“Lucy” (A.L. 288‐1) had five sacral vertebrae

A “long‐backed” scenario of hominin vertebral evolution posits that early hominins possessed six lumbar vertebrae coupled with a high frequency of four sacral vertebrae (7:12‐13:6:4), a configuration acquired from a hominin‐panin last common ancestor (PLCA) having a vertebral formula of 7:13:6‐7:4. One founding line of evidence for this hypothesis is the recent assertion that the “Lucy” sacrum (A.L. 288‐1an, Australopithecus afarensis) consists of four sacral vertebrae and a partially‐fused first coccygeal vertebra (Co1), rather than five sacral vertebrae as in modern humans. This study reassesses the number of sacral vertebrae in Lucy by reexamining the distal end of A.L.288‐1an in the context of a comparative sample of modern human sacra and Co1 vertebrae, and the sacrum of A. sediba (MH2). Results demonstrate that, similar to S5 in modern humans and A. sediba, the last vertebra in A.L. 288‐1an exhibits inferiorly‐projecting (right side) cornua and a kidney‐shaped inferior body articular surface. This morphology is inconsistent with that of fused or isolated Co1 vertebrae in humans, which either lack cornua or possess only superiorly‐projecting cornua, and have more circularly‐shaped inferior body articular surfaces. The level at which the hiatus' apex is located is also more compatible with typical five‐element modern human sacra and A. sediba than if only four sacral vertebrae are present. Our observations suggest that A.L. 288‐1 possessed five sacral vertebrae as in modern humans; thus, sacral number in “Lucy” does not indicate a directional change in vertebral count that can provide information on the PLCA ancestral condition. Am J Phys Anthropol 156:295–303, 2015. © 2014 Wiley Periodicals, Inc.     

Evaluation of "unique" aspects of human vertebral bodies and pedicles with a consideration of Australopithecus africanus

Recent functional studies of human vertebrae have revealed that loads borne by the axial skeleton during bipedal postures and locomotion pass through the pedicles and posterior elements as well as through the bodies and discs. Accordingly, particular morphological attributes of these vertebral elements have been linked exclusively with bipedalism. In order to test the validity of current form-function associations in human vertebral anatomy, this study considers the morphology of human thoracolumbar vertebral bodies and pedicles in the context of a wide comparative primate sample. The last lumbar vertebra of STS 14 (Australopithecus africanus) is also included in the analysis. Results indicate that certain features of human vertebrae previously thought to reflect bipedalism are characteristic of several nonhuman primates, including those whose posture is habitually pronograde. These features include the decrease in vertebral body surface area and the increase in cross-sectional area of the pedicle between the penultimate and last lumbar vertebra. In addition, although humans have relatively large and wide last lumbar pedicles, the enlargement and widening of the pedicle between the penultimate and last lumbar vertebra is not unique to humans. On the other hand, human vertebrae do exhibit several unique adaptations to bipedal posture and locomotion: (1) the vertebral body surface areas of the lower lumbar vertebrae and the cross-sectional areas of the last lumbar pedicles are large relative to body size, and (2) the last lumbar pedicles are wider relative to length and to body size than are those of nonhuman primates. The last lumbar vertebra of STS 14 does not exhibit any of these human-like vertebral features—its pedicles and body surface areas are relatively small, and its pedicles are not relatively wide, but relatively short.     

Morphological Features of Adult Rats of IS/Kyo and IS-Tlk/Kyo Strains with Lumbar and Caudal Vertebral Anomalies

IS-Tlk/Kyo, a mutant derived from IS/Kyo strain, exhibits a kinked and/or short tail, in addition to the congenital lumbar vertebral anomaly. Homozygotes of Tlk dominant gene are known to die during embryonic development. We previously reported the morphological features of the skeleton in IS/Kyo and IS-Tlk/Kyo fetuses and of the heart in IS/Kyo fetuses [19]. This study was conducted to clarify the morphological features of the skeleton in both adult rats and of the heart in adult IS/Kyo rats. Ventricular septal defect (VSD) was observed in 3 out of 10 IS/Kyo rats. Neither splitting of lumbar vertebra and supernumerary rib (in both strains) nor fused or absent caudal cartilage (in IS-Tlk/Kyo strain) was detected in adult rats. Fusion of lumbar vertebrae was observed in almost all specimens together with lumbarization of sacral vertebrae in a few specimens in both adult rats as well as fusion of sacral and caudal vertebrae only in adult IS-Tlk/Kyo rats. In addition, a severe reduction in the ossified sacral and caudal vertebrae was noted in adult IS-Tlk/Kyo rats (mean number: 20.6) and IS/Kyo rats (31.8), and the difference was similar to that in the length of sacral and caudal vertebrae. These results suggest that the Tlk gene may be involved in both the congenital and acquired abnormal formation of the lower vertebral centra as well as the persistent occurrence of VSD by the background gene in IS/Kyo strain.     

