Postnatal maturation of the sternum in a Portuguese skeletal sample: a variable ossification process.

The timing of skeletal maturation is one of the common indicators used to estimate age at death of juvenile skeletal remains. Skeletal maturation of the sternum has received less attention than other anatomical locations, and there is a general lack of detailed information about the fusion timing in the dry sternum that can be used for the estimation of age. The objective of this study is to document the age variation in the fusion of the body sternebrae, and both clavicular and intercostal notches. A three stage scale scheme was used (unfused elements, partial, and complete fusion) to quantify fusion of primary and secondary ossification centres in a sample of 68 individuals of both sexes from the identified skeletal collection housed at the National Museum of Natural History and Science in Lisbon, Portugal. Analysis was performed only for the pooled sex sample due to small sample size. Wide age intervals were obtained for fusion stages at all of the sternal centres. Primary ossification centres start to fuse between 1 and 27 years of age, with sternebrae 3 and 4 completing their fusion first. Secondary ossification centres fuse between 5 to 25 years of age. Results reflect considerable variability among individuals in the maturation of the sternum.

Calcium affects sternal mass by effects on osteoclast differentiation and function in meat ducks fed low nutrient density diets.

Genetic progress and increasing nutrient density for greater body mass and meat yield in poultry has inadvertently led to an imbalance between pectorales mass and sternal development which may or may not be detrimental to productivity and welfare. Slowing weight gain while promoting bone mineralization could positively influence sternal health. Thus, the present study aimed to evaluate the effect of graded calcium (Ca) supplementation in low nutrient density (LND) diets on sternal mass and bone turnover in meat ducks. Male meat ducks (720, 15-day-old) were randomly assigned and fed a standard nutrient density positive control (PC) diet, and 4 LND diets with 0.5, 0.7, 0.9, and 1.1% Ca, respectively. Metabolic energy (ME) was reduced in the LND by 9.5 and 16.3% at 15-35 D and 36-56 D compared to PC diet, respectively, while maintaining proportionate essential nutrient proportions to energy similar as in the PC diet. Although the 0.9% Ca LND diet decreased body weight and sternal dimension, it increased the relative sternum weight, the trabecular bone volume/tissue volume (BV/TV) and Ca content of the sternum compared with PC diet. Feeding 0.7% or more Ca with the LND diet significantly increased the mineral content, bone density, BV/TV, and trabecular number of the sternum for 49-days-old ducks. Furthermore, the LND diet with 0.7% or more Ca-increased osteocyte-specific gene mRNA and osteoprotegerin (OPG) expression, and it blocked the expression of cathepsin K and decreased osteoclasts number per bone surface. Tartrate-resistant acid phosphatase (TRAP) staining also revealed that the addition 0.7% or more Ca to the LND diet significantly decreased the number of osteoclasts compared with the 0.5% Ca LND diet. Meanwhile TRAP activity in serum was significantly decreased in 0.7% or more Ca-treated groups. We concluded that LND diet with 0.7% or more Ca may maintain optimal sternal mass through suppressing bone resorption for meat duck.

MDCT evaluation of sternal development.

BACKGROUND AND PURPOSE: Sternal ossification starts in utero, and continues throughout puberty in various patterns. In this study, our objective was to evaluate the correlation of ossification with age and to determine whether age can be predicted. MATERIALS AND METHODS: Individuals younger than 30 years old without congenital anomalies, chronic disease, and history of long-term chemotherapy who had chest CT imaging with a slice thickness < 3 mm were retrospectively reviewed. Data of ossification centers, horizontal and vertical fusion were collected. Spearman correlation test and ROC analysis were performed to correlate age with fusion. Kruskal-Wallis test was used to perform gender wise comparisons. Sensitivity, specificity, positive predictive value and negative predictive value of cut-off points, estimated according to ROC analysis, were calculated. RESULTS: Segmented ossification centers were more common in males, with significant difference in third and fourth mesosternal ossification centers (p < 0.05). Females had more vertical fusion at each level (p < 0.05). Spearman correlation test showed significant correlation between age and horizontal and vertical fusion for both genders. ROC analysis was performed and cut-off values were estimated. Sensitivity was very high (84.6-100%) but specificity was low (43.3-79.9%) for horizontal fusion. Sensitivity of vertical fusion (64.8-100%) was similar but specificity was higher (74.7-100%). CONCLUSIONS: Horizontal and vertical fusions of sternal ossification centers correlate with age significantly. Vertical fusion might be a better indicator of age with higher sensitivity and specificity, while horizontal fusion has lower accuracy. Large-scale studies should be conducted to confirm our results.

