Detection of shape outliers, with an application to complete unilateral cleft lip and palate in humans

Cleft lip/palate (CLP) is a relatively common birth defect (about 1 per 1000) so disfiguring that nowadays it is almost always corrected surgically as early as possible. The postnatal surgical correction does not, however, result in a normally growing maxilla (upper jaw), but instead, owing to scar tissue and altered mechanical function, one that grows abnormally. It is of interest to determine whether that abnormality is itself homogeneous. In this paper I comment on this question both as an example of geometric morphometrics and as an example of the kind of question that craniofacial surgeons might propose in their role as physical anthropologists, students of the variation of human form.