Odontoid hypoplasia.
From a randomised series of 500 adult patients, average measurements of the normal adult odontoid peg in the vertical and sagittal planes as seen on a standard lateral film of the cervical spine are given, and it is suggested that measurements which fall below this range should be interpreted as indicating "odontoid hypoplasia" irrespective of the cause of the abnormality. A series of 500 lateral radiographs of the upper cervical spine showed the mean height of the odontoid to be 18.0 mm in males and 16.8 mm in females, and it is concluded that a height measurement of less than 11.9 mm in either sex can be taken as the criterion of odontoid hypoplasia. A case history of one patient with hypoplasia is given, by way of illustration.
Adult↗