4 Things of Baby Skull Differnt From Adult

Annu Proc Assoc Adv Automot Med. 1998; 42: 93–113.

An Overview of Anatomical Considerations of Infants and Children in the Developed World of Car Safety Design^§

Abstract

The infant and child differ structurally from the adult in a number of ways which are critical to the design for protection confronting impact forces and for adequate occupant restraint systems. The purpose of this paper is to bring together a contour of the anatomy, anthropometry, growth and development of the baby and child. Age differences related to the proper pattern of child restraint systems are emphasized. Issues discussed include child--adult structural differences, centre of gravity of the body, the head mass in relation to the neck and general body proportions, positions of key organs, and biomechanical properties of tissues.

Introduction

Infants and children are non miniature adults. Trunk size proportions, musculus os and ligamentrus strengths are different and thus occupant packaging for crash protection need special consideration. This newspaper is an overview of pediatric size and proportional differences with considerations of some kid injuries in car crashes along with a review of some biomechanical data.

GROWTH OF THE Babe Torso AS A WHOLE

Growth and development of the human being torso occurs continuously from birth through senesence (old age). Such development is sporadic and non-uniform, yet information technology does not occur haphazardly. For the most part, incremental growth of any dimension or part of the body occurs according to predictable trends. Most trunk dimensions follow trends which involve rapid growth separated past a menstruum of relatively slower or uniform growth. In that location are notable differences in the timing of these incremental growth spurts, for most tissues and organs of the torso collectively reverberate the general body growth. Equally an example, the brain grows rapidly during the catamenia before birth and and then slows considerably during the per-schoolhouse years. At nascency the brain is typically 25% of its adult size, although the torso weight of the newborn is only about 5% of adult weight (Stuart and Stevenson, 1950). Importantly, nearly half of the postnatal growth of the brain volume occurs during the beginning yr of life, and attains about 75% of its adult size by the finish of the second yr. Past dissimilarity, genital organs develop very slowly during this menses but, instead, attain their adult size during the second decade of life.

Subcutaneous tissue (trunk fat) is a body component infrequently considered as a factor in the proper pattern of protective devices for the infant body. This tissue tends to increment apace in thickness during the starting time 9 months following birth, which growth of the body as a whole is much slower. After this period of high incremental change at that place is a menstruation of less rapid growth, and then that by five years of age the thickness of the subcutaneous layer is about one-half the thickness of the nine calendar month old infant.

Loading of the body by strap-blazon restraints must occur in areas where the trunk is strongest, i.e., on solid skeletal elements. In some, the fatty subcutaneous tissue can produce bulges or 'rolls' of flesh in the areas of placement on such restraint straps. Thus, proper positioning of restraint straps on the chubby i–3 yr old may exist difficult to maintain because of the affluence of this fatty tissue.

Changes in body weight similarly follow characteristic age group trends (Krogman, 1960; Krogman and Johnston, 1965; Martin and Thieme, 1954; and Meredith, 1963). From the 10th day after nascence, when the post-birth weight loss is normally regained, at that place is a steady increment in weight so that during the outset three months an average infant gains most two pounds per calendar month, or nearly one ounce per solar day (Krogman 1941). At five months the birth weight has doubled. Beginning at six months, there is only a i pound gain per calendar month in weight and so that the birth weight is tripled at the end of the commencement year and quadrupled at the end of the second. From this time on, the charge per unit of increase in body weight gradually decreases during the 2d year according to a gene of one-half pound per month (Krogman and Johnston, 1965). Later the 2d yr proceeds in weight may become irregular and less predictable on a monthly basis. As a full general pattern, afterwards the 2nd year and until the ninth year there is a five pound almanac increment. Thus, at v years the body weight is six times the birth weight and in the 10th year the weight of the body is x times the birth weight (Krogman, 1960).

Changes in body superlative and body proportions too take specific age trends (Figs. 1–iii). The newborn child is approximately 20 inches in total trunk length. During the outset yr this meridian is increased past approximately ten inches. Until about the seventh year, full torso length should be doubled by the fourth year and tripled by the 13th year. The height of an adult is about twice the height of a ii-year-old child. From the 2d to the 14th year, total body summit increases (in inches) according to the formula: Height=historic period in years × ii.5 + 30 (Weech, 1954).

Percentage distribution of trunk segments every bit related to pre- and postnatal development. (Modified from Salzmann, "Principles of Orthodontics.")

Developmental change in body proportions as seen in directly comparison betwixt the adult and the newborn, child and boyish. (Modified from Chenoweth and Selrick, "Schoolhouse Health Problems.")