Forensic age-at-death estimation from the sternum in a black South African population.

Age-at-death estimation is a crucial component of any forensic anthropological analysis. Despite a variety of research in this field, uncertainties still exist when estimating adult age. The sternum is an under-considered element in terms of adult age estimation. Previous research on an Indian population suggested that this may be a usable region of the skeleton, although results were ambivalent. This study observed the fusion phases of 461 sterna from a black South African population in an attempt to match true age of an individual with the different phases of synostosis of the manubrio-sternal and the sterno-xiphoidal junctions. The results demonstrated that the majority of sterna remain unfused throughout adult life, with complete fusion observed both in young (25 year-old) and old individuals. Significant differences were identified amongst male and female sterna, with males presenting no transitional fusion of the segments, while female sterna demonstrated fusion to a lesser extent. Overall, logistic regression results demonstrated low accuracies (62.5%) for age estimation even when the two sexes were considered separately (male=63.9%; female=61.8%). The synostosis of both junctions is hence considered highly variable and deemed unreliable for adult age-at-death estimation in the black South African population.

A study on the sternum growth and mineralization kinetic of meat duck from 35 to 63 days of age.

The sternum as an important part of the skeleton and not only provides a crucial attachment site for the pectoral muscles and protects internal organs such as the heart and lungs for meat duck, but may also be considered as the primary ventilator in the avian respiratory system. Therefore, this study focuses on the sternum growth and mineralization kinetics of ducks from 35 d to 63 d of age. A total of 72 one-d-old males and 72 females were chosen and fed with the same diet until the age of 9 weeks. The sternum and serum were harvested at 35 d, 42 d, 49 d, 56d, and 63 d of feeding. Results showed that the sternum width rapidly grew from 35 d to 42 d and the value changed little after 42 d, while the keel length and the sternum depth did not significantly change until 49 d age. The sternum defatted weight and density increased assumed to "S" with ducks' age and their plateau in the 56 d. The sternum ash content, calcium (Ca), and phosphate (P) levels increased with duck age, then all three reached a plateau in 49 days. Similarly, serum alkaline phosphatase (ALP) activity was higher in the ducks at both 35 and 42 days, followed by 49 days, and the value was lowered to a minimum on both days 56 and 63. Conversely, serum tartrate resistant acid phosphatase (TRAP) activity substantially increased until 49 days irrespective of duck gender. Results indicate that the dimensions of the sternum were already at the maximum in 49-day-old ducks and the sternum of the ducks rapidly mineralized from 42 d to 49 d of age and achieved a plateau phase after 49-days resulting from the high activity of ALP at the sternum early mineralization.

Effects of enhancing vitamin D status by 25-hydroxycholecalciferol supplementation, alone or in combination with calcium and phosphorus, on sternum mineralisation and breast meat quality in broilers.

