Clinical anatomy of the nasal process of the frontal bone (spina nasalis internal)

OBJECTIVES: During endonasal frontal sinusotomy with the sharp spoon, a sol id 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 intern al nasal spine (spina nasalis internal. A prominent spina may render an ext ended sinusotomy difficult and may call for use of the drill. A series of a natomic measurements is presented to illustrate the 3-dimensional anatomy o f 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 mea ns of a sharp spoon. The dimensions of the remaining nasal spine were measu red subsequently together with the anterior-posterior diameter of the infer ior frontal sinus, the thickness of the anterior frontal sinus wall, and th e distance from the neo-ostium to the anterior ethmoidal artery. RESULTS: The individual microanatomy of the medial floor of the frontal sin us showed a wide range of variation. The average height of the individual s pine 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 quarte rs of the cases, the neo-ostium was separated by just one anterior ethmoida l cell from the anterior ethmoidal artery. CONCLUSIONS: The presented investigations provide the surgeon with quantita tive data on the individual anatomy of the nasal spine and offer additional information for selecting the appropriate surgical procedure in the indivi dual patient.