Sagittal alignment correlates with the C1-C2 fixation angle and functional outcome after posterior atlantoaxial fixation for traumatic atlantoaxial instability.
The C1-C2 angle has been shown to correlate with subaxial alignment under various conditions. The aim of this study was to evaluate the correlation between the C1-C2 fixation angle and subaxial sagittal alignment as well as the impact of the sagittal vertical axis (SVA) on functional outcomes in traumatic atlantoaxial (A-A) instabilities. The data of 36 patients who underwent posterior C1-C2 fixation for traumatic A-A instability between December 2005 and September 2015 were retrospectively reviewed. Radiographic parameters, including the C1-C2 angle, occipitocervical angle, C2-C7 angle, and C2-C7 SVA, were measured before surgery and at 1-year follow-up. Clinical outcomes were measured using the visual analogue scale (VAS) and Neck Disability Index (NDI). The preoperative and postoperative relationships between parameters were analyzed. In preoperative and postoperative radiographs, the C1-C2 angle correlated with the C2-C7 angle (r = -0.347, p = 0.038, and r = -0.339, p = 0.043, respectively) and the C2-C7 SVA (r = 0.648, p < 0.001, and r = 0.436, p = 0.008, respectively). The postoperative C2-C7 SVA was directly proportional to the preoperative C2-C7 SVA and postoperative C1-C2 angle (postoperative C2-C7 SVA = 0.72 + 0.669 × [preoperative C2-C7 SVA] + 0.555 × [postoperative C1-C2], r2 = 0.677, p < 0.001). The postoperative C2-C7 SVA correlated with postoperative VAS (rs = 0.382, p = 0.021) and NDI (rs = 0.476, p = 0.003). The postoperative C2-C7 SVA was affected by the preoperative C2-C7 SVA and the postoperative C1-C2 angle and showed significant positive correlation with postoperative NDI. The C1-C2 fixation angle and the preoperative C2-C7 SVA should be carefully considered to avoid postoperative sagittal imbalance.
['Choi|Dae Han|DH|', 'Lee|Sang Gu|SG|', 'Yoo|Chan Jong|CJ|', 'Kim|Woo Kyung|WK|', 'Son|Seong|S|']
D000328:Adult D000368:Aged D000369:Aged, 80 and over D001268:Atlanto-Axial Joint D002574:Cervical Vertebrae D005260:Female D006801:Humans D016268:Internal Fixators D007593:Joint Instability D008297:Male D008875:Middle Aged D012189:Retrospective Studies D013123:Spinal Fusion D016896:Treatment Outcome D064232:Visual Analog Scale
Sagittal alignment Atlantoaxial fixation Traumatic atlantoaxial instability Cervical spine