Management of strut graft failure in anterior cervical spine surgery

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Although successfully used, long strut grafts are vulnerable to dislodgment, displacement, fracture, and nonunion, which can require revision surgery; thus, meticulous preparation of the vertebral endplate along with exact sizing and harvesting of the bone graft with plating are essential for successful outcomes. Biomechanical data and previous clinical studies support the addition of posterior fusion and fixation following multilevel (more than two-level) corpectomy. The additional posterior instrumentation moves the instantaneous axis of rotation posteriorly, thus approximating its normal location in the posterior vertebral body (VB). Biomechanically, this protects the graft from excessive loads while in extension and explains the clinical success of circumferential instrumentation for long-segment corpectomy reconstructions. If strut fracture occurs with minimal displacement and the graft position is still satisfactory, application of a halo vest and judicious observation are recommended. Significant displacement, kyphosis, or loss of contact of the graft and VB require revision surgery. In patients requiring revision surgery for nonunion, placement of fibular autograft or allograft with use of bone morphogenetic protein is likely to be beneficial. If questions remain regarding bone quality or construct stability, the supplemental use of posterior stabilization is recommended. Various surgical approaches have been advocated for treatment of symptomatic anterior cervical pseudarthroses or nonunion. It remains controversial as to whether the anterior or posterior approach is best. Adequate understanding of the graft and implant biomechanics are essential for a successful outcome.

Abbreviations used in this paper:ACDF = anterior cervical discectomy and fusion; CT = computerized tomography; MR = magnetic resonance; VB = vertebral body.

Although successfully used, long strut grafts are vulnerable to dislodgment, displacement, fracture, and nonunion, which can require revision surgery; thus, meticulous preparation of the vertebral endplate along with exact sizing and harvesting of the bone graft with plating are essential for successful outcomes. Biomechanical data and previous clinical studies support the addition of posterior fusion and fixation following multilevel (more than two-level) corpectomy. The additional posterior instrumentation moves the instantaneous axis of rotation posteriorly, thus approximating its normal location in the posterior vertebral body (VB). Biomechanically, this protects the graft from excessive loads while in extension and explains the clinical success of circumferential instrumentation for long-segment corpectomy reconstructions. If strut fracture occurs with minimal displacement and the graft position is still satisfactory, application of a halo vest and judicious observation are recommended. Significant displacement, kyphosis, or loss of contact of the graft and VB require revision surgery. In patients requiring revision surgery for nonunion, placement of fibular autograft or allograft with use of bone morphogenetic protein is likely to be beneficial. If questions remain regarding bone quality or construct stability, the supplemental use of posterior stabilization is recommended. Various surgical approaches have been advocated for treatment of symptomatic anterior cervical pseudarthroses or nonunion. It remains controversial as to whether the anterior or posterior approach is best. Adequate understanding of the graft and implant biomechanics are essential for a successful outcome.

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Address reprint requests to: Daniel H. Kim, M.D., Department of Neurosurgery, Stanford University Medical Center, Room R-201, Edwards Building, 300 Pasteur Drive, Stanford, California 94305-5327. email: neurokim@stanford.edu.

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