Randomized Controlled Trial of Posterior Lumbar Interbody Fusion With Ti- and CaP-Nanocoated Polyetheretherketone Cages: Comparative Study of the 1-Year Radiological and Clinical Outcome

Clinical and Radiographic Outcomes of Anterior Lumbar Interbody Fusions Using a Titanium Cage with a Biomimetic Surface

BACKGROUND

 We analyzed clinical and radiographic outcomes in patients undergoing anterior lumbar interbody fusions (ALIFs) using a new biomimetic titanium fusion cage (Titan nanoLOCK interbody, Medtronic, Minneapolis, Minnesota, United States). This specialized cage employs precise nanotechnology to stimulate inherent biochemical and cellular osteogenic reactions to the implant, aiming to amplify the rate of fusion. To our knowledge, this is the only study to assess early clinical and radiographic results in ALIFs.

METHODS

 We conducted a retrospective review of data for patients who underwent single or multilevel ALIF using this implant between October 2016 and April 2021. Indications for treatment were spondylolisthesis, postlaminectomy syndrome, or spinal deformity. Clinical and radiographic outcome data for these patients were collected and assessed.

RESULTS

 A total of 84 patients were included. The mean clinical follow-up was 36.6 ± 14 months. At 6 months, solid fusion was seen in 97.6% of patients. At 12 months, solid fusion was seen in 98.8% of patients. Significant improvements were seen in patient-reported outcome measures (PROMs; visual analog scale and Oswestry Disability Index) at 6 and 12 months compared with the preoperative scores (p < 0.001). One patient required reoperation for broken pedicle screws 2 days after the ALIF. None of the patients required readmission within 90 days of surgery. No patients experienced an infection.

CONCLUSIONS

 ALIF using a new titanium interbody fusion implant with a biomimetic surface technology demonstrated high fusion rates (97.6%) as early as 6 months. There was significant improvement in PROMs at 6 and 12 months.

The Influence of Titanium-coated Poryetheretherketone Cages in Fusion Status after Posterior Lumbar Interbody Fusion with Cortical Bone Trajectory Screw Fixation

OBJECTIVE

Posterior lumbar interbody fusion (PLIF) with cortical bone trajectory (CBT) screw fixation (CBT-PLIF) shows potential for reducing adjacent segmental disease. Previously, our investigations revealed a relatively lower fusion rate with the use of carbon fiber-reinforced polyetheretherketone (CP) cages in CBT-PLIF compared with traditional pedicle screw fixation (PS-PLIF) using CP cages. This study aims to evaluate whether the implementation of titanium-coated polyetheretherketone (TP) cages can enhance fusion outcomes in CBT-PLIF.

METHODS

A retrospective analysis was conducted on 68 consecutive patients who underwent CBT-PLIF with TP cages (TP group) and 89 patients who underwent CBT-PLIF with CP cages (CP group). Fusion status was assessed using computed tomography at 1 year postoperatively and dynamic plain radiographs at 2 years postoperatively.

RESULTS

No statistically significant differences in fusion rates were observed at 1 and 2 years postoperatively between the TP group (86.8% and 89.7%, respectively) and the CP group (77.5% and 88.8%, respectively). Notably, the CP group exhibited a significant improvement in fusion rate from 1 to 2 years postoperatively (P = 0.002), while no significant improvement was observed in the TP group.

CONCLUSIONS

Examination of temporal changes in fusion rates reveals that only the TP group achieved a peak fusion rate 1 year postoperatively. This implies that TP cages may enhance the fusion process even after CBT-PLIF. Nevertheless, the definitive efficacy of TP cages for CBT-PLIF remains uncertain in the context of overall fusion rates.

Titanium-coated PEEK Versus Uncoated PEEK Cages in Lumbar Interbody Fusion: A Systematic Review and Meta-analysis of Randomized Controlled Trial

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

This study was performed to compare the fusion and subsidence rate of titanium-coated polyetheretherketone (Ti-PEEK) versus polyetheretherketone (PEEK) cages after lumbar fusion and to investigate the clinical effect on patient-reported outcomes (PROMs).

SUMMARY OF BACKGROUND DATA

Ti-PEEK cages have been developed to combine the advantages of both titanium alloy and PEEK, but whether they are superior to uncoated PEEK cages in bone fusion is still inconclusive.

