Risk factors of titanium mesh subsidence after anterior cervical corpectomy and fusion

English Keywords:Cervical spondylotic myelopathy  Anterior cervical corpectomy and fusion  Titanium mesh subsidence  Risk factor  Intervertebral distraction distance

English Abstract:

  【Abstract】 Objectives: To investigate the incidence and potential risk factors of titanium mesh cages(TMC) subsidence after anterior cervical corpectomy and fusion(ACCF). Methods: The data of 82 patients underwent ACCF between January 2019 and December 2021 at the Spine group of Department of Orthopaedics, Peking University Third Hospital were retrospectively analyzed. There were 44 males and 38 females, aged 52.4±10.1 years (range: 34-76 years), and they were followed up for 26.6±12.5 months(range: 6-42 months). The patients were divided into subsidence group and non-subsidence group according to whether the height of the fusion segment decreased ≥2.0mm at postoperative 3 months. C2/C7 Cobb angle, Cobb angle of the operative segment, intervertebral distraction distance and fusion segment height were measured on lateral cervical X-ray films before operation, on postoeprative 1d and at 3 months after operation. The preoperative CT values of proximal and distal vertebral bodies of operative segments were measured to estimate osteoporosis; The Japanese Orthopaedic Association(JOA) score was recorded preoperatively and at the final follow-up, and the JOA score recovery rate was also documemted. Univariate analysis was performed on each variable, and variables with P<0.1 and risk factors with clinical significance were included in logistic regression analysis. Receiver operating characteristic(ROC) curve was employed to evaluate the risk factors and predict TMC subsidence, and the cut-off point was determined according to the principle of the maximum Jordon index. Results: 58 patients(70.7%) developed TMC subsidence. There was no statistical difference between subsidence group and non-subsidence group in gender, age, length of hospital stay(P>0.05). The C2/C7 Cobb angle and Cobb angle of operative segment in both groups were all significantly increased on postoperative 1d compared with before operation(P<0.05). The C2/C7 Cobb angle in the non-subsidence group and Cobb angle of operative segment in both groups were significantly increased 3 months after operation compared with before operation(P<0.05). There was no statistically significant difference in C2/C7 Cobb angle and Cobb angle of operative segment between the two groups at the same time point(P>0.05). The postoperative intervertebral distraction distance in the subsidence group was significantly larger than that in the non-subsidence group(3.82±1.93mm vs 2.37±1.98mm, P=0.003). At 3 months after operation, the intervertebral height at fusion segments in the non-subsidence group were significantly higher than that in the subsidence group(P<0.05). No statistical difference was found in the CT values of proximal and distal vertebral bodies between the subsidence group and non-subsidence group(Proximal 364.6±102.2HU vs 389.2±102.3HU, P=0.325; Distal 305.2±82.4HU vs 341.1±84.6HU, P=0.086). There was no significant difference in the improvement rate of JOA score between the two groups(P=0.442). There was no significant difference in the incidence of axial symptoms between subsidence group and non-subsidence group(6.9% vs 12.5%, P=0.409). The logistic regression analysis results showed that the odds ratio of the intervertebral distraction distance was 1.496[95%CI(1.107, 2.022), P=0.009]. The area under the ROC curve to predict TMC subsidence based on the intervertebral distraction distance was 0.717. The cut-off value of the intervertebral distraction distance was 1.83mm when the Jordan index was the maximum. Conclusions: The excessive intervertebral distraction during ACCF is an independent risk factor for TMC subsidence, and the risk of TMC subsidence is significantly increased when the distance of intervertebral distraction is more than 1.8mm during operation.