A cephalometric and histologic study of the cranial base in foetal monkeys, Macaca nemestrina

Archs oral Biol Vol. 23. pp. 57 10 67 Pergamon Press 1978. Printed m Great Bntam

A CEPHALOMETRIC AND HISTOLOGIC STUDY THE CRANIAL BASE IN FOETAL MONKEYS, MACACA NEMESTRINA Department of Orthodontics,

R. N. MOORE* School of Dentistry, University

Seattle.

OF

of Washington.

WA 98195. U.S.A.

Summary-With increasing gestational age (101-170 days), the sagittal endocranial profile of the basi-occipital bone became progressively more concave. Other cranial base structures showed continGed bony apposition with less pronounced alterations in shape. Although there were no statistically significant angular changes with age or sex among the structures studied. there was a significant correlation (r > 0.6) of the basisphenoid and presphenoid bones, indicating that the midsphenoidal synchondrosis is a relatively stable articulation during late gestation.

INTRODUCTION Alterations of the cranial base in the human foetus with increasing gestational age have been investigated using midline sagittal sections (Ford, 1956, 1958; Burdi, 1965, 1969; Baume, 1968; Birch, 1968; Houpt, 1970; Kvinnsiand, 1971, 1973; Johnston, 1974) and cephalometric radiographs (Mestre, 1959; Inoue, 1961; Kobayashi and Inoue, 1961; Levihn, 1967; Preston, 1976). These studies in general indicate that the linear dimensions of the’cranial base, but not the cranial base angle (basion-sella-nasion), have a statistically significant correlation with crown-rump length (Burdi, 1965, 1969; Birch, 1968; Houpt, 1970; Preston, 1976). The ahterior cranial base (sella-nasion) accounts for approximately one-half the total cranial base length in the second trimester and two-thirds of its length in the older specimens (Ford, 1956; Mestre, 1959; Burdi, 1965; Levihn, 1967; Birch, 1968; Kvinnsland, 1971; Johnson, 1974). The cranial base angle exhibits an increase during the entire gestational period, ranging from 12 to 23” depending on the study (Ford, 1956; Mestre, 1959; Levihn, 1967; Burdi, 1969; Kvinnsland, 1971, 1973). This increase has not, however, been confirmed by Preston (1976). The region of angular change has been reported to be located in the area of sella (Inoue, 1961) or the spheno-ethmoidal junction (Kvinnsland, 1971). Although the growth rates of the components of the craniofacial complex are generally considered to exhibit a proportional constancy (Inoue, 1961; Burdi, 1965, 1969; Houpt, 1970), a statistical study by Johnston (1974) showed that, during the second trimester, the mandible, midface and anterior cranial base grow isometrically, but the posterior cranial base becomes relatively smaller. As the non-human primate is an important experimental model for human craniofacial growth and no investigations of the morphology of the foetal non* Present address: Dentistry, University U.S.A.

Section of Orthodontics, of California, Los Angeles,

School of CA 90024.

human primate cranial base have been reported. I have examined the morphologic changes of the foetal macaque cranial base.

MATERIALS AND

METHODS

The foetuses (Macaca nemesrrina) used were obtained from the Regional Primate Research Center and prepared for study by the Department of Orthodontics at the University of Washington. The 43 specimens (Table 1) comprise the entire collection and were obtained primar,ily by caesarian section and occasionally by spontaneous abortion. All were preserved in 10 per cent buffered formalin. Foot lengths were measured and using a standard curve of-foot length to known gestational age (L. Newell-Morris and L. Tarrrant, 1976, personal communication), the animals were grouped into IO-day gestational age groups ranging from 101 to 170 days. For cephalometry, each specimen was positioned in a primate head holder and laterally radiographed with a Dome cephalometer using 5 x 7 inch Kodak type AA industrial film. Because of the small size of the foetal skull, the radiographs were photographically enlarged 2.5 times and the outline of the desired anatomical structures was traced on 0.003 inch matte acetate paper. Most of the cephalometric landmarks (Text Fig. 1, Table 2) used were similar to those which have been used in man (Bjork, 1955; Koski, 1973) and Macacu mulatta (Vinkka, Koski and McNamara, 1975) with anatomical planes represented as the best-fit short lines between specific landmarks (Solow, 1966). As the foetal dorsum sellae is cartilaginous and does not radiograph well, for purposes of reproducibility, sella was defined as the most inferior portion of the bony sella on a plane parallel to foramen magnum (Ford, 1956). For similar reasons, the orbital plane (ORB) was defined by a plane tangential to the orbital roof passing through the most superior endocranial point of the presphenoid bone (Koski, 1973). The angle. viewed as opening on the face, between each radiographically-defined anatomical plane and foramen mag-

