Cranial sutures

Cranial sutures are not of great concern to the modern neurosurgeon, except when abnormalities interfere with the skull's shape and its ability to expand during childhood. It is a commonplace that a craniotomy may cross a variety of sutures without providing any extra difficulty to the operator. The sagittal suture does remain useful as a definition of the midline of the cranium and as an indicator of the underlying sinus. Galen for reasons that are far from clear, "observed" relationships between the sutures, the meninges and the pericranium which led him to advise avoidance of any surgical proximity to the sutures. The result of this proscription was a severe limit of the access surgeons considered was appropriate and thus limited their ability to care for their patients.

Fractality of Cranial Sutures

It has long been known that skull suture has a typical fractal structure. Although the fractal dimension has been utilized to assess morphology, the mechanism of the fractal structure formation remains to be elucidated. Recent advances in the mathematical modeling of biological pattern formation provided useful frameworks for understanding this mechanism. This chapter describes how various proposed mechanisms tried to explain the formation of fractal structures in cranial sutures.

Wormian Bones: Prevalence, Topography, and Implications

BACKGROUND

Wormian bones also known as sutural bones are asymmetrical and shapeless bones occurring in cranial sutures and fontanelle of the skull. Their incidence is reported to vary in population. The exact etiology is debatable, but their formation is under the control of both genetic and environmental factors and has great anthropological and clinical implications related to the cranium. Due to high clinical relevance of Wormian bones, the study was carried out. The aim of the study is to expound the incidence and topography of Wormian bones along with clinical significance in dry adult skulls of Indian origin.

METHODS

The study was conducted in the Department of Anatomy using 200 complete adult dry skulls of unknown age and sex. All the sutures in the skull were inspected for the presence of Wormian bones. The Wormian bones were classified into 10 categories, and associated implications were brought out. The Wormian bones were photographed, and details were compared with the available literature.

RESULTS

The Wormian bones were observed in 190 (380 sides) skulls with 186 on the right side and 108 on the left side. The predominance site of sutural bone was lambdoid suture followed by sagittal suture. The least common site of Wormian bone was lambda.

CONCLUSION

The detailed information of precise topography, frequency, and number of Wormian bones is of utmost use for surgeons performing surgery on the skull, anthropologists for identifying races, and forensic scientists for investigating child abuse cases.

Comparative digital reconstruction of Pica pica and Struthio camelus and their cranial suture ontogenies

To date, several studies describe post-hatching ontogenetic variation in birds; however, none of these studies document and compare ontogenetic variation of the entire skull in multiple avian species. Therefore, we studied ontogenetic skull variation of two bird species with very different ecologies, Pica pica, and Struthio camelus, using μCT based 3D reconstructions. For each specimen, we performed bone-by-bone segmentation in order to visualize and describe the morphological variation of each bone during ontogeny and estimated the average sutural closure of the skulls to identify different ontogenetic stages. Although bone fusion of P. pica occurs more rapidly than that of S. camelus the general sequence of bone fusion follows a similar trend from posterior to anterior, but a more detailed analysis reveals some interspecific variation in the fusion patterns. Although growth persists over a longer period in S. camelus than in P. pica and adults of the former species are significantly larger, the skull of the most mature S. camelus is still less fused than that of P. pica. Different growth and fusion patterns of the two species indicate that the interspecific ontogenetic variation could be related to heterochronic developments. Nevertheless, this hypothesis needs to be tested in a broader phylogenetic framework in order to detect the evolutionary direction of the potential heterochronic transformations.

Is Asterion a Reliable Surgical Landmark for the Transverse and Sigmoid Sinus Junction in Indian Skulls?

Background

Asterion is the junction of lambdoid, parietomastoid, and occipitomastoid sutures. In traditional anatomy teaching, it is believed that asterion sits over the transverse-sigmoid sinus junction (TSSJ). It is a significant surgical landmark for the placement of a burr hole in the retrosigmoid approach.

Objective

The purpose of this study was to evaluate the asterion's accuracy as a TSSJ-specific external surgical landmark in the Indian population.

Materials and Methods

16 human dried skulls were obtained from the Department of Anatomy, AIIMS, New Delhi. The point of TSSJ was taken between the two lips and just posterior to the entry of the superior petrosal sinus. Asterion internally was localized with the help of a geometrical divider. The x- horizontal/ anterior and y- vertically superior (+)/ inferior (-) distances were measured from asterion (internally) to the TSSJ by a digital vernier caliper.

Results

The mean horizontal distance (x) of the left side asterion & TSSJ was 10.3±1.0mm whereas the vertical distance (y) ranged between +2 to -4.3 mm. The mean horizontal distance (x) of the right side asterion & TSSJ was 13.5±1.4mm whereas the vertical distance (y) ranged between +3 to -4.2 mm.

Conclusion

Asterion is not a reliable landmark for TSSJ in Indian skulls. The TSSJ with respect to asterion was found on average 10mm and 13.5mm anterior on the left and right side respectively, and mostly inferior (average 4.2mm) in 75% of the skulls. The TSSJ was closer to the asterion on the left side in comparison with the right side. However, further studies with a larger sample size will be needed to evaluate the population-specific relation of asterion with the TSSJ.

Morphometric and morphological evaluation of temporozygomatic suture anatomy in dry adult human skulls

This study aims to evaluate the position, morphometric, and morphological features of the temporozygomatic suture (TZS) located on the zygomatic arch (ZA) in dry adult human skulls. Thirty-two crania were evaluated. Measurements for the TZS were carried out using the ImageJ software. Morphometric measurements were carried out bilaterally in 23 crania and unilaterally in 9 crania (right: 4, left: 5). A total of 55 TZSs were analyzed. Localization of the TZS was determined according to the reference landmarks on the ZA. Morphologic features of the TZS evaluated in terms of "joint shape type" and "suture margin pattern". Descriptive statistics of the morphometric and morphologic variables were calculated. A statistically significant difference between the right and left sides was observed for the localization of the TZS (p < 0.05). TZS is located more anteriorly on the left side than the right side. Based on the "joint shape type", four types of TZS were observed: Type 1 (angular) (34.55%), Type 2 (curvy) (34.55%), Type 3 (oblique) (14.55%), Type 4 (horizontal) (16.36%). Based on the "suture margin pattern", five types of TZS were observed: Type A (linear) (12.73%), Type B (denticulate) (34.55%), Type C (serrated) (23.64%), Type D (mixt) (21.82%), Type E (fused) (7.27%). No significant association between the type and lateralization was found for both morphologic classifications. To the best of our knowledge, this is the first published report regarding the localization and morphologic classification of the TZS in adult human crania. Considering the TZS with its morphometric and morphological features may contribute to clinical or forensic medical evaluations.

