Failure of a Carbon Fiber–Reinforced Polymer Implant Used for Transforaminal Lumbar Interbody Fusion

摘要

Lumbar interbody fusion is a common procedure owing to the high prevalence of degenerative spinal disorders. During such procedures, carbon fiber–reinforced polymer (CFRP) cages are frequently utilized to fill the void created between adjacent vertebral bodies, to provide mechanical stability, and to carry graft material. Failure of such implants can lead to significant morbidity. We discuss the possible causes leading to the failure of a CFRP cage in a patient with rheumatoid arthritis. Review of a 49-year-old woman who underwent revision anterior lumbar interbody fusion 2 years after posterior instrumentation and transforaminal lumbar interbody fusion at L4–L5 and L5–S1. The patient developed pseudarthrosis at the two previously fused levels with failure of the posterior instrumentation. Revision surgery reveled failure with fragmentation of the CFRP cage at the L5–S1 level. CFRP implants can break if mechanical instability or nonunion occurs in the spinal segments, thus emphasizing the need for optimizing medical management and meticulous surgical technique in achieving stability. Keywords: carbon fiber–reinforced polymer, cage failure, nonunion, rheumatoid arthritis Lumbar interbody fusion procedures, such as posterior lumbar interbody fusion and transforaminal lumbar interbody fusion (TLIF), are performed commonly nowadays due to the high prevalence of degenerative spinal conditions. These procedures involve removing the disk material and cartilaginous end plates from the involved intervertebral disk space and filling up the void with a spacer to maintain disk height and to decompress the neural foramina. Choices for the spacer include structural allograft, structural autograft, or synthetic cages that can be packaged with graft material. Such synthetic cages are meant to offer immediate rigid structural support while carrying bone graft that would result in osseous fusion between the two vertebral bodies. 1 2 3 One such cage used in TLIF procedures is made of carbon fiber–reinforced polymer (CFRP; Leopard, Depuy, Raynham, MA, USA) and has two chambers for insertion of bone graft. It has a modulus of elasticity approximating that of cortical bone and has four tantalum beads to visualize cage position on radiographs. Because of the ability to carry autologous bone graft, high rates of fusion with the CFRP cages have been reported in literature without much implant-related complications. 1 3 4 5 6 To our knowledge, there has been only one reported case of CFRP cage failure in the literature. 7 We report here another case of a CFRP cage failure.