R. N. Moore

58

Table 1. Sample distribution Group

I

II III IV V VI

Estimated gestational age (days)

Number

101-l 10 121-130 131-140 141-150 151-160 161-170

in group

Male

Female

4 5 6 2

2 3 4 5 8 3

num (Text Fig. 1) was measured to the nearest 0.5 degree. The numerical angular relationships of all planes to one another were calculated by geometric transposition (Text Fig. 2). To avoid mathematical correlations, angular relationships were based on the angles between adjacent planes such that no angle was completely contained within another. Total technique error was determined by analyzing cephalometrically the same animal on five separate occasions. Of the initial 28 calculated angles (Text Fig. 2), five had an angular technique error (Solow. 1966) greater than 5 per cent and were not utilized in subsequent calculations. To determine the amount of error in the photographic process and in observer angular measurement, a rectangular grid with two diagonals was photographed using the same enlarging technique and five prints were made from the negative. The 12 angles of the control grid and of the ftve prints were measured on five separate occasions. The mean value for each angle was calculated and the difference of that value between the control and the prints represented the amount of error attributable to photographic processing and observer angular measurement. The mean difference was 0.25’, well within the 0.5” range to which the cephalometric radiographs were measured. For histology, three specimens representmg each estimated lo-day age group were demineralized in a formic acid solution (Molnar, 1975~) and embedded in celloidin or double-embedded in nitrocellulose and paraffin (Molnar, 1974). Serial sagittal sections (celloidin 25 pm, paraffin 7 pm) were prepared, every tenth slide being stained with. modified haemataxylin and eosin (Molnar, 1975a). The next three successive slides were stained using modified Mallory’s aniline blue,

Foot length (mm)

Unknown 1

42244 53-57 60-66 67-73 74-76 79-85

Verhoeff and alcian blue periodic-acid Schiff procedures, respectively (Molnar, 1976a, 1975b, 1976b). Sections that included the posterior maxillary dentilion were used for analysis of the orbital roof. RESULTS

Cephalometric angular analysis The angular relationships of the radiographic planes (Table 3) showed no definitive trends or statistically significant changes with mcreasmg gestational age (foot length). Therefore Groups III to V, which contained the most specimens, were combined in an attempt to define statistically the association of variables more concisely. Age and sex. A two-way analysis of variance (age by sex) was run for each variable in the combined group and none showed significant sex differences or age-sex interaction. In subsequent calculations, males and females from the same age group were combined. Angles and planes. None of the angles measured to foramen magnum (Text Fig. 1) nor the calculated angles (Text Fig. 2) correlated significantly (r > 0.6) with foot length for the combined group. Correlation coefficients were calculated between each radiographic plane of the combined group. The results (Table 4) showed a statistically significant correlation (r # 0) between all radiographic planes. However, when only the higher values were considered, a more specific pattern emerged. Those planes associated with the same bone (CLIVUS, PHAR and BAS) showed highly significant correlations (r > 0.9). Even though the midsphenoidal synchondrosis intervened. the basisphenoid and basi-occipital bones showed a strong linear association (r > 0.6). The sphenoid and orbital planes exhibited a moderate correlation, and

N

PRESPH

k

BA

Fig. 1. Schematic

representation

of radiographic

anatomlcal

planes

defined

in Table 2

Foetal macaque cranial base Table 2. Definition Opisthion

of radiographic

59

points and planes

(cm

Perpendicular projection of the posterior bborder of foramen through the inferior contour of the foramen (Bjork, 1955).

Basion (BA)

Perpendicular to the tangent

Foramen magnum (FM) Dorsal clivus (CLIVUS) Ventral clivus (PHAR) Baslon-sella (BAS) Basisphenoid (BASISPH)

Plane connecting

Presphenoid (PRESPH) Sella (S) Naslon (N) Sphenoid (SPHEN) Orbital (ORB) Sella-Nasion (SN)

Endocranial Pharyngeal

magnum

projection of the anterior border of the foramen magnum through the inferior contour of the foramen (Bjork. 1955). opisthion

surface

(endobasion)

with basion

of the basl-occipital

surface of the basio-occipital

Plane connecting

to the tangent

bone

excluding

bone (Koskl.

dorsum

sellae (Koskl.

