Anatomic Variability of the Human Orbit

Automated 3-D Computer-Aided Measurement of the Bony Orbit: Evaluation of Correlations among Volume, Depth, and Surface Area

(1)The study aimed to measure the depth, volume, and surface area of the intact human orbit by applying an automated method of CT segmentation and to evaluate correlations among depth, volume, and surface area. Additionally, the relative increases in volume and surface area in proportion to the diagonal of the orbit were assessed. (2) CT data from 174 patients were analyzed. A ball-shaped mesh consisting of tetrahedral elements was inserted inside orbits until it encountered the bony boundaries. Orbital volume, area depth, and their correlations were measured. For the validation, an ICC was used. (3) The differences between genders were significant (p < 10-7) but there were no differences between sides. When comparing orbit from larger to smaller, a paired sample t-test indicated a significant difference in groups (p < 10-10). A simple linear model (Volume~1 + Gender + Depth + Gender:Depth) revealed that only depth had a significant effect on volume (p < 10-19). The ICCs were 1.0. (4) Orbital volume, depth, and surface area measurements based on an automated CT segmentation algorithm demonstrated high repeatability and reliability. Male orbits were always larger on average by 14%. There were no differences between the sides. The volume and surface area ratio did not differ between genders and was approximately 0.75.

Insights into Orbital Symmetry: A Comprehensive Retrospective Study of 372 Computed Tomography Scans

Background: The operation planning and production of individualized implants with the help of AI-based software after orbital fractures have become increasingly important in recent years. This retrospective study aimed to investigate the healthy orbitae of 372 patients from CT images in the bone and soft tissue windows using the Disior™ Bonelogic™ CMF Orbital software. (version 2.1.28). Methods: We analyzed the variables orbital volume, length, and area as a function of age and gender and compared bone and soft tissue windows. Results: For all variables, the intraclass correlation showed excellent agreement between the bone and soft tissue windows (p < 0.001). All variables showed higher values when calculated based on bone fenestration with, on average, 1 mL more volume, 0.35 mm more length, and 0.71 cm2 more area (p < 0.001). Across all age groups, men displayed higher values than women with, on average, 8.1 mL larger volume, a 4.78 mm longer orbit, and an 8.5 cm2 larger orbital area (p < 0.001). There was also a non-significant trend in all variables and both sexes toward growth with increasing age. Conclusions: These results mean that, due to the symmetry of the orbits in both the bone and soft tissue windows, the healthy orbit can be mirrored for surgical planning in the event of a fracture.

Do Racial Differences in Orbital Volume Influence the Reconstruction of Orbital Trauma

PURPOSE

Successful orbital reconstruction relies on an accurate restoration of orbital volume (OV). The purpose of this study was to determine if the OV of African American (AA) subjects differs from that of Caucasian subjects.

METHODS

The authors implemented a retrospective observational study of successive subjects who received a maxillofacial computed tomography (CT) scan at a level I trauma center between 2017 and 2020. The primary predictor variable was race (AA/Caucasian). The primary outcome variable was orbital volume. Two independent examiners calculated OV with an open access OsiriX MD software version 10.0.5 (Pixmeo, Switzerland). Inter-rater reliability was calculated. Differences between races, genders, and sides were tested using independent samples t test with a significance of P < .05.

RESULTS

Sixty subjects (120 orbits) were included in the study. The mean age was 36.7 (SD ± 13.2) years with a range of 22 to 78 years. Gender distribution was equal with 30 male (50%) and 30 female (50%) subjects. Inter-examiner reliability was 0.973. The mean OV of AA and Caucasians was 22.38 and 23.23 cm³, respectively (P = .07). The mean OV of AA and Caucasian males was 23.92, and 24.17cm³, respectively (P = .71). The mean OV in AA and Caucasian females was 20.84 and 22.28cm³, respectively (P = .013).

CONCLUSIONS

African-American female subjects appear to have a smaller OV when compared with Caucasians which may influence orbital reconstruction. Laterality does not appear to be associated with any differences in OV.

Three-Dimensional Computer-Aided Analysis of 293 Isolated Blowout Fractures - Which Radiological Findings Guide Treatment Decision?

PURPOSE

Our study purpose was to clarify the extent of isolated unilateral orbital blowout fracture in relation to surgical treatment and other factors behind the treatment decision. The specific aim was to determine which computer-aided measurements based on radiological images associate with treatment choice.

METHODS

A retrospective cohort study was implemented on patients with an isolated unilateral orbital blowout fracture. Computer-aided measurement of fracture extent was performed. The study variables included treatment as primary outcome (surgical vs nonsurgical), post-traumatic orbital volume difference (mL) compared to contralateral orbit, fracture area (mm²), fracture depth (mm) as predictor variables, and age, sex, injury mechanism, side and site of orbital fracture and positions of recti muscles as explanatory variables. Postoperative outcomes were reported. Logistic regression analysis was used to determine the risk factors for surgery. The statistical significance level was set at P < .05.

RESULTS

Of 293 patients, 28.0% received surgical and 72.0% nonsurgical treatment. Volume difference, fracture area and fracture depth predicted surgical outcome (P < .001). In adjusted univariate regression analyses, fractures with moderate and severe displacement of recti muscles were more likely to receive surgical treatment than fractures with mild or no displacement (OR 6.15 and 30.75, respectively, P < .001). Isolated medial wall fractures were significantly less often (OR 0.05, P = .006) and patients with older age (OR 0.97, P = .013) slightly less often treated with surgery. Patients with preoperative symptoms had more often persisting postoperative symptoms than patients without preoperative symptoms.

CONCLUSIONS

Positions of the recti muscles are an independent radiological factor guiding orbital blowout fracture treatment decision. The bony fracture extent is a combination of volume difference, fracture area and fracture depth which are strongly correlated to each other. A computer-aided method significantly facilitates the systematic evaluation of bone fragments, and the extent of orbital fractures.

Contemplations and Ruminations of Methodological Error

PURPOSE

Journal articles in our field of oral and maxillofacial surgery are rife with case studies, cohort reviews, meta-analysis, basic science studies, surgical techniques, and anatomic studies. The data found in these studies often rely on multiple measurements by which the authors draw their conclusions. Accurate measurements play a critical role in the design of the study, which in turn affects the conclusion that the author is attempting to convey. Investigators must determine and develop the processes to determine the methodological errors associated with each project to help with determining the accuracy of these measurements. The aim of this study is to highlight some of the methodological errors contained in the material and methods in oral and maxillofacial surgery studies over the calendar years of 2018 and 2019 and how best to evaluate them.

MATERIALS AND METHODS

The inclusion criteria involved articles that used measurements where discrepancies could exist such as clinical measurements, histological measurements, and radiological measurements. The number of specimens or subjects measured in each study was tabulated.

RESULTS

Over the 2-year period considered, 744 articles were published, and 116 (15.6%) of them met the inclusion criteria. Of these articles, 37 (32%) reported a methodological error, while 79 (68%) did not. In addition, 31 (84%) of the articles with a methodological error were radiographic, while only 6 (16%) were not radiographic. Among the studies that reported methodological error, there were approximately 7 different types used with no rationale given for the choice.

CONCLUSIONS

We believe that it is important to ensure sound methods and materials, including a stated methodological error. An attempt at standardization will help to serve to enhance and strengthen the different research studies seen in our field.