Cranial Surface Research Articles

Neurosurgical skills conference for medical students: A before and after study

Background: Undergraduate conferences may improve exposure to neurosurgery among medical students. Hence, this study aimed to evaluate the effect of a neurosurgical skills conference on medical students’ comprehension and perceptions of the specialty. Methods: A before-and-after (BA) study design was employed to assess the effects of a conference that integrated presentations with hands-on sessions. Practical workshops covered craniotomy, spinal fixation, surface anatomy, intracranial pressure (ICP) monitoring, basic surgical skills, and microsurgical simulation. Pre-conference and post-conference surveys, utilizing Likert scales, gauged participants’ attitudes, prior neurosurgical exposure, and understanding of neurosurgical skills. Statistical analysis was conducted on dichotomized responses. Results: Thirty-one participants completed both surveys, with the majority being 1st and 2nd-year medical students. Among the participants, 58.1% were female, and 77.4% identified with BAME ethnicities. Following the conference, there was a notable increase in comprehension regarding neurosurgical careers (from 58.1% to 96.8%, P < 0.001) and training criteria (from 22.6% to 93.5%, P < 0.001). The conference enhanced knowledge of indications for craniotomy (P < 0.001), ICP monitoring (P < 0.001), and spinal fixation (P < 0.001). Participants reported improved understanding of the steps involved in craniotomy (P < 0.001), familiarity with basic cranial surgical surface anatomy (P < 0.001), and confidence in performing basic surgical instrument ties (P < 0.001). Although interest in pursuing a career in neurosurgery remained high (from 87.1% to 90.3%, P = 1.000), a majority of participants, both BA the conference, expressed concerns about the impact on personal life (from 58.1% to 64.5%, P = 0.774). Conclusion: This study underscores the role of undergraduate mixed-method conferences in augmenting understanding of neurosurgery and nurturing early interest.

Geometric Morphometric Study on Distinguishing Metopic Craniosynostosis from Metopic Ridging.

Craniosynostosis, a common congenital anomaly, results from premature fusion of the cranial sutures. One of the forms of craniosynostosis is premature fusion of the metopic suture, referred to as trigonocephaly, but the diagnosis of metopic suture synostosis remains controversial. The purpose of this study was to clarify, using geometric morphometric analysis, if a metopic ridge alone observed in cases of mild trigonocephaly represents a pathological phenomenon. Three different cranial morphologies were compared among patients up to 2 years old who were categorized into the true group, the mild group, and the normal group, based on the presence or absence of specific symptoms, history of cranioplasty for trigonocephaly, or lack of any abnormality on computed tomography. Using the obtained computed tomography images, 235 anatomical landmarks and semi-landmarks were plotted on the entire cranial surface for analysis of neurocranial morphology, and the cranial shapes represented by landmarks were analyzed using geometric morphometrics. Principal components of shape variations among specimens were then computed, based on the variance-covariance matrix of the Procrustes residuals of all specimens, and statistically analyzed. The principal component analyses of the variations in endocranial shape, frontal bone shape, and occipital bone shape did not show any significant differences in cranial morphology between mild trigonocephaly and normal skulls; however, true trigonocephaly was found to differ significantly from mild trigonocephaly and normal skulls. These findings suggest that in assessments of cranial morphology, the presence of a ridge alone cannot be diagnosed as fundamentally pathological, and may represent normal morphology.

Carotid web catheter angiography hemodynamic parameters

BackgroundCarotid web (CaW)-related contrast stagnation on digital subtraction angiography (DSA) may be a marker supporting the pathophysiological theory of stasis and thrombosis/embolization. We aim to assess the correlation between DSA...

