Anatomical localisation of the maxillary nerve with the use of computed tomography to aid nerve block placement in dogs.

BACKGROUND: The maxillary block is a commonly used anaesthetic technique in dogs; however, no universal recommendations for the best method to perform this block exist. Differences between using this block in brachycephalic and non-brachycephalic breeds have not been examined. This study compared the position of the maxillary nerve using CT in brachycephalic and non-brachycephalic dogs. METHODS: Forty CT images of the heads of dogs of varying conformation were analysed. The distances and angles to the maxillary nerve from the injection site within the oral cavity were measured. If present in the same plane, the distance to the eye was measured. Measurements of jaw width and length were taken to ascertain if they correlated to the distance to the maxillary nerve from the oral cavity. RESULTS: There was no difference in angle between brachycephalic and non-brachycephalic dogs; however, the distance between nerve and injection point in brachycephalic dogs was generally greater. A regression equation relating maxillary nerve depth to jaw width was found. The eye was more likely to be in the plane of injection if the dog was non-brachycephalic. CONCLUSION: The discovered relationship between jaw width and maxillary nerve depth may allow more accurate injections to be made.

A morphometric analysis of the immature human infraorbital canal.

PURPOSE: The importance of the infraorbital canal in the growth of the maxilla and associated mid-facial region has significance for innervation of this region as well as the associated dentition, yet little is known about the development of the canal. An analysis of its dimensions and morphology during the late prenatal and early postnatal periods was thus undertaken. The aim of this study was to describe changes in the morphology, size and branching pattern of the infraorbital canal during the late prenatal and early postnatal stages of human growth. METHODS: Fifty human fetal and neonatal maxillae were analyzed. The sample included 27 late prenatal individuals (30 gestational weeks and birth) and 23 early postnatal individuals (birth and 1 year). Maxillae were scanned using a Nikon XTH 225 L micro-CT unit and analyzed using VG studiomax v3.2. Measurements included the maximum width, height and surface area of each foramen associated with the infraorbital canal and the total length of the canal, bilaterally. RESULTS: All the measurements of the canal were greater in the early postnatal group than in the late prenatal group, while the walls and branching pattern of the canal were better developed in the postnatal group. Bone development occurred within the walls as development proceeded. Variations in the branching pattern of the canal were found. CONCLUSION: The morphology of the infraorbital canal reflected the developmental stage of associated structures such as the dentition, maxillary sinus and orbit.

Suprazygomatic maxillary nerve block: an ultrasound and cadaveric study to identify correct sonoanatomical landmarks.

​PURPOSE: Suprazygomatic maxillary nerve blocks (SMB) are used in adult and pediatric patients to provide analgesia for midface surgery and chronic maxillofacial pain syndromes. The ultrasound-guided SMB technique ensures visualisation of the needle tip, avoidance of the maxillary artery and confirmation of local anesthetic spread. The goal of this study was to correctly identify SMB sonoanatomical landmarks to ensure the nerve block is performed safely and effectively. METHODS: Following an ultrasound-guided SMB with dye injection on 2 embalmed cadavers, pre-tragal face-lift style incision with a full thickness flap dissection was performed allowing accurate visualization of the bony landmarks being used for sonography and identification of the location of the injected dye. RESULTS: This study identifies the correct sonoanatomic landmarks as the maxilla and the coronoid process of the mandible which suggests that the block needle tip and local anesthetic injection are within the infratemporal fossa as opposed to the previously reported pterygopalatine fossa. CONCLUSION: An improved understanding of the sonoanatomy will aid clinicians who are learning, performing and teaching the ultrasound-guided suprazygomatic approach to the maxillary nerve block.

Revisiting major anatomical risk factors of maxillary sinus lift and soft tissue graft harvesting for dental implant surgeons.

