive to
follow the changes in the sitting height rather than in the standing
height (10,34). If a
6-year-old girl with juvenile scoliosis is being treated, her sitting
height will be approximately 64 cm and will increase to about 88 cm.
Therefore the orthopaedist will have to control the spinal curve while
her trunk grows 24 cm. The measurement of sitting height can also be
useful in anticipating the onset of puberty (10).
In an average population, puberty starts at approximately 75 cm sitting
height in girls and at approximately 78 cm in boys. When the sitting
height is approximately 84 cm, 80% of girls have menarche (2,3,10,35).

The segment of the body consisting of the legs is
measured to determine the subischial leg length. As implied by the
name, subischial limb length is measured by subtracting the sitting
height from the standing height (18).

At birth, the subischial leg length averages 18 cm. At
the completion of growth, it will average 81 cm in boys and 74.5 cm in
girls. This 63 cm of growth in boys and 56.5 cm of growth in girls
contributes a far greater percentage of growth in height than does
trunk growth (18). This accounts for the changing proportions of the body during growth (Fig. 2.2).

The measurement of arm span provides an indirect control
parameter for the measurement of standing height. Combining these two
measurements avoids virtually all errors. To measure arm span, the
patient simply raises the arms to a horizontal position, and the
distance between the tips of the middle fingers is measured with a tape
measure (36,37). There is an excellent correlation between

arm span and standing height—standing height is about 97% of arm span (36).
In 77% of healthy children, arm span will be 0 to 5 cm greater than
standing height; in 22%, it will be 5 to 10 cm greater; and in 1%, it
will be greater by 10 cm or more. This relationship persists throughout
puberty, with arm span tending to be slightly greater in proportion to
standing height in boys than in girls. If the trunk is normal (i.e.,
without deformity), its length will equal approximately 52% of arm
span, and the lower limbs will be equal to approximately 48%, or will
be the same as their proportions in the standing height (2,3).

The relation of arm span to normal height is useful in
determining what the normal height of a child who is in a wheelchair
would be; this allows the calculation of the child’s height and weight (31,32,33,36).
It is routinely used for any child who has a spine deformity (e.g.,
scoliosis) for calculating the normal values for pulmonary function.
This relation is also useful in diagnosing certain disorders
characterized by a disproportion between the limbs and the trunk, for
example, Marfan syndrome, in which arm span is usually 5 cm greater
than standing height. In children with spinal deformity, arm span is a

good estimate of what standing height would be if there were no scoliosis.

Weight should always be brought into the equation when
making a surgical decision, whether one is dealing with a case of
idiopathic scoliosis, paralytic scoliosis, or lower limb osteotomy.
Children should always be weighed at consultations (2,3,7,15,16,18,19).
There may be striking morphologic changes from one year to the next. If
weight evaluation becomes an integral part of each consultation,
changes will become obvious and can be incorporated into the
orthopaedic specialist’s deliberations. A simple trend

in the increase in a boy’s weight is 18 to 20 kg at 5 years of age; 30 kg at 10 years of age; and 60 kg at 17 years of age (2,3).
Note that weight doubles between 10 and 17 years of age. At 5 years of
age, the child’s weight has reached 32% of the final normal weight (2,3,18) yet only 48% of the final normal weight is achieved at 10 years of age.

In a patient whose weight is 10% or more above normal, a
scoliosis brace may no longer correct the spinal curve as it did
before. Excess weight of 10% or more may also induce symptoms in a hip
deformed by Perthes disease or limit a child’s ability to walk or run.
A low weight, on the other hand, can explain the delay in the onset of

menarche
because girls generally need to attain a weight of 40 kg for menarche
to occur. If a patient’s excess weight or obesity aggravates an
orthopaedic condition, it is useful to have objective measurements to
document the problem for the patient and his or her parents. A
generally accepted estimate of body fat is expressed in Quetelet body
mass index (BMI): weight (kg)/height(m²) (37). Using this index, 20 to 25 kg per m² is normal, 25 to 30 kg per m² is moderate obesity, 30 to 40 kg per m² is major obesity, and more than 40 kg per m² is morbid obesity.

The BMI is increased in slipped capital femoral epiphysis (38); obesity is a risk factor in Legg-Perthes-Calvé disease.

Hall (19), Garn (39), Lefort (40), and Canepa and Stella (41)
outlined the concept of the “multiplying coefficient,” which can be
applied to growth measurements in children at any age. This has also
been described by Payle et al. (42). It is easy
to calculate this coefficient, which is obtained by considering the
percentage of growth that has been attained. For example, once a child
has reached 40% of his or her expected adult standing height, the
multiplying coefficient can be calculated as 100/40 = 2.5 The
multiplying coefficient can be applied to all biometric data—standing
height, sitting height, subischial leg length, and length of the femur,
tibia, humerus, radius, and ulna (Tables 2.3 and 2.4).

Growth starts before birth. During the first trimester
of gestation, the systems are busy organizing themselves and are
developing at a brisk pace (43,44,45,46).
During this period, the fetus makes daily progress, so that when the
infant is born, it has reached a weight six million times that of the
original egg. By the second month of life, the sitting height is
increasing at a rate of 1 millimeter (mm) daily, which subsequently
increases to 1.5 mm per day. Were this rate of growth to continue until
the age of 10 years, the child would ultimately stand 6 m tall (2,3).

From the third month onward, the embryo becomes a fetus
and turns into a miniature adult. At the end of the second trimester of
gestation, the fetus has reached 70% of its expected length at birth
(it measures 30 cm at this stage) but has achieved no more than 20% of
the expected birth weight (it weighs approximately 800 grams [g]).
During the third trimester, the fetus gains weight at the highest rate
(700 g per month). This means that various stages of

growth do not occur simultaneously during intrauterine life. Length increases steadily and rapidly during the first 6 months in utero, whereas weight gain is most rapid during the final 3 months of gestation (Fig. 2.2).

With high-resolution ultrasonography, it is possible to
follow the growth of the fetus and to detect even the slightest
abnormality (47,48). It
can be anticipated that many orthopaedic conditions characterized by
disproportionate or abnormal growth will be diagnosed prenatally.

