Age-stratified anatomical differences of orbital floor and medial orbital wall blowout fractures.

Purpose: To define the anatomical variance between orbital floor and medial orbital wall blowout fractures, and its change with age.

Methods: This was a retrospective, observational study analyzing data from 557 patients with isolated blowout fractures of the orbital floor or medial orbital wall. Axial and quasi-sagittal CT images were analyzed to compare radiologic data on orbital wall morphology between fracture site groups and among age groups. Patient ages were classified as: 0-9 (childhood), 10-18 (adolescence), 19-44 (early adulthood), 45-64 (middle adulthood), and ≥ 65 years (late adulthood).

Results: The orbital floor fracture group demonstrated significantly steeper orbital floors (p < 0.001), while the medial wall fracture group exhibited a tendency for more convex medial orbital walls (p = 0.066). Among age groups, medial wall fracture was predominant in the late adulthood group only (p < 0.001). Patients in the childhood and late adulthood groups had significantly flatter orbital floors (p < 0.001). Patients in the childhood group presented with a concave medial orbital wall (p < 0.001). The anteroposterior length of the medial orbital wall and the number of ethmoid air cells were not different between fracture groups (p = 0.603 and 0.753, respectively) and among age groups (p = 0.306 and 0.456, respectively).

Conclusion: Patients with orbital floor and medial orbital wall fractures had anatomically steeper orbital floors and convex medial orbital walls, respectively. Age-related differences in the shape of the orbital walls may influence variation in orbital blowout fracture sites by age.

Key Messages: WHAT IS KNOWN : Fracture sites of the orbital walls differ according to age groups. The floor is more commonly fractured in children, with a shift to the medial wall in the elderly.

What Is New: Orbital floor and medial orbital wall fractures present with anatomically higher floor and medial walls, respectively, compared to each other.  This indicates steeper convexities of the walls which predispose them to fracturing. Children's medial orbital walls are initially concave, then shift to convex structures with facial bone and sinus maturation. This explains why there is a change in blowout fracture site between age groups, as it has been documented that concave structures are more resistant to deformation.