Search

Temporal tendinitis is characterized by acute inflammation often resulting from mechanical stress, such as repetitive jaw movements associated with jaw opening and closing and teeth clenching. Treatment for temporal tendinitis typically involves the administration of local anesthetic or corticosteroid injections. However, the complex anatomical structure of the coronoid process, to which the temporalis tendon attaches, located deep within the zygomatic arch, poses challenges for accurate injections. In this study, we aimed to establish guidelines for the safe and effective treatment of temporal tendinitis by using intraoral ultrasonography (US) to identify the anatomical structures surrounding the temporalis tendon and coronoid process. US was performed using an intraoral transducer on 58 volunteers without temporomandibular joint disease. The procedure involved placing the transducer below the occlusal plane of the maxillary second molar. Measurements were taken for the horizontal distance from the anterior border of the coronoid process, observed at the midpoint (MP) of the US images, and the depth of the coronoid process and temporalis muscle from the oral mucosa. The anterior border of the coronoid process was visualized on all US images and classified into three observed patterns at the MP: type A (anterior to the MP, 56.2%), type B (at the MP, 16.1%), and type C (posterior to the MP, 27.7%). The temporalis muscle was located at a mean depth of 3.12 ± 0.68 mm from the oral mucosa. The maxillary second molar is an intraoral landmark for visualizing the anterior border of the coronoid process. The new location information obtained using intraoral US could help identify the safest and most effective injection sites for the treatment of temporal tendinitis., (© 2023 American Association of Clinical Anatomists and British Association of Clinical Anatomists.)

Skeletal muscle fibre architecture provides important insights into performance of vertebrate locomotor and feeding behaviours. Chemical digestion and in situ sectioning of muscle bellies along their lengths to expose fibres, fibre orientation and intramuscular tendon, are two classical methods for estimating architectural variables such as fibre length (L f ) and physiological cross-sectional area (PCSA). It has recently been proposed that L f estimates are systematically shorter and hence less accurate using in situ sectioning. Here we addressed this hypothesis by comparing L f estimates between the two methods for the superficial masseter and temporalis muscles in a sample of strepsirrhine and platyrrhine primates. Means or single-specimen L f estimates using chemical digestion were greater in 17/32 comparisons (53.13%), indicating the probability of achieving longer fibres using chemical digestion is no greater than chance in these taxonomic samples. We further explored the impact of sampling on scaling of L f and PCSA in platyrrhines applying a bootstrapping approach. We found that sampling-both numbers of individuals within species and representation of species across the clade significantly influence scaling results of L f and PCSA in platyrrhines. We show that intraspecific and clade sampling strategies can account for differences between previously published platyrrhine scaling studies. We suggest that differences in these two methodological approaches to assessing muscle architecture are relatively less consequential when estimating L f and PCSA for comparative studies, whereas achieving more reliable estimates within species through larger samples and representation of the full clade space are important considerations in comparative studies of fibre architecture and scaling., (© 2024 American Association for Anatomy.)

Background: With the growing popularity of rejuvenation, people are giving more concerns on their temporal depression which makes them look older and wishing to improve it by injection. The complex structure of the temporal region leads to a higher risk of failed injection. The temporal region is well understood based on cadaver anatomy, but few studies have described its spatial structure. The purpose of this study was to improve the efficacy and safety of temporal injection by studying the spatial structure of the soft tissues and major blood vessels in each layer of the temporal region., Methods: A total of 30 volunteers (24 men and 6 women, 60 temporal regions) were investigated. Color Doppler ultrasound was used to measure the thickness of the temporal layers at the selected measurement points (A, B, C, D, E, and F). The maximum thickness of the temporal fat pads was also measured, and the layers, depths and diameters of the major temporal vessels (frontal branch of superficial temporal artery and vein, middle temporal vein and deep temporal artery) were measured., Results: At the various measurement points, the thickness and position of the skin, subcutaneous fat superficial fascia, and temporalis muscle did not differ significantly, whereas the superficial temporal fat pad and deep temporal fat pad differed significantly. The diameter and depth of the superficial temporal artery, superficial temporal vein, and deep temporal artery did not differ significantly, whereas the diameter of the middle temporal vein differed slightly, whereas the depth differed more obviously., Conclusions: The temporal structure is very complex, and understanding the spatial position of each layer of tissue plays an important role in improving the efficacy and safety of temporal filler injection. Ultrasound can help us to understand this information and assist in therapy., Level of Evidence: Level II., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 by Mutaz B. Habal, MD.)

A report published in the Annals of Anatomy recently stated that the coronoid part of the masseter was a newly described layer. However, there have been numerous discussions regarding the layered structures in the masseter and temporalis. In this review, we show that the muscle bundle stated as a newly described layer could be similar to the zygomaticomandibularis that was previously reported. Knowledge of various muscle bundles with different fiber directions is essential to understanding the stabilization and closing functions of the jaw. Therefore, the layered structure of the masseter and temporalis should be considered more for clinical and functional applications., Competing Interests: Declaration of Competing Interest The authors have no conflict of interest to disclose., (Copyright © 2022 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

Background: The temporal muscle (TM) needs to be dissected and reflected downward in some anterolateral cranial approaches, and failing to preserve its integrity could have severe functional and cosmetic consequences. Most articles focus on techniques to prevent vascular injury during retrograde dissection or techniques to preserve the facial nerve; however, information on how to take care of the muscle during hook retraction is limited. We presented an anatomic study of vascularization of the TM, and we established safe areas for muscular hook retraction., Methods: We dissected 16 TMs in 8 cadaveric heads. The TM was reflected downward, and we measured the distance between the anterior branch of the posterior deep temporal artery (PDTA) and the frontozygomatic suture and the distance between the posterior branch of the PDTA and the external auditory meatus projection., Results: The average distance between the anterior branch of the PDTA and the frontozygomatic suture was 19.5 mm (range, 14-26 mm). The average distance between the posterior branch of the PDTA and the external auditory canal was 37.1 mm (range, 31-43 mm). We established 2 safe zones for hook placement: an anterior safe zone 14 mm posterior to the frontozygomatic suture and a posterior safe zone 30 mm anterior to the external auditory meatus., Conclusions: We delimited 2 safe zones for hook placement during TM retraction aiming to avoid direct vascular damage in anterolateral cranial approaches., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: The deep temporal fascia (DTF) is known to separate into two layers that descend to attach to the zygomatic arch. When surgeons reduce an isolated fracture of the zygomatic arch through a temporal approach, the temporal incision site needs to be superior to the split line of the DTF., Materials and Methods: Sixty-seven hemifacial cadavers were investigated after removing the skin, subcutaneous tissue, and superficial temporal fascia. The superficial layer of the DTF was exposed. We cut the superficial layer along the line along, which it adhered to the deep layer inseparably. The heights of the split line of the DTF from the superior border of the zygomatic arch and from the top of the helix were measured at three points: at the jugale, zygion, and 3 cm from the tragus., Results: In all cases there were thick identifiable deep layers of the DTF. The mean heights of the split line of the DTF from the superior border of the zygomatic arch were 49.8, 46.7, and 42.6 mm at the jugale, zygion, and 3 cm from the tragus, respectively; the corresponding mean heights of the split line from the top of the helix were 19.1, 15.6, and 11.4 mm., Conclusions: Knowledge of the mean height of the split line of the DTF will be helpful for surgeons to determine the temporal incision site for ensuring the safe reduction of a zygomatic arch fracture., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest concerning the materials or methods used in this study and no source of funding., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Jaw-muscle architecture is a key determinant of jaw movements and bite force. While static length-force and force-velocity relationships are well documented in mammals, architecture dynamics of the chewing muscles and their impact on muscle performance are largely unknown. We provide novel data on how fiber architecture of the superficial anterior temporalis (SAT) varies dynamically during naturalistic feeding in tufted capuchins (Sapajus apella). We collected data on architecture dynamics (changes in muscle shape or the architectural gear ratio) during the gape cycle while subjects fed on foods of different mechanical properties. Architecture of the SAT varied with phases of the gape cycle, but gape distance accounted for the majority of dynamic changes in architecture. In addition, lower gear ratios (low muscle velocity relative to fascicle velocity) were observed when animals chewed on more mechanically resistant foods. At lower gear ratios, fibers rotated less during shortening resulting in smaller pinnation angles, a configuration that favors increased force production. Our results suggest that architectural dynamics may influence jaw-muscle performance by enabling the production of higher bite forces during the occlusal phase of the gape cycle and while processing mechanically challenging foods.

