Interbody fusion cage

An interbody fusion cage (colloquially known as a "spine cage") is a prosthesis used in spinal fusion procedures to maintain foraminal height and decompression. They are cylindrical or square-shaped devices, and usually threaded. There are several varieties: the Harms cage, Ray cage, Pyramesh cage, InterFix cage, and lordotic LT cage, all of which are made from titanium; the Brantigan cage, made from carbon fibre; and the Cortical Bone Dowel, which is cut from allograft femur. The cages can be packed with autologous bone material in order to promote arthrodesis.[1] Such implants are inserted when the space between the spinal discs is distracted, such that the implant, when threaded, is compressed like a screw. Unthreaded implants, such as the Harms and Pyramesh cages have teeth along both surfaces that bite into the end plates.[1]

X-ray of interbody fusion cage in cervical vertebrae, Juliet system.

X-ray of interbody fusion cage in L5S1 vertebrae.

Technology: expansion vs. static devices Expandable implant devices are at the forefront of technology in this field, with cages that expand in place for optimal end-plate-to-endplate fit and correction of lordosis. There are several technologies for cage expansion; FLXfit by Expanding Orthopedics offers a unique and patented 3D articulation and lordotic expansion, Staxx by Spinewave stacks plates as risers, Varilift by Wenzel - uses a screw device for enlargement and AccuLIF by CoAlign, which has a unique locking hydraulic solution for precise expansion. FlareHawk by Integrity Implants uses stent-like technology, expanding in width, height, and lordosis.

Once placed, the cages resist flexion and extension of the spine, and axial forces across the ventral and middle columns.[1]