Facial Projection Research Articles

The shrinking anthropoid nose, the human vomeronasal organ, and the language of anatomical reduction.

Humans and most of our closest extant relatives, the anthropoids, are notable for their reduced "snout." The striking reduction in facial projection is only a superficial similarity. All anthropoids, including those with long faces (e.g., baboons), have lost numerous internal projections (turbinals) and spaces (recesses). In sum, this equates to the loss of certain regions of olfactory mucosa in anthropoids. In addition, an accessory olfactory organ, the vomeronasal organ, is non-functional or even absent in all catarrhine primates (humans, apes, monkeys). In this commentary, we revisit the concept of anatomical reductions as it pertains to the anthropoid nasal region. Certain nasal structures and spaces in anthropoids exhibit well-known attributes of other known vestiges, such as variability in form or number. The cupular recess (a vestige of the olfactory recess) and some rudimentary ethmoturbinals constitute reduced structures that presumably were fully functional in our ancestors. Humans and at least some apes retain a vestige that is bereft of chemosensory function (while in catarrhine monkeys it is completely absent). However, the function of the vomeronasal system also includes prenatal roles, which may be common to most or all mammals. Notably, neurons migrate to the brain along vomeronasal and terminal nerve axons during embryogenesis. The time-specific role of the VNO raises the possibility that our concept of functional reduction is too static. The vomeronasal system of humans and other catarrhine primates appears to qualify as a "chronological" vestige, one which fulfills part of its function during ontogeny, and then becomes lost or vestigial.

Osteoplastic reconstruction of severely resorbed maxilla by stack plasty: combining sinus augmentation with lateral and vertical onlay bone grafting

Progressive loss of the alveolus with aging leads to defects in the buccolingual and vertical dimensions. Maxillomandibular spatial discrepancies and deficits in sagittal facial projection develop at the same time as deficiencies of the periodontal unit, alveolar bone, and attached gingiva increase, depending on the extent of the atrophy. To restore the anatomy, a sinus lift should be combined with lateral and vertical bony augmentation in an osteoplastic procedure. To achieve this, “block over block” replacement with bone from the iliac crest allows precise functional and aesthetic restoration of the alveolus and the nasomaxillary region by combining inlay, interpositional, and onlay grafting. To our knowledge, preprosthetic osteoplastic reconstruction with stacked bone grafts has not previously been documented with a large number of patients. We report the results of this procedure in 62 patients with severe maxillary atrophy.

Towards Characterizing the “Immunoscore” in the Tumor Microenvironment in Oral, Head and Neck Cancer

rehabilitation. Fibular free flaps were utilized to immediately reconstruct themaxilla andmandible in six patients, facilitating orthognathic jaw position, favorable facial projection, separation of the nose and mouth, and oral competence. The remaining patients were treated without microvascular free tissue transfer, but the virtual planning, pre-bent reconstruction plates, and intraoperative imaging significantly aided accurate reconstruction. Intraoperative CT scans facilitated recognition of minor inaccuracies in orbital plate placement in two patients, the position of which was corrected prior to leaving the operating room. Conclusion: Computer-aided presurgical planning, custom cutting guides and guide stents, and intraoperative imaging have the potential to favorably affect the functional and aesthetic outcomes of patientswith severe facial injuries resulting from gunshot wounds.

Utilization of Intraoperative 3D Navigation for Delayed Reconstruction of Orbitozygomatic Complex Fractures

Reconstructive goals for orbitozygomaticomaxillary complex fractures include restoration of orbital volume, facial projection, and facial width. Delayed reconstruction is made more difficult by malunion, nonunion, bony absorption, loss of the soft tissue envelope, and scar. Three-dimensional intraoperative navigation, widely used in neurosurgery and sinus surgery, can improve the accuracy with which bony reduction is performed. This is particularly useful in the setting of bony absorption and comminution. We report a case of delayed reconstruction of an orbitozygomaticomaxillary complex fracture using intraoperative navigation and review this technology's utility in this setting.