METHODS

PubMed, EMBASE, ISI Web of Science, CENTRAL, and CNKI were searched to identify randomized controlled trials that compared the efficacy of Ti-PEEK and PEEK cages in lumbar fusion. Difference in fusion rate and subsidence rate was indicated by risk ratio and its associated 95% confidence interval (95% confidence interval). Mean difference was calculated for Oswestry Disability Index and visual analogue scale for low back pain. Subgroup analysis was performed by time course after the surgery. The Grading of Recommendations, Assessment, Development and Evaluation approach was used to evaluate the certainty of evidence.

RESULTS

Four randomized controlled trials involving 325 patients (160 patients in Ti-PEEK group and 165 patients in PEEK group) that underwent lumbar fusion were included by our current study. Low to moderate evidence suggested that Ti-PEEK and PEEK cages exhibited equivalent fusion rate and subsidence rate at any follow-up time. Low to moderate evidence suggested that there was no difference in PROMs except for visual analogue scale measured at 6 months (mean difference: -0.57, 95% confidence interval -0.94, -0.21; P =0.002) but the difference was not clinically relevant according to the minimal clinically important difference.

CONCLUSION

Low to moderate evidence showed that Ti-PEEK and PEEK had equivalent effect in bone fusion and cages subsidence at any follow-up time after lumbar fusion surgeries. Low to moderate evidence showed no clinically important difference in PROMs.

Titanium‑coated polyetheretherketone cages vs. polyetheretherketone cages in lumbar interbody fusion: A systematic review and meta‑analysis

Fusion material is one of the key factors in the success of lumbar interbody fusion surgery. The present meta-analysis compared the safety and efficacy of titanium-coated (Ti) polyetheretherketone (PEEK) and PEEK cages. Published literature on the use of Ti-PEEK and PEEK cages in lumbar interbody fusion was systematically searched on Embase, PubMed, Central, Cochrane Library, China National Knowledge Infrastructure and Wanfang databases. A total of 84 studies were retrieved and seven were included in the present meta-analysis. Literature quality was assessed using the Cochrane systematic review methodology. After data extraction, meta-analysis was performed using the ReviewManager 5.4 software. Meta-analysis showed that, compared with that in the PEEK cage group, the Ti-PEEK cage group showed a higher interbody fusion rate at 6 months postoperatively (95% CI, 1.09-5.60; P=0.03) and improved Oswestry Disability Index (ODI) scores at 3 months postoperatively [95% CI, -7.80-(-0.62); P=0.02] and visual analog scale (VAS) scores of back pain at 6 months postoperatively [95% CI, -0.8-(-0.23); P=0.0008]. However, there were no significant differences in intervertebral bone fusion rate (12 months after surgery), cage subsidence rate, ODI score (6 and 12 months after surgery) or VAS score (3 and 12 months after surgery) between the two groups. The results of the meta-analysis showed that the Ti-PEEK group had an improved interbody fusion rate and higher postoperative ODI score in the early postoperative period (≤6 months).

An alternative method to evaluate lumbar interbody fusion status focusing on position change of screw-rod constructs

OBJECTIVES

The evaluation of lumbar interbody fusion status is generally subjective and may differ among raters. The authors examined whether the assessment of position change of screw-rod constructs could be an alternative method for the evaluation of fusion status.

METHODS

Sixty-three patients undergoing lumbar interbody single-level fusion were retrospectively reviewed. Three-dimensional images of screw-rod constructs were created from baseline CT examination on the day after surgery and follow-up CT examinations (3-5 months, 6-11 months, and ≥ 12 months) and superposed, with position change of screw-rod constructs being evaluated by the distance between the 3-dimensional images at baseline and follow-up. The evaluation was repeated twice to confirm the reproducibility. Fusion status on follow-up CT examinations was assessed by three raters, where inter-rater reliability was evaluated with Fleiss' kappa. The results of the fusion status were classified into fusion and incomplete fusion groups in each timing of follow-up CT examinations, where the amount of position change was compared between the two groups.

