For anterior cervical arthrodesis, surgeon preference determines which of many different bone substrates can be used with instrumentation, which impacts the costs. Fusion substrates include structural autografts, structural allografts, morselized autografts, morselized allografts, demineralized allografts, porous ceramics and metals, and BMP. Given these many options, studies comparing the constructs are lacking, especially with regard to the cost of alternative fusion constructs that produce similar outcomes. The Centers for Disease Control and Prevention defines cost-benefit analysis as a “type of economic evaluation that measures both costs and benefits (ie, negative and positive consequences) associated with an intervention in dollar terms.”22 It has been reported that using iliac crest autografts with anterior plate instrumentation is the most cost-effective method, yet alternatives remain in use.5,10
For ACDF, iliac crest bone is an ideal and widely used construct substrate. Structural grafts harvested from the crest provide significant stability due to their bicortical or tricortical configuration with interposed osteoinductive and osteogenic cancellous bone. Few graft complications (eg, graft resorption) and no immunogenic or infectious complications have been reported for iliac crest bone. However, autologous iliac crest increases operative time, and donor-site morbidity has been reported.23,24 A retrospective questionnaire-based investigation by Silber and colleagues, who evaluated iliac crest bone graft site morbidity in 1-level ACDF, found that 26.1% of patients had pain at the iliac crest harvest site, and 15.7% had numbness.24 Other complications, which occurred at lower rates, were bruising, hematoma, pelvic fracture, and poor cosmesis.23,25 In addition, osteoporosis and comorbid conditions have made it a challenge to acquire iliac crest autograft, contributing to the popularity of alternative substrates.25
Allografts
An alternative to autografts, allografts have the advantages of reduced operative time and reduced donor-site morbidity.26 Major historical concerns with allografts have included risk for disease transmission, costs associated with sterilization and serologic screening of grafts, and lack of oversight, leading to human allografts being acquired from dubious sources and ending up in the operating room.27,28 Two major types of allografts are available: mineralized and demineralized.
Arthrodesis rates are inferior for mineralized (structural) allografts with instrumentation than for autografts with instrumentation.29 In addition, smoking and other comorbidities have influenced fusion rates more in allograft than autograft fusions.30-33 However, allografts are being widely used because they avoid the donor-site morbidity associated with autografts and because they are load bearing, can provide structural stability and an osteoconductive matrix, and can be used off the shelf without adding much time to surgery.
Demineralized matrix substrates are commercial osteoconductive and osteoinductive biomaterials approved for filling bone gaps and extending graft when combined with autograft.7,8 Despite their osteoinductive properties, these substrates have had a high degree of product inconsistency, in some cases leading to poor outcomes.34 The lack of randomized studies with these constructs has made the determination of clear indications a challenge.
The initial enthusiasm over use of BMP, another bone-graft substitute for cervical fusion, was curtailed by reports of adverse events (AEs). Effective in anterior lumbar spine fusions, BMP was adapted to off-label use in the cervical spine a few years ago.35 Initial studies by Baskin and colleagues and Bishop and colleagues showed its fusion rates superior to those of allograft.31,32 Both studies reported no significant AEs. However, studies by Dickerman and colleagues and Smucker and colleagues demonstrated increased soft-tissue swelling leading to dysphagia and prolonged hospitalization, which were attributed to higher dosage (no study has identified a precise dose for individual patients).36,37 In addition, the cost of BMP is higher than that of any other bone-graft option for ACDF.3 Osteolysis has also been reported with BMP use.38-40 Carragee and colleagues highlighted the potential carcinogenicity of BMP, but this finding was not corroborated by Lad and colleagues.41,42
Cost Considerations
In addition to surgical effectiveness, spine surgical device costs have come under increased scrutiny.43-45 In 2012, plates were reported to cost (without overhead or profit margin to hospitals) between $1,015 and $3,601, and allograft spacers were estimated to cost between $1,220 and $3,640, cage costs ranged from $1,942 to $4,347, and PEEK spacers cost from $4,930 to $5,246.5 Individual surgeon instrumentation costs varied 10-fold based on the fusion constructs used.5
In a cost-effectiveness review of anterior cervical techniques, cage alone was the least expensive technique, disc arthroplasty or cage/plate/bone substitute groups were the next most expensive, and autograft alone was the most expensive option due to hip graft site morbidity.43 In another study, operative time associated with harvesting an iliac crest graft was equivalent in cost to that of an interbody cage.44 Other studies have compared the costs of various anterior cervical fusion constructs.9,10,45,46 A limitation of these studies is that autologous bone often refers to iliac crest grafts rather than local autograft. Epstein reviewed data from these studies and concluded, “ACDF using dynamic plates and autografts are the most cost effective treatment for anterior cervical discectomy,” citing a cost of $1,015 for this construct.5 Although Epstein demonstrated the cost-effectiveness of autograft in an individual surgeon’s hands, the results also are significant in that the studies identified areas in which improvements can be made at other institutions. The ROI-C cervical cage and local autograft bone cost that the authors report is at the lower end of the range reported by Epstein.5
