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Force necessary to fracture the orbital floor
R P Green1, D R Peters, J W Shore
1USAF School of Aerospace Medicine, Brooks AFB, Texas 78235.
Ophthalmic Plastic and Reconstructive Surgery
|January 1, 1990
Summary
This study quantifies the force needed for orbital floor fractures in primates, revealing low-energy trauma can cause these injuries via a direct ocular impact mechanism. Orbital fractures did not always prevent globe rupture.
Area of Science:
- Ophthalmology
- Biomechanics
- Forensic Science
Background:
- Orbital wall fractures are theorized to result from "hydraulic" or "buckling" mechanisms.
- Existing evidence is derived from cadaver, dried skull, and theoretical models.
- In vivo data quantifying fracture forces in live subjects are lacking.
Purpose of the Study:
- To provide the first in vivo measurements of the force required to produce orbital floor fractures in a live primate model.
- To investigate the role of direct ocular trauma in orbital floor fracture mechanisms.
- To assess the protective efficacy of orbital wall fractures against globe rupture.
Main Methods:
- Developed a novel apparatus to deliver quantifiable force directly to the globe in anesthetized Macaca fascicularis monkeys.
- Applied controlled, bilateral forces to the ocular globe.
- Examined exenterated orbits to document fracture extent and globe injuries.
Main Results:
- Orbital floor fractures were consistently produced at forces of 2.08 Joules and above.
- Posterior globe ruptures occurred within the same force range.
- Orbital wall fractures failed to protect the globe from rupture in 23% of cases.
Conclusions:
- Orbital floor fractures can occur at low energies solely from direct ocular trauma (pure hydraulic mechanism).
- This study provides critical in vivo data for understanding orbital fracture biomechanics.
- Orbital wall integrity is not always sufficient to prevent severe ocular injury.