Mechanical modulation of vertebral and tibial growth: diurnal versus full-time loading

The aim of this study was to determine whether the amount of growth response to mechanical compression and the underlying mechanism differed with night-time or day-time loading, relative to full time loading. Mechanical compression (nominally 0.1 MPa stress) was applied across tibial and tail vertebral growth plates of growing Sprague-Dawley rats. Four groups of animals were tested: 24/24 hour (full-time loading); 12/24 hour (day-loading); 12/24 hour (night-loading); and 0/24 hour (sham instrumented), 4 or 5 animals per group. After 8 days animals were euthanized and the growth plates were processed for quantitative histology of loaded and within-animal control growth plates to measure 24-hour growth, total and BrdU-positive proliferative zone chondrocyte counts, and hypertrophic chondrocyte enlargement in the growth direction.

RESULTS

Growth as a percentage of within-animal control averaged 82% (full-time); 93% (day-loading); 90% (night-loading); 100% (sham) for vertebrae. For proximal tibiae it averaged 70% (full-time); 84% (day-loading); 86% (night-loading); 89% (sham). Reduced amount of hypertrophic chondrocytic enlargement explained about half of this effect in full-time compressed growth plates, but was not significantly altered in half-time loaded growth plates. The remaining variation in growth was apparently explained by reduced total numbers of proliferative zone chondrocytes. The BrdU labeling index demonstrated an opposite trend, which was not statistically significant. In half-time loaded growth plates the proliferative zone cell count change predominated.

The pathogenesis of idiopathic scoliosis: uncoupled neuro-osseous growth?

This paper examines the following speculative hypothesis: "that in some patients with scoliosis there is disproportionate neuro-osseous growth--the longitudinal growth of the spinal cord fails to keep pace with the growth of the vertebral column and, as a consequence, the spine buckles into a scoliosis deformity". A literature review of the morphology and neurology of scoliosis does not deny the hypothesis. Several mechanisms are suggested as to why the spinal cord growth could become uncoupled from osseous growth.

Vertebral column and associated elements in dipnoans and comparison with other fishes: development and homology

A vertebral column consisting of a persistent notochord and ossified arcocentra is the primitive condition for Gnathostomata; it still persists in primitive actinopterygians and sarcopterygians. Advanced actinopterygians and sarcopterygians develop numerous types of centra that include, among others, the presence of holocentrum, chordacentrum, and autocentrum. The chordacentrum, a mineralization or calcification of the fibrous sheath of the notochord, is only found in actinopterygians, whereas an autocentrum is a synapomorphy of teleosts above Leptolepis coryphaenoides. The chordacentrum, formed by migration of cartilaginous cells from the arches into the fibrous sheath of the notochord and usually covered by a thin calcification, is a unique feature of chondrichthyans. The actinopterygian chordacentrum and the chondrichthyan chordacentrum are not homologous. The postcaudal cartilaginous centrum is only known in postcaudal vertebrae of living dipnoans. The holocentrum is present in certain fossil dipnoans and actinopterygians, where it has been independently acquired. It is formed by proliferation of cartilage cells around the elastica externa of the notochord. These cells later ossify, forming a compact centrum. A vertebral column formed by a persistent notochord without vertebral centra is the primitive pattern for all vertebrates. The formation of centra, which is not homologous among vertebrate groups, is acquired independently in some lineages of placoderms, most advanced actinopterygians, and some dipnoans and rhipidistians. Several series of structures are associated with the vertebral column such as the supraneurals, interhaemals, radials, and ribs. In living dipnoans median neural spine, "supraneural," and dorsal radial result from growth and distal differentiation of one median cartilage into two or three median bones during ontogeny. The median neural spine articulates with the neural arch and fuses with it in the caudal vertebrae early in ontogeny. Two bones differentiate in the anterior abdominal vertebrae, i.e., the proximal neural spine and the distal "supraneural." Three bones differentiate in front of the dorsal fin, i.e., the proximal neural spine, the middle "supraneural", and the distal radial; the same pattern is observed in front of the anal fin (the proximal haemal spine, the middle interhaemal, and the distal radial). Considering that the three dorsal (and also the three ventral) bones originate from growth of only one cartilage, they cannot be serial homologs of the neural spines, or "supraneural." They are linear homologs of the median neural cartilage in living dipnoans. The development of these elements differs within osteichthyans from sarcopterygians to actinopterygians, in which the neural spine originates as a continuation of the basidorsal arcualia and in which the supraneural and radial originate from independent cartilages that appear at different times during early ontogeny. The ribs of living dipnoans are unique in that they are not articulated with parapophyses, like in primitive fossil dipnoans, but a remnant of the ventral arcuale surrounded by a small arcocentrum remains at its base. A true caudal fin is absent in living dipnoans. The postcaudal cartilages extend to the caudal tip of the body separating dorsal and ventral rays (or the camptotrichia). Actinotrichia are present in young dipnoans. They are also known in extant actinistians and actinopterygians. They probably represent the primitive state for teleostomes. In contrast, the camptotrichia are unique for extant dipnoans (and probably Carboniferous and younger dipnoans). Lepidotrichia apparently developed many times among osteichthyans.

