Morphometric Study Of Infraorbital Foramen In Dry Human Skulls

Background & Objectives:To study the most precise location, shape and direction of infraorbital foramen in dry human skulls, in relation to Infraorbital Margin, Piriform Aperture(PA) and Upper Alveolar Margin(AM). Method: A total of one hundred dry human skulls of unknown gender were measured using digital calliper with Infraorbital Margin, Piriform Margin and Alveolar Margin as reference points. The location, shape, size, direction and number of accessory foramina were observed. Results: The mean distance between the Infraorbital Margin(IOM) and Infraorbital foramen(IOF) was 7.82mm. There was a statically significant difference on right and left sides. The mean distance between the IOF and the piriform aperture(PA) was 16.01mm. The overall vertical diameter of the IOF was 3.23±0.98mm (right) and 3.25±1.03mm (left ). The overall horizontal diameter of IOF was 3±0.76mm(right) and 3.28±0.99mm ( left).The majority of IOF were directed inferiomedially on both the right (51%) and left (50%) side. There was a superiomedially directed IOF in 1% of skulls, which was not mentioned in the previous literatures. Accessory foramina were found in 20% skulls. Interpretation & Conclusion: Infraorbital foramen is located close to important anatomical structures like orbit, nose, oromaxillary sinuses and upper teeth. The knowledge of anatomical characteristics of the location ,dimension, shapes, directions and number of accessory foramina have clinical implications in the infraorbital nerve block. This information should be kept in mind during local anaesthetic planning for surgeries in the field of Dentistry, ENT, Anaesthesia, Ophthalmology and Surgery. [Bharti B et al NJIRM 2013; 4(3) : 43-49] KEY Words: Infraorbital foramen, Infraorbital margin , Piriform aperture ,Alveolar margin. Author for correspondence: Dr. Amrita Bharti, Department of Anatomy, Bharati Vidyapeeth Deemed University Medical College, Pune – 411043. email: [email protected]. Introduction: Facial skeleton on the anterior view of the human skull is formed by a frontal bone in the upper part, two maxillae in the central part and a mandible in the lower part. The central part of the face is occupied by two maxillae separated by the anterior nasal aperture. Each maxilla contributes to the upper jaw, floor of the orbital cavity, the lateral wall of the nose, the floor of the nasal aperture and the bone of the cheek. Medially the maxilla forms the nasal notch. The prominent anterior nasal spine, which surmounts intermaxillary suture at the lower margin of the anterior nasal aperture, is palpable in the nasal septum. The infraorbital foramen, which transmits the infraorbital vessels and nerve, lies about 1 cm below the infraorbital margin1. It is a continuation of infraorbital canal, which is present on the orbital surface of the maxilla. This canal opens just below the margin of the orbit. It transmits the infraorbital nerves and infraorbital artery, both of which enter this canal at the infraorbital groove, courses through the maxillary sinus and exits via infraorbital foramen. The infraorbital nerve is a terminal branch of maxillary nerve. It divides into three groups of branchesthe palpabral, the nasal and the superior labial. The palpabral branches supply the skin in the lower eyelid. The nasal branches supply the skin of the side of the nose and of the movable part of the nasal septum. The superior labial branches supply the skin of the anterior part of the cheek and the upper lip .The teeth in the upper jaw are supplied by the three superior alveolar (dental) nerves. The posterior superior alveolar nerve arises from maxillary nerve. The middle superior and anterior superior alveolar nerves arise from infraorbital nerve. The middle superior nerve runs in the lateral wall of maxillary sinus and ends in small branches forming superior dental nerve plexus which supply the upper premolar tooth. The anterior superior alveolar nerve traverses the anterior wall of maxillary sinus, passes towards the nose, divides into branches supplying upper incisors and canine teeth. The infraorbital artery arises from third part of the maxillary artery. It emerges from the infraorbital foramen on the face to supply the lower eyelid, Morphometric Study Of Infraorbital Foramen In Dry Human Skulls NJIRM 2013; Vol. 4(3).MayJune eISSN: 0975-9840 pISSN: 2230 9969 44 lateral aspect of the nose and the upper lip. The upper jaw is supplied by dental arteries which