What is the Orbital Volume of African-Americans?

Abstract

PurposeMeasurements of orbital volume (OV) are important for reconstructive operations of orbits such as congenital deformities, trauma, and pathology. Successful orbital reconstruction relies on an accurate restoration of OV. The purpose of this study was to identify the OV in the African-American (AA) population. The specific aims were to compare OV of AAs to Caucasians and right-to-left OV in the same racial group. This is the first project in available literature that calculates these OVs. Materials and methodsThe authors implemented a retrospective observational study of successive subjects who received a maxillofacial computed tomography (CT) scan at Grady Memorial Hospital between 2017 and 2020. The primary predictor variable was race. The primary outcome was orbital volume. Two independent examiners calculated OV with an open access OsiriX MD software (version 10.0.5; Pixmeo, Switzerland). All CT scans were acquired using a departmental-based max-face CT scan protocol; 0.6mm slice thickness, 0.5mm slice increment, 100-120kV, 80-440mA, 200-220 FOV, 0.656 Pitch, and a 512 × 512 image matrix. All CT scan data sets were anonymized. The CT images was exported in the digital imaging and communication in medicine (DICOM) format file from Philips Intellispace PACS Enterprise 4.4 software to an external hard drive WD My Passport for Mac. Computer-assisted manual segmentation of OV was performed using an open-access OsiriX MD (software version 10.0.5 [Pixmeo, Switzerland]). The anterior and posterior boundary of the orbit was defined by posterior lacrimal crest and anterior aspect of the optic canal, respectively. Inter-rater reliability was calculated. Differences in means between races, genders, and sides were tested using an independent samples T-test. ResultsSixty subjects (120 orbits) with an average age of 36.7 years (range 22 to 78) met the inclusion criteria. Male-to-female ratio was 1:1. Racial distribution represented 30 AA (50%) and 30 Caucasian patients (50%). Inter-examiner reliability was 0.973. The mean OV of AA and Caucasians was 22.375 cm3 and 23.225 cm3, respectively (P = .07). The mean OV in AA and Caucasian males was 23.919 cm3 and 24.168 cm3, respectively (P = .71). The mean OV in AA and Caucasian females was 20.832 cm3 and 22.282cm3, respectively (P = .013). Gender analysis revealed that AA males had a statistically significant larger OV than AA females (P = <.0001). ConclusionIn conclusion, this study showed that the mean OV for AAs was 22.38 cm3 (male 23.919 cm3; female 20.832 cm3). Caucasian males and females had a larger OV than AA males and females. Caucasian and AA males had a larger OV than Caucasian and AA females. The study findings provide normative values for race and gender between AA and Caucasians. Understanding the average value for OV based on race and gender will assist in preoperative surgical planning of orbital trauma repair and therefore will improve surgical outcome.