Bite force is a measure of feeding performance used to elucidate links between animal morphology, ecology, and fitness. Obtaining live individuals for in vivo bite-force measurements or freshly deceased specimens for bite force modeling is challenging for many species. Thomason's dry skull method for mammals relies solely on osteological specimens and, therefore, presents an advantageous approach that enables researchers to estimate and compare bite forces across extant and even extinct species. However, how accurately the dry skull method estimates physiological cross-sectional area (PCSA) of the jaw adductor muscles and theoretical bite force has rarely been tested. Here, we use an ontogenetic series of southern sea otters (Enhydra lutris nereis) to test the hypothesis that skeletomuscular traits estimated from the dry skull method accurately predicts test traits derived from dissection-based biomechanical modeling. Although variables from these two methods exhibited strong positive relationships across ontogeny, we found that the dry skull method overestimates PCSA of the masseter and underestimates PCSA of the temporalis. Jaw adductor in-levers for both jaw muscles and overall bite force are overestimated. Surprisingly, we reveal that sexual dimorphism in craniomandibular shape affects temporalis PCSA estimations; the dry skull method predicted female temporalis PCSA well but underestimates male temporalis PCSA across ontogeny. These results highlight the importance of accounting for sexual dimorphism and other intraspecific variation when using the dry skull method. Together, we found the dry skull method provides an underestimation of bite force over ontogeny and that the underlying anatomical components driving bite force may be misrepresented., (© 2019 Wiley Periodicals, Inc.)

Notoungulates were a diverse group of South American ungulates that included the rodent-like typotherians. However, they are typically compared with other ungulates and interpreted as grazers. Here we present the first detailed reconstruction of the masticatory muscles of the pachyrukhine typotherians Paedotherium and Tremacyllus . An outstanding feature is the presence of a true sciuromorph condition, defined by an anterior portion of the deep masseter muscle originating from a wide zygomatic plate that reaches the rostrum, a trait traceable since the Oligocene pachyrukhines. Consequently, pachyrukhines are the first case of sciuromorph non-rodent mammals. This morphology would have allowed them to explore ecological niches unavailable for the exclusively hystricomorph coexisting rodents. This innovative acquisition seems to be synchronous in Pachyrukhinae and sciuromorph rodents and related to hard-food consumption. We postulate the expansion of nut and cone trees during the major environmental changes at Eocene-Oligocene transition as a potential trigger for this convergence., Competing Interests: Competing interestsThe authors declare no competing interests.

Ligation of the sphenopalatine and posterior nasal arteries is indicated for posterior epistaxis as initial treatment or when conservative measures fail. In some patients, a transnasal approach or its alternative transantral approach are not possible due to tumor filling the nasal corridor, pterygopalatine fossa, or maxillary sinus. Aim of this study was to evaluate feasibility of endoscopically assisted transoral approach for the ligation of the maxillary artery (MA). Six fresh cadaver specimens (12 sides), previously prepared with intravascular injections of colored latex, were dissected. A combined transnasal and transoral approach exposed the MA from the deep belly of the temporalis muscle laterally to its terminal branches medially. Anatomical relationships of the MA with the deep belly of the temporalis muscle and the lower head of the lateral pterygoid muscle, and feasibility of access to the MA via a transoral approach were assessed. In all specimens, the MA was found at the point where horizontal fibers of the lower head of the lateral pterygoid muscle cross the vertical fibers of the deep belly of the temporalis muscle. In 5 specimens, the artery ran anteriorly and laterally to lower head of the lateral pterygoid muscle, and in 1 specimen, it ran posteriorly and medially to this muscle, diving between its fibers. The modified endoscopically assisted transoral approach is feasible to ligate the MA. It can be used for proximal vascular control in cases when transnasal and transantral approaches are not viable.

Objectives: Changes to soft- and hard-tissue components of the masticatory complex during development can impact functional performance by altering muscle excursion potential, maximum muscle forces, and the efficiency of force transfer to specific bitepoints. Within Macaca fascicularis, older individuals exploit larger, more mechanically resistant food items and more frequently utilize wide-gape jaw postures. We therefore predict that key architectural and biomechanical variables will scale during ontogeny to maximize bite force and gape potential within older, larger-bodied individuals., Materials and Methods: We analyzed 26 specimens of M. fascicularis, representing a full developmental spectrum. The temporalis, superficial masseter, and deep masseter were dissected to determine muscle mass, fiber length, and physiologic cross-sectional area (PCSA). Lever-arm lengths were also measured for each muscle, alongside the height of the temporomandibular joint (TMJ) and basicranial length. These variables were scaled against two biomechanical variables (jaw length and condyle-molar length) to determine relative developmental changes within these parameters., Results: During ontogeny, muscle mass, fiber length, and PCSA scaled with positive allometry relative to jaw length and condyle-molar length within all muscles. TMJ height also scaled with positive allometry, while muscle lever arms scaled with isometry relative to jaw length and with positive allometry (temporalis) or isometry (superficial and deep masseter) relative to condyle-molar length., Conclusion: Larger individuals demonstrate adaptations during development towards maximizing gape potential and bite force potential at both an anterior and posterior bitepoint. These data provide anatomical evidence to support field observations of dietary and behavioral differences between juvenile and adult M. fascicularis., (© 2018 Wiley Periodicals, Inc.)

Murine rodents display a unique cranial morphology and masticatory musculature. Yet detailed myological descriptions are scarce, especially considering the great diversity of the subfamily and the use of the house mouse and brown rat as model organisms. The masticatory musculature in these two species has been thoroughly described, which allows comparisons with other wild species. Description and comparison of a wide range of species constitutes a necessary step to fully understand how ecological factors may influence the morphology and myology of the skull in the Murinae and vice versa. In this study, we describe the masticatory musculature of five mouse species: Mus caroli, Mus cervicolor, Mus pahari, Mus fragilicauda, and Mus minutoides. For each species, one to five specimens were dissected, and their muscle weights and volumes calculated. One specimen was selected for iodine-enhanced CT-scanning, which allowed us to digitally reconstruct the musculature. We then compared the different masticatory arrangements between these species, as well as with the previous descriptions of the house mouse and brown rat. We show that interspecific differences especially involved the temporalis muscle and zygomatico-mandibularis muscular groups, although some differences were also seen in the pterygoid muscle and masseter muscle groups. We then propose some ecological interpretations for these differences, by interpreting them in terms of functional differences., (© 2018 Wiley Periodicals, Inc.)

