Analysis Of Risk Factors For Axial Pain After ACDF Using Zero-p Interbody Fusion

Objective:Axial pain is a kind of postoperative complication which seriously affects patients’quality of life.Most of these studies were limited to traditional plate and cage systems,and few studies involved patients with zero-p interbody fusion.Due to the uncertainty and controversy on postoperative axial pain after ACDF with zero-profile implants,we aimed to:identify the potential risk factors of post-operative axial pain after ACDF with zero-profile implant in single-level CSM patient;clarify the correlation between postoperative axial pain and disc height change in this study,and provide evidence in preventing ACDF-related post-operative axial pain,and increase the clinical outcome of ACDF-treated CSM patients.Methods:Patients who suffered from single-level CSM and who received ACDF with zero-profile implant between 2018 January to 2021 January were reviewed.Of 200 single-level CSM patients,144 patients who passed the inclusion criteria were enrolled.Patients were divided into two groups according to the severity of postoperative axial pain as measured by postoperative neck visual analogue scale(nVAS).Clinical parameters including age,sex,smoking history,symptom duration,body mass index(BMI),the Japanese Orthopaedic Association(JOA)scores,as well as radiological parameters were obtained pre-and post-operatively,and the data were compared between two groups.Pearson’s chi-square tests and Mann-Whitney U tests were implemented to identify statistically significant differences between subgroups for categorical and continuous data,respectively;otherwise,the data were tested with Student’s t-test.Risk factors were identified using logistic regression.The receiver operating characteristic(ROC)curve was also analyzed using SPSS to evaluate the significance of the differences in the area under the ROC curve(AUC).The Youden index was used to determine the cutoff value for the moderate to severe postoperative axial pain.The Youden index is used to determine the threshold value.Further,patients were divided into two groups according to preoperative C2-7 Cobb angle to explore the relationship between it and postoperative axial pain.Results:Of the patients(97.8%)achieved satisfied neurological recovery,and 88.2%of the patients achieved fusion at 1-year follow-up.33%of the patients(48 patients out of 144)had sustained postoperative axial pain after the surgery.Comparison of different severity groups exhibited no significant differences in terms of the possible risk factors(P>0.05)except for preoperative C2-C7 Cobb angles(6.33 ± 6.53 vs.11.88 ± 7.41,P<0.05).Furthermore,correlation analysis showed that the preoperative C2-C7 Cobb angle is significantly correlated with the severity of the postoperative axial pain(R2=0.83,P<0.01).In addition,logistic regression analysis demonstrated that the preoperative C2-C7 Cobb angle is an independent predictor of postoperative axial pain(P<0.01,OR=0.53).Further receiver operating characteristic(ROC)analysis displayed an area under the curve(AUC)of 0.78(P<0.01)for preoperative C2-C7 Cobb angle,and the optimal cutoff was 8.4°(sensitivity 0.77,specificity 0.65).Patients were divided into group A(<8.4°)and group B(≥8.4°)according to the threshold value(8.4°)obtained from the ROC curve.The preoperative C2-7 Cobb angle was an independent factor affecting postoperative axial pain(P<0.001).Compared with preoperative C2-7 Cobb angle≥8.4°,patients with preoperative C2-7 Cobb angle<8.4 ° have a greater probability of postoperative axial pain,HR=3.47(95%CI:1.90-6.34).Conclusion:The pre-operative C2-C7 Cobb angle is a risk factor for severe postoperative axial pain after anterior cervical discectomy and fusion with zero-profile interbody.There is no direct relationship between postoperative axial pain and postoperative height changes of intervertebral space.The appropriate expanding of the intervertebral space is more conducive to decompression and the recovery of nerve function.We should be cautious when poor preoperative C2-C7 Cobb angle is found in myelopathy patients planning to use zero-profile interbody to treat such patients.