Static and Fatigue Load Bearing Investigation on Porous Structure Titanium Additively Manufactured Anterior Cervical Cages.

This study investigates the static and fatigue behavior of porous and conventional anterior cervical cages. Porous structure titanium anterior cervical cages were manufactured using direct selective laser sintering technique. Four different types of cervical cages were designed and manufactured, among which three designs consist of porous structure (type 1, type 2, and type 3) and manufactured using metal 3D printing. Remaining one design (type 4) was manufactured using conventional machining and did not consist any porous structure. All types of manufactured cages were tested in compression under static and fatigue loading conditions as per ASTM F2077 standard. Static and fatigue subsidence testing was performed using ASTM F2267 standard. Static compression testing results of type 1 and type 4 cages reported higher yield load when compared to the type 2 and type 3 cages. Static subsidence testing results reported almost 11% less subsidence rate for additively manufactured cages than the conventional cages. Fatigue subsidence testing results showed that type 2 and type 3 cages can withstood approximately 21% higher number of cycles before subsidence as compare to the type 1 and type 4 cages. During fatigue testing, all the cages design survived 5 million cycles at the 3000 N loading. For 6000 N and 8000 N, loading rate type 2 and type 3 cages showed lower fatigue life when compared to other cages design. Since fatigue life of type 2 and type 3 cage designs were reported lower than other cages design, it is concluded that the performance of the additively manufactured porous cages can be significantly varied based upon the cage design features.