Age changes in the ratio betwixt sitting (body) top and full body superlative cannot be disregarded when considering the dynamics of changing body proportions. (Fig. iv). Sitting height represents most 70% of the total height at birth, but falls rapidly to about 57% in the third year. At 13-years of age in girls, and 2 years later on in boys, the ratio of sitting height to total body height is about 50%.

Changes in sitting height from birth to machismo.

Longitudinal growth of limb bones occurs as long as the epiphyseal cartilage prolificates; growth ceases when the cartilage ossifies and fuses to the os segments surrounding it. Since the fusion of epiphyses in the lower extremities occurs earlier in girls than in boys, girls tend to accept a lower 'sitting tiptop-full trunk height' ratio than boys, between eight and 12 years, and a higher one between the 14th and 18th year.

Thus, specially in the early on years of life, the infant is markedly elongating in stature. As well, the postural changes of the infant, from a recumbent one to that of a slouched, upright position, is completed within a relatively brusque menses of time.

In general, children of either sex are of the same height, weight, and general body proportions up to 10 or 11 years of age; however, not infrequently one sees girls slightly taller than their male counterparts fifty-fifty at ages six–10. Girls tend to have an earlier pubertal growth spurt between eleven and 14 years and, in full general, are taller than boys of this age. In the early on to mid-teens, the boys catch up, so surpass the girls in stature (Watson and Lowrey, 1967). These variations in total superlative at the 10–xiv yr age span reflect the differences in sitting height betwixt boys and girls.

At birth the head is ane-quaternary the full body length, whereas in the adult it is one-seventh (Fig. five). Also the trunk is long with the upper limbs beingness longer than the lower limbs. From the second half of the first year to puberty the extremities grow more speedily than the head. At puberty the growth rates of the trunk and limbs are about equal, simply the body continues to grow in length afterwards limb elongation has declined in the boyish period. The mid-point of the body is slightly above the bellybutton (omphalos) in the newborn, and a 2 years the mid-point of the body is slightly below the omphalus; at well-nigh sixteen years, this mid-signal is near the pubic symphysis.

The proportional changes in body segments with age.

The center of gravity of the kid varies according to age, child size, weight, and body form as well as sitting posture. A study by Swearingen and Young (1965), of individuals at ages v, 10, 12, and 18 years, indicated that the center of gravity (CG) cannot be located accurately and precisely in groups of seated children. They found that a plot of the CG would autumn within an asymmetrically ellipsoidal area. In these children it was found that the CG was located vertically on the torso well in a higher place the lap belt level. This high CG in children must exist considered when adult lap belts are used to restrain children, since the greater body mass above the chugalug may cause the child to whip forrad more in the case of an adult. In a subsequent report of infants aged 8 weeks–3 years, it was found that the CG is located even college on the trunk (Young, 1968).

THE Caput

In automotive collisions, the child's head is the body area virtually oft and most seriously involved. In a study of children's injury patterns in 14,520 rural automobile accidents involving 31,925 occupants, it was found that children (nascency through xi years) had a frequency of 77% head injuries (Moore et al, 1959). This was a much greater frequency than either adolescents (69%) or adults (70%) in this written report, although it was found that kid caput injuries were of a more pocket-sized variety than either adolescents or adults. Agran and Winn (1987) identified head injuries in 50% of children, either lap-shoulder belted or unrestrained. Contributing to specific caput impact bug are the large head of the child, the relatively soft, pliable, and elastic basic of the cranial vault, and the fontanelles. As compared with the developed, these features make the head of the child less resistant to bear on trauma. In a standoff, for example, the unrestrained child, because of his large head and high CG, would 'lead with his head'. Crash data covering infants and children up to iv years of age point that 77% of those who were injured in automobile accidents had caput injuries (Kihlberg and Gensler, 1967). The vulnerability to injury of an babe'southward head occurs even prior to birth, every bit has recently been shown in a report of fetal deaths involving restrained and unrestrained pregnant women in machine accidents (Crosby et al, 1968). The reasons for this greater frequency of head injury in children can exist demonstrated both anatomically and biomechanically. The child'southward head is proportionately larger than in the adult (Immature, 1966). (Fig. five). This heavier head mass and resulting college seated CG in immature children, coupled with weaker neck supporting structures, may be, in office, the basis for this higher frequency of head injury.

At birth the facial portion of the caput is smaller than the cranium having a face up-to-cranium ratio of i:8 (cf. adult ratio of i:two.5). Relative to the facial profile, the newborn forehead is high and quite bulged, due to the massive size of the frontal lobe of the brain (Fig. 6). Thus, in the newborn and infant the face is tucked below the massive brain example (Fig. 7). The big head-small confront pattern is noticeable in children even up to ages seven and 8, Vertical growth of the infant face occurs in spurts every bit related to both respiratory needs and tooth eruption. These growth spurts occur during the first half dozen months after birth, during the 3rd and quaternary year, from the 7th to 11th twelvemonth, and again between the 16th and the 19th yr. The commencement growth spurt is chiefly olfactory as associated with the vertical growth of the upper portion of the olfactory organ and nasal crenel. The concluding spurt is related to boyish sexual development.