The anatomical variations of the maxillary sinus septa, greater palatine artery, and posterior superior alveolar arteries might cause unexpected complications when they are damaged. Dentists who know these structures well might hope to learn more practical knowledge to avoid and assess injury preoperatively. Therefore, this review paper aimed to review the reported anatomy and variations of the maxillary sinus septa, greater palatine artery/nerve, and posterior superior alveolar artery, and to discuss what has to be assessed preoperatively to avoid iatrogenic injury. To assess the risk of injury of surgically significant anatomical structures in the maxillary sinus and hard palate, the operator should have preoperative three-dimensional images in their mind based on anatomical knowledge and palpation. Additionally, knowledge of the average measurement results from previous studies is important.

Infraorbital Foramen Decompression Surgery for the Infraorbital Nerve Hypoesthesia in Patients With Isolated Fracture of Maxillary Sinus Anterior Wall.

Isolated fracture of maxillary sinus anterior wall is relatively uncommon. If the extent of fracture is minimal, only conservative care is amenable, however, there is no agreement on whether infraorbital nerve dysfunction can be used as an indication for surgical intervention. This study was conducted to verify the effect of decompression surgery of infraorbital foramen for recovery of hypoesthesia. A total of 26 patients with unilateral fracture of maxillary sinus anterior wall were enrolled. Ten who received only conservative therapy were allocated in the control group, while sixteen patients were assigned to the decompression group. Pre- and post-treatment sensory assessment using visual analogue scale (VAS) was recorded. Overall treatment satisfaction was also evaluated by means of global assessment scale (GAS). Both absolute VAS value and score increment showed statistical difference only at 4 weeks (P = 0.010 and P = 0.021, respectively), but no significant difference at 1, 12, and 24 weeks. GAS score also showed no statistical significance (P = 0.386). Decompression surgery of infraorbital foramen does not have a significant effect on hypoesthesia recovery in isolated fracture of maxillary sinus anterior wall. Therefore, it is not recommended to perform the operation when the infraorbital nerve hypoesthesia is the only indication for the open reduction.

False and true accessory infraorbital foramina, and the infraorbital lamina cribriformis.

The infraorbital nerve (ION) and artery (IOA) course in the infraorbital canal (IOC) to exit through the infraorbital foramen (IOF). Few previous studies brought evidence of accessory IOF. Evaluation of the IOF in Cone Beam Computed Tomography (CBCT) is more accurate to determine whether or not foramina of maxilla are supplied by canaliculi deriving from the IOC. We performed a retrospective anatomical study of the CBCT files of 200 patients. An accessory infraorbital foramen located inferior to the infraorbital margin (AIOF) was found in 18/200 right maxillae and in 13/200 left ones. Canaliculi deriving from the IOC supplied accessory foramina in the sutura notha- AIOF(SN) - in 15 maxillae. Noteworthy, the AIOF(SN)-negative maxillae displayed the SN and the vascular foramina of Macalister. In 94% of cases the AIOF were unique. A single maxilla (3%) had a double AIOF. In a different case (3%) were found three accessory infraorbital foraminules transforming the anterior wall of the antrum into a veritable lamina cribriformis infraorbitalis. A single prior study distinguished AIOF from AIOF(SN), while most of different other ones were performed on dry bones. Therefore, the reports of prevalence for the number and location of AIOF should be regarded with caution. Foramina of the SN could equally get intraosseous and extraosseous supply, this distinction being accurately made in CBCT.

Technical considerations for approaches to the ultrasound-guided maxillary nerve block via the pterygopalatine fossa: a literature review.