Some physiological and developmental considerations of the temperature-gradient hypothesis of bone marrow distribution

In adult humans, active bone marrow is confined to the proximal portion of the skeleton. Huggins and Blocksom (J. Exp. Med., 64: 253, '36) concluded that a high temperature is needed for hematopoiesis in rats. However, precise thermal regulation of human marrow was not found (Petrakis, J. Appl. Physiol., 4: 549, '52). Because these experiments made on the rat tail are the basis for a commonly accepted hypothesis attempting to explain marrow distribution in man, it was considered of importance to re-examine the caudal vertebra model upon which the temperature-gradient hypothesis is based. The sacral and coccygeal vertebrae were examined in rats, mice and humans with respect to marrow cellularity and temperature. In rats and mice and man it was observed that the transition between hematopoietically-active and inactive (fatty) vertebral marrow cavities is abrupt, occurring at the level of the first and second caudal and coccygeal vertebrae. All vertebrae distal to this point have fatty marrow. Of significance was the finding that the vertebral and coccygeal temperatures, as measured with a thermister needle, remain unaltered over this area of changing cellular activity. These anatomical and thermal observations of the caudal vertebrae of rats, mice, and humans indicate that the use of the tail as an experimental model does not support the hypothesis that temperature is a primary factor in the physiological maintenance of hematopoiesis in bone marrow. The possible relationship of hematopoietic activity to developmental and other factors peculiar to the caudal vertebra model is under study.     

Computer-Assisted Radiographic Calculation of Spinal Curvature in Brachycephalic “Screw-Tailed” Dog Breeds with Congenital Thoracic Vertebral Malformations: Reliability and Clinical Evaluation

The objectives of this study were: To investigate computer-assisted digital radiographic measurement of Cobb angles in dogs with congenital thoracic vertebral malformations, to determine its intra- and inter-observer reliability and its association with the presence of neurological deficits. Medical records were reviewed (2009–2013) to identify brachycephalic screw-tailed dog breeds with radiographic studies of the thoracic vertebral column and with at least one vertebral malformation present. Twenty-eight dogs were included in the study. The end vertebrae were defined as the cranial end plate of the vertebra cranial to the malformed vertebra and the caudal end plate of the vertebra caudal to the malformed vertebra. Three observers performed the measurements twice. Intraclass correlation coefficients were used to calculate the intra- and inter-observer reliabilities. The intraclass correlation coefficient was excellent for all intra- and inter-observer measurements using this method. There was a significant difference in the kyphotic Cobb angle between dogs with and without associated neurological deficits. The majority of dogs with neurological deficits had a kyphotic Cobb angle higher than 35°. No significant difference in the scoliotic Cobb angle was observed. We concluded that the computer assisted digital radiographic measurement of the Cobb angle for kyphosis and scoliosis is a valid, reproducible and reliable method to quantify the degree of spinal curvature in brachycephalic screw-tailed dog breeds with congenital thoracic vertebral malformations.     