Birth marks a very obvious transition in the growth of
the child. After birth, not only does the overall rate of growth vary
at different ages, but the rates at which various segments of the body
grow also differ. For example, during the first 5 years of life,
sitting height and subischial leg length increase at about the same
rate; from age 5 years to puberty, the sitting height accounts for one
third of the gain and the subischial leg length accounts for two
thirds; from puberty to maturity, the ratio is reversed, with the
sitting height accounting for two thirds of the gain in height and the
subischial leg length accounting for one third (Figs. 2-3 and 2-4).
The extent of increase in sitting height and subischial leg length for
boys and girls of various ages are shown in Figures 2.5 and 2.6.

At birth, the standing height of the neonate (50 to 54
cm) is 30% of the final height. By the age of 5 years, the standing
height increases to 108 cm, which is double the birth height and 62% of
the final height. The first year of life sees particularly vigorous
growth rates, with the infant’s height increasing by 22 cm (2,3).
This means that the height gain during a single year is as great as it
is during the entire surge of puberty. After the age of 1 year, the
growth rate starts to slow down but remains strong, with the infant
growing another 11 cm between 1 and 2 years of age, and 7 cm between 3
and 4 years of age (2,3).

At birth, the sitting height of the neonate is
approximately 34 cm, which is roughly two thirds of the standing height
and 37% of the final sitting height. By the age

of
5 years, the sitting height increases to 60 cm, approximately 66% of
the final sitting height, with only another 26 to 30 cm to grow (10,49).
This information is useful in anticipating the effects of deformity and
the consequences of arthrodesis in spinal deformity in young patients (10).

Growth in the subischial leg length follows a pattern
almost identical to that of sitting height. At birth, the lower limbs
are relatively short (only 18 cm) compared to the trunk. By the age of
5 years, the subischial leg length measures 45 cm (a gain of 27 cm),
representing about 60% of the final length. After age 5 years, the
subischial leg length increases by approximately another 35 cm in boys
and 29 cm in girls, before growth ceases; this is a considerable amount
of growth but less than what occurred in the first 5 years (2,3). These figures indicate a need for great caution whenever predictions are being made concerning inequality of limb length.

During the first 5 years of growth after birth, the
proportions change. The cephalic end of the body becomes relatively
smaller, whereas the subischial leg length increases (Figs. 2-3 and 2-4).
It is now readily appreciated why any congenital limb deformity or
chondrodystrophy has such a dramatic onset during this period of rapid
growth. Similarly, any limb paralysis occurring during the first years
of life will usually result in severe shortening, not only because so
much growth remains but also because the ill effects of the paralysis
are felt the most when growth is expected to be extremely rapid.

During this period, growth is not only a vertical
phenomenon but also a volumetric one. At birth, weight is between 3000
and 3500 g, which is 5% of the final figure.

At
5 years, the weight averages 18 to 20 kg, which is 32% of the final
adult weight. In 5 years, the weight gain is 15 to 17 kg. Birth weight
triples in a single year and quadruples by the age of 3 years.

The circumference of the chest is 32 cm at birth but increases by 25 cm to reach 57 cm by the age of 5 years (2,3,10,49).
Chest morphology has undergone dramatic changes. The most precious
growth is the neurologic growth: the head circumference is 35 cm at
birth and increases by 12 cm in the first year, reflecting the growth
of the nervous system. Head circumference should be measured at every
physical examination during the first 2 years after birth and twice a
year up to 5 years. Any neurologic assault on the infant during this
period can have serious effects on neurologic development.

Between 5 years of age and the onset of puberty (11
years of bone age in girls and 13 years of bone age in boys), there is
a marked deceleration in growth, with standing height increasing at
approximately 5.5 cm per year (Figs. 2-3 and 2-4). About two thirds of this growth (3.2 cm) occurs in the lower limb and about one third (2.3 cm) occurs in the sitting height (10).
The trunk is now growing at a slower rate, whereas the lower limbs are
growing faster than the trunk, thereby altering the proportions of the
body (Fig. 2.2). During this period, in boys,
standing height will increase by 27% (approximately 44 cm), sitting
height by 20% (approximately 18 cm), and subischial leg length by 32%
(approximately 26 cm); in girls, standing height will increase by 22%
(approximately 34 cm), sitting height by 17% (approximately 14 cm), and
subischial leg length by 28% (approximately 20 cm) (Figs. 2-5 and 2-6).

At the beginning of puberty, approximately 22.5 cm of
growth remains to be attained in standing height (12.5 cm in sitting
height and 10 cm in lower limb) in the case of boys and 20.5 cm (11.5
cm in sitting height and 9 cm in lower limb) in the case of girls. From
age 5 years to the beginning of puberty, the average weight gain is
about 2.5 kg per year (Figs. 2-5 and 2-6).
At 10 years of age, the weight represents about 50% of the final
weight. In contrast, the standing height at this age is 78% of the
final standing height in the case of boys and 83% in the case of girls (2,3,15,16,17,19).

Chronologic age is a poor indicator of puberty. We may
start anticipating puberty at the age of 10 years in girls and 12 years
in boys. The acceleration in growth velocity best characterizes the
beginning of puberty. From a clinical viewpoint, puberty will be
recognized by a combination of factors other than growth: sexual
development, chronologic age, and bone age. After the age of 11 years,
the growth patterns of boys and girls proceed differently. On average,
girls will experience the onset of puberty at 11 years (bone age), and
boys at 13 years (bone age). Puberty and its accompanying rapid growth
is a period of great importance to the orthopaedic surgeon. It is
therefore important to recognize the period just before puberty (2,3,12,13,15,16,17,18,19,21,34,50,51,52,53,54).

There are four main characteristics that dominate the phase of growth called puberty:

During puberty (from 11 to 15 years in girls and from 13
to 17 years in boys) there is a dramatic increase in the growth rate.
However, during this period, the growth is far more noticeable in the
trunk than in the lower limbs: two thirds of the growth goes toward
increasing sitting height and only one third is toward increasing
subischial leg length.