Purpose: It has been widely accepted that a split of the deep temporal fascia occurs approximately 2 to 3 cm above the zygomatic arch and extends into the superficial and deep layers. The deep layer of the deep temporal fascia is between the superficial temporal fat pad and the temporal muscle. However, during procedures, the authors noted the absence of the deep layer of the deep temporal fascia between the superficial temporal fat pad and the temporal muscle. This prospective study was conducted to clarify the presence or absence of a deep layer of the deep temporal fascia., Materials and Methods: Anatomic layers of the soft tissues of the temporal region, with reference to the deep temporal fascia, were investigated in 130 cases operated on for zygomaticofacial fractures using the supratemporal approach from June 2013 to June 2017., Results: Of 130 surgeries, the authors found the absence of a thick, obviously identifiable, fascial layer between the superficial temporal fat pad and the temporal muscle. In fact, the authors found nothing above the temporal muscle in most cases. In a few cases, the authors observed only a small amount of scattered loose connective tissue between the superficial temporal fat pad and the temporal muscle., Conclusions: This clinical study showed the absence of a thick, obviously identifiable, fascial layer between the superficial temporal fat pad and the temporal muscle, which suggests that a "deep layer of the deep temporal fascia" might not exist., (Copyright © 2018 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Analyses of masticatory muscle architecture-specifically fascicle length (FL; a correlate of muscle stretch and contraction speed) and physiological cross-sectional area (PCSA; a correlate of force)-reveal soft-tissue dietary adaptations. For instance, consumers of large, soft foods are expected to have relatively long FL, while consumers of obdurate foods are expected to have relatively high PCSA. Unfortunately, only a few studies have analyzed these variables across large primate samples-an order of particular interest because it is our own. Previous studies found that, in strepsirrhines, force variables (PCSA and muscle masses; MM) scale with isometry or slight positive allometry, while the body size corrected FL residuals correlate with food sizes. However, a study of platyrrhines using different methods (in which the authors physically cut muscles between fascicles) found very different trends: negative allometry for both the stretch and force variables. Here, we apply the methods used in the strepsirrhine study (chemical dissection of fascicles to ensure full length measurements) to reevaluate these trends in platyrrhines and extend this research to include catarrhines. Our results conform to the previous strepsirrhine trends: there is no evidence of negative allometry in platyrrhines. Rather, in primates broadly and catarrhines specifically, MM and PCSA scale with isometry or positive allometry. When examining size-adjusted variables, it is clear that fascicle lengths (especially those of the temporalis muscle) correlate with diet: species that consume soft, larger, foods have longer masticatory fiber lengths which would allow them to open their jaws to wider gape angles. Anat Rec, 301:311-324, 2018. © 2018 Wiley Periodicals, Inc., (© 2018 Wiley Periodicals, Inc.)

The aim of this study was to clarify the anatomical relationship between the buccinator and the temporalis in order to improve understanding of the precise and coordinated movements of the mouth and the mandible. The buccinator and the temporalis were investigated in 72 hemifaces from Korean cadavers. Removing the buccal fat pad from the buccinator revealed that the fascia encircled the space between the superficial and deep tendons of the temporalis laterally, and the external surface of the buccinator medially in all specimens (100%). The fascia was located between the buccinator and the tendons of the temporalis, thereby connecting these two muscles. The fascial space was filled with connective tissue, and the buccal nerve and artery passed through this space. The inferior fibers of the buccinator arose from the anterior portion of the deep tendon of the temporalis in all specimens (100%). The anterior portion of the deep tendon of the temporalis extended forward obliquely between the ramus and body of the mandible. Thus, both the anterior portion of the deep tendon of the temporalis and its attaching inferior muscle fibers of the buccinator coursed obliquely. The above observations indicate that the connecting fascia between the buccinator and tendons of the temporalis and the inferior fibers of the buccinator that were attached to the deep tendon of the temporalis could assist in coordinatation of the movements of the mandibular region and the mouth angle in the timing and strength of contraction of the muscles during mastication, facial expression, and speech., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

Background: The pterional approach (PA), together with its variants, is still one of the most common methods used by surgeons to reach the anterior and middle cranial base. A highly important technical detail during a PA is the preservation of the frontotemporal branch of the facial nerve, which can be achieved through an interfascial dissection., Objective: To describe the anatomy of the interfascial vein (IFV), highlighting its recognition as a significant anatomic reference to perform an interfascial dissection (IFD)., Methods: Eight adult cadaveric heads, fixed with formaldehyde and injected with colored silicone, were studied. In 6 heads, an IFD was performed, simulating a PA. In the 2 remaining heads, the IFV was dissected. In addition, an IFD was performed in 10 patients, studying the IFV anatomy., Results: In the 6 cadaveric heads in which the PA with an IFD was performed, and in the 10 patients who underwent a PA with an IFD, the IFV was found. If the interfascial space is divided into thirds, in all cases, the IFV was located within the middle third of the interfascial fat pad. On the 2 cadaveric heads in which the IFV was anatomically dissected, the IFV was also located within the middle third of the interfascial space., Conclusion: Recognizing the IFV in the interfascial space is of great help as an anatomic landmark to confirm that one is actually between both layers of the superficial temporal fascia., (Copyright © 2017 by the Congress of Neurological Surgeons)

Background: Temporal hollowing is a common complication following surgical dissection in the temporal region. Our objectives were to: (1) review and clarify the temporal soft tissue relationships - supplemented by cadaveric dissection - to better understand surgical approach variations and elucidate potential etiologies of postoperative hollowing; (2) identify if there is any evidence to support a surgical approach that prevents hollowing through a systematic review., Methods: Cadaveric dissection was performed on six hemi-heads. A systematic review of the literature was undertaken to identify surgical approaches with a decreased risk of postoperative hollowing., Results: A total of 1212 articles were reviewed; 19 of these met final inclusion criteria. Level I and II evidence supports against the use of a dissection plane beneath the superficial layer of the deep temporal fascia or through the intermediate temporal fat pad. Level II evidence supports preservation of the temporalis muscle origin - no evidence is available to support other temporalis resuspension techniques. For intracranial exposure, refraining from temporal fat pad dissection (Level I Evidence) and use of decreased access approaches such as the minipterional craniotomy (Level I Evidence) appear to minimize temporal soft tissue atrophy., Conclusions: This study highlights the significance of preservation of the temporal soft tissue components to prevent hollowing. Preserving the temporalis origin and avoiding dissection between the leaflets of the deep temporal fascia or through the intermediate temporal fat pad appear to minimize this complication., (Copyright © 2016 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.)

Purpose: The objective of this study was to simplify the anatomically safe and reproducible approach for BoNT injection and to generate a detailed topographic map of the important anatomical structures of the temporal region by dividing the temporalis into nine equally sized compartments., Methods: Nineteen sides of temporalis muscle were used. The topographies of the superficial temporal artery, middle temporal vein, temporalis tendon, and the temporalis muscle were evaluated. Also evaluated was the postural relations among the foregoing anatomical structures in the temporalis muscle, pivoted upon a total of nine compartments., Results: The temporalis above the zygomatic arch exhibited an oblique quadrangular shape with rounded upper right and left corners. The distance between the anterior and posterior margins of the temporalis muscle was equal to the width of the temporalis rectangle, and the distance between the reference line and the superior temporalis margin was equal to its height. The mean ratio of width to height was 5:4., Conclusions: We recommend compartments Am, Mu, and Pm (coordinates of the rectangular outline) as areas in the temporal region for BoNT injection, because using these sites will avoid large blood vessels and tendons, thus improving the safety and reproducibility of the injection.