Squamous suture obliteration: frequency and investigation of the associated skull morphology

This study aimed to investigate the frequency of squamous suture (SqS) obliteration, to estimate the involvement of the major calvarial sutures and those surrounding the temporal squama, and to inspect the neuro- and basicranium for deformities. A series of 211 dry skulls of contemporary adult males were macroscopically observed. The skulls with closed SqS were scanned using an industrial µCT system. Digital morphometry of the skulls with obliterated SqS was performed by recording the 3D coordinates of anatomic landmarks and calculation of linear distances, angles and indices. Obliteration of SqS was observed in 3 (1.42%) skulls. One skull showed bilateral SqS obliteration. The other two cases were unilateral, one right-sided and one left-sided. SqS obliteration seems to be co-ordinated with the closure of the parietomastoid suture, partially related to the closure of the occipitomastoid, sphenoparietal and sphenofrontal sutures, and independent from the closure of the sphenosquamosal suture and the major calvarial sutures. No severe disproportions in the skull configuration were observed in the three investigated cases. The major differences in the complimentary hemicrania concern the parietal and occipital parts of the skull vault. Dorsum sellae erosion, an indicator for raised intracranial pressure, was observed in all three cases.

Anatomic Analysis of the Internal and External Aspects of the Pterion

OBJECTIVE

The pterion is an H-shaped suture complex. This study's goal was to determine the location of its external and internal surfaces and extension and emphasize and discuss its surgical importance.

METHODS

Fifty dried adult human skulls were obtained from the Department of Anatomy. A 2-mm drill bit was placed externally over the pterion, and the pterion was drilled through the bone perpendicular to the skull's surface.

RESULTS

The midpoint of the H shape in the pterion area was not at the same level on the skull's external and internal pterion surfaces. According to these measurements, the external pterion lay above the internal pterion when the skull was viewed externally. Furthermore, the internal pterion was on average longer than the external pterion. The internal and external pterions were schematized such that the skull was viewed from the outside. These areas were divided into 4 quadrants (anterior-superior, anterior-inferior, posterior-superior, and posterior-inferior) by a vertical and horizontal line. In 30 cases (60%), sulci of the middle meningeal artery's parietal branches entered the posterior-superior quadrant on the bone, whereas the artery's frontal branches were located in the anterior-superior and anterior-inferior quadrants, and the Sylvian fissure's origin was in the posterior-inferior quadrant.

CONCLUSIONS

By using a subdivision into 4 quadrants, and considering our anatomic findings, we determined the way surgical procedures can be performed more easily and reliably. Even with modern localization technologies, anatomic landmarks can be useful to the neurosurgeon.

Prevalence of agenesis of frontal sinus in human skulls with metopism

BACKGROUND

The frontal bone is an anatomical structure of the skull separated by the metopic suture in the childhood. The scientific literature indicates that metopic suture consolidates with closure in the early stages of life. Metopism is the term used to describe a metopic suture that persists up to the adulthood. Persistent metopic suture is associated potentially with the agenesis of the frontal sinus.

AIM

To investigate the prevalence of absent frontal sinuses in dry skulls with metopism.

MATERIALS AND METHODS

The present study was performed after the approval of the local Committee of Ethics in Research. The sample consisted of dry skulls (n=245), aging between 17 and 50 years old, of the Forensic Medical Institute of Goiânia, Brazil. The skulls underwent anthropological exam in the search for metopism. Radiographic exam was performed in the skulls with metopism to verify the presence or absence of the frontal sinus. The radiographic assessment was performed with a Mobile DaRt Evolution device (Shimadzu, Kyoto, Japan) with protocol set in 64 kV and 16 mA).

RESULTS

From the 245 dry skulls, 17 presented metopism. The length of the metopic suture in the skulls, considering the distances between nasio and bregma craniometric landmarks, ranged between 114 mm and 137 mm. Radiographic exams were performed on 16 skulls (one skull was not analysed radiographically because of extensive destruction). Only one skull (6.25%) had the frontal sinus absent. Besides the agenesis, the present study also found four (12.5%) skulls with aplasia and eight (25.0%) hyperplasia of the frontal sinus in dry skulls with metopism.

CONCLUSION

The present study found a low prevalence rate of the agenesis of frontal sinuses in dry skulls with metopism.

[Stature estimation from sagittal and coronal suture lengths for Central European individuals]

$Human skulls frequently represent the only skeletal remains of an unidentified corpse available for forensic osteological examination. Skulls are very useful in reliably determining sex and also yield fairly good clues to an individual's age and ancestry. To date, however, a sufficiently accurate correlation between skull measurements and stature could not be found. In contrast, the results of a study by Rao et al. (2009) seemed to be promising, by finding a good correlation between the length of the coronal and sagittal sutures and stature in a male Indian population. In an attempt to verify the transferability of their results to a Central European population, the authors measured the length of the sagittal and coronal sutures with a tape measure along with body height in the course of 117 autopsies performed at the Institute of Forensic Medicine at the University of Giessen during 2009 and 2010. The age of the individuals measured ranged from 15 to 96 years (mean value 52.8, median 51 years). Of these individuals, 82 were male and 35 were female. The length of the sagittal suture with respect to body length yielded a correlation coefficient of only r = 0.045 (p = 0.617) in the regression analysis. Similar results were found for the coronal suture: In this case the correlation coefficient was r = 0.015. With an assumed maximum permissible probability of error of α = 0.05, none of the performed regression analyses were found to be statistically significant. As expected, our results suggest that neither the length of the sagittal nor the length of the coronal suture is suitable for a forensic estimation of stature for Central European individuals.

Fusion Patterns in the Skulls of Modern Archosaurs Reveal That Sutures Are Ambiguous Maturity Indicators for the Dinosauria

The sutures of the skulls of vertebrates are generally open early in life and slowly close as maturity is attained. The assumption that all vertebrates follow this pattern of progressive sutural closure has been used to assess maturity in the fossil remains of non-avian dinosaurs. Here, we test this assumption in two members of the Extant Phylogenetic Bracket of the Dinosauria, the emu, Dromaius novaehollandiae and the American alligator, Alligator mississippiensis, by investigating the sequence and timing of sutural fusion in their skulls. As expected, almost all the sutures in the emu skull progressively close (i.e., they get narrower) and then obliterate during ontogeny. However, in the American alligator, only two sutures out of 36 obliterate completely and they do so during embryonic development. Surprisingly, as maturity progresses, many sutures of alligators become wider in large individuals compared to younger, smaller individuals. Histological and histomorphometric analyses on two sutures and one synchondrosis in an ontogenetic series of American alligator confirmed our morphological observations. This pattern of sutural widening might reflect feeding biomechanics and dietary changes through ontogeny. Our findings show that progressive sutural closure is not always observed in extant archosaurs, and therefore suggest that cranial sutural fusion is an ambiguous proxy for assessing maturity in non-avian dinosaurs.