Craniofacial skeletal architecture and obstructive sleep apnoea syndrome severity

Obstructive sleep apnoea syndrome (OSAS) is a sleep related breathing disorder caused by pharynx obstruction that often terminates in abrupt arousals and is capable of disrupting physiological sleep profile. Its' severity has been associated, among others, with craniofacial skeletal morphology. To investigate this relationship and elucidate craniofacial skeleton patterns in individuals without obvious maxillofacial abnormalities, 171 OSAS patients were studied with nocturnal polysomnographic record and chephalometric X-ray (24 variables). Chephalometric variables were compared between three apnoea/hypopnoea index (AHI) groups (AHI ≤ 15; 15 < AHI < 30; AHI ≥ 30) and uni/multivariate analysis between chephalometric variables and AHI were performed.The patients were predominantly men (83%), with a mean age of 48.1 years. Mean BMI and AHI were 28.4 kg/m2 and 26.2, respectively. Most chephalometric variables differed among the three AHI groups. Fifteen chephalometric variables showed a correlation with AHI. Five chephalometric variables and BMI were independent AHI predictors. Chephalometric variables were better AHI predictors in normal weight patients.Significant evidence of craniofacial skeleton influence was found on OSAS severity, caudalization of the hyoid and lower sagittal facial projection being the most important patterns. From the chephalometric variables analysed, the hypopharynx calibre demonstrated a higher predictive value for AHI, independently of BMI.

Stereophotogrammetry-Based Facial Depth Measurements

Orthognathic surgery leads to alteration of the spatial relationship of the mandible and maxilla resulting changes in the degree of facial projection. Traditional 2-dimensional cephalometry and photographic techniques do not provide data on facial depth. Though stereophotogrammetry can be used as a noninvasive method for evaluating facial depth, the unavailability of ethnicity-specific norms hinder its routine use in clinical practice. The objectives of this study were to (a) generate an analytic scheme suitable for evaluating facial depth using stereophotogrammetry and (b) create normative data for the facial depth measurements for young Hong Kong Chinese adults. Stereophotographic images from 41 male and 45 female ethnic Chinese young adults without facial deformities were analyzed. Facial depth measurements were performed based on standard anthropometric landmarks, with the aid of 3dMDVultus software. All facial depth measurements were found in absolute terms to be significantly higher in males. In contrast, the upper face, maxillary, and sublabial depth indices were significantly higher in females, whereas no significant gender differences emerged for lower facial and maxillomandibular indices. A novel method of using stereophotographic images for quantifying facial depth was evaluated. Normative facial depth measurements for young Hong Kong Chinese adults were established. This gender-specific database can be used as a reference in the diagnosis, treatment planning, or evaluation of outcomes after surgical correction of facial deformities.

Prediction of lower incisor proclination during Xbow treatment based on initial cephalometric variables

To predict lower incisor proclination from initial cephalometric values in Class II division 1 patients treated in phase I with the Xbow appliance. Two hundred forty-nine mild to moderate Class II division 1 patients treated with the Xbow appliance as a phase I treatment were considered. Patients were in late mixed dentition or early permanent dentition. Commonly used cephalometric variables at T1 (before treatment) were used to predict lower incisor proclination after Xbow treatment (T2). A principal component analysis (PCA) was performed. The four extracted PCA components were skeletal component, incisal distance, anterior facial projection, and maxillo-mandibular relation. Thereafter, a multiple linear regression analysis (MLRA) was performed using the four extracted PCA components at T1 as predictor variables, and lower incisor inclination relative to the mandibular plane (L1-MP) at T2 as the dependent variable. The mean L1-MP at T1 was 95.46 degrees and the mean L1-MP at T2 was 98.51 degrees, resulting in a mean difference of 3.04 degrees. Only incisal distance and maxillo-mandibular relation PCA components had significance (P < .05) according to the MLRA. The overall model gave an adjusted R2 value (coefficient of determination) of 0.091. The best prediction model could account for only 9% of the total variability. Using common cephalometric variables at T1, average lower incisor proclination from Xbow treatment cannot be predicted in a clinically meaningful way.