Purpose: The objective of this study was to characterize and compare the morphological characteristics of the dura mater, the pericranium, and the temporal fascia to ascertain the most adequate tissue to use as a dura graft., Methods: 20 dura mater, 20 pericranium and 20 temporalis fascia samples were analyzed. Each of the samples was stained with hematoxylin and eosin, orcein, Van Gieson, Masson's trichrome and Verhoeff-Van Gieson (600 slides in total) for a general morphological evaluation, as well as a quantitative, morphometric and densitometric analysis of elastic fibers present in each of the tissues., Results: The micro-densitometric analysis of the tissues indicated that the area occupied by the elastic fibers showed values of 1.766 ± 1.376, 4.580 ± 3.041, and 8.253 ± 4.467 % for the dura mater, the temporalis fascia and the pericranium, respectively (p < 0.05, all pairs). The values observed in the analysis of the density intensity were 3.42E+06 ± 2.57E+06, 1.41E+07 ± 1.28E+07, and 1.63E+07 ± 9.19E+06 for the dura mater, the temporalis fascia and the pericranium, respectively (p < 0.05), dura mater vs. temporalis fascia and dura mater vs. pericranium)., Conclusions: This is the first study to compare the dura mater with tissues for dural autograft and to quantify the elastic component present in these tissues. The results indicate that the temporalis fascia is a better dural graft because of its intrinsic tissue properties.

This study involved an extensive analysis of published research on the morphology of the temporalis muscle in order to provide an anatomical guideline on how to distinguish the temporalis muscle and temporalis tendon by observing the surface of the patient's face. Twenty-one hemifaces of cadavers were used in this study. The temporalis muscles were dissected clearly for morphological analysis between the temporalis muscle and tendon. The posterior border of the temporalis tendon was classified into three types: in Type I the posterior border of the temporalis tendon is located in front of reference line L2 (4.8%, 1/21), in Type II it is located between reference lines L2 and L3 (85.7%, 18/21), and in Type III it is located between reference lines L3 and L4 (9.5%, 2/21). The vertical distances between the horizontal line passing through the jugale (LH) and the temporalis tendon along each of reference lines L0, L1, L2, L3, and L4 were 29.7 ± 6.8 mm, 45.0 ± 8.8 mm, 37.7 ± 11.1 mm, 42.5 ± 7.5 mm, and 32.1 ± 0.4 mm, respectively. BoNT-A should be injected into the temporalis muscle at least 45 mm vertically above the zygomatic arch. This will ensure that the muscle region is targeted and so produce the greatest clinical effect with the minimum concentration of BoNT-A., Competing Interests: The authors declare no conflict of interest.

Objectives: To measure the lengths of the force and resistance arms, in order to calculate the mechanical advantage and muscular work of the human temporalis muscle (TM) in brachyfacial (BR) and dolichofacial (DO) subjects., Setting and Sample Population: Mandibles from 49 subjects of both genders (BR n = 9; DO n = 40) from the collection of the Laboratory of Human Anatomy at Universidade de Santa Cruz do Sul, Rio Grande do Sul, Brazil, were analyzed., Material and Methods: The distance between the condylar process and the coronoid process (insertion site of the TM) represented the length of the force arm (LFA ) of the TM. The distance between the condylar process and the mental protuberance represented the length of the resistance arm (LRA ). Thus, the mechanical advantage of the TM was obtained using the following ratio: LFA /LRA , while the muscular work (LRA /LFA ) of the TM was obtained using the inverse of this ratio., Results: When compared with the DO, the parameters of the BR are significantly greater, as shown by the LFA (6.0%) and mechanical advantage (8.2%; p = 0.0078). By contrast, our results show that in the DO, the LRA was 2.4% longer and the muscular work was 10.4% greater (p = 0.0087)., Conclusion: The mechanical advantage of the TM in BR subjects is significantly greater than in DO subjects. Moreover, this greater mechanical advantage may explain, at least in part, the higher incidence of temporomandibular dysfunctions in BR subjects., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Purpose: To analyze possible correlations between the electrical activity of masseter and temporal muscles, Bite Force (BF), and Morphological Facial Indices (MFI)., Methods: The study involved 43 young adults, both genders, 18 to 37 years old. The individuals were submitted to: face measurement to calculate MFI; Masseter and Temporal Surface Electromyography (sEMG) and BF measurements on right and left premolars and incisors. The following electromyographic tests were conducted: at rest position; Maximal Voluntary Isometrical Contraction (MVIC) and usual chewing of raisins. Statistical analysis was conducted using the coefficient of Spearman correlation with significance level of 5%., Results: The values at rest in the temporal muscles were significantly higher than those in the masseter muscles. A meaningful correlation was found between MFI and sEMG in the MVIC test for the Left Temporal (rs=36, p=0.017). A significant correlation was observed between FMI and sEMG during BF in incisors for temporal muscles and the Right Masseter. During the force tests, it was possible to observe a meaningful correlation between BF in right premolars and the sEMG of the Left Temporal and Masseters., Conclusion: No correlation was found between the sEMG of temporal and masseter muscles, BF, and FMI in adult individuals based on the tests performed. The SEMG of temporal and masseter muscles seems to be associated only with BF. As a datum of habitual postural characteristic, the electrical activity of temporal muscles is higher than the activity of masseters, also regardless of MFI.

Objective: To determine the safe space for hyaluronic acid(HA) injection through anatomy study of temporal layers., Methods: 6 fresh and 8 formaldehyde-fixed cadaver heads were dissected. The skin soft-tissue layers of temporal region were incised through the cranial coronal plane and elevated layer by layer. The morphological features of layers were observed and documented, as well as the relationship of the superficial temporal artery (STA),the temporal branch of facial nerve (TFN) and the middle temporal vein(MTV) with corresponding layers. Relevant neasurements of the superficial temporal fat pad (sTFD) were recorded. With reference of cardever dissection, temporal region injection with HA was carried out clinically to confirm the safety and effect., Results: In the temporal region, from surface to the temporal fossa, the layers are skin, subcutaneous tissue, superfiacial temporal fascia (STF),loose areolar tissue, superficial layer of deep temporal fascia(sDTF), sTFD, deep layer of deep temporal fascia (dDTF),deep temporal fat pad (dTFD) and temporalis. The temporal skin is tightly attached with the subcutaneous tissue. The STA runs within the subcutaneous tissue on the STF, whereas the TFN within the areolar tissue was just beneath the STF. The loose areolar tissue is a potential layer space. The DTF splits into two sheets of fascia at the line 1 cm above the upper orbital rim to envelope the sTFD, within which the MTV runs backward. The dTFD is the temporal extension of buccal fat pad. With reference of cadever dissection, the target space of temporal HA injection was beneath the temporalis for the area superior to the MTV, whereas within the sTFD for the area inferior to the MTV.67 cases were completed with good result and no complication., Conclusions: In the upper area of temporal region adjacent to the frontal border, the sub-temporalis space is the safety space for HA injection, while inferior to the middle temporal vein and near the zygoma, the superficial temporal fat pad is the target space for safe HA injection.

Purpose: The aim of this study was to evaluate anatomically the relationship between bone and muscles by detailed observation of the bone shape and the structure of muscles to facilitate an understanding of the function of the muscles involved in jaw movement., Methods: 36 specimens of 24 Japanese cadavers were examined. The insertion areas were marked using a radiopaque marker and examined by micro-computed tomography. For morphological observation, we used 101 condylar processes. In addition, we made histological sections in some specimens to observe the detailed attachments of the muscle., Results: Based on the micro-CT images and dissection findings, the lateral pterygoid muscle was found to be most frequently inserted into the anterior impression and attached to the medial impression of the process. According to the histological observations, the lateral pterygoid muscle mainly inserted to the condylar process. The micro-CT images indicated that the obvious bony ridge was lateral to the pterygoid fovea on the condylar process in all specimens. The midmedial muscle bundle of the temporalis was attached to the ridge. Based on the morphological observations, the ridge was situated on the lateral area of the condylar process., Conclusions: Since dysfunction of the temporomandibular joint is likely closely related to both the lateral pterygoid muscle and also the temporalis, further studies are necessary to evaluate the function of these muscles and consider jaw movement.