Soft tissue profile changes of the caput and face up.

Sequential changes of various head and face up regions.

Baby head shape also differs significantly from that of the adult (Fig viii). In the infant the cranium is much more elongate and bulbous, with large frontal and parietal (side) prominences (Fig. eight). At birth the circumference of the caput is nearly 13–14 inches. Information technology increases past 17% during the first 3 months of life, and by 25% at half dozen months of age. Information technology increases by near i inch during the second year, and during the tertiary through the 5th year caput circumference increases past about half inch per year. At that place is only a 4 inch increase in herd circumference from the end of the 1st year to the 20th year (Fig nine).

A comparison of face-braincase proportions in the kid and adult. The horizontal line passes through the same anatomical landmarks on both skulls.

Skull profiles showing changes in size and shape. (Modified from Morris' "Human being Anatomy.")

Head circumference increases markedly during the beginning postnatal year due to the progressive and rapid growth of the encephalon as a whole. The important relation of brain size and cranium size can exist demonstrated on a percentage basis, which shows that lxx% of the adult brain weight is achieved at eighteen months, 80% at 3 years, 90% at five–eight years and approximately 95% at the 10th year. In the adult the average encephalon weight is 1350 g.

Infant and child skulls are considerably pliable, due to the segmental development and arrangement of the skull bones, plus the flexibility of individual basic which are extremely thin. The skull develops equally a loosely joined system of basic formed in the soft tissue matrix surrounding the encephalon. Junctions between bones are relatively broad and large, leaving areas of brain covered past a thin fibrous sheath and somewhat exposed to the external environment. These 'soft spots' (fontanelles) are several in number and are most obvious in the frontal and posterior skull regions (Fig. x). The mastoid fontanelle, betwixt the occipital and parietal bones, airtight nearly vi–8 weeks after birth. However, a much larger midline junction between the frontal and parietal bones, i.e., frontal fontanelle, is not closed by bone growth until approximately the 17th month.

Size and location of the fontanelles. Arrows indicate management of fontanelle closure.

At nativity all of the potential structures for the development of teeth are present. The early on teeth offset erupt at bout half dozen months of age and continue to erupt progressively. The child begins to lose his deciduous teeth about five–six years of historic period after which they are replaced by the permanent teeth.

Trauma to the jaws of infants or small children, especially in the area where the unerupted teeth are found can lead to serious problems in tooth eruption, molar spacing, tooth arrangement and alignment. Traumatic injuries to the child's lower jaw (mandible) may exist related to abnormal facial profiles with increasing age. The normal changes in size and position of the lower jaw are dependent upon a growth site in the mandible located nearly its junction with the skull. If this of import growth site is significantly traumatized, the normal changes in size and position of the mandible diminish resulting in a smaller mandible and a recessive mentum.

THE NECK

There are several unique aspects of the anatomy of the child's neck. Neck muscle strength increases with age notwithstanding, with the greater head mass perched on a slender neck, the neck muscles by and large are non developed sufficiently to dampen vehement head movement, especially in children. In a study of lap-shoulder belted children, ages 10–fourteen years in all types of motor vehicle crashes, nigh 21% had cervical strain (Agran & Winn, 1987). The cervix vertebrae of children are young models of the adult. These cervical vertebrae are mainly cartilaginous in the infant, with complete replacement of this cartilage by bone occurring slowly. Articular facets, the contact areas between the vertebrae, are shallow; neck ligaments, as elsewhere in the body, are weaker than in adults. The disproportionately large head, the weak cervical spine musculature, and laxity, can subject the infant to uncontrolled and passive cervical spine movements and perchance to compressive or distraction forces in certain impact deceleration environments. These all contribute to a high incidence of injury to the upper cervical spine every bit compared to the lower cervical spine area (Sumchi and Stemback, 1991).

The articular facets of the infant and immature children are oriented in an even more horizontal direction than in the adult (Kasai, et al, 1996) (sixty deg. @ 1 twelvemonth, 53 deg. @ 3 years and 47 deg. @ 6 years). The "cervicocranium", the base of the skull, C1, C2 and the C2/C3 disc is a singled-out unit in infants and pocket-size children, and should be considered as a specialized surface area of the cervical spine considering of its anatomical difference from the lower and more uniformly shaped cervical vertebrae (Huelke, et al, 1992). Using dynamic cervical spine radiographs it has been shown that the fulcrum for flexion is at C2-C3 in infants and young children, at C3-C4 at about age 5 or 6 and at C5-C6 in adults (Baker and Berdon, 1966).