It is during this period that boys overtake girls in
height. On average, boys are between 12 and 15 cm taller than girls.
This is accounted for by two factors. First, boys have approximately 2
years of growth more than girls. Second, boys have a slightly greater
increase in the rate of growth during puberty than girls do, accounting
for approximately 2 cm of additional height.

During puberty, the standing height increases by
approximately 1 cm per month. At the onset of puberty, boys have 13%
(±1%) of their remaining standing height to grow. This is approximately
22.5cm (±1cm) made up of 12.5 cm in sitting height and 10 cm in
subischial leg length. Girls have 12% (±1%) of their standing height to
grow. This is approximately 20.5cm (±1cm) made up of 11.5 cm in sitting
height and 9 cm in subischial leg length.

The peak velocity of growth during puberty occurs
between 13 and 15 years of bone age in boys and between 11 and 13 years
of bone age in girls (2,3,6,18,37,50,51,53).
After bone age 13 years in girls and 15 years in boys, there is a
considerable decrease in the annual velocity of height gain (Figs. 2.3, 2.4, 2.5 and 2.6).
The lower limbs stop growing rapidly; the total remaining growth is 5.5
cm, about 4 cm in the sitting height and about 1.5 cm in the lower
limb. This variation in growth velocity is an extremely important
factor to consider in the treatment of many disorders, especially
scoliosis and limb-length discrepancy.

These figures, ratios, and rates provide only a partial
view of the growth phenomenon. Precise evaluation of the
characteristics of puberty, using the bone age assessment, the Tanner
classification, the onset of menstruation, the Risser sign, and the
annual height velocity, is something that needs to be undertaken with a
great deal of care and consideration. One of the major problems with
using only the onset of menarche and the Risser sign is that they occur
after the growth associated with puberty has begun to slow (3).

Secondary sexual characteristics develop throughout the
course of puberty; the first appearance of pubic hair, the budding of
the nipples, and the swelling of the testes are the first physical
signs to signal the onset of puberty (2,3,18,50,51). The first physical sign of puberty in boys, testicular growth in 77% (37),
occurs, on average, 1.7 years before the peak height velocity and 3.5
years before attaining adult height. The bone age will be approximately
13 years at the onset of puberty; the Risser sign is 0 and the
triradiate cartilage is open.

The first physical sign of puberty in girls, breast budding in 93%, occurs about 1 year before peak height velocity (37).
This averages 11 years in bone age. The Risser sign is still 0, and the
triradiate cartilage is still open at the onset of puberty. Menarche
occurs about 2 years after breast budding, and final height is usually
achieved 2.5 to 3 years after menarche. After menarche, girls will gain
the final 5% of their standing height, about 3 to 5 cm (10,35,54). The appearance of axillary hair, although variable, occurs after the peak of the pubertal growth diagram.

The secondary sexual characteristics generally develop in harmony with bone age, but there are discrepancies in 10% of cases (2,3,6,10,18,37).
Puberty may be accelerated and growth can end more quickly than usual,
catching the unwary physician off guard. In fact, it has been
demonstrated that it is not uncommon to see an acceleration of the bone
age during puberty (37).

Using all of these landmarks, it is possible to draw a diagram relating the events occurring during puberty (Figs. 2-5 and 2-6).
Even if one indicator is missing or does not match the other, it is
still possible to have a good idea of where the child is on his or her
own path through puberty (2,3,10).
By plotting the gains in standing height and sitting height every 6
months, a picture of the period of puberty is developed. It is also
easy to divide this into two parts. The first phase (i.e., the
ascending limb of the growth velocity curve) is characterized by an
increase in the velocity of growth and is the major portion of the
pubertal growth spurt. The second phase (i.e., the descending phase of
the growth velocity curve) is characterized by a slowing of the rate of
growth (2,3,10).

The first phase of the pubertal growth spurt is the
ascending phase, which corresponds to the acceleration in the velocity
of growth. This phase lasts 2 years, from approximately 11 to 13 years
of bone age in girls and from 13 to 15 years of bone age in boys. The
gain in standing height in girls during this phase is about 15.1 cm,
made up of 7.7 cm in sitting height and 7.4 cm in subischial leg
length. The gain in standing height in boys during this phase is about
16.5 cm, made up of 8.5 cm in sitting height and 8 cm in subischial leg
length. During this first phase of the pubertal growth spurt, the
increase in sitting height contributes 53% and the increase in
subischial leg length contributes 47%. Therefore, more growth comes
from the trunk than from the legs during this phase of growth (10).
The peak height velocity occurs on the ascending side of the growth
velocity curve. It does not occur at just one point on the curve but
takes place during 2 years. It can be roughly identified by accurate
assessment of standing height and sitting height at 6-month intervals.

Triradiate cartilage closure occurs about halfway up the
ascending phase of the pubertal growth velocity diagram. This closure
corresponds to an approximate bone age of 12 years in girls and 14
years in boys. After closure of the triradiate cartilage, there is
still a considerable amount of growth remaining: greater than 12 cm of
standing height in girls and more than 14 cm in boys (3).

The second phase of the pubertal growth spurt is the
descending side, which corresponds to the deceleration in the velocity
of growth. The closure of the elbow (discussed in subsequent text)
divides the ascending and descending phases of puberty (10).
The descending phase lasts 3 years, from 13 to 16 years of bone age in
girls and from 15 to 18 years of bone age in boys. During this phase,
both boys and girls will gain about 6 cm in standing height, with 4.5
cm attained from an increase in sitting height and 1.5 cm attained from
an increase in subischial leg length. During this phase, the increase
in sitting height contributes 80% of the gain in the standing height (10).

Menarche usually occurs after closure of the olecranon
apophysis, on the descending phase of the growth curve, when the rate
of growth is slowing. This decrease in the rate of growth is usually
between bone ages of 13 and 13.5 years and corresponds to Risser sign I
on the iliac apophysis (34,35,55,56,57).
After this stage, the average girl will gain an additional 4 cm of
sitting height and 0.6 cm of subischial leg length. The menarche is not
as precise as many other indicators during puberty. Forty-two percent
of girls experience menarche before Risser I, 31% at Risser I, 13% at
Risser II, 8% at Risser III, and 5% at Risser IV (7).