Vertebral age changes in Japanese macaques

This study deals with maturation and aging of the vertebrae in Japanese macaques (Macaca fuscata fuscata) of known chronological age. The samples used were 103 skeletons of captive raised Japanese macaques varying in age from 6-23 years. Epiphyseal union between the vertebral body and the epiphyseal disk (epiphyseal ring, annular epiphysis) and degenerative changes of the vertebrae were macroscopically examined. It was revealed that vertebral epiphyseal union develops comparatively rapidly in the sacral and cervical vertebrae, moderately in the lumbar vertebrae, and slowly in the thoracic vertebrae. It was found that, as a central tendency, the vertebral epiphyseal union begins at about 6 years of age, progresses lineally in proportion to age, and completes at about 23 years of age. However, considerable variation in developmental states of union was observed among individuals of the same age. Concerning vertebral degenerative changes, few were observed among the present samples. Compared with the other primates with regard to the timing of vertebral maturation, shortening of duration of maturation was found among humans. Human vertebrae may have become an early-maturing organ in order to sustain the increased loading that is accompanied by the adoption of habitual erect posture and bipedal locomotion.

Critical ages and stages of puberty in the accumulation of spinal and femoral bone mass: the validity of bone mass measurements

In growing children, lumbar and femoral areal bone mineral density (aBMD), as measured by dual-energy X-ray absorptiometry (DXA), is influenced by skeletal growth and bone size. Correction of lumbar bone mineral density (BMD) for bone volume (volumetric BMD [vBMD]), by the use of mathematical extrapolations, reduces the confounding effect of bone size, but vBMD remains dependent on age and bone size during growth. Femoral (neck and mid-shaft) vBMD, assessed by DXA, is independent of age prior to puberty, but a slight increase occurs in late puberty and after menarche. Femoral (mid-shaft) cortical bone density and radial cortical and trabecular bone densities, assessed by quantitative computed tomography (QCT), show no peak during childhood or adolescence. Bone strength index, calculated by peripheral QCT, increases with age and correlates with handgrip strength, bone cross-sectional area and cortical area. Puberty is one of the main factors that influences lumbar bone mineral content and aBMD accumulation, but a high incidence of fractures occurs during this period of life, which may be associated with a reduced aBMD.

Growth hormone and segmental growth in survivors of head and neck embryonal rhabdomyosarcoma

AIMS

To assess the impact of treatment for embryonal rhabdomyosarcoma on spinal growth and limb length and examine the response of these parameters to growth hormone (GH) treatment.

METHODS

We conducted a retrospective case note review of 17 survivors of head and neck rhabdomyosarcoma followed up at a single institution. All children had been treated with chemotherapy and local radiotherapy. Growth velocity, height, sitting height, and subischial limb length SDS scores were analysed.

RESULTS

Growth failure secondary to isolated GH deficiency (GHD) developed in 7/17 patients. GHD occurred at a median (range) of 3.4 (1.3-9.9) years after radiotherapy tumour doses of 46 (40-50) Gy. Growth velocity, height, and subischial limb length SDS were significantly reduced in the GHD group and improved with GH therapy.