1973).

1973).

basion with sella.

Plane connecting the most postero-superior portion of the midsphenoidal synchondrosls with the most antero-superior portion of the spheno-occipital synchondrosis. Endocranial

surface of the presphenoid

Most inferior portion (Ford, ‘56). Most anterior Horizontal

bone.

of the bony sella turcica

aspect of the nasofrontal

plane of the presphenoid

on a plane parallel

to foramen

magnum

suture (Bjork. ‘55).

bone posterior

to the zygoma (Koski,

1973).

Endocranial surface of the orbit defined by a plane tangent to the orbital roof and mtersetting the most superior point of the presphenoid bone (Modified from Koski. 1973). Plane connecting

sella with nasion.

both showed a stronger correlation (r > 0.65) with SN, perhaps Indicating a generalized correlation of the structures of the anterior portion of the cranial base and to some extent reflecting the mathematical influence of the length of the SN plane (Solow, 1966). Cephulometric superimpositions To better understand the gross morphologic manifestations of the angular data, cross-sectional cephalometric radiographs of specimens from Groups I, III and VI were superimposed. As there is no known “best” reference point, films were superimposed on four separate structures. Figure 3 shows a typical superimposition. On basisphenoid. Enlargement of the basisphenoid was greater in the caudal-rostra1 direction in Groups I and III and greater supero-inferiorly in the older group. In the younger specimens, the midsphenoidal synchondrosis had a much more acute angular relationship to the inferior border. The spheno-occipital synchondrosis in each age group retained the same approximate relationship to the inferior border. Extensive elongation occurred in the basi-occipital bone with relatively more growth on the ventral clivus than on the dorsal clivus, the latter being transformed from a convex to a slightly concave surface. These two factors caused the long axis of the basioccipital bone to be slightly less obtuse endocranially relative to the basisphenoid. The superior endocranial surface of the presphenoid bone and the spheno-ethmoidal plane showed a postero-superior enlargement relative to the inferior presphenoid, especially in the younger ages. On spheno-ethmoidal plane. With increasing age, the

-

nasal bone moved antero-superiorly and the orbital roof became less acutely convex endocranially. especially superior to the spheno-frontal suture. On caudal spheno-okipital synchondrosis. The decrease of endocranial convexity with age, the linear increase and the formation of a more bulbous caudal tip of the basi-occipital bone are better illustrated with this superimposition. The width of the sphenooccipital synchondrosis, in contrast to the midsphenoidal, varied little with age. On rostra1 midsphenoidal synchondrosis. There was a decrease m the antero-posterior dimension of the midsphenoidal synchondrosis with time. especially in the younger age groups. Descriptive histolog) The cephalometric analyses demonstrated that. within the age range studied, certam structures showed marked morphologic alterations but others exhibited a fairlv consistent nattern throughout. To elucidate these changes more definitively, each structure (Text Fig. 4) will be described in detail for Group I and illustrated with typical photomicrographs of specimens processed by double-embedding (Plate Figs. 5-14). Where practical, subsequent age groups will be combined and only the pertinent alterations will be discussed. Group I (101-l 10 days). The basi-occipital bone. which was composed of woven bone with prominent osteocytes, showed generalized appositional activity. Although basion and the caudal dorsal clivus exhibited some osteoblastic activity (Plate Figs. 5 and 6). the rostra1 dorsal clivus (Plate Fig. 8) had a wider osteoid seam, indicating relatively more apposition.

60

R. N. Moore

Fig. 2. Calculated angles between radiographic planes depicted in Fig. 1. Asterisk greater These angles

than

were deleted

in subsequent

PRESPH SPHEN ORB SN PRESPH SPHEN ORB SN

BASISPH

23

PRESPH

with

SPHEN

PRESPH

24

PRESPH

wtth

ORB

SPHEN

25

PRESPH

with

ORB SN BASISPH

26 27 *28

ORB ORB SPHEN

with with with

BAS PHAR BASISPH PRESPH SPHEN ORB SN PHAR

with with with

12

BAS

with

13 14

BAS PHAR

with with

The ventral clivus showed the opposite pattern in that caudally there were closely approximated osteoblasts (Plate Fig. 7) and a more prominent osteoid seam than rostrally. The latter exhibited a smooth, lamellar-type bone, which was, in many places, devoid of cells. The area of the ventral clivus nearest the spheno-occipital synchondrosis (Plate Fig. 9) had a