In that the skull base, C1 and C2 move as a unit in flexion and extension, and in some rotation, it is not surprising that anterior deportation of the entire cervicocranial unit tin can occur after traumatic disruption of the posterior portions of C2, causing separation of the neural arch ossification centers, stretching of the elastic ligaments, or bilateral fractures of the pedicles without evidence of dislocation (Sumchi, and Stembacck, 1991). A lark force on the cervical spine can pull apart the cervical cartilagenous-osseous structures and associated ligaments and, if in a forward direction, can cause spinal cord damage (Finnegen and McDonald, 1982; Tingvall, 1987).

It has been reported that pseudosubluxation or physiological inductive deportation of C2 on C3 of more than than three millimeters occurs in approximately 24–33% of children less than eight years of age (Dunlap, et al, 1958; Fuchs, et al, 1989; Papavasilou, 1978). In autopsy specimens the rubberband infantile vertebral bodies and ligaments allows for column elongation of up to two inches, but the spinal string ruptures if stretched more 1/4 inch (Leventhal, 1960). Thus it is hard to differentiate physiological deportation from pathological dislocation of C2 on C3 in childhood, especially when an x-ray is taken with the child'south head in flexion (Swishuck, 1977). Occasionally in immature infants, there is a reversal of the normal anterior curve, seen in lateral C-spine x-rays, probably due to the weak, immature cervical musculature (Harris and Edeiken-Monroe, 1987).

If cervix motion exceeds tolerable limits, dislocation of vertebrae and mayhap injury to the spinal cord can occur. This combination of anatomical features results in lowered protection of the neck in rapid deceleration and if the head is rotated or snapped to the side or to the rear, serious harm might occur to the delicate system of critical arteries or veins of the brain, to nerves, to the vertebrae, and/or the spinal cord itself. The mechanism of pediatric cervical injury is relatively straight forward---head flexion with either a tension or compression component and a relatively restrained torso. Basically, in the frontal-type crash the caput continues forrard across the belted torso. The construction of the child'southward neck certainly plays a office in the injury. Fuchs, et al (1989) best summarized the reasons for this, including (1) A heavy head on a small body results in high torques existence practical to the neck and consequently, loftier susceptibility to flexion-extension injuries, (2) The lax ligaments that allows a significant degree of spinal mobility (anterior subluxation of up to four.0 mm at C2-3 or C3-4 may occur as a normal variant), (3) The cervical musculature is not fully adult in the infant allowing for unchecked distracting and displacement forces, (iv) The facet joints at C1 and C3 are nearly horizontal for the beginning several years of life assuasive for subluxations at relatively piddling forcefulness, (5) Immature uncovertebral joints of the C2 to C4 levels may not withstand flexion-rotation forces (6) The fulcrum of cervical movement is located higher in young children (C2-3 level than in adults (C5-6).

THE Chest

Thoracic injuries in children subjected to impact usually occur to the internal organs. The thoracic walls are thinner and the ribs more elastic in infants and immature children than in the adults. Therefore, affect to the thorax of an baby or a small child volition produce larger amounts of chest wall deflection onto the vital thoracic organs, east.g. middle, lungs. As clinicians well know, closed cardiac massage in infants can be performed by using only 1 or two fingers which well demonstrates the highly elastic nature of the chest wall.

At birth the infant centre lies midway between the top of the head and the buttocks. The long axis of the middle is directed horizontally in the fourth intercostal space with its noon lateral to the midclavicular line. These relationships are maintained until the fourth year, and after the heart gradually moves downwards, due to the elongation of the thorax, until it comes to lie at the 5th intercostal infinite with its apex inside the midclavicular line. Until the first twelvemonth, the width (or length) of the center is no more than than 55% of the chest width taken at the xyphoid line. After the first year, heart width is slightly less than fifty% of the chest width (Fig. 11).

Schematic diagram of the position al changes of the heart within the chest at various ages. (Redrawn from Watson and Lowrey, "Growth and Development of Children.")

At birth the chest is circular, merely as the infant grows the transverse diameter becomes larger than the anterior-posterior dimension, giving the chest an elliptical appearance. At birth the breast circumference is well-nigh one-half inch smaller than the head. At 1 year the chest is equal to or exceeds head circumference slightly; later on 1 year the chest becomes progressively larger in diameter than the head.