CONCLUSIONS

GH treatment resulted in a significant improvement in sitting height SDS. We discuss the unexpected improvement in spinal growth in survivors with GHD.

Axial and appendicular pneumaticity in Archaeopteryx

From the time of its discovery in 1860 to this day Archaeopteryx has been essential to our understanding of avian evolution. Despite the great diversity of plesiomorphic avialan (sensu Gauthier 1986) taxa discovered within the last decade, Archaeopteryx remains the most basal avialan taxon. A very unusual feature of extant birds is their lung structure, in which air diverticulae penetrate the bones. This has previously been reported in Archaeopteryx as well, in the cervical vertebrae of the Berlin specimen and in an anterior thoracal vertebra of the Eichstätt specimen. This indicates the presence of a cervical air sac. We show that the London specimen also has pneumatized anterior thoracal vertebrae, and, thus, that this feature was present in the most archaic avialans, as the London and Eichstätt specimens are different species. Furthermore, the pelvis of the London specimen shows clear signs of the presence of an abdominal air sac, indicating that at least two of the five air sacs present in modern birds were also present in Archaeopteryx. Evidence of pubic pneumaticity was also found in the same position in some extant ratites.

Heterogeneity in the growth of the axial and appendicular skeleton in boys: implications for the pathogenesis of bone fragility in men

Men with spine fractures have reduced vertebral body (VB) volume and volumetric bone mineral density (vBMD). Men with hip fractures have reduced femoral neck (FN) volume and vBMD, site-specific deficits that may have their origins in growth. To describe the tempo of growth in regional bone size, bone mineral content (BMC), and vBMD, we measured bone length, periosteal and endocortical diameters, BMC, and vBMD using dual-energy X-ray absorptiometry in 184 boys aged between 7 and 17 years. Before puberty, growth was more rapid in the legs than in the trunk. During puberty, leg growth slowed while trunk length accelerated. Bone size was more advanced than BMC in all regions, being approximately 70% and approximately 35% of their predicted peaks at 7 years of age, respectively. At 16 years of age, bone size had reached its adult peak while BMC was still 10% below its predicted peak. The legs accounted for 48%, whereas the spine accounted for 10%, of the 1878 g BMC accrued between 7 and 17 years. Peripubertal growth contributed (i) 55 % of the increase in leg length but 78% of the mineral accrued and (ii) 69% of the increase in spine length but 87% of the mineral accrued. Increased metacarpal and midfemoral cortical thickness was caused by respective periosteal expansion with minimal change in the endocortical diameter. Total femur and VB vBMD increased by 30-40% while size and BMC increased by 200-300%. Thus, growth builds a bigger but only slightly denser skeleton. We speculate that effect of disease or a risk factor during growth depends on the regions maturational stage at the time of exposure. The earlier growth of a regions size than mass, and the differing growth patterns from region to region, predispose to site-specific deficits in bone size, vBMD, or both. Regions further from their peak may be more severely affected by illness than those nearer completion of growth. Bone fragility in old age is likely to have its foundations partly established during growth.

Curve progression and spinal growth in brace treated idiopathic scoliosis

The risk of progression of idiopathic scoliosis is correlated primarily to factors that predict potential remaining skeletal growth. The aim of the current study was to evaluate spinal growth, measured as the length of the scoliotic spine on serial longitudinal radiographs, and its relationship to progression of the scoliotic curve. The retrospective study was based on measurements made on standing anteroposterior radiographs of 60 patients with adolescent idiopathic scoliosis. In all patients, a Boston brace was prescribed during the followup period. Despite brace treatment, a significantly greater average progression rate of the scoliotic curve was seen in periods of rapid to moderate growth (> or = 10 mm per year) compared with periods of small or no growth (< 10 mm per year). The difference in progression rates concerned the increase of the Cobb angle and the increase of lateral deviation and axial rotation. These findings indicate the length of the spine measured on subsequent radiographs is an excellent parameter to determine spinal growth and thus an excellent predictor of scoliosis progression. With the presented growth charts, which were derived from the measured individual growth velocity values of the patients in the study, it is possible to predict future spinal growth at different chronologic ages.

