A novel design of an expandable cage used in posterior interbody fusion for lumbar spine surgery

Spinal fusion surgery is applied to permanent joining two or more vertebrae to solve uncontrollable human low back pain when physical therapy is helpless. An interbody fusion cage is a prosthesis used in spine fusion procedures to maintain foraminal height and decompression. We have designed and constructed the prototype expandable cage to be used in posterior lumbar interbody fusion (PLIF) surgery. Protocol of implanting the expandable cage was investigated via in Vitro simulation to examine its feasibility and stability. Repeating stress analysis was applied to the mechanisms and then layouts correction before metal manufacture. According to the analysis, the maximum stress of the cage is less than the yielding stress of the material, briefly conclude that our design is stress allowance.