Assessment of biomechanics of orbital fracture: a study in goats and implications for oculoplastic surgery in humans.
OBJECTIVE
To determine the biophysical characteristics of energy absorption of the various orbital structures and the amount of force/energy required to produce an orbital fracture in goats, and to interpret results in terms of human clinical applicability.


METHODS
Experimental animal study.


METHODS
The energy required to fracture the orbit on direct globe impact was measured. We used a variety of other measurements, including high-speed videography, intraocular pressure, and intraorbital pressure measurements to describe the biophysics of floor fracture. Twenty-one goats and 42 orbits were studied in this single institutional site study.


RESULTS
Our measurements determined the fracture threshold for the caprine orbit averaged 26.5 N (SE 3.1 N) with a total energy threshold for fracture of 2600 mJ (SE 280 mJ). Eye deformation measured 6 mm with deformation energy dissipation measuring 100 to 180 mJ (SE 10 mJ). Eye displacement measured 10 mm with dissipation measuring 50 to 75 mJ (SE 4.0 mJ). The deconvoluted bone fracture energy averaged 2350 mJ (SE 260 mJ).


CONCLUSIONS
Impact energy applied to the orbit through the eyeball is absorbed and dissipated by three primary mechanisms: (1) globe deformation, (2) globe displacement, and (3) orbital fracture. Excess energy (above the energy required for deformation and displacement) >or=2350 mJ will result in an orbital fracture.
Gilliland
Grant D
GD
Baylor University Medical Center, Dallas, Texas, USA. grantg1@sbcglobal.net
Gilliland
Guy
G
Fincher
Timothy
T
Harrington
John
J
Gilliland
Jared M
JM
D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D004195:Disease Models, Animal; D006041:Goats; D009915:Orbit / Q000293:injuries* / Q000503:physiopathology; D009917:Orbital Fractures / Q000503:physiopathology*; D011312:Pressure; D014741:Video Recording