The association between athletic training time and the sagittal curvature of the immature spine

Strenuous physical activity is known to cause structural abnormalities in the immature vertebral body. Concern that exposure to years of intense athletic training may increase the risk for developing adolescent hyperkyphosis in certain sports, as well as the known association between hyperkyphosis and adult-onset back pain, led us to examine the association between cumulative hours of athletic training and the magnitude of the sagittal curvature of the immature spine. A sample of 2,270 children (407 girls and 1,863 boys) between 8 and 18 years of age were studied. An optical raster-stereographic method was used to measure the mid-sagittal curvatures of the surface of the back while the subject was in the upright standing position to quantify the angles of thoracic kyphosis and lumbar lordosis. These data were then correlated with self-reported hours of training measured by interview and questionnaire. The possible effects of age, sex, sport, and upper and lower body weight training were investigated. The results in these young athletes showed that larger angles of thoracic kyphosis and lumbar lordosis were associated with greater cumulative training time. Gymnasts showed the largest curves. Lack of sports participation, on the other hand, was associated with the smallest curves. Age and sex did not appear to affect the degree of curvature.

The aetiology of idiopathic scoliosis: biomechanical and neuromuscular factors

The aetiology of idiopathic scoliosis: biomechanical and neuromuscular factors small curve develops due to a small defect in the neuromuscular control system and a second stage during adolescent growth in which the scoliotic curve is exacerbated by biomechanical factors.

Evolutionary mechanisms of rib loss in anurans: a comparative developmental approach

ABSTRACT The presence of free ribs is presumed to be a primitive morphological character observed only in a few families of Recent anurans, whereas the absence of ribs has been considered to be a derived condition that is widespread within this order. A comparative study of rib development based on representatives of several anuran lineages (Alytes, Bombina, Bufo, Discoglossus, Hyla, Pelobates, Pelodytes, Rana, and Xenopus) reveals a previously undetected diversity of developmental features in the formation and interaction between neural arches and ribs. The absence of free ribs at premetamorphic or later stages is verified in some groups, but we present for the first time evidence of the existence of larval rib rudiments in others, both in the anterior (Rana, Hyla) and posterior (Bufo, Discoglossus, Pelobates) presacral regions. Heterochrony seems to have played a major role in the processes underlying rib reduction. The intracolumnar differences between anterior (V(2)-V(4)) and posterior (V(5)-V(8)) regions are based on perturbations in the timing of early differentiation. Furthermore, a clear shift in the relative timing of ossification among evolutionary lineages was detected. In this respect Xenopus has a highly derived condition. The use of the morphological character of "rib loss" in phylogenetic analyses must be reconsidered due to the different convergent developmental paths described here. The phylogenetic analysis of a "sequence units" matrix of rib development is compared with current anuran phylogenies. Some evolutionary information appears to be clearly present in the ontogenetic data of this "missing morphology," but its value for evolutionary inferences is rather limited.

The stimulation of vertebral and tibial bone growth by the parathyroid hormone fragments, hPTH-(1-31)NH2, [Leu27]cyclo(Glu22-Lys26)hPTH-(1-31)NH2, and hPTH-(1-30)NH2

The native human parathyroid hormone, hPTH-(1-84), and certain carboxyl truncated analogs such as hPTH-(1-34) and even smaller fragments such as hPTH-(1-31)NH2, [Leu27]cyclo(Glu22-Lys26)hPTH-(1-31)NH2, and hPTH-(1-30)NH2 stimulate femoral trabecular and cortical bone growth in ovariectomized (OVX) rats. Here we show that when injected once daily for 6 weeks starting 2 weeks after OVX in doses of 1 or 2 nmol/100 g of body weight, hPTH-(1-31)NH2, [Leu27] cyclo(Glu22-Lys26)hPTH-(1-31)NH2, and hPTH-(1-34)NH2 prevented the loss of trabecular volume in the L5 vertebrae induced by OVX. In fact, by the end of the sixth week of injections (i.e., the eighth week after OVX) the fragments had increased the volume and trabecular thickness significantly above the values in vehicle-injected sham-operated rats. hPTH-(1-30)NH2 can stimulate vertebral bone growth as much as the larger fragments, but 10-25 times more of it was needed to do so. The same daily doses of hPTH-(1-31)NH2, [Leu27]cyclo(Glu22-Lys26)hPTH-(1-31)NH2, and hPTH-(1-34)NH2 also raised the trabecular volume and thickness in the L5 vertebrae of rats well above the values in vehicle-treated animals when the injections were started 9 weeks after OVX. This restoration of trabecular bone in the L5 vertebrae in estrogen-deprived animals was accompanied by a significant increase in the bone mineral density (BMD) of the L1-L4 vertebrae and tibias. However, there was no significant drop in the pelvic BMD in the estrogen-deprived animals and the effects of hPTH-(1-31)NH2, [Leu27]cyclo(Glu22-(Lys) hPTH-(1-31)NH2, and hPTH-(1-34)NH2 on the pelvic BMD were equivocal.