Circumscribed Thinning of the Calvaria - A Long-Term Sequela After Vacuum Extraction Delivery

Abstract Background Vacuum extraction deliveries are associated with a number of complications like injuries to the skin, subperiosteal, subgaleal and intracranial hemorrhages. Even skull fractures have been described, but data on persistent changes in the bone structure of the skull like thinning of the calvaria is lacking in the literature. Aims We describe a previously unreported long-term sequela of vacuum extraction delivery. Methods We present a series of 8 children, who were referred because of an irregularity of the cranial surface without other symptoms. The investigations revealed a circumscribed thinning of the calvaria in all 8 cases. Detailed history and the specific clinical findings were crucial in the assessment. Various imaging techniques were used to visualize the lesions and rule out some differential diagnoses. Results All children had undergone a vacuum-assisted delivery. All irregularities of the cranial surface were discovered incidentally. Clinical examination revealed a round (6) or linear (1) channel-shaped indentation of the calvaria in 7 cases. The shape and size of the annular thinning of the calvaria matched devices commonly used in vacuum extraction very well. In one patient, a localized protrusion of the calvaria was investigated, but an indentation more posteriorly was detected in the CT scan. CT scan was performed in 6 patients, in 2, parents refused this examination. In the follow-up, no progression or symptoms was observed in any of the patients. Conclusion Such long-term sequelae after vacuum-assisted delivery have not been reported yet and the underlying mechanism is unclear. In children who present with irregularities of the cranium, an accurate history, including the mode of birth, and detailed clinical examination should be performed. Knowledge about the presented pathology may help to avoid extensive investigations, particularly CT scan. The publication of further cases could help to propagate the circumscribed thinning of the calvaria after vacuum extraction as a distinctive clinical entity.

The sequence of acrania–exencephaly–anencephaly (AEAS)- An infrequent case report

Acrania–exencephaly–anencephaly sequence has an incidence of 3.6–5.4 for 10,000 live births and has been reported in literature. Exencephaly, described here is a defect of the neural tube which occurs due to the absence of closure of the neural fold. The main diagnostic ultrasound features include that are characterized by acrania, decreased size of cranial pole in comparison with the chest, irregular cranial surface, with increased amniotic fluid echogenicity due to the damaged brain tissue. Associated with amniotic band syndrome, Pentalogy of Cantrell, limb anomalies and ventral body wall defects. It is incompatible with life. Conducting programs training the budding neuro-sonographers about the knowledge in detection, diagnosis of NTD according to the Carnegie Classification is crucial to look forward in pathogenesis and application in the clinical scenario.

Quantitative morphological analysis framework of infant cranial sutures and fontanelles based on CT images.

Characterizing the suture morphological variation is a crucial step to investigate the influence of sutures on infant head biomechanics. This study aimed to establish a comprehensive quantitative framework for accurately capturing the cranial suture and fontanelle morphologies in infants. A total of 69 CT scans of 2-4 month-old infant heads were segmented to identify semilandmarks at the borders of cranial sutures and fontanelles. Morphological characteristics, including length, width, sinuosity index (SI), and surface area, were measured. For this, an automatic method was developed to determine the junction points between sutures and fontanelles, and thin-plate-spline (TPS) was utilized for area calculation. Different dimensionality reduction methods were compared, including nonlinear and linear principal component analysis (PCA), as well as deep-learning-based variational autoencoder (VAE). Finally, the significance of various covariates was analyzed, and regression analysis was performed to establish a statistical model relating morphological parameters with global parameters. This study successfully developed a quantitative morphological framework and demonstrate its application in quantifying morphologies of infant sutures and fontanelles, which were shown to significantly relate to global parameters of cranial size, suture SI, and surface area for infants aged 2-4 months. The developed framework proved to be reliable and applicable in extracting infant suture morphology features from CT scans. The demonstrated application highlighted its potential to provide valuable insights into the morphologies of infant cranial sutures and fontanelles, aiding in the diagnosis of suture-related skull fractures. Infant suture, Infant fontanelle, Morphological variation, Morphology analysis framework, Statistical model.

Neuroscientific results of experimental studies on the control of acute pain with hypnosis and suggested analgesia.

