Background and objectives: Orbital floor fractures are a common result of orbital injury. These fractures can vary in size from small cracks to large defects. Fractures of the orbital floor mainly occur medial to the infraorbital groove and canal and medio caudal from the orbital roof, due to the limited thickness of the bone in this area. As a result of an orbital floor fracture, the volume of the orbit can increase with hypoglobus, enophthalmos and diplopia as well known consequences. This present study was performed to develop an engineering model of the orbital floor in which materials for orbital floor reconstruction can be evaluated in order to formulate recommendations for the choice of implant material in orbital floor reconstruction in relation to defect size.

Methods: Data from the literature on the orbital floor, intraorbital pressure and traumatic changes in orbital volume causing enophthalmos were incorporated in a mathematical orbital floor engineering model. Using the engineering model, the behaviour of different reconstruction materials over a series of theoretical orbital floor defects was evaluated.

Results: A close relation between the mechanical properties of reconstruction materials and defect size of orbital floor fractures with respect to changes in orbital volume and enopthalmos was observed when applying the engineering model. The developed orbital floor engineering model was shown to be helpful in the pre-operative evaluation of reconstruction materials for orbital floor fractures providing information on what reconstruction material can be considered appropriate for a particular orbital floor defect.

Conclusions: The engineering model is helpful in selecting reconstruction materials accounting for critical parameters. With the model, clinicians can preoperatively judge whether a selected material is suitable. Applying such a material in reconstruction of the defect is thought to prevent early onset enophthalmos.

Key words: orbital floor fracture; orbital defects; reconstruction material; orbital surgery; engineering model