I

20.5 18.5 17.4 15.4 18.1 18.2

II III IV V VI

Differences

f + + + + +

CLIVUS/ BASISPH

2.6 155.2 + 2.0 5.3 165.5 + 4.2 2.0 157.6 + 2.5 1.9 162.4 + 1.9 1.6 161.7 + 1.8 2.9 160.7 + 2.7 between

age groups

relationship

SN SPHEN SN SN

scalloped surface suggestive of resorption, although there were few osteoclasts in this area. Morphologically, the midsphenoidal and sphenooccipital synchondroses (Plate Fig. 10) were composed of a central core of single chondrocytes which peripherally became hypertrophic and aggregated into long columns perpendicular to the margin of the

of radiographic

planes (mean degrees

&SE.)

CLIVUS/ PRESPH

CLIVUS/ SPHEN

CLIVUS/ ORB

BASISPH/ PRESPH

PRESPH/ ORB

20.8 23.5 26.4 30.8 30.6 25.5

131.2 138.2 137.5 143.9 144.7 137.0

163.8 166.8 167.8 170.2 170.4 169.9

45.7 38.0 48.8 48.4 48.9 44.8

37.0 36.7 38.7 40.7 40.2 35.6

f 3.9 &- 4.8 + 2.2 + 1.3 + 1.4 k 2.4

+_ 3.2 f. 3.8 + 1.5 f 2.1 k 1.6 + 3.4

were not statistically

error

calculations. with with with with with with with with

with with with with with with with with

CLIVUS/ PHAR

with technique

PHAR PHAR PHAR PHAR BASISPH BASISPH BASISPH BASISPH

CLIVUS CLIVUS CLIVUS CLIVUS CLIVUS CLIVUS CLIVUS BAS BAS BAS BAS

Group

angles

15 16 17 18 19 *20 *21 *22

*1 2 3 4 5 6 7 8 9 10 11

Table 3. Angular

denotes

5 per cent.

4 f + & + f

significant

6.5 1.6 1.7 2.4 1.9 4.0

k + f + f +

3.2 0.9 2.1 1.4 1.2 2.3

f + + + f k

for any angle (p < 0.05).

4.6 3.6 1.9 1.8 1.3 4.2

BAS/ SN 151.7 155.7 158.2 160.6 159.1 155.1

+_ 3.3 + 3.8 2 1.1 + 1.9 + 1.5 + 3.7

61

Foetal macaque cranial base Table 4. Correlation

of radiographic Pearson

CLIVUS

0.001 0.001 0.009 0.001 0.034 0.025 0.009

planes, Groups correlation

PHAR

BAS

BASISPH

0.932

0.938 0.917 -

0.001 0.008 0.001 0.030 0.028 0.002

0.001 0.001 0.026 0.005 0.001

bone with the cartilage. Along the superior and inferior extremes of these margins, the cell columns became more acutely angulated to the bone and radiated toward the periphery. This pattern was especially characteristic of the spheno-occipital synchondrosis. Generally, the dorsum sellae was composed of smgle, small chondrocytes. Near the basisphenoid bone, the chondrocytes became more hypertrophic and were arranged in pairs with an occasional column of four cells. The inferior border of the bony sella showed more prominent osteoblastic activity on its anterior (rostral) than on its posterior (caudal) end (Plate Fig. 11). The rostra1 inferior border of the basisphenoid bone showed a more prominent osteoid seam than did the caudal aspect. Osteoblastic activity with some osteoid seam formation was evident on the endocranial surface of the presphenoid bone (Plate Fig. 12). The jugum sphenoidale and spheno-ethmoid plane both exhibited a marked osteoid seam in some areas, but in others there was less cellular activity. indicatmg the possibility that this region was undergoing differential morphological alteration. The orbital roof (Plate Fig. 14), especially superior to the spheno-frontal suture, consistently showed

III-V

coefficients

(131-160 days) (r)

