Pterygopalatine Fossa: Microsurgical Anatomy and its Relevance for Skull Base Surgery

Introduction The purpose of this study was to define the anatomical relationships of the pterygopalatine fossa (PPF) and its operative implications in skull base surgical approaches. Methods Ten cadaveric heads were dissected at the Dianne and M Gazi Yasargil Educational Center MicrosurgicaLaboratory, in Little Rock, AK, USA. The PPF was exposed through an extended dissection with mandible and pterygoid plate removal. Results The PPF has the shape of an inverted cone. Its boundaries are the pterygomaxillary fissure; themaxilla, anteriorly; themedial plate of the pterygoid process, and greater wing of the sphenoid process, posteriorly; the palatine bone,medially; and the body of the sphenoid process, superiorly. Its contents are the maxillary division of the trigeminal nerve and its branches; the pterygopalatine ganglion; the pterygopalatine portion of the maxillary artery (MA) and its branches; and the venous network. Differential diagnosis of PPF masses includes perineural tumoral extension along the maxillary nerve, schwannomas, neurofibromas, angiofibromas, hemangiomas, and ectopic salivary gland tissue. Transmaxillary and transpalatal approaches require extensive resection of bony structures and are narrow in the deeper part of the approach, impairing the surgical vision and maneuverability. Endoscopic surgery solves this problem, bringing the light source to the center of the surgical field, allowing proper visualization of the surgical field, extreme close-ups, and different view angles. Conclusion We provide detailed information on the fossa's boundaries, intercommunications with adjacent structures, anatomy of the maxillary artery, and its variations. It is discussed in the context of clinical affections and surgical approaches of this specific region, including pterygomaxillary disjunction and skull base tumors.

Morphological and morphometric characterization of the "sphenoidal tubercle" / Caracterización morfológica y morfométrica del tubérculo esfenoidal

The sphenoidal tubercle is a bone elevation located in the anterior edge of the infratemporal crest of the sphenoid greater wing, where the temporal and lateral pterygoid muscles have their origin. This bone accident presents varied morphology so its description and denomination are a topic of discussion. 60 dry skulls obtained from the morphology laboratory of the Biomedical Basic Sciences Department of the University of Talca were used for a morphological and morphometric analysis of the sphenoidal tubercle including its morphology, diameters (anteroposterior, transverse and vertical) and the distance to the grooves for the maxillary artery and maxillary nerve. Sphenoidal tubercle had a prevalence of 98.4 % of all dry skulls analyzed with a bilateral presentation in the 76.6 % of the cases. According to its different forms of presentation established by Cáceres et al., (2016) the pyramidal form was the most frequent with a 25.7 %. The average diameters were of 4.12 mm anteroposterior, 5.50 mm transverse and 3.89 mm vertical. The average distance to the grooves of the maxillary artery and maxillary nerve were 9.04 mm and 7.6 mm, respectively. Sphenoidal tubercle is a constant bone accident with a variated morphology and measures. Due to its anatomical relations with important neurovascular elements such as the maxillary artery and the maxillary nerve, it may be used as a reference point for surgical access to the infratemporal fossa. From this analysis we establish that the denomination of "infratemporal process" is more accurate, because the development of this bone accident is from muscular traction performed by the lateral pterygoid muscle and the deep portion of the temporal muscle causing great variations in its morphology, probably due to external and functional parameters or even influenced by the biotype.

El tubérculo esfenoidal es una elevación ósea ubicada en el extremo anterior de la cresta infratemporal del ala mayor del hueso esfenoides, donde presta inserción al músculo temporal y pterigoideo lateral. Presenta morfología variada, por lo que su descripción y denominación resultan motivo de discusión. 60 cráneos secos obtenidos del Laboratorio de Morfología del Departamento de Ciencias Básicas Biomédicas de la Universidad de Talca, fueron utilizados para realizar un análisis morfológico y morfométrico del tubérculo esfenoidal evaluando forma, diámetros (anteroposterior, laterolateral y vertical) y distancia con el surco de la arteria y nervio maxilar. El tubérculo esfenoidal tuvo una prevalencia del 98,4 % del total de cráneos analizados, presentándose bilateralmente en el 76,6 % de los casos. De acuerdo a las diferentes formas de presentación establecidas por Cáceres et al (2016) la forma piramidal fue la más frecuente con un 25,7 %. Los diámetros promedio fueron de 4,12 mm anteroposterior, 5,50 mm laterolateral y 3,89 mm vertical. Las distancias promedio con el surco de la arteria y nervio maxilar fueron de 9,04 mm y 7,6mm, respectivamente. El tubérculo esfenoidal es un accidente óseo constante de morfología y dimensiones variadas. Debido a sus relaciones con elementos vasculares de importancia, tales como la arteria y nervio maxilar, podría ser utilizado como elemento de referencia para el acceso quirúrgico a la fosa infratemporal. A partir de su análisis planteamos que su denominación como "proceso infratemporal" sería más apropiado, debido a que se desarrollaría a partir de la tracción muscular ejercida por el musculo pterigoideo lateral y la porción profunda del músculo temporal, ocasionando variaciones notables en su morfología, probablemente debido a factores externos y funcionales o incluso influenciada por el biotipo.

