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D cervical disease is among the most common age-related disorder encountered in the general population, with over a quarter of patients ultimately failing conservative management and progressing to surgical intervention.1 The constellation of disc herniation, osteophyte formation, and superimposed canal stenosis can lead to a host of neurological consequences, including radiculopathy, paresthesias, weakness, and myelopathy. The anterior approach to the vertebral column for discectomy and fusion was first described by Cloward in the 1950s and is now the most common procedure used to treat cervical spondylosis. In the decades since, leaping advances have been made through variations in technique and technology. Arguably the key component of these surgeries is the selection of interbody graft material, which ultimately dictates height distraction, load-bearing stability, and fusion potential. The gold standard for interbody fusion is tricortical autologous bone graft, usually harvested from the iliac crest. However, due to well-documented harvest-site complications, including hematoma, infection, chronic pain, and progressive pelvic fractures, surgeons have sought other less-invasive options for grafting. The 1980s saw significant advances in sterilization processes and bone-banking protocols paving the way for allograft bone from cadavers, as well as the development of synthetic material interbody cages. These autologous bone graft substitutes circumvent harvest-site complications and additional operative time, but remain inferior to autologous bone based on inherent fusion principles. These include osteogenesis, osteoinduction, osteoconduction, and osseointegration. Osteogenesis refers to de novo bone growth; osteoinduction refers to the ability to stimulate osteoblast precursor differentiation; and osteoconduction refers to the ability to provide scaffolding for which osteogenesis to occur. The concerted efforts of these properties dictate the degree of osseointegration, which is the incorporation of the graft material with native bone. Both cadaveric allografts and interbody cages lack osteogenic properties due to their acellular makeup, yet are highly osteoconductive based on their structural profile. In many allografts and interbody cages, hollow cores within the spacers can be filled with morselized autograft, demineralized allograft bone matrices, synthetic ceramics, or new generation “biologics” such as recombinant human bone morphogenetic proteins to stimulate their osteoinductive properties. Both allograft and interbody cages have demonstrated 91%–100% fusion rates in various trials with minimal radiographic and clinical complications.2–4 Despite these similarities, subtle differences exist among these groups that limit their utility in certain cases. As with implantation surgeries, structural allografts are harvested under aseptic conditions, and both donors and grafts go through rigorous screening processes evaluating for microbial pathogens before storage. However, these laborious steps do not completely eliminate all possible contaminants that can potentially lead to allograft disease transmission. For example, a study by Barriga et al5 found 12% of allografts contained positive bacterial cultures immediately before implantation which had tested negative for all infectious pathogens before storage. Although none of these findings resulted in clinical signs of infection in any patient, it raises the issue of nondetectable contamination during harvesting, and posits questions with regard to the standardized protocols for storage and handling to the operating room. These results may not be as widely applicable in present-day, developed countries, yet the patient perception of transmissible diseases from harvested cadaveric bone persists, and furthermore presents challenges with groups who refuse to accept donated tissues for religious or cultural reasons. In a similar regard, the sterilization process for harvested allograft often involves gamma irradiation. This process has been shown to degrade collagen in the bone matrix in an inconsistent manner from graft to graft, and thus structural allografts demonstrate higher rates of pseudarthrosis and graft collapse.6 Interbody cages, in contrast, have witnessed accelerated development over the past 20 years concomitant with advances in material science engineering and growing Received for publication August 7, 2016; accepted June 19, 2018. From the Department of Neurological Surgery, New York Presbyterian Hospital, Weill Cornell Medical College, New York, NY. A.A.B. declares royalties from Thieme Publishers. The authors declare no conflict of interest. Reprints: Ali A. Baaj, MD, Department of Neurological Surgery, New York Presbyterian Hospital, Weill Cornell Medical College, 525 East 68th Street, New York, NY 10065 (e-mail: [email protected]. edu). Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved. CONTROVERSIES IN SPINE SURGERY