The human spine carries the weight of the trunk,upper extremities,and head,and provides an extensive range of motion.Due to heavy use and lack of vasculature,the intervertebral discs degenerate much more rapidly than other structures of the human body.12Intervertebral disc degeneration is mostly age-related,and spinal disorders associated with disc degeneration have a significant impact on society.3,4 Indeed,low back pain affects nearly three-quarters of the population sometime in their life.3 Surgical strategies for treatment of disc degenerative disease (DDD) include removal of pathological discs and fusion of intervertebral bodies or facet joints with or without instrumentation.Spinal fusion enhances the stability of the spine and decreases the formation of pseudo-unions;however,this procedure is also associated with breakage or loosening of the instruments and acceleration of adjacent segment degeneration.4,5 As an alternative to disc fusion,artificial disc (AD) replacement using a disc prosthesis results in a greater degree of segment motion.68 Complications of AD include periprosthetic ossification,neurological deficit,prosthetic looseness or breakage,and even cervical kyphosis.8 Since conservative methods for treatment of DDD eventually fail and surgical interventions have significant drawbacks and complications,non-operative (biological) strategies such as growth factor injection,stem cell transplantation,and gene therapy have begun to receive more attention.4。
