Porous titanium-6 aluminum-4 vanadium cage has better osseointegration and less micromotion than a poly-ether-ether-ketone cage in sheep vertebral fusion.

Interbody fusion cages made of poly-ether-ether-ketone (PEEK) have been widely used in clinics for spinal disorders treatment; however, they do not integrate well with surrounding bone tissue. Ti-6Al-4V (Ti) has demonstrated greater osteoconductivity than PEEK, but the traditional Ti cage is generally limited by its much greater elastic modulus (110 GPa) than natural bone (0.05-30 GPa). In this study, we developed a porous Ti cage using electron beam melting (EBM) technique to reduce its elastic modulus and compared its spinal fusion efficacy with a PEEK cage in a preclinical sheep anterior cervical fusion model. A porous Ti cage possesses a fully interconnected porous structure (porosity: 68 ± 5.3%; pore size: 710 ± 42 µm) and a similar Young's modulus as natural bone (2.5 ± 0.2 GPa). When implanted in vivo, the porous Ti cage promoted fast bone ingrowth, achieving similar bone volume fraction at 6 months as the PEEK cage without autograft transplantation. Moreover, it promoted better osteointegration with higher degree (2-10x) of bone-material binding, demonstrated by histomorphometrical analysis, and significantly higher mechanical stability (P < 0.01), shown by biomechanical testing. The porous Ti cage fabricated by EBM could achieve fast bone ingrowth. In addition, it had better osseointegration and superior mechanical stability than the conventional PEEK cage, demonstrating great potential for clinical application.

A polycaprolactone-tricalcium phosphate composite scaffold as an autograft-free spinal fusion cage in a sheep model.

Titanium (Ti) based spinal fusion cages are frequently used in the clinics for the treatment of spinal degeneration and related diseases, however, their further clinical application is generally harassed by several drawbacks such as stress shielding, non-biodegradability and additional bone grafting procedure. Our earlier work has demonstrated the efficacy of a biodegradable macro-porous polycaprolactone-tricalcium phosphate (PCL-TCP) composite scaffold in promoting bony tissue ingrowth as well as its ability to sustain mechanical loads upon implantation into an orthotopic defect site. In this study, we investigated the use of PCL-TCP scaffold as an autograft-free spinal fusion cage in a preclinical sheep model over 12 months, and compared the fusion efficacy against Ti cages incorporated with autografts. Results showed that despite PCL-TCP scaffold as an autograft-free cage attaining a slower fusion rate at early stage (6 month), it achieved similar degree of spinal fusion efficacy as Ti cages aided with autograft at 12 month post-operation as evidenced by the radiographic and histological evaluation. PCL-TCP cages alone demonstrated better bone ingrowth with 2.6 fold higher bone/interspace ratio (B/I) and more homogeneous bone tissue distribution compared with that of the Ti cages (88.10  ±  3.63% vs. 33.74  ±  2.78%, p < 0.05) as seen from the histological and micro-CT analysis. Moreover, besides the bone tissue ingrowth, a quantitative approach was illustrated to accurately evaluate the osteointegration of fusion cage with surrounding bone tissue, and showed a 1.36 fold higher degree of osteointegration occurred in PCL-TCP cage group than Ti cage group (CS/PC: 79.31  ±  3.15% vs 58.44  ±  2.43%, p < 0.05). Furthermore, biomechanical analysis showed comparable mechanical strength of fused segments in both groups in terms of the range of motion and stiffness at 12 month (p > 0.05). The degradation profile of the PCL-TCP cages was noted to increase in tandem with new bone ingrowth into the pores, while maintaining good structural integrity necessary for supporting the spinal interbody segments. Therefore, with the better osteointegration, more bone tissue ingrowth as well as its favorable biodegradable and radiolucent properties, PCL-TCP cage has been demonstrated to be a promising candidate as an autograft-free fusion cage for clinical application.

The treatment effect of porous titanium alloy rod on the early stage talar osteonecrosis of sheep.

Osteonecrosis of the talus (ONT) may severely affect the function of the ankle joint. Most orthopedists believe that ONT should be treated at an early stage, but a concise and effective surgical treatment is lacking. In this study, porous titanium alloy rods were prepared and implanted into the tali of sheep with early-stage ONT (IM group). The curative effect of the rods was compared to treatment by core decompression (DC group). No significant differences in bone reconstruction were observed between the two groups at 1 month after intervention. After 3 months, the macroscopic view of gross specimens of the IM group showed ordinary contours, but the specimens of the DC group showed obvious partial bone defects and cartilage degeneration. Quantitative analysis of the reconstructed trabeculae by micro-CT and histological study suggested that the curative effect of the IM group was superior to that of the DC group at 3 months after intervention. These favorable short-term results of the implantation of porous titanium alloy rods into the tali of sheep with early-stage ONT may provide insight into an innovative surgical treatment for ONT.