With regard to xenografts complications commonly

With regard to xenografts, complications commonly reported are an immunologic response surrounding the graft, collapse of the graft before fusion, poor osseointegration or fusion, and disease transmission. Espersen et al while reviewing 1106 patients found that although functional results equivalent to those of an autograft were achieved, xenografts were associated with increased rates of reoperation. The allograft is another commonly used alternative to autografts and has advantages such as the avoidance of donor-site morbidity, greater supply, and a reduced operating time. Nevertheless, allograft substrates are difficult to standardize, given the heterogeneity of the donor population. Consequently, synthetic bone substitute materials have been developed to deal with concerns regarding disease transfer, limitations of supply, and inconsistency. Calcium phosphate ceramics, tricalcium phosphate (TCP) and hydroxyapatite (HA), are the most widely evaluated of these materials for use in the cervical spine. Generally, TCP and HA achieve acceptable fusion rates and clinical outcomes at a reasonable price. However, HA is usually considered nonabsorbable, and the persistence of the graft material can be linked to some poor clinical outcomes. By contrast, porous TCP scaffolds are stated to have high rates of cell- and chemically medicated dissolution, which may cause adverse biological reactions to the scaffolds by microparticle-induced purinergic receptors and surface instability. Another bioceramic that can be used for bone-graft substitutes is calcium sulfate. Calcium sulfate has been successfully used in long-bone defects, and defects in the calvaria and the mandible. Furthermore, it has been used as a carrier in various studies for the in vitro elution of a variety of antimicrobials, including vancomycin, teicoplanin, clindamycin, gentamicin, and daptomycin. Although many studies have investigated the effectiveness of these substrates, there is no current option that is conclusively superior to an autograft. High rates of nonunion and graft collapse have been controversial issues in the use of allografts and bone substitutes for ACDF. Synthetic interbody cages have been developed both to achieve an immediate stability and successful bone fusions. Titanium- or carbon-fibered cages were widely used for cervical interbody fusion. However, subsidence, migration, and structure failure have occurred from using these cages. Radiologic assessment of fusion is difficult for each of these two materials. Despite the advantage of radiolucency, carbon cages have been associated with a high rate of pseudarthrosis due to mechanical stress-shielding of the cage and decreased bone-to-bone contact. Polyetheretherketone (PEEK), which is a nonabsorbable biopolymer that has been used in a variety of industries, including medical devices, is biocompatible and radiolucent. The modulus of elasticity of PEEK is similar to that of bone. This distinguishing feature is thought to prevent the cage subsidence induced by metallic cages. The PEEK cages, unlike Trabecular Metal cages, are not osteoinductive, and therefore, require an agent to promote fusion. The hollow center of the PEEK cages provides a spacer for fusion materials that is integral to achieving a successful fusion.
Materials and methods
Results Twenty-four patients underwent an ACDF. All patients were followed up for at least 1 year (mean: 16.9; range: 12–30 months). Twenty-one patients underwent a single-level ACDF and three patients had a two-level ACDF, for a total of 27 levels. C5–6 was the most common (15/24) level of disc surgery in autotrophic series. The mean age was 50.9 years (range: 23–77 years). The demographic data of patients are shown in Table 2.
Discussion Bone grafts and their artificial substitutes have been commonly used for this purpose at the site of arthrodesis. Chau and Mobbs reviewed articles and compared the clinical outcomes, fusion rates, and complications of individual bone-graft substitutes. Packing different bone-graft substitutes in the hollow center of the PEEK cage has been discussed in various studies recently. Boakye et al reported results obtained in 24 patients with cervical disc disease who had undergone an ACDF involving the placement of PEEK cages filled with recombinant human bone morphogenetic protein (rhBMP-2) and anterior plating. The radiographic fusion rate was 100%. Cho et al compared the results of 40 patients who underwent an ACDF with PEEK spacers filled with an autogenous iliac cancellous bone graft and a comparable group in which the patients underwent ACDF with autogenous tricortical iliac crest graft. A complete fusion rate occurred in 100% of the patients with autogenous iliac cancellous bone grafts and in 93% of those with tricortical iliac crest grafts. Liao et al reported the results obtained in 19 patients who underwent an ACDF with the replacement of the cancellous allograft bone, which was harvested from the femoral condyle during a total knee arthroplasty, and embedded in the PEEK cage. The fusion rate was 100%. Park et al enrolled 31 patients with spondylotic cervical disease who received an ACDF with the placement of a PEEK cage packed with a putty form of demineralized bone matrix (DBM, Grafton; Osteotech Inc., Shrewsbury, NJ, USA) mixed with autologous bone chips obtained from anterior and posterior bony spurs. A total of 97% of patients demonstrated radiographic fusion.