Comparison of osseointegration in 3D-printed hexanium titanium cages and PEEK cervical cages: In-vivo ovine cervical fusion model.

Purpose: To evaluate intervertebral cage migration and bony ingrowth in 3D printed additive manufacturing titanium cages with hexagonal geometry in the cage walls and traditional PEEK anterior cervical cages using an in-vivo ovine model.

Materials And Methods: A comparative animal study was performed. 3D-printed titanium and PEEK interbody cages were implanted in eight ovine cervical spines without fixation. After 8 weeks, animals underwent a full body CT-scan and at 12 weeks, a micro-CT scan and histological sections were performed to qualitatively assess (i) the cage position (ii) the ratio of bone ingrowth inside the cage central window in terms of area and volume and (iii) the osseointegration inside the 3D-printed titanium complex geometry.

Results: Within the central window of the cages, the mean percentage of bone area/total area for the PEEK and 3D-printed titanium groups was 3.79 ± 7.26 and 10.46 ± 8.52, respectively (p-value = 0.086). The mean percentage of bone volume/total volume for PEEK and 3D-printed titanium groups was 7.83 ± 6.65 and 20.53 ± 14.56 respectively (p-value = 0.018). Histological results showed a similar trend with bone ingrowth. Implant migration was observed more frequently in PEEK (87.5%) than in 3D-printed titanium cages (37.5%).

Conclusions: 3D-printed titanium cages showed significantly increased bone formation in an in-vivo ovine model under suboptimal conditions. We suspect that the early osseointegration in the hexagonal geometry in the cage walls may contribute to decreased cage migration. However, further studies are necessary to confirm the findings of this preliminary study.