The descending phase of puberty is characterized by significant growth of the thorax.

During puberty, the peak growth is a combination of
three micropeaks: the first peak involves the lower limb at the very
beginning of this period, and the second peak involves the trunk (these
two peaks are on the ascending phase of the growth velocity curve); the
third peak involves growth of the thorax and occurs during the
descending phase of the curve (Fig. 2.7).

At skeletal maturity, the final standing height is about 175cm (±6.6 cm) for boys and about 166cm (±6 cm) for girls.

Puberty is characterized by a great increase in weight.
At the beginning of puberty, the average weight is 40 kg for boys and
33 kg for girls. At skeletal maturity, the average weight for boys is
65 kg (a gain of 25 kg) and the average weight for girls is 56 kg (a
gain of 23 kg). During the growth spurt of puberty, the average gain in
weight each year is 5 kg (2).

Measurement of sitting height provides an indirect
indication of spinal growth. The spine makes up 60% of the sitting
height, whereas the head represents 20%, and the pelvis represents 20% (9,10,77).
If we accept the fact that there are at least three growth zones per
vertebra (sometimes four), the resulting morphology of the spinal
column is

the
product of 100 growth plates. The pattern of growth in the posterior
arch, where closure is linked, in particular, to the presence of the
neural stem, differs from that seen in the body of the vertebra, which
behaves like a long bone (9,10,23,78).

If one were to compare any of the vertebrae of a
newborn, one would find very little morphologic variation between them.
The process by which cervical, thoracic, and lumbar vertebrae acquire
their individual identities is gradual. In the vertebral body,
ossification first appears in the dorsal region; from this hub, the
process of ossification radiates to the cranial and caudal parts of the
spine. The process of ossification is extremely slow, and does not
finish until the 25th year of life.

At birth, the lumbosacral vertebrae are relatively
smaller than the thoracic and cervical vertebrae. However, during the
first years of growth, they grow more rapidly. Between 3 and 15 years
of age, the lumbar vertebrae and their discs increase in size by about
2 mm per year, whereas the thoracic vertebrae and their discs increase
by 1 mm.

The
discs account for approximately 30% of the height of the spinal segment
at birth. At maturity, this proportion decreases to 25%, with the discs
constituting 22% of the cervical spine, 18% of the thoracic spine, and
35% of the lumbar spine (9,10).

The anterior and posterior portions of the vertebrae do
not grow at the same rate. In the thoracic region, the posterior
components grow at a faster pace than their anterior counterparts. The
reverse occurs in the lumbar region. Growth potential therefore varies
from one level to the next, differing from anterior to posterior. In
addition, as the vertebrae develop, there is a constant remodeling of
the anatomic organization of the spine; for example, the articular
apophyses change in both morphology and direction (10,29).

The length of the spine will nearly triple between birth
and adulthood. At birth, the vertebral column is approximately 24 cm
long. In the newborn, only 30% of the spine is ossified. There is
little substantial difference in morphology between one vertebra and
another. The length of a thoracic

vertebra is about 7.6 mm and that of a lumbar vertebra is about 8 mm (9,10).
The average adult spine is approximately 70 cm long in men, with the
cervical spine measuring 12 cm, the thoracic spine 28 cm, the lumbar
spine 18 cm, and the sacrum 12 cm. The average female spine is
approximately 65 cm long at maturity.

At birth, the cervical spine measures 3.7 cm; it will
grow about 9 cm, to reach the adult length of 12 to 13 cm. The length
of the cervical spine will nearly double by 6 years of age. It will
gain an additional 3.5 cm during the pubertal growth spurt. The
cervical spine represents 22% of the C1-S1 segment and 15% to 16% of
sitting height (9,10).

The diameter of the cervical spinal canal varies with
location, typically decreasing in width from C1 to C7 or from C1 to C3,
and then widening slightly. These differences are important in the
clinical setting because the room available for the spinal cord can be
very consequential. It should be remembered that, regardless of the
size of the child (e.g., in dwarfing conditions), the spinal cord will
attain the usual adult diameter. The average width of the cervical cord
is 13.2 mm, and the average anteroposterior depth is 7.7 mm (9,10).
Therefore, the transverse and sagittal diameters of the cervical canal
are important. In the adult, at C3, the normal transverse diameter is
27 mm and the average sagittal diameter is approximately 19 mm (9,10).

The T1-S1 segment is very important because the most
frequent disorders of the spine during growth originate in this
segment. The T1-S1 segment measures about 19 cm at birth, and 45 cm at
the end of growth in the average man and 42 to 43 cm in the average
woman (9,10,77).
This segment makes up 49% of the sitting height at maturity. Knowledge
of the effects of arthrodesis on this segment of the spine requires
precise knowledge of the growth remaining at various ages (7) (Figs. 2.13, 2.14 and 2.15).

The thoracic spine is about 11 cm long at birth and will
reach a length of about 28 cm in boys and 26 cm in girls at the end of
growth. Its length more than doubles between birth and the end of the
growth period. The growth of the

thoracic
segment has a rapid phase from birth to 5 years of age (7 cm), a slower
phase from 5 to 10 years of age (4 cm), and rapid growth through
puberty (7 cm) (9,10).

The T1-T12 segment represents 30% of the sitting height,
so a single thoracic vertebra and its disc represents 2.5% of the
sitting height. By knowing the amount of growth that each vertebra
contributes to the final height, the effect of a circumferential
arthrodesis, which stops all growth in the vertebrae and discs, can be
calculated (Table 2.5).

Posterior arthrodesis results in only one third of this
deficit (2.5% of sitting height for each thoracic vertebra), which is
about 0.8% of the remaining sitting height (Figs. 2.13, 2.14, 2.15 and 2.16).

The thoracic spinal canal is narrower than either the
lumbar or the cervical canals. At the age of 5 years, this canal has
attained its maximum volume, and is wide enough to permit the entry of
the little finger of an adult hand. The average of the transverse and
anteroposterior diameters at T7 is approximately 15 mm (Fig. 2.17).