BACKGROUND AND OBJECTIVES: Blockade of the trigeminal nerve and its branches is an effective diagnostic tool and potential treatment of facial pain. Ultrasound-guided injections in the pterygopalatine fossa (PPF) to block the trigeminal nerve divisions and sphenopalatine ganglion have been described but a consensus has yet to be reached over the ideal approach. We sought to delineate and compare the various approaches to the ultrasound-guided trigeminal divisions blockade via the PPF. METHODS: The literature search was performed by searching the National Library of Medicine's PubMed database, the Cochrane Database of Systematic Reviews and Google Scholar within the date range of January 2009-March 2019 for keywords targeted toward "trigeminal nerve," "maxillary nerve," or "pterygopalatine fossa," "ultrasound," and "nerve block," using an English language restriction. Six papers were included in the final review: one prospective double-blinded randomized controlled trial, one prospective descriptive study, one case series, two case reports, and one cadaveric study. RESULTS: There are three main approaches to the ultrasound-guided trigeminal nerve branches blockade via the PPF: anterior infrazygomatic in-plane, posterior infrazygomatic in-plane, and suprazygomatic out-of-plane approaches. Each showed injectate spread to the PPF in cadaver, adult and pediatric patients, respectively.1-5 Injectate used varied from 3 to 5 mL to 0.15 mL/kg. CONCLUSIONS: These studies demonstrated that the PPF is a readily accessible target for the ultrasound-guided maxillary nerve block via three main approaches.2 The ideal approach is yet to be determined and must be further explored.

Assesment of accessory branches of canalis sinuosus on CBCT images

BACKGROUND: The aim of this study is to describe the presence, to reveal the frequency and characteristics of accessory canals (ACs) of the canalis sinuosus (CS) by cone beam computed tomography (CBCT). MATERIAL AND METHODS: A total of 326 CBCT examinations were scanned retrospectively. The anatomical views were evaluated on sagittal, axial, coronal and cross sectional imaging. The following parameters were recorded: age, sex, presence or absence of ACs, location in relation to the adjacent teeth and distance to the nasal cavity floor (NCF), alveolar ridge crest (ARC) and buccal cortical bone (BCB), and incisive canal. All the collected data were statistically analyzed. RESULTS: 113 patients (34,7%); presented ACs in total 214 foramina of the sample. There were no statistically sig-nificant changes in the presence of ACs regarding age groups excluding 80-89 years. But there is a statistically significant difference regarding the frequency of ACs and the gender. The prevalence for male patients was higher than female patients. Curved-shape configuration of CS prevalence is found as 69,15%. The prevalence of vertical tracing is 26,16% and Y-shape configuration of CS prevalence is 4,67%. Diameter of the foramens of the CS branches was 1.30 mm. The mean distance of the AC to the NCF, BCB, and ARC were found 13,83 mm, 6,60 mm and 5,32 mm, respectively. CONCLUSIONS: In the anterior palatal region, ACs are mostly related to CS's branches. So; knowing the course of CS branches in surgical planning and radiographic evaluations in this region is extremely important for preventing complications and avoiding misdiagnosis

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Ultrasound-guided maxillary nerve block: an anatomical study using the suprazygomatic approach.

PURPOSE: Although a maxillary nerve (MN) block reportedly provides satisfactory analgesia for midface surgery and chronic maxillofacial pain syndromes, a safe and reliable MN block technique has not been reported. The goal of this anatomical study was to quantify the various angles and depth of the block needle, as well as to evaluate the impact of volume on the extent of injectate spread that might influence anesthetic coverage and block-related complications. METHODS: Following an ultrasound-guided suprazygomatic MN block with dye injection, a dissection was performed in the pterygopalatine fossa (PPF) of four lightly embalmed cadaveric specimens. Half of the specimens were injected with 5 mL of dye, and the other half with 1 mL of dye. The needle depth was measured from the ultrasound images and using rubber markers. Following injection, dissection was performed to map the area of dye spread. RESULTS: The median [interquartile range (IQR)] distance from the skin to the PPF was 37 [36-43] mm and 47 [40-50] mm by ultrasound and rubber marker methods, respectively. The median [IQR] needle orientation was 14 [11-32] degrees inferiorly and 15 [10-17] degrees posteriorly. The PPF was consistently dyed in the 5 mL group, but sporadically dyed in the 1 mL group. In the 5 mL group, spread outside of the PPF was seen. CONCLUSIONS: We showed that 5 mL of injectate far exceeds the capacity of the PPF, leading to drug spread outside of the PPF. Moreover, we found that 1 mL of injectate largely covered the nerve, suggesting a more efficacious and safer block procedure. This finding will need confirmation in future clinical studies.

