GROWTH HOLDS THE BASICS
Growth is a major factor that should be taken into account in scoliosis. Growth in childhood and growth in the pubertal period both have a major influence on the evolution of spinal curvature. The analysis of the growth parameters (yearly rate of increase in standing and sitting height and bone age) allows adjusting and planning one's strategy prospectively in case of severe deformities. Growth is characterized by changes in rhythm. It includes phases of acceleration and deceleration that must be accounted for. Puberty is the turning point during which the curvature of scoliosis will be emphasized. It begins insidiously. It is very important to identify its first signs early and to anticipate the curvatures that are going to develop.
BIOMETRIC MEASUREMENTS (FIGS. 1, 2)
Looking beyond racial diversity, there are growth constants (ie, stages through which every child must pass regardless of chronologic age) that are the same in all ethnic groups. A few simple tools are required at the time of the consultation: a height gauge, scales, a metric tape, and a bone age atlas. With these tools, the specialist will be able to perform a rapid mental arithmetic and reach a reasonable decision. A few simple questions will guide the orthopaedist.1–6 (Table 1).
Examining the child at every 6 months, with 1 of the 2 checkups being preferably around his or her birthday, allows an easy assessment of the growth velocity of the child and the different body segments. Growth velocity is an excellent example and provides the best indicator of the beginning of puberty, on which so many decisions rest.
The first sign of puberty is an increase in the growth rate of the standing height to greater than 0.5 cm per month or greater than 6 cm per year.
The height gauge is to the orthopaedic specialist what the stethoscope is to the cardiologist. At 2 years of age, the standing height is approximately 50% of the adult height; at 5 years it is approximately 60%; and by the age of 9 years it is approximately 80%. Standing height is a global marker and consists of 2 specific measurements such as subischial height (ie, the growth of the lower limbs) and sitting height (ie, the growth of the trunk). These 2 different regions often grow at different rates at different times, which is valuable information for decisions in orthopaedics.5–10
The sitting height averages 34 cm at birth, and averages 88 cm for girls for a standing height of 1.65 cm and 92 cm for boys at the end of growth for a standard height of 1.75 cm. In patients with scoliosis, it can be instructive to follow the changes in the sitting height rather than in the standing height. The measurement of sitting height can also be useful in anticipating the onset of puberty. In an average population, puberty starts at approximately 75 cm of sitting height in girls and at approximately 78 cm in boys. When the sitting height is approximately 84 cm, 80% of girls have menarche.
Children should always be weighed at each consultation. There may be striking morphologic changes from 1 year to the next. Growth is a volumetric revolution. The gain is 5 kg by year during puberty. The weight is 20 kg at 5 years and 30 kg at 10 years.
Note that weight doubles between 10 and 17 years of age. At 5 years of age, the child's weight reaches 32% of the final normal weight 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.
PUBERTY IS A TURNING POINT (FIGS. 3–5)
Puberty is a vague concept for many physicians. Each one has their own landmarks and references, and a very intuitive notion of the chronology of events. In contrast, the children must be followed up very precisely during this key period. There are many misunderstandings. Sexual characteristics are often misscored, menarche is unpredictable, and the notion of age is equivocal: which age do we mean? bone age or chronologic age? A great deal of discipline is required to avoid confusion.
Measurements must be repeated at regular intervals. The onset of puberty is not a sudden event starting at some exact H-hour. There is an incubation phase and then a gradual onset. It is the responsibility of the physician to recognize when the pace of the system changes.
Two indicators that provide starting signals are:7–9
- The swelling of the testis in boys and of the breast in girls;
- The increase in growth rate, particularly that of sitting height, which doubles or triples over a few months. The pubertal cycle is the same regardless of ethnic origin. It follows a stereotypic course. Puberty starts at a bone age of 11 years in girls and 13 years in boys. This bone age is marked by the appearance of the sesamoid bone of the thumb on left hand radiographs and the fusion of the 2 bone nuclei of the olecranon in the elbow.
The first 2 years are a time of strong acceleration. The last 3 years are a period of pubertal deceleration. Elbow closure is on the dividing line between the acceleration and deceleration phases.