PRESPH

SPHEN

ORB

SN

0.457 0.460 0.603 -

0.593 0.554 0.667 0 678

0.001 0.010 0.001 0.001

0.375 0.384 0.392 0.447 0.417

0.018 0.001 0.001

0.398 0.389 0.482 0.560 0.553 0.506

0.453 0.521 0.547 0.635 0.554 0.658 0.731

0.003 0.001

0.001

bone formation on the endocranial surface and resorption on the ocular surface. Similarly, the intrasutural surfaces of the spheno-frontal suture (Plate Fig. 13) had resorption on the ocularly-facing surface and apposition on the endocranially-facing surface. The cribriform plate was composed of prominent chondrocytes surrounded by fibrous connective tissue and traversed by the large olfactory nerve fibres. The nasal bone was characterized by osteoid seam on all surfaces with the anterior slightly more prominent than the posterior. Group I (121-130 days). The caudal surface of the dorsal clivus appeared to be more lamellar. Moving rostrally, the surface progressively showed more of an osteoid seam with numerous large. prominent osteoblasts and an occasional cell within the osteoid seam itself. The caudal ventral clivus was also lined with elongated, closely-spaced cells, some embedded partially or completely within the seam. Rostrally, the ventral clivus resembled the younger specimens with a lamellar-type bone showing few osteoblasts and some lacunae and osteoclasts. Basion (Plate Fig 5) showed the marked transition from dorsal to ventral with lamellar bone in the superior quarter and osteoid seam inferiorly. Group III (131-140 days). The caudal dorsal clivus I* I/\

ri*7

/-

Fig. 3. Cephaiometric superimpositions. Group I (101-l 10 days) -; Group III (131-140 days) ‘. ‘; Group VI (161-170 days) ----. Superimposed on (a) basisphenoid at sella, (b) spheno-ethmoid plane, (c) caudal spheno-occipital synchondrosis, (d) rostra1 midsphenoidal synchondrosis.

62

R. N. Moore

Fig. 4. Schematic drawing showing relative positions of Figs. 5-14 on foetal M. nemesrrinn cranial base. (Plate Fig. 6) was much more acellular, being characterized by lamellar bony surfaces lined by sparse, elongated cells with hyperchromatic nuclei, or. toward the caudal end, by osteoclasts in lacunae. The rostra1 end continued to exhibit a prominent osteoid seam (Plate Fig. 8). Groups IV-VI (141-170 days). These groups were combined as they all showed different degrees of the same morphological pattern. The caudal portion of the dorsal clivus showed progressively increasing resorption with lamellar bone continuing further rostrally than before. The osteoid seam extended much further rostrally along the ventral clivus than in earlier age groups and ended abruptly near the spheno-occipital synchondrosis where the bony surface became scalloped with numerous osteoclasts. Both the anterior portions of the floor of sella (Plate Fig. 11) and the inferior border of the basisphenoid bone showed more prominent osteoblasts and had more osteoid seam than their respective posterior parts. Although the entire endocranial surface of the presphenoid was still appositional (Plate Fig. 12), the superior aspect exhibited more cells than the inferior presphenoid, suggesting relatively more growth activity in a postero-superior direction.

DlSCUSSlON

The information gained from the cephalometric and histologic analyses is summarized schematically in Text Fig. 15. The changes in shape of the basi-occipita1 bone, which become more endocranially concave and elongated with time, were achieved by bony apposition at basion, spheno-occipital synchondrosis, rostra1 dorsal clivus and caudal ventral clivus. Concomitantly, there was resorption along the caudal dorsal clivus and rostra1 ventral clivus. These data are in contrast to those for one-day old Macacn mulatta labelled in uiuo with tetracycline reported by Michejda (1971) where the entire basi-occipital bone was depicted as being appositional. However, six month and older M. mulatta showed a resorptive pattern along the entire dorsal clivus (Lager, 1958; Michejda, 1971). The progressive caudal to rostra1 resorptive pattern of the dorsal clivus seen with increasing age in my study suggests that both

Fig. 15. Characteristic histologic alteration of foetal M. nemestrina cranial base with increasing gestational age. Size of arrows indicates relative activity. Solid arrows, apposition; hollow arrows, resorption; dot, activity greater in ammals younger than 130 days; X activity greater in animals older than 130 days. Unlabelled arrows denote activity that IS relatively constant throughout the age range 101-170 days. M. mulatta and M. nemestrina have a similar resorptive pattern. The basisphenoid bone showed an overall appositional trend with the rostra1 portion of the inferior border and the floor of sella being greater khan the caudal (Plate Fig. 11). This morphology and that of the sellar-synchondrosal cartilage of the basisphenoid bone were very similar to those described by Latham (1972) for the human foetus. Thus the postero-superior movement of the hypophysis with age reported by Latham probably occurs in M. nemestrina. This movement is relatively small and would only slightly lessen the measured cranial base angle. Cephalometric superimpositions suggested that the histologically-observed differential apposition of the basisphenoid resulted in caudal-rostra1 elongation with concomitant dorsal-ventral thickening. The increase in the caudal-rostra1 dimension was accompanied by a decrease in width of the midsphenoidal synchondrosis with little change m the spheno-occipital synchondrosis. In an attempt to correlate the cephalometric changes with endochondral bone formation in the synchondroses, the height of the chondrocytic columns of representative areas of the spheno-occipital and midsphenoidal synchondroses were measured with an ocular micrometer (Moss-Salentijn, 1974). In most age groups, the rostra1 end of the midsphenoidal synchondrosis had the longest column length. Similar findings were reported by Michejda (1971) for oneday old M. mulatta. In M. nemestrina, however, variability was large and no definitive quantitative trend was apparent. Such a lack of relationship between basi-cranial angles and the morphology of the synchondroses and bone has been reported in young pigs and rabbits (Hoyte, 1973a, b). Apparently the midsphenoidal synchondrosis plays a more active role in bony adjustment in younger than in older animals. The cephalometric superimpositions (Text Fig. 3) showed that the change of the basi-sphenoid-presphenoid relationship was greater