1. The aim of the present study was to examine the effects of improving vitamin D status in broiler diets by supplementary 25-hydroxycholecalciferol (25OHD3), alone or in combination with calcium (Ca) and available phosphorus (aP), on live performance, sternum mineralisation and breast meat quality in broilers. 2. A total of 936 1-d-old Ross 308 broilers were used in the study. After gender determination at the hatchery, chicks from each sex were randomly distributed into three dietary treatments. The following dietary treatments were used in the experiment from hatch to 38 d: (1) A control diet formulated to meet all of the nutrient requirements of broiler chicks according to the management guide; (2) The control diet supplemented with 18.7-15.0 µg/kg of 25OHD3; and (3) The control diet supplemented with 18.7-15.0 µg/kg of 25OHD3 plus Ca + aP. 3. Improvement in vitamin D status by 25OHD3 supplementation, alone or in combination with Ca and aP, had no effect on body weight and feed conversion ratio of broilers. 4. The serum 25OHD3 concentration significantly increased with 25OHD3 and 25OHD3 plus Ca + aP supplementation (P < 0.05), whereas the ionised Ca and Mg concentrations remained unchanged. 5. Sternum absolute weight, ash content and the concentrations of Ca and P significantly increased (P < 0.01) with supplementation of 25OHD3, alone or in combination with Ca + aP. 6. Supplemental 25OHD3, alone or in combination with Ca + aP, slightly increased pH24 (P = 0.05) and decreased (P < 0.01) squeezable water loss in breast meat, whereas it had no significant effect on lightness, yellowness and sarcoplasmic protein solubility. 7. In conclusion, the results suggested that enhancing vitamin D status by 25OHD3 supplementation alone or in combination with Ca + aP may improve sternum structure and mineral accretion. Furthermore, supplemental 25OHD3, even in a nutritionally complete diet, may offer an effective way to improve protein solubility in female broilers.

Evolution and functional significance of derived sternal ossification patterns in ornithothoracine birds.

The midline pattern of sternal ossification characteristic of the Cretaceous enantiornithine birds is unique among the Ornithodira, the group containing birds, nonavian dinosaurs and pterosaurs. This has been suggested to indicate that Enantiornithes is not the sister group of Ornithuromorpha, the clade that includes living birds and their close relatives, which would imply rampant convergence in many nonsternal features between enantiornithines and ornithuromorphs. However, detailed comparisons reveal greater similarity between neornithine (i.e. crown group bird) and enantiornithine modes of sternal ossification than previously recognized. Furthermore, a new subadult enantiornithine specimen demonstrates that sternal ossification followed a more typically ornithodiran pattern in basal members of the clade. This new specimen, referable to the Pengornithidae, indicates that the unique ossification pattern observed in other juvenile enantiornithines is derived within Enantiornithes. A similar but clearly distinct pattern appears to have evolved in parallel in the ornithuromorph lineage. The atypical mode of sternal ossification in some derived enantiornithines should be regarded as an autapomorphic condition rather than an indication that enantiornithines are not close relatives of ornithuromorphs. Based on what is known about molecular mechanisms for morphogenesis and the possible selective advantages, the parallel shifts to midline ossification that took place in derived enantiornithines and living neognathous birds appear to have been related to the development of a large ventral keel, which is only present in ornithuromorphs and enantiornithines. Midline ossification can serve to medially reinforce the sternum at a relatively early ontogenetic stage, which would have been especially beneficial during the protracted development of the superprecocial Cretaceous enantiornithines.

Morphometric analysis of variation in the sternum with sex and age.

Age and sex-related variations in sternum morphology may affect the thoracic injury tolerance. Male and female sternum size and shape variation was characterized for ages 0-100 from landmarks collected from 330 computed tomography scans. Homologous landmarks were analyzed using Procrustes superimposition to produce age and sex-specific functions of 3D-sternum morphology representing the combined size and shape variation and the isolated shape variation. Significant changes in the combined size and shape variation and isolated shape variation of the sternum were found to occur with age in both sexes. Sternal size increased from birth through age 30 and retained a similar size for ages 30-100. The manubrium expanded laterally from birth through age 30, becoming wider in relation to the sternal body. In infancy, the manubrium was 1.1-1.2 times the width of the sternal body and this width ratio increased to 1.6-1.8 for adults. The manubrium transformed from a circular shape in infancy to an oval shape in early childhood. The distal sternal body became wider in relation to the proximal sternal body from birth through age 30 and retained this characteristic throughout adulthood. The most dramatic changes in sternum morphology occur in childhood and young adulthood when the sternum is undergoing ossification. The lesser degree of ossification in the pediatric sternum may be partly responsible for the prevalence of thoracic organ injuries as opposed to thoracic skeletal injuries in pediatrics. Sternum fractures make up a larger portion of thoracic injury patterns in adults with fully ossified sternums. The lack of substantial size or shape changes in the sternum from age 30-100 suggests that the increased incidence of sternal fracture seen in the elderly may be due to cortical thickness or bone mineral density changes in the sternum as opposed to morphological changes.

