Clinical Anatomy of the Nasal Process of the Frontal Bone (Spina Nasalis Interna)

Abstract

OBJECTIVES: During endonasal frontal sinusotomy with the sharp spoon, a solid piece of bone is frequently encountered anterior to the neo-ostium. This bone may be referred to as the nasal process of the frontal bone or internal nasal spine (spina nasalis interna). A prominent spina may render an extended sinusotomy difficult and may call for use of the drill. A series of anatomic measurements is presented to illustrate the 3-dimensional anatomy of the spina nasalis and the regional anatomy. METHODS: A maximum endonasal frontal sinusotomy (Draf type I-II procedure, nasofrontal approach type II) was performed on 36 anatomic specimens by means of a sharp spoon. The dimensions of the remaining nasal spine were measured subsequently together with the anterior-posterior diameter of the inferior frontal sinus, the thickness of the anterior frontal sinus wall, and the distance from the neo-ostium to the anterior ethmoidal artery. RESULTS: The individual microanatomy of the medial floor of the frontal sinus showed a wide range of variation. The average height of the individual spine was 10 mm, the maximum depth 6 mm. A correlation was found between the nasofrontal angle of the specimen and the anterior-posterior dimension of the spine: the more acute the angle, the thicker the spine. In three quarters of the cases, the neo-ostium was separated by just one anterior ethmoidal cell from the anterior ethmoidal artery. CONCLUSIONS: The presented investigations provide the surgeon with quantitative data on the individual anatomy of the nasal spine and offer additional information for selecting the appropriate surgical procedure in the individual patient.