are posterior, middle and anterior superior arteries. The middle and anterior superior alveolar arteries are branches of infraorbital artery. The anterior superior alveolar artery supplies the upper incisors, canine and mucous membrane in the maxillary sinus. It follows the rim of anterior nasal aperture and ends near nasal septum giving its terminal branches. The infraorbital foramen is located near important anatomical structures like orbit, nose and oral cavity. It finds clinical significance because of its neurovascular contents. The infraorbital nerve block is the local analgesic technique of choice for the regional anaesthesia of the face. The procedure offers several advantages over local tissue infiltration. The infraorbital nerve block achieves anaesthesia with a smaller amount of anaesthetic drug than is required for local infiltration. It can also provide anaesthesia without causing tissue distortion. The infraorbital nerve block is a convenient alternative for situations such as facial lacerations in which tissue distortion would be unacceptable. The infraorbital nerve supplies sensory innervations to the lower eyelid, the side of nose and the upper lip. This nerve is a prime candidate for a regional nerve block on account of this large area of innervation. An infraorbital nerve block is essential during surgical procedures around the orbit, nose and buccal regions. Therefore the location of the infraorbital foramen assumes great importance. This study was conducted for morphometric measurements of the infraorbital foramen in 100 dry human skulls, irrespective of their gender. The aim of this study was to find out the incidence of variations in number, location, shape, dimension and direction of the infraorbital foramen on both the sides of the same skull. The findings of this study were also compared with the findings of other authors. Material and Methods: One hundred adult dry macerated human skulls of unknown gender were obtained from department of anatomy of various medical colleges in Maharashtra, with prior permission of the concerned authorities. Both sides of each skull were assessed by direct inspection. The location, dimension and direction of infraorbital foramen (IOF) were observed. Skulls with fractures in the supraorbital margin, piriform aperture, infraorbital foramen, infraorbital margin and at the upper alveolar margin , adult skulls in which one side is destroyed, edentulous skulls, foetal and child skulls were excluded from this study. All the measurements were taken on both the sides with the help of digital vernier caliper and noted in millimetre by a single observer. The distances from the upper and lower margins of the infraorbital foramen to the supraorbital margin (lateral to supraorbital notch) and infraorbital margin (where zygomaticomaxillary suture intersects the infraorbital margin ) were measured. The distances from the medial margin of the infraorbital foramen to the piriform aperture along the transverse plane that passes through the centre of the infraorbital foramen were measured. The vertical distances from the lower margin of the infraorbital foramen to the upper alveolar margin were measured. The tooth to which this vertical line corresponds was also noted. Vertical and horizontal dimensions of the foramen were also taken with double tipped compass. The compass opening was transferred to calliper and measuring scales to measure the dimensions.The direction of the infraorbital foramen was determined by using a probe in the direction of opening of IOF. Result: The sample size is of 100 skulls in each group. Various mean distances were documented and compared on right and left sides using Z-test. Statistical significance of the differences in various parameters on right and left side were established on the basis of p value. The level of significance was 5%.The range for various measurements were calculated. Standard deviation in various measurements were calculated. The mean distance of upper margin of infraorbital foramen to supraorbital notch on right side is 38.21 mm (SD ±3.91) and on left side is 38.55 mm (SD ±4.66). This distance lies in the range of 17.59 mm (minimum) and 48.00 mm (maximum). Statistically there is no significant difference between mean distance on Morphometric Study Of Infraorbital Foramen In Dry Human Skulls NJIRM 2013; Vol. 4(3).MayJune eISSN: 0975-9840 pISSN: 2230 9969 45 right and left sides of the skull, the calculated pvalue = 0.569 > 0.025 (Standard p-value). The mean