The L1-L5 lumbar spine is approximately 7 cm in length
at birth, and it grows to approximately 16 cm in men and 15.5 cm in
women. As in the thoracic spine, growth is not linear: there is rapid
growth from 0 to 5 years of age (gain of about 3 cm); slow growth from
5 to 10 years of age (gain of about 2 cm); and rapid growth again from
10 to 18 years of age (gain of about 3 cm). The height of the lumbar
spine doubles between birth and maturity (9,10).

The lumbar spine represents 18% of the sitting height,
and a single lumbar vertebra and its disc account for 3.5% of the
sitting height. Values for the remaining growth of the lumbar segment
at various ages are given in Figures 2.13 and 2.14. A posterior
vertebral arthrodesis results in a

deficit of only one third of this value, that is, slightly more than 1% of the remaining sitting height (9,10).

At the skeletal age of 10 years, the lumbar spine has
reached 90% of its final height but only 60% of its final volume. The
medullar canal in the lumbar spine is wider than that in the thoracic
spine. At skeletal maturity, the dimensions of the canals are such that
the adult thumb can be introduced into the cervical canal, the
forefinger into the thoracic canal, and the thumb into the lumbar
canal. At birth, the spinal cord ends at L3, and at maturity, it ends
between L1 and L2.

The growth of the thorax represents the fourth dimension of the spine (10).
The thoracic circumference is a rough but valuable indicator of this
fourth dimension of spinal growth. The thorax has a circumference of 32
cm at birth, and it will grow 56 cm in boys and 53 cm in girls, that
is, to almost three times its birth size.

In boys, the thoracic circumference is 36% of its final
size at birth, 63% at the age of 5 years, 73% at 10 years, 91% at 15
years, and 100% at 18 years. From birth to the age of 5 years, the
thoracic circumference grows exponentially and increases by 24 cm. From
the ages of 5 to 10 years, the increase is slower; the thoracic
circumference is 66 cm at the age of 10 years, which means that its
growth is only 10 cm in 5 years. At that stage, it is at 73% of its
final dimension. Another spurt occurs between the ages of 10 and 18
years, particularly during puberty. The thoracic circumference then
increases by 23 cm, that is, as much as between birth and 5 years.

The thoracic circumference measures approximately 96% of the sitting height (10).
These two measures do not grow simultaneously, especially during
puberty. At age 10 years, the thoracic circumference is at 74% of its
final size, whereas the sitting height is almost at 80% of the expected
measurement at the end of growth.

The transverse and anteroposterior diameters, which can
be measured with obstetrical calipers, are two more parameters to
assess the growth of the thorax. At the end of growth, the thorax has
an anteroposterior diameter of about 21 cm in boys and 17 cm in girls;
that is, it has increased by 9 cm since birth. The transverse diameter
is 28 cm in boys and 24 cm in girls at the end of growth; that is, it
has increased by 14 cm since birth. The transversal diameter makes up
30% of the sitting height and the anteroposterior diameter constitutes
20%. The sum of the measurements of the transverse and anteroposterior
diameters of the thorax should equal 50% or more of the sitting height (10).

The thoracic volume makes up 6% at birth, 30% at the age
of 5 years, and 50% at 10 years. It doubles between the age of 10 years
and skeletal maturity. Extensive thoracic congenital scoliosis
associated with fused ribs may affect thoracic growth and function and
may have an adverse effect on the development of the lungs.
Constrictive tridimensional deformities of the thorax may cause
restrictive lung disease. Campbell proposed that severe congenital
scoliosis with segmental hypoplasia of the hemithorax and fused ribs
may be treated by opening wedge thoracostomy with the use of a
chest-wall distractor (79,80,81,82).

The sitting height plays an essential part in the treatment of scoliosis (10);
unfortunately, it is not recorded often enough. Gain in sitting height
always needs to be compared with angular development of the spine (10,12).
This relation is all that is needed for the proper assessment of
treatment efficacy. If the increase in sitting height is accompanied by
stable angulation, the treatment is definitely working well (10,12,34). If, on the other hand, it is accompanied by deterioration of angulation, the treatment needs to be reconsidered.

When we treat scoliosis, we must also think of growth.
In congenital scoliosis, the intrauterine growth and that occurring in
the first few years of life can reveal a great deal about the future
behavior of the spinal curvature (49). In
idiopathic infantile and juvenile scoliosis, the growth during the
first 10 years of life can be very important and may give clues to the
behavior of the spinal curvature during the

pubertal growth spurt (10,34).
However, in adolescent idiopathic scoliosis, the most common form of
scoliosis, there is no such information available before the spine
begins to curve in puberty. The ultimate outcome of the curve will be
determined during the pubertal growth spurt. Therefore, monitoring the
behavior of the spinal curve during this short and decisive period
gives the only clues to its natural history. To detect these clues, it
is necessary to know the onset of puberty (10).

The natural history of the curve of the spine can be
judged on the ascending side of the pubertal growth velocity diagram
corresponding to the first 2 years of puberty (from 11 to 13 years bone
age in girls and from 13 to 15 years bone age in boys) (10).
Any spinal curve increasing by 1 degree each month (12 degrees per
year) during the ascending phase of the pubertal growth diagram is
likely to be a progressive curve that will require treatment. Any curve
that increases by 0.5 degree each month during this phase must be
monitored closely, whereas a curve that increases by less than 0.5
degree each month during this phase can be considered mild (10).
This observation of the natural history of the spinal curve during the
early part of puberty gives information about the behavior of the curve
during the last phase of puberty, as growth is slowing, and thereby
gives guidance about the frequency of follow-up visits and the duration
of bracing.

It is therefore clear that scoliotic risk evaluation
plays an essential role in the treatment of the disease. During the
ascending phase of the pubertal growth diagram a 5-degree curve is
associated with a 10% risk of progression, a 10-degree curve represents
a 20% risk, a 20-degree curve carries a 30% risk, and a 30-degree curve
raises the risk to virtually 100% (10,83,84).

The risk of scoliosis decreases on the descending phase of the puberty growth diagram (85).
At Risser I (13.6 years of bone age in girls and 15.6 years of bone age
in boys), there is a 10% risk of progression for an angulation of 20
degrees and a 60% risk for a 30-degree curve.

