Biomechanical Test of the Stability of a Cervical Interfacet Self-Locking Cage

Purpose: To compare the biomechanical properties of a novel 3D-printed cervical interfacet self-locking cage (CISC) using medical titanium alloy (Ti-6Al-4V) material with the lateral mass screw–rod system. Methods: CT scans were performed on seven preserved human cervical spine specimens (C2–T1) to exclude deformities, infections, tumors, fractures and other lesions, and titanium CISCs were 3D-printed based on the CT scan data. A moment of 1.5 Nm was applied to the specimen using a biomechanics machine. The range of motion (ROM) in bending, extension, lateral bending and rotation directions of each specimen in the different groups was measured, including an intact group (group A), a C5–C6 posterior ligamentous complex (PLC) resection group (group B), a C5–C6 lateral mass screw–rod system fixation group (group C), and a C5–C6 novel CISC fixation group (group D). Results: Groups C and D had smaller ROM than groups A and B in flexion–extension, lateral bending and rotation directions, and the difference was statistically significant ( P < 0.05). Group D had significantly greater ROM than group C in the forward flexion and posterior extension directions ( P < 0.05). Conclusions: Injury to the posterior ligament complex of the lower cervical spine can cause flexion and extension, lateral bending, and instability in the direction of axial rotation. CISC fixation is equivalent to the fixation effect of the lateral mass screw-rod system, and can be used as a simple fixation or supplementary fixation for the posterior cervical spine.