Development of trunk asymmetry in a cohort of children ages 11 to 22 years

STUDY DESIGN

A cohort study with a follow-up period of 11 years.

OBJECTIVES

To study the growth of the spine with a focus on the development of trunk asymmetry and scoliosis.

SUMMARY OF BACKGROUND DATA

Trunk asymmetry, a common phenomenon at adolescence, can be considered the clinical expression of scoliosis. The importance of the pubertal growth spurt has been stressed in the natural history of scoliosis. However, no cohort studies have focused on the ascending and descending phase of the spine's peak growth and the development of trunk asymmetry.

METHODS

The cohort consisted of all the fourth-grade school children in the Western school district of Helsinki, Finland, in the spring of 1986. These 1060 children (515 girls and 545 boys), from the average age of 11 to 14 years, were invited to undergo annual examinations. The 855 children (80.7%) who had participated in the study at the age of 14 years were invited to a reexamination at the age of 22 years. This invitation was accepted by 430 (208 women and 222 men; 54%) of those invited. The forward bending test, the spinal pantography, and the anthropometric measurements were carried out by the same author (M.N.) throughout this study.

RESULTS

At 22 years of age, 30% of the adults were found to be symmetric, with a hump less than 4 mm in the forward bending test, whereas 51% had a hump of 4 to 9 mm, and 19% had a hump 10 mm or larger (major asymmetry). The directional asymmetry of trunk surface, a skew to the right at the thoracic level and to the left at the lumbar level at puberty, remained constant at adult age. The prevalence of major trunk asymmetry at adult age was the same in both women and men, in contrast to the female predominance at puberty in this cohort. There were close correlations in the degrees of thoracic and lumbar asymmetry between puberty and adult ages.

CONCLUSIONS

The shape of the back develops mainly during the pubertal growth spurt at ages 12 to 14 years in girls and boys. Trunk asymmetry (and mild scoliosis) seems as prevalent in young adult women as in men, although at puberty idiopathic scoliosis was twice as prevalent among girls as among boys in this cohort.

Mouse Ror2 receptor tyrosine kinase is required for the heart development and limb formation

BACKGROUND

A mouse receptor tyrosine kinase (RTK), mRor2, which belongs to the Ror-family of RTKs consisting of at least two structurally related members, is primarily expressed in the heart and nervous system during mouse development. To elucidate the function of mRor2, we generated mice with a mutated mRor2 locus.

RESULTS

Mice with a homozygous mutation in mRor2 died just after birth, exhibiting dwarfism, severe cyanosis, and short limbs and tails. Whole-mount in situ hybridization analysis showed that mRor2 was expressed in the branchial arches, heart and limb/tailbuds, in addition to the developing nervous system. The mutants had cardiac septal defects, mainly a ventricular septal defect. In addition, an examination of the skeletal systems revealed that the mutants had shorter limbs, vertebrae and facial structure, with a particular defect in their distal portions, and that almost no calcification was observed in their distal limbs. Histological examination showed abnormalities in the chondrocytes.

CONCLUSIONS

Our findings suggest that mRor2 plays essential roles in the development of the heart and in limb/tail formation, in particular cardiac septal formation and ossification of distal portions of limbs and tails.