At Risser II (14 years bone age in girls and 16 years
bone age in boys), there is still a 30% risk of progression (5 degrees
or more) for a 30-degree curve and a 2% risk for a 20-degree curve (64).
At Risser III (14.6 years bone age in girls and 16.6 years bone age in
boys), there is a 12% risk of a curve of 20 degrees or greater
progressing by 5 degrees or more (10). At
Risser IV (15 years bone age in girls and 17 years bone age in boys),
the risk of the progression of scoliosis is markedly decreased,
although, for boys, a slight risk remains (83,84,85,86).
At Risser V (16 years bone age in girls and 18 years bone age in boys),
it would be futile, if not naïve, to wait until the iliac crest is
completely ossified, before discontinuing the treatment of scoliosis (64) (Fig. 2.18).

However imprecise and approximate the Risser sign may
be, it is widely used as a deciding factor in many reports of brace
treatment or surgery. Nevertheless, its limitations must be understood.
The data of the studies by Lonstein et al. (83) and Pedriolle (85),
relating Risser sign and the curve magnitude, have been discussed. As
was pointed out in the preceding text, because two thirds of the
pubertal growth spurt occurs before the appearance of Risser I, and
because of the often ambiguous relation between Risser stage and bone
age, its value in both clinical decision making and research should be
questioned. Bone age, the growth rate, and secondary sexual
characteristics are the most reliable parameters. Risser stages must
not be regarded as a first-choice indicator; they must always be
compared with bone age (Greulich and Pyle atlas), especially when
making decisions that will have major consequences, such as ordering or
removing a brace or scheduling vertebral fusion (10).

Evaluation of the vertebral ring apophyses has been recommended by Blount (87), and rib epiphysis by Hoppenfeld et al. (88)
as other ways to judge the remaining growth of the spine and therefore
the risk of progression of the curve. Although there may be some value
in these radiologic signs, it is important to know that in some
patients these apophyses may not close until after 20 years of age (64).

Theoretically, treatment for scoliosis should be stopped when growth is complete.

Evaluation of growth completion should be based on the
rate of annual growth rather than on radiologic signs. In cases where
annual growth rate is less than 2 cm per year, the end of growth is
imminent (89,90). This
parameter is far more precise than Risser V. It is considered that 3.5
years after the peak growth period in puberty and 2 years after the
onset of menstruation, there is virtually no risk of progression of
scoliosis, and growth is completed.

A question that is asked frequently by parents, and
considered by physicians, is by how much will a spinal fusion for
scoliosis decrease the final height of the child (Table 2.5)?
To determine the answer to this question, the surgeon needs to know the
remaining growth in sitting height and the contribution to that height
made by the vertebrae that will be fused (10,91).
After a bone age of 13 years in girls, when there is only 3.8 cm of
future growth in sitting height, and a bone age of 15 years in boys,
when there is only 4.1 cm of remaining growth in sitting height, there
is little need for concern about final height. Figures 2.13 and 2.14
show the growth remaining in the spine at various ages; the effects of
arthrodesis at these ages can be calculated (Figs. 2-15 and 2-16).

However, arthrodesis for deformity is often required
before these ages. Faced with deformity in a developing spine, the
specialist may be best advised to carry out a vertebral arthrodesis to
prevent progression of a severe deformity (92).
It may be better to have a short spine that is straight than to have a
longer but crooked spine with the same sitting height (91).
In addition, the vertebrae in many cases of congenital scoliosis will
not grow normally, and therefore arthrodesis of these vertebrae does
not alter the height as much as it would in a normal spine. Arthrodesis
of six thoracic vertebral bodies, at the age of 5 years, will result in
an approximately 4-cm deficit in sitting height.

The crankshaft effect on the spine, after arthrodesis for scoliosis, was described by Dubousset et al. (93).
The crankshaft phenomenon occurs when there is a solid posterior
arthrodesis, with sufficient anterior growth remaining to produce a
rotation of the spine and trunk with progression of the spinal curve.
Therefore, it is very important for the surgeon to consider the state
of skeletal maturity and the amount of growth remaining in the portion
of the spine that is to be fused (94,95).

Roberto et al. (96) reviewed 86
immature patients who underwent posterior arthrodesis at Risser 0 or I.
They found that in 72% of the patients the curve progressed less than
10 degrees, in 21% of them it progressed by 11 to 15 degrees, and in
seven patients it progressed by more than 16 degrees. Patients in
Tanner stage I, with open triradiate cartilage, had the greatest
increase in the curve, and the crankshaft phenomenon decreased with
greater maturity.

Sanders et al. (97) performed a
retrospective study of posterior spinal instrumentation with fusion in
43 patients with idiopathic scoliosis, who were at Risser 0 at the time
of surgery. The triradiate cartilage was open in 23 patients and closed
in 20 patients. The crankshaft effect was observed in 10 of the 23
patients with open triradiate cartilage, and in 1 patient with closed
triradiate cartilage.

However, after closure of the triradiate cartilage there
is still a significant amount of growth remaining, that is, greater
than 12 cm of standing height for girls and more than 14 cm for boys.

These studies emphasize the problem with using only one
factor in determining the remaining growth of the spine, which is a
difficult thing to do at best. The studies also emphasize the fact
that, for much of the decision making required in the treatment of
scoliosis, the Risser sign is not a reliable parameter because so much
of the spinal growth occurs before Risser I; Tanner signs, bone age,
and annual growth rate are more precise.

There is still a risk of crankshaft phenomenon on the
descending phase of the puberty growth diagram after elbow closure. The
last spurt of puberty predominantly involves the growth of the thorax,
which may completely change the evolution of idiopathic scoliosis (10,94).
The growth of the thorax, a largely ignored factor, can explain some of
the incidents of deterioration after initially good surgical results.
In addition, the greater the residual curve, the greater the chance of
significant crankshaft development (10,94).