The Correction of Post-Traumatic Pan Facial Residual Deformity

Disfiguring post-traumatic deformities of the midface sometimes persist even after the treatment. Such deformities, after healing, are among the most formidable challenges faced by the surgeons, apart from the psychological impact on the patients. Following the basic principles of craniofacial reconstruction and with newer techniques, better results can be achieved. Symmetry is key to proper reconstruction in general and face in particular. Proper facial projection and height must be re-established with harmonious occlusion. Our basic approach to the evaluation of deformities and particularly useful techniques for their correction are presented, with a representative case of malunited panfacial fracture that we treated with an iliac bone onlay grafting for zygoma along with correction of mandibular deformity by osteotomies.

Mechanical Impact of Incisor Loading on the Primate Midfacial Skeleton and its Relevance to Human Evolution

The midfacial skeleton in the human lineage demonstrates a wide spectrum of variation that may be the consequence of different environmental and mechanical selective pressures. However, different facial configurations may develop under comparable selective regimes. For example, the Neanderthal high and projected face and the Inuit broad and flat face are hypothesized to be the consequence of (1) life in a cold climate, and (2) excessive paramasticatory stresses focused on the anterior dentition. In this study, the second of these two hypotheses is tested using finite element analyses of a monkey skull. Results indicate that incisor loading induces heavy stress in the anterior midface of macaques. Additional analyses using incremental increases in the anteroinferior tilt of the skull to simulate different magnitudes of facial projection revealed that comparable muscular force generates less stress in a less-projected face. However, the findings of our final analyses, which attempted to combine biting with the incisors and pulling with the hands, differed from the analyses that mimicked only incisor loading (without any sort of anterior pulling component). These findings suggest that shortening the face may be the most effective way to compensate for anterior dental loading but not necessarily offset the forces incurred when using the anterior dentition as a vice for various paramasticatory behaviors. Although Neanderthals may have frequently loaded their anterior dentition, countervailing selection pressures, such as the inclusion of tough foods in the diet that demanded molar grinding, may have selected for a longer face with a lower load- to lever-arm ratio.

Sutural growth restriction and modern human facial evolution: an experimental study in a pig model.

Facial size reduction and facial retraction are key features that distinguish modern humans from archaic Homo. In order to more fully understand the emergence of modern human craniofacial form, it is necessary to understand the underlying evolutionary basis for these defining characteristics. Although it is well established that the cranial base exerts considerable influence on the evolutionary and ontogenetic development of facial form, less emphasis has been placed on developmental factors intrinsic to the facial skeleton proper. The present analysis was designed to assess anteroposterior facial reduction in a pig model and to examine the potential role that this dynamic has played in the evolution of modern human facial form. Ten female sibship cohorts, each consisting of three individuals, were allocated to one of three groups. In the experimental group (n = 10), microplates were affixed bilaterally across the zygomaticomaxillary and frontonasomaxillary sutures at 2 months of age. The sham group (n = 10) received only screw implantation and the controls (n = 10) underwent no surgery. Following 4 months of post-surgical growth, we assessed variation in facial form using linear measurements and principal components analysis of Procrustes scaled landmarks. There were no differences between the control and sham groups; however, the experimental group exhibited a highly significant reduction in facial projection and overall size. These changes were associated with significant differences in the infraorbital region of the experimental group including the presence of an infraorbital depression and an inferiorly and coronally oriented infraorbital plane in contrast to a flat, superiorly and sagittally infraorbital plane in the control and sham groups. These altered configurations are markedly similar to important additional facial features that differentiate modern humans from archaic Homo, and suggest that facial length restriction via rigid plate fixation is a potentially useful model to assess the developmental factors that underlie changing patterns in craniofacial form associated with the emergence of modern humans.

