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http://dx.doi.org/10.3340/jkns.2021.0011

Analyzing the Significance of T1 Slope minus Cervical Lordosis in Patients with Anterior Cervical Discectomy and Fusion Surgery  

Lee, Ho Jin (Department of Neurosurgery, St. Vincent Hospital, College of Medicine, The Catholic University of Korea)
You, Soon Tae (Department of Neurosurgery, St. Vincent Hospital, College of Medicine, The Catholic University of Korea)
Sung, Jae Hoon (Department of Neurosurgery, St. Vincent Hospital, College of Medicine, The Catholic University of Korea)
Kim, Il Sup (Department of Neurosurgery, St. Vincent Hospital, College of Medicine, The Catholic University of Korea)
Hong, Jae Taek (Department of Neurosurgery, Eunpyeong St. Mary's Hospital, College of Medicine, The Catholic University of Korea)
Publication Information
Journal of Korean Neurosurgical Society / v.64, no.6, 2021 , pp. 913-921 More about this Journal
Abstract
Objective : Accurate measurement of T1 slope (a component of T1s minus cervical lordosis [CL]) is often constrained by anatomical limitations. In this situation, efforts should be made to find the exact meaning of T1s-CL and whether there are any alternatives to it. Methods : We enrolled 117 patients who received two-level anterior cervical discectomy and fusion (ACDF). Occipital slope, C2 slope (C2s), C7 slope (C7s), T1, O-C2 angle (O-C2A), C2-7 angle (C2-7A), O-C7 angle (O-C7A), T1s-CL, C7-T1 angle (C7-T1A), and C2-7 sagittal vertical axis were measured. We determined 16° (T1s-CL) as the reference point for dividing subjects into the mismatch group and the balance group, and a comparative analysis was performed. Results : The mean value of C7-T1A was constantly maintained within 2.6° peri-operatively. In addition, C2s and T1s-CL showed the same absolute change (Δ|0.8|°). The mean values of T1s-CL of the mismatch and balance groups were 23.0° and 7.6°, respectively. The five factors with the largest differences between the two groups were as follows : C2s (Δ13.3°), T1s-CL (Δ15.4°), O-C2A (Δ8.7°), C2-7A (Δ14.7°), and segmental angle (Δ7.9°) before surgery. Only four factors showed statistically significant change between the two groups after ACDF : T1s-CL (Δ4.0° vs. Δ0.2°), C2s (Δ3.2° vs. Δ0.7°), O-C2A (Δ2.6° vs. Δ1.3°), C2-7A (Δ6.3° vs. Δ1.3°). A very strong correlation between T1s-CL and C2s was also found (r=|0.88-0.96|). Conclusion : C2s itself may be the essential key to represent T1s-CL. The amounts and directions of change of these two factors (T1s-CL and C2s) were also almost identical. The above phenomenon was re-confirmed once again through the correlation analysis.
Keywords
T1 slope; Cervical lordosis; Cervical sagittal balance; Anterior cervical discectomy and fusion; C2 slope;
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