In paralytic scoliosis, in which the curve is severe or
rapidly progressive, circumferential fusion with segmental
instrumentation is the best strategy to avoid the crankshaft
phenomenon. The greater the magnitude of the curve, the more complex
and hazardous is the surgery, and the more unlikely it is to correct
the curve to 0 degrees. In such cases, there is no reason to wait for
the pubertal spurt (10). Puberty can only
worsen the situation. The deficit in sitting height caused by such
early fusion is largely compensated for by the correction of the curve.
A loss of sitting height by early arthrodesis at 10 years of age is not
important for the patient who will live, at least most of the time, in
a wheelchair. At age 5 years, the spinal canal has grown to 95% of its
definitive size; therefore, circumferential arthrodesis will have no
influence on the size of the spinal canal (10).

In congenital scoliosis, the first 5 years of life are the golden period to perform hemiepiphysiodesis (49,98,99). A gain in angulation of 10 to 15 degrees can be obtained for each vertebral segment.

The femur is approximately 9 cm long at birth and will
undergo a fivefold increase in length to approximately 44 cm in girls
and approximately 47 cm in boys by the time growth has finished. Growth
is particularly vigorous during the first 5 years of life, with the
femur doubling in length by 2 years and tripling by the age of 5 years,
at which age it reaches 60% of the final length (multiplying
coefficient of 1.66) (39-42,101).

Between birth and 5 years of age, the femur grows 17
cm(±1 cm) in both girls and boys. From 5 years of age until puberty,
femoral growth slows to a steady rate of less than 2 cm per year,
increasing to more than 2.2 cm during puberty. The proximal femoral
physis of the femur accounts for 30% of the femoral growth, or
approximately 10 cm. The proximal femoral growth plates grow roughly
0.7 cm each year increasing to 0.8 cm per year at puberty. The distal
femoral epiphysis accounts for 70% of the femoral growth or
approximately 24 cm. The distal femoral growth plate grows roughly 1.2
cm each year, increasing to 1.4 cm per year at puberty (104).

The tibia is 7 cm long at birth, and grows at a slower
rate than the femur. By the time the tibia has stopped growing, it will
be about 34 cm long in girls and 37 cm long in boys, having also
increased practically fivefold in length. By the age of 2 years, the
tibia will have nearly doubled its length, it will have tripled its
length by age 5 years and it will have reached, at this time, about 60%
of its final length (multiplying coefficient of 1.66). The tibial and
femoral growth profiles are almost identical, with vigorous growth
during the first 5 years of life, which then slows to about 1.3 cm each
year until puberty, when growth increases to 1.6 cm per year.

The proximal tibial physis accounts for about 60% of the
length of the tibia, or about 16 cm in girls and 18 cm in boys. Growth
occurs at a rate of roughly 0.9 cm per year. The proximal physis grows
about 0.7 cm each year from age 5 years until puberty, when it
increases to 1 cm per year. The distal tibial physis grows slower and
accounts for about 40% of growth potential, equivalent to 11 cm in
girls and 12 cm in boys. The distal physis grows about 0.5 cm from age
5 years until puberty, when it increases to 0.7 cm per year (100,101,102,103,104).

The growth of the tibia and the fibula are
interdependent, and perfect harmony is necessary. Excessive growth in
the fibula, which happens in cases of achondroplasia, may lead to genu
varum. Similarly, resection of the fibula during growth may result in
ankle valgus. These clinical examples demonstrate how important it is
to restore continuity, length, and growth to either bone if deformity
is to be avoided.

Consideration of the growth of the distal femur and the proximal tibia together illustrates the importance of injury

to both of these growth centers. Any serious injury to the growth
centers around the knee during the early years of life is likely to
result in severe shortening of the lower limb. The knee undergoes the
greatest growth of all. From birth to maturity, the knee grows about
42.5 cm in boys (24 cm for the femur and 18.5 cm for the tibia) and
38.7 cm in girls (22 cm for the femur and 16.7 cm for the tibia). The
knee accounts for two thirds of growth (65%) in the lower limb (37% for
the femur and 28% for the tibia) (100,101,102,103,104).

Stated another way, the knee grows about 2 cm per year
from age 5 to the beginning of puberty, with slightly more than 1 cm of
growth in the femur and slightly less than 1 cm in the tibia. At
puberty, during the ascending phase of the puberty growth diagram, the
knee grows about 2.4 cm per year, with approximately 1.4 cm of growth
in the femur and 1 cm in the tibia. When the growth of the femur and
the tibia are combined, total growth in the lower limb before puberty
averages approximately 3.1 cm per year, increasing to 3.8 cm per year
during puberty.

The length of the foot in relation to the length of the
lower limb is greatest during intrauterine life, and decreases from
birth onward. When the sizes of the fetal foot and the lower limb are
compared, the ratio is 1.41 at 8 weeks, 0.9 at birth, and 0.6 in
adults. At birth, the foot is about 7.5 cm long (i.e., 40% of its final
size). At the end of growth, the foot length is about 24 cm in girls
and 26 cm in boys (6,105). The length of the foot represents 15% of the standing height in both girls and boys at skeletal maturity.

The foot is the first structure of the musculoskeletal system that begins to grow at puberty (6).
The growth spurt of the foot occurs a few months before the start of
puberty. Although it is the first to start growing during puberty, the
foot is also the first musculoskeletal structure to stop growing.
Growth of the foot stops at bone age 12 years in girls and at bone age
14 years in boys (i. e., 3 years before the end of growth) (105). This makes the foot unique among the musculoskeletal structures in that its rate of growth mostly declines during puberty.

When puberty begins, at approximately bone age 11 years
in girls, the foot is already 22 cm long and has only 1.6 cm or 2% of
its growth left. When puberty starts in boys, at approximately bone age
13 years, the foot is about 24 cm long and has 2 cm or 2.5% of its
growth remaining. Therefore, arthrodesis at the beginning of puberty
will have no considerable effect on the length of the foot (106).

When considering limb-length discrepancy, the size and the height of the hind part of the foot must be taken into consideration.

Although there are many methods for predicting
limb-length discrepancies, an understanding of the growth of the limbs
gives the physician important information, both in predicting the
incidence of such discrepancies and in more accurately applying the
information from the various methods (e.g., the Moseley straight-line
graft) (42,102).