Unusual origin and relations of the accessory meningeal artery: a case report / Origen inusual y relaciones de la arteria meníngea accesoria: reporte de un caso

SUMMARY: Accessory meningeal artery is a branch of the first part of the maxillary artery. It supplies the structures in the infratemporal fossa and the dura mater in the middle cranial fossa. Accessory meningeal artery arose from the middle meningeal artery, 25 mm below the base of the skull and entered the middle cranial fossa through the foramen ovale. The two roots of the auriculotemporal nerve looped around it. The knowledge of the variant origin and relations may be useful during the surgeries of the infratemporal fossa. It might also be useful to the radiologists.

RESUMEN: La arteria meníngea media es una rama accesoria que emerge al inicio de la arteria maxilar. Suministra la vascularización a nivel de la fosa infratemporal y la duramadre en la fosa craneal media. En este trabajo, surgió una arteria meníngea accesoria de la arteria meníngea media, a una 25 mm por debajo de la base del cráneo, accediendo en la fosa craneal media a través del foramen oval. Las dos raíces del nervio auriculotemporal la rodeaban. El conocimiento de esta variación y sus relaciones pueden ser útiles durante las cirugías de la fosa infratemporal, como así también puede ser útil para los radiólogos.

Avaliação do diâmetro do ramo intraósseo da artéria alveolar superior posterior e sua relação com a cirurgia de levantamento do seio maxilar ­ estudo transversal / Evaluation of intra-osseous branch of posterior superior alveolar artery diameter and its relation with the maxillary sinus

Objetivo: descrever a anatomia do ramo intraósseo da artéria alveolar superior posterior (riAASP) na parede lateral do seio maxilar. Material e métodos: 31 pacientes se encaixaram nos critérios de inclusão para a pesquisa. Avaliou-se a presença ou não do riAASP, sua distância até o assoalho do seio maxilar e até a crista alveolar, e seu diâmetro nas regiões dentais posteriores bilateralmente em maxila, comparando regiões dentadas com edentadas através de TCFCs. Resultados: o riAASP foi identificado em 21 pacientes (67,7%), sendo mais visualizado na região de primeiro molar. Foram avaliadas 248 regiões dentais de 31 pacientes, onde o riAASP foi visualizado e mensurado em 153 regiões (61,7%). Quanto mais posterior era a região, maior era o diâmetro do vaso, tanto para regiões dentadas quanto para as edentadas, e o diâmetro médio encontrado foi de 1,2 mm. A distância do riAASP até o assoalho do seio maxilar nas regiões dentadas não apresentou diferença estatisticamente significante nas diferentes regiões dentais. Já nas regiões edentadas, quanto mais posterior foi a região, menor foi esta distância. Em relação à distância da artéria até a crista alveolar, quanto mais anterior era a região dental, mais distante da crista o riAASP se posicionou. Conclusão: o conhecimento anatômico, a solicitação de exames de tomografi a computadorizada, a interpretação no planejamento pré-operatório e a habilidade do cirurgião poderão eliminar ou diminuir os acidentes relacionados à hemorragia do riAASP durante a cirurgia de levantamento do seio maxilar.

