O R I G I N A L A R T I C L E
Location of the infraorbital foramen with reference to soft tissue
landmarks
Nurcan Ercikti1• Nihal Apaydin2•Yalcin Kirici3
Received: 4 January 2016 / Accepted: 28 April 2016 / Published online: 4 May 2016 Ó Springer-Verlag France 2016
Abstract
Purpose The location of the infraorbital foramen and its variations are important during periorbital, dental, plastic, and oromaxillofacial surgeries. The aim of this study is to document the most practical anatomical soft tissue land-marks for defining the location of infraorbital foramen and infraorbital nerve for effective nerve blockade and to decrease its risk of injury during periorbital surgeries. Methods Forty sides from 20 adult fixed cadavers were used for this study. The position of the infraorbital nerve was determined in reference to the lateral edge of the ala of the nose, medial and lateral palpebral commissures. All these three soft tissue landmarks were then connected to each other forming a triangular shaped region.
Results In 75 % of the cases the infraorbital foramen was located on the line which is connecting the lateral palpebral commissure to the ala of the nose. The closest distance of infraorbital foramen to the inferior orbital margin and to facial midline was also measured. The infraorbital foramen was located outside the previously defined triangular region in 20 % and inside the triangle in 5 %. The closest mean distance between the infraorbital foramen and the infraor-bital margin was measured as 8.8 ± 1.0 mm and the dis-tance between the medial wall of the infraorbital foramen and the facial midline was measured as 30.3 ± 2.7 mm.
Conclusion The triangular region and the soft tissue landmarks we offered in this study may facilitate prediction of the locations of the infraorbital foramen thus, the infraorbital nerve.
Keywords Infraorbital foramen Infraorbital nerve Oromaxillofacial surgery Infraorbital nerve blockage
Introduction
The location of the infraorbital foramen (IOF) and its variations are important during periorbital surgery. The infraorbital nerve emerges from the IOF, and it is blocked at the foramen to induce local anesthesia during dental, plastic, and oromaxillofacial surgery. Thus, precise knowledge of the location of these foramen and nerve is necessary to avoid neurovascular injury during surgery or any interventions done at that region [2,5,6,10].
The location of the IOF has frequently been determined in numerous studies examining the skulls devoid of soft tissue structures [1, 3,4, 8, 9]. However, the location of IOF has not been well defined on cadavers according to standard and easily visible anatomical landmarks. The aim of this study, therefore, is to document the most practical anatomical landmarks for defining the location of infraor-bital nerve for effective nerve blockade and to decrease its risk of injury during periorbital surgeries.
Materials and methods
Forty sides from 20 adult fixed cadavers were used for this study. Of these, ten were male and ten were female and ranged in age from 40 to 72 years, with a mean of 61 years & Nihal Apaydin
napaydin@gmail.com
1 Department of Anatomy, Gulhane Military Medical School,
Ankara, Turkey
2 Department of Anatomy, Ankara University Faculty of
Medicine, 06100 Sihhiye, Ankara, Turkey
3 Department of Anatomy, Ufuk University Faculty of
Medicine, Ankara, Turkey DOI 10.1007/s00276-016-1683-0
at death. None of the cadavers showed any gross pathology or signs of surgical procedures in the examined area. Each cadaver was placed prone and the skin and the subcuta-neous tissue over the maxilla were cut and removed com-pletely. The infraorbital nerve was exposed at the IOF and its position was determined in reference to the lateral edge of the AN, medial and lateral palpebral commissures. All these three soft tissue landmarks were then connected to each other forming a triangular shaped region for stan-dardizing the location of the infraorbital nerve (Fig.1). The distances of the IOF to these soft tissue landmarks were measured and the position of the foramen was documented in reference to this triangle by trusting following measurements:
1. Distance between lateral palpebral commissure (LPC) and the ala of the nose (AN).
2. Distance between IOF and LPC. 3. Distance between the IOF and AN.
The closest mean distance of the IOF to the infraorbital margin was also measured to for the location of the IOF in relation to the inferior orbital rim. The distance between
the medial wall of the IOF and the facial midline (FM) was measured to point the position of the IOF to FM (Fig.2). All measurements were made using digital calipers (Vernier LCD Digital Caliper Measuring, USA with an accuracy of 0.01 mm). To correct for individual examiner variability, each specimen was examined by two members of the team (NI, YK). Each observer made single inde-pendent measurements and the mean of all measurements was recorded. Statistical analysis was performed using Student’s t test. Mann–Whitney U test was performed for comparisons between the side, gender and age of the cadavers. P B 0.05 was considered as statistically significant.
Results
The IOF was present in all cases. Only in one of cadavers there was a double IOF on the right side (Fig. 3).