This narrative review summarizes a representative collection of electrophysiological and imaging studies on the neural processes and brain sources underlying hypnotic trance and the effects of hypnotic suggestions on the processing of experimentally induced painful events. It complements several reviews on the effect of hypnosis on brain processes and structures of chronic pain processing. Based on a summary of previous findings on the neuronal processing of experimentally applied pain stimuli and their effects on neuronal brain structures in healthy subjects, three neurophysiological methods are then presented that examine which of these neuronal processes and structures get demonstrably altered by hypnosis and can thus be interpreted as neuronal signatures of the effect of analgesic suggestions: (A) On a more global neuronal level, these are electrical processes of the brain that can be recorded from the cranial surface of the brain with magnetoencephalography (MEG) and electroencephalography (EEG). (B) On a second level, so-called evoked (EPs) or event-related potentials (ERPs) are discussed, which represent a subset of the brain electrical parameters of the EEG. (C) Thirdly, imaging procedures are summarized that focus on brain structures involved in the processing of pain states and belong to the main imaging procedures of magnetic resonance imaging (MRI/fMRI) and positron emission tomography (PET). Finally, these different approaches are summarized in a discussion, and some research and methodological suggestions are made as to how this research could be improved in the future.

Anatomical and topographic substantiation of various accesses to the proximal epiphysis of the tibia

One of the most frequently performed accesses in the practice of an orthopedic veterinarian is access to the proximal epiphysis of the tibia. Access to the proximal epiphysis of the tibia is necessary in many cases of treatment of pathologies of the musculoskeletal system in cats and dogs and can be used in such surgical pathologies. The aim of the study was to consider options for surgical access to the proximal epiphysis of the tibia to perform osteosynthesis of fractures according to the Salter–Harris type, and osteotomy leveling the slope of the tibial plateau (TPLO) with anatomical and topographic justification. The study was conducted in the Network of veterinary centers "Kotonai" and the Department of Animal Anatomy of the St. Petersburg State University of Veterinary Medicine. The object of the study was dogs of small and medium breeds in the number of twelve individuals. The average age of the patients ranged from 6 months to 12 years. The study involved 5 intact females and 7 intact males. The average weight at the time of the study ranged from 2.5 to 21.0 kg. In the process of collecting the life history of all patients, the presence of chronic diseases, allergies and infectious diseases is excluded. The initial examination of the animal included: collection of anamneses of life and illness, general clinical examination, thermometry, neuroorthopedic examination, auscultation of the heart and lungs, X-ray examination under sedation. General clinical examination, thermometry and auscultation of the heart and lungs did not reveal pathological changes in all cases. According to the results of the study, it was found that there were no severe postoperative complications requiring repeated treatment in the studied patients. With the observance of clear anatomical and topographic landmarks in the formation of accesses, a good understanding of the anatomy of the medial and cranial surfaces of the tibia, visualization in the wound during surgical interventions (osteosynthesis of SalterHarris fractures, TPLO osteotomy) in the area of the proximal epiphysis of the tibia is convenient and safe.

In-vivo integration of soft neural probes through high-resolution printing of liquid electronics on the cranium

Current soft neural probes are still operated by bulky, rigid electronics mounted to a body, which deteriorate the integrity of the device to biological systems and restrict the free behavior of a subject. We report a soft, conformable neural interface system that can monitor the single-unit activities of neurons with long-term stability. The system implements soft neural probes in the brain, and their subsidiary electronics which are directly printed on the cranial surface. The high-resolution printing of liquid metals forms soft neural probes with a cellular-scale diameter and adaptable lengths. Also, the printing of liquid metal-based circuits and interconnections along the curvature of the cranium enables the conformal integration of electronics to the body, and the cranial circuit delivers neural signals to a smartphone wirelessly. In the in-vivo studies using mice, the system demonstrates long-term recording (33 weeks) of neural activities in arbitrary brain regions. In T-maze behavioral tests, the system shows the behavior-induced activation of neurons in multiple brain regions.