Three-dimensional model of the skull and the cranial bones reconstructed from CT scans designed for rapid prototyping process

This paper presents the effects of building mesh models of the human skull and the cranial bones from a series of CT-scans. With the aid of computer so ware, 3D reconstructions of the whole skull and segmented cranial bones were performed and visualized by surface rendering techniques. The article briefly discusses clinical and educational applications of 3D cranial models created using stereolitographic reproduction.

Effects of low-intensity pulsed ultrasound on bone formation after the expansion of the inter-premaxillary suture in rats: a histologic and immunohistochemical study

BACKGROUND

Orthodontic maxillary expansion is a commonly-performed treatment approach to correct transverse maxillary deficiencies by separating the mid-palatal suture. To obtain a successful treatment result and prevent relapse, the expanded maxillary sutures require maintenance by means of qualified bone reorganisation.

AIM

To assess the effects of low-intensity pulsed ultrasound (LIPUS) on sutural bone formation after the expansion of the interpremaxillary suture in rats.

METHODS

Sixteen male Wistar rats, 6 to 8-week old, were used. The expansion appliance comprised a helical spring fabricated from 0.014 inch stainless steel wire (Dentaurum, Ispringen, Germany). The rats were divided into two equal groups and randomly assigned to the LIPUS treatment group or a sham-operation group. LIPUS was delivered via a 2.5 cm diameter ultrasound transducer (Exogen, Smith and Nephews, Inc., Memphis, TN, USA) for 20 minutes per day during 7 days of post-expansion retention. Following retention, the rats' maxillae were surgically removed and histologic and immunohistochemical specimens were prepared and examined.

RESULTS

The number of osteoblasts and blood vessel dimensions in the ultrasound group increased but was not significant, compared with the control group. A statistically significant difference in osteocalcin, VEGF and TGF-β immunoreactivities (p < 0.01) was found in the area of the mineralising tissue. Only VEGF immunoreactivity was significant between two groups (p < 0.01) in the fibrous tissue area.

CONCLUSIONS

The area of mineralising tissue in the LIPUS-applied group expressed activity markers for osteocalcin, VEGF and TGF-β compared with a surrounding area of fibrous tissue. Cellular activation in the LIPUS group was greater than that of controls. Therefore, LIPUS may be accepted as a useful approach to enhance sutural bone formation.

Symmetry of external auditive meatus. A pilot study on human skulls

OBJECTIVES. To evaluate the perpendicularity of the line connecting external auditive meatus to the midsagital plane and the palatal suture as a midsagittal symmetry reference line. Setting and Sample Population - 62 randomly chosen human skulls from osteological collection (Vilnius University). MATERIAL AND METHODS. The skulls were photographed (Nikon 40 D, Nikkor lens 50 mm) from basal, frontobasal and frontal views. Photos were analysed with Adobe Photoshop CS5 (Adobe). The first line connected frontal points of external auditive meatus and the angle to the midsagittal plane was measured. The second line (the palatal suture) was compared to the median sagittal plane. Data was analysed with SPSS 17 (IBM). RESULTS. The mean value for the angles of the line between the external auditive meatus and the midsagittal plane in basal views was 90.12° (SD=1.48°) and in frontobasal 90.36° (SD=2.25°). No statistically significant differences were found between groups of age and sex. The inter-rater agreement for evaluation of the adequacy of palatal suture with the midsagital plane was high (Cohen's Kappa 0.702 (p<0.05)) as well as the coincidence of both lines in basal and frontobasal views (90.3% and 85.5% respectively). CONCLUSION. Considering the limits of this study the angle between external auditive meatus and midsagital skull plane has a characteristic fluctuating asymmetry. The congruence of palatal suture and midsagital plane is debatable.

Stereotaxis of mandibular nerve initial point of trigeminal ganglion in rats

OBJECTIVE

To acquire parameters for stereotaxis of the mandibular nerve initial point of the trigemenial ganglion (TG) and to test the accuracy of the acquired parameters for microinjection into the mandibular nerve initial point of TG in adult rats.

METHODS

Sprague-Dawley rats (260-270 g) were mounted onto a stereotaxic frame. The bregma was set as an anchor point and the three-dimensional parameters between the mandibular nerve initial point of the bilateral TGs and the bregma were measured in 25 rats. The accuracy of these parameters was tested using microinjection of Evans blue dye into the mandibular nerve initial point of the bilateral TGs in 30 rats and the injection sites were evaluated by dissection.

RESULTS

The three-dimensional parameters of the mandibular nerve initial point of the bilateral TGs were 3.5 ± 0.1 mm posterior and 3.6 ± 0.2 mm lateral to the bregma, and 12.0 ± 0.2 mm inferior to the skull surface. Accuracy for the microinjection of Evans blue dye into the mandibular nerve initial point of the bilateral TGs was 86.7% (52/60).

CONCLUSION

The acquired parameters served well for stereotaxis and microinjection of reagents into the mandibular nerve initial point of TG.

Wormian bones: a review

Wormian bones are abnormal ossicles that develop from extra ossification centers within the cranium. They are most frequently located in the lambdoid suture or the coronal suture, and have been seen in the fontanelles, particularly the posterior fontanelle. It is unclear at this time exactly how or why they are formed, although genetic as well as environmental factors have been proposed. Their initial formation is thought to be caused by a degree of dural strain and increased sutural width. These conditions can result from mechanically induced stress due to intentional deformation like that practiced in ancient cultures, premature sutural closure, or from reduced skull ossification as seen in metabolic bone diseases. The cause of the malformation can have an influence on the number and location of Wormian bones. Clinically, Wormian bones are used as markers in the diagnoses of many autosomal dominant genetic disorders, namely, craniosynostosis and osteogenesis imperfecta.

[Morphometric characteristics of the asterion and the posterolateral surface of the skull: its relationship with dural venous sinuses and its neurosurgical importance]

BACKGROUND

The knowledge of the location and morphometric of the lateral venous sinus (transverse and sigmoid), and their relationship with the asterion and other surface anatomical landmarks, it is imperative for posterolateral approaches to the posterior cranial fossa to avoid vascular structures injury and surgical complications.

OBJECTIVE

Determine an anatomical area security for a drill that allows entry into the posterior cranial fossa without damaging adjacent structures, and study the morphometric characteristics asterion, the lateral sinus and bony landmarks of the posterolateral surface of the skull.

METHODS

With a 1.3 mm drill drilled both sides of 88 dry skulls (176 hemicranias). The anatomical landmarks studied were the asterion, the apex of the mastoid process, spina suprameatal, the Frankfurt horizontal plane, the posterior root of the zygomatic arch, the external occipital protuberance and its relationship with the sinus transversus.

RESULTS

The asterion type I prevails in 74.4% of the pieces. In 82.4% of the skulls asterion level is, sinus transversus in less than 12.5% and above this at 5.1%.