Frequency of canalis sinuosus and its anatomic variations in cone beam computed tomography images / Frecuencia de canalis sinuosus y sus variaciones anatómicas en imágenes de tomografía computarizada de haz cónico

The aim of this paper was to determine the frequency of Canalis Sinuosus (CS) and its anatomic variations. A total of 236 cone beam computed tomography (CBCT) images were studied. Characteristics of the canal such as its form, pathway and diameter were analyzed. The CS was clearly visualized in 100 % of the images with variations in the canal observed in up to 46 % of the cases. In 79 % of the cases the variation was found to be bilateral. The most common variation was an increase in the diameter (> 1mm) of the CS. Considering that the anterior region of the middle third of the face is a common place for clinical interventions, this study supports the need to perform a thorough evaluation of the maxillary region prior to clinical interventions in order to prevent complications such as direct or indirect injury to the anterior superior alveolar neurovascular bundle contained within the CS.

El objetivo de este trabajo fue determinar la frecuencia de Canalis Sinuosus (CS) y sus variaciones anatómicas. Se estudiaron un total de 236 imágenes de tomografía computarizada de haz cónico (CBCT). Se analizaron las características del canal, como su forma, vía y diámetro. El CS se visualizó claramente en el 100 % de las imágenes, observándose variaciones en el canal en hasta el 46 % de los casos. En el 79 % de los casos la variación fue bilateral. La variación más común fue un aumento en el diámetro (> 1 mm) de la CS. Teniendo en cuenta que la región anterior del tercio medio de la cara es un lugar común para las intervenciones clínicas, este estudio apoya la necesidad de realizar una evaluación exhaustiva de la región maxilar antes de las intervenciones clínicas para prevenir complicaciones como lesiones directas o indirectas a el haz neurovascular alveolar superior anterior contenido dentro de la CS.

The Value and Application of Personalized Needle Modification in Percutaneous Infrazygomatic Radiofrequency in Isolated Maxillary Nerve Pain through the Foramen Rotundum.

BACKGROUND: Percutaneous infrazygomatic radiofrequency (PIR) is a common approach used to block isolated maxillary nerve (V2) pain through the foramen rotundum (FR) in patients with trigeminal neuralgia (TN). Nevertheless, when using this method, there is a risk of accidental penetration of the superior orbital fissure (SOF) and the optic canal (OC) that may result in the injury of the vessels and nerves in that area, and in some severe cases may lead to blindness. According to the blocking of the external orifice of the FR and whether a curved needle was used, combined angle deviation from the path of percutaneous infrazygomatic approach, the FR to the SOF or the OC in the treatment of V2 pain, in which no research has reported the angle, we analyzed the value and application of personalized needle modification in PIR in isolated maxillary nerve pain through the FR. OBJECTIVES: The following study examined the relationship between the FR and the SOF, and analyzed the clinical significance of personalized needle modification in computed tomography (CT)-guided PIR ablation of the maxillary nerve through the FR in patients with TN. STUDY DESIGN: Randomized, review, clinical research study. SETTING: Department of Anesthesiology and Pain Medical Center, Jiaxing, China. METHODS: Three-dimensional reconstruction was performed in 88 patients and 136 patients with PIR ablation in isolated maxillary nerve pain through the FR. According to the blocking of the external orifice of the FR and whether a curved needle was used, patients were divided into 4 groups: curved-needle blocking group (CB), straight-needle blocking group (SB), straight needle no-blocking group (SN), and curved-needle no-blocking group (CN). RESULTS: The results obtained revealed minimum H (shortest diameter of the FR) = 1.0 mm and minimum L (length of the FR tubes) = 3.7 mm. The distance between the external orifice of the FR and the SOF (FS) was 5.16 ± 1.33 mm. The angle A (between the radiofrequency needle and the sagittal plane) was 39 ± 3.95°; the angle between the canthomeatal line and the CT scan line (ACT) was 58.99 ± 6.23°; the puncture depth (LS) was 63.99 ± 4.24 mm; the deviation angle of the misplacement into the SOF (SAF) was 2.96 ± 0.71°; the deviation angle of the misplacement into the OC (OAF) was 4.95 ± 0.73°. In addition, the postoperative Numeric Rating Scale scores in the CB group were significantly lower compared with the SB group, whereas the probability of entering the SOF in the CB group was significantly lower compared with the SB group. The total number of punctures in the SN group was less than that in the CN group. LIMITATIONS: Additional clinical data should be collected to preserve the results in future work. CONCLUSIONS: The distance between the FR and the SOF or the OC was only few millimeters, and slight angle error could lead to the SOF and the OC. For patients with blockage in the path, the treatment of radiofrequency with personalized needle modification could improve the curative effect and reduce the risk of accidental SOF penetration. KEY WORDS: Trigeminal neuralgia, foramen rotundum, superior orbital fissure, radiofrequency, personalized needle modification.

