Classification of the axial mastoid process and its clinical application / 中华创伤骨科杂志

ABSTRACT

Objective To explore a simple classification of the axial mastoid process and its clinical significance in improving the traditional screw insertion in the treatment of odontoid fracture with percutaneous anterior odontoid screwing. Methods The median sagittal CT images of 120 patients with cervical dis-ease were measured. They were 63 males and 57 females, aged from 31 to 59 years (average, 41.6 years). On their median sagittal CT images, line A was the connection of the lowest point of the anterior inferior boarder of the axis body to the vertex of the odontoid process and line B a parallel line to line A through the mastoid process. The distance between lines A and B was measured (the height of the axial mastoid process) and a complete statistical record was made to analyze the distribution and regularity of distances AB. The improved insertion points were indentified based on the above measurements (X25%and X75%) and clinical ex-perience. We reviewed 32 patients with odontoid fracture of Anderson&D' Alonzo typeⅡA, ⅡB or superficialⅢ. Of them 15 underwent percutaneous anterior screwing by the improved insertion points and 17 underwent percutaneous anterior screwing by the conventional insertion points. The 2 groups were compared in terms of incision length, operation time, bleeding, fluoroscopy frequency and hospital stay. Results Distance AB was 3.42 ± 0.68 mm. The distance AB <3 mm was classified as low-level mastoid process, the distance AB between 3 to 4 mm as slightly convex mastoid process, and the distance AB > 4 mm as convex mastoid process. Of the 120 patients, 32 (26.7% ) were classified as having a low-level mastoid process, 57 (47.5%) as having a slightly convex mastoid process, and 31 (25.8%) as having a convex mastoid process. Compared with the conventional insertion group, the improved insertion group had significantly shorter oper-ation time (31.32 ± 2.12 min versus 46.18 ± 3.63 min), significantly lower fluoroscopy frequency (18.20 ±1.57 times versus 21.27 ± 2.50 times) but significantly greater bleeding (43.22 ± 3.17 mL versus 31.22 ± 3.52 mL) (P <0.05). There were no significant differences between the 2 groups in incision length or hospital stay (P > 0.05). Conclusions In the treatment of odontoid fracture with percutaneous anterior odontoid screwing, the screw insertion can be improved according to our classification of the axial mastoid process. Our simple classification of the axial mastoid process may lead to more efficient operation and less radiation hazard.