Objective: to define the anatomy of the intraosseous branch of the posterior superior alveolar artery (ioPSAA) in the lateral wall of the maxillary sinus. Material and methods: 31 patients meet the inclusion criteria for the study. The presence or absence of ioAASP, its distance to the floor of the maxillary sinus, to the alveolar crest and its diameter, were evaluated in the posterior dental regions bilaterally in the maxilla, comparing edentulos and dentate regions through CBCTs. Results: the ioPSAA was identifi ed in 21 patients (67.7%), being more visualized in the 1st molar region. A total of 248 dental regions of 31 patients were evaluated, where ioAASP was visualized and measured in 153 regions (61.7%). The diameter of the artery increases as it runs posteriorly in the maxilla, for both toothed and edentate regions. The mean diameter found was 1.2 mm. The distance from the ioPSAA to the maxillary sinus fl oor in the dentate regions did not present a statistically significant difference in the different dental regions. In the edentate regions, the more posterior the region, the smaller the distance to the sinus floor. Regarding the distance from the artery to the alveolar crest, the more anteror the dental anterior, the greater the distance of ioPSAA from the alveolar crest. Conclusion: anatomical knowledge, the need for CT scans, its interpretation in the preoperative planning, and the surgeon's ability, may eliminate or reduce the accidents related to riAASP hemorrhage during maxillary sinus surgery.

Evaluación de la arteria alveolo-antral mediante tomografía volumétrica en población mexicana y su relación con levantamiento del piso del seno maxilar / CBCT evaluation of the alveolar antral artery in a mexican cohort and its relationship to maxillary sinus floor lifting

Introducción: El conocimiento de la anatomía de la región maxilar debe ser esencial para el cirujano antes de realizar levantamiento del seno maxilar para evitar complicaciones. La arteria alveolo antral forma una anastomosis intraósea con la arteria infraorbitaria a nivel de la pared antero lateral del seno maxilar, aproximadamente a una distancia de entre 18.9 y 19.6 mm desde el reborde alveolar maxilar. La arteria alveolo antral es la encargada de dar vascularidad a la membrana mucosa del seno maxilar, pared antero lateral del seno y tejido perióstico subyacente.Objetivo: Describir y establecer la frecuencia, diámetro y localización dela anastomosis entre la arteria infraorbitaria y la arteria alveolar posterior superior, llamada arteria alveolo antral y su relación con la cresta ósea alveolar en una población mexicana. Material y métodos: Se realizaun protocolo de estudio observacional, descriptivo y transversal en una población de 1,116 pacientes derecho habientes del Instituto de Seguridad Social y Servicios para los Trabajadores del Estado (ISSSTE), en el oriente de la Ciudad de México, mediante la revisión de estudios de tomografía volumétrica computarizada. Resultados: Se encuentra la anastomosis arterial en el 90 por ciento de los estudios revisados, correspondiente a 1,005 estudios de tomografía.

Introduction: In order to avoid complications, it is essential for surgeonsto have a detailed knowledge of the anatomy of the superior maxillarybone prior to performing any sinus lift procedure. The alveolarantral artery forms an intraosseous anastomosis with the infraorbitalartery at the level of the anterolateral wall of the maxillary antrum at anapproximate distance of between 18.9 and 19.6 mm from the maxillaryalveolar ridge. The alveolar antral artery is responsible for providingvascularity to the mucous membrane of the maxillary sinus, the anteriorlateral wall of the sinus, and the underlying periosteal tissue. Objective:To analyze and establish the frequency, diameter, and locationof the anastomosis between the infraorbital artery and the posteriorsuperior alveolar artery known as the alveolar antral artery, and itsrelationship to the alveolar bone crest in a Mexican cohort. Materialand methods. We conducted a cross-sectional observational descriptivestudy involving a cohort comprised of 1,116 patients of the Institute forSocial Security and Services for State Workers (ISSSTE) on the eastside of Mexico City. The study consisted of a review of CBCT studies.Results: The arterial anastomosis was found in 90% of the 1,005 CBCTstudies reviewed, based on which the following values were determinedfor the distance between the alveolar ridge and the canal of the alveolarantral artery: for the fi rst premolar, 18.24 mm; second premolar,17.35 mm; fi rst molar, 16.96 mm, and for the second molar, 18.75 mm.Conclusions: We established the average measurements for the locationof the vascular bundle in question and the measurements neededto safeguard it along its course, which is important for the preservationand osseointegration of bone grafts placed during maxillary sinus liftprocedures, thus providing a margin of safety not previously reportedin the literature for a Mexican cohort.