Evaluation of the postnatal development of the sternum and sternal variations using multidetector CT.

PURPOSE: We aimed to evaluate the postnatal development and the maturation of the sternum and sternal variations using multidetector computed tomography (MDCT). Additionally, we aimed to examine the roles of gender and age in sternal development. MATERIALS AND METHODS: Two hundred and fifty patients who underwent thorax MDCT examinations were evaluated for sternal development and variations. Coronal curved planar reconstruction and maximum intensity projection images were used to better assess the ossification centers in the manubrium and the body of the sternum. Multiplanar images were used to accurately measure the thickness and the sagittal dimension of the manubrium, the sagittal dimension of the body, and the total sagittal dimension of the sternum in the sagittal plane. RESULTS: No significant differences in the manubrium measurements were observed between the genders. The thickness and sagittal dimension of the manubrium, sagittal dimension of the body, and total sagittal dimension of the sternum in the sagittal plane were significantly different between the age groups. We evaluated the ossification centers; shape and developmental variations in the manubrium and body; direction, calcification, and termination of the xiphoid process; developmental variations in the xiphoid process; and manubriosternal and sternoxiphoidal fusion. Significant variations were observed from person to person. CONCLUSION: The anatomy and the developmental properties of the sternum should be well understood in cases of potential chest and sternum injuries and in several surgical procedures. Therefore, knowledge of the development and the maturation of the sternum, and sternal variations and anomalies is important. We suggest that the postnatal development and the morphogenesis of the sternum can be adequately assessed using MDCT.

Sternal development in the pediatric population: evaluation using computed tomography.

BACKGROUND: The normal development of the sternum using CT imaging is not known. OBJECTIVE: To describe the normal development of the sternum in children on chest CT imaging. MATERIALS AND METHODS: CT imaging of 300 patients (150 male, 150 female), mean age: 4.97 years (range: 0.01-9.9 years), were evaluated retrospectively. The presence and number of ossification centers in the manubrium, each individual mesosternal segment and the xiphoid were reviewed. Additionally, the vertical and horizontal fusion between ossification centers was evaluated. Differences among age and gender were calculated. Descriptive statistics, analysis of variances (ANOVA), chi-square and Fisher exact tests were performed for statistical analysis. RESULTS: Manubrium: A single ossification center was seen in 88% of cases and two or three ossification centers were seen in 12%. More manubrial ossification centers were correlated to a younger age (P < 0.001, R = -0.2). Mesosternum: Majority of patients had a single ossification center in the first segment (85%). The majority of patients had double ossification centers in the second and third segments (51% and 64%, respectively). No ossification center was seen in the fourth segment in 38% of patients. No significant difference among the age of vertical ossification between mesosternal segments was found. (ANOVA; P > 0.05). Xiphoid: Absence was seen in 67% of the patients. Bifid xiphoid was seen in 1% of the patients. CONCLUSION: The normal development of the different components of the sternum is a process with wide variation among children. The large variability of mesosternal ossification center types should not be confused with pathology.

[The staging method of sternal end of clavicle epiphyseal growth by thin layer CT scan and imaging reconstruction].