CONCLUSIONS

With the data obtained from this and other research, the initial trephine should be placed below the 15 mm and 15 mm asterion post this to reduce the risk of injury from sinus transversus.

Characterization of the bending strength of craniofacial sutures

The complex, thin and irregular bones of the human craniofacial skeleton (CFS) are connected together through bony articulations and connective tissues. These articulations are known as sutures and are commonly divided into two groups, facial and cranial sutures, based on their location in the CFS. CFS sutures can exhibit highly variable degrees of interdigitation and complexity and are believed to play a role in accommodating the mechanical demands of the skull. This study aimed to evaluate the mechanical behavior of CFS bone samples with and without sutures and to determine the effect of sutural interdigitations on mechanical strength. Sagittal, coronal, frontozygomatic and zygomaticotemporal sutures along with adjacent bone samples not containing sutures were excised from six fresh-frozen cadaveric heads. The interdigitation of the sutures was quantified through μCT based analysis. Three-point bending to failure was performed on a total of 29 samples. The bending strength of bone samples without sutures demonstrated a non-significant increase of 14% as compared to samples containing sutures (P=0.2). The bending strength of bones containing sutures was positively correlated to the sutural interdigitation index (R=0.701, P=0.002). The higher interdigitation indices found in human cranial vs. facial sutures may be present to resist bending loads as a functional requirement in protecting the brain.

Imaging of the Wormian bones using microcomputed tomography

Wormian bones are irregular ossicles of small size and reveal fractal pattern of their edges. Their anatomy was visualized in volumetric reconstructions obtained from a series of micro-CT scans. In visual evaluation Wormian bones showed typical anatomy for the calvarial bones. They revealed three-layer composition: the outer and the inner table of the compact bone intervening with the table of the spongy bone. Microcomputed tomography captured all details of the interdigitation of the edge being incorporated into the lambdoid suture and interlocked between opposing edges of the occipital and parietal bones. This modality provided accurate images which allowed delineating morphological differences between the compact bone and the diploe, including vascular channels.

Cranial sutures and diploae morphology

The aim of the study was to assess the normal cranial suture and bone diploae ultrastructural morphology. Two types of sutures from different specimens were collected. The micro-CT scanning provided a three-dimensional view of the sutures at a microscopic level thus allowing the evaluation of the development stage and a rapid analysis evaluation of bone and diploae morphology. In the meantime, the micro-CT is able to generate more slices than the normal histology preserving the analyzed specimens and became one of the most powerful tools in the craniofacial area. The micro-CT analysis generated structure-orientated slices that in conjunction with the histological sections provide a high quality quantitative analysis of all cranial sutures and of the cranial bones diploae.

The importance of craniofacial sutures in biomechanical finite element models of the domestic pig

Craniofacial sutures are a ubiquitous feature of the vertebrate skull. Previous experimental work has shown that bone strain magnitudes and orientations often vary when moving from one bone to another, across a craniofacial suture. This has led to the hypothesis that craniofacial sutures act to modify the strain environment of the skull, possibly as a mode of dissipating high stresses generated during feeding or impact. This study tests the hypothesis that the introduction of craniofacial sutures into finite element (FE) models of a modern domestic pig skull would improve model accuracy compared to a model without sutures. This allowed the mechanical effects of sutures to be assessed in isolation from other confounding variables. These models were also validated against strain gauge data collected from the same specimen ex vivo. The experimental strain data showed notable strain differences between adjacent bones, but this effect was generally not observed in either model. It was found that the inclusion of sutures in finite element models affected strain magnitudes, ratios, orientations and contour patterns, yet contrary to expectations, this did not improve the fit of the model to the experimental data, but resulted in a model that was less accurate. It is demonstrated that the presence or absence of sutures alone is not responsible for the inaccuracies in model strain, and is suggested that variations in local bone material properties, which were not accounted for by the FE models, could instead be responsible for the pattern of results.

Anatomical variation and morphology in the position of the palatine foramina in adult human skulls from Greece

OBJECTIVE

To investigate the anatomical variability of the palatine structures in Greek population.

MATERIAL AND METHODS

71 Greek adult dry human skulls were examined to detect the position of the greater palatine (GPF) and lesser palatine foramina (LPF) related to adjacent anatomical landmarks.

RESULTS

The perpendicular distance of the GPF to the midline sagittal suture was 1.53 cm and 0.3 cm from the inner border of the alveolar ridge. The mean distance from the posterior palatal border was consistent 0.46 cm on the right and 0.47 cm on the left side of the skulls. In the greater majority of the skulls (76.2%), the GPF were between proximal-distal surfaces of the 3rd maxillary molar. A single LPF was observed in 53.45% of the skulls, two LPF were observed in 31% of the skulls bilaterally and five LPF were rare (2.1%). The commonest position of LPF was at the junction of the palatine bone and the inner lamella of the pterygoid plate (71.9%).

CONCLUSION

Our results can help clinicians localize the palatine foramina in patients with and without maxillary molars and to predict the depth of a needle to anaesthetise the maxillary nerve with greater success when performing surgical procedures in the hard and soft palate.

Unusual presence of Wormian (sutural) bones in human skulls

Wormian bones are a subset of the small intrasutural bones that lie between the cranial sutures formed by the bones of the skull vault. They are formed due to additional ossification centres in or near sutures. They are usually considered as normal variants and seem to be determined genetically in certain populations. They have been linked with rapid cranial expansion as they appear in great number in hydrocephalic skulls. They are commonly found in the lambdoid suture and fontanelles but are occasionally seen in other sutures especially the coronal, squamosal, and sagittal sutures. We examined 25 dried human skulls with the aim to find out the occurrence and variations of Wormian bones, and surprisingly we found Wormian bones in the coronal, squamosal, and sagittal sutures in 6 skulls. These are uncommon sites of occurrence of sutural bones as reported in the literature. These findings prompted us to report these cases as their presence can lead to confusion in diagnosis in cases of skull fractures.

Anatomical consideration of pterion and its related references in Thai dry skulls for pterional surgical approach

OBJECTIVE

Pterion is a crucial surgical landmark for surgical approaches to the middle meningeal artery particular lesions, and tumors in the brain. The present study aimed to analyze the types of the pterion and its location related with nearby landmarks in dry skulls. In addition, variations of pterion in sex, age, and skull side were compared.

MATERIAL AND METHOD

Bilateral sides of 268 adult human Thai dry skulls were investigated Pterion types were classified as sphenoparietal, frontotemporal, epipteric, or stellate. To localize the pterion, linear distances were measured from the center of the pterion to neighboring landmarks.

