BACKGROUND:At present,research has only shown that the cervical lordosis ratio can be an important factor in predicting the loss of lordosis curvature after laminoplasty,and no one has studied whether the cervical lordosis ratio,a dynamic level indicator,can be one of the decision-making factors for the selection of posterior cervical surgical procedures. OBJECTIVE:To investigate whether the cervical lordosis ratio,an index of cervical hyperextension and hyperflexion,can be used as a selective index for laminoplasty and laminectomy fusion. METHODS:A retrospective review of 141 patients who had undergone posterior cervical surgery more than one year of follow-up due to multi-level cervical spondylotic myelopathy from December 2015 to March 2020 was performed.Among them,63 patients received laminectomy and fusion(laminectomy and fusion group)and 78 patients received laminoplasty(laminoplasty group).The demographic statistics(gender,age,body mass index,follow-up time),imaging indexes such as C2-7 Cobb angle,C2-7 range of motion,flexion Cobb angle,extension Cobb angle,flexion range of motion and extension range of motion,clinical effect indexes such as Japanese Orthopaedic Association score and visual analog scale score were compared between the two groups.The evaluation index of cervical lordosis alignment change was C2-7 Cobb angle difference before and after operation(ΔCL).Cervical lordosis ratio was equal to 100%×flexion range of motion/C2-7 range of motion.Receiver operating characteristic curve analysis was used to determine the role of cervical lordosis ratio in predicting postoperative severe cervical lordosis loss(ΔCL≤-10°).According to the critical value of cervical lordosis ratio(68.5%),all patients were divided into low cervical lordosis ratio group and high cervical lordosis ratio group.In these two ratio groups,the cervical lordosis alignment index and clinical effect index between the two operation groups were discussed again. RESULTS AND CONCLUSION:(1)Cervical lordosis alignment decreased after laminectomy and fusion and laminoplasty(P=0.039,P=0.002),and cervical lordosis alignment change in laminoplasty group(ΔCL)was greater than that of laminectomy and fusion group,and the difference between the two groups was statistically significant.(2)Based on receiver operating characteristic curve analysis,cervical lordosis ratio in predicting severe cervical lordosis alignment change(ΔCL≤-10°)had good identification ability(area under the curve=0.792).(3)In low cervical lordosis ratio group,there was no significant difference in cervical lordosis alignment change(ΔCL)between laminectomy and fusion group and laminoplasty group(P=0.141).(4)In high cervical lordosis ratio group,the ΔCL of laminoplasty group was greater than that in laminectomy and fusion group(P=0.001),which had a higher probability of postoperative severe cervical lordosis alignment change(ΔCL≤-10°)(43%,29%).(5)It is indicated that cervical lordosis ratio can be used as a decision-making index for the choice of posterior surgery for multi-level cervical spondylotic myelopathy.Laminoplasty can be considered in the low cervical lordosis ratio group,while laminectomy and fusion can be considered in the high cervical lordosis ratio group.