Computed tomography evaluation of the morphometry and variations of the infraorbital canal relating to endoscopic surgery / Computed tomography evaluation of the morphometry and variations of the infraorbital canal relating to endoscopic surgery

Abstract Introduction: The course of the infraorbital canal may leave the infraorbital nerve susceptible to injury during reconstructive and endoscopic surgery, particularly when surgically manipulating the roof of the maxillary sinus. Objective: We investigated both the morphometry and variations of the infraorbital canal with the aim to show the relationship between them relative to endoscopic approaches. Methods: This retrospective study was performed on paranasal multidetector computed tomography images of 200 patients. Results: The infraorbital canal corpus types were categorized as Type 1: within the maxillary bony roof (55.3%), Type 2: partially protruding into maxillary sinus (26.7%), Type 3: within the maxillary sinus (9.5%), Type 4: located anatomically at the outer limit of the zygomatic recess of the maxillary bone (8.5%). The internal angulation and the length of the infraorbital canal, the infraorbital foramen entry angles and the distances related to the infraorbital foramen localization were measured and their relationships with the infraorbital canal variations were analyzed. We reported that the internal angulations in both sagittal and axial sections were mostly found in infraorbital canal Type 1 and 4 (69.2%, 64.7%) but, there were commonly no angulation in Type 3 (68.4%) (p < 0.001). The length of the infraorbital canal and the distances from the infraorbital foramen to the infraorbital rim and piriform aperture was measured as the longest in Type 3 and the smallest in Type 1 (p < 0.001). The sagittal infraorbital foramen entry angles were detected significantly smaller in Type 3 and larger in Type 1 than that in other types (p = 0.003). The maxillary sinus septa and the Haller cell were observed in 28% and 16% of the images, respectively. Conclusion: Precise knowledge of the infraorbital canal corpus types and relationship with the morphometry allow surgeons to choose an appropriate surgical approach to avoid iatrogenic infraorbital nerve injury.