Aims: To compare the feasibility and accuracy of three injection techniques for entering the superior joint space of the swine temporomandibular joint (TMJ)., Methods: Nine swine were used for this study, in which 500 μL of colored dye was injected into both TMJs of each swine. Three injection techniques were used: the posterior injection (PI), the anterosuperior injection (ASI), and the lateral injection (LI) techniques. Each injection technique was performed on six TMJs. Swine were sacrificed immediately after injection and the swine head was dissected in order to observe the dye distribution. Injection was considered successful if no dye could be observed outside the superior joint space., Results: The PI technique was successful in all six TMJs (success rate: 100%), the LI technique in three out of six TMJs (success rate: 50%), and the ASI technique in two out of six TMJs (success rate: 33%); the differences were statistically significant (chi-square test, P < .05)., Conclusion: The PI technique was more accurate than the LI or ASI techniques in accessing the swine superior TMJ space.

Background: Non-thrombotic pulmonary embolism has recently been reported as a remote complication of filler injections to correct hollowing in the temporal region. The middle temporal vein (MTV) has been identified as being highly susceptible to accidental injection., Methods: The anatomy and tributaries of the MTV were investigated in six soft embalmed cadavers. The MTV was cannulated and injected in both anterograde and retrograde directions in ten additional cadavers using saline and black filler, respectively., Results: The course and tributaries of the MTV were described. Regarding the infusion experiment, manual injection of saline was easily infused into the MTV toward the internal jugular vein, resulting in continuous flow of saline drainage. This revealed a direct channel from the MTV to the internal jugular vein. Assessment of a preventive maneuver during filler injections was effectively performed by pressing at the preauricular venous confluent point against the zygomatic process. Sudden retardation of saline flow from the drainage tube situated in the internal jugular vein was observed when the preauricular confluent point was compressed. Injection of black gel filler into the MTV and the tributaries through the cannulated tube directed toward the eye proved difficult., Conclusion: The mechanism of venous filler emboli in a clinical setting occurs when the MTV is accidentally cannulated. The filler emboli follow the anterograde venous blood stream to the pulmonary artery causing non-thrombotic pulmonary embolism. Pressing of the pretragal confluent point is strongly recommended during temporal injection to help prevent filler complications, but does not totally eliminate complication occurrence., No Level Assigned: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors http://www.springer.com/00266 .

Purpose: To examine the microanatomical location of hyaluronic acid gel injected within the temporal hollows of cadaver specimens., Methods: The temporal hollows were injected subcutaneously with hyaluronic acid gel in 6 fresh frozen human cadaver hemifaces. Temporal soft tissues were dissected to a preperiosteal plane and fixated in 95% alcohol. A soft tissue section extending from skin to temporal bone was obtained for each specimen. Histologic examination was performed using hematoxylin and eosin stain., Results: In 5 of 6 specimens, at least 95% of the hyaluronic acid was located within the subcutaneous fat. In 1 of 6 specimens, approximately 35% of the material was located within the subcutaneous fat and 60% was located within the superficial temporal fascia. Two specimens had 5% located within the temporalis muscle. In 1 specimen, hyaluronic acid was found to encompass a superficial muscular artery within the superficial temporal fascia., Conclusions: This study elucidates the location of hyaluronic acid gel after subcutaneous injection within the temporal hollow. Histology confirmed consistent placement of the gel within the subcutaneous tissues, but it also showed that injection in this region may produce unintended deeper location of filler, and a significant perivascular collection of the material. The proximity of dense temporal fascial and muscle arterial networks in this region may pose risk for perivascular injection and associated complications.

To carry out functional simulations of the masticatory system that aim to predict strain magnitudes it is important to apply appropriate jaw-elevator muscle forces. Force magnitude estimation from directly measured muscle physiological cross-sectional area or anatomical cross-sectional area (CSA) is not possible for fossils and skeletal material from museum collections. In these cases, muscle CSAs are often estimated from bony features. This approach has been shown to be inaccurate in a prior study based on direct measurements from cadavers. Postmortem alterations as well as age changes in muscle form might explain this discrepancy. As such, the present study uses CT images from 20 living individuals to directly measure temporalis and masseter muscle CSAs and estimated cross-sectional areas (ECSAs) from bony features. The relationships between CSAs and ECSAs were assessed by comparing mean values and by examining correlations. ECSAs are up to 100% greater than CSA and the means of these variables for each muscle differ significantly. Further, ECSA is significantly correlated with CSA for temporalis but not masseter. Cranial centroid size is only significantly associated with CSA for temporalis. These findings indicate that ECSAs should be employed with caution in simulations of human masticatory system functioning; they do not reflect CSAs and it is plausible that this also applies to studies of closely related living and fossil taxa. When ECSAs are used, sensitivity analyses are required to determine the impact of potential errors., (© 2015 Wiley Periodicals, Inc.)

Bone is a highly plastic tissue that reflects the many potential sources of variation in shape. Here, we focus on the functional aspects of bone remodeling. We choose the skull for our analyses because it is a highly integrated system that plays a fundamental role in feeding and is thus, likely under strong natural selection. Its principal mechanical components are the bones and muscles that jointly produce bite force and jaw motion. Understanding the covariations among these three components is of interest to understand the processes driving the evolution of the feeding apparatus. In this study, we quantitatively and qualitatively compare interactions between these three components in shrews from populations known to differ in shape and bite force. Bite force was measured in the field using a force transducer and skull shape was quantified using surface geometric morphometric approaches based on µCT-scans of the skulls of same individuals. The masseter, temporalis, pterygoideus, and digastricus muscles of these individuals were dissected and their cross sectional areas determined. Our results show strong correlations between bite force and muscle cross sectional areas as well as between bite force and skull shape. Moreover, bite force explains an important amount of skull shape variation. We conclude that interactions between bone shape and muscle characteristics can produce different morpho-functional patterns that may differ between populations and may provide a suitable target for selection to act upon., (© 2014 Wiley Periodicals, Inc.)

Wombats are unique among marsupials in having one pair of upper incisors, and hypsodont molars for processing tough, abrasive vegetation. Of the three extant species, the most abundant, the common wombat (Vombatus ursinus), has had the least attention in terms of masticatory muscle morphology, and has never been thoroughly described. Using MRI and digital dissection to compliment traditional gross dissections, the major jaw adductor muscles, the masseter, temporalis and pterygoids, were described. The masseter and medial pterygoid muscles are greatly enlarged compared to other marsupials. This, in combination with the distinctive form and function of the dentition, most likely facilitates processing a tough, abrasive diet. The broad, flat skull and large masticatory muscles are well suited to generate a very high bite force. MRI scans allow more detail of the muscle morphology to be observed and the technique of digital dissections greatly enhances the knowledge obtained from gross dissections.