Evaluation of the posterior superior alveolar artery and the maxillary sinus with CBCT

Assessment of the maxillary sinus anatomy before sinus augmentation is important for avoiding surgical complications, because of the close anatomical relationship between the posterior maxillary teeth and the maxillary sinus. The posterior superior alveolar artery (PSAA) is the branch of the maxillary artery that supplies the lateral sinus wall and overlying membrane. We evaluated the location of the PSAA and its relationship to the alveolar ridge and maxillary sinus using cone beam computed tomography (CBCT). The study group consisted of 135 CBCT scans (270 sinuses) obtained from the archive of the dentomaxillofacial radiology department at Yeditepe University Faculty of Dentistry, Istanbul, Turkey. The distance between the lower border of the artery and the alveolar crest, bone height from the sinus floor to the ridge crest, distance from the artery to the medial sinus wall, and the diameter and location of the artery were determined. The occurrence of septa and pathology were recorded from CBCT scans. The PSAA was observed in 89.3% of sinuses, and 71.1% of arteries were intraosseous with diameters mostly < 1 mm (68.9%). The prevalence of sinus septa was 55.2%, and that of sinus pathology was 57.4%. The mean age was 43.07 ± 17.55 years. There was a statistically significant difference between the location of the artery and gender (p < 0.05). The prevalence of sinus membrane thickening was 57.4%. Detailed knowledge about the location of the PSAA and sinus morphology may be obtained with CBCT before maxillary sinus surgery.

Clinical significance of maxillary artery and its branches: a cadaver study and review of the literature / Significado clínico de la arteria maxilar y sus ramas: un estudio en cadáver y la revisión de la literatura

The aim of this study was to investigate the anatomy of the maxillary artery (MA) and its branches. Fourteen sides of Turkish adult cadavers were dissected. The specimens were classified according to the relation between MA and the lateral pterygoid. After the removal of the lateral pterygoid, parts and branches of MA were exposed. We classified the branching patterns of MA in the pterygopalatine fossa. The calibers and lengths of the arteries, and the distance between the zygomatic arch and MA, and between the infratemporal crest and MA were measured. The MA was found superficial to the lateral pterygoid in 57.2 percent. The inferior alveolar artery (IA) was arisen from MA before the middle meningeal artery (MM) in 35.7 percent, after MM in 35.7 percent. The IA and MM were arisen from the same area of MA in 14.3 percent. In other two cases IA was arisen from the beginning of MA (14.3 percent). According to the contours of third portion of MA, we classified "Y" type (50 percent), "intermediate-T" type (14.3 percent), and "M" type (35.7 percent). This reinvestigation of the clinical anatomy of MA may provide useful information to the head and neck surgeons, dentists, neurosurgeons and radiologists related with this region.

El objetivo de este estudio fue investigar la anatomía de la arteria maxilar (AM) y sus ramas. Fueron disecados 14 hemicabezas de cadáveres turcos adultos. Las muestras fueron clasificadas de acuerdo a las relaciones entre AM y el músculo pterigoideo lateral. Después de la eliminación del músculo pterigoideo lateral, las partes y las ramas de AM fueron expuestas. Se clasificaron los patrones de ramificación de la AM en la fosa pterigopalatina. El calibre y la longitud de las arterias, la distancia entre el arco cigomático y la AM , y entre la cresta infratemporal y la AM fueron medidas. La AM se encuentra superficial al músculo pterigoideo lateral en el 57,2 por ciento. La arteria alveolar inferior (AI) se originó desde la AM antes que la arteria meníngea media (MM) en el 35,7 por ciento, y después de ésta en el 35,7 por ciento. La AI y MM se originaron en la misma zona de la AM en el 14,3 por ciento. En otros dos casos la AI se originó desde el inicio de AM (14,3 por ciento). De acuerdo con los contornos de la tercera porción de AM, se clasificaron como tipo "Y" (50 por ciento), tipo "intermedio-T" (14,3 por ciento), y de tipo "M" (35,7 por ciento). Esta investigación de la anatomía clínica de la AM puede proporcionar información útil a los cirujanos de cabeza y cuello, odontólogos, neurocirujanos y radiólogos relacionados con esta región.

Unilateral variation in the origin of the inferior alveolar and buccal arteries: a case report / Variación unilateral en el origen de las arterias alveolar inferior y bucal: reporte de un caso

The maxillary artery (MA) is one of the terminal branches of the external carotid artery (ECA) and is located in the infratemporal fossa (IF). Some of the branches in this region are the inferior alveolar artery (IAA) and the buccal artery (BA), both descending branches. Here, we report an unusual unilateral origin of the IAA and the BA from a common trunk directly from the ECA. We conducted a routine dissection of both IF in a 54-year-old hispanic male cadaver. Fixed with Universidad de los Andes® conservative solution and red latex for vascular filling. On each side, the MA is observed superficially located over the lateral pterygoid muscle. On the right side, the IAA and the BA originate from a common trunk from the ECA approximately 5 mm prior to the bifurcation into their terminal branches. On the left side, the IAA originates from the MA that is immediately next to its origin, making a common trunk with the pterygoid branches. Knowing the morphology of the MA and its branches at the IF is important for oral and maxillofacial surgery procedures; and any variation in the origin or course of these arteries may result in the patient's increased morbidity during some invasive procedure in the area.