Foetal macaque cranial base from Group I to Group III than from Group III to Group VI. Similarly, there was a strong linear association (Table 4) between these two bones in the combined Groups III-V. suggesting some stability at the midsphenoidal synchondrosis in the older specimens. At this stage in Group III the sagittal profile of the basi-occipital bone began to change. Thus with mcreasmg age there appears to be a transition in influence on the shape of the crania1 base from the mldsphenoldal area to the basi-occipital. Michejda ( 1972) observed a similar decrease in midsphenoidal endochondral activity and an increase in that of the spheno-ocapital synchondrosis. Histologically. the presphenoid bone, caudal spheno-ethmoid plane, nasal bone and endocranial surface of the orbital roof displayed appositional activity throughout and so confirmed the cephalometric superimpositions (Text Fig. 3) which demonstrated a marked supero-posterior movement of these bones relative to the dorsal clivus. The similar pattern of movement suggests a close association in growth pattern of these component structures of the anterior cramal base. As the amount of postero-superior movement of the presphenoid bone relative to the dorsal chvus detected cephalometrically in earlier gestational age groups was greater than expected from the amount of endocranial bony apposition observed histologically, it appears that a portion of the change was due to the relative movement of the bone across the synchondroses. Such an interpretation is consistent with the concept of growth activity at the midsphenoidal synchondrosis. In the human foetus, Ford (1956) found an increase in the cramal base angle (measured to the floor of .the hypophyseal fossa) from 134’ to 149” from 10 to 40 lunar weeks of gestation. Other investigations of more limited age ranges using the centre of the fossa (Burdi, 1965, Kvinnsland, 1973) and Bolton pomt (Levlhn. 1967) confirm the overall increase. In contrast, foetal M. nemesrrina (Table 3) has a cranial base angle of approximately 155-160” which is more obtuse than the most comparable measurement .of 149’ at 40 weeks of gestation in man. This acuteness of the cranial base angle in the human foetus is also confirmed by extrapolation from the data presented by Moss and Greenberg (1955). The approximate equivalent of the CLIVUS/SPHEN angle in the human newborn would be 121” vs approximately 140” in the foetal M. nemestrina. Similarly, the equivalent of the CLIVUS/ORB angle would be 152” vs approximately 170”. The cranial base angle in the human foetus shows no statistically significant correlation with crownrump length (Burdi, 1965, 1969; Birch, 1968; Houpt, 1970). Similarly. the angle BAS/SN (Table 3) in foetal M. nemestrina showed no statistically significant correlation w& foot length. As in man (Inoue, 1961: Houpt. 1970). the foetal non-human primate has no statlstlcally significant sex differences for any angular measurements. In contrast to the human foetal studies (Ford, 1956; Levihn. 1967; Burdi, 1965, 1969; Kvinnsland, 1971, 1973) where the cranial base angle increased throughout gestation, the BASjSN angle in M. nemestrina showed no specific trend. Some of the changes in angular measurements with age (Table 3) were un-

