Comparison of Atlantoaxial Functional and Radiographic Outcomes after Posterior Temporary Fixation Preserving with Detaching the Semispinalis Cervicis for Odontoid Fracture

Abstract Background: The semispinalis cervicis (SSC) is attached to the spinous process of the C2–C5 vertebra and distally to the transverse process of the T1–T6 vertebra, like a primary power source for extension of the cervical spine. This study was to compare the outcomes following temporary posterior fixation in two cohorts of patients who either underwent our technique of preserving SSC (P-SSC) or traditional technique of detaching the SSC (D-SSC). Methods : The conventional posterior temporary fixation was modified by preserving the SSC inserted into the C2 process. A total of 16 patients with odontoid fracture underwent the temporary posterior fixation preserving the SSC (P-SSC) or detaching the SSC (D-SSC). We measured the frequencies of postoperative axial symptom and cervical range of motion (ROM) in the rotation. The cross-sectional areas of posterior cervical muscles were also measured using axial CT. Results: At the final follow-up, in 16 cases from each group fracture healing was achieved. The total extension ROM of C1-C2 in the P-SSC was 56.8±3.5̊, while it was larger than 52.0±4.6̊ in the D-SSC. The frequency and severity of limitations of ADL accompanying each of three neck movements i.e. extension, flexion and rotation were 2.8±0.5, 1.9±0.6 and 2.0±0.5, respectively in the P-SSC; and 2.9±0.4, 2.3±0.5 and 2.6±0.5, respectively in the D-SSC. Regarding the average atrophy rate, it was 6.0±2.9% at the level C3 and 6.7±4.3% at the level C5 in the P-SSC; and 17.9±7.4% at the level C3 and 7.5±4.7% at the level C5 in the D-SSC. Conclusion: The frequencies of ADL limitations, the incidence of axial symptoms and loss of ROM accompanying neck extension, and atrophy rate of the posterior cervical muscles were lower for the atlantoaxial posterior temporary fixation preserving the SSC.