Clinical Anatomy 28:753–760 (2015)
ORIGINAL COMMUNICATION
Anatomical Study of the Infraorbital Foramen: A Basis for Successful Infraorbital Nerve Block ANJALI AGGARWAL,1* HARJEET KAUR,1 TULIKA GUPTA,1 R. SHANE TUBBS,2 DAISY SAHNI,1 Y.K. BATRA,3 AND RAKESH V. SONDEKOPPAM4 1
Department of Anatomy, Post Graduate Institute of Medical Education and Research, Chandigarh, India 2 Pediatric Neurosurgery, Children’s Hospital, Birmingham, Alabama 3 Department of Anaesthesia, Post Graduate Institute of Medical Education and Research, Chandigarh, India 4 Department of Anesthesia and Perioperative Medicine, London Health Sciences Centre, London, United Kingdom
Detailed knowledge of variations of the infraorbital foramen (IOF) and the establishment of a constant reference point for needle insertion are important for safe and successful regional block and for avoiding iatrogenic injury to the nerve during surgery in the midfacial region. Infraorbital foramina from 133 sides of 67 dry intact adult skulls of undetermined gender were examined for variations in shape, number, location in relation to bony landmarks, and relationship to the maxillary teeth. The angles of needle insertion in the sagittal and Frankfurt planes were determined. The infraorbital foramina were located at an average distance of 6.33 6 1.39 mm below the infraorbital margin, 25.69 6 2.37 mm from the median plane, 15.19 6 1.70 mm from the lateral margin of the piriform aperture, and 28.41 6 2.82 mm above the maxillary alveolar border. The average angles of needle insertion through the IOF with the sagittal and Frankfurt planes were 21.148 6 10.108 and 31.798 6 7.688, respectively. Multiple foramina were found in 21% of the hemi-skulls. The foramen was less than 2 mm in size in 23.31% of the hemi-skulls. The position of the IOF with respect to the maxillary teeth varied from the interval between the canine and first premolar to the first molar, but in half of the specimens it lay in line with the second maxillary premolar tooth. The observations made in this study should be useful for planning infraorbital nerve block or surgery around the IOF. Clin. Anat. 28:753–760, 2015. VC 2015 Wiley Periodicals, Inc. Key words: infraorbital foramen; infraorbital nerve; radiofrequency ablation; infraorbital canal
INTRODUCTION Percutaneous radiofrequency ablation is emerging as a minimally invasive technique for curative and palliative treatment of pain from various sources. Infraorbital neuralgia is one such indication, which can be treated effectively by ablating a portion of the infraorbital nerve (ION) in the outpatient department (Rahman et al., 2009). Anesthetic blockade of the ION, which involves injection of a drug through the infraorbital foramen (IOF), is an alternative therapy for maxillary division neuralgia and is also used to provide analgesia and anesthesia for maxillofacial surgeries.
C V
2015 Wiley Periodicals, Inc.
The ION, a direct extension of the maxillary division of the trigeminal nerve, passes along the floor of the orbit in the infraorbital groove and eventually exits
*Correspondence to: Dr. Anjali Aggarwal, 123-c Type IV Flats, Sector 24 A, Chandigarh 160023, India. E-mail: [email protected] Received 23 January 2015; Revised 3 March 2015; Accepted 9 April 2015 Published online 28 June 2015 in Wiley Online (wileyonlinelibrary.com). DOI: 10.1002/ca.22558
Library
754
Aggarwal et al.
the orbit through the IOF and provides cutaneous innervation to the lower eyelid, the side of the nose, and the upper lip. The superior alveolar branch of the ION provides sensory innervation to the upper incisor, canine, and associated gingiva. Detailed knowledge of the IOF and the establishment of a constant reference point for needle insertion are important for accomplishing safe and successful regional block and to avoid iatrogenic injury to the nerve during surgery in the midfacial region (Kazkayasi et al., 2001). Owing to its anatomical variations, it can be difficult to identify the IOF, and the landmark-based approach can be challenging even for experienced clinicians. Despite many authors’ claims regarding inconsistency in the relationship of the IOF to the teeth, the maxillary teeth, particularly the second premolar, are still in practice used as a reference for intraoral ION blocking (Aziz et al., 2000; Kazkayasi et al., 2001; Apinhasmit et al., 2006). Few articles describing the angle of needle insertion into the IOF have been published (Lee et al., 2006; Rahman et al., 2009). We planned our study to provide a detailed account of the variations of the IOF and to determine its relationship to surrounding landmarks so as to facilitate the prediction of its location and the best angle for needle insertion.
MATERIALS AND METHODS The study material consisted of 133 halves of 67 dry intact adult skulls of Indian descent. The skulls belonged to persons with ages ranging from 20 to 60 years. Their gender records were not available. Institutional ethical committee approval was obtained for pursuing the study.
Gross Anatomical Observations The IOF was studied for shape, presence of any surrounding bony projection, accessory IOF, and relationship to the maxillary teeth.