The paradox of a wide nasal aperture in cold-adapted Neandertals: a causal assessment

Neandertals have been characterized as possessing features indicative of cold-climate adaptation largely based on ecogeographical morphological patterning found in recent humans. Interestingly, one character that deviates from this pattern is a relatively wide nasal aperture. The ecogeographical patterning of the nasal aperture in recent humans would predict instead that Neandertals should exhibit reduced nasal breadth dimensions. To explain this apparent anomaly it has been argued that a reduction in Neandertal nasal breadth was not possible due to dentognathic constraints on their midfaces via large anterior palatal breadth dimensions, especially large intercanine distances. A complicating factor in understanding the relationship between anterior palate breadth and nasal breadth is that both measurements are also correlated with facial prognathism. It is, therefore, unknown to what degree the relationship between anterior palate breadth and nasal breadth in Neandertals is a function of the pleisiomorphic retention of a prognathic facial skeleton. We used path analysis to test for a causal relationship between intercanine breadth and nasal breadth taking into account the potential effect of facial projection and facial prognathism (i.e., basion-nasion length and basion-prosthion length) using a large sample of geographically diverse recent and fossil Homo. Additionally, we examined the ontogenetic relationship between nasal breadth and intercanine breadth using a longitudinal human growth series to determine whether these variables exhibit similar growth trajectories. The results of these analyses indicate a weaker association between intercanine breadth and nasal breadth than expected, and that more variation in nasal breadth can be explained through basion-prosthion length rather than anterior palatal breadth dimensions. Moreover, the ontogenetic development of anterior palate breadth does not correspond to the growth trajectory of the breadth of the nose. These results explain the apparent paradox of wide piriform apertures in generally cooler climate-adapted Neandertals without resorting to dentognathic constraints, and provide additional insight into both the adaptive and nonadaptive (i.e., neutral) basis for Neandertal facial evolution.

Microsurgical Reconstruction of Posttraumatic High-Energy Maxillary Defects: Establishing the Effectiveness of Early Reconstruction

Posttraumatic, high-energy defects of the midface can be challenging to reconstruct because they involve extensive composite tissue loss and result in significant permanent functional and cosmetic deformity. These injuries require replacement of the bony framework, external soft tissue, and intraoral mucosa. Local skin flaps and nonvascularized bone grafts have been used for reconstruction, but bony resorption and the associated soft-tissue collapse limit long-term viability. The authors present a classification of maxillary defects following high-energy trauma and a treatment algorithm using vascularized bone flaps. Fourteen patients with significant maxillary loss from high-energy trauma underwent reconstruction with composite vascularized bone flaps. Eight patients had fibula flaps and six had iliac crest flaps. There were five women and nine men, with a mean age of 36.3 years (range, 21 to 48 years) and a mean follow-up of 18 months (range, 5 to 54 months). Thirteen of the 14 flaps survived. Nine patients had additional procedures. Nine patients had oronasal fistulas and eight were dependent on gastrostomy tubes preoperatively. All patients were able to feed orally without nasal regurgitation postoperatively. All patients achieved stable restoration of the midfacial architecture. The classification scheme presented centers on the missing maxillary subunits. The reconstructive algorithm is based on the type of defect, tissue requirement, and donor tissues necessary to restore facial projection and prosthodontic rehabilitation. Iliac crest and fibula bone free flaps are ideal for restoring a variety of traumatic maxillary defects. The authors advocate early reconstructive intervention using vascularized bone flaps to achieve superior functional and cosmetic outcomes.

Craniofacial growth in fetal Tarsius bancanus: brains, eyes and nasal septa.