Scientists are not entirely in agreement as to the master biomechanical causation of cardiac trauma during impact in the adult. Researchers such as Stapp (1965) and Taylor (1963) report that pressure is the major cistron. Yet, cardiac rupture has been produced experimentally in animals with the blood book entirely removed, strongly suggesting that other factors are involved (Roberts et al, 1965). Lasky et al (1968), studying developed humans involved in steering-wheel impacts, believes that aortic laceration occurs at the weakest and narrowest point of the aortic arch, and that this anatomical fact is of biodynamic significance.

Introducing a new consideration, Life and Pince (1968) have demonstrated experimentally in animals that the contractile country of the ventricular myocardium at the instant of impact plays a disquisitional role in whether or not cardiac rupture volition occur. Clinical daze with abnormally dull heart and pulse rates (bradycardia) occurs without structural failure in homo adult impact tests, and constitutes a primary limitation to the charge per unit of onset (Taylor, 1963).

No thoracic impact data are available for children. Because the differences between child and adult morphology, impact tolerances for the child are probably considerably less than those of the developed.

THE ABDOMEN

Although statistically meaningful studies on child abdominal injuries have not been conducted, the issue of blunt abdominal trauma to children, equally compared to adults, has been suggested in the literature. Tank et al (1968), noted that but cerebral injuries and burns outrank injury to the abdominal organs equally a grade of serious adventitious injury to children. In adults, blunt injury to the abdominal viscera presents the almost hard diagnosis and treatment, and results in the highest mortality rate (Fonkalsrud, 1966; Orloff, 1966). Thus, any blunt intestinal injury tin be potentially serious, just such injuries to the infant and child are much more critical due to their developing and immature structure, big organ relationships, and almost consummate lack of overlying muscle or skeletal protection.

The bulge of the newborn abdomen is accentuated by the abdominal viscera pushing forward during respiration against the weak and atonic muscle wall of the abdomen. The right side of the infant and newborn belly is especially enlarged due to the depression position of the liver which occupies two-fifths of the abdominal cavity. Along the midclavicular line the liver is approximately two cm beneath the costal margins in the newborn; one and one-half cm below the margin for the residuum of the outset year; and 1 cm below from eighteen months to 6 years. After well-nigh the 6th–7th year, the liver is seldom palpable except in abnormal cases. On a weight basis, the liver of the newborn comprises 4% of the total body weight, and by puberty weighs 10 times as much (Watson and Lowery, 1967). The liver, although considered every bit an abdominal organ, lies almost entirely deep to the correct lower ribs and the highly elastic ribs of the child offer minimal protection for this organ from touch on.

Posteriorly, a like relative migration of the bony thorax down occurs to provide some protection for the spleen, kidneys, and suprarenal glands as the babe ages. At birth, for example, the kidneys occupy a large portion of the posterior abdominal crenel owing to their relatively big size.

In the newborn, the urinary bladder lies shut to the lower abdominal wall with merely its lower portion located behind the pubic bones. During babyhood, much of the bladder descends into the pelvic area where information technology is more protected past the bony pelvis.

Again, many of the kid abdominal viscera are relatively unprotected by bone equally compared to the adult. The bladder is located higher, exterior the pelvic area, the liver and kidneys are relatively exposed, all existence more than available to traumatic insult. The liver is an organ which is not well designed for withstanding traumatic insults fifty-fifty in the adult. Traumatic liver injuries produce the highest mortality rate of any abdominal organ (Di Vincenti et al, 1968). With the smaller chest and pelvis of the kid, less of the intestinal contents are protected by the rib cage and bony pelvis, and can be more easily injured.

Dimensions of the intestinal area also differ from that of the adult, both proportionately and in relation to position of torso organs. Intestinal girth, in full general, is most the same every bit that of the chest during the first 2 years of life. After ii years, increases in intestinal circumference at the umbilical level practise non keep pace with the increases in thoracic girth. Pelvic breadth is some other dimension which is less subject area to variations in body posture and tonic activeness of the muscular abdominal wall. The maximum distance between the external margins of the iliac crests is approximately 3 inches at birth, 5 inches at 1 yr, seven inches at 5 years and nine inches at 10 years of historic period. Mostly, in the early part of infancy there is niggling change in trunk class, but after the assumption of erect posture in that location is a relative reduction in the anterior-posterior bore of both of the thoracic and intestinal regions, accompanied by a decrease in the relative size of the umbilical region and a relative increase in the lumbar region. These changes continue throughout childhood and early boyhood.