Resumo: Introdução: O trajeto do canal infraorbitário pode predispor o nervo infraorbitário a lesões durante cirurgias reconstrutoras e endoscópicas com manipulação do teto do seio maxilar. Objetivo: Investigamos a morfometria e as variações do canal infraorbitário e objetivamos demonstrar a relação entre elas, visando as abordagens endoscópicas. Método: Este estudo retrospectivo foi realizado em imagens de tomografia computadorizada multidetectora de seios paranasais de 200 pacientes. Resultados: Os tipos de corpos do canal infraorbitário foram categorizados como Tipo 1; inseridos no teto ósseo maxilar (55,3%), Tipo 2; projetando-se parcialmente dentro do seio maxilar (26,7%), Tipo 3; dentro do seio maxilar (9,5%), Tipo 4; localizado anatomicamente no limite externo do recesso zigomático do osso maxilar (8,5%). A angulação interna e o comprimento do canal infraorbitário, os ângulos de entrada do forame infraorbitário e as distâncias relacionadas à localização do forame foram medidos e suas relações com as variações do canal infraorbitário foram analisadas. Observamos que as angulações internas em ambos os cortes sagital e axial foram encontradas em sua maioria em canais infraorbitários Tipo 1 e 4 (69,2%, 64,7%) e, no geral, não houve angulação no canal Tipo 3 (68,4%) (p < 0,001). O comprimento do canal infraorbitário e as distâncias desde o forame infraorbitário até o rebordo infraorbitário e a abertura piriforme foram medidos e os mais longos foram identificadas no Tipo 3 e os mais curtos no Tipo 1 (p < 0,001). Os ângulos de entrada do forame infraorbitário em projeção sagital foram significativamente menores no Tipo 3 e maiores no Tipo 1, em relação aos outros tipos (p = 0,003). Septos nos seios maxilares e as células de Haller foram observados em 28% e 16% das imagens, respectivamente. Conclusão: O conhecimento preciso dos tipos de corpo do canal infraorbitário e a relação com a morfometria permitem que o cirurgião escolha uma abordagem cirúrgica apropriada para evitar lesões iatrogênicas do nervo infraorbitário.

Ectopic Infra Orbital Nerves: Case Series of a Dangerous Normal Variant.

Normal variations in the paranasal sinus region are well documented in literature. We present five cases of a little known normal variant, which can have serious implications for the patient as well as the operating surgeon. An ectopic infra orbital nerve canal coursing through the maxillary sinus has rarely been described in imaging literature. This may sometimes be mistaken for a simple septum in the maxillary sinus and may cause serious complications during Functional Endoscopic sinus surgery (FESS) surgeries. We describe the imaging findings and present a brief review of the previous publications on the same subject.

A Cadaveric Study of Ultrasound-Guided Maxillary Nerve Block Via the Pterygopalatine Fossa: A Novel Technique Using the Lateral Pterygoid Plate Approach.

BACKGROUND AND OBJECTIVES: This study aimed to describe and assess the accuracy and feasibility of a novel technique for ultrasound-guided maxillary nerve block using the lateral pterygoid plate (LPP) approach via the pterygopalatine fossa (PPF) in a soft cadaveric model. METHODS: Ten soft cadavers were studied. The curved array ultrasound transducer probe was applied over 1 side of the face of the cadavers in the open-mouth posture. It was placed transversely below the zygomatic arch for identifying the border of the maxillary tuberosity and the LPP. We tilted the curve probe from the caudal to the cranial direction until the uppermost part of the PPF was identified. The in-plane needle approach was used from the anterior-to-posterior and lateral-to-medial directions through the fossa, and 3 mL of methylene blue dye was injected. RESULTS: The spread of injectate after ultrasound-guided maxillary nerve block using the LPP approach was successfully performed in all cadavers as demonstrated by visualized moderate to marked traces of methylene blue within the PPF. No accidental injections in the maxillary arteries or facial nerves were observed. CONCLUSIONS: This cadaveric study suggests that ultrasound-guided maxillary nerve block using the LPP approach via the PPF has a high degree of accuracy and feasibility. Further studies are required to confirm its efficacy and safety for clinical application.

Infraorbital Nerve Located Medially to Postoperative Maxillary Cysts: A Risk of Endonasal Surgery.

BACKGROUND/AIMS: This study aimed to examine variations in the location of the infraorbital nerve relative to postoperative maxillary cysts to assess the potential risk of nerve injury during endonasal marsupialization. METHODS: Coronal computed tomography images of 130 patients (162 sides) with postoperative maxillary cysts who visited our clinic between 2003 and 2014 were reviewed from the viewpoint of the anatomical relationship between the infraorbital nerves and cysts. RESULTS: The proportions of the six locations were as follows: upside 45.1% (n = 73), separate 13.0% (n = 21), medial 5.6% (n = 9), lateral 14.2% (n = 23), in-between 7.4% (n = 12), and unevaluable 14.8% (n = 24). The proportion of the cases with a potential risk of infraorbital nerve damage during endoscopic marsupialization, including medial, in-between, and unevaluable locations, was 27.8%. Retrospective chart review revealed that 2 patients with a postoperative maxillary cyst that were unevaluable complained of persistent postoperative hypoesthesia of the cheek. CONCLUSION: The anatomical relationship between the infraorbital nerve and postoperative maxillary cysts varied among patients, with approximately one-fourth of the patients being at risk of infraorbital nerve injury even during endoscopic procedures.

