The design and biomechanical study of the 3D-printed implanted cervical vertebral cage

An in vitro biomechanical study was conducted to assess the immediate postoperative stability and compressive stiffness of monosegment slot-expansion decompression with implantation of a novel 3D-printed implanted cervical vertebral cage. A comparative analysis was performed against traditional anterior cervical discectomy and fusion (ACDF) constructs and partial vertebrectomy with cage implantation. The objective was to provide biomechanical validation for the rationale and efficacy of the 3D-printed implanted cervical vertebral cage in clinical use.

Fifteen fresh goat cervical spine specimens were divided into five groups: (1) intact control, (2) discectomy-only, (3) traditional ACDF cage, (4)partial corpectomy with traditional cage, (5) slot-expansion decompression with 3D-printed implanted cervical vertebral cage. Range of motion (ROM) was measured under 2.0 N·m loading in flexion, extension, lateral bending, and axial rotation. Axial compressive stiffness was assessed under vertical loads (50 N, 100 N, 150 N, 200 N).

The 3D-printed implanted cervical vertebral cage group exhibited slightly lower flexion ROM than traditional ACDF and vertebral endplate resection group, though statistically insignificant (P > 0.05). Extension ROM was marginally reduced compared to intact and ACDF groups, though statistically insignificant (P > 0.05), similar to the partial corpectomy group (P > 0.05). Lateral bending ROM and rotation ROM showed no intergroup differences (P > 0.05). All surgical groups demonstrated higher compressive stiffness than the intact spine (P < 0.05). Under physiological loads (around 50 N), the 3D-printed implanted cervical vertebral fusion cage's stiffness matched traditional ACDF (P > 0.05); at higher loads (> 100 N), it was lower than ACDF (P < 0.05) but remained superior tovertebral partial corpectomy group (P < 0.05).

This study demonstrates that the 3D-printed implanted cervical vertebral cage, used with monosegmental slot-expansion decompression, provides a biomechanical stability profile comparable to traditional ACDF, while offering greater subsidence resistance than partial corpectomy. These biomechanical findings suggest that the novel 3D-printed cage design may serve as a stable alternative for slot-expansion decompression. Further in vivo and clinical studies are warranted to confirm its long-term performance.