Anatomical and morphometric studies on the axial skeleton of ostrich (Struthio camelus)

The present study showed a descriptive anatomical study of the parts of the axial skeleton in the ostrich (Struthio camelus) in addition to a morphometric study of each bone. We studied 7 male ostriches aged from 1 to 3 years with an average weight of 120.00 kg. The cranium exhibited two vast orbits supported by a sclerotic ring. Hyoid apparatus was fine delicate horseshoe-shaped and comprised Basihyale, Urohyale, and Cornu branchiale. Cornu branchiale were paired and long rod-shaped, consisting of a proximal bony part Ceratobranchiale and slightly curved distal cartilaginous process, the Epibranchiale located on either side of the hyoid apparatus. The whole vertebral column comprised 54 vertebrae, including 18 cervical vertebrae, 7 separated thoracic vertebrae, a synsacrum, and 9 separated caudal vertebrae. Atlas had a butterfly-shape with a narrow width and large vertebral foramen. Axis had a protruded dens with a rounded tip that arose from the cranial surface of the body for articulation with the Incisura fossae of atlas. Several Pneumatic foramina were found in the cervical vertebrae. The transverse foramen was found in all the cervical vertebrae except atlas. The ribs were nine pairs in number, the sternal ribs extended from the third to the seventh rib while the rest were asternal floating ribs. The sternum was a broad quadrilateral extensive bone, lacking the keel bone. It had dorsally several Pneumatic foramina.

Functional Anatomy of Urogenital Hiatus Closure: the Perineal Complex Triad Hypothesis.

Urogenital hiatus enlargement is a critical factor associated with prolapse and operative failure. This study of the perineal complex was performed to understand how interactions among its three structures: the levator ani, perineal membrane, and perineal body-united by the vaginal fascia-work to maintain urogenital hiatus closure. Magnetic resonance images from 30 healthy nulliparous women with 3D reconstruction of selected subjects were used to establish overall geometry. Connection points and lines of action were based on perineal dissection in 10 female cadavers (aged 22-86years), cross sections of 4 female cadavers (aged 14-35years), and histological sections (cadavers aged 16 and 21years). The perineal membrane originates laterally from the ventral two thirds of the ischiopubic rami and attaches medially to the perineal body and vaginal wall. The levator ani attaches to the perineal membrane's cranial surface, vaginal fascia, and the perineal body. The levator line of action in 3D reconstruction is oriented so that the levator pulls the medial perineal membrane cranio-ventrally. In cadavers, simulated levator contraction and relaxation along this vector changes the length of the membrane and the antero-posterior diameter of the urogenital hiatus. Loss of the connection of the left and right perineal membranes through the perineal body results in diastasis of the levator and a widened hiatus, as well as a downward rotation of the perineal membrane. Interconnections involving the levator ani muscles, perineal membrane, perineal body, and vaginal fascia form the perineal complex surrounding the urogenital hiatus in an arrangement that maintains hiatal closure.

Aureispira anguillae sp. nov., isolated from Japanese eel Anguilla japonica leptocephali.

A novel filamentous eel-leptocephalus pathogenic marine bacterium, designated strain EL160426T, was isolated from Japanese eel, Anguilla japonica, leptocephali reared at a laboratory in Mie, Japan. In experimental infection studies on eel larvae, the strain EL160426T caused massive larval mortality and was reisolated from moribund leptocephali. Characteristically, observations of infected larvae found that EL160426T forms columnar colonies on the cranial surface of larvae. The novel isolate exhibited growth at 15-30°C, pH 7-9, and seawater concentrations of 60-150% (W/V). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain EL160426T was most closely related to Aureispira maritima 59SAT with 97.7% sequence similarity. The whole genome sequence analysis of the strain EL160426T showed that the strain maintained a circular chromosome with a size of approximately 7.58Mbp and the DNA G + C content was 36.2%. The major respiratory quinone was MK-7 and the predominant cellular fatty acids were 16:0, 20:4 w6c (arachidonic acid), 17:0 iso and 16:0 N alcohol. DNA relatedness between the closest phylogenetic neighbor strain EL160426T and A. maritima (JCM23207T) was less than 13%. On the basis of the polyphasic taxonomic data, the strain represents a novel species of the genus Aureispira, for which the name Aureispira anguillae sp. nov. is proposed. The type strain is EL160426T (= JCM 35024T = TSD-286T).

