CHAPTER 1
Typical Growth and Motor Development
• Typical growth and maturation of a child’s musculoskeletal system and development of motor skills are determined by numerous factors, including genetics, nutrition, hormones, illness, physical activity, social conditions, race, culture, and geographic location.
• This chapter describes typical growth and maturation of the pediatric musculoskeletal system; typical patterns of motor skill development; and methods of evaluating growth, maturation, and development and identifying anomalies and concerns.
Somatic Growth
• Somatic growth refers to the increase in weight, height, and organ size.
— Assess somatic growth by comparing a child’s height and weight to a population of other children at the same chronological age (CA). For children younger than 24 months, use growth charts developed by the World Health Organization (WHO). From 2 years to 20 years, growth can be assessed using Centers for Disease Control and Prevention (CDC) growth charts.
— These charts include the range of height, weight, head circumference, and body mass index (BMI) obtained from different populations of children.
— WHO growth charts use data from an international cohort of breastfed children obtained in the first 2 years after birth.
— CDC growth charts include data from a sample of children in the United States aged birth to 20 years.
— While frequently used as a marker of health and nutritional status, somatic growth is not a reliable indicator of biological maturity. There is significant individual variation in the timing (when the growth spurt occurs) and tempo (rate or speed at which growth spurt occurs) of growth.
• Growth rate varies with age: it is greatest from birth to 2 years, declines during childhood, and briefly increases again during the adolescent growth spurt (Table 1-1, Figure 1-1).
• During the prepubertal stage between 6 and 12 years of age, growth averages 3 to 3.5 kg and 6 cm per year, with minimal difference between boys and girls (Figure 1-1).
Table 1-1. Rates of Growth in Weight and Height by Age
Adapted from Behrman RE, Kliegman RM, Jenson HB, eds. Nelson Textbook of Pediatrics. 17th ed. Philadelphia, PA: WB Saunders Co; 2004:35, with permission from Elsevier.
Figure 1-1. Stature for age and weight for age for girls (A) and boys (B).
ADOLESCENT GROWTH SPURT
• The adolescent growth spurt begins at about 9 to 10 years of age for girls and 11 to 12 years of age for boys.
— Boys experience a growth spurt about 2 years after the onset of puberty, heralded by the onset of gonadal enlargement.
— Girls experience a growth spurt as soon as 6 months after the appearance of breast buds.
— The growth spurt starts peripherally with enlargement of the hands and feet, then progresses centrally to the arms and legs, and lastly the trunk.
— The peak growth rate occurs earlier for trunk length and later for leg length compared with stature; thus, the late childhood growth spurt is characterized by rapid trunk growth and the early adolescent growth spurt is characterized by rapid growth of the legs.
HEIGHT
• The rate of height growth accelerates until it reaches a maximum, termed the peak height velocity (PHV), which occurs about 2 years after the start of the adolescent growth spurt.
• The growth spurt lasts anywhere from 24 to 36 months (Figure 1-2).
• Standard deviations of age at PHV range from 0.7 to 1.2 years, indicating significant individual variation in the timing of the growth spurt.
• Age at PHV is a reliable indicator of somatic maturity in boys and girls.
• Boys reach PHV at an average age of 14 years at a rate of 10.3 cm (4.3″) per year and then decelerate to a stop by age 18 years.
• Girls reach PHV at an average age of 12 years at a rate of 9 cm (3.8″) per year and stop growing approximately 2 years earlier than boys (usually by age 16 years).
• The onset of menses generally follows PHV by 1 year and is associated with a rapid deceleration in growth and limited additional gains in stature (Figure 1-2).
• PHV and magnitude of height gained is 3 to 5 cm greater in boys than in girls.
• Girls achieve a final mean adult height of 163.8 cm compared with 176.8 cm for boys, for an average adult height difference of 13 cm between men and women. This difference in final adult stature is because of the smaller PHV and the earlier termination of growth in girls compared with boys.
• Pubertal growth accounts for almost 25% of final adult height.
• The genetic contribution to final adult height is approximately 60%.
Figure 1-2. Summary of pubertal development in girls (A) and boys (B). Menarche generally occurs shortly after peak height velocity is attained.
From Rosen DS. Physiologic growth and development during adolescence. Pediatr Rev. 2004;25(6):194–200.
• There is a trend for youth who attain PHV at an earlier age to be slightly taller at that age, but ultimately there seems to be no relationship between age at PHV and final adult stature.
• Children who mature earlier generally have a higher PHV than those who mature late, and late maturers on average are taller when the growth spurt begins; consequently, the mean adult height of early and late maturers is usually the same.
• Height differences among boys with differences in age of pubertal onset will generally disappear by late adolescence.
• Similarly, children with constitutional growth delay will “catch up” with their peers by late adolescence.
ESTIMATING ADULT HEIGHT
• Mid-parental height is a frequently used method to estimate a child’s genetic height potential based on the child’s sex and the biological parents’ height, with a standard deviation of approximately 2 inches.
— Mid-parental height for boys = paternal height + maternal height + 5 (inches)/2
— Mid-parental height for girls = paternal height + maternal height − 5 (inches)/2
• Multiplier method
— Height at given CA (cm) × multiplier = adult height (Table 1-2, Table 1-3)
Table 1-2. Height Multiplier Table for Boys
Abbreviation: M, multiplier.
From Paley J, Talor J, Levin A, Bhave A, Paley D, Herzenberg JE. The multiplier method for prediction of adult height. J Pediatr Orthop. 2004;24:732–737 (https://journals.lww.com/pedorthopaedics/Abstract/2004/11000/The_Multiplier_Method_for_Prediction_of_Adult.25.aspx). Reprinted with permission from Wolters Kluwer and the Pediatric Orthopaedic Society of North America.
Table 1-3. Height Multiplier Table for Girls
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