RESULTS

The evaluation of position change was completely reproducible. The Fleiss' kappa (agreements) was 0.481 (69.4%). The medians of the amount of position change in fusion and incomplete fusion groups were 0.134 mm and 0.158 mm at 3-5 months (p = 0.21), 0.160 mm and 0.190 mm at 6-11 months (p = 0.02), and 0.156 mm and 0.314 mm at ≥ 12 months (p = 0.004).

CONCLUSIONS

The assessment of position change of screw-rod constructs at 6 months or more after surgery can be an alternative method for evaluating lumbar interbody fusion status.

KEY POINTS

• Lumbar interbody fusion status (satisfactory, incomplete, or failed) is associated with the quantification of position change of screw-rod in this study. • Reference values for the evaluation of position change in identifying interbody fusion status are provided. • Position change of screw-rod could be a supportive method for evaluating interbody fusion status.

Early Outcomes of 3D-printed Porous Titanium versus Polyetheretherketone (PEEK) Cage Implantation for Standalone Lateral Lumbar Interbody Fusion in the Treatment of Symptomatic Adjacent Segment Degeneration

OBJECTIVE

This study compared outcomes of 3D-printed porous titanium (Ti) versus polyetheretherketone (PEEK) cage implantation for standalone lateral lumbar interbody fusion (SA-LLIF) in the treatment of symptomatic adjacent segment degeneration (ASD).

METHODS

44 patients (59 levels) underwent SA-LLIF with Ti or PEEK cages between 10/2016 and 07/2020. The primary outcome was cage subsidence according to Marchi et al. Secondary outcomes included revision/recommendations for revision surgery, back/leg pain severity, changes in disc/foraminal height and global/segmental lumbar lordosis.

RESULTS

44 patients (21 female) were included with a mean age at surgery of 61.8±11.5 years, average radiological follow-up of 12.5±8.2 and clinical follow-up of 11.0±7.1 months. The overall subsidence rate was significantly less in the Ti versus PEEK group (20% vs. 58.8%; p=0.004). Revision was recommended to none of the patients in the Ti and 3 in the PEEK group (p=0.239). Furthermore, patients in the Ti group showed significantly better improvement in back pain NRS score (p=0.001). Disc height (p<0.001) and foraminal height restoration (p=0.011) were statistically significant in the Ti group, whereas only disc height restoration was significant in the PEEK group (p=0.003).

CONCLUSION

In patients undergoing SA-LLIF for ASD treatment, 3D-printed Ti cages had significantly lower overall subsidence rate compared to PEEK cages. Furthermore, Ti cages resulted in fewer recommendations for revision surgery. Whether greater pain reduction in the Ti group is associated with earlier or higher fusion rates needs to be further elucidated.

Integral fixation titanium/polyetheretherketone cages for cervical arthrodesis: Two-year clinical outcomes and fusion rates using β-tricalcium phosphate or supercritical carbon dioxide treated allograft

Context:

Despite increasing promising reports regarding composite titanium (Ti)/PolyEtherEtherKetone (PEEK) cages, further longer-term, quality research is required. Synthetic bone graft substitutes are another rapidly developing area of spinal surgical research.

Aims:

The purpose of this study is to evaluate the outcomes of an integral fixation composite Ti/PEEK cage for anterior cervical discectomy and fusion (ACDF) and compare a synthetic bone graft substitute (β-tricalcium phosphate; [βTCP]) with allograft processed using supercritical fluid technology.

Methods and Design:

Data from 195 consecutive patients were prospectively collected from a single centre. Indications were largely degenerative. Allograft and βTCP were used in a 3:1 randomization protocol. Patients were followed up for a minimum of 6 months and up to 48 months. Clinical outcomes included visual analogue scale and neck oswestry disability index. Radiographic outcomes included fusion rates, subsidence rates and implant complications.

Results:

Graft sub-cohorts were largely comparable and included 133 and 52 patients in the allograft and βTCP sub-cohorts, respectively. Clinical outcomes overall significantly improved (P < 0.001), with no significant inter-cohort differences. There were no implant-related complications. Overall fusion rate was 94.1% (175/186). The allograft cohort produced a significantly greater fusion rate of 97.7% (126/129) compared to 77.6% (38/49) for the βTCP cohort (P = 0.001).

