An interbody fusion cage (colloquially known as a "spine cage") is a

prosthesis In medicine, a prosthesis (: prostheses; from ), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through physical trauma, disease, or a condition present at birth (Congenital, congenital disord ...

used in

spinal fusion Spinal fusion, also called spondylodesis or spondylosyndesis, is a surgery performed by Orthopedic surgery#Practice, orthopaedic surgeons or neurosurgeons that joins two or more vertebrae. This procedure can be performed at any level in the spine ...

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 Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...

; the Brantigan cage, made from

carbon fibre Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers ( Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon comp ...

; and the Cortical Bone Dowel, which is cut from allograft

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

. The cages can be packed with autologous bone material in order to promote

arthrodesis Arthrodesis, also known as artificial ankylosis or syndesis, is the artificial induction of joint ossification between two bones by surgery. This is done to relieve intractable pain in a joint which cannot be managed by pain medication, splin ...

. 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. 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.

References

Further reading