|Year : 2016 | Volume
| Issue : 1 | Page : 37-40
Anatomy of maxillary sinus and its ostium: A radiological study using computed tomography
Anne D Souza1, KV Rajagopal2, Vrinda Hari Ankolekar1, Antony Sylvan D Souza1, Sushma R Kotian1
1 Department of Anatomy, Kasturba Medical College, Manipal University, Manipal, Karnataka, India
2 Department of Radiodiagnosis, Kasturba Medical College, Manipal University, Manipal, Karnataka, India
|Date of Web Publication||22-Dec-2015|
Sushma R Kotian
Department of Anatomy, Kasturba Medical College, Manipal University, Manipal - 576 104, Karnataka
Source of Support: None, Conflict of Interest: None
Background: Interventions involving the middle meatus are commonly performed because the majority of the paranasal sinuses open into the osteomeatal complex. Therefore, the aim of the present study was to locate the level of maxillary sinus ostium (MSO), to measure the distances between MSO and different anatomical landmarks, to measure the different dimensions of maxillary sinus and to compare the morphology of maxillary sinus between the right and the left sides. Materials and Methods: The study involved 50 computed tomography (CT) images of normal paranasal sinus anatomy in coronal and sagittal planes from the Department of Radiodiagnosis. The location of the sinus ostium (upper, middle, or lower third) was observed. Perpendicular distance from the sinus ostium to the lower border of inferior turbinate and hard palate were measured. The maximum vertical, transverse, and antero-posterior diameters of the maxillary sinus were measured. Results: Of 50 CT images, the MSO was located in the upper third in 40 cases while in 10 it was located in the middle third. The most common location of MSO was in the upper third. The dimensions of the maxillary sinus indicated bilateral symmetry. Conclusion: The dimensions of the maxillary sinus indicated bilateral symmetry, and there were no significant gender differences when compared. However, the distances of the MSO from the major anatomical landmarks were significantly different between males and females which are seldom reported earlier. This knowledge about the variations in the lateral wall of the nasal cavity is crucial during the endoscopic interventions and for functional endoscopic sinus surgeries.
Keywords: Computed tomography, dimensions, maxillary sinus, ostium
|How to cite this article:|
Souza AD, Rajagopal K V, Ankolekar VH, Souza AD, Kotian SR. Anatomy of maxillary sinus and its ostium: A radiological study using computed tomography. CHRISMED J Health Res 2016;3:37-40
|How to cite this URL:|
Souza AD, Rajagopal K V, Ankolekar VH, Souza AD, Kotian SR. Anatomy of maxillary sinus and its ostium: A radiological study using computed tomography. CHRISMED J Health Res [serial online] 2016 [cited 2019 Sep 19];3:37-40. Available from: http://www.cjhr.org/text.asp?2016/3/1/37/172397
| Introduction|| |
The maxillary sinus is a pyramid shaped pneumatic space with its base adjacent to the nasal wall and apex pointing to the zygoma. It is the largest bilateral air sinus located in the body of the maxilla and opens in the middle nasal meatus of the nasal cavity with single or multiple openings. The maxillary sinus varies greatly in size, shape, and position not only in different individuals but also in different sides of the same individual. Thus, dimensions of the maxillary sinus vary considerably among the gender, ethnic groups, etc. Considering the anatomical variability related to the maxillary sinus, its intimate relation to the maxillary posterior teeth, the implications that pneumatization may possess, assessment of the dimensions of the maxillary sinus is of utmost usefulness.
With evolution, man has attained an erect posture, which is further associated with multiple modifications in the body pattern. Higher location of the maxillary sinus ostium (MSO) is one among them. Consequently drainage was no longer due to gravity. This factor along with the impendence to mucociliary action of the lining mucosa is the leading cause in the obstruction of the ostium which opens at the hiatus semilunaris. Maxillary sinusitis is, therefore, the demerited gift of erect posture. The ostium of the maxillary sinus is on the highest part of the medial wall of the sinus and, is therefore, poorly placed from the point of view of free drainage; in addition, it does not open directly into the nasal fossa but into the narrow ethmoidal infundibulum, inflammation of which can further interfere with drainage.