THE VERTEBRAL Column

Normal development of erect posture involves a gradual transition from the early crawling stages involving interrelationships of the extremities, spine, and pelvis, to the well-balanced weight- bearing relationships typical of the adult. When the infant first stands, the pelvis is tilted far forward on the thighs and an erect posture is starting time attained in infancy concurrent with the development of the lumbar (depression dorsum) bend. As a result of this lumbar curve, combined with increased tonic activity of abdominal wall muscles the infant develops his characteristic sway-back and intestinal prominence which is maintained throughout pre-school years. The infant pelvis gradually rotates up and forward beginning to institute an adult-like posture. The curvature of the sacrum as seen in the adult is already nowadays at nascence; withal, in infants the vertebral column above the sacrum is usually straight (Fig. 12).

Curvature of vertebral column emphasizing the development of primary curvatures (P) and secondary curvatures (Due south). Note: in the infant there are simply 2 primary curves, i.east. thoracic and sacral. In the adult there are secondary curves in the cervical and lumbar regions. In the aged only the main curves persist. (Modified from Johnson and Kennedy, "Radiographic Beefcake of the Homo Skeleton.")

Early in infancy the baby can enhance his head while lying prone, and the cervical (cervix) curve showtime becomes well established every bit the caput is held cock and cervical muscles become developed and increase their tone activity. By the third or 4th month the infant tin sit with support and by the 7th month can be expected to sit lonely. At 8 or 9 months the infant tin can usually stand up with support and so tin stand without assistance by ten–14 months.

In the developed, the prominent anterior superior iliac spines are used every bit anatomical ballast points. Simply in children these spines are not well developed until about 10 years of age and basically exercise not yet exist. Rather this anterior pelvic surface area is a broad gentle curve without a prominent spine as in the adult.

THE LIMBS

In considering the growth of the extremities information technology is necessary to examine factors of skeletal embryology and subsequent dimensional changes (Scammon and Calkins, 1929). Considering get-go the trends in dimensional growth of the limbs, it is mostly noted that the lower limbs increase in length more rapidly than do the upper limbs. At about 2 years of age, for example, their lengths are equal but in the adult the lower limb is about on-sixth longer than the upper limb. The adult relations of the different limb segments are well established prenatally; however, there is some reduction in the relative length of the hand and of the foot afterward birth. At birth the lower limb forms about 15% of the body volume and in the adult reaches about 30%. In contrast the upper limb constitutes nigh 8% of the body weight at nativity and maintains this aforementioned proportionality thereafter.

As in the skull, the long bones of the extremities laissez passer through successive developmental stages which, when compared to adult morphology, make the limb bones less tolerable to trauma. In early development before nascence, long bones are typically represented past a shaft of bone which grows in bore by addition of new os on its surface with concomitant erosion within the shaft. This evolution of the shaft can best be described as a tube that progressively increases in diameter. Impact tolerances of children's basic are dependent upon the irresolute girth of the bone and relative proportions of the marrow cavity and bony walls, as well as the proportions of inorganic and organic materials that class bone tissue. In the early evolution of bone tissue, organic materials outweigh inorganic components. The degree of flexibility or torsional strength of the bone itself is directly related to the organic component of the os structure. The preponderance of organic material continues through adolescence after which in that location is a gradual buildup of inorganic bone substance.

Change in length of long bones is a function of the connected growth of epiphyseal cartilage. In the early on development of a long bone the shaft is capped on both ends by cartilage. From late fetal life through puberty bond tissue appears in the cartilage at either stop of the shaft but does non attach to the shaft. There is a remaining cartilaginous epiphyseal plate between the bony shaft and the bony epiphyseal ossification center at each end. The surface of the epiphyseal cartilage in contact with the long os shaft continues to abound which effectively moves or pushes the epiphyseal bone cap away from the shaft. This activity of the epiphyseal cartilage accounts for increases in length of the long bone. Finally, when the adult length is attained for a specific bone equally influenced by sex, race, nutrition and endocrine balance, the cartilage of the epiphyseal plate stops proliferation and begins to ossify. Thus, the bony epiphyseal cap is united to the shaft. In females the epiphyses unite sooner so that growth in length ceases before by about two–3 years when compared to males of similar ages. Simply fifty-fifty in the male person most of the fusions of long bone epiphyseal cartilages are completed at about the twentieth year. Obviously, since os length is a factor of epiphyseal cartilage growth, traumatic deportation of the cartilage out of line with the normal solitary axis of the bone can lead to gross limb distortion and malformations.

Conclusions

Infants and children are not miniature adults. Their anatomy differs from the adult in a number of ways which should be considered in the proper blueprint of occupant restraint systems specific to their age. Inside the framework of automobile condom blueprint it should exist emphasized that:

1. The frequency of caput injuries in children involved in automobile accidents may be due to the child'southward proportionately large head and higher eye of gravity. Every bit a consequence, infants and children restrained by a lap belt have a greater chance of beingness projected over the restraining belt because the CG and trunk fulcrum is located above the belt location.