Pubertal deceleration is also gradual: the yearly growth rate decreases. This reduction in the pace of the system must also be recognized, based on the decrease in the sitting height (and therefore standing height): increased rate over a period of 6 months, closure of the elbow, fusion of the distal phalanges of the hand, and then ossification of the iliac crest a few months later (these are Risser signs).
PUBERTAL DIAGRAM AND THE PEAK HEIGHT VELOCITY (FIGS. 3–5)
Puberty starts at 13 years (bone age). At the beginning of puberty the remaining growth at the standing height is about 22.5 cm: it is 12.5 cm in sitting height and 10 cm in subischial leg length. The remaining growth in standing height is approximately 14%. The multiplying factor is 1.14. The trunk grows more than the lower limbs.
The ascending side for boys (acceleration phase6–21) lasts from 13 to 15 years of bone age. This period corresponds to peak growth. It is not a single point. It lasts for 2 years. For boys, during this period, the gain in standing height is 16.5 cm. The gain in sitting height is ±8.5 cm. The gain in subischial length is 8 cm. The triradiate cartilage closes 1 year after the onset of puberty and the ascending phase is approximately 14 years of bone age.
The descending side (deceleration phase) is characterized by a steady decrease in velocity of annual growth. It lasts 3 years from 15 to 18 years. The remaining growth in standing height is approximately 6 cm: 4.1 cm in sitting height and 1.9 cm in subischial length. During this phase, the trunk grows more than the lower limb, which stops growing at Risser 1 (Fig. 3).
Puberty starts at 11 years bone age. At the beginning of puberty the average remaining growth in standing height is approximately 20.5 cm. The gain in the sitting height is approximately 11.5 cm. The gain in subischial length is approximately 9 cm. The remaining standing height is approximately 13%. The multiplying factor is 1.13.
The ascending phase (acceleration phase6–21) starts from 11 to 13 years of bone age. The peak growth lasts for 2 years. During this phase the gain in standing height is 15.1 cm (±1 cm); in sitting height it is 7.7 cm (±0.5 cm), and in subischial height it is 7.4 cm (±0.5 cm). The triradiate cartilage closes 1 year after the beginning of puberty, at approximately 12 years of bone age.
The descending phase (deceleration phase) is characterized by steady decrease in the annual velocity of growth. It lasts for 3 years, from 13 to 16 years. The remaining growth is approximately 5.4 cm in standing height with 3.8 cm in sitting height and 1.6 cm in subischial length. The lower limb stops going after menarche. This equals our Risser 1. Menarche occurs on the descending side of puberty: 42% of the girls experience menarche before Risser 1; 31% at Risser 1; 13% at Risser 2; 8% at Risser 3; 5% at Risser 4. After 2 years of menarche, there is usually no more growth (Fig. 4). During the pubertal period, the average gain in weight each year is approximately 5 kg. The bigger is the child, the less effective is the brace.
THORACIC GROWTH IS THE FOURTH DIMENSION OF THE SPINE (FIGS. 6, 7)
Puberty is characterized by a dramatic change in stature, by a change in the proportions of the upper and lower body segments, and by the development of secondary sexual characteristics. Puberty is a juxtaposition of 3 micropeaks (Fig. 6).
- The first peak occurs in the lower limbs;
- The second peak occurs in the trunk;
- The third peak occurs in the thorax just after Risser 1.
At birth the volume of the thorax is approximately 6%. At 5 years, it is 30%. At 10 years, it is 50% (Fig. 7). The anteroposterior diameter is approximately 21% of sitting height. The transversal diameter makes up 30% of sitting height. The thoracic perimeter is approximately 93% of sitting height. In treating scoliosis, the morphology of the thorax must be considered.1–5,22 The thorax grows significantly during puberty. This involvement must not be underestimated. The spurt in thoracic growth accompanies the deformity, is submitted to its action, and aggravates it.
ESTIMATION OF SKELETAL MATURITY (FIGS. 8, 9)
Personal data indicate that approximately 50% of children have a bone age that is significantly different from their chronologic age.1–20,22–25 Decision making should be based on annual growth velocity (pubertal diagram), Tanner sign, and bone age.