Anatomical Measurements All linear measurements were taken with a Mitutoyo digital caliper of 0.02 mm precision (Fig. 1). i. The distance of the IOF from each of the following bony landmarks was measured: Shortest vertical distance of the upper margin of the IOF from the lower rim of the orbit (IOFIOM); Transverse distance of the medial margin of the IOF from the lateral margin of the piriform aperture (IOF-PA); Transverse distance of the medial margin of the IOF from the median plane of the skull (IOF-ML); Vertical distance of the lower margin of the IOF from the upper alveolar border (IOF-AB). ii. To estimate its size, the maximum transverse and vertical dimensions of the IOF were measured.
Fig. 1. Skull showing measured parameters. IOFIOM: Vertical distance between upper margin of infraorbital foramen and inferior orbital margin. IOF-AB: Vertical distance between lower margin of infraorbital foramen and maxillary alveolar border. IOF-ML: Horizontal distance between medial margin of infraorbital foramen and midline of skull. IOF-PA: Horizontal distance between medial margin of infraorbital foramen and lateral margin of piriform aperture. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
The Angle of Needle Insertion into the Infraorbital Canal The skull was positioned on the skull stand such that the Frankfurt plane paralleled the horizontal plane and the midline of the skull paralleled the sagittal plane (Fig. 2). A needle was introduced into the IOF. Photographs of the skull with the needle in place were taken in anteroposterior and lateral views using a digital SLR Canon Camera, EOS series, secured to a tripod stand at a fixed distance from the skull stand. The distance between the skull and camera was standardized. The photographs were transferred to the computer. In the anteroposterior view, the angle between the needle and a vertical line passing through the IOF and parallel to the midline of the skull was measured with the angle measurement tool in Corel Draw version 12. In the lateral view, the angle between the needle and the horizontal line intersecting it at the IOF was measured using the same tool.
Statistical Analysis All measurements were analyzed statistically using MS Office, 2007 Excel spread sheet (Microsoft Corp., Redmond, WA) and SPSS version 2007 (SPSS Inc., Chicago, IL). A paired Student’s t-test was used to establish the statistical relationship between measurements of the right and left sides. The Pearson’s correlation coefficient was calculated to assess associations among variables.
Infraorbital Foramen
755
Fig. 2. (a) Angle between needle passing through the infraorbital foramen and the vertical line passing through the IOF parallel to the sagittal plane. (b) Angle between needle passing through infraorbital foramen and horizontal line intersecting the needle at the IOF parallel to the Frankfurt plane. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
RESULTS
Size of Infraorbital Foramen
Multiplicity of Infraorbital Foramina
The average transverse diameter of the foramen was 2.72 6 0.95 mm (range, 1.03–5.49 mm). In 20.3% of cases, the IOF was like a vertical slit with a transverse diameter
ORIGINAL COMMUNICATION
Anatomical Study of the Infraorbital Foramen: A Basis for Successful Infraorbital Nerve Block ANJALI AGGARWAL,1* HARJEET KAUR,1 TULIKA GUPTA,1 R. SHANE TUBBS,2 DAISY SAHNI,1 Y.K. BATRA,3 AND RAKESH V. SONDEKOPPAM4 1
Department of Anatomy, Post Graduate Institute of Medical Education and Research, Chandigarh, India 2 Pediatric Neurosurgery, Children’s Hospital, Birmingham, Alabama 3 Department of Anaesthesia, Post Graduate Institute of Medical Education and Research, Chandigarh, India 4 Department of Anesthesia and Perioperative Medicine, London Health Sciences Centre, London, United Kingdom
Detailed knowledge of variations of the infraorbital foramen (IOF) and the establishment of a constant reference point for needle insertion are important for safe and successful regional block and for avoiding iatrogenic injury to the nerve during surgery in the midfacial region. Infraorbital foramina from 133 sides of 67 dry intact adult skulls of undetermined gender were examined for variations in shape, number, location in relation to bony landmarks, and relationship to the maxillary teeth. The angles of needle insertion in the sagittal and Frankfurt planes were determined. The infraorbital foramina were located at an average distance of 6.33 6 1.39 mm below the infraorbital margin, 25.69 6 2.37 mm from the median plane, 15.19 6 1.70 mm from the lateral margin of the piriform aperture, and 28.41 6 2.82 mm above the maxillary alveolar border. The average angles of needle insertion through the IOF with the sagittal and Frankfurt planes were 21.148 6 10.108 and 31.798 6 7.688, respectively. Multiple foramina were found in 21% of the hemi-skulls. The foramen was less than 2 mm in size in 23.31% of the hemi-skulls. The position of the IOF with respect to the maxillary teeth varied from the interval between the canine and first premolar to the first molar, but in half of the specimens it lay in line with the second maxillary premolar tooth. The observations made in this study should be useful for planning infraorbital nerve block or surgery around the IOF. Clin. Anat. 28:753–760, 2015. VC 2015 Wiley Periodicals, Inc. Key words: infraorbital foramen; infraorbital nerve; radiofrequency ablation; infraorbital canal
INTRODUCTION Percutaneous radiofrequency ablation is emerging as a minimally invasive technique for curative and palliative treatment of pain from various sources. Infraorbital neuralgia is one such indication, which can be treated effectively by ablating a portion of the infraorbital nerve (ION) in the outpatient department (Rahman et al., 2009). Anesthetic blockade of the ION, which involves injection of a drug through the infraorbital foramen (IOF), is an alternative therapy for maxillary division neuralgia and is also used to provide analgesia and anesthesia for maxillofacial surgeries.