Lengthening temporalis myoplasty, reported by Daniel Labbé in 1997, is a unique and definite facial reanimation procedure that involves moving the whole temporal muscle anteroinferiorly and inserting its tendon directly into the nasolabial fold. In the present article, we report our experience in the use of his modified method of the procedure, which preserves the zygomatic arch by transecting the coronoid process through the nasolabial fold incision. We also describe our cadaveric study that aimed to elucidate a secure approach for coronoid process transection. We performed this procedure in five patients with permanent facial paralysis. To improve facial symmetry, we also performed several additional static reconstructions such as T-shaped double-sleeve fascia grafts for lower lip deformities. We were successful in achieving considerable static improvement at rest, immediately after the surgery, and the recovery of facial movement was apparent approximately 3 months after the surgery. With regard to the cadaveric study, we noted that the entry to the buccal fat region, which is also the pathway of the temporal fascia, was a narrow space, and a short transection of the medial upper edge of the masseter fascia would make it easy to locate the coronoid process. Therefore, for a safe and secure access to the coronoid process from the nasolabial fold, we believe that we should first expose the cranial side and continue to dissect along the side and lower edge of the maxilla to locate the medial upper edge of the masseter fascia. By transecting along its edge, we could easily access the coronoid process, located immediately behind it, and widen the pathway of the temporal fascia. This modified method is less invasive and simpler compared to the original procedure, and understanding the detailed anatomy for dissection would help surgeons perform this procedure more confidently., (Copyright © 2014 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.)

Objective: To investigate the morphology change of stomatognathic muscles after zygomatic plasty combined with mandibular angel plasty., Methods: 3D-CT facial soft tissue measurement was performed pre-operative and at 10 days,3 months post-operatively in 59 cases with prominent malar-complex and mandibular angle. The q test (Newman-Keuls method) was used to analyze the variance., Results: The cross sectional area of masseter muscle and medial pterygoid muscle were both increased at 10 days, reduced at 3 months post-operatively (P < 0.05). The masseter muscle and medial pterygoid muscle cross sectional areas were (4.73 +/- 0.21) cm2 and (3.24 +/- 0.21) cm2 at anterior nasal spine plane, respectively; the pterygoid muscle cross-sectional area was (1.37 +/- 0.35 ) cm2 at the root of coronoid process plane, showing significant difference, when comparing with those before operation (P < 0.05). Lateral pterygoid muscle and temporal muscle had no statistical difference between the pre-and 10 days post-operatively(P > 0.05), however, the temporal muscle was reduced while the lateral pterygoid muscle was increased at 3 months post-operatively. The temporal muscle cross-sectional area was(2.35 + 0.25) cm2 at coronoid process plane; the temporal muscle and lateral pterygoid muscle cross-sectional areas were (1.00 +/- 0.16) cm2 and (3.54 +/- 0.61) cm2 at the root of coronoid process plane, which were significantly different from those before operation (P < 0.05 )., Conclusions: Because of osteotomy, muscles attached position are changed in the short term after zygomatic plasty combined with mandibular angel plasty. Masseter muscle and medial pterygoid muscle are inevitably injuried during the operation. With the postoperative recovery, muscles have adaptive changes which reduced compared with those before operation after their reattachment. Zygomatic plasty can cause temporal muscle atrophy;while the lateral pterygoid muscle is rarely involved, the cross sectional area had no statistical difference between the pre- and 10 days post-operative, and the cross sectional area increase at 3 months post-operatively may be due to a compensational enlargement.

Importance: During anatomic and surgical dissections, a connection was seen between the superficial layer of the deep temporal fascia and the prezygomatic area. These findings were in contrast to previous evaluations. This study defines this connection, which is important to understand from both surgical and anatomic standpoints., Objective: To define the connection between the superficial layer of the deep temporal fascia and the prezygomatic area and demonstrate the presence of a deep fascial layer in the midface., Design and Setting: Anatomical study performed at the Laboratoire d'Anatomie de la Faculté de Médecine de Nice, Sophia Antipolis, France; at the Centre du Don des Corps de l'Université Paris Descartes, Paris, France; and at the Department of Experimental Medicine, Histology, and Embryology Unit of the University of Pavia, Pavia, Italy. Twenty-four hemifaces of 14 white cadavers were dissected to define the relationship between deep temporal fascia and the midface. Four biopsy samples were harvested for histologic analysis., Main Outcomes and Measures: Dissection of 24 hemifaces from the fresh cadavers revealed the following findings. There is a connection of the deep fascia of the temple (superficial layer of deep temporal fascia) to the midface that divides the fat deep to the orbicularis muscle into 2 layers. One layer of fat is the so-called suborbicularis oculi fat (SOOF), which is superficial to the deep fascia, and the other layer of fat (preperiosteal) is deep to the deep fascia and adherent to malar bone. These findings are in contrast to previous anatomical findings. RESULTS In 12 hemifaces, the superficial layer of the deep temporal fascia directly reached the prezygomatic area as a continuous fascial layer. In 16 hemifaces, the superficial sheet of the deep temporal fascia inserted at the level of the zygomatic and lateral orbital rim and continued as a deep fascial layer over the prezygomatic area. In all specimens, a deep fascial layer was present in the prezygomatic-infraorbital area. This deep fascial layer is adherent to the muscles of the infraorbital area, and it divided the fat located deep to the orbicularis oculi muscle into 2 layers: the SOOF and a deeper layer. Histologic examination of the biopsy samples confirmed these findings., Conclusions and Relevance: This study demonstrates the existence of a deep fascial layer in the midface. This fascia is connected to the superficial layer of the deep temporal fascia, and it divides the fat deep to the orbicularis oculi muscle into 2 layers. This new finding carries interesting implications related to the classic concept of the superficial musculoaponeurotic system., Level of Evidence: NA.

Background: The psoas muscle has been shown to predict patient outcomes based on the quantification of muscle area using computed tomography (CT) scans. The accuracy of morphomic analysis on other muscles has not been clearly delineated. In this study, we determine the correlation between temporalis muscle mass, psoas muscle area, age, body mass index (BMI), and gender., Methods: Temporalis and psoas muscle dimensions were determined on all trauma patients who had both abdominal and maxillofacial CT scans at the University of Michigan between 2004 and 2011. Age, BMI, and gender were obtained through chart review. Univariate and multivariate analyses were performed to determine the relative relationship between morphomic data of the temporalis and psoas muscles and the ability of such information to correspond with clinical variables, such as BMI, age, and gender., Results: A total of 646 patients were included in the present study. Among the 249 (38.5%) women and 397 (61.5%) men, the average age was 49.2 y. Average BMI was 27.9 kg/m². Total psoas muscle area directly correlated with mean temporalis muscle thickness (r = 0.57, P < 0.001). There was an indirect correlation between age and psoas muscle area (r = -0.52, P < 0.001) and temporalis muscle thickness (r = -0.36, P < 0.001). Neither psoas nor temporalis measurements correlated strongly with BMI (r = 0.18, P < 0.001; r = 0.14, P = 0.002), although stronger correlations were found in a more "frail," subgroup as defined by a BMI of <20 (r = 0.59, P = 0.002)., Conclusions: We demonstrate that dimensions of the temporalis muscle can be quantified and may serve as a proxy for age. Going forward, we aim to assess the utility of temporalis and psoas morphomics in predicting complication rates among trauma patients admitted to the hospital to predict outcomes in the future., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Introduction: For more than a century, the temporalis muscle has been used for facial reconstructions. More recently, a split temporalis muscle flap elevated on the superficial temporal pedicle has been described, for which the resulting gain of length makes crossing of the midline possible, as well as reconstruction of substance losses exceeding the midline., Materials and Methods: Fourteen fresh cadaveric dissections were performed to study the different techniques for splitting the temporalis muscle. Dissections with catheterization and injection of radio-opaque contrasting agent in the external carotid artery were then performed to specify the vascularization of the flap split on the superficial temporal pedicle., Results: The duplication of the superficial temporal pedicle grants greater length compared to that of the deep pedicles, 57 mm versus 40 (p = 0.036). The middle temporal artery is capable of ensuring the vascularization, and therefore the viability, of the split flap. From these results, we spoke about the limitations of this study and we have inferred the main indications.