values of distance of lower margin of infraorbital foramen to supraorbital notch on right side is 39.46mm (SD ±5.93) and on left side is 40.49mm (SD ±5.92). This distance ranges from 16.53mm (Minimum) to 48.87 mm (Maximum) .The overall mean distance between the infraorbital foramen and the supraorbital notch is 39.18 mm . The mean values of distance of upper margin of infraorbital foramen to infraorbital margin on right side is 6.54 mm (SD ±1.28) on left side is 7.02 mm (SD ±1.42) .The distance ranges from 4.17mm (minimum) to 10.21mm (maximum) .The mean distance of upper margin of infraorbital foramen from infraorbital margin on the right side differ significantly (0.48mm ±0.14) from that on the left side of the skulls with a calculated p-value = 0.014 < 0.025. The mean values of distance of lower margin of infraorbital foramen to infraorbital margin on right side is 8.62mm (SD ±1.23) and on left side is 9.11mm (SD ±1.70).This distance lies in the range of 5.94 mm minimum to 13.7 mm (maximum).Statistically there is a significant difference (0.49mm±0.47) between mean distance of IOM to lower margin of IOF on right and left sides of skull (calculated p-value = 0.021 <0.025). The overall mean distance between the infraorbital foramen and the infraorbital margin is 7.82mm. The mean values of distance from medial margin of infraorbital foramen to piriform aperture on right side is 16.20mm (SD ±2.72) and on left side is 15.82mm (SD ±2.75). The overall combined mean distance between IOF and PA is 16.01 mm (SD±2.73), with a range of 9.56 mm(min) and 24.24 mm (max). Statistically there is no significant difference (0.37mm±0.02) between mean transverse distance of IOF from PA on right and left sides of skull (calculated p-value = 0.33 > 0.025). The mean vertical distance from lower margin of infraorbital foramen to upper alveolar margin on right side is 28.93 mm (SD ±4.11) and on left side is 28.42 mm (SD ±4.43). The overall combined mean vertical distance between lower margin of IOF and upper alveolar margin 28.68 mm (SD±4.27). This ranges from 16.99 mm (min) to 42.32 mm (max). Statistically, there is no significant difference (0.5mm±0.31) between lower margin of IOF and upper AM on right and left sides of the skull (calculated p-value = 0.392 > 0.025). The mean horizontal distance between medial and lateral margin of infraorbital foramen (H) on right side is 3.00 mm (SD ±0.76)and on left side is 3.28 mm (SD ±0.99). Statistically, there is a significant difference (0.28mm±0.23) between mean horizontal dimension of right and left sides of the skull (calculated p-value = 0.024 > 0.025).The mean combined horizontal distance between lateral and medial margins of IOF is 3.14 mm (SD±0.89).The range of this horizontal distance is 0.55 mm (min) to 5.48 mm (max). The mean vertical distance between upper and lower margins of infraorbital foramen (V) on right side is 3.23mm (SD ±0.98) and on left side is 3.25mm (SD ±1.03).Statistically, there is a significant difference (0.02mm±0.05) between mean vertical dimension of IOF on right and left sides of the skull (p-value = 0.896 > 0.025).The overall combined mean vertical dimension is 3.24mm (SD±1.00), with a range of 0.96 mm (min) to 5.71 mm (max). Four different directions of openings of the infraorbital foramen (Photograph No.3) were observed.They were: 1) Inferiomedially directed foramen in 51% skulls on right side and 50% skulls on left side of the same skull. 2) Inferiorly directed foramenin 22% skulls on right side and 22% skulls on left side of the same skull. 3) Medially directed foramen in 26% skulls on right side and in 27% skulls on left side of the same skull. 4) Superiomedially directed foramen (Photograph No.2, 3) – in 1% skull on right side and in 1% skull on left side of the same skull. There is one skull showing openings of infraorbital foramen on right side being inferiomedially and on left side being medially (Photograph no.4). There is no such variant finding reported in the previous literatures. Statistically there is no significant difference in the Morphometric Study Of Infraorbital Foramen In Dry Human Skulls NJIRM 2013; Vol. 4(3).MayJune eISSN: 0975-9840 pISSN: 2230 9969 46 direction of opening of infraorbital foramen on the right and left side of the same skull. Photograph No.1 IOF – Infraorbital foramen, IOM-Infraorbital margin, PA-Piriform aperture, AM-Alveolar margin(upper), 1-Distance between IOM and IOF, 2-Transverse Distance between IOFand PA , 3-Vertical Distance between IOF and upper AM.