Case series study and finite element analysis of a new cervicothoracic fixation device

To introduce a specialized device designed for the fixation of the cervical-thoracic spine and describe its surgical installation, finite element analysis, and clinical outcomes.

A finite element model of the C₆-T₁ segment was developed and validated, and simulations of subtotal resection of anterior cervical vertebrae, artificial vertebrae placement, and titanium plate fixation were performed. The model was subjected to a 75 N load to simulate the weight of the head and a 1 N·m force to simulate flexion, lateral bending, and axial rotation. The analysis focused on range of motion, total stress, stress in the artificial vertebrae, and stress in the device. The clinical outcomes were evaluated in a retrospective case series of 140 patients with cervical spine fractures.

Under the same loading conditions, the maximum stresses on specialized anatomical and biomechanical devices for the fixation of the cervicothoracic segment of the spine during neutral, forwards flexion, backwards extension, left lateral bending, right lateral bending, left rotation, right rotation and other working conditions were 25.097 MPa, 149.480 MPa, 64.150 MPa, 67.804 MPa, 72.754 MPa, and 117.98 MPa, respectively. And, the maximum ROMs were 2.230 mm, 5.585 mm, 4.682 mm, 3.184 mm, 3.061 mm, 4.451 mm, and 4.645 mm. Compared with those in the preoperative period, the patients' CL, OPCL, UCL, LCL, UROM, LROM, VAS score, NDI score, JOA score, intervertebral space height at the injured segment, cervical anterior kyphosis angle, Cobb angle, vertebral displacement, ASIA grade, fracture classification, and vertebral displacement improved (P < 0.05). Sixty-two patients had dysphagia, and 3 patients experienced leakage of cerebrospinal fluid.

The design of the new cervicothoracic internal fixation device conforms to the anatomical structure of the cervicothoracic spine, which can provide immediate stability, better screw placement and adequate bone grafting, and reduce the risk of complications. Despite some disadvantages, it is a good device for segmental fixation of the cervical and thoracic spine.