The tarsier skull has been of particular interest in studies of primate taxonomy and functional morphology for several decades. Despite this, there remains no comprehensive data on how the tarsier skull develops, especially in relation to the soft-tissues of the head. Here we have documented for the first time fetal development of the skull and brain as well as the nasal septum and eyes in T. bancanus. We have also tested for the possible influence of these tissues in shaping skull architecture. Nineteen post-mortem specimens were imaged using high-resolution magnetic resonance imaging and magnetic resonance microscopy. Landmarks and volume data were collected and analysed. Findings demonstrated massive increases of brain size and eye size as well as flattening of the midline cranial base, facial projection and orbital margin frontation. Little evidence was found to support the notion that growth of the brain or nasal septum physically drives the observed changes of the skull. However, increases in the size of the eyes relative to skull size were associated with orbital margin frontation. With the possible exception of the results for eye size, the findings indicate that rather than forcing change the soft-tissues form a framework that physically constrains the morphogenetic template of the skeletal elements. This suggests, for example, that the degree of cranial base angulation seen in adulthood is not directly determined by brain expansion bending the basicranium, but by brain enlargement limiting the extent of cranial base flattening (retroflexion) in the fetus.

Multiplanar Distraction Osteogenesis of Fibula Free Flaps Used for Secondary Reconstruction of Traumatic Maxillary Defects

Traumatic maxillary bone loss, if not treated acutely, is accompanied by contracture of the overlying soft tissue envelope and loss of facial projection in three dimensions. Reconstruction aimed at replacing the bony architecture, expanding the soft tissue envelope and establishing a platform for dental rehabilitation can be accomplished in a staged approach. We present two patients who underwent replacement of missing maxillary segments with a free fibula flap, followed by distraction of the free fibula in three dimensions and eventual dental rehabilitation with osseo-integrated implants.

Patterns of craniofacial integration in extantHomo,Pan, andGorilla

Brain size increased greatly during Pleistocene human evolution, while overall facial and dentognathic size decreased markedly. This mosaic pattern is due to either selective forces that acted uniquely on each functional unit in a modularized, developmentally uncoupled craniofacial complex, or alternatively, selection that acted primarily on one unit, with the other responding passively as part of a coevolved set of ontogenetically and evolutionarily integrated structures. Using conditional independence modeling on homologous linear measurements of the height, breadth, and depth of the cranium in Pan (n = 95), Gorilla (n = 102), and recent Homo (n = 120), we reject the null hypothesis of equal levels of overall cranial integration. While all three groups share the pattern of greater neurocranial integration with distinct separation between the face and neurocranium (modularization), family differences do exist. The apes are more integrated in their entire crania, but display a particularly strong pattern of integration within the facial complex related to prognathism. Modern humans display virtually no facial integration, a pattern which is likely related to their markedly decreased facial projection. Modern humans also differ from their great ape counterparts in being more integrated within the breadth dimension of the cranial vault, likely tied to the increase in brain size and eventual globularity seen in human evolution. That the modern human integration pattern differs from the ancestral African great ape pattern along the inverse neurocranial-facial trend seen in human evolution indicates that this shift in the pattern of integration is evolutionarily significant, and may help to clarify aspects of the current debate over defining modern humans.

Facial reshaping using less invasive methods

There has been no ideal option for patients who are unhappy with their facial shape but do not want to undergo complex surgeries or pay the high price of temporary injectable treatments. In this article, we describe the treatment of facial complaints such as the gaunt face, long face, bottom-heavy face, chubby face, midface retrusion, and asymmetric face, as well as the modification of racial and ethnic characteristics, through the use of less invasive methods. Fat grafting was used to accentuate the cheekbones in most patients complaining about their facial shape. For the long face, this technique increased the horizontal facial diameter. Lipoplasty combined with buccal lipectomy effectively decreased the fullness of the lower face and improved facial contour in the bottom-heavy face and chubby face. A skin-tightening face lift may also be necessary in patients with neck laxity. Fat grafting was used to fill in depressions or defects in the gaunt face and to treat midface retrusion and facial asymmetry. Added facial projection was obtained with nasal and chin implants. Photographs of representative patients treated for facial reshaping using the described techniques are presented. By using the less invasive techniques described, plastic surgeons can reshape a patient's face without the prolonged downtime or morbidities associated with more invasive procedures.

