The spectrum of minimal clefting: Process-oriented cleft management in the presence of an intact alveolus

The minimal cleft lip provides a model for study of the clefting process. Nasolabial embryogenesis can be best understood using the concept of embryonic fields in which midline structures (columella, philtrum, premaxilla, septum, vomer, and ethmoids) develop with paired, fused A fields. Anatomic features of the minimal cleft lip suggest that the actual clefting site is located at the interface between the A and B fields within the lateral piriform wall. Study of the progression of clefting, using this model, places the timing of the clefting event to Carnegie stage 14. The degree to which this initial event affects subsequent fusion of the lateral and medial nasal processes (D and C fields) determines the final morphology of the cleft. Using this model, a rational basis is presented for the surgical management of minimal clefting in its varying manifestations.