A prospective study of quantitative ultrasound in children and adolescents

The accrual of optimal bone mass during childhood and adolescence is essential for the formation of a skeleton that will meet structural needs throughout life. Assessing bone health of children is becoming increasingly important in order to identify those who require interventions, and quantitative ultrasound (QUS) has appeal for these assessments. The purpose of this prospective study was to characterize changes in QUS values in 328 healthy children and adolescents over a 3-yr period. Measurements of QUS, height, weight, nutrient intake, fracture history, and Tanner stage were made at baseline and 3 yr later. Both females and males experienced significant increases in QUS values during the study. The rate of change of QUS peaked at an earlier age in females than in males, and maximum accumulation rates in both genders occurred at ages at which highest accumulation rates are seen with densitometry. Females exhibited higher QUS values than males during puberty, also similar to results for dual X-ray absorptiometry (DXA). This is the first report of prospective data of QUS in children and adolescents. Our findings that QUS values change during childhood and adolescence in a manner similar to DXA values, the "gold standard," provide support for the validity of using QUS to assess bone health in children and adolescents.

Description of the chondrocranium and osteogenesis of the Chacoan burrowing frog, Chacophrys pierotti (Anura: Leptodactylidae)

The larval chondrocranium of the large-headed leptodactylid frog, Chacophrys pierotti (Ceratophryinae), is described in detail. Descriptions include the ontogeny of the chondrocranium and osteogenesis of the cranial skeleton. The chondrocranium of C. pierotti is profoundly different from the chondrocrania previously described for the other genera of the Ceratophryinae (Ceratophrys and Lepidobatrachus). The chondrocranium of Chacophrys is longer than wide and not particularly robust or laterally expanded; that of Ceratophrys is very robust, whereas the chondrocranium of Lepidobatrachus is widely expanded laterally. These differences are particularly apparent in the elements associated with the jaw (i.e., suprarostral, infrarostral, Meckel's cartilage, palatoquadrate, cornua trabeculae), which are robust in Ceratophrys and thin and elongate in Lepidobatrachus. Unlike Ceratophrys and Lepidobatrachus, which possess highly specialized carnivorous larva, the chondrocranium of Chacophrys more closely resembles the typical microphagous herbivore morphology characteristic of other leptodactylid frogs for which the chondrocrania are known. These data suggest that Chacophrys is the basal taxon within the monophyletic Ceratophryinae. The ontogeny of the chondrocranium of Chacophrys, as well as the cranial ossification sequence, do not differ greatly from those described for Ceratophrys. Detailed descriptions of the ontogeny of the chondrocranium and the bony skeleton are needed for additional taxa within the Ceratophryinae (especially Lepidobatrachus). Such descriptive ontogenetic studies promise new insight into the phylogeny and morphological evolution of this remarkable group of large-headed frogs.

Pax1 and Pax9 synergistically regulate vertebral column development

The paralogous genes Pax1 and Pax9 constitute one group within the vertebrate Pax gene family. They encode closely related transcription factors and are expressed in similar patterns during mouse embryogenesis, suggesting that Pax1 and Pax9 act in similar developmental pathways. We have recently shown that mice homozygous for a defined Pax1 null allele exhibit morphological abnormalities of the axial skeleton, which is not affected in homozygous Pax9 mutants. To investigate a potential interaction of the two genes, we analysed Pax1/Pax9 double mutant mice. These mutants completely lack the medial derivatives of the sclerotomes, the vertebral bodies, intervertebral discs and the proximal parts of the ribs. This phenotype is much more severe than that of Pax1 single homozygous mutants. In contrast, the neural arches, which are derived from the lateral regions of the sclerotomes, are formed. The analysis of Pax9 expression in compound mutants indicates that both spatial expansion and upregulation of Pax9 expression account for its compensatory function during sclerotome development in the absence of Pax1. In Pax1/Pax9 double homozygous mutants, formation and anteroposterior polarity of sclerotomes, as well as induction of a chondrocyte-specific cell lineage, appear normal. However, instead of a segmental arrangement of vertebrae and intervertebral disc anlagen, a loose mesenchyme surrounding the notochord is formed. The gradual loss of Sox9 and Collagen II expression in this mesenchyme indicates that the sclerotomes are prevented from undergoing chondrogenesis. The first detectable defect is a low rate of cell proliferation in the ventromedial regions of the sclerotomes after sclerotome formation but before mesenchymal condensation normally occurs. At later stages, an increased number of cells undergoing apoptosis further reduces the area normally forming vertebrae and intervertebral discs. Our results reveal functional redundancy between Pax1 and Pax9 during vertebral column development and identify an early role of Pax1 and Pax9 in the control of cell proliferation during early sclerotome development. In addition, our data indicate that the development of medial and lateral elements of vertebrae is regulated by distinct genetic pathways.