Skeletotopic landmarks of the points of fixation of the quadriceps femoral muscle in representatives of canids

The article presents skeletotopic landmarks of the points of fixation of the quadriceps femoral muscle in representatives of Canidae (shalayka and domestic dog), which are absent in the available literature. Thus, it was revealed that the straight head in the distal part of the shalaika is attached to the base of the cranial surface of the kneecap by tendon fibers, and in the domestic dog its muscle-tendon fixation was found. The research was carried out at the Department of Anatomy and Histology of Animals named after Professor A. F. Klimov of the Moscow State Academy of Veterinary Medicine and Biotechnology – MBA named after K. I. Scriabin. The material for the research was sectional material - pelvic limbs (n=16), selected from adult dogs and canine hybrids (shalayka), without external signs of musculoskeletal system pathologies. The methods of fine macro- and microanatomic dissection under the control of a Micromed HR 350 S binocular magnifier were used, followed by functional analysis of the studied structures and skeletotopic projection of muscle attachment points on the kneecap. When studying the structures located on the kneecap, it was found that the cranial head of the tailor's muscle and the wide fascia of the thigh, covering the cranial surface of the kneecap, connects to the underlying organs through loose connective tissue. However, at the top of the cranial tubercle, they closely fuse with the tendon of the rectus femoris muscle, as well as directly with the periosteum of the cranial tubercle of the kneecap, and then, covering the rectus ligament of the kneecap, continue into the fascia of the lower leg.

A New Measure of Posterior Morphology in Sagittal Craniosynostosis: The Occipital Bullet Index

Introduction: Sagittal craniosynostosis (SC) is associated with scaphocephaly, an elongated narrow head shape. Assessment of regional severity in the scaphocephalic head is limited by the use of serial computed tomographic (CT) imaging or complex computer programing. Three-dimensional measurements of cranial surface morphology provide a radiation-free alternative for assessing cranial shape. This study describes the creation of an occipital bulleting index (OBI), a novel tool using surface morphology to assess the regional severity in patients with SC. Methods: Surface imaging from CT scans or 3D photographs of 360 individuals with SC and 221 normocephalic individuals were compared to identify differences in morphology. Cartesian grids were created on each individual’s surface mesh using equidistant axial and sagittal planes. Area under the curve (AUC) analyses were performed to identify trends in regional morphology and create measures capturing population differences. Results: The largest differences were located in the medial regions posteriorly. Using these population trends, a measure was created to maximize AUC. The OBI has an AUC of 0.72 with a sensitivity of 74% and a specificity of 61%. When the frontal bossing index is applied in tandem, the two have a sensitivity of 94.7% and a specificity of 93.1%. Correlation between the two scores in individuals with SC was found to be negligible with an intraclass correlation coefficient of 0.018. Severity was found to be independent of age under 24 months, sex, and imaging modality. Conclusions: This index creates a tool for differentiating control head shapes from those with SC and has the potential to allow for objective evaluation of the regional severity, outcomes of different surgical techniques, and tracking shape changes in individuals over time, without the need for radiation.

Comparison of electrode position marking procedures on the cranial surface.

The study aimed to compare the conventional method of electrode marking with a new system, EPlacement, to improve accuracy and reduce the time burden on health care professionals. Ten health care professionals marked mannequin heads and adult volunteers using both methods. Time, accuracy, and usability of each method were analyzed. Three neurophysiological diagnostic tests were performed on mannequin heads: reversal pattern visual evoked potential (three electrodes required); somatosensory evoked potentials from the upper and lower extremities (five electrodes required); and standard intraoperative neurophysiological monitoring for spine surgery (nine electrodes required). Precision scanning of the mannequins with structured light and a printed hull were used to determine the actual locations of the electrodes of the 10/20 system. The new method based on the EPlacement device represents an improvement on conventional tape measure (TM) marking and may be considered within the group of advanced methods such as navigation systems since it leads to improvements of 34% (1.7mm) for electrode positions in the Nasion-Inion and Left tragus-Right tragus lines and 77% (12.5mm) for electrode positions using the approximate method. It reduces the time spent per test by an average of 1min compared to the TM method. Health care staff survey results show a positive feedback regarding usability of the new method. The study showed that the EPlacement device improves accuracy, reduces time, and is easy to use compared to the conventional method of electrode marking. The EPlacement method can facilitate the complex task of electrode marking and ultimately contribute to improved patient outcomes. It has the potential to be widely accepted and implemented in clinical practice.