Cortical control for mastication in cats: Changes in masticatory movements following lesions in the masticatory cortex

In a previous paper (Hiraba and Sato ) we reported that an accurate mastication might be executed by the cortical processing in bilateral masticatory area (MA)and motor cortices. The aim of this study was to determine if cats with lesion of either unilateral or bilateral MA showed changes in mastication. After exploring mechanoreceptive fields and motor effects of mastication-related neurons (MRNs) in MA using the single unit recording and intracortical microstimulation methods, we made various lesions in MAs with injections of kainic acid (0.1%, 2.0 µl). Since the MA was divided into facial (F) and intraoral (I) projection areas as reported in the previous paper, cats with the unilateral lesion in F or I, and with the bilateral lesion in F & F, I & I or F & I (F on one side and I on other side) were prepared. Cats with unilateral lesion in F or I and with bilateral lesion in F & I showed no changes in mastication except for prolongation of the food intake and masticatory periods. Cats with bilateral lesion into F & F, or I & I showed wider jaw-opening during mastication. Particularly, the latter group showed enormous jaw-opening, delay in the start of mastication and difficulty in manipulating food on the tongue. In all cats with lesions of each type, masticatory and swallowing rhythms remained normal. These findings suggest that accurate mastication is executed by the close integration between F & F and I & I of the bilateral MA.

Ossification and midline shape changes of the human fetal cranial base.

An appreciation of ontogenetic changes to the cranial base is important for understanding the evolution of modern human skull form. Using geometric morphometric techniques, this study explores midline shape variations of the basicranium and midface during human prenatal ontogeny. In particular, the analysis sets out to explore shape variations associated with endochondral ossification and to reassess shape variations previously observed on the basis of angular measures.Fifty-four formalin-preserved human fetuses were imaged using high-resolution MRI. Coordinates for 10 landmarks defining the midline basicranium and midface were acquired and areas of ossification in the midline basioccipital, basisphenoid, and presphenoid cartilages were measured as percentages of overall cranial base area. The results show shape variations with increasing fetal size that are consistent with cranial base retroflexion, anterior facial projection and dorsal facial rotation. These growth variations are centered on the midsphenoid area and are associated with disproportionate variations of sphenoid height and length. Small but significant correlations were observed between ossification of the presphenoid cartilage and components of shape that described, among other variations, sphenoid shortening. While ossification cannot be directly linked with the shape variations observed, it seems likely that bone formation plays a role in modulating the influence of other factors on the fetal cranial base.

Revisional surgery for midface fractures: Malocclusion and malposition

Secondary deformities that result from midface fractures are seen even after proper care is delivered by the best physicians. Malpositioned or missing skeletal fragments provide a faulty foundation and disrupt the harmony of the overlying soft tissues. Weak bony support will lead to its collapse and cicatrical loss of soft-tissue volume, thereby compounding the challenge. Successful management hinges on the surgeon's ability to distill the disfigurement to its individual components. Symmetry is key to proper reconstruction in general and particularly, in the face. In addition, proper facial projection and height must be reestablished. Systematic evaluation of the midface, including position of the globes, orbits, zygomatic (facial) width, and occlusion, is paramount. Our basic approach to the evaluation of these deformities and particularly useful techniques for their correction are presented, along with a representative case

Sphenoid shortening and the evolution of modern human cranial shape.

Crania of 'anatomically modern' Homo sapiens from the Holocene and Upper Pleistocene epochs differ from those of other Homo taxa, including Neanderthals, by only a few features. These include a globular braincase, a vertical forehead, a dimunitive browridge, a canine fossa and a pronounced chin. Humans are also unique among mammals in lacking facial projection: the face of the adult H. sapiens lies almost entirely beneath the anterior cranial fossa, whereas the face in all other adult mammals, including Neanderthals, projects to some extent in front of the braincase. Here I use radiographs and computed tomography to show that many of these unique human features stem partly from a single, ontogenetically early reduction in the length of the sphenoid, the central bone of the cranial base from which the face grows forward. Sphenoid reduction, through its effects on facial projection and cranial shape, may account for the apparently rapid evolution of modern human cranial form, and suggests that Neanderthals and other archaic Homo should be excluded from H. sapiens.