Further, the topography of the maxillary sinus is also variable due to the range of anatomical bony structures forming this cavity. These are important in otolaryngological or maxillofacial surgical practice., An atypical structure of the maxillary sinus causes difficulties during operation on this cavity  or sinus floor augmentation procedures.,, Various cadaveric and radiological studies have been carried out to identify the variations of the landmarks in nasal anatomy but the morphometric measurements vary considerably in cadaveric and CT studies.,, However, studies using CT scan have shown to provide a more accurate data. In addition, there is a dearth for studies that have a holistic approach to the maxillary sinus. Therefore, the present study is an attempt to explore the anatomy of maxillary sinus, that is, its dimensions, position of MSO, and relationship of the MSO with the major anatomical landmarks which would be useful in endoscopic maxillary sinus approaches.
| Materials and Methods|| |
The present observational study was carried out using 50 64/16 slice brilliance CT images, (Philips) of adults with normal paranasal sinus anatomy in coronal and sagittal planes procured from the Department of Radiodiagnosis during the year 2014. Ethical clearance was obtained from the Institutional Ethics Committee. The CT images with paranasal sinus pathology or with previous surgeries were excluded from the study. The parameters were measured using Meddiff Pacs System (Meddiff Technologies Pvt. Ltd.).
The maximum vertical, transverse, and antero-posterior diameters of the maxillary sinus were measured. Location of the sinus ostium was observed and was classified as upper, middle, or lower third. Perpendicular distance from the sinus ostium to the lower border of inferior turbinate (IT) and hard palate (HP) were also measured. The measured parameters are shown in [Figure 1].
|Figure 1: The computed tomography images showing the parameters measured. MSO: Maxillary sinus ostium, IT: Inferior turbinate, a: MSO to inferior turbinate, b: MSO to hard palate, c: Transverse diameter, d: Vertical diameter, e: Antero-posterior diameter|
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SPSS version 16 (IBM Corporation) was used for the statistical analysis. Kolmogorov–Smirnov test was applied to check the uniform distribution of the data and Levene's test for their homogeneity. The mean parameters were compared between males and females using unpaired t-test as well as between the right and left sides using paired t-test.
| Results|| |
CT images of 50 adults were included in the study, of which 34 were males and 16 females. Their age group ranged from 20 to 60 years. The mean and standard deviations of the dimensions of maxillary sinus and the distances measured from the ostium to important anatomical landmarks are shown in [Table 1].
|Table 1: Mean and standard deviations of dimensions of measured parameters|
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Of 50 CT images, the MSO was located in the upper third in 40 cases while in 10 it was located in the middle third [Figure 2]. No maxillary sinus was observed with the ostium located in lower third.
|Figure 2: Computed tomography scan image in coronal view showing the maxillary sinus ostium at the middle third on right side and at upper third on left side|
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Unpaired t-test was applied to compare the means between males and females. There was a significant difference observed between the distances measured from MSO to IT and HP (P < 0.05). However, the dimensions of maxillary sinus did not vary with the gender.
Paired t-test was applied to compare the means between right and left sides. There was no statistical significant difference found between the means of two sides indicating the bilateral symmetry of the parameters.
| Discussion|| |
The maxillary sinuses are the only sizable sinuses present at birth. At birth, they measure about 8 mm × 4 mm, and are situated with their longer dimension directed anteriorly and posteriorly. The maxillary sinuses appear at the end of the second embryonic month. They extend to the roof of the permanent teeth when deciduous teeth fall off. According to Jovanic, the maxillary sinuses reach their mature sizes at the age of about 20 years, when the permanent teeth fully develop. The size of the sinus is insignificant until the eruption of permanent dentition. The average dimensions of the adult sinus are 2.5–3.5 cm wide, 3.6–4.5 cm tall, and 3.8–4.5 cm deep. It has an estimated volume of approximately 12–15 cm., During adulthood, their shapes and sizes change, especially due to loss of teeth. It has been reported that genetic diseases, postinfections, and environmental factors can also affect the sizes of maxillary sinuses.