Vertebrae numbers of the early hominid lumbar spine

General doctrine holds that early hominids possessed a long lumbar spine with six segments. This is mainly based on Robinson's (1972) interpretation of a single partial Australopithecus africanus skeleton, Sts 14, from Sterkfontein, South Africa. As its sixth last presacral vertebra exhibits both thoracic and lumbar characteristics, current definitions of lumbar vertebrae and lumbar ribs are discussed in the present study. A re-analysis of its entire preserved vertebral column and comparison with Stw 431, another partial A. africanus skeleton from Sterkfontein, and the Homo erectus skeleton KNM-WT 15000 from Nariokotome, Kenya, did not provide strong evidence for the presence of six lumbar vertebrae in either of these early hominids. Thus, in Sts 14 the sixth last presacral vertebra has on one side a movable rib. In Stw 431, the corresponding vertebra shows indications for a rib facet. In KNM-WT, 15000 the same element is very fragmentary, but the neighbouring vertebrae do not support the view that it is L1. Although in all three fossils the transitional vertebra at which the articular facets change orientation seems to be at Th11, this is equal to a large percentage of modern humans. Indeed, a modal number of five lumbar vertebrae, as in modern humans, is more compatible with evolutionary principles. For example, six lumbar vertebrae would require repetitive shortening and lengthening not only of the lumbar, but also of the entire precaudal spine. Furthermore, six lumbar vertebrae are claimed to be biomechanically advantageous for early hominid bipedalism, yet an explanation is lacking as to why the lumbar region should have shortened in later humans. All this raises doubts about previous conclusions for the presence of six lumbar vertebrae in early hominids. The most parsimonious explanation is that they did not differ from modern humans in the segmentation of the vertebral column.     

Age estimation from stages of epiphyseal union in the presacral vertebrae

The presacral vertebrae have various secondary centers of ossification, whose timing of fusion can be used for age estimation of human skeletal remains up to the middle to the latter third decade. However, detailed information about the age at which these secondary centers of ossification fuse has been lacking. In this study, the timing of epiphyseal union in presacral vertebrae was studied in a sample of modern Portuguese skeletons (57 females and 47 males) between the ages of 9 and 30, taken from the Lisbon documented skeletal collection. A detailed photographic record of these epiphyses and the age ranges for the different stages of epiphyseal union are provided. Partial union of epiphyses was observed from 11 to 27 years of age. In general, centers of ossification begin to fuse first in the cervical and lumbar vertebrae, followed by centers of ossification in the thoracic region. The first center of ossification to complete fusion is usually that of the mammillary process in lumbar vertebrae. This is usually followed by that of the transverse process, spinous transverse process, and annular ring, regardless of vertebra type. There were no statistically significant sex differences in timing of fusion, but there was a trend toward early maturation in females for some vertebra or epiphyses. Bilateral epiphyses did not show statistically significant differences in timing of fusion. This study offers information on timing of fusion of diverse epiphyseal locations useful for age estimation of complete or fragmented human skeletal remains. Am J Phys Anthropol, 2011. © 2010 Wiley‐Liss, Inc.     

Characterization of a novel insertional mouse mutation, kkt: A closely linked modifier of Pax1

We describe a novel transgene insertional mouse mutant with skeletal abnormalities characterized by a kinked tail and severe curvature of the spine. The disrupted locus is designated kkt for "kyphoscoliosis kinked tail." Malformed vertebrae including bilateral ossification centers and premature fusion of the vertebral body to the pedicles are observed along the vertebral column, and the lower thoracic and lumbar vertebrae are the most affected. Some of the homozygous kkt neonates displayed two backward-pointing transverse processes in the sixth lumbar vertebra (L6) that resembled the first sacral vertebra, and some displayed one forward- and one backward-pointing transverse process in L6. The fourth and fifth sternebrae were also fused, and the acromion process of the scapula was missing in kkt mice. The skeletal abnormalities are similar to those observed in the mouse mutant undulated (un). The transgene is integrated at the distal end of chromosome 2 close to the Pax1 gene, as revealed by FISH analysis. However, mutation of the Pax1 gene is responsible for the un phenotype, but the Pax1 gene in the kkt mice is not rearranged or deleted. Pax1 is expressed normally in kkt embryos and in the thymus of mature animals, and there is no mutation in its coding sequence. Thus, the skeletal abnormalities observed in the kkt mutant are not due to a lack of functional Pax1. Mouse genomic sequences flanking the transgene and PAC clones spanning the wild-type kkt locus have been isolated, and reverse Northern analysis showed that the PACs contain transcribed sequence. Compound heterozygotes between un and kkt (un(+/-)/kkt(+/-)) display skeletal abnormalities similar to those of un or kkt homozygotes, but they have multiple lumbar vertebrae with a split vertebral body that is more severe than in homozygous un or kkt neonates. Furthermore, the sternebrae are not fused and no backward-pointing transverse processes are detected in L6. It is therefore apparent that these two mutations do not fully complement each other, and we propose that a gene in the kkt locus possesses a unique role that functions in concert with Pax1 during skeletal development.     