2. Observations that the child's caput is relatively massive and supported poorly from beneath have been implicated in head snapping with rapid body deceleration. Such sudden snapping or rotation of the relatively unrestrained child's head can traumatize related nerves, blood vessels, and spinal cord segments.

3. Contributing to brain injuries of the young child is the relative lack of skull protection since, early on in life, the skull is not an intact bony example for the brain but is a series of broadly spaced rubberband basic.

4. Growth rates of different parts of the body vary with age. For case, the mid-point of the body is higher up the navel at birth, slightly below it a 2 years of historic period and nearer the pubic basic at sixteen years.

5. Since growth of the kid is dependent upon the normal activeness of growth centers, protection of these centers is vital. Abnormalities of body stature and limb mobility might effect from injury to growth centers of the extremities. Similarly, in the head, the organization of teeth every bit well equally the facial contour tin be afflicted by traumatic injuries to the facial growth centers.

6. Unlike the developed, the organs of the chest are housed in an elastic and highly compressible thoracic cage. Organs every bit the lungs and heart are extremely vulnerable to nonpenetrating impacts to the chest. The smaller rib cage also means less protection is offered to larger abdominal organs which would normally receive some protection class the larger stronger rib muzzle of the developed. The highly elastic construction of the thoracic cage is non acquiescent to direct trauma or loading of webbed restraints in children.

​

Increase in total stature at various ages as compared to the developed. (Modified from Chenoweth and Selrick, "Schoolhouse Health Problems.")

Footnotes

^§This newspaper is a modification and update of "Infants and Children in the Developed World of Car Prophylactic Design: Pediatric and Anatomical Considerations for Design of Child Restraints", Burdi, AR, Huelke, DF, Snyder, RG, et al, J Biomech. 2:267-280,1969.