Shapes of cervical articular process joints and association with histological evidence of osteochondrosis in Warmblood foals: A post-mortem study.

Osteochondrosis dissecans (OCD) of articular process joints (APJs) is involved in cervical vertebral compressive myelopathy (CVM). Biomechanical forces, important in development of OCD, depend on joint conformation. Oval and flat APJ surfaces are considered normal. To identify and grade gross shape variation of cervical and cranial thoracic APJ surfaces and determine association with histological evidence of osteochondrosis. Case series. Eight hundred and four cervical and cranial thoracic APJ surfaces of 30 foals were evaluated for shape(s) and grades, and were correlated with osteochondrosis. Three top view shapes (oval, pointed, elongated) and seven lateral view shapes (flat, convex, concave, stepped, bevelled, folded edge, raised edge) were regularly encountered. The oval top view shape was most common. Flat and bevelled were the most common lateral view shapes. General shape grade of caudal articular surfaces was significantly higher than of cranial surfaces. The combinations of an oval top view shape and the lateral view shapes folded edge, concave, or flat with additional raised edge and/or folded edge (flat +), were more likely to have OC than oval with convex, bevelled or flat lateral view shapes (normal vs. oval and folded, odds ratio [OR] 2.49 [95% confidence intervals (CIs) 1.13-5.67]; normal vs. oval and flat +, OR 2.77 [95% CI 1.15-6.85]; oval and convex vs. oval and folded, OR 3.20 [95% CI 1.35-8.20]; oval and convex vs. oval and flat +, OR 3.56 [95% CI 1.43-9.54]; oval and bevelled vs. oval and concave, OR 2.02 [95% CI 1.14-3.60]; oval and bevelled vs. oval and folded, OR 3.50 [95% CI 1.91-6.60]; oval and bevelled vs. oval and flat +, OR 3.90 [95% CI 2.00-7.70]). Most foals (21/30) were less than 1 month old. Lack of observer reliability scores for shape and shape grade. APJs shape might contribute to CVM by increased likelihood to have OC.

Three-dimensional geometric morphometric study of the Xuchang 2 cranium

Results of traditional metric and nonmetric assessments suggest that the Xuchang hominin shares features with Neanderthals. To comprehensively compare the nuchal morphology of XC 2 to those of the genus Homo, we conduct a three-dimensional geometric morphometric study with 35 cranial landmarks and surface semilandmarks of XC 2, Homo erectus, Middle Pleistocene humans, Neanderthals, and early and recent modern humans. Results reveal that the centroid size of XC 2 is larger than that of early and recent modern humans and can only be compared to that of Middle Pleistocene humans and H. erectus. Early and recent modern humans share a nuchal morphology distinct from archaic hominins (Ngandong H. erectus, Middle Pleistocene humans, and Neanderthals), except for SM 3, Sangiran 17, and Asian and African H. erectus. Although Ngandong specimens differ from the other H. erectus, it is unclear whether this represents a temporal or spatial trend in the process of evolution of this species. The nuchal morphological resemblance between Middle Pleistocene humans and Neanderthals may be attributed to similar cranial architecture and cerebellar shape. The great nuchal morphological variation shared by recent modern humans may indicate a particular developmental pattern. In conclusion, the nuchal morphology of different human groups is highly variable and may be caused by different factors including brain globularization and developmental plasticity. XC 2 shares similar nuchal morphology with Middle Pleistocene humans and Neanderthals, but these results are insufficient to fully resolve the taxonomic status of XC 2.