The mean distance between LPC and the AN was measured as 54.7 ± 3.1 mm. The mean distance between the IOF and LPC was measured as 30.5 ± 3.6 mm and the mean distance between the IOF and AN as 24.7 ± 4.0 mm. The closest mean distance of the IOF to the infraorbital margin was measured as 8.8 ± 1.0 mm. The distance between the medial wall of the IOF and the FM was measured 30.3 ± 2.7 mm.
Fig. 1 The soft tissue landmarks (lateral edge of the ala of the nose, medial and lateral palpebral commissures) and the triangular shaped region formed by connecting all these three soft tissue landmarks were shown. Arrow indicates the infraorbital foramen which is located on the line connecting the lateral palpebral commissure to the ala of the nose in this case
Fig. 2 The distances between the FM (facial midline) and the infraorbital foramen (horizontal arrow) and the closest distance between the infraorbital margin and the infraorbital foramen (vertical arrow)
The majority of the infraorbital foramens (75 %) were found to be located on the line which is connecting the LPC to the AN. The IOF was located outside the previously defined triangular region in 20 % and inside the triangle in 5 %. In the case presenting double infraorbital foramens one foramen was located on the LPC-AN line and the other inside the triangle.
All the results were given in Table1. There were no statistically significant differences in regards to age, gen-der, or side of the specimens (P [ 0.05).
Discussion
The location of the infraorbital nerve is important for local anesthetic procedures and also its foramen is an important anatomic landmark for the oral and maxillofacial surgeries. In our study we aimed to define practical anatomical soft tissue landmarks for to locate the position of the IOF, thus the infraorbital nerve easily to ensure safety during surg-eries directed to superior or anterior wall of the maxilla, such as rhinoplasty, tumor surgeries or Le-Fort type 1 osteotomies. Additionally locating the infraorbital nerve and its foramen will also be useful to direct the anesthetic
needle for selective infraorbital nerve blocks during anes-thesia. By precisely directing to the infraorbital nerve, the need for anesthetic agent will decrease thus, the compli-cations related with the anesthetic will decrease.
There is a large variation in determining the location of the infraorbital nerve and its foramen in the literature with regard to the some anatomic landmarks [1–4,9,10]. For example, Aziz et al. have measured the distance of IOF to the infraorbital margin on 47 cadaveric heads and found that distance as 8.5 ± 2.2 mm [2]. Gupta studied the location of the IOF on skulls by defining skeletal land-marks and found the mean distance of the IOF from the inferior orbital margin was about 7.0 ± 1.6 mm and from the zygomatico-maxillary suture it was 10.8 mm. The other landmark which was chosen by Gupta was the facial midline which is drawn through the bony septum of the nose [4]. In our study we found the closest mean distance of IOF to infraorbital margin as 8.78 mm. However, we believe that the infraorbital margin is not a reliable land-mark to locate the exact position of the IOF because it is a long curved line and the location of the IOF can be any-where in relation to that line. Additionally, palpating the zygomatico-maxillary suture is nearly impossible superfi-cially. It can be only exposed on dry skulls and we suggest that it cannot be used as a practical landmark clinically. In addition to this, the distance between the inferior margin of the orbit and the IOF varies between studies and among different ethnic groups [2].
Aziz et al. also suggested the FM as a reference to locate the IOF and measured this distance as 27.7 ± 4.3 mm in males and 26.2 ± 3.2 mm in females [2]. Gupta found the distance of the IOF to FM as 28.5 ± 6 2.6 mm [4]. This distance was found as 30.3 ± 2.7 mm in our study. We also suggest that the FM is not a reliable landmark line since the position of the IOF can be anywhere in relation to this line. So we suggest that defining more standard land-marks which can be easily located by palpation of inspection will be more practical to find the exact position of the IOF.
