Are Inferior Rectus Muscle Displacement and the Fracture's Size Associated With Surgical Repair Decisions and Clinical Outcomes in Patients With Pure Blowout Orbital Fracture?

Purpose: Although orbital blowout fractures are common, there is no consensus with respect to treatment decision making and long-term outcome. The purpose of this study was to evaluate the association between inferior rectus muscle (IRM) displacement and fracture size and the surgical repair decisions and clinical outcomes in patients with blowout fractures (BOFs).

Patients and methods: We designed a prospective cohort study and enrolled all patients who presented to the University Hospital of Geneva for evaluation of a BOF. The primary predictor variables were the IRM grade, measuring the severity of downward displacement of the IRM relative to the level of the fracture's edge (mild [grade I], moderate [grade II], or severe [grade III]), and fracture size. The primary outcome was surgical repair. The secondary outcomes were post-trauma diplopia (at baseline and at 10 days) and persistent annoying diplopia and/or enophthalmos considered independently or as a composite outcome. Other study variables included demographic and injury-related parameters. Descriptive, bivariate, and multiple logistic regression statistics were computed, and the significance level was set at P ≤ .05.

Results: The sample was composed of 108 patients with a mean age of 46.8 ± 23 years; 73.1% were men. The IRM grade was associated with surgical repair (P < .001), post-trauma diplopia (P < .001), and the composite outcome (P = .003). Fracture size was associated with enophthalmos (P = .03) and the composite outcome (P = .009). In the adjusted model, only IRM grades II and III were associated with the decision for surgical repair (P < .001).

Conclusions: The results of this study suggest that the IRM grade, unlike fracture size, may be a valid measurement in surgical decision making, as well as in determining BOF severity, as evidenced by the correlation between the IRM grade and surgical repair, as well as clinical outcome.