Maxillary sinus anatomy is complex and rather variable from person to person. Significant differences in structure between the two sides may also exist in the same person., Contrary to that, in the present study no statistical significant difference was found between two sides indicating the bilateral symmetry of dimensions.
The dimensions of the maxillary sinus could be used for determination of gender. CT measurements of maxillary sinuses, that is, the length, the width, and the height may be useful to support gender determination in forensic medicine; however, with a relatively low-accuracy rate (<70%). However, in the present study, the dimensions of maxillary sinus did not vary with the gender. Therefore, dimensions of maxillary sinus together with other bones can be used for gender determination when the whole skeleton is not available for more accurate results.
A detailed knowledge of the anatomy of the sinuses is critical in performing procedures such as functional endoscopic sinus surgery.,
The incidence of the location of MSO has been recorded by various authors who conducted studies on cadavers and endoscopically. According to them, the MSO may be found at any point along the course of the ethmoid infundibulum. In a study by Prasanna andMamatha, the ostium of the maxillary sinus was more commonly found to open into the posterior third of the infundibulum in 21 (52.5%) specimens, while it opened into the middle third in 11 (27.5%), anterior third in 4 (10%), and was absent in 4 (10%) specimens. Van Alyea reported similar observations and found the opening of maxillary ostium into the anterior third of the uncinated groove in 9 (5.53%), to the middle third in 18 (11.04%), to the posterior third in 117 (71.8%), and to the extreme posterior tip of the groove in 19 (11.65%) cases. Rosenberger has stated that maxillary ostium opens into the posterior third in 70% cases, thus, making the posterior third of the uncinate groove as the most common position.
However, limited literature is available on the variable position of the MSO in CT studies. In the present study, coronal sections of the CT images were examined which classified the variable positions of the MSO as upper third, middle third, and lower third. The most common position of the MSO was at the upper third, which was similar to the findings of May et al.
Myerson et al., recognized that the ostium of the maxillary sinus is located immediately below the orbital floor, and thus, below the lamina papyracea in the posterior part of the infundibulum, and that perforating the lateral wall of the infundibulum superior to the ostium violates the orbit. Hence, the sinus surgeon must have a thorough knowledge of the relevant anatomic relationship to avoid injury to the orbit. Blind probing or nibbling with the forceps may lead to higher incidence of orbital complications.
The present study agrees with the same and also stresses on the relationship of the MSO with the major anatomical landmarks, that is, the distance between the MSO and the IT which was approximately similar bilaterally. However, they vary significantly in case of males and females.
Balloon catheter dilation of the paranasal sinuses offers a unique opportunity to re-establish maxillary sinus ostial drainage without removing the uncinate process. Although the literature suggests a high success in gaining access to the maxillary sinus with a sinus guidewire, navigating the ethmoid fundibulum with a guidewire and successfully traversing the MSO while retaining the uncinate process can be challenging in certain cases. A thorough knowledge of the distance between the MSO and the important anatomical landmarks, therefore, becomes important. This study reveals specific anatomic information that is applicable to the technique of transnasal maxillary sinus balloon catheter dilation. The data collected allow surgeons to anticipate the direction in which a guidewire must be manipulated in order to correctly enter the maxillary ostium.
The anatomy of the maxillary ostia should be well understood by an endoscopic sinus surgeon in order to perform the middle meatal antrostomy.
| Conclusion|| |
The location of MSO and dimensions of maxillary sinus were noted and the distances were measured from the MSO to important surgical landmarks. The most common location of MSO was in the upper third. The dimensions of the maxillary sinus indicated bilateral symmetry and there were no significant gender differences when compared. However, the distances of the MSO from the major anatomical landmarks were significantly different between males and females which are seldom reported earlier. Variability in the morphology of the maxillary sinus has practical significance during surgical procedures conducted by maxillofacial surgeons or otolaryngologists. The knowledge about the variations in the lateral wall of the nasal cavity is also crucial during the endoscopic interventions and for functional endoscopic sinus surgeries.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
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