Contrary to widespread belief, there is more growth in
the trunk or in sitting height during puberty than there is in the
subischial length or the limbs (2,3).
The growth spurt in the lower limbs occurs during the first year of
puberty, and, after bone age of 13 years in girls and 15 years in boys
(i.e., elbow closure and descending phase of the puberty growth
velocity diagram), the rate of growth of the limbs decreases rapidly (54,107). The growth of the limbs is complete at bone age 13.6 years in girls and 15.6 years in boys (54,107) which corresponds to Risser I. In the Greulich and Pyle atlas (20),
this corresponds to fusion of the distal phalangeal physis of the index
and middle fingers. Limb growth is very brief during puberty, and this
must be taken into account. Epiphysiodesis is all the more effective in
cases where surgery is performed at the very beginning of puberty. The
optimum timing for epiphysiodesis remains a controversial subject. The
main challenge in this procedure is to reduce the margin of error (101,108,109). Decisions must be based on the pubertal diagram with precise evaluation of the bone age (hand and elbow) (Figs. 2.20, 2.21 and 2.22).

When performing an epiphysiodesis at the beginning of
puberty or later, the risk of overcorrection is relatively small. The
amounts of growth remaining at the various growth plates in the lower
extremity are given in Figures 2.21 and 2.22.

With knowledge of the growth of the lower limbs (expressed as a percentage or by using the multiplying coefficient) (39,40,41,42), it is easy to make a quick prediction of limb inequality at skeletal maturity (101). A general rule

for a problem such as congenital short femur is to multiply the
discrepancy at certain ages by a factor; for example, multiply the
discrepancy by 3 at age 1 year, by 2 at age 3 years for girls and 4
years for boys, by 1.5 at age 6 years for girls and 7 years for boys,
and by 1.1 at the beginning of puberty for both boys (13 years of bone
age) and girls (11 years of bone age). Therefore, a boy with a 4-cm
discrepancy at age 4 years will have an 8-cm difference at the end of
growth. At 7 years, a 4-cm discrepancy will increase to 6 cm. At the
onset of puberty, 10% of the growth of the lower limb remains on
average, so the final length discrepancy will be around 4.4 cm (2,3,101).

Such predictions are general and should be used with
caution. For the final decision in complex cases, it is best to use all
of the information possible—standing height, sitting height, annual
growth rate, Hechard–Carlioz chart (110), Moseley chart (102), Lefort residual coefficient (40), and multiplying coefficient (39,40,41,42)—while
considering the bone age in order to lessen the margin of error. The
younger the patient, the higher the risk of inaccurate prediction (111).

All these data are based on the Green and Anderson tables (100). These predictions do not need to be interpreted with mathematical strictness because there is a reasonable margin for error (2,3,111).
Furthermore, these forecasts are best suited to cases of malformation
in which the difference in the rate of growth between the two limbs
remains constant. Other causes of limb-length discrepancy, such as
poliomyelitis, vascular malformation, and chronic arthritis, may not
follow a constant pattern and are more difficult to evaluate (112).

A decision for lengthening versus epiphysiodesis often
depends on the final height of the child. Predicting the final height
before puberty is inexact (26). Approximately
80% of children will remain in the same percentile for height after age
5 years. Tables to make these predictions from bone age are found in
the Greulich and Pyle atlas (20). At the
beginning of puberty, the remaining growth in standing height is about
14% in boys and 13% in girls. The final standing height depends upon
the date of the beginning of puberty and its duration.

The growth pattern is abnormal in many children with
paralytic disorders (e.g., cerebral palsy, spina bifida, and
poliomyelitis). In these children, therefore, it is essential to record
and follow the parameters of growth closely to establish an indication
for surgery with as much accuracy and safety as possible (2,31,32,33,119,120).
There are two problems that make it difficult to measure and evaluate
the parameters of growth in such children. First, contractures and
deformities make morphometric measurements difficult or even
impossible. Second, reference values that pertain to children with
normal growth and development are not applicable to these children.

Nevertheless, it is still possible to gain valuable
information about growth, first by measuring arm span when the child is
in a wheelchair and, second, by scrutinizing the child carefully from
head to foot. The length of even one bone that has been more or less
spared by the deficit could be sufficient to determine the standing
height of the child. For example, after age 8 years, the proportions of
the body segments remain the same; therefore, the length of the femur
represents 28% of standing height, and the length of the tibia and
fibula represents 24% of standing height. For the upper extremities,
the humerus represents 19% of standing height and 36.5% of sitting
height, the radius represents 14.5% and 27.8% of standing and sitting
height, respectively, and the ulna represents 15.5% and 29.5%,
respectively (2,3).

Weight is an important parameter to take into
consideration. Many children, especially those with cerebral palsy and
total body involvement, have a deficit of 20 to 30 kg. Surgical
procedures are not the same for children who weigh 20, 40, and 60 kg.
Being underweight as a result of malnutrition creates a risk of
infection after surgery (121,122,123,124).
There are many parameters that are used to assess nutritional status,
such as measurements of the triceps and the subscapular skinfold, or
determination of the total lymphocyte count. Whichever tests the
surgeon relies on should be carried out on underweight children before
surgery, especially on those children with chronic conditions (125).

On the other hand, obesity can also be a problem in
surgery. The obesity of children with muscular dystrophy or spina
bifida may restrict the choice of surgical approaches and
instrumentation. The gain in weight during puberty is the main enemy of
children with diplegia or ambulatory quadriplegia (2,3,126).

The assessment of bone age is more difficult in paralyzed children. Bone age retardation can be very severe in cerebral palsy (127).
These patients sometimes display a wide range of bone ages, with the
bone age of the hand not matching that of the elbow or the pelvis (this
observation is made from the author’s personal experience). The real
bone age, therefore, must be approximately assessed, and this
information must be correlated with the results of anthropometric
measurements (31,32,33).
These measurements are based on radiographs that measure the bone
length, but they can also be obtained during a clinical examination.
For the tibia, a simple measurement is possible from the medial joint
line of the knee to the inferior rim of the medial malleolus (128).