Axial and appendicular skeletal transformations, ligament alterations, and motor neuron loss in Hoxc10 mutants

Vertebrate Hox genes regulate many aspects of embryonic body plan development and patterning. In particular, Hox genes have been shown to regulate regional patterning of the axial and appendicular skeleton and of the central nervous system. We have identified patterning defects resulting from the targeted mutation of Hoxc10, a member of the Hox10 paralogous family. Hoxc10 mutant mice have skeletal transformations in thoracic, lumbar, and sacral vertebrae and in the pelvis, along with alterations in the bones and ligaments of the hindlimbs. These results suggest that Hoxc10, along with other members of the Hox10 paralogous gene family, regulates vertebral identity at the transition from thoracic to lumbar and lumbar to sacral regions. Our results also suggest a general role for Hoxc10 in regulating chondrogenesis and osteogenesis in the hindlimb, along with a specific role in shaping femoral architecture. In addition, mutant mice have a reduction in lumbar motor neurons and a change in locomotor behavior. These results suggest a role for Hoxc10 in generating or maintaining the normal complement of lumbar motor neurons.     

Reevaluation of the lumbosacral region of Oreopithecus bambolii

Functional interpretations of the postcranium of the late Miocene ape Oreopithecus bambolii are controversial. The claim that Oreopithecus practiced habitual terrestrial bipedalism is partly based on restored postcranial remains originally recovered from Baccinello, Tuscany ( Köhler and Moyà-Solà, 1997). The lower lumbar vertebrae of BA#72 were cited as evidence that Oreopithecus exhibits features indicative of a lordotic lumbar spine, including dorsal wedging of the vertebral bodies and a caudally progressive increase in postzygapophyseal interfacet distance. Here, we demonstrate why the dorsal wedging index value obtained by Köhler and Moyà-Solà (1997) for the BA#72 last lumbar vertebra is questionable due to distortion in that region, present a more reliable way to measure postzygapophyseal interfacet distance, and include an additional metric (laminar width) with which to examine changes in the transverse dimensions of the neural arches. We also quantify the external morphology of the BA#72 proximal sacrum, which, despite well-documented links between sacral morphology and bipedal locomotion, and excellent preservation of the sacral prezygapophyses, first sacral vertebral body, and right ala, was not evaluated by Köhler and Moyà-Solà (1997). Measures of postzygapophyseal interfacet distance and laminar width on the penultimate and last lumbar vertebrae of BA#72 reveal a pattern encompassed within the range of living nonhuman hominoids and unlike that of modern humans, suggesting that Oreopithecus did not possess a lordotic lumbar spine. Results further show that the BA#72 sacrum exhibits relatively small prezygapophyseal articular facet surface areas and mediolaterally narrow alae compared with modern humans, indicating that the morphology of the Oreopithecus sacrum is incompatible with the functional demands of habitual bipedal stance and locomotion. The Oreopithecus lumbosacral region does not exhibit adaptations for habitual bipedal locomotion.     

High assimilation of the sacrum in a sample of American skeletons: Prevalence,pelvic size,and obstetrical and evolutionary implications

High assimilation sacrum is fusion of the caudal‐most lumbar vertebra to the first sacral vertebra. Previous studies have shown that high assimilation is associated with clinical problems, including obstetrical difficulty. This study used adult American males (n = 1,048) and females (n = 1,038) of the Hamann–Todd and Terry skeletal collections to determine the prevalence of high assimilation and its effect on pelvic size, and to consider the obstetrical and evolutionary implications of high assimilation. The prevalence of high assimilation in this sample is 6.3%, with males and females not differing significantly from one another in their prevalence. This prevalence is near the median for that reported in 41 other samples. In both males and females, individuals with high assimilation have significantly longer anteroposterior and posterior sagittal diameters of the inlet, and shorter sacrum compared to those with a nonassimilated sacrum. Females with high assimilation have a significantly narrower sacral angulation (i.e., reduced inclination of ventral axis of sacrum), and shorter posterior sagittal diameter of the outlet compared to those with a nonassimilated sacrum. A short posterior sagittal diameter of the outlet is associated with childbirth difficulty. As high assimilation is partial homeotic transformation of a lumbar vertebra, this study supports previous research that homeotic transformation of vertebrae is selectively disadvantageous. Am J Phys Anthropol, 2009. © 2008 Wiley‐Liss, Inc.     