Introduction: The superior head of the lateral pterygoid muscle (LPM), is closely related to the temporomandibular joint (TMJ) and plays a role in the aetiology of temporomandibular disorders. Increased activity of this muscle has been implicated in the anterior displacement of the TMJ disc. However, there is uncertainty about the manner of the LPM attachment to the disc-condyle complex., Aim: The aim of this study was to investigate the exact anatomy of the attachment of the superior head of the LPM (SLPM) to the disc-condyle complex of the TMJ., Material and Methods: Thirty-six TMJs were examined - both sides of 18 Greek cadavers (eight males and 10 females, mean age 79.6 years). Examination of the attachment of the SLPM was undertaken viewed under the dissecting microscope., Results: Variation in the attachment of the SLPM was categorized into three types: in type I, the SLPM inserted into the condyle and the disc-capsule complex (55.5%). In type II, the SLPM only inserted into the condyle (27.8%). In type III, the SLPM inserted purely into the disc-capsule complex (16.7%)., Conclusions: This study demonstrates that there are three different attachment types of the SLPM to the disc-condyle complex. The type III variation could be involved in the TMJ pathology. The knowledge of the variations of the SLPM attachment could be useful for precise surgical and pharmaceutical approaches., (Copyright © 2012 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.)

Background: Estimates of blood loss during craniosynostosis surgeries have ranged from 42 to 126 percent of infant's total blood volume. Currently, no risk model has been developed to determine the likelihood of needing a blood transfusion. The authors propose an objective model, based on patients' three-dimensional anatomical characteristics, to stratify the likelihood of needing perioperative packed red blood cells., Methods: High-throughput image analysis from already ordered preoperative computed tomographic scans was used to reconstruct the three-dimensional anatomy of the temporalis muscle and overlying temporal fat pad. Using these morphomic measurements, the authors created a risk assessment model of the amount of packed red blood cells infused based on morphomic variations in temporal soft tissue., Results: The authors evaluated 139 infants with nonsyndromic craniosynostosis from the University of Michigan Health System. Results show the need for blood transfusion ranged from 94.1 percent among patients in the smallest quartile for temporal fat pad volume compared with 65.7 percent among the group with the largest quartile for temporal fat pad volume (p = 0.0057). Using multivariable linear regression, temporal fat pad volume (p = 0.012) and fat pad thickness (p = 0.036) were independent predictors for amount of packed red blood cells required., Conclusions: The authors demonstrate that patients with diminished temporal fat pad volume are significantly more likely to need increased packed red blood cell transfusions. In addition, by use of multivariable linear regression, their data suggest that temporal fat pad volume and thickness were independent predictors for the amount of required transfusion of packed red blood cells.

The aims of this article are twofold: (1) to provide the facial plastic surgeon with a comprehensive and up-to-date overview of periocular anatomy including the brow, midface, and temporal region and (2) to highlight important anatomical relationships that must be appreciated in order to achieve the best possible functional and aesthetic surgical outcomes., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

The most stable pattern of internal fixation for fractures of the mandibular condyle is a matter for ongoing discussion. In this study we investigated the stability of three commonly used patterns of plate fixation, and constructed finite element models of a simulated mandibular condylar fracture. The completed models were heterogeneous in the distribution of bony material properties, contained about 1.2 million elements, and incorporated simulated jaw-adducting musculature. Models were run assuming linear elasticity and isotropic material properties for bone. This model was considerably larger and more complex than previous finite element models that have been used to analyse the biomechanical behaviour of differing plating techniques. The use of two parallel 2.0 titanium miniplates gave a more stable configuration with lower mean element stresses and displacements over the use of a single miniplate. In addition, a parallel orientation of two miniplates resulted in lower stresses and displacements than did the use of two miniplates in an offset pattern. The use of two parallel titanium plates resulted in a superior biomechanical result as defined by mean element stresses and relative movement between the fractured fragments in these finite element models., (Copyright © 2012 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)

The jaw-closing muscles are responsible for generating many of the forces and movements associated with feeding. Muscle physiologic cross-sectional area (PCSA) and fiber length are two architectural parameters that heavily influence muscle function. While there have been numerous comparative studies of hominoid and hominin craniodental and mandibular morphology, little is known about hominoid jaw-muscle fiber architecture. We present novel data on masseter and temporalis internal muscle architecture for small- and large-bodied hominoids. Hominoid scaling patterns are evaluated and compared with representative New- (Cebus) and Old-World (Macaca) monkeys. Variation in hominoid jaw-muscle fiber architecture is related to both absolute size and allometry. PCSAs scale close to isometry relative to jaw length in anthropoids, but likely with positive allometry in hominoids. Thus, large-bodied apes may be capable of generating both absolutely and relatively greater muscle forces compared with smaller-bodied apes and monkeys. Compared with extant apes, modern humans exhibit a reduction in masseter PCSA relative to condyle-M1 length but retain relatively long fibers, suggesting humans may have sacrificed relative masseter muscle force during chewing without appreciably altering muscle excursion/contraction velocity. Lastly, craniometric estimates of PCSAs underestimate hominoid masseter and temporalis PCSAs by more than 50% in gorillas, and overestimate masseter PCSA by as much as 30% in humans. These findings underscore the difficulty of accurately estimating jaw-muscle fiber architecture from craniometric measures and suggest models of fossil hominin and hominoid bite forces will be improved by incorporating architectural data in estimating jaw-muscle forces., (Copyright © 2013 Wiley Periodicals, Inc.)

Objective: The purpose of this study was to determine whether high amounts of fast/type II myosin heavy chain (MyHC) in the superficial as compared to the deep temporalis muscle of adult female and male baboons (Papio anubis) correlates with published data on muscle function during chewing. Electromyographic (EMG) data show a regional specialization in activation from low to high amplitude activity during hard/tough object chewing cycles in the baboon superficial temporalis.(48,49) A positive correlation between fast/type II MyHC amount and EMG activity will support the high occlusal force hypothesis., Design: Deep anterior temporalis (DAT), superficial anterior temporalis (SAT), and superficial posterior temporalis (SPT) muscle samples were analyzed using SDS-PAGE gel electrophoresis to test the prediction that SAT and SPT will show high amounts of fast/type II MyHC compared to DAT. Serial muscle sections were incubated against NOQ7.5.4D and MY32 antibodies to determine the breadth of slow/type I versus fast/type II expression within each section., Results: Type I and type IIM MyHCs comprise nearly 100% of the MyHCs in the temporalis muscle. IIM MyHC was the overwhelmingly predominant fast MyHC, though there was a small amount of type IIA MyHC (≤5%) in DAT in two individuals. SAT and SPT exhibited a fast/type II phenotype and contained large amounts of IIM MyHC whereas DAT exhibited a type I/type II (hybrid) phenotype and contained a significantly greater proportion of MyHC-I. MyHC-I expression in DAT was sexually dimorphic as it was more abundant in females., Conclusions: The link between the distribution of IIM MyHC and high relative EMG amplitudes in SAT and SPT during hard/tough object chewing cycles is evidence of regional specialization in fibre type to generate high occlusal forces during chewing. The high proportion of MyHC-I in DAT of females may be related to a high frequency of individual fibre recruitment in comparison to males., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The supraorbital keyhole approach offers a limited access for aneurysms located at the middle cerebral artery (MCA) bifurcation with long M(1) segments or proximal M(2) aneurysms. Alternative minimally invasive routes centered on the pterion have been developed to address these aneurysms. Appropriate dissection and reconstruction of the temporal muscle are important for optimal exposure and best cosmetic results with the pterional keyhole craniotomy. The authors describe the technical nuances of temporal muscle dissection and reconstruction adapted to the pterional keyhole craniotomy. After incising the scalp in a curvilinear fashion behind the hairline, an interfascial dissection is performed, allowing anterior reflection of the superficial temporal fat pat and superficial temporal fascia. The temporal muscle is incised 7-10 mm below its insertion at the superior temporal line. The deep temporal fascia and temporal muscle are incised vertically, completing a T-shaped incision. Subperiosteal dissection of both muscle flaps preserves the deep temporal arteries and nerves. A craniotomy measuring 2.5-3 cm in diameter, based anteriorly at the pterion, is made over the sylvian fissure. Dissection of the sylvian fissure and of MCA aneurysms can proceed without the use of retractors. The bone flap and associated hardware is entirely covered by the temporal muscle, which is reconstructed in 2 layers: the temporal muscle/deep temporal fascia and the superficial temporal fascia. This dissection technique prevents damage to branches of the facial nerve and minimizes temporal muscle damage. Dividing the temporal muscle vertically and reflecting both parts anteriorly and posteriorly prevents suboptimal illumination and visualization under the microscope. Covering the bone flap and related hardware with a multilayer anatomical reconstruction optimizes cosmetic results.