An anatomical variant: evaluation of accessory canals of the canalis sinuosus using cone beam computed tomography.

BACKGROUND: The anatomical variation of the anterior superior alveolar nerve described as canalis sinuosus (CS) is a less known structure of anterior maxilla. Due to the fact that it contains anterior superior alveolar nerve as well as veins and arteries, exact localisation of this structure will allow surgeons to avoid complications. Hence, the aim of this study was to verify the presence, reveal the frequency and characteristics of accessory canals of CS. MATERIALS AND METHODS: This study was based on retrospective evaluation of cone beam computed tomography (CBCT) scans. A total of 1460 CBCT images were analysed and collected data were noted. The following parameters were recorded: age, sex, presence or absence of CS, location in relation to the adjacent teeth and impaction of canine teeth. RESULTS: A total of 6668 accessory canals were found in 1460 CBCT images. Of these, 672 (46.0%) were from female patients, and 788 (54.0%) were from male patients. 1034 (70.8%) of 1460 images had at least one accessory canal of CS. Maxillary intercentral region is the area where accessory canals were seen most frequently (n = 653, 44.72%). CONCLUSIONS: Canalis sinuosus is a bony canal which is incidentally found and less known structure of anterior portion of maxilla. Knowing the accessory canals deriving from this structure will allow surgeons to avoid complications and non-integration after dental implant procedures. Conventional imaging modalities have limited value in detecting this neurovascular structures. Therefore CBCT may have an important role for accurate diagnosis to reveal anatomical variations.

Computed tomography evaluation of the morphometry and variations of the infraorbital canal relating to endoscopic surgery.

INTRODUCTION: The course of the infraorbital canal may leave the infraorbital nerve susceptible to injury during reconstructive and endoscopic surgery, particularly when surgically manipulating the roof of the maxillary sinus. OBJECTIVE: We investigated both the morphometry and variations of the infraorbital canal with the aim to show the relationship between them relative to endoscopic approaches. METHODS: This retrospective study was performed on paranasal multidetector computed tomography images of 200 patients. RESULTS: The infraorbital canal corpus types were categorized as Type 1: within the maxillary bony roof (55.3%), Type 2: partially protruding into maxillary sinus (26.7%), Type 3: within the maxillary sinus (9.5%), Type 4: located anatomically at the outer limit of the zygomatic recess of the maxillary bone (8.5%). The internal angulation and the length of the infraorbital canal, the infraorbital foramen entry angles and the distances related to the infraorbital foramen localization were measured and their relationships with the infraorbital canal variations were analyzed. We reported that the internal angulations in both sagittal and axial sections were mostly found in infraorbital canal Type 1 and 4 (69.2%, 64.7%) but, there were commonly no angulation in Type 3 (68.4%) (p<0.001). The length of the infraorbital canal and the distances from the infraorbital foramen to the infraorbital rim and piriform aperture was measured as the longest in Type 3 and the smallest in Type 1 (p<0.001). The sagittal infraorbital foramen entry angles were detected significantly smaller in Type 3 and larger in Type 1 than that in other types (p=0.003). The maxillary sinus septa and the Haller cell were observed in 28% and 16% of the images, respectively. CONCLUSION: Precise knowledge of the infraorbital canal corpus types and relationship with the morphometry allow surgeons to choose an appropriate surgical approach to avoid iatrogenic infraorbital nerve injury.