[Spinal lipoma in children: analysis of magnetic resonance image for upward displacement of medullary-conus on 44 consecutive surgical cases]

Medullary conus-untethering operation was conducted on 52 infants with spinal lipoma. Magnetic resonance (MR) image was used in order to evaluate the untethering results in 44 out of these 52 patients who could be followed-up after Osaka Medical Center & Research Institute for Maternal & Child Health was opened. Talking into account the changes in vertebral body during the growth period of infants, the authors studied the upward displacement of the conus-lipoma interface by four fractional MR sagittal image, using the vertebral body-intervertebral disc space as the baseline. Upward displacement was confirmed in 27 of 44 (61.4%). The mean, median and trimmed mean of upward displacement were 1.78 +/- 0.80, 2.0, 1.70 fractions, respectively. Sixteen (59.3%) were caudal type, 10 (37.0%) were transitional type and 1 (3.7%) was dorsal type. By type of spinal lipoma, upward displacement was observed in 16 of 23 caudal type patients (69.6%), 10 of 16 transitional type patients (62.5%) and 1 of 5 dorsal type patients (20%). While the rate of upward displacement was almost equal between the caudal and transitional type, that of dorsal type was lower. However, statistical analysis for the difference in population percentage of the three groups showed that significant difference existed only in the caudal type group.

Occipital spine of Orthacanthus (Xenacanthidae, Elasmobranchii): structure and growth

The morphology of 16 occipital spines of the xenacanthid Orthacanthus from Upper Carboniferous deposits of Robinson (Kansas, USA), Nýran (Czech Republic) and Puertollano (Spain) is described. The nonreplaced spines reveal the growth pattern of the shark. Moreover, the relationship between growth and paleoenvironmental conditions can be used to determine paleoecological conditions. Both external and internal morphology indicate that the spine was superficially inserted in the skin. During growth, the spine moved from a deep position in the dermis, in which trabecular dentine is formed, to a more superficial location in which centrifugally growing lamellar dentine was formed. Centripetally growing lamellar dentine was deposited more slowly than the centrifugally growing dentine; it obliterated the pulp cavity. The denticles are independent dermal elements formed by a dermal papilla and secondarily attached by dentine to the spine proper. The number of denticles per annual cycle and the density of denticulation vary with the growth rate. Moreover, the ratio of length of denticulated region to total length of the spine changes throughout ontogeny. In consequence, those features cannot be used for systematic purposes without a careful analysis of the variability. Centrifugally growing lamellar dentine in spines from Robinson shows a regular alternation of layers, suggesting tidal conditions in the environment in which the sharks lived. Monthly and seasonal cycles also occur. Tidal (lunar) cyclicity is also observed in the denticles: size and distance between denticles increase and decrease gradually, forming waves that are considered seasonal and yearly cycles. The observed regularity could be related to the variation in calcium phosphate deposition following the cyclical changes in water temperature produced in the tidal zone. Monthly and seasonal cycles are the result of the interaction of the solar and tidal (lunar) cycles. The cyclical pattern of growth is used to determine the age and growth rates. Orthacanthus was a fast-growing shark like the Recent sharks Isurus, Mustelus, and Negaprion.