Icex: Advances in the automatic extraction and volume calculation of cranial cavities.

The use of non-destructive approaches for digital acquisition (e.g. computerised tomography-CT) allows detailed qualitative and quantitative study of internal structures of skeletal material. Here, we present a new R-based software tool, Icex, applicable to the study of the sizes and shapes of skeletal cavities and fossae in 3D digital images. Traditional methods of volume extraction involve the manual labelling (i.e. segmentation) of the areas of interest on each section of the image stack. This is time-consuming, error-prone and challenging to apply to complex cavities. Icex facilitates rapid quantification of such structures. We describe and detail its application to the isolation and calculation of volumes of various cranial cavities. The R tool is used here to automatically extract the orbital volumes, the paranasal sinuses, the nasal cavity and the upper oral volumes, based on the coordinates of 18 cranial anatomical points used to define their limits, from 3D cranial surface meshes obtained by segmenting CT scans. Icex includes an algorithm (Icv) for the calculation of volumes by defining a 3D convex hull of the extracted cavity. We demonstrate the use of Icex on an ontogenetic sample (0-19 years) of modern humans and on the fossil hominin crania Kabwe (Broken Hill) 1, Gibraltar (Forbes' Quarry) and Guattari 1. We also test the tool on three species of non-human primates. In the modern human subsample, Icex allowed us to perform a preliminary analysis on the absolute and relative expansion of cranial sinuses and pneumatisations during growth. The performance of Icex, applied to diverse crania, shows the potential for an extensive evaluation of the developmental and/or evolutionary significance of hollow cranial structures. Furthermore, being open source, Icex is a fully customisable tool, easily applicable to other taxa and skeletal regions.

A Comparison of Semilandmarking Approaches in the Visualisation of Shape Differences.

In landmark-based analyses of size and shape variation and covariation among biological structures, regions lacking clearly identifiable homologous landmarks are commonly described by semilandmarks. Different algorithms may be used to apply semilandmarks, but little is known about the consequences of analytical results. Here, we assess how different approaches and semilandmarking densities affect the estimates and visualisations of mean and allometrically scaled surfaces. The performance of three landmark-driven semilandmarking approaches is assessed using two different surface mesh datasets with different degrees of variation and complexity: adult human head and ape cranial surfaces. Surfaces fitted to estimates of the mean and allometrically scaled landmark and semilandmark configurations arising from geometric morphometric analyses of these datasets are compared between semilandmarking approaches and different densities, as well as with those from warping to landmarks alone. We find that estimates of surface mesh shape (i.e., after re-semilandmarking and then re-warping) made with varying numbers of semilandmarks are generally consistent, while the warping of surfaces using landmarks alone yields surfaces that can be quite different to those based on semilandmarks, depending on landmark coverage and choice of template surface for warping. The extent to which these differences are important depends on the particular study context and aims.

Realistic Facial Three-Dimensional Reconstruction from CT Images and 2D Photographic Images for Surgical-Orthognathic Planning

Orthognathic surgery is a procedure used to correct intermaxillary discrepancies, thus promoting significant improvements in chewing and breathing. During the surgical planning stage, orthodontists often use two-dimensional imaging techniques. The assessment is based on CBCT images and dental cast models to overcome these limitations; however, the evaluation of soft tissues remains complex. The aim of the present study was to develop a co-registration method of CBCT and photo images that would result in realistic facial image reconstruction. CBCT images were three-dimensionally rendered, and the soft tissues were subsequently segmented resulting in the cranial external surface. A co-registration between the obtained surface and a frontal photo of the subject was then carried out. From this mapping, a photorealistic model capable of replicating the features of the face was generated. To assess the quality of this procedure, seven orthodontists were asked to fill in a survey on the models obtained. The survey results showed that orthodontists consider the three-dimensional model obtained to be realistic and of high quality. This process can automatically obtain a three-dimensional model from CBCT images, which in turn may enhance the predictability of surgical-orthognathic planning.