Comparison between Three-Dimensional Printed Titanium and PEEK Cages for Cervical and Lumbar Interbody Fusion: A Prospective Controlled Trial

OBJECTIVES

The three-dimensional printing titanium (3DPT) cage with excellent biomechanical properties and osseointegration capabilities has been initially used in spinal fusion, while the polyetheretherketone (PEEK) cage, a bioinert material device, has been a widely used for decades with relatively excellent clinical outcomes. This study was performed to investigate the early radiographic and clinical outcomes of 3DPT cage versus PEEK cage in patients undergoing anterior cervical discectomy and fusion (ACDF) and transforaminal lumbar interbody fusion (TLIF).

METHODS

This prospective controlled trial, from December 2019 to June 2022, included patients undergoing ACDF and TLIF with 3DPT cages and compared them to patients using PEEK cages for treating spinal degenerative disorders. The outcome measures included radiographic parameters (intervertebral height [IH], subsidence, fusion status, and bone-cage interface contact) and clinical outcomes (Japanese Orthopaedic Association [JOA], Neck Disability Index [NDI], Oswestry Disability Index [ODI], Short Form 12-Item Survey [SF-12], Visual Analog Scale [VAS], and Odom's criteria). Student's independent samples t test and Pearson's chi-square test were used to compare the outcome measures between the two groups before surgery and at 1 week, 3 and 6 months after surgery.

RESULTS

For the patients undergoing ACDF, the 3DPT (18 patients/[26 segments]) and PEEK groups (18 patients/[26 segments]) had similar fusion rates at 3 months and 6 months follow-up (3 months: 96.2% vs. 83.3%, p = 0.182; 6 months: 100% vs. 91.7%, p = 0.225). The subsidence in the 3DPT group was significantly lower than that in the PEEK group (3 months: 0.4 ± 0.2 mm vs. 0.9 ± 0.7 mm p = 0.004; 6 months: 0.7 ± 0.3 mm vs. 1.5 ± 0.8 mm, p < 0.001). 3DPT and PEEK cage all achieved sufficient contact with the cervical endplates. For the patients undergoing TLIF, the 3DPT (20 patients/[26 segments]) and PEEK groups (20 patients/[24 segments]) had no statistical difference in fusion rate (3 months: 84.6% vs. 58.3%, p = 0.059; 6 months: 92.3% vs. 75%, p = 0.132). The subsidence was lower than that in the PEEK group without significantly difference (3 months: 0.9 ± 0.7 mm vs.1.2 ± 0.9 mm p = 0.136; 6 months: 1.6 ± 1.0 mm vs. 2.0 ± 1.0 mm, p = 0.200). At the 3-month follow-up, the bone-cage interface contact of the 3DPT cage was significantly better than that of the PEEK cage (poor contact: 15.4% vs. 75%, p < 0.001). The values of UAR were higher in the 3DPT group than in the PEEK group during the follow-up in cervical and lumbar fusion, there were more statistical differences in lumbar fusion. There were no significant differences in the clinical assessment between 3DPT or PEEK cage in spinal fusion.

CONCLUSION

The 3DPT cage and PEEK cage can achieve excellent clinical outcomes in cervical and lumbar fusion. The 3DPT cage has advantage in fusion quality, subsidence severity, and bone-cage interface contact than PEEK cage.

Biomechanical analysis of a single-level Customized cage screw fixation for Anterior Cervical Discectomy and Fusion in the cervical spine: an in-silico study

The usual surgical choice of customized cage fixation is anterior cervical discectomy and fusion (ACDF) for cervical spondylosis with disc herniation. The safe and successful cage fixation for ACDF surgery benefits patients with cervical disc degenerative disease by easing their discomfort and regaining function. The cage prevents mobility between the vertebrae by using cage fixation to anchor the neighbouring vertebrae. The goal of the current study is to develop a customized cage-screw implant for single-level cage fixation at C4-C5 level of the cervical spine (C2-C7). The Finite Element Analysis (FEA) is performed for the intact and implanted cervical spine and analysed the flexibility, stress of the implant and implant adjacent bone during three physiological loading conditions being analysed. Lower surface of the C7 vertebrae is fixed and 50 N compressive force with 1 Nm moment are applied on the C2 vertebrae for simulated lateral bending, axial rotation and flexion-extension. The flexibility is decreased at single level of fixation (C4-C5 level) by 64% to 86%, as compared to natural cervical spine. The flexibility is increased 3% to 17% at the nearest levels of fixation. The maximum Von Mises stress in PEEK cage varies from 24 to 59 MPa and for Ti-6Al-4V screw the stress varies from 84MPa to 121MPa which are far below the yield stress of PEEK (95MPa) and Ti-6Al-4V (750MPa).