[Natural history of scoliosis from childhood to old age]

Idiopathic scoliosis arises at any age in childhood. Its increasing is usually progressive, following growth, with a peak at puberty. Well codified determining factors for severity are: age at beginning, angulation and bone maturation. Functional and consequential effects remain anyway limited. Many scoliosis increase in adult life, giving way to deterioration, prevailing at the lumbar level, with osteo-arthritic changes and typical patterns such as dislocation at the junctional areas. Functional repercussion may thus arise, mainly pain and, in severe thoracic scoliosis impairment of the pulmonary function. A special form of degenerative scoliosis may appear over 45 or 50 years of age with progressive backache and/or radicular pain.

[Treatment of idiopathic scoliosis in children during the growth period]

Idiopathic infantile and juvenile scoliosis have potential for extreme worsening. Orthopaedic treatment should be started as soon as the progressivity of the scoliosis is proven. In some infantile curves healing is possible, but in most cases the aim of the orthopaedic treatment will be to avoid spinal fusion at the end of growth. In some malignant infantile scoliosis, curves are rapidly out of the orthopaedic treatment control, and in such cases early surgery could be discussed.

Vertebral development and amphibian evolution

Amphibians provide an unparalleled opportunity to integrate studies of development and evolution through the investigation of the fossil record of larval stages. The pattern of vertebral development in modern frogs strongly resembles that of Paleozoic labyrinthodonts in the great delay in the ossification of the vertebrae, with the centra forming much later than the neural arches. Slow ossification of the trunk vertebrae in frogs and the absence of ossification in the tail facilitate the rapid loss of the tail during metamorphosis, and may reflect retention of the pattern in their specific Paleozoic ancestors. Salamanders and caecilians ossify their centra at a much earlier stage than frogs, which resembles the condition in Paleozoic lepospondyls. The clearly distinct patterns and rates of vertebral development may indicate phylogenetic separation between the ultimate ancestors of frogs and those of salamanders and caecilians within the early radiation of ancestral tetrapods. This divergence may date from the Lower Carboniferous. Comparison with the molecular regulation of vertebral development described in modern mammals and birds suggests that the rapid chondrification of the centra in salamanders relative to that of frogs may result from the earlier migration of sclerotomal cells expressing Pax1 to the area surrounding the notochord.

Mechanical modulation of growth for the correction of vertebral wedge deformities

This study tested the following hypotheses: (a) a vertebral wedge deformity created by chronic static asymmetrical loading will be corrected by reversal of the load asymmetry; (b) a vertebral wedge deformity created by chronic static asymmetrical loading will remain if the load is simply removed; and (c) vertebral longitudinal growth rates, altered by chronic static loading, will return to normal after removal of the load. An external fixator was used to impose an angular deformity (Cobb angle of 30 degrees) and an axial compression force (60% body weight) on the ninth caudal (apical) vertebra in two groups of 12 5-week-old Sprague-Dawley rats. This asymmetrical loading was applied to all rats for 4 weeks to create an initial wedge deformity in the apical vertebra. The rats from group I (load reversal) then underwent 1 week of distraction loading followed by 4 weeks of asymmetrical compressive loading with the imposed 30 degree Cobb angle reversed. The rats from group II (load removal) had the apparatus removed and were followed for 5 weeks with no external loading. Weekly radiographs were obtained and serial fluorochrome labels were administered to follow vertebral wedging. After the initial 4-week loading period, the combined average wedge deformity that developed in the apical vertebra of the animals in both groups was 10.7 +/- 4.4 degrees. The group that underwent load reversal showed significant correction of the deformity with the wedging of the apical vertebra decreasing to, on average, 0.1 +/- 1.4 degrees during the 4 weeks of load reversal. Wedging of the apical vertebra in the group that underwent load removal significantly decreased to 7.3 +/- 3.9 degrees during the first week after removal of the load, but no significant changes in wedging occurred after that week. This indicated a return to a normal growth pattern following the removal of the asymmetrically applied loading. The longitudinal growth rate of the apical vertebra also returned to normal following removal of the load. Vertebrae maintained under a load of 60% body weight grew at a rate that was 59.4 +/- 17.0% lower than that of the control vertebrae, whereas after vertebrae were unloaded their growth averaged 102.4 +/- 31.8%. These findings show that a vertebral wedge deformity can be corrected by reversing the load used to create it and that vertebral growth is not permanently affected by applied loading.