Analysis of risk factors for an increase in the cervical sagittal vertical axis after cervical laminectomy with lateral mass screw fixation

Abstract

Abstract Background: In recent studies on factors affecting quality-of-life (QOL) of patients after cervical laminectomy with fixation, cervical sagittal parameters were considered to have a strong association with the QOL.And among these parameters, the cervical sagittal vertical axis(cSVA) is regarded as the most important one. Therefore the purpose of this study is to analyze risk factors for an increase in the cSVA after cervical laminectomy with lateral mass screw fixation (LLMF). Methods: A retrospective analysis of 128 patients who underwent LLMF from October 2018 to June 2021. The following parameters were measured: McGregor's slope (McGS), C2 slope (C2S), C2-7 cobb angle (CL), cSVA, and T1 slope (T1S). Two groups were divided according to whether ΔcSVA is positive or negative, including the negative ΔcSVA group (Group N) and the positive ΔcSVA group (Group P). The basic characteristics of patients, clinical outcomes, and imaging parameters of the two groups were compared. Results: A total of 77 patients were included in this study (46 men and 31 women, a mean age of 61.44 ± 7.23 years, and a mean follow-up time of 18.60 ± 5.20 months). There were 28 patients in Group N and 49 in Group P. Patients in the two groups were similar in basic characteristics. C2S, cSVA, and NDI were significantly different postoperatively (p=0.002,0.001, and 0.031). Group P had larger changes of C2S, cSVA, and T1S than that of Group S (p=0.001,p＜0.001, and p=0.008). ΔcSVA was significantly correlated with ΔMCGS, ΔC2S, and ΔT1S (r=0.310,0.577, and 0.435). Multivariate linear analysis revealed that ΔcSVA was associated with the ΔC2S and ΔT1S (β=0.552 and 0.314). Postoperative C2S demonstrated a significant correlation with clinical outcomes. Conclusion: A smaller reduction in T1S after LLMF would be a risk factor for an increase in cSVA. Postoperative C2S increases would be necessary to maintain the horizontal gaze and the head's center of gravity if postoperative cSVA increases excessively. Postoperative C2S can also be a good predictor of clinical outcomes.