Prediction of late enophthalmos using quantitative measures in isolated medial orbital wall fracture: Multiple regression analysis.

Background: Enophthalmos is one of the most distressing complications of orbital fracture, and when faced with a blowout fracture, plastic surgeons often find it difficult to determine the need for surgical correction. Although a number of studies have been conducted on this topic, no study has yet been performed using a set of measurable parameters.

Methods: We quantitatively measured orbital fracture areas (OFA), volumes (OFV), and medial rectus muscle cross-sectional ratios in patients with an isolated medial orbital wall fracture defect during a 5-year period from 2014 to 2018. Only conservatively treated patients constituted the study cohort. Enophthalmos was measured by two plastic surgeons at ≥6 months after trauma. We analyzed correlations between various parameters and degrees of late enophthalmos in the study cohort.

Results: Significant correlations were observed between several parameters and late enophthalmos. Multiple regression analysis resulted in the following coefficients: -0.449 is constant (p = 0.017), 0.596 and 0.460 for OFA (p = 0.000) and OFV (p = 0.005), respectively. However, no significant relationship was observed between enophthalmos and medial rectus muscle cross-sectional ratios (p = 0.340).

Conclusions: The results of this study enable the degree of late enophthalmos in conservatively treated patients to be predicted using OFV and OFA values. We suggest five indications that require surgical correction without long-term clinical follow-ups: (1) OFA ≥ 1.90 cm, (2) OFV ≥ 1.00 cm, (3) 1.30 OFA + OFV > 5.32, (4) signs of muscle incarceration, and (5) signs of severe retrobulbar hematoma. The more satisfactory the five indications are, the greater is the need for surgery.