Reconstruction of Segmental Stability of Goat Cervical Spine with Poly (D, L-lactic acid) Cage

To compare the characteristics of inter body fusion after using an established poly (D, L-lactic acid) (PDLLA) cage, a titanium cage or autologous tricortical iliac crest graft in a goat cervical spine model in vivo.

Twenty-four goats were assigned to three groups: PDLLA cage group (n = 8), titanium alloy cage group (n = 8) and autologous iliac bone group (n = 8), and underwent C3-4 discectomy and fusion with the allocated procedure. Radiography was performed pre- and post-operatively and after 1, 2, 4, 8 and 12 weeks and disc space height (DSH), intervertebral angle (IVA), and lordosis angle (LA) measured at these time points. After 12 weeks, the goats were killed and fusion sites removed. Biomechanical testing was performed in flexion, extension, axial rotation, and lateral bending to determine the stiffness and range of motion (ROM). All specimens were also assessed histomorphologically.

The IVA of PDLLA cage four weeks postoperatively and DSH eight and twelve weeks postoperatively were significantly greater than that of autologous iliac bone graft (P < 0.05). The LA values did not differ significantly between groups. The stiffness of both types of cages for axial rotation and lateral bending, and ROM for every movement, were significantly greater than that of the autologous iliac bone graft group (P < 0.05). PDLLA and titanium cages did not differ significantly (P > 0.05). Radiographic and histomorphological assessment showed better fusion in the cage than the autologous bone groups.

The PDLLA cage can provide good intervertebral distract ability and enough biomechanical stability for cervical fusion.