RESULTS

The results showed the two most common types of the pterion, the sphenoparietal (81.2%), and the epiteric (17.4%). Externally, the pterion was commonly located 38.48 +/- 4.38 mm superior to the zygomatic arch and 31.12 +/- 4.89 mm posterior to the frontozygomatic suture. Internally, it was located 38.94 +/- 3.76 mm lateral to the optic canal and 11.70 +/- 4.83 mm from the sphenoid ridge. Sex influenced the occurrence of thepterion type, while sex, skull side, and age affected its location. Mean skull thickness at the pterion was 5.13 +/- 1.67 mm.

CONCLUSION

The pterion is predominantly sphenoparietal type and is typically located 39 mm superior to the zygomatic arch, 31 mm posterior to the frontozygomatic suture, 39 mm lateral to the optic canal and 12 mm from the sphenoid ridge. The data obtainedfrom the present study should be clinically useful for localizing the position of pterion.

Morphological investigation of cranial sutures in Indian human adult skulls

OBJECTIVES

The goal of the study was to evaluate the gross morphology of the coronal, sagittal and lambdoid sutures in human adult dried skulls and to determine if any difference exists in terms of patency.

MATERIALS AND METHODS

The study included 78 human dry skulls of Indian population. The coronal, sagittal and lambdoid sutures were analyzed using the modified grading scale (Sabini RC and Elkowitz DE, 2006) for quantifying the sutural patency. An open suture was graded as 0, a fused suture as 1 and an obliterated suture as 2, 3 or 4, depending on the extent of obliteration.

RESULTS

In coronal suture, the grade 1 suture was seen in 3.9%, grade 2 in 55.1%, grade 3 in 33.3%, and grade 4 in 7.7% of the cases. The sagittal sutures had grade 1 in 2.6%, grade 2 in 46.1%, grade 3 in 37.2%, and grade 4 in 14.1% of the cases. In contrast, the lambdoid suture showed 23.1% grade 1, 55.1% grade 2, 16.7% grade 3, and 5.1% grade 4 sutures. The grade 0 suture morphology was not observed in any of the skulls.

CONCLUSIONS

When compared with the coronal and sagittal sutures, the lambdoid suture was more likely to be patent. The prolonged patency of the lambdoid suture may be due to external forces acting on it. The greater number of muscles acting on the lambdoid suture compared to coronal and sagittal sutures may be considered as the cause. We believe that, these findings may be helpful to the researchers who are interested in biomedical science and osteopathic manipulative medicine. The findings are also enlightening for the neuroscientists, morphologists, anthropologists and clinicians.

Three-dimensional cranial suture morphology analysis

The aim of the study was to assess the normal and synostosed coronal cranial sutures morphology at an ultrastructural level. Different operative specimens of human coronal sutures were collected. Three-dimensional reconstruction of the microcomputed tomography (micro-CT) slices were obtained and compared with the representative histologic sections. The micro-CT scanning provides a three-dimensional view of the sutures at a microscopical level thus allowing to establish the stage of development and the bone morphology. The micro-CT has the advantage of being able to image more slices than the normal histology without any damage to the analyzed specimens. Micro-CT is a powerful tool in the craniofacial area that allows us to obtain many structure-orientated slices and in conjunction with the histologic sections provides an overall thorough quantitative analysis of all cranial sutures.

[Cranial osteopathy as a complementary treatment of postural plagiocephaly]

For the majority of neonates and young infants, appropriate postures and standard physiotherapy succeed in preventing or correcting acquired cranial deformations (fetal due to restricted mobility in utero or postnatal secondary to exclusive dorsal decubitus). However in some cases, when postural management is not efficient, pediatricians will be asked by the parents about the potential benefits of osteopathy. What is osteopathic treatment? At first, diagnostic palpation will identify which suture is normally mobile with the respiratory cycle, and which has limited or absent mobility secondary to abnormal postures. Later on, the goal of the therapeutic phase is to mobilise impaired sutures, by various gentle maneuvers depending on the topography of the impairment. The treatment is not restricted to the skull but extended to the spine, pelvis and lower extremities which contribute to the deformative sequence. Osteopathic treatment belongs to complementary medicine, therefore demonstration of its scientific value and favorable results have to be provided. Based on randomized studies, the answer is yes, it significantly decreases the degree of asymmetry. Do postural deformations matter to the development of an healthy infant? It seems that the prejudice is not only esthetic but also functional, however more research is necessary. In conclusion, pediatricians should be more aware of the method and expectations: major deformative sequence since birth and increasing deformations despite preventive postures and standard physiotherapy are reasonable indications for such complementary treatment. "Preventive" osteopathy in maternity is not justified. Moreover osteopathy has no place in the treatment of craniosynostosis ; the latter belong to malformations, completely distinct from postural deformations.

Postoperative nursing care of the endoscopic nonsyndromic craniosynostosis surgery patient

Craniosynostosis affects 1 in 2,100 children. The current methods for the treatment of craniosynostosis at Rady Children's Hospital, San Diego, are open cranial vault remodeling and the minimally invasive endoscopic technique. The primary advantages of the minimally invasive endoscopic technique are decreased operative time, blood loss, swelling, incision size, and inpatient hospital stay. Postoperative helmet therapy is a necessary part of the treatment for the refinement of the surgical result. The purpose of this article is to present current inpatient and outpatient nursing management considerations in the care of infants undergoing the minimally invasive endoscopic technique for the treatment of craniosynostosis.

[Biomechanical properties of the human cranium: aging aspects]

Biomechanical properties of the human skull affect its dynamic tensility (pliability, compliance) by changes of intracranial volume and pressure (deltaV/deltaP). The goal of this study is to substantiate a possibility of noninvasive and dynamic evaluation of cranial compliance. The transcranial dopplerogram of middle cerebral artery and hemispheric bioimpedance were synchronously recorded, which represent information about pulsative changes of intracranial pressure and volume, respectively. The parameters were recorded at rest and during adequate hemo- and liquorodynamic tests in different age groups--20-30, 40-50, and 70-85 years. As compared with the young group, a decrease of the cranial compliance in the intermediate age group was revealed due to an observed increase if rigidity of skull bones and ligaments, which indicates a decrease of stability of the intracranial circulatory system. However, in the group of 70-85 years the compliance rose again due to an enlargement of intracranial liquor spaces and facilitation of liquor circulation inside the intracranial cavity; this can be suggested to be a compensatory mechanism for supporting the adequate brain circulatory-metabolic state.

Establishment of nomograms and reference ranges for intra-cranial ventricular dimensions and ventriculo-hemispheric ratio in newborns by ultrasonography

AIM

To establish normal ranges for the lateral, third, and fourth ventricular dimensions and the ventriculo-hemispheric ratio (VHR) in neonates using cranial ultrasonography.

METHOD

Intra-cranial ventricles were assessed ultrasonographically using anterior fontanelle as acoustic window. Data were analyzed to determine correlation, coefficient of determination (R2), regression equations and plotted against gestational age (GA).