63

doubtedly due to changes in the shape of the basioccipital bone, different rates of remodelling of the basisphenoid and presphenoid bones, and some relative changes of the bones across synchondroses. In addition, antero-superior movement of the nasal bone partially compensated for the inferior movement of the remodelling basi-occipital bone and, as a consequence, the BAS/SN angle remained relatively stable. This apparent stability may be a consequence of the relatively short age range studied and/or the limited sample size, as evidenced by the fact that Preston (1976) using a small foetal human sample was unable to demonstrate an increase in cranial base angle. Thus, although the cranial base angle of foetal M. netnestrina is more obtuse than in the human foetus. this species is a useful model for the study of prenatal craniofacial growth with relevance to man. A fundamental doubt concerning relevance is the fact that the midsphenoidal synchondrosis fuses at birth m man, but remains patent in non-human primates. Conceivably, this synchondrosis could be a site of crania1 base flexure which would not be relevant to human craniofacial growth (Scott, 1958). Acknowledgements--I gratefully acknowledge the valuable assistance of Dr. B. Moffett in preparation of this manuscript and Dr. C. Phdhps for statIstical consultation The support by USPHS Research Grants DE 02931 and DE 02918 abd the University of Washmgton Orthodontic Memorial Fund IS acknowledged. The study was based on a thesis submltted in partial fulfillment of the reqturements for the degree of Master of Science m Dentistry. Umversity of Washmgton REFERENCES

Baume L. J. 1968. Patterns of cephalofaclal growth and development. Int dent. J. 18, 489-513. Birch R. H. 1968. Foetal retrognathla and the cramal base Angle Orthod. 38, 231-235. Bjork A. 1955. Cranial base development Am. J. Or0tod 41, 198-225. Burdi A. R. 1965 Saglttal growth of the nasomaxillary complex during the second trlmester of human prenatal development. J. dent. Res. 44, 112-125. Burdi A. R. 1969. Cephalometric growth analyses of the human upper face region durmg the last two trlmesters of gestation. .4m. J Anat. 125, 113-122. Ford E. H. 1956. The growth of the foetal skull J. 4m. 90, 63-72

Ford E. H. 1958. Growth of the human cranial base. .-Zm J. Orthod. 44, 498-506. Houpt M. I. 1970. Growth of the cramofacial complex of the human fetus. Am. J. Orthod. 58, 373-383 Hoyte D. A N. 1973a. Basicranial elongation’ 2 Is there differenttal growth within a synchondrosls. Anat Ret 175, 374. Hoyte D. A N. 1973b. Basicramal elongation: 3 Differential growth between synchondroses and baslon Proc 3rd Eur. Anat. Congr pp. 231-232. Inoue N. 1961. A study of the developmental changes of dentofaclal complex durmg fetal period by means of roentgenographic cephalometrics. Bull Tokyo Med Dent. Unrr. 8, 205-227. Johnston L. E. 1974. A cephalometric mvestlgation of the sagittal growth of the second-trimester fetal face Allat Rec. 178, 623-630. Kobayashi S. and Inoue N. 1961. RadiologIcal observation on the development and growth of the Japanese fetal cramum. Bull. Tokyo Med Dent. (Iniv. 8, 165-190

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Koskl K. 1973. Variabdity of the craniofacial skeleton. Am J. Orrhod. 64, 188-196. Kvinnsland S. 1971. The saglttal growth of the foetal cranial base. :cra odont. stand. 29, 699-715. Kvinnsland S. 1973. Changes in the foramen magnum axis durmg human foetal life. Acfa odonr. stand. 31, 175-I 78. Lager H. 1958. A histological description of the crarual base in Macaca rhesus. Trans. Eur. Orthod. Sot. 4, 147-156. Latham R. A. 1972. The different relationshtp of the sella point to the growth sites of the cranial base in fetal hfe. J. dent. Res. 51, 16461650. Levihn W. C. 1967. A cephalometric roentgenographic cross sectional study of the cramofacial complex m fetuses from twelve weeks to birth. Am. J. Orthod. 53, 822-848. Mestre J. C. 1959. A cephalometric appraisal of cranial and facial relationships at various stages of human fetal development. Am. J. Orthod. 45, 473. Michejda M. 1971. Ontogenic changes of the cranial base in Macaca mulatta: histologic study. Proc. 3rd Int. Congr. Primatol. 1, 215-225. Michejda M. 1972. The role of basicranial synchondroses m flexure processes and ontogenetic development of the skull base. Am. J. Phys. Anthrop. 37. 143-150. Molnar L. M. 1974. Double embedding with nitrocellulose and paraffin. Stain Techno/. 49. 311.