On the ascending side of puberty, the elbow is wide open (Risser 0) (Fig. 8). Elbow maturation is more precise than hand maturation. The olecranon method is very useful (Figs. 9, 10).6
- At the very beginning;
- At 11.4 years of age for girls and 13 years for boys, there are 2 ossification centers on the olecranon;
- At 11.5 years of bone age for girls and 13.5 years for boys, the 2 ossification centers fuse to give a semilunar shape;
- At 12 years of bone age for girls and 14 years for boys, the olecranon is rectangular;
- At 12.5 years of bone age for girls and 11.5 years for boys, the Please confirm the age for the boys.olecranon begins to fuse;
- At 13 years of bone age for girls and 15 years for boys, the olecranon is completely fused.
The Risser 0 covers the first two thirds of the pubertal growth. This period is critical because of the evolution of the curve. 1–18,22,25 (Fig. 10).
On the descending side of puberty, the elbow closes. Risser 1 appears 6 months after elbow closure:
- Risser 1 heralds the beginning of the descending slope of the pubertal growth velocity diagram. It generally appears after elbow closure, when the epiphyses of the distal phalanges (II, III, IV, and V) of the hand fuse. The rate of growth in sitting height and standing height decreases abruptly. Axillary hair generally appear during this period;
- Risser 2 corresponds to a bone age of 14 years in girls and 16 years in boys. It generally appears when the greater trochanteric apophysis unites with the femur. When the proximal phalangeal epiphyses fuse in the hand, there is approximately 3 cm left to grow in sitting height and there is no more growth of the lower limb;
- Risser 3 corresponds to bone ages of 14.5 years in girls and 16.5 years in boys. The phalangeal epiphyses of P1 and P2 fuse during this period, the greater trochanter is closed, and 1 year of growth and an increase of 2 cm in sitting height still remain;
- Risser 4 corresponds to a bone age of 15 years in girls and 17 years in boys. The distal epiphysis of the ulna is united to the shaft. At this stage, the remaining growth in sitting height is 1 cm;
- Risser 5 is very much like Risser 0: it is a long period that does not provide much information to the dinician. The distal radial epiphysis generally fuses around Risser 5. The iliac apophysis may fuse at the age of 22 or 23 years, but in some cases it never fuses.
Regardless of the method of its determination, bone age is meaningless as an isolated parameter. It should be constantly measured against chronologic age, the rate of annual growth in standing height, and secondary sexual characteristics.
The pubertal diagram can be divided into 4 zones (Fig. 11).
First zone: Ascending side, triradiate cartilage open, bone age between 11 and 13 years in girls and between 13 and 15 years in boys (Risser 0).
Second zone: Ascending side, triradiate cartilage closed, bone age between 11 and 13 years in girls and between 13 and 15 years in boys (Risser 0).
Third zone: Descending side, elbow closed but greater trochanter not fused, bone age between 13 and 16 years in girls and between 15 and 18 years in boys (Risser 1–2).
Fourth zone: Descending side, elbow closed and greater trochanter fused, bone age between 13 and 16 years in girls and between 15 and 18 years in boys (Risser 3 to 4; Fig. 11).
On the ascending side of puberty, olecranon evaluation is more precise than the hand; on the descending side of puberty, the Risser sign must be completed by the hand maturation.
SCOLIOSIS AND PUBERTY (FIG. 12)
Sitting height plays an essential part in the treatment of scoliosis; unfortunately, it is not recorded often enough. Gain in sitting height always needs to be compared with the angular development of the spine.17 The basic question is: how much has the child grown in a year and how much has the scoliosis worsened in a year. This question 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. If, in contrast, it is accompanied by a deterioration of angulation, the treatment needs to be reconsidered.
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 y bone age in girls and from 13 to 15 y bone age in boys) (Figs. 12, 13).
Any spinal curve increasing by 1 degree each month (12 degrees/year) during the ascending phase of the pubertal growth diagram is likely to be a progressive curve that will require treatment.18,24,25
Any curve that increases by 0.5 degree each month during this phase must be monitored closely.
