Anterior screw fixation for type II odontoid process fractures: A single-center experience with the double Herbert screw fixation technique (Retrospective cohort study)

Background: In type II odontoid fractures with intact transverse ligament as classified by the Anderson and D'Alonzo system, anterior screw fixation offers the best anatomical and functional results. The goal of this study is to review the results of the double screw technique in anterior odontoid surgery using a headless 3.0-mm.-diameter cannulated Herbert screw on patients with odontoid process fractures. Methods: From January 2015 through March 2019, 12 cases of acute traumatic type II odontoid fractures were treated with double anterior screw fixation using 3.0-mm Herbert screws, slightly smaller than the standard size for Caucasian populations. The data collected included radiographic measurements, postoperative complications, union rate and clinical outcomes in follow-up examinations over an average of 24-months. Results: The age of the 12 patients, 8 males and 4 females, ranged from 17 to 68 years (mean, 38.42 +/- 20.14). The fracture type was type IIa in 4 patients (33.33%) and type IIb in 8 patients (66.67%). The period of follow-up was 15-64 months (mean, 31.42 +/- 17.37). All the patients had good clinical results after surgery with no postoperative complications. Eleven cases (92%) had achieved bone union with 1 case (8%) of nonunion. In the nonunion case, the patient was a chronic smoker who continued smoking both during treatment and follow-up. Conclusions: This series of satisfactory clinical results demonstrates that double anterior screw fixation of type II odontoid process fractures using 3.0-mm screws is highly effective in the Thai population. Headless cannulated cancellous screws provide significant biomechanical strength which is not inferior to the traditional screws