Molnar L. M. 1975a. Modification of Harris’ hematoxylin for sectlons from tissue double embedded wrth nitrocellulose and paraffin. Histologic 5, 59. Molnar L. M. 1975b. Modification of Verhoeff’s elstlc stain for sections from tissue double embedded with nrtrocellulose and paraffin. Histologic 5, 64. Molnar L. M. 1975~. Decalcifying solution for hard or soft tissue. Hislologic 5, 71. Molnar L. M. 1976a. Modification of Mallory’s aniline blue collagen stain. Histologic 6, 78. Molnar L. M. 1976b. New method for perlochc-acid Schlffs and alclan blue staining procedure. Histologic. 6, 87 Moss M. L. and Greenberg S. N. 1955 Postnatal growth of the human skull base. Angle Orthod. 25, 77-84. Moss-Salentijn L. 1975. Studies of long bone growth. 1. Determination of differential elongation in paired growth plates of the rat. Acta anat. 90, 145-160. Preston C. B. 1976. A cephalometric study of foetal skull. J. dent. Ass. S. Ajii. 31, 65-69. Scott J. H. 1958. The cranial base. Am. J Pkps. Anthrop 16, 319-348. Solow B. 1966. The pattern of craniofacial association. Acta odont. stand. Suppl. 46. Vinkka H., Koski K. and McNamara J. 1975. Variability of the craniofacial skeleton. III. Radiographic cephalometry of juvenile Macara mulatta. Am. J. Orthod. 68. 1-7.

Foetal macaque cranial base

Plate 1 overleaf

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Plate 1 Fig. 5. Basion (151-160 days). The superior quarter of basion exhibited bony resorption and numerous osteoclasts.(oc). Inferiorly, there was an abrupt change to bony apposition with osteoid seam formation (OS)and numerous osteoblasts (ob). Haematoxylin and eosin. x 320 Fig. 6. Caudal dorsal clivus (131-140 days). While more rostra1 portions of the dorsal clivus had a lamellar endocranial surface (1) lined by only a few osteoblasts (ob), the caudal portion showed a more irregular, resorptive surface (r) and occasional osteoclasts (oc). Haematoxylin and eosin. x 320 Fig. 7. Caudal ventral clivus (131-140 days). This surface of the basi-occipital bone displayed continued bony apposition as evidenced by the numerous osteoblasts (ob) and prominent osteoid seam (OS). Haematoxylin and eosin. x 200 Ftg. 8. Rostra1 dorsal clivus (131-140 days). Bony apposition on this surface was stmilar to that seen on the caudal ventral clivus (Fig. 9) with numerous osteoblasts (ob) and moderate osteoid seam (OS). The fact that the osteoid seam of the rostra1 dorsal clivus was narrower than that of the caudal ventral clivus suggests less rapid bone formation on the former. Haematoxyhn and eosin. x 200 Fig. 9. Rostra1 ventral clivus (131-140 days). The irregularly shaped outhne and the presence of numerous osteoclasts (oc) indicated that this surface near the spheno-occipital synchondrosis was undergoing marked resorptton. Haematoxylin and eosin. x 200 Fig. 10. Superior portion of caudal spheno-occipital synchondrosis (151-160 days). Synchondroses were composed of a central core of single or double chondrocytes (c) which pertpherally became hypertrophic and aggregated into long columns (hc). Along the superior (shown here) and inferior extremes of the bone-cartilage margin the cell columns became more acutely angulated to the bone and radiated peripherally. Haematoxylin and eosin. x 320 Fig. Il. Floor of hypophyseal fossa (151-160 days). Differential appositton m the anterior (rostral) portion (a) of the fossa was evidenced by the presence of more osteoblasts (ob) and a slightly wider osteoid seam than were seen in the posterior (caudal) area (p). Haematoxylin and eosin. x 405 Fig. 12. Superior presphenoid (151-160 days). Generalized bony apposition was observed on this surface as indicated by the numerous osteoblasts (ob) and prominent osteoid seam (OS). The osteoid seam was narrower than that seen in Figs. IO and 1I, suggesting that its rate of apposition was relatively less. Haematoxylin and eosin. x 320 Fig. 13. Sphenofrontal suture (151-160 days). The intrasutural morphology is similar to that of the orbital roof. The ocularly-facing surface (0) has a resorptive pattern with numerous osteoclasts (oc). The endocranially-facing surface is appositional with a prominent osteoid seam (OS). Haematoxylin and eosin. x 200 Fig. 14. Orbital roof (131-140 days). The ocular surface (0) showed resorptive activity with numerous osteoclasts (oc) while the endocranial surface (e) was characterized by osteoblasts (ob) and generalized osteoid seam formation (OS).Haematoxylin and eosin x 200

Foetal macaque cranial base

Plate 1