Risk factors of early subsidence of 3D-printed artificial vertebral body following single-level anterior cervical corpectomy and fusion (ACCF): retrospective study of 98 patients.

Background: The 3D-printed artificial vertebral body (AVB) was designed with theoretically better biomechanical properties than traditional implants to decrease the incidence of implant subsidence. However, implant subsidence still occurs, with the potential risk factors for AVB subsidence remaining unknown. This study aimed to identify the risk factors for early subsidence of AVB after single-level anterior cervical corpectomy and fusion (ACCF).

Methods: Consecutive patients who underwent single-level ACCF using 3D-printed AVB for cervical spondylotic myelopathy between 2018 and 2022 were included. Preoperative, immediate postoperative, and 3-month postoperative X-ray scans were evaluated. Radiological assessment included segmental height (SH), intraoperative retraction height, cervical alignment parameters, bone quality and implant sagittal size ratio. Early subsidence was defined as an SH loss ≥ 2 mm based on 3-month radiographs.

Results: Of the included 98 patients (52 males, 46 females, average age: 51.8 ± 10.1), 35(35.7%) experienced early subsidence. The subsidence group exhibited significantly higher age, segmental sagittal vertical axis, cervical lordosis, C7 slope, and segmental slope, alongside lower implant sagittal size ratio. Correlation analysis revealed that SH loss is significantly positively correlated with intraoperative retraction height, segmental SVA, C7 slope, segmental slope, and negatively with the ratio of implant sagittal diameter compared to vertebra. Forward multivariable logistic regression indicated that greater age (p = 0.029), intraoperative retraction height (p < 0.001), and segmental slope (p = 0.006) were significant risk factors, while a higher implant sagittal size ratio (p = 0.004) was a protective factor against AVB subsidence.

Conclusions: Increased age, segmental slope, intraoperative retraction height, and a lower implant sagittal size ratio are significant risk factors for AVB subsidence. Surgeons should consider these factors in surgery planning and avoid excessive intraoperative retraction.