RESULTS

Of total 1483 neonates (25-42 w GA), 372(25%) had GA < 34 weeks. GA strongly correlated with anterior horn width (AHW; 0.92), thalamo-occipital distance (TOD; 0.94), and third (0.78) and fourth (0.89) ventricular widths. The R2 values were 0.85, 0.88, 0.66 and 0.80, respectively. VHR had weak correlation (0.12, R(2)= 0.005) with GA and stayed constant (0.27-0.28) across GA. Nomograms of AHW, TOD, and third and fourth ventricular widths were constructed with respect to GA.

CONCLUSION

Intra-cranial ventricles increase in size with GA but this increase is limited to only a few mm and is proportional to increment in brain tissue. Nomograms and regression equations of AHW, TOD and widths of third and fourth ventricles can assist in objectively assessing ventricular sizes. The almost uniform VHR can be used to screen ventricle size while suspecting hydrocephalus.

On the effect of cranial deformation in determining age from ectocranial suture closure

Available techniques for determining age from human cranial remains are limited. This study examines the efficacy of Meindl and Lovejoy's (1985) method of determining age based on ectocranial suture closure patterns as compared to a baseline of ages developed from a multifactorial approach employing various age determining factors from across the skull. What makes this study different is that the sample upon which this comparison is performed contains a large number of artificially deformed crania. Our hypothesis is that aging techniques that rely on suture closure patterns as markers are complicated by the results of artificial modification of the cranial vault. The study is conducted on adult, human crania from prehispanic archaeological sites in South America. Results demonstrate a significant difference between the two aging methods, more particularly when applied to deformed skulls. We conclude that when a skull is deformed age should be estimated utilizing multiple factors that exclude Meindl and Lovejoy's ectocranial suture aging technique.

Suture neontology and paleontology: the bases for where, when and how boundaries between bones have been established and have evolved

Much of what has been written about sutures has either focused on the genetic and biologic etiologies of specific sutural development, maintenance, and pathogenesis or on the utilization of sutures as character states in vertebrate cladistic analyses. There is a much more modest literature explicitly concerned with the evolution of sutures. We provide a small bridge of these literatures by presenting a discussion of the evolutionary biologic bases for the patterns of where, when, and how sutural boundaries between skeletal and dental elements have been established and have evolved. As sutural boundaries do not exist in the absence of the nucleation events that initiate the generation of skeletal elements, we explore historic models seeking to identify the inductive events dictating the specific times and places where a cranial skeletal element forms, the elaboration of its sutural boundaries, and the mechanisms whereby subsequent phyletic changes may be manifested and recognized.

The size of anterior fontanel in neonates and infants in Addis Ababa

INTRODUCTION

Assessment of the size of the anterior fontanel is a part of the routine examination in neonatology and pediatrics. Knowledge of the normal variations in AF size may be helpful in the early recognition of disorders. The mean size of the AF in neonates and infants in Addis Ababa is not known and the current looks in to this issue.

METHODS

A cross sectional study was carried out on 687 apparently healthy neonates and infants who were seen consecutively from January 2003 to December 2003.

RESULTS

There were 363 males and 324 females at the ages of 3, 46, 76, 106 and 270 days. The mean of anterior-posterior and lateral dimensions was considered to be the size of anterior fontanel. The mean AF size at the age of 3 days was 3.35 +/- 0.94 cm and showed a decline in the respective postnatal ages. 0.8% of infants at the age of 76 days had closed AF and the percentage of closure rose to 2.3 and 39.6 at the ages of 106 and 270 days respectively.

CONCLUSION

This study supported previous reports indicating racial difference in the size and time of closure of AF. The size and time of closure of AF are used to monitor the development of brain and general state of health of the individual. Further study is recommended indifferent parts of Ethiopia to establish age-related standard of AF size.

[Verification of the method for estimating age-at-death using maxillary suture obliteration in Japanese]

The method for estimating age-at-death of human skeletal remains based on the morphological changes of maxillary sutures is widely accepted in Japan. This method is based on the work of Kamijo (1949), which describes the age-related alternations in the morphology of maxillary sutures in Japanese population. However, from the modern anthropological viewpoint, Kamijo's report has some serious flaws in the definition of the morphology of the sutures as well as in the quality and quantity of the samples. Despite these problems, no verification has been conducted for the validity of estimating age-at-death based on his data. Recently, Mann et al. (1991) published a new method for estimating skeletal age based on the progressive obliteration of maxillary sutures. However, there has been no report that verified the effectiveness of their method in Japanese. In the present study, we re-examined the age-related alternations in the morphologies of maxillary sutures in Japanese and assessed the effectiveness of the method of Mann et al. (1991) by using 375 (274 males and 101 females) Japanese skeletons of known sex and age. In all maxillary sutures, the morphological transitions from "no obliteration" to "partial obliteration" with age could be confirmed. However the transition from "partial obliteration" to "complete obliteration" with age could be seen only in the incisive suture and the posterior median palatine suture. Moreover the percentage of each morphology of suture to a total within each decade shows almost no change over fifth decade. By using the method of Mann et al., we could correctly estimate the age-at-death of only 36.9% for males and 25.7% for females of the Japanese samples, however, we seldom overestimated the age-at-death of these samples compared with their actual age. This finding suggests that this method is applicable to estimate the minimum age-at-death in Japanese population.

Cell proliferation and osteogenic differentiation of growing pig cranial sutures

Bone growth at the cranial sutures relies on proliferation of osteogenic progenitor cells and/or differentiation of osteoblasts. The current study was undertaken to assess these events in relation to suture growth and fusion. A total of 21 pigs, divided into three age groups (0.5-1.5 months, 3-4 months and 5-7 months), were used for immunohistochemical evaluation of cell proliferation (BrdU) and osteogenic differentiation (Cbfa1/Runx2) in the interfrontal and interparietal sutures. Proliferation and osteogenic differentiation were both more prominent near the bone fronts than in the central zone. With age, both proliferation and osteogenic differentiation diminished. Proliferation ceased on the endocranial (dura mater) side by the age of 3-4 months. Proliferation on the pericranial side was accompanied by active bone formation and initiation of suture fusion from this side. In conclusion, (1) decreased suture bone growth with age reflects decreased cell proliferation and probably also osteogenic differentiation, and (2) suture fusion occurs from the pericranial side where activity remains relatively high.

