Subdental synchondrosis and anatomy of the axis in aging: a histomorphometric study on 30 autopsy cases

During skeletal development the two ossification centers of the odontoid process are separated from the corpus of the axis by a subdental synchondrosis. This synchondrosis is thought to close and disappear spontaneously in adolescence although this has never been studied in detail. The basis of the dens is of clinical relevance as type II dens fractures are located here. To characterize the morphological architecture of the axis with particular attention to the subdental synchondrosis, the complete axis was harvested from thirty age-matched and gender-matched patients of the three different age groups at autopsy. The subdental synchondrosis and the bone structure of the dens, the basis of the dens and the body of C2 were analyzed by radiography, histology and quantitative histomorphometry. At the macroscopic level the persistency of the subdental synchondrosis in the adult cervical spine was detected in 87% (26 of 30) of the specimens. Histomorphometry revealed a residual disc blastema with an average size of 25.8% of the sagittal depth of the basis of the dens at this level. Bony integration of the synchondrosis was poor throughout all ages. Histologically a cartilaginous matrix composition of the subdental synchondrosis persisted throughout all groups. The trabecular microarchitecture demonstrated a significant reduction of bone volume and trabecular number as well as an increased trabecular separation within the basis of the dens as compared to the corpus or the dens of C2. This histomorphometric data regarding a poor integration of the synchondrosis into the trabecular network and the reduced bone mass within the basis of the dens might offer a previously underestimated explanation for the occurrence of type II dens fractures and their association with pseudoarthrosis, respectively.Matthias Gebauer and Christian Lohse contributed equally to this study and therefore share first authorship.     

张应力对小鼠蝶枕软骨联合细胞增殖及低氧诱导因子-1α表达的影响

目的:了解循环张应力对小鼠颅底蝶枕软骨联合细胞(SOSCs)增殖及低氧诱导因子-1α表达的影响.方法:采集1 d龄小鼠的SOSCs进行体外培养,对第三代细胞加载牵张形变率分别为3％、6％、9％,频率为1 Hz,持续时间为1 h的循环张应力;用流式细胞术测算细胞增殖指数,用蛋白免疫印迹技术分析Hif-1α的表达水平.用按...     

Correlation between spheno-occipital synchondrosis,dental age,chronological age and cervical vertebrae maturation in Turkish population: is there a link?

Objective: To assess the correlation between third molar mineralization (TMM), spheno-occipital synchondrosis (SOS) fusion, chronologic age and cervical vertebrae maturation (CVM) for skeletal maturation.

Materials and methods: Radiographs for 116 patients between 8 and 28 years were evaluated for age determination using mandibular TMM, SOS fusion and CVM. Spearman Correlation and Kappa test analyses were used to assess the relationship between variables and for intraobserver reliability.

Results: Strong correlation was found between chronological age and TMM for males (r?=?.802) and females (r?=?.842), very strong correlation was found between age and CVM for males (r?=?.812) and moderate for females (r?=?.449), it was strong between age and SOS fusion for males (r?=?.810) and females (r?=?.643). Correlation between TMM and SOS was found to be strong for males (r?=?.759) and moderate for females (r?=?.534), it was strong between TMM and CVM for males (r?=?.723) and weak for females (r?=?.371). Very strong correlation was found between CVM and SOS fusion for males (r?=?.851) and strong correlation for females (r?=?.618).

Conclusion: Good correlation was found between the degrees of TMM, fusion of SOS and CVM in young Turkish population.     

不同加载时间周期性张应力对大鼠颅底软骨细胞的影响

目的: 构建颅底软骨细胞体外培养力学刺激模型,研究周期性张应力对颅底软骨细胞主要细胞外基质（Ⅱ型胶原）和Sox9表达的影响。方法: 采用FX-5000T应力加载系统对体外培养的第2代大鼠颅底软骨细胞分别施加3、6、12、24 h的周期性张应力,加力值均为10%形变率,频率均为1 Hz。加力后即刻收集细胞,提取总RNA,实时荧光定量 PCR技术检测颅底软骨细胞Ⅱ型胶原（type-Ⅱcollagen,Col-Ⅱ）和Sox9 mRNA的表达。采用SPSS 17.0软件包对数据进行统计学分析。结果: 与对照组（加力0 h）相比,加力3 h组Col-Ⅱ和Sox9表达下降,且后者有显著差异（P<0.05）;加力6 h组Col-Ⅱ和Sox9表达显著下降（Col-Ⅱ,P<0.01;Sox9,P<0.05）;加力12 h组Col-Ⅱ和Sox9表达较6 h组有所上升,与对照组相比差异无统计学意义;加力24 h组中,两者表达与对照组相比显著升高（P<0.05）。结论: 周期性张应力可影响颅底软骨细胞增殖及细胞外基质合成,加力短时间基质合成抑制,增加加力时间则明显促进基质合成,且成软骨分化标志物Sox9 mRNA表达水平差异先于Col-Ⅱ出现。     

Differential responses to parathyroid hormone‐related protein (PTHrP) deficiency in the various craniofacial cartilages