Chronology of fusion of the primary and secondary ossification centers in the human sacrum and age estimation in child and adolescent skeletons

Little is known about fusion times of the primary and secondary centers of ossification in the sacrum, particularly from dry bone observations. In this study, the timing of union of these centers was studied in a sample of modern Portuguese skeletons (90 females and 101 males) between the ages of 0 and 30 years, taken from the Lisbon documented skeletal collection. A three‐stage scheme was used to assess fusion status between ossification centers as unfused, partially fused and completely fused. Posterior probability tables of age, given a certain stage of fusion, were calculated for most anatomical locations studied using both reference and uniform priors. Partial union of primary centers of ossification was observed from 1 to 8 years of age and partial union of secondary centers of ossification was observed from 15 to 21 years of age. The first primary centers of ossification to complete fusion are the neural arch with the centrum of the fifth sacral vertebrae and the last are the costal element with the centrum of the first sacral vertebra. The annular and sacroiliac epiphyses are the first, among the secondary centers of ossification observed, to complete fusion, after which the lateral margin fuses. This study offers information on timing of fusion of diverse locations in the developing sacrum useful for age estimation of complete or fragmented immature human skeletal remains and fills an important gap in the literature, by adding to previously published times of fusion of primary and secondary ossification centers in this sample. Am J Phys Anthropol 153:214–225, 2014. © 2013 Wiley Periodicals, Inc.     

Placement of the diaphragmatic vertebra in catarrhines: implications for the evolution of dorsostability in hominoids and bipedalism in hominins

A fundamental adaptation to orthograde posture and locomotion amongst living hominoid primates is a numerically reduced lumbar column, which acts to stiffen the lower back and reduce injuries to the intervertebral discs. A related and functionally complementary strategy of spinal stability is a caudal position of the diaphragmatic vertebra relative to the primitive condition found in nonhominoid primates and most other mammals. The diaphragmatic vertebra marks the transition in vertebral articular facet (zygapophysis) orientation, which either resists (prediaphragmatic) or allows (postdiaphragmatic) trunk movement in the sagittal plane (i.e., flexion and extension). Unlike most mammals, which have dorsomobile spines (long lumbar columns and cranially placed diaphragmatic vertebrae) for running and leaping, hominoids possess dorsostable spines (short lumbar columns and caudally placed diaphragmatic vertebrae) adapted to orthogrady and antipronogrady. In contrast to humans and other extant hominoids, all known early hominin partial vertebral columns demonstrate cranial displacement of the diaphragmatic vertebra. To address this difference, variation in diaphragmatic placement is assessed in a large sample of catarrhine primates. I show that while hominoids are characterized by modal common placement of diaphragmatic and last rib-bearing vertebrae in general, interspecific differences in intraspecific patterns of variation exist. In particular, humans and chimpanzees show nearly identical patterns of diaphragmatic placement. A scenario of hominin evolution is proposed in which early hominins evolved cranial displacement from the ancestral hominid condition of common placement to achieve effective lumbar lordosis during the evolution of bipedal locomotion.     

Brace technology thematic series: the dynamic derotation brace

Background

The curveback lineage of guppy is characterized by heritable idiopathic-type spinal curvature that develops during growth. Prior work has revealed several important developmental similarities to the human idiopathic scoliosis (IS) syndrome. In this study we investigate structural and histological aspects of the vertebrae that are associated with spinal curvature in the curveback guppy and test for sexual dimorphism that might explain a female bias for severe curve magnitudes in the population.

Methods

Vertebrae were studied from whole-mount skeletal specimens of curved and non-curved adult males and females. A series of ratios were used to characterize structural aspects of each vertebra. A three-way analysis of variance tested for effects of sex, curvature, vertebral position along the spine, and all 2-way interactions (i.e., sex and curvature, sex and vertebra position, and vertebra position and curvature). Histological analyses were used to characterize micro-architectural changes in affected vertebrae and the intervertebral region.