The mendosal suture of the occipital bone: occurrence in Indian population, embryology and clinical significance

The occipital bone is ontogenetically and functionally unique when compared to the other bones of the skull in humans and other mammalian cousins. The occipital bone develops from six ossification centers; any defect in the ossification process will give rise to mendosal suture (accessory suture) and conditions like posterior plagiocephaly. There is a paucity of literature regarding the mendosal suture and further more, its report in Indian population is not known. The present study was conducted to find out the occurrence of mendosal suture in the Indian dry skulls. Fifteen specimens (3%) were found to have these sutures out of five hundred (500) skulls examined. Nine (3.1%) samples are of male skulls out of two hundred ninety (290) and six (2.85%) samples are that of female skulls out of two hundred ten (210). The mendosal suture ran close to the superior nuchal line in all specimens and traveled medially from the lambdoidal suture. The length of the sutures ranged from 0.8 cm to 2.6 cm (1.88 cm) on the right side and 1.4 cm to 2.9 cm (1.94 cm) on the left side respectively in male skulls; and 0.7 cm to 2.8 cm (1.55 cm) on the right side and 1 cm to 2.4 cm (1.42 cm) on the left side, respectively, in female skulls. The origin of mendosal suture from the lambdoidal suture was 5.7 cm to -6.3 cm (5.98 cm) from the tip of the mastoid process on the right side and 5.6 to -6.3 cm (6 cm) on the left side, respectively, in male skulls; and 5.4 cm to -5.8 cm (5.58 cm) on the right side and 5.4 cm to -5.6 cm on the left side respectively in female skulls. The occurrence and clinical significance of the present study is discussed.

Terrestrial-style feeding in a very early aquatic tetrapod is supported by evidence from experimental analysis of suture morphology

There is no consensus on when in the fish-tetrapod transition suction feeding, the primary method of prey capture in the aquatic realm, evolved into the direct biting on prey typical of terrestrial animals. Here, we show that differences in the morphology of selected cranial sutures between species that span the fish-tetrapod transition (the Devonian osteolepiform fish Eusthenopteron, the aquatic Devonian tetrapod Acanthostega, and the Permian terrestrial tetrapod Phonerpeton) can be used to infer when terrestrial feeding first appeared. Our approach consists of defining a sutural morphospace, assigning functional fields to that morphospace based on our previous measurements of suture function made during feeding in the living fish Polypterus, inferring the functions of the fossil sutures based on where they fall in the morphospace, and then using the correlation between feeding mode and the patterns of inferred suture function across the skull roof in taxa where feeding mode is unambiguous to infer the feeding mode practiced by Acanthostega. Using this procedure, we find that the suture morphologies of Acanthostega are inconsistent with the hypothesis that it captured prey primarily by means of suction, which suggests that it may have bitten directly on prey at or near the water's edge. Thus, our data strongly support the hypothesis that the terrestrial mode of feeding first emerged in aquatic taxa.

Does the mendosal suture exist in the adult?

There is a paucity of information in the literature regarding the mendosal suture. Furthermore, reports of the closure of this presumed suture of childhood are variable. This study seeks to establish the presence or absence of this structure in the adult. Fifty adult skulls were evaluated for the presence or absence of the mendosal suture. Sixteen percent of specimens were found to have a mendosal suture. Six specimens were found to have these sutures bilaterally, and two had sutures on the right side only. Most sutures were linear in nature. The mendosal suture approximated the superior nuchal line in all specimens and more or less traveled medial and perpendicular to the lambdoidal suture. The length of these sutures ranged from 0.8 to 1.4 cm (1.1 cm). Our hopes are that these data will prove useful to both the anatomist and clinicians, so that, when present, misinterpretation of the mendosal suture will be avoided.

Anatomical modifications of the mid palatal suture during ageing: a radiographic study

In transverse maxillary deficiencies it is important to know if the mid palatal suture is obliterated or not, to decide which treatment to perform (orthodontic expansion or surgical disjunction of the suture). The maxillary sutures obliteration has been used in forensic medicine in estimating adult age at death. In order to determine the proportion of mid palatal suture obliteration in the elderly in man, we examined 100 consecutive CT scans of the palate. This study has shown that the age of mid palatal total obliteration was variable. The obliteration begins in the anterior and in the superior part of the palate. The inferior part of the junction between the palatal processes is the last part of the suture to be obliterated.

Linking form and function of the fibrous joints in the skull: a new quantification scheme for cranial sutures using the extant fish Polypterus endlicherii

The aim of this study is to connect specific sutural morphologies with the specific types of deformation they experience. To meet this goal, we quantified the morphologies of the interfrontal (IF), interparietal (IP), and frontoparietal (FP) sutures in the extant fish Polypterus endlicherii, and used our published measurements of in vivo deformation of these sutures during feeding to infer how suture morphology and function are connected. Specifically, we found that three relatively simple measures of cross-sectional suture complexity (i.e., the ratio of total sutural length to its shortest end-to-end length; amount of sutural overlap; and size of the largest interdigitation) can be used to distinguish between the IF, FP, and IP sutures, which exhibit very different cross-sectional shapes and responses to loading. Interestingly, these differences in cross-sectional morphology are not reflected by the linear traces of these sutures on the surface of the skull, implying that cross-sectional shape of a suture must be known to infer the loading conditions it experiences. Plotting the three cross-sectional metrics against one another to yield a sutural morphospace shows that the IF, IP, and FP sutures define regions that are largely distinct from one another. Our previous measurements of strain across these sutures suggested that the FP region would lie between the IF and IP regions; instead, the FP region is largely set apart from the other two fields. Based on this discovery, and on the locations of cranial muscles, we propose a new model of deformation in the skull of P. endlicherii during feeding, in which rotation parallel to the skull roof is combined with bending, subjecting the FP suture to complex shearing. Finally, although the sutures of P. endlicherii appear to be significantly less complex than those of mammals, these fish sutures show a similar range of morphologies and perform similar functions as do mammalian sutures.

The suprapetrosal craniotomy

Object

The primary aim of this study was to establish standard sites for bur holes that maintain constant anatomical relationships with the skull base and neural structures and can serve as the basal aspect of supratentorial temporooccipital craniotomies.

Methods

To determine cranial–cerebral relationships, the authors created bur holes in 16 adult cadaveric skulls. Three bur holes were made on each side of the skulls (32 cerebral hemispheres). The authors then introduced plastic catheters through the bur holes to evaluate pertinent cranial and neural landmarks.

The first bur hole, located anterior to the auricle of the ear, appeared to have a particular anatomical relationship with the anterior aspect of the petrous portion of the temporal bone and the most anterior aspect of the midbrain. The second bur hole, whose base was located 1 cm above the interface of the parietomastoid and squamous sutures, had a particular relationship with the posterior border of the petrous portion of the temporal bone and with the posterior aspect of the midbrain. The third bur hole, whose base was located 1 cm above the asterion, was mostly supratentorial and particularly related to the preoccipital notch.

Conclusions

The preauricular bur hole and the bur hole whose base was located 1 cm above the interface of the parietomastoid and squamous sutures delimit anteriorly and posteriorly the external projection of the petrous bone and the midbrain. The middle fossa floor is located anterior to the site of the preauricular bur hole, and the superior surface of the tentorium is posterior to the bur hole located above the parietomastoid–squamous suture interface. Together with the bur hole whose base is located above the asterion, these bur holes can be considered standards for temporooccipital craniotomies.

