Risk factors for early subsidence of 3D Printed Artificial vertebral after anterior cervical corpectomy and fusion.

Objective: The subsidence of vertebral body replacement may occur after anterior cervical corpectomy and fusion (ACCF) , which may lead to cervical kyphosis, spinal cord compression and neurological dysfunction. The authors aim to investigate the risk factors for early subsidence of 3D printed artificial vertebral (3D-PAVB) after ACCF surgery and to provide guidance for clinical practice.

Methods: A retrospective analysis was conducted on the data of consecutive patients with cervical spondylosis who underwent ACCF surgery at Bethune Hospital of Shanxi from 2017 to 2020. The statistical data included age, gender, disease type, body mass index (BMI), surgical segment, vertebral height, Cobb Angle, and Hounsfeld Units (HU) values of the vertebral body and endplate. The clinical efficacy of the surgery was evaluated using Visual Analog Scale (VAS), Japanese Orthopedic Association (JOA), and Neck Disability Index (NDI). Follow-up data, such as VAS, JOA, NDI, and Cobb Angle, were obtained using a repeated-measures ANOVA analysis. Univariate analysis was conducted to identify the factors contributing to the early subsidence of the3D-PAVB, and independent risk factors were determined using logistic regression. The HU value was analyzed using the Receiver Operating Characteristic (ROC) curve and the area under the Area Under Curve (AUC) to predict the subsidence of the 3D-PAVB.

Results: A total of 66 patients were included in the study, out of which 19 patients experienced subsidence of 3D-PAVB,resulting in an incidence rate of 28.8%. The postoperative JOA, VAS, and NDI scores showed significant improvement in both the subsidence and non-subsidence groups. Upon conducting univariate analysis, significant differences were observed between the two groups in terms of age, diabetes, smoking, and lower vertebral Computed Tomography (CT) values. The average HU value of the subsidence group (251.39±52.615, n=19) was significantly lower than that of the non-subsidence group (317.06±73.587, n=47, p＜0.01). Multivariate analysis revealed that smoking and HU of the lower vertebra were independent risk factors for 3D-PAVB subsidence, with an AUC of 0.772 and an optimal threshold of 272 for HU (sensitivity 78.9%, specificity 74.5%).

Conclusion: The occurrence of early subsidence of 3D-PAVB post ACCF surgery is influenced by two independent risk factors - smoking and low HU. To predict the likelihood of this outcome, it is advisable to consider smoking history and measure CT HU value prior to surgery. A lower CT HU value is indicative of a greater risk of subsidence.