Results

In curveback, vertebrae that are associated with curvature demonstrate asymmetric shape distortion, migration of the intervertebral ligament, and vertebral thickening on the concave side of curvature. There is sexual dimorphism among curved individuals such that for several vertebrae, females have more slender vertebrae than do males. Also, in the region of the spine where lordosis typically occurs, curved and non-curved females have a reduced width at the middle of their vertebrae, relative to males.

Conclusions

Based on similarities to human spinal curvatures and to animals with induced curves, the concave-convex biases described in the guppy suggest that there is a mechanical component to curve pathogenesis in curveback. Because idiopathic-type curvature in curveback is primarily a sagittal deformity, it is structurally more similar to Scheuermann kyphosis than IS. Anatomical differences between teleosts and humans make direct biomechanical comparisons difficult. However, study of basic biological systems involved in idiopathic-type spinal curvature in curveback may provide insight into the relationship between a predisposing aetiology, growth, and biomechanics. Further work is needed to clarify whether observed sex differences in vertebral characteristics are related to the female bias for severe curves that is observed in the population.     

Kyphectomy for severe kyphosis with pyogenic spondylitis associated with myelomeningocele: a case report

A 32-year-old woman was referred to our hospital for a refractory ulcer on her back. She had a history of myelomeningocele with spina bifida that was treated surgically at birth. The ulcer was located at the apex of the kyphosis. An X-ray film revealed a kyphosis of 154° between L1 and 3 and a scoliosis of 60° between T11 and L5. Computed tomography, magnetic resonance imaging and laboratory data indicated the presence of a pyogenic spondylitis at L2/3. To correct the kyphosis and remove the infected vertebrae together with the skin ulcer, kyphectomy was performed. Pedicle screws were inserted from T8 to T12 and from L4 to S1. The dural sac was transected and ligated at L2, followed by total kyphectomy of the L1-L3 vertebrae. The spinal column was reconstructed by approximating the ventral wall of the T12 vertebral body and the cranial endplate of the L4 vertebra. Postoperatively, the kyphosis was corrected to 61° and the scoliosis was corrected to 22°. In the present case, we treated the skin ulcer and pyogenic spondylitis successfully by kyphectomy, thereby, preventing recurrence of the ulcer and infection, and simultaneously obtaining sufficient correction of the spinal deformity.     

Morphology and Function of the Vertebral Column in Remingtonocetus domandaensis (Mammalia, Cetacea) from the Middle Eocene Domanda Formation of Pakistan

The archaeocete family Remingtonocetidae is a group of early cetaceans known from the Eocene of India and Pakistan. Previous studies of remingtonocetids focused primarily on cranial anatomy due to a paucity of well-preserved postcranial material. Here we describe the morphology of the known vertebral column in Remingtonocetus domandaensis based largely on a single well-preserved partial skeleton recovered from the upper Domanda Formation of Pakistan. The specimen preserves most of the precaudal vertebral column in articulation and includes seven complete cervical vertebrae, ten partial to complete thoracic vertebrae, six complete lumbar vertebrae, and the first three sacral vertebrae. Cervical centra are long and possess robust, imbricating transverse processes that stabilized the head and neck. Lumbar vertebrae allowed for limited flexibility and probably served primarily to stabilize the lumbar column during forceful retraction of the hind limbs. Vertebral evidence, taken together with pelvic and femoral morphology, is most consistent with interpretation of Remingtonocetus domandaensis as an animal that swam primarily by powerful movement of its hind limbs rather than dorsoventral undulation of its body axis.     

Analysis of variability in vertebral morphology and growth ring counts in two Carcharhinid sharks

Inter- and intra-regional variations in vertebrae morphology and growth increment counts (band counts) were analyzed for two carcharhinid shark species, Carcharhinus plumbeus (n = 10) and C. limbatus (n = 11). Five sequential vertebrae were removed from the cervical region, above the branchial chamber and posterior to the chondrocrainium, and thoracic region, below the first dorsal fin. Dorsal–ventral height, medial–lateral breadth, and caudal–cranial length were measured for each sampled vertebra. Results indicate no significant difference in vertebral morphology within a sampled region of the vertebral column. However, a significant difference in vertebral morphology was noted between regions for both shark species, with thoracic vertebrae consistently larger than cervical vertebrae. A sub-set of three vertebrae was taken from each sampled region of each shark for sectioning and counting of growth increments. Analyses of growth increment counts by two readers indicated no significant difference in band counts within and between sampled regions.