C V
2015 Wiley Periodicals, Inc.
The ION, a direct extension of the maxillary division of the trigeminal nerve, passes along the floor of the orbit in the infraorbital groove and eventually exits
*Correspondence to: Dr. Anjali Aggarwal, 123-c Type IV Flats, Sector 24 A, Chandigarh 160023, India. E-mail: [email protected] Received 23 January 2015; Revised 3 March 2015; Accepted 9 April 2015 Published online 28 June 2015 in Wiley Online (wileyonlinelibrary.com). DOI: 10.1002/ca.22558
Library
754
Aggarwal et al.
the orbit through the IOF and provides cutaneous innervation to the lower eyelid, the side of the nose, and the upper lip. The superior alveolar branch of the ION provides sensory innervation to the upper incisor, canine, and associated gingiva. Detailed knowledge of the IOF and the establishment of a constant reference point for needle insertion are important for accomplishing safe and successful regional block and to avoid iatrogenic injury to the nerve during surgery in the midfacial region (Kazkayasi et al., 2001). Owing to its anatomical variations, it can be difficult to identify the IOF, and the landmark-based approach can be challenging even for experienced clinicians. Despite many authors’ claims regarding inconsistency in the relationship of the IOF to the teeth, the maxillary teeth, particularly the second premolar, are still in practice used as a reference for intraoral ION blocking (Aziz et al., 2000; Kazkayasi et al., 2001; Apinhasmit et al., 2006). Few articles describing the angle of needle insertion into the IOF have been published (Lee et al., 2006; Rahman et al., 2009). We planned our study to provide a detailed account of the variations of the IOF and to determine its relationship to surrounding landmarks so as to facilitate the prediction of its location and the best angle for needle insertion.
MATERIALS AND METHODS The study material consisted of 133 halves of 67 dry intact adult skulls of Indian descent. The skulls belonged to persons with ages ranging from 20 to 60 years. Their gender records were not available. Institutional ethical committee approval was obtained for pursuing the study.
Gross Anatomical Observations The IOF was studied for shape, presence of any surrounding bony projection, accessory IOF, and relationship to the maxillary teeth.
Anatomical Measurements All linear measurements were taken with a Mitutoyo digital caliper of 0.02 mm precision (Fig. 1). i. The distance of the IOF from each of the following bony landmarks was measured: Shortest vertical distance of the upper margin of the IOF from the lower rim of the orbit (IOFIOM); Transverse distance of the medial margin of the IOF from the lateral margin of the piriform aperture (IOF-PA); Transverse distance of the medial margin of the IOF from the median plane of the skull (IOF-ML); Vertical distance of the lower margin of the IOF from the upper alveolar border (IOF-AB). ii. To estimate its size, the maximum transverse and vertical dimensions of the IOF were measured.
Fig. 1. Skull showing measured parameters. IOFIOM: Vertical distance between upper margin of infraorbital foramen and inferior orbital margin. IOF-AB: Vertical distance between lower margin of infraorbital foramen and maxillary alveolar border. IOF-ML: Horizontal distance between medial margin of infraorbital foramen and midline of skull. IOF-PA: Horizontal distance between medial margin of infraorbital foramen and lateral margin of piriform aperture. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
The Angle of Needle Insertion into the Infraorbital Canal The skull was positioned on the skull stand such that the Frankfurt plane paralleled the horizontal plane and the midline of the skull paralleled the sagittal plane (Fig. 2). A needle was introduced into the IOF. Photographs of the skull with the needle in place were taken in anteroposterior and lateral views using a digital SLR Canon Camera, EOS series, secured to a tripod stand at a fixed distance from the skull stand. The distance between the skull and camera was standardized. The photographs were transferred to the computer. In the anteroposterior view, the angle between the needle and a vertical line passing through the IOF and parallel to the midline of the skull was measured with the angle measurement tool in Corel Draw version 12. In the lateral view, the angle between the needle and the horizontal line intersecting it at the IOF was measured using the same tool.
Statistical Analysis All measurements were analyzed statistically using MS Office, 2007 Excel spread sheet (Microsoft Corp., Redmond, WA) and SPSS version 2007 (SPSS Inc., Chicago, IL). A paired Student’s t-test was used to establish the statistical relationship between measurements of the right and left sides. The Pearson’s correlation coefficient was calculated to assess associations among variables.
Infraorbital Foramen
755
Fig. 2. (a) Angle between needle passing through the infraorbital foramen and the vertical line passing through the IOF parallel to the sagittal plane. (b) Angle between needle passing through infraorbital foramen and horizontal line intersecting the needle at the IOF parallel to the Frankfurt plane. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
RESULTS
Size of Infraorbital Foramen
Multiplicity of Infraorbital Foramina
The average transverse diameter of the foramen was 2.72 6 0.95 mm (range, 1.03–5.49 mm). In 20.3% of cases, the IOF was like a vertical slit with a transverse diameter
