Healing process of Type II odontoid fractures after C1-C2 posterior screw fixation: Predictive factors for pseudoarthrosis

Satoshi Yamaguchi; Brian J Park; Masaaki Takeda; Takafumi Mitsuhara; Kiyoharu Shimizu; Pei-Fu Chen; Royce W Woodroffe

doi:10.25259/SNI_198_2022

Healing process of Type II odontoid fractures after C1-C2 posterior screw fixation: Predictive factors for pseudoarthrosis

Surg Neurol Int. 2022 Mar 31:13:116. doi: 10.25259/SNI_198_2022. eCollection 2022.

Authors

Satoshi Yamaguchi¹, Brian J Park¹, Masaaki Takeda², Takafumi Mitsuhara², Kiyoharu Shimizu², Pei-Fu Chen³, Royce W Woodroffe¹

Affiliations

¹ Department of Neurosurgery, University of Iowa Hospitals and Clinics, Iowa City, United States.
² Department of Neurosurgery, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima City, Hiroshima, Japan.
³ Department of Anesthesiology, Far Eastern Memorial Hospital, New Taipei City, Taiwan.

Abstract

Background: The healing process after C1-C2 posterior screw fixation (C1-C2 PSF) for odontoid fractures is not well understood. Here, we evaluated such processes and identified factors potentially contributing to pseudoarthroses following fusions for Type II odontoid fractures.

Methods: Pre- and post-operative cervical radiographs and computed tomography (CT) images from 15 patients with preoperative Type II odontoid fractures who underwent C1-C2 PSF were retrospectively reviewed.

Results: CT images identified three areas of bone fusion: The primary fracture site in the dens (9/15 patients, 60%), the atlanto-dental interspace (ADI) (10/15, 67%), and C1-C2 interlaminar space after onlay bone grafting (4/15, 27%). All patients showed bone fusion in at least one of three areas, while only one patient (6.7%) achieved bone fusion in all three areas. With these overall criteria, nine of 15 patients (60%) were considered fused, while six patients (40%) were determined to exhibit pseudoarthroses. Univariate analyzes showed that the preoperative C2-C7 SVA for the nonunion group was significantly larger versus the union group, and bone fusion at the level of the ADI was significantly more common in the nonunion versus the union group.

Conclusion: CT studies identified three anatomical areas where bone fusion likely occurs after C1-C2 PSF. Increased sagittal balance in the cervical spine may negatively impact the fusion of odontoid fractures. Further, bone fusion occurring at other sites, not the primary fracture location, through stress shielding may contribute to delayed or failed fusions.

Keywords: Bone fusion; C1-C2 posterior screw fixation; Odontoid fracture.