References

• Agran PF, Winn D. Traumatic Injuries Among Children Using Lap Belts and Lap/Shoulder Belts in Motor Vehicle Collisions. 31st Proc Am Assn for Auto Med. 1987:183–307. [Google Scholar]
• Chenoweth LB, Selkirk T. Schoolhouse Wellness Problems. Crofth; New York: 1937. [Google Scholar]
• Crosby WM, Snyder RG, Snowfall CC, et al. Bear upon Injuries in Pregnancy--I. Experimental Studies. Am J Obstet Gynec. 1968;101:100–110. [PubMed] [Google Scholar]
• DiVincenti FC, Rives JD, Labordge EJ, et al. Blunt Abdominal Trauma. J Trauma. 1968;8:1004–1013. [PubMed] [Google Scholar]
• Dunlap J, Morris M, Thompson R. Cervical-Spine Injuries in Children. J Os & Jt. Surg. 1958;forty-A:681–686. [PubMed] [Google Scholar]
• Fonkalsrud EW. Astute Trauma in Infants and Children. In: Nahum A, editor. Early Manaaement of Astute Trauma. Mosby; St. Louis: 1966. pp. 180–192. [Google Scholar]
• Finnegen M, McDonald H. Hangman'southward Fracture in an Babe. CMAJ. 1982;127:1001–1002. [PMC complimentary article] [PubMed] [Google Scholar]
• Fuchs Due south, Barthel JJ, Flannery AM, et al. Cervical Spine Fractures Sustained by Immature Children in Forward-Facing Car Seats. Pediatrics. 1989;84:348–354. [PubMed] [Google Scholar]
• Harris J, Edeiken-Monroe B. The Radiology of Astute Cervical Spine Trauma. Williams and Wilkins; Baltimore, Medico: 1987. pp. 1–ten. [Google Scholar]
• Huelke DF, Mackay GM, Morris A, et al. Car Crashes and Non-Head Touch on Cervical Spine Injuries in Infants and Children. Soc Automobile Eng Intl Cong; Detroit, MI. 1992. Paper No. 920562. [Google Scholar]
• Johnson WH, Kennedy JA. Radiographic Anatomy of The Man Skeleton. Williams and Wilkins; Baltimore: 1961. [Google Scholar]
• Kasai T, Ikata T, Katoh S, et al. Growth of the Cervical Spine With Special Reference To Its Lorclosis and Mobility. Spine. 1996;21(eighteen):2067–2073. [PubMed] [Google Scholar]
• Kihlberg JK, Gensler Hour. Head Injuries in Automobile Accidents Related to Seat, Position and Age. Cornell Aeronautical Laboratory, Inc; 1967. [Google Scholar]
• Krogman WM. Philadelphia Centre for Research in Kid Growth. Philadelphia, PA: 1960. Peak, Weight and Body Growth of American White and American Negro Boys at Philadelphia, Aged half-dozen–14 Years. [Google Scholar]
• Krogman WM, Johnston Atomic number 26. Philadelphia Center for Research in Child Growth. Philadelphia, PA: 1965. The Physical Growth of Philadelphia White Children, Age 7–17 Years. [Google Scholar]
• Krogman WM. Tabulate Biologicae. Vol. 20. Vitgerverij Dr. W. Junk; Den Haag: 1941. Growth of Man. [Google Scholar]
• Lasky I, Siegel AW, Nahum AM. Automotive Cardio-Thoracic Injuries: A Medico-Engineering Analysis. Soc Auto Eng; New York. 1968. SAE preprint No. 680052. [Google Scholar]
• Leventhal H. Birth Injuries of the Spinal Cord. J Ped. 1960;56:447–453. [PubMed] [Google Scholar]
• Life JS, Pince BW. Response of the Canine Heart to Thoracic Impact During Ventricular Diastole and Systole. J Biomech. 1968;1:169– 173. [PubMed] [Google Scholar]
• Martin WE, Thieme FP. A Articulation Project of the US Office of Didactics. The University of Michigan and the National School Service, Institute; Chicago, IL: 1954. The Functional Trunk Measurements of Schoolhouse Age Children. [Google Scholar]
• Meredith HW. Advances in Child Development and Behavior. Vol. 1. Academic Printing; New York: 1963. Change in the Stature and Body Weight of North American Boys During the Final fourscore Years. [Google Scholar]
• Moore JO, Tourin B, Garrett JW, et al. Child Injuries in Automobile Accidents. Presented at 14th Intl Conf Pediatrics; Montreal Canada. Besides in Traffic Rubber Res Rev iv:sixteen–21, 1959. [Google Scholar]
• Morris H. In: Morris' Human Anutomy. 12th Edn. Anson BJ, editor. Blakiston, NY: 1966. [Google Scholar]
• Orloff MJ. In: Intestinal Injuries. Early Management of Astute Trauma. Nahum A, editor. Mosby; St. Louis: 1966. pp. 148–161. [Google Scholar]
• Papavasiliou 5. Traumatic Subluxation of the Cervical Spine During Babyhood. Orthoped Clin Due north Amer. 1978;9:945–954. [PubMed] [Google Scholar]
• Salzmann J. Principles of Orthodontics. Lippincott; Philadelphia, PA: 1943. [Google Scholar]
• Scammon RE, Calkins LA. The Development and Growth of the External Dimensions of the Man Body in the Fetal Period. Univ of Minnesota Press; 1929. [Google Scholar]
• Stapp JP. Trauma Caused past Impact and Smash. Clin Neurosurg. 1965;12:324–343. [PubMed] [Google Scholar]
• Stuart HC, Stevenson SS. In: Physical Growth and Evolution. 5th Edn. Nelson, editor. Mitchell-Nelson Textbook of Pediatrics; Philadelphia: 1950. 1959. Reprinted in Documents-Geigy, Scientific Tables. [Google Scholar]
• Sumchi A, Sternback G. Hangman's Fracture in a 7-Week Old Infant. Ann Emerg Med. 1991;20:86–89. [PubMed] [Google Scholar]
• Swearingen JJ, Young JW. Determination of Centers of Gravity of Children, Sitting and Standing. Civil Aeromed Res Inst, Federal Aviation Agency; Oklahoma City, OK: 1965. Rep. No. AM 65-23 August. [Google Scholar]
• Swishuk L. Anterior Displacement of C2 in Children: Physiologic or Pathologic? Ped Radiol. 1977;122:759–763. [PubMed] [Google Scholar]
• Tank ES, Eraklis AJ, Gross RE. Blunt Intestinal Trauma in Infants and Childhood. J Trauma. 1968;8:439–448. [PubMed] [Google Scholar]
• Taylor ER. Biodyamics: By, Nowadays and Futurity. 657 1st Aero-medical Res Lab; Holloman AFB, New Mexico: 1963. Rep. No. ARL- TDR-63-x. [Google Scholar]
• Tingvall C. Injuries to Restrained Children in Cars Involved in Traffic Accidents. Acta Paedriatr Stand up Suppl. 1987;339(III):1–15. [Google Scholar]
• Watson EH, Lowrey GH. Growth and Development of Children. 5th Edn. Year Book Publishers; Chicago, IL: 1967. [Google Scholar]
• Weech AA. Signposts on the Highway of Growth. AMA Am J Dis Child. 1954:881452. [PubMed] [Google Scholar]
• Young, JW: Personal communication. Unpublished Infant C.Thou. data, 1968.

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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3400202/

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