Experimental evaluation of susceptibility to fractures of the orbital floor in patients with unilateral complete cleft palate.

We set out this study to verify a hypothesis that orbital floor fractures tend to affect wider areas in patients with unilateral complete cleft palate. Using a striking machine, the inferior orbital rims of eight normal skulls (intact skull group) and eight skulls with parts of the maxillas removed to simulate alveolar and palatal clefts (cleft skull group) were impacted. The fractured areas were compared. Models designed using a computer were produced to simulate the skulls of 12 normal people and 12 patients with left unilateral complete cleft palate, and were classified as the intact model group and the cleft model group, respectively. Computer simulation of applying external forces to the inferior orbital rim of each model was performed. Areas where stresses exceeded the bone-yielding threshold were compared. Actual fractured areas were significantly larger in the cleft skull group than in the intact skull group. Theoretical fracture areas were also significantly greater in the cleft model group than in the intact model group. We conclude that orbital floor fractures develop in wider areas in patients with unilateral complete cleft palates, because of the instability of the maxilla on the cleft side.