The Orbital Index: a novel comprehensive quantitative tool for prediction of delayed enophthalmos in orbital floor fracture management

Abstract

Summary: Early identification of surgical indication is critical to optimizing outcomes in orbital floor fracture management. However, identifying those at risk for delayed enophthalmos and requiring subsequent repair has remained a challenge. This study aimed to validate the Orbital Index, a prediction tool using computed tomography to stratify risk for delayed enophthalmos and establish a threshold for repair. The Orbital Index stratifies fractures by size, location, and inferior rectus rounding (a surrogate for fascioligamentous sling disruption) on a scale 0 to 6. A 22-year (1998 to 2020) multi-institution analysis of unilateral isolated orbital floor fractures was performed. Index scores were assigned to each scan, unoperated patients invited for blinded Hertel exophthalmometry assessment, and enophthalmos measurements correlated with Index scores. Interobserver scoring reproducibility was assessed with weighted Cohen kappa. Preintervention and postintervention Likert scale surveys were administered to determine whether this tool improved understanding and communication. The Orbital Index demonstrated high fidelity and interobserver reproducibility and identified a score of four or greater as a surgical threshold. Of 1769 computed tomography scans, 395 met criteria and were included for analysis. Eighty of 395 were managed operatively (operative rate, 20.3 percent). Of 315 patients managed nonoperatively, 41 (13.0 percent) agreed to follow-up evaluation and 28 (68.3 percent) were found to have enophthalmos. Unoperated patients with an Orbital Index score of 4 or higher were more likely to have enophthalmos than those with a score of 3 or less (p = 0.001). The mean weighted Cohen kappa was 0.73, corroborating reproducibility. Communication (p = 0.0003) and ability to correctly identify surgical need (p = 0.01) were improved with use of this tool. The Orbital Index is a reproducible tool to stratify risk for enophthalmos in orbital floor fracture management.

Prediction of Permanent Enophthalmos Using 3-Dimensional Integral Model in Blowout Fractures

“…This orbital index was a value wherein the size of the fracture, the location of the fracture, and the degree of herniation of the EOM obtained using a CT scan in patients with nonoperatively managed blowout fractures was scored and summed. 18 However, in our study, we did not simply present the criteria value that could predict permanent enophthalmos of 2 mm; instead, we also analyzed the structure of the orbit, created an integral model, and developed a formula with a cubic equation that enabled the continuous prediction of permanent enophthalmos. Furthermore, through regression analysis, the relationship between the predicted value and the actual uncorrected permanent enophthalmos was found, and the formula was adjusted more accurately.…”

“…Another recent study suggested an “Orbital Index” tool that could predict the occurrence of delayed enophthalmos >2 mm. This orbital index was a value wherein the size of the fracture, the location of the fracture, and the degree of herniation of the EOM obtained using a CT scan in patients with nonoperatively managed blowout fractures was scored and summed 18 . However, in our study, we did not simply present the criteria value that could predict permanent enophthalmos of 2 mm; instead, we also analyzed the structure of the orbit, created an integral model, and developed a formula with a cubic equation that enabled the continuous prediction of permanent enophthalmos.…”