Fig. 3 A case presenting double infraorbital foramina and double infraorbital nerves on the right side
Table 1 Certain distances used for location of the infraorbital foramen LPC-AN (mean ± SD mm) IOF-LPC (mean ± SD mm) IOF-AN (mean ± SD mm) IOF-IOM (mean ± SD mm) IOF-FM (mean ± SD mm) Female (n = 10) Right (n = 5) 52.3 ± 3.7 29.4 ± 3.6 24.2 ± 3.7 7.8 ± 1.0 27.5 ± 2.7 Left (n = 5) 52.5 ± 3.2 29.4 ± 2.8 23.5 ± 4.4 7.9 ± 0.8 31.2 ± 3.1 Male (n = 10) Right (n = 5) 57.5 ± 2.6 30.2 ± 3.9 26.7 ± 3.8 9.6 ± 1.2 32.0 ± 2.0 Left (n = 5) 56.7 ± 2.8 32.8 ± 4.2 24.3 ± 4.2 9.8 ± 0.9 30.5 ± 2.9 Total (n = 20) 54.7 ± 3.1 30.5 ± 3.6 24.7 ± 4.0 8.8 ± 1.0 30.3 ± 2.7 LPC lateral palpebral commissure, AN ala of the nose, IOF infraorbital foramen, IOM inferior orbital margin, FM facial midline
Similarly, Singh has studied the position of the IOF in relation to bony landmarks such as infraorbital margin and piriform aperture [9]. Chrcanovic et al. has also suggested use of infraorbital margin, FM, piriform aperture and zygomatico-maxillary suture as bony landmarks [3]. Agthong et al. suggested one additional landmark which was anterior nasal spine in addition to infraorbital margin and FM [1]. Rai et al. included frontomaxillary suture to these bony landmarks [8]. Actually all these authors have only examined dry skulls not cadavers. However, we suggest that bony landmarks such as piriform aperture as suggested by Singh and Chrcanovic et al. or zygomatico-maxillary suture as suggested by Gupta and Chrcanovic et al. or frontomaxillary suture as suggested by Rai et al. are not practical landmarks to use as landmarks during surgeries [3,4,8,9]. These landmarks are not palpable and it is also difficult to relate the position of the foramen to these bony landmarks.
Soft tissue landmarks or palpable bony landmarks are more practical to use as a guide during surgeries. For example, Song et al. have suggested the AN and the mouth corners (cheilions) as soft tissue landmarks fort o find the location of the IOF [10]. They made their measurements on photographs of the cadavers and found the distance between the AN and the IOF as 15.9 ± 2.8 mm [10]. This distance was found as 24.7 ± 4.0 mm in our study. The difference may come from the number of the specimens examined and the ethnics of the specimens. Song et al. suggested that the locations of the infraorbital foramina were variable in rela-tion to the cheilions, being in the same plane, medial to, or lateral to that of the cheilions [10]. They found that only in approximately 50 % of cases the location were similar. They concluded that since the cheilions lie far from the infraor-bital foramina and thus do not constitute better landmarks than the alae of the nos [10]. Takashi et al. examined the horizontal location of the IOF in relation to the ala nasi in 56 orbits of 28 Japanese cadavers and found out this distance as 4.9 mm, with no significant difference between genders [11]. The authors have suggested that the ala nasi can be used as a versatile reference point to identify the IOF during surgery since the horizontal distance is irrespective of gen-der and easy to identify [11]. We also suggest that since the AN is a clearly visible and palpable landmark on the face, it can be used as a reliable landmark. But defining only one soft tissue landmark is not reliable to find the exact location of the foramen.
Liu et al. had suggested determining the locations of the supraorbital foramen (SOF) and the IOF relative medial and lateral cantus [6]. We suggest trusting other landmarks as well such as medial and lateral palpebral commissures in addition to the AN. And the triangular region which was defined in our study can be used to predict the position of the IOF before initiating surgery. In 80 % of our cases the
IOF was located either on the lateral margin or inside the triangle which was formed by the lines connecting there soft tissue points namely; AN, lateral and medial palpebral commissures.
In a recent study by Michalek et al. [7] the infraorbital nerve block was tested on skull models by using ultra-sound-guided simulation. It was suggested that ultrasound guidance may help to reduce the potential of puncture of neurovascular structures during needle placement and thus decreasing risk of hematoma formation. The results of our study suggested us that LPC and the line connecting the LPC to AN can also be used as reliable landmarks. In our study, the mean LPC-AN distance was measured as 54.7 ± 3.1 mm and the mean distance between the IOF and LPC was measured as 30.5 ± 3.6 mm. These distances were not measured previously by any authors so we cannot compare our results with previous ones. In 5 % of our cases the IOF was located medial to LPC-AN being previously defined triangle and in 75 % of cases the IOF was located on LPC-AN line. It can be also concluded that the IOF was located at the lower half of the LPC-AN line. Considering the spread of the anesthetic agent, an anesthetic injected on the lower half of the IOF-AN line would successfully block the infraorbital nerve in majority of the patients. Keeping this location in mind before any operation directed to maxilla-facial region may also prevent nerve injury. But it should be also kept in mind that the foramen can be double, so the nerve. Aziz et al. previously reported the presence of double foramen as 15 % [2]. In our study the incidence of double foramen was 2.5 %.
In conclusion, we suggest that the landmarks and the triangle region we offered in this study may facilitate prediction of the locations of the IOF thus, the infraorbital nerve. Knowledge of this exact position in relation to easily visible landmarks may decrease the risk of injury during surgical approaches directed to this region and might serve as a guide during local anesthetic interventions. We also suggest introduction of ultrasound guidance techniques as recommended by Michalek et al. [7] will reduce the risk of neurovascular injury and increase the success of the block. Compliance with ethical standards
Conflict of interest The authors declare that there is no conflict of interest.
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