PTHrP null mutant mice exhibit skeletal abnormalities both in the craniofacial region and limbs. In the growth plate cartilage of the null mutant, a diminished number of proliferating chondrocytes and accelerated chondrocytic differentiation are observed. In order to examine the effect of PTHrP deficiency on the craniofacial morphology and highlight the differential feature of the composing cartilages, we examined the various cartilages in the craniofacial region of neonatal PTHrP deficient mice. The major part of the cartilaginous anterior cranial base appeared to be normal in the homozygous PTHrP deficient mice. However, acceleration of chondrocytic differentiation and endochondral bone formation was observed in the posterior part of the anterior cranial base and in the cranial base synchondroses. Ectopic bone formation was observed in the soft tissue‐running mid‐portion of the Meckel's cartilage, where the cartilage degenerates and converts to ligament in the course of normal development. The zonal structure of the mandibular condylar cartilage was scarcely affected, but the whole condyle was reduced in size. These results suggest the effect of PTHrP deficiency varies widely between the craniofacial cartilages, according to the differential features of each cartilage. Anat Rec 255:452–457, 1999. © 1999 Wiley‐Liss, Inc.     

The growth of the posterior cranial fossa in FGFR2-induced faciocraniosynostosis: A review

BackgroundThe growth of the posterior fossa in syndromic craniostenosis was studied in many papers. However, few studies described the pathophysiological growth mechanisms in non-operated infants with fibroblast growth factor receptor (FGFR) type 2 mutation (Crouzon, Apert or Pfeiffer syndrome), although these are essential to understanding cranial vault expansion and hydrocephalus treatment in these syndromes.ObjectiveA review of the medical literature was performed, to understand the physiological and pathological growth mechanisms of the posterior fossa in normal infants and infants with craniostenosis related to FGFR2 mutation.DiscussionOf the various techniques for measuring posterior fossa volume, direct slice-by-slice contouring is the most precise and sensitive. Posterior fossa growth follows a bi-phasic pattern due to opening of the petro-occipital, occipitomastoidal and spheno-occipital sutures. Some studies reported smaller posterior fossae in syndromic craniostenosis, whereas direct contouring studies reported no difference between normal and craniostenotic patients. In Crouzon syndrome, synchondrosis fusion occurs earlier than in normal subjects, and follows a precise pattern. This premature fusion in Crouzon syndrome leads to a stenotic foramen magnum and facial retrusion.     

The dens-arch synchondrosis versus the Hangman's fracture

The synchondrosis between the dens and arch of C2 is a normal structure in infants and children. It is not visible on lateral views of the cervical spine, but is routinely visible on oblique views. In such cases it has a distinct tendency to mimic a C2-arch fracture. The varying appearance of this synchondrosis and its differentiation from a true fracture of C2 are the subjects of this report.     

Three-dimensional assessment of the spheno-occipital synchondrosis and clivus after tooth-borne and bone-borne rapid maxillary expansion:: A retrospective CBCT study using voxel-based superimposition

ObjectivesTo assess changes in spheno-occipital synchondrosis after rapid maxillary expansion (RME) performed with conventional tooth-borne (TB) and bone-borne (BB) appliances.Materials and MethodsThis study included 40 subjects with transverse maxillary deficiency who received TB RME or BB RME. Cone-beam computed tomography images (CBCT) were taken before treatment (T0), and after a 6-month retention period (T1). Three-dimensional surface models of the spheno-occipital synchondrosis and basilar part of the occipital bone were generated. The CBCTs taken at T0 and T1 were registered at the anterior cranial fossa via voxel-based superimposition. Quantitative evaluation of Basion displacement was performed with linear measurements and Euclidean distances. The volume of the synchndrosis was also calculated for each time point as well as the Nasion-Sella-Basion angle (N-S-Ba°). All data were statistically analyzed to perform inter-timing and intergroup comparisons.ResultsIn both groups, there was a small increment of the volume of the synchondrosis and of N-S-Ba° (P < .05). Basion showed a posterosuperior pattern of displacement. However, no significant differences (P > .05) were found between the two groups.ConclusionsAlthough TB and BB RME seemed to have some effects on the spheno-occipital synchondrosis, differences were very small and clinically negligible.     

Time and pattern of the fusion of the spheno-occipital synchondrosis in patients with skeletal Class I and Class III malocclusion

Objectives:To investigate the time and pattern of fusion of the spheno-occipital synchondrosis in patients with skeletal Class I and Class III malocclusion using cone-beam computed tomography (CBCT).Materials and Methods:A total of 262 CBCT images were collected: 140 skeletal Class I (0° < ANB < 4°; 71 males, 69 females) and 122 skeletal Class III (ANB ≤ 0°; 61 males and 61 females). The fusion stages were identified using CBCT images of a six-stage system defined by the appearance of osseous cores and ossifying vestige in the synchondrosis. The age distributions of each stage and the pattern of fusion were evaluated.Results:The stages of fusion progressed with increasing age (P < .05, r = .824), and the age distributions in the female groups were generally 1 to 3 years younger than those in the male groups. However, no significant differences were observed between the skeletal Class I and Class III groups regarding the time of ossification of the synchondrosis. The osseous cores appeared most frequently in the supero-center part, followed by the mid-center part of the synchondrosis.Conclusions:The time and pattern of fusion of the spheno-occipital synchondrosis are not apparently different between patients with Class I malocclusion and those with Class III malocclusion. The osseous cores appear frequently in the supero-center and mid-center of the synchondrosis with various patterns before the end of the pubertal growth spurt period.