La arteria maxilar (AM) es una rama terminal de la arteria carótida externa (ACE), y se ubica en la región infratemporal (RI). Algunas de sus ramas en esta región son la arteria alveolar inferior (AAI) y la arteria bucal (AB), ambas ramas descendentes. En este trabajo informamos de un inusual origen unilateral de la AAI y de la AB a partir de un tronco común desde la ACE. Se realizó una disección de rutina de ambas regiones infratemporales en un cadáver de 54 años, sexo masculino, caucásico. Fijado con solución conservadora Universidad de los Andes® y repleción vascular con látex rojo. A cada lado, se observa la AM en ubicación superficial sobre el músculo pterigoideo lateral. Al lado derecho, la AAI y la AB se originan de un tronco común desde la ACE aproximadamente 5 mm antes de la bifurcación en sus ramas terminales. Al lado izquierdo la AAI se origina de la AM inmediato a su origen, formando un tronco común con los ramos pterigoideos. El conocimiento de la morfología de la AM y de sus ramas en la RI es de importancia en procedimientos odontológicos, de cirugía oral y maxilofacial. Por lo que cualquier variación en el origen o trayecto de estas arterias puede predisponer a un paciente a una mayor morbilidad durante algún procedimiento invasivo en la zona.

Variations in the origin and course of the inferior alveolar neurovascular bundle

The knowledge of the neurovascular relationships of the infratemporal region is of great interest for any surgical procedure in the area. The region contains important structures such as the mandibular nerve, the maxillary artery and the muscles of mastication. In this article we present a case of atypical origin and course of inferior alveolar nerve [IAN] and inferior alveolar artery [IAA]

An unusual relationship between the inferior alveolar nerve, lingual nerve and maxillary artery / Una inusual relación entre los nervios alveolar inferior y lingual y la arteria maxilar

The knowledge of the neurovascular relationships of the infratemporal region is relevant in odontostomatology practice. In this article we present a case of atypical communication between the inferior alveolar nerve and lingual nerve associated with a change in relations with the maxillary artery, and discusses some clinical implications that these relations have on the development of the suplementary innervation and the anesthesia.

El conocimiento de las relaciones entre los elementos neurovasculares de la región infratemporal es relevante en la práctica odontoestomatológica. En el presente artículo presentamos el caso de una comunicación atípica entre el nervio alveolar inferior y el nervio lingual asociados a una variación en las relaciones con la arteria maxilar, y sediscut en algunas implicancias clínicas que estas relaciones tienen en el desarrollo de inervación suplementaria y en la práctica anestésica.

Estudo da anatomia da região do forame esfenopalatino na parede lateral do nariz através da dissecção endoscópica em cadáveres / Study of the anatomy of the sphenopalatine foramen region in the lateral nasal wall during endoscopic cadaver dissection

INTRODUÇÃO: Apesar do índice de sucesso da cirurgia da ligadura ou cauterização da artéria esfenopalatina, para o tratamento da epistaxe severa, ser maior que 95%, a falha pode variar de 2% a 10%. Algumas variações anatômicas na parede lateral do nariz são relatadas, sendo referentes à localização do forame esfenopalatino (FEP), à presença de um forame acessório, à ramificação das artérias e à dimensão e morfologia do FEP. A variação anatômica dessa região assim como a escassez de estudos endoscópicos mostrando pontos de reparo para o encontro da artéria esfenopalatina e seus ramos podem justificar a falha cirúrgica em alguns casos, assim como a dificuldade técnica encontrada por alguns autores. OBJETIVO: Descrever a anatomia da região do FEP na parede lateral do nariz e as possíveis variações anatômicas, durante a dissecção endoscópica em cadáveres, e observar as possíveis diferenças entre os achados anatômicos, o gênero (masculino/feminino) e o grupo étnico/racial, assim como a simetria entre as fossas nasais. CASUÍSTICA E MÉTODOS: Estudo anatômico prospectivo realizado de setembro de 2006 a janeiro de 2007. A região do FEP de 61 cadáveres frescos (122 fossas nasais) foi cuidadosamente dissecada, sob visibilização endoscópica. Prevaleceram os cadáveres do sexo masculino (75%) e grupo étnico/racial pardo, seguidos de negros e brancos. Foram observados a presença da crista etmoidal da lâmina perpendicular do osso palatino, a localização dos forames esfenopalatino e acessório, o número de ramos arteriais emergentes pelos forames e a distância dos mesmos à espinha nasal anterior. Os dados foram analisados em relação ao gênero, grupo étnico/racial e simetria entre as fossas nasais do mesmo cadáver. Foi, ainda, avaliada a predição da presença do forame acessório em relação ao número de ramos arteriais emergentes através do FEP, à localização do FEP e à distância do FEP à espinha nasal anterior...

