Morphometric and geometric anatomy of the caucasian orbital floor

Morphometric analysis of the infraorbital foramen, canal and groove using cone beam CT: considerations for creating artificial organs

PURPOSE

The aim of this study was to examine the anatomy and variations of the infraorbital foramen and its surroundings via morphometric measurements using cone beam computed tomography (CBCT) scans derived from a 3D volumetric rendering program.

METHODS

354 sides of CBCT scans from 177 patients were examined in this study. DICOM data from these images were exported to Maxilim® software in order to generate 3D surface models. The morphometric measurements were done for infraorbital foramen (IOF), infraorbital groove (IOG) and infraorbital canal (IOC). All images were evaluated by 1 radiologist. To assess intra-observer reliability, the Wilcoxon matched-pairs signed rank test was used. Differences between sex, side, age and measurements were evaluated using chi-square and paired t-test and measurements were evaluated using 1-way ANOVA tests. Differences were considered significant when p<0.05.

RESULTS

The most common shape was oval for IOF and parallel for IOC without any accessory foramen. The results showed that females have smaller dimensions for the measurements between the two foramen rotundum (FR), FR-IOF, sella-FR, center of the IOF (cIOF)-nasion (N), cIOF-NB (nasion-B) (p>0.05). No significant difference was found according to age groups (p>0.05).

CONCLUSIONS

These results provide detailed knowledge of the anatomical characteristics in this particular area. CBCT imaging with lower radiation dose and thin slices can be a powerful tool for anesthesia procedures like infra orbital nerve blocks, for surgical approaches like osteotomies and neurectomies and also for generating artificial prostheses.

Anatomic analysis specific for the endoscopic approach to the inferior, medial and lateral orbit

INTRODUCTION

The endoscopic approaches to the medial and inferior orbital walls have continued to grow in popularity. The ability to provide a safe approach to the orbit through this technique has been described in a handful of studies. Even though metric analyses have been conducted on orbital anatomy, few have outlined the anatomical relations pertinent to endoscopic surgery. The goal is to provide improved understanding of the complex anatomy encountered through anatomical dissections and metric analysis of the orbit. This information could assist in approach selection during preoperative planning.

METHODS

Anatomical dissections via transantral and endonasal approaches were used to define the limits with current endoscopic sinus surgery instrumentation. The surface area was then calculated of the floor and medial wall to assess access created by the approaches. The path of the infraorbital canal was conducted to assess its placement within the orbital floor.

RESULTS

The transantral and endonasal approaches to the orbit provided an adequate surgical window inferiorly and medially. This was confirmed by the surface area calculations. Access laterally was also possible, however, it became limited as dissection advanced superior to the lateral rectus muscle. The infraorbital canal was located consistently at midline on the orbital floor.

CONCLUSION

Endoscopic access to the medial and inferior parts of the orbit is feasible and creates adequate access with current instrumentation. Knowing the surgical boundaries and the amount of exposure created can assist the surgeon in deciding a minimally invasive approach.

Morphometric analysis of the infraorbital groove, canal, and foramen on three-dimensional reconstruction of computed tomography scans

PURPOSE

This study aimed to investigate the anatomy of the infraorbital foramen (IOF), infraorbital canal (IOC), and infraorbital groove (IOG) with regard to surgical and invasive procedures using three-dimensional reconstruction of CT scans.

METHODS

The CT scans of 100 patients were evaluated retrospectively. The morphology of the IOF, IOC, and IOG as well as their relationships to different anatomic landmarks was assessed in a three-dimensional model.

RESULTS

The mean length of the IOC and IOG and the angle of the IOC relative to IOG were 11.7 ± 1.9, 16.7 ± 2.4 mm, and 145.5° ± 8.5°, respectively. The mean angles of the IOC relative to vertical and horizontal planes were 13.2° ± 6.4° and 46.7° ± 7.6°, respectively. In the relationships between the IOF and different anatomic landmarks, the mean distances from the IOF to supraorbital notch/foramen, facial midline, and infraorbital rim were 5.6 ± 3.1 mm laterally, 26.5 ± 1.9 mm laterally, and 9.6 ± 1.7 mm inferiorly, respectively. The mean distance from the IOF to anterior nasal spine (ANS) was 35.0 ± 2.6 mm, and the mean angle of the axis that passed the IOF and ANS relative to horizontal plane was 28.8° ± 4.1°. In addition, the mean soft tissue thickness overlying the IOF was 11.4 ± 1.9 mm.

CONCLUSIONS

These results provide detailed knowledge of the anatomical characteristics and clinical importance of the IOF. Such knowledge is of paramount importance for surgeons when performing maxillofacial surgery and regional block anesthesia.

A cadaveric study of the morphometric relationships and bony composition of the caucasian nasolacrimal fossa

AIMS

To describe the morphometric relationships and bony composition of the nasolacrimal fossa in a Caucasian population with particular reference to the lacrimo-maxillary suture (LMS).

METHODS

Forty-seven orbits from 24 formalin fixed cadavers were exenterated. Morphometric measurements were taken between anatomical landmarks forming the lacrimal fossa on the medial orbital wall.

RESULTS

The mean recorded distance from the anterior lacrimal crest (ALC) to the posterior lacrimal crest (PLC) and the LMS were 8.8 mm (± 1.6) and 4.3 mm (± 1.1), respectively. In 25.5% of the orbits the LMS was at the mid-vertical line (MVL), defined as a line equidistant from the ALC and PLC. In 42.5% the LMS was located anterior to the MVL toward the ALC. In 66% of the orbits the LMS was at or within one standard deviation (SD) of the MVL. The LMS was >1 SD away from the MVL toward the ALC and PLC in 19% and 15% of orbits, respectively.

CONCLUSIONS

In a quarter of the orbits in our Caucasian population the nasolacrimal fossa was formed equally by the maxillary and lacrimal bones. However, in nearly a third of the cases the LMS was located closer to the PLC, indicating predominance of the thicker maxillary bone. This may result in greater difficulty in initiating the surgical osteotomy when performing a dacryocystorhinostomy. These data contribute to our understanding of the variation in lacrimal fossa anatomy and encourage further studies in different racial groups.