Subsidence and Nonunion after Anterior Cervical Interbody Fusion Using a Stand-Alone Polyetheretherketone (PEEK) Cage

Abstract

BackgroundThe purposes of the present study are to evaluate the subsidence and nonunion that occurred after anterior cervical discectomy and fusion using a stand-alone intervertebral cage and to analyze the risk factors for the complications.MethodsThirty-eight patients (47 segments) who underwent anterior cervical fusion using a stand-alone polyetheretherketone (PEEK) cage and an autologous cancellous iliac bone graft from June 2003 to August 2008 were enrolled in this study. The anterior and posterior segmental heights and the distance from the anterior edge of the upper vertebra to the anterior margin of the cage were measured on the plain radiographs. Subsidence was defined as ≥ a 2 mm (minor) or 3 mm (major) decrease of the segmental height at the final follow-up compared to that measured at the immediate postoperative period. Nonunion was evaluated according to the instability being ≥ 2 mm in the interspinous distance on the flexion-extension lateral radiographs.ResultsThe anterior and posterior segmental heights decreased from the immediate postoperative period to the final follow-up at 1.33 ± 1.46 mm and 0.81 ± 1.27 mm, respectively. Subsidence ≥ 2 mm and 3 mm were observed in 12 segments (25.5%) and 7 segments (14.9%), respectively. Among the expected risk factors for subsidence, a smaller anteroposterior (AP) diameter (14 mm vs. 12 mm) of cages (p = 0.034; odds ratio [OR], 0.017) and larger intraoperative distraction (p = 0.041; OR, 3.988) had a significantly higher risk of subsidence. Intervertebral nonunion was observed in 7 segments (7/47, 14.9%). Compared with the union group, the nonunion group had a significantly higher ratio of two-level fusion to one-level fusions (p = 0.001).ConclusionsAnterior cervical fusion using a stand-alone cage with a large AP diameter while preventing anterior intraoperative over-distraction will be helpful to prevent the subsidence of cages. Two-level cervical fusion might require more careful attention for avoiding nonunion.

Safe Clinical Use of Carbon Nanotubes as Innovative Biomaterials

“…519,520 Because of its low compatibility for bone tissue, however, PEEK has been associated with the problem of insufficient bone union when used in implants that are directly exposed to bone, such as interbody fusion cages. 521−524 MWCNTs have been reported by many research teams, including ours, to possess bone induction potential. 58,62,63,67,213,215,216,218,525,526 If conjugation with MWCNTs further improves the mechanical characteristics of PEEK and also induces osteogenesis, then MWCNT/PEEK composite will become an ideal interbody fusion material (Figure 13).…”

Bioabsorbable self-retaining PLA/nano-sized β-TCP cervical spine interbody fusion cage in goat models: an in vivo study

“…The design and development of a suitable fusion cage to replace a degenerated disc are currently being performed. 5,7 A possible solution for many of these problems may be a bioabsorbable cage. PLA is currently the most popular material that is used to make bioabsorbable cages, and these cages can be designed with similar stiffness to a human bone to reduce stress shielding.…”

Anterior Cervical Discectomy and Fusion (ACDF) using StandAlone Polyetheretherketone (PEEK) Cage Packed with Local Autologous Bone Graft

“…Subsidence and nonunion have several risk factors 2,4,7,24,25 . As for examples, wrong surgical techniques such as over distraction, endplate damage, and inadequate preparation of endplate.…”

“…In the study of Park et al 12 , there were 22.6% subsidence and 9.7% nonunion. Yang et al 25 reported in their study of ACDF with stand-alone case filled with iliac crest bone graft that25.5% subsidence and 14.9% nonunion. In a similar study by Bartels et al 2 in ACDF using a stand-alone cage packed with local autologous bone graft from the adjacent vertebrae found, 29.2% subsidence and 4.3% nonunion.…”