OBJECTIVE: To establish a CT staging method of sternal end of clavicle epiphyseal growth for teenagers by thin layer CT scan, multiplanar reconstruction (MPR) and volume reconstruction (VR) technologies. METHODS: The CT imaging characteristics, which collected from 460 teenagers (aged from 15 to 25) in East and South China, were studied through both sternal ends of clavicles' imagings by thin layer coronal CT scan and axial CT scan, MPR and VR technologies. The parameters of sternal end of clavicle including the longest diameter of epiphysis, the longest diameter of metaphysis, their length ratio, area of epiphysis, area of metaphysis, and their area ratio were measured and calculated in order to establish new classification. RESULTS: Based on the staging method of Schmeling, integrating the CT imaging reconstruction information of sternal end of clavicle, the new classification of sternal end of clavicle epiphyseal growth were divided into 1 to 5 stages, and stage 2 and stage 3, respectively, contained a, b and c sub-classification. CONCLUSION: This new classification has merits of large sample size, wide age range and easy operability. By using CT imaging reconstruction techniques and analyzing the data which closely related to sternal end of clavicle epiphyseal growth of teenagers, the feasibility of the staging method could be increased.

[Progress in thin layer CT scan technology in estimating skeletal age of sternal end of clavicle].

It is practical value for determination the teenagers whether the age is full of the legal responsibility age of 18 years old or not by estimating skeletal age of sternal end of clavicle. The traditional methods mainly based on X-ray radiography. However, sternal end of clavicle and adjacent lung, bronchus, sternum, rib, transverse process of thoracic vertebra are overlapped each other. As a result of overlapping, there will be obtained false negative or positive film reading results when according to X-ray observation of epiphyseal growth of sternal end of clavicle, which directly affect the scientificalness and accuracy of estimating of skeletal age. In recent years, the scholars at home and abroad have started to use thin layer CT scan technology to estimate skeletal age of the sternal end of clavicle. With the 2D and 3D CT recombination technology, the accuracy of the film reading distinctly improves by making the shape, size and position of epiphysis displayed clearly. This article reviews the application and research progress of thin layer CT scanning technology in estimating skeletal age of sternal end of clavicle at home and abroad, analyzes the superiority and value of thin layer CT scan technology, which applied to skeletal age of sternal end of clavicle.

Quantitative geometric analysis of rib, costal cartilage and sternum from childhood to teenagehood.

Better understanding of the effects of growth on children's bones and cartilage is necessary for clinical and biomechanical purposes. The aim of this study is to define the 3D geometry of children's rib cages: including sternum, ribs and costal cartilage. Three-dimensional reconstructions of 960 ribs, 518 costal cartilages and 113 sternebrae were performed on thoracic CT scans of 48 children, aged 4 months to 15 years. The geometry of the sternum was detailed and nine parameters were used to describe the ribs and rib cages. A "costal index" was defined as the ratio between cartilage length and whole rib length to evaluate the cartilage ratio for each rib level. For all children, the costal index decreased from rib level 1 to 3 and increased from level 3 to 7. For all levels, the cartilage accounted for 45-60 % of the rib length, and was longer for the first years of life. The mean costal index decreased by 21 % for subjects over 3-year old compared to those under three (p < 10(-4)). The volume of the sternebrae was found to be highly age dependent. Such data could be useful to define the standard geometry of the pediatric thorax and help to detect clinical abnormalities.

The staging method of sternal end of clavicle epiphyseal growth by thin layer CT scan and imaging reconstruction / 法医学杂志

OBJECTIVE@#To establish a CT staging method of sternal end of clavicle epiphyseal growth for teenagers by thin layer CT scan, multiplanar reconstruction (MPR) and volume reconstruction (VR) technologies.@*METHODS@#The CT imaging characteristics, which collected from 460 teenagers (aged from 15 to 25) in East and South China, were studied through both sternal ends of clavicles' imagings by thin layer coronal CT scan and axial CT scan, MPR and VR technologies. The parameters of sternal end of clavicle including the longest diameter of epiphysis, the longest diameter of metaphysis, their length ratio, area of epiphysis, area of metaphysis, and their area ratio were measured and calculated in order to establish new classification.@*RESULTS@#Based on the staging method of Schmeling, integrating the CT imaging reconstruction information of sternal end of clavicle, the new classification of sternal end of clavicle epiphyseal growth were divided into 1 to 5 stages, and stage 2 and stage 3, respectively, contained a, b and c sub-classification.@*CONCLUSION@#This new classification has merits of large sample size, wide age range and easy operability. By using CT imaging reconstruction techniques and analyzing the data which closely related to sternal end of clavicle epiphyseal growth of teenagers, the feasibility of the staging method could be increased.