INTRODUCTION: Even though the success rate of sphenopalatine ligation is greater than 95%, some authors have reported some difficulties in isolating those arteries during endoscopic surgical procedure. The failure rate of the sphenopalatine artery ligation or cauterization may vary from 2% to 10%. Some anatomical variations on the nose lateral wall are reported, with reference to the sphenopalatine foramen (SPF) location, the presence of an accessory foramen, arteries ramification and SPF dimension and morphology. Anatomical variation of the region, as well as scarcity of endoscopic studies showing landmarks to find the sphenopalatine artery and its branches may justify surgical failure. OBJECTIVE: The purpose of this study was to describe the anatomy of SPF region and possible anatomical variations, during the endoscopic cadaver dissection and to observe the symmetry between nasal sides and the relationship to gender and racial group. CASUISTICS AND METHODS: It is a prospective anatomical study developed from September, 2006 to January, 2007. The SPF of 61 fresh cadavers (122 nasal fossae) was carefully endoscopic dissected. Male (75%) and mixed race cadavers prevailed. Presence of ethmoidal crest, location of sphenopalatine and accessory foramens, number of arterial branches emerging through foramens and distances from the foramens to anterior nasal spine were observed. Data were analyzed in relation to gender, racial group and symmetry of the same cadaver. Prediction of the presence of accessory foramen was evaluated in relation to number of arterial branches emerging through SPF, SPF location and distance from the SPF to the anterior nasal spine. RESULTS: Ethmoidal crest was present in 100% of cadavers, being anterior to the SPF in 98.4% of times. The most frequent SPF location was the transition region of middle and superior meatus (86.9%). Mean distance from SPF and accessory foramen to anterior nasal spine was 6.6cm and 6.7cm, respectively...

Anatomical study of the maxillary artery at the pterygomaxillary fissure in a Thai population: its relationship to maxillary osteotomy.

BACKGROUND: The maxillary artery (MA) and its terminal branches are commonly damaged in the maxillary osteotomy, especially during separation of the pterygomaxillary junction (PMJ). OBJECTIVE: To evaluate the positional relationship between the MA at the pterygomaxillary fissure (PMF) and the PMJ in Thais, as well as to measure the diameter of the MA as it enters the pterygopalatine fossa (PPF) and the heights of PMJ, maxillary tuberosity and posterior maxilla. SUBJECTS AND METHOD: Both sides of 100 Thai adult cadavers (50 males and 50 females) were examined The mean age of the subjects was 64.5 +/- 12.8 years. With the lateral infratemporal approach, the branches from the third part of the MA, PMJ and posterolateral maxilla were dissected. Measurements taken included the following: First, the distance from the most inferior point of the PMJ to the most inferior position of the MA as it entered the PPF; second, the external diameter of the MA as it entered the PPF; third, vertical heights of the PMJ, maxillary tuberosity and posterior maxilla. Means, standard deviations and ranges were determined and statistical differences were calculated between sides and genders at p < 0. 05. RESULTS: The MA entered the PPF at a mean distance of 23.5 +/- 2.5 mm above the most inferior point of the PMJ. The mean external diameter of the MA as it entered the PPF was 2.8 +/- 0.6 mm. The mean heights of the PMJ, maxillary tuberosity and posterior maxilla were 19.5 +/- 2.3 mm, 6.1 +/- 2.7 mm, and 25.6 +/- 3.3 mm, respectively. There were no differences with respect to side and gender, except that the distance from the most inferior point of the PMJ to the most inferior position of the MA as it entered the PPF was longer in males than in females (p < 0.05). CONCLUSION: The mean location of the MA was 23.5 mm apart from the most inferior point of the PMJ, therefore, dysjunction of the PMJ using an osteotome with a 15-mm cutting edge may be conducted without damaging to the MA. When properly placed, the margin of safety from the superior cutting edge of the osteotome to the MA is approximately 8 mm in adults.