The morphology and biomechanics of the vertebrate skull reflect the physical properties of diet and behaviors used in food acquisition and processing. We use phyllostomid bats, the most diverse mammalian dietary radiation, to investigate if and how changes in dietary hardness and loading behaviors during feeding shaped the evolution of skull morphology and biomechanics. When selective regimes of food hardness are modeled, we found that species consuming harder foods have evolved skull shapes that allow for more efficient bite force production. These species have shorter skulls and a greater reliance on the temporalis muscle, both of which contribute to a higher mechanical advantage at an intermediate gape angle. The evolution of cranial morphology and biomechanics also appears to be related to loading behaviors. Evolutionary changes in skull shape and the relative role of the temporalis and masseter in generating bite force are correlated with changes in the use of torsional and bending loading behaviors. Functional equivalence appears to have evolved independently among three lineages of species that feed on liquids and are not obviously morphologically similar. These trends in cranial morphology and biomechanics provide insights into behavioral and ecological factors shaping the skull of a trophically diverse clade of mammals., (© 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.)

Objective: To evaluate variation of electromyographic (EMG) activity and sensitivity between different sites of anterior temporalis (AT) muscle., Materials and Methods: Sixteen healthy subjects (eight men: 28.8 ± 5.2 year old and eight women: 29.1 ± 3.9) participated in one experimental session. EMG activity during masticatory muscle contraction was recorded from nine sites at the AT muscle in a 3 × 3 grid with 1 cm between. The subjects maintained steady 30% of maximal voluntary contraction (MVC) using visual feedback. The surface EMG electrode was moved sequentially between these nine test sites and the contractions were repeated. One site was tested four times to assess test-re-test variability. The sensory threshold to electrical stimulation and impedance was also measured at the same sites as the placement of EMG electrodes., Results: The 30% MVC force values did not differ between sites (p = 0.863) or within the same site (p = 0.995) due to the feedback. The EMG activity during 30% MVC was highest at the anterior-superior site (p < 0.05) with a marginal difference within the same site (p = 0.044). Impedance was higher at the posterior-superior, posterior-middle and posterior-inferior sites (p < 0.05). The sensory threshold was highest at the posterior-superior site (p < 0.05)., Conclusion: These findings showed that electrodes close to the hairline have higher impedance and sensory thresholds and should be avoided. The anterior-superior site produces the highest EMG activity and lower sensory thresholds and can be recommended as the optimal site to place the electrode for contingent stimulation.

Temporalis transfers for reanimation in facial palsy have been criticised for the lack of neural input from a functioning facial nerve. Cross-facial nerve grafting to the deep temporal nerves may provide a solution. An anatomical study was performed to further elucidate the deep temporal nerves (DTN) and arteries, examining anatomical variation and infratemporal distribution. Seventeen temporalis muscles were dissected from 13 cadavers as part of a BSc project. The number, branching pattern, length and diameter of DTN were recorded. Arteries supplying the deep surface of temporalis and their relation to DTN were noted. Six specimens were processed using Sihler's staining technique. Arteries were injected with Iodixanol X-ray contrast medium and radiographs taken. All specimens displayed a single DTN originating from the anterior branch of V(3). A mean of 3 branches was observed. The nerve length was 14.22±3.95 mm. The point of entry of DTN into temporalis showed great consistency. Upon exiting the infratemporal fossa, the posterior deep temporal artery was deep and posterior to DTN in 65% of specimens. The branching pattern of DTN can be classified into three types. The deep arterial supply to temporalis was constant in all specimens. This study provides an anatomical basis for the planning and execution of cross-facial nerve grafting to temporalis, and for protection of vital structures. Furthermore, it helps to clarify inconsistencies in the literature regarding nomenclature of the nerve branching pattern of the deep temporal nerves., (Copyright © 2011 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.)

The temporalis muscle, which is one of the masticatory muscles, enables elevation and retraction of the mandible. Direct injury to the temporalis muscle, facial nerve, or temporal fat pad during cranial-base surgery can cause temporal hollowing. The temporalis muscle is currently described in almost all atlases and textbooks as comprising a single layer. In this study, a superficial layer of the temporalis muscle is described, clarifying the anatomy of this muscle. Twenty heads of adult cadavers were dissected. The gross anatomy of the temporalis muscle was examined after removing the skin, subcutaneous tissue, superficial temporal fascia, and deep temporal fascia. The superficial layer of the temporalis muscle was clearly distinguishable from the deep layer. The superficial layer originated from the same region as the deep layer, and the muscle fibers of the two layers were intermingled in the superior part of the muscle. The deep layer of the temporalis muscle, which is referred to in textbooks and atlases simply as the temporalis muscle, was exposed after removing the superficial layer. The existence of this superficial layer was confirmed herein both histologically and by magnetic resonance imaging. Henceforth, the superficial layer of the temporalis muscle must be included in descriptions of the temporalis muscle in anatomy textbooks and atlases. The findings of this study are important not only from the perspective of simply acquiring correct anatomical knowledge, but also from the surgical perspective in preventing temporal hollowing during related surgical procedures., (Copyright © 2011 Wiley-Liss, Inc.)

Purpose: The masticatory muscles have a common embryological origin. Despite numerous anatomical studies their close anatomical relationships are not always accurately described in anatomical treatises. An expansion of the masseter muscle inserted into the deep surface of the superficial temporal aponeurosis has been described. Despite the classical description of two transition bundles (Yoshikawa et al. in Kaibogaku Zasshi 37:206-217, 1962), the literature concerning these fibres has remained difficult to interpret. Given the clinical applications of the lengthening of the temporal muscle in myoplasty, it is important that we have accurate anatomical knowledge of it., Methods: We dissected 14 embalmed or untreated anatomical cadaver heads with a sex ratio of 1 in order to analyse the aforementioned fibres and their variations. A radiologic study allowed us to understand the entanglement of the fibres. 10 craniofacial MRI were processed by 3D MPR reconstruction., Results: The fibres were identified as an expansion of the posterior head of the masseter muscle and distinct from the two classically described transition bundles. These were present in all subjects of both sexes. We can systematically describe their origin, trajectory and termination., Conclusion: Fibres belonging to masseter muscle pass up to the zygomatic arch and terminate on the deep surface of the temporal fascia. Awareness of the nature and trajectory of these muscular fibres allows us to avoid taking "wrong path" when approaching the temporal muscle tendon on the coronoid process via the temporal fossa.