Conclusions:

This study demonstrates the viability of an integral fixation composite Ti/PEEK ACDF device in effectively and safely improving patient outcomes and achieving fusion. Allograft is more effective in achieving fusion compared to βTCP, though both were similarly efficacious in improving clinical outcomes.

Sustainable Surface Modification of Polyetheretherketone (PEEK) Implants by Hydroxyapatite/Silica Coating-An In Vivo Animal Study

Polyetheretherketone (PEEK) has the potential to overcome some of the disadvantages of titanium interbody implants in anterior cervical and discectomy and fusion (ACDF). However, PEEK shows an inferior biological behavior regarding osseointegration and bioactivity. Therefore, the aim of the study was to create a bioactive surface coating on PEEK implants with a unique nanopore structure enabling the generation of a long-lasting interfacial composite layer between coating material and implant. Seventy-two PEEK implants-each thirty-six pure PEEK implants (PI) and thirty-six PEEK implants with a sprayed coating consisting of nanocrystalline hydroxyapatite (ncHA) embedded in a silica matrix and interfacial composite layer (SPI)-were inserted in the femoral condyles of adult rats using a split-side model. After 2, 4 and 8 weeks, the femur bones were harvested. Half of the femur bones were used in histological and histomorphometrical analyses. Additionally, pull-out tests were performed in the second half. Postoperative healing was uneventful for all animals, and no postoperative complications were observed. Considerable crestal and medullary bone remodeling could be found around all implants, with faster bone formation around the SPI and fewer regions with fibrous tissue barriers between implant and bone. Histomorphometrical analyses showed a higher bone to implant contact (BIC) in SPI after 4 and 8 weeks (p < 0.05). Pull-out tests revealed higher pull-out forces in SPI at all time points (p < 0.01). The presented findings demonstrate that a combination of a bioactive coating and the permanent chemical and structural modified interfacial composite layer can improve bone formation at the implant surface by creating a sustainable bone-implant interface. This might be a promising way to overcome the bioinert surface property of PEEK-based implants.

PEEK versus titanium cages in lateral lumbar interbody fusion: a comparative analysis of subsidence

OBJECTIVE

The authors have provided a review of radiographic subsidence after lateral lumbar interbody fusion (LLIF) as a comparative analysis between titanium and polyetheretherketone (PEEK) cages. Many authors describe a reluctance to use titanium cages in spinal fusion secondary to subsidence concerns due to the increased modulus of elasticity of metal cages. The authors intend for this report to provide observational data regarding the juxtaposition of these two materials in the LLIF domain.

METHODS

A retrospective review of a prospectively maintained database identified 113 consecutive patients undergoing lateral fusion for degenerative indications from January to December 2017. The surgeons performing the cage implantations were two orthopedic spine surgeons and two neurosurgeons. Plain standing radiographs were obtained at 1–2 weeks, 8–12 weeks, and 12 months postoperatively. Using a validated grading system, interbody subsidence into the endplates was graded at these time points on a scale of 0 to III. The primary outcome measure was subsidence between the two groups. Secondary outcomes were analyzed as well.

RESULTS

Of the 113 patients in the sample, groups receiving PEEK and titanium implants were closely matched at 57 and 56 patients, respectively. Cumulatively, 156 cages were inserted and recombinant human bone morphogenetic protein–2 (rhBMP-2) was used in 38.1%. The average patient age was 60.4 years and average follow-up was 75.1 weeks. Subsidence in the titanium group in this study was less common than in the PEEK cage group. At early follow-up, groups had similar subsidence outcomes. Statistical significance was reached at the 8- to 12-week and 52-week follow-ups, demonstrating more subsidence in the PEEK cage group than the titanium cage group. rhBMP-2 usage was also highly correlated with higher subsidence rates at all 3 follow-up time points. Age was correlated with higher subsidence rates in univariate and multivariate analysis.

CONCLUSIONS

Titanium cages were associated with lower subsidence rates than PEEK cages in this investigation. Usage of rhBMP-2 was also robustly associated with higher endplate subsidence. Each additional year of age correlated with an increased subsidence risk. Subsidence in LLIF is likely a response to a myriad of factors that include but are certainly not limited to cage material. Hence, the avoidance of titanium interbody implants secondary solely to concerns over a modulus of elasticity likely overlooks other variables of equal or greater importance.