Any curve that increases by less than 0.5 degree each month during this phase can be considered mild (Figs. 12, 13).
The evolutive risk must be assessed in all cases of scoliosis. It is proportional to the growth and initial angulation. An angle of 20 degrees is frightening at the age of 5 years, preoccupying at the onset of puberty, but reassuring at the end of puberty. Aggressive scoliosis must be detected as early as possible.15,24
- A curve of 20 degrees at the onset of puberty has a surgical risk of 16%.1–15,22,24,25
- A curve of 20 to 30 degrees at the onset of puberty has a surgical risk of 75%.1–15,22,24,25
- A curve of 30 degrees at the onset of puberty has a surgical risk of 100%.
On the ascending side of puberty the first 2 years are crucial:
- If the annual curve progression is less than 6 degrees/year, 33% are high candidates for surgery24;
- If the progression is between 6 and 10 degrees/year, the rate becomes 71%24;
- If the progression is greater than 10 degrees/year, the rate becomes 100%.24
The risk of scoliosis decreases on the descending phase of the puberty growth diagram:15
- Risser 1 (13.6 y of bone age in girls and 15.6 y 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;
- Risser 2 (14 y of bone age in girls and 16 y of 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;
- Risser 3 (14.6 y of bone age in girls and 16.6 y of bone age in boys): There is a 12% risk of a curve of 20 degrees or greater progression by 5 degrees or more;
- Risser 4 (15 y of bone age in girls and 17 y of bone age in boys): The risk of the progression of scoliosis is markedly decreased, although for boys, a slight risk remains;
- Risser 5 (16 y of bone age in girls and 18 y of bone age in boys): It would be futile, if not naive, to wait until the iliac crest is completely ossified, before discontinuing the treatment of scoliosis. But there is still a risk of worsening in boys who have idiopathic scoliosis between Risser 4 and 5.1–12,22–26
THE CRANKSHAFT PHENOMENOM: MYTH OR REALITY?
This effect may be summarized as follows: the best procedure for fusion is one that sterelises or neutralises or freeze all the posterior and anterior growth cartilages. Posterior fusion is a partial vertebral fusion that may cause a crankshaft phenomenon when performed in immature children. Sanders 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 crankshaft effect was observed in those patients who still had an open triradiate cartilage in the pelvis.18,19 The crankshaft effect obviously decreases as puberty progresses. The risk of crankshaft phenomenon is low if the spine curvature is 0 degree.3
WHAT WILL BE THE DEFICIT ON THE TRUNK IF PERIVERTEBRAL ARTHRODESIS IS PERFORMED AT THE BEGINNING OF PUBERTY6
The remaining growth on the thoracic spine is 3.6 cm for girls and 3.9 cm for boys. The remaining growth of the lumbar spine is 2.1 cm for girls and 2.3 cm for boys. The deficit on the trunk will be balanced by the correction of the deformity. The risk of the crankshaft phenomenon is low if the spine curvature is reduced to 0 degree.3
LESSONS LEARNED FROM GROWTH
To control growth, annual growth velocity, skeletal maturation, and Tanner signs must be considered. The measurement of standing height is too approximate to provide an accurate insight into the growth of a scoliotic child.5,6 The measurement of sitting height is much more precise. The mistake is to stick to 1 parameter. Risser 0 covers two thirds of the pubertal period. The pubertal diagram is useful for the adaptation of the strategy. The surgical risk must be appreciated. At the beginning of puberty, a curve of 30 degrees has a 100% surgical risk. If progression is greater than 10 degrees/year on the ascending side of puberty, the surgical risk is 100%.
When treating scoliosis on the ascending side of puberty (crucial period), during Risser 0, 2 important parameters must be observed: the olecranon morphologic changes6 and the progression velocity of the annual curve.
Aggressive scoliosis must be treated by anticipation (not post hoc). Finding out things after they have occurred is the worst outcome that can occur. The damage done during puberty is too often discovered after several months. The potential evolution of the spinal curvature must be assessed at the beginning of puberty.
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