Growth Cartilages of the Spine and Pelvic Vertebra

Fig. 1

Schmorl’s original drawing of a thoracic vertebra showing (a) the NCC and (b) the ring apophysis

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig2_HTML.png — Fig. 2

Histology of the NCC: (a) active bipolar cartilage, (b) cartilage at a later age, (c) closed cartilage

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig3_HTML.jpg — Fig. 3

Chronology of closure of the NCC initially in cervical and lumbar, then in the thoracic spine

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig4_HTML.jpg — Fig. 4

Chronology of closure of the NCC in the same child with a double curvature: (a) right thoracic, (b) left lumbar. The closure is earlier in lumbar than in the thoracic

We studied the anatomy of 20 children from under 1 year to 16 years and CT scans of 30 children from 3 to 18 years (10 healthy children with axial images at T8 and 20 pathological cases including 15 congenital scoliosis, 2 lordo-scoliosis and 3 severe kyphoses) [8].

Table 1 shows the series of anatomical specimens studied by Beguiristain (Fig. 5). On these vertebrae of different ages, there was a natural progressive narrowing of the NCC towards closure, a relative decrease in the antero-posterior direction (study of the ratio (AC/AB)) due to the continued growth of the vertebral body while the posterior arc no longer increases (Figs. 6 and 7) and a relative horizontalization of the NCC in the axial plane (Fig. 8). For the CT scan, general anaesthesia had to be performed in those under 3 years of age and positioned in the lateral decubitus with a small bolster in the cases of scoliosis to horizontally align the inclined vertebrae and avoid a false image plane (pre-digital imaging) (Figs. 9 and 10). The constants selected for the CT were 800–1600 Hounsfield units. The sections studied were sagittal and coronal (Fig. 11). This examination, more precise in the study of the NCC than MRI, made it possible to recognize its shape, and thus its complete closure, occurring very late (Fig. 12). We have also shown the asymmetrical closure of concave and convex NCCs in scoliosis, as discussed later. MRI was used by Yamazaki et al. [9] to study the age of NCC closure in the thoracic spine: between 11 and 16 years for girls and 12 and 16 years for boys.

Table 1

Anatomical specimens

Number	Age	Gender
1	Foetus	M
3	New born	1M 2F
1	3 months	M
1	11 months	M
2	2 years	1M 1F
2	3 years	2M
1	4 years	F
2	5 years	2F
1	6 years	M
1	7 years	M
1	9 years	F
1	11 years	M
1	12 years	M
1	14 years	F
1	16 years	M
20		12M 8F

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig5_HTML.png — Fig. 5

Anatomy of the NCC on 3 thoracic vertebrae of different ages, a = newborn, b = 6 years, c = 12 years

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig6_HTML.png — Fig. 6

NCC anatomy : e = thickness, AC/AB = anteroposterior position of the NCC

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig7_HTML.png — Fig. 7

NCC anatomy evolution of the AC/AB ratio: a = vertebra of 10 years, b = vertebra of 16 years

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig8_HTML.png — Fig. 8

Anatomy of the NCC: Horizontalisation over time

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig9_HTML.jpg — Fig. 9

Positioning in lateral decubitus to minimize scoliosis, with an image taken at the level of the apical vertebra

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig10_HTML.jpg — Fig. 10

Comparison of two images: (a) non-horizontal and uninterpretable, (b) correct

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig11_HTML.jpg — Fig. 11

CT Scan of a thoracic vertebra in a 6-year-old child; sagittal cut (a) and axial at different levels (b, c, d)

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig12_HTML.jpg — Fig. 12

CT Scan of a vertebra in a young adult showing the physeal scar and therefore the recent closure of the NCC

The NCC has a dynamism of growth: it changes spatial orientation as it self horizontalises over time.

The NCC has another polarity: it ossifies the vertebral body and the posterior arch

The NCC has a double action (Figs. 13, 14): control of the anteroposterior dimension of the central spinal canal, which is therefore fixed early, as shown by Knutsson [2] (Fig. 15), and height of the posterior 1/3 of the vertebral body.

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig13_HTML.png — Fig. 13

Action of the NCC: control of the size of the central spinal canal (a) and control of the height growth of the posterior part of the vertebral body (b)

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig14_HTML.png — Fig. 14

Neurocentral cartilage has a bidirectional activity. It contributes posteriorly to the ossification of the posterior arch and anteriorly to a third of the ossification of the vertebral body

../images/451372_1_En_4_Chapter/451372_1_En_4_Fig15_HTML.png — Fig. 15

Evolution of the dimensions of the spinal canal (a) and the anteroposterior diameter of the vertebral body (b), according to Knutsson [2]

Nicoladoni [3] has shown, on histological sections of scoliotic vertebrae , the earlier closure of the convex NCC (Fig. 16). Beguiristain et al. [10] showed on the growing pig that unilateral screw fixation of the NCC caused a scoliosis with rotation of the convex side corresponding to the side of the NCC interupted by the screw fixation (Fig. 17). The same result was obtained more recently by Zhang and Sucato [11]. In our study, the scanners performed early in the case of early scolioses allowed us to recognize this early closure of the NCC on the convex side (Fig. 18); The concave part of the neural arc is longer, since the NCC acts longer on this side, which goes in the direction of the rotation of the body towards the convexity (Fig. 19). We can compare this dysfunction of the NCCs in the axial plane of the hyperlordotic spine observed in the most severe scoliosis because of the action of the NCC in the growth of the posterior part of the vertebral body (Fig. 20). This corresponds to Dickson’s scheme [12], which has shown that the thoracic scoliotic segment where there is rotation is in hypokyphosis or even in lordosis (Fig. 21).