Progress in thin layer CT scan technology in estimating skeletal age of sternal end of clavicle / 法医学杂志

It is practical value for determination the teenagers whether the age is full of the legal responsibility age of 18 years old or not by estimating skeletal age of sternal end of clavicle. The traditional methods mainly based on X-ray radiography. However, sternal end of clavicle and adjacent lung, bronchus, sternum, rib, transverse process of thoracic vertebra are overlapped each other. As a result of overlapping, there will be obtained false negative or positive film reading results when according to X-ray observation of epiphyseal growth of sternal end of clavicle, which directly affect the scientificalness and accuracy of estimating of skeletal age. In recent years, the scholars at home and abroad have started to use thin layer CT scan technology to estimate skeletal age of the sternal end of clavicle. With the 2D and 3D CT recombination technology, the accuracy of the film reading distinctly improves by making the shape, size and position of epiphysis displayed clearly. This article reviews the application and research progress of thin layer CT scanning technology in estimating skeletal age of sternal end of clavicle at home and abroad, analyzes the superiority and value of thin layer CT scan technology, which applied to skeletal age of sternal end of clavicle.

Development of the mammalian axial skeleton requires signaling through the Gα(i) subfamily of heterotrimeric G proteins.

129/SvEv mice with a loss-of-function mutation in the heterotrimeric G protein α-subunit gene Gnai3 have fusions of ribs and lumbar vertebrae, indicating a requirement for Gα(i) (the "inhibitory" class of α-subunits) in somite derivatives. Mice with mutations of Gnai1 or Gnai2 have neither defect, but loss of both Gnai3 and one of the other two genes increases the number and severity of rib fusions without affecting the lumbar fusions. No myotome defects are observed in Gnai3/Gnai1 double-mutant embryos, and crosses with a conditional allele of Gnai2 indicate that Gα(i) is specifically required in cartilage precursors. Penetrance and expressivity of the rib fusion phenotype is altered in mice with a mixed C57BL/6 × 129/SvEv genetic background. These phenotypes reveal a previously unknown role for G protein-coupled signaling pathways in development of the axial skeleton.

Electrospun hydroxyapatite-functionalized PLLA scaffold: potential applications in sternal bone healing.

Sternal synthesis after median sternotomy, a conventional access practice in thoracic and cardiac surgery, is at the basis of severe complications, often impairing the clinical outcome of surgical interventions. In this work, we propose the use of an acellular biomaterial scaffold, to be interposed across the fracture rime during closure operations, directly exposing the biomaterial to bone marrow, in order to expedite healing process. A rabbit model of median sternotomy was performed and an electrospun scaffold composed of a hydroxyapatite-loaded absorbable biopolymer (poly-L: -lactide), shaped into a fibrillar structure, was used. CT follow-up confirmed a complete healing in the scaffold-treated group 1 week before the control. Histological evaluation demonstrated presence of newly formed bone trabeculae among scaffold fibers showing a higher degree of maturity with respect to the control untreated group. The proposed approach is able to both guide a more rapid healing and modulate inflammatory response across the wound site, resulting in improved healing and tissue remodeling with respect to conventional closure technique.

Fatigue properties of superelastic Ti-Ni filaments and braided cables for bone fixation.