Three-dimensional finite-element analysis of maxillary protraction with and without rapid palatal expansion

The aims of this study were to determine the reaction of the craniofacial bones on the protraction force transferred to the maxillary body, and whether or not the midpalatal suture had opened during skeletal Class III treatment. A computerized tomograph was obtained from a dry skull with a normal occlusion to construct a three-dimensional finite-element model (3D.FEM) of the craniofacial bones and the maxillary teeth to simulate actual bone reactions. A protraction force of 500 g was applied at the first premolar region, directed 20 degrees inferior to the occlusal plane. The displacement and the stress distribution of the craniofacial bones and sutures were then calculated using the ANSYS 5.3 program dividing the analysis into two simulations, based on whether or not the midpalatal suture was opened. The results showed that there was less compressive stress and greater tensile stress in the circumaxillary suture areas when the midpalatal suture was opened. The amount of displacement and deformation when the midpalatal suture was opened also demonstrated a decrease in upward-forward rotation of the maxilla and zygomatic arch and greater amounts of displacement in the frontal, vertical, and lateral directions compared with no opening of the midpalatal suture. Analysis of these results showed that maxillary protraction produce similar changes to normal downward and forward growth of the maxilla and was achieved with accompanying opening of the midpalatal suture.

Scanning electron microscope and micro-CT evaluation of cranial sutures in health and disease

Current knowledge of suture biology has been ascertained as a result of morphological studies of normal cranial sutures (and rarely those undergoing craniosynostosis). These were initially undertaken often using histological investigations, or more recently using CT scans, as investigative tools, but have often used animal models. However, recent technological advances have provided the potential to refine our understanding of the ultrastructure by the use of new advanced scanning technology, which offers the possibility of more detailed resolution. Our aim was to undertake detailed scans of normal, fusing and fused sutures from patients with craniosynosotosis affecting different sutures, to study the detailed structure at different stages of the fusion process using a modern micro-CT scanner and a microanalytical scanning electron microscope. We wished to include in our study all the human sutures because previous studies have mostly been undertaken using the sagittal suture. Ten sutures from seven patients have revealed a complex ultra-structural arrangement. The different patterns of bone ridging seen on the ectocranial and endocranial surfaces of the fused sagittal suture were not repeated on closer inspection of either fused coronal or lambdoid sutures. Elemental analysis confirmed that the amount of calcium increased and the amount of carbon decreased as sampled areas moved away from the suture margin. We conclude that scanning allowed detailed assessment and revealed the complex arrangement of the structure of the human cranial sutures and those undergoing the process of craniosynostosis, with some differences in final structure depending on the affected suture.

Inheritance of sutural pattern at the pterion in rhesus monkey skulls

Five of the bones that characteristically comprise the cranial vault articulate on the lateral aspect of the skull at or near the cephalometric landmark referred to as the pterion. The pattern of articulation in the sutures associated with these bones varies among and within primate species and has been used as a criterion for classification in taxonomic studies, as well as in archeological and forensic studies. Within species, the sutural patterns found within the region of the pterion have remarkable consistency, which lead to the hypothesis that these patterns have a genetic basis. Sutural pattern variations were investigated at the pterion in 422 skulls from 66 rhesus monkey families with known genealogies from the long-standing colony on Cayo Santiago. Four specific types of articulation patterns were recorded. The results demonstrated that the most common suture pattern at the pterion of Cayo Santiago rhesus monkeys (86%; similar to that seen in some other anthropoid species but not humans and some apes) was characterized by an articulation between the temporal bone and parietal bone. Articulation between the sphenoid and parietal bones (type SP) accounted for 14% of the specimens and was concentrated in a dozen families. Mothers with the SP phenotype had a high incidence of offspring with SP phenotypes. Most non-SP mothers having SP offspring had siblings or family members from previous generations with the SP type. This is the first study to examine variation in sutural patterns at the pterion in pedigrees. Variation of sutural patterns shows familial aggregation, suggesting that this variation is heritable. Future work will be focused on defining the inheritance patterns of variation at the pterion, with the ultimate objective of identifying the specific genes involved and their mechanism of action.

Significance of differences in patency among cranial sutures

OBJECTIVE

To evaluate the gross external characteristics of the coronal, lambdoid, and sagittal sutures in human cadaver skulls and determine if a difference exists in terms of patency, sex, and age.

METHODS

The coronal, lambdoid, and sagittal sutures were described using a modified grading scale to quantify sutural patency. An open suture was graded as 0, a fused suture as 1, and an obliterated suture as 2, 3, or 4, depending on the extent of obliteration.

RESULTS

Thirty-six skulls were examined, including 17 female and 19 male (age range, 56-101 y). When compared with the sagittal suture, the lambdoid suture was significantly more likely to be patent and least likely to be obliterated. No significant difference in suture grades was found between female and male skulls, and no significant difference was found between age and suture grade.

CONCLUSION

The prolonged patency of the lambdoid suture may be due to external forces, such as the greater number of muscles affecting the lambdoid suture when compared with the sagittal suture.

Asterion as a surgical landmark for lateral cranial base approaches

INTRODUCTION

When approaching the posterior fossa and posterolateral cranial base, surface landmarks are helpful in locating the junction of the transverse and the sigmoid sinus.

MATERIAL AND METHODS

On 100 skull halves a 2mm drill bit was externally placed over the asterion and was drilled through the bone perpendicular to the skull surface. Various positions of the asterion and its distance from the root of the zygomatic process of the temporal bone, from the suprameatal crest and the mastoid tip were investigated.

RESULTS

The position of the asterion has been found to be located superficial to the transverse-sigmoid sinus junction in 87% of all samples, inferior to the transverse-sigmoid sinus junction in 11% and superior to the transverse-sigmoid sinus junction in 2%. The distance from the asterion to the root of the zygoma has been determined to be 54.6+/-5.5mm. The distance between asterion and Henle's spine was 45.2+/-5.2, and from asterion to Frankfurt Horizontal Plane 15+/-7.5mm.

CONCLUSION

Asterion varies regarding its cephalocaudal position. The findings of this study might have direct consequences for transmastoid and retrosigmoid approaches for microvascular trigeminal root decompression and combined petrosal approaches.

Implant anchorage in orthodontic practice: the Straumann Orthosystem

Dental implants have been used to provide orthodontic anchorage. This article provides an overview of the Straumann Orthosystem implant system (Institut Straumann, Waldenburg, Switzerland) and its application, including the anatomy of the bony palate and contiguous structures. Considerations in placement of the Orthosystem implant include the avoidance of contiguous anatomic structures such as the nasal cavity, the degree of ossification of the palatal suture, and the quality and quantity of bone in the proposed implant site, all of which are discussed in this article.