This work is focused on the fatigue properties of the braided hollow tubular cables for bone fixation made of superelastic Ti-Ni filaments. To evaluate the fatigue life of the cable and the impact of braiding on fatigue life, a comparative study was conducted on both the braided cable and the single filament. The results of strain-controlled fatigue testing under variable mean and alternating strain conditions demonstrated that: (a) even though alternating strain is the most influent parameter, mean strain also has a significant impact on the fatigue life of both the filament and the braid; an improvement in the braided cable's fatigue life is observed under mean strains corresponding to the middle of the superelastic loop plateau; and (b) run-out (10(5) cycles) is reached at 1% of alternating strain for the filament, and at 0.3% for the braided cable. It was proved that the negative impact of braiding on fatigue life is caused: (a) by friction-induced damage of the braided filaments during cable manufacturing and (b) by locally occurring bending in the vicinity of the filaments' crossing, combined with the interfilament fretting during repetitive stretching of the braided cable.

Dorsal arthrodesis of thoracic spine and effects on thorax growth in prepubertal New Zealand white rabbits.

STUDY DESIGN: Dorsal arthrodesis of thoracic spine in a prepubertal New Zealand White rabbit model. OBJECTIVE: Evaluating the consequences of dorsal arthrodesis on the growth of the spine, sternum, and thorax in prepubertal rabbits, through the study of CT scans. SUMMARY OF BACKGROUND DATA: Vertebral arthrodesis in the treatment of progressive idiopathic scoliosis in prepubertal patients is not ideal, but is still a choice in treating major deformities of the spine. Postoperative assessment of spinal deformity is essential, feasible, and recordable through CT scans. METHODS: Twelve female rabbits, 9 weeks old, were subjected to surgery for dorsal arthrodesis of the upper thoracic spine. Surgery involved the implant of 2 "C"-shaped titanium bars, which were placed beside the spinous processes of the thoracic vertebrae. Three CT scans were performed, 10 (T1), 55 (T2), and 139 (T3) days after surgery. Measures were obtained by Myrian Pro software for 3 different groups: G1 with complete fusion, G2 with incomplete fusion, and G3 sham-operated. RESULTS: The average of the dorsoventral/laterolateral thoracic diameter ratio at fused levels is lower than 1 in G1 as well as in G2; on the contrary, in G3 is higher than 1. The average growth of the sternum length between T1 and T2 and between T2 and T3 is minor in G1 than in G2 and G3. The dorsal and ventral lengths of thoracic vertebral bodies in the spinal segment D1-D6 is smaller in G1 and G2 than in G3, whereas no differences were observed between the 3 groups in the D7-D12 segment without arthrodesis. CONCLUSION: Dorsal arthrodesis in prepubertal rabbits changes thoracic growth patterns. In operated rabbits, the dorsoventral thoracic diameter grows more slowly than the laterolateral thoracic diameter. The sternum as well as the lengths of thoracic vertebral bodies in the spinal segment D1-D6 grow less. The crankshaft phenomenon is evident at the fused vertebral levels where there is a reduction of thoracic kyphosis.

Parathyroid hormone/parathyroid hormone-related peptide modulates growth of avian sternal cartilage via chondrocytic proliferation.

Parathyroid hormone (PTH; 10(-7) to 10(-15) M) decreased terminal chondrogenesis in the avian sterna. During the first half of an 8-day culture, 100 nM PTH (1-34) significantly increased sternal length and downregulated the deposition of type X collagen and its mRNA expression. However, it remains unclear how PTH increased cartilaginous growth. In this study, we examined growth by both cell proliferation and analysis of cyclin d1 and collagen mRNA. Types II, IX, and X collagens and cyclin d1 mRNA were quantified through real-time RT-PCR, while Ki-67 was used as an immunohistochemical proliferation marker. Extracellular matrix content was measured through mRNA quantification of types II, IX, and X collagen and observing deposition of the same collagens. PTH significantly increased the proliferation marker Ki-67 in the sternal cephalic region. There was less type II and X collagen in PTH-treated sterna with concomitant decreases in mRNA production, suggesting that proliferation was the major contributor to cartilage growth in the presence of PTH/PTH-related peptide receptor activation. In conclusion, these experiments demonstrated that PTH increased cartilage growth by upregulating cell proliferation or other extracellular matrix components.