Structural Allograft Versus PEEK Implants in Anterior Cervical Discectomy and Fusion: A Systematic Review

Structural Allograft versus Polyetheretherketone Cage in Anterior Cervical Discectomy and Fusion: A Meta-Analysis

BACKGROUND

Polyetheretherketone (PEEK) cages and structural allografts (SAs) are commonly used in anterior cervical discectomy and fusion (ACDF), yet their postoperative results remain uncertain. This meta-analysis was conducted to determine whether there were any differences in outcomes between patients who received these two grafts in ACDF.

METHODS

We comprehensively searched electronic databases up to August 2023. Observational studies or randomized controlled trials reported postoperative outcomes, including fusion, subsidence, reoperation rates, and patient-reported outcomes through the Neck Disability Index, the visual analog scale for neck and arm pain, and the Japanese Orthopaedic Association (JOA)/modified JOA score following primary ACDF using SA or PEEK cage. The results are presented in odds ratios (ORs) or mean differences with corresponding 95% confidence intervals (CIs).

RESULTS

Eleven studies were included, with 1213 patients (788 receiving SAs and 425 receiving PEEK cages). Patients having SA had significantly higher fusion (OR: 1.84; 95% CI: 1.27-2.67; P = 0.001) and lower subsidence (OR: 0.50; 95% CI: 0.30-0.86; P = 0.01) rates when compared with the PEEK cage. There was no difference in revision rate between SA or PEEK cage (P = 0.88). Two grafts demonstrated similar clinical improvements in Neck Disability Index (P = 0.31), visual analog scale for the neck (P = 0.77) and arm pain (P = 0.22), and JOA/modified JOA score (P = 0.99).

CONCLUSIONS

SA demonstrates better fusion and lower subsidence rates than the PEEK cage in ACDF. Nevertheless, SAs and PEEK cages resulted in equally successful postoperative clinical performances.

Anterior cervical decompression and fusion at one and two levels: trends and factors associated with structural allograft versus synthetic cages

Background

Following decompression in anterior cervical discectomy and fusion (ACDF), reconstruction is typically done with structural allograft or a synthetic cage. Relative trends and factors associated with utilizing these implants have not been well characterized.

Methods

The PearlDiver 2011 to 2021 M157 database was used to identify adult patients undergoing 1- or 2-level ACDF. The incidence of structural allograft versus synthetic cage utilized was compared by year. Patient factors predictive of synthetic cage use as the structural interbody for ACDF were assessed with multivariable analysis. Further, the use of anterior plates was trended to provide a measure of usage of stand-alone devices (this comparison was made beginning with 2016 based on coding limitations).

Results

Of 173,833 isolated 1- or 2-level ACDF cases identified, structural allograft was used for 63,029 (36.3%) and synthetic cages were used for 110,804 (63.8%). The use of synthetic cages increased from 51.1% of cases in 2011 to 75.8% of cases in 2021 (p < 0.0001). Independent clinical predictors of synthetic cage use were: older age (odds ratio [OR] 1.02 per decade), female sex (OR 1.04), and greater ECI (OR 1.09 per 2-point increase).Independent non-clinical predictors of synthetic cage use were: geographic region (Northeast OR 1.11, South OR 1.85, and West 2.08, each relative to Midwest), and provider specialty (orthopedic OR 1.06 relative to neurosurgeons). There was an increase in the percent of synthetic cases without separately coded plate ("stand-alone" interbody cages: 21.7% in 2016 to 35.3% in 2021, p < 0.001).

Conclusions

The usage of synthetic cages in 1- and 2- level ACDF has increased relative to structural allograft between 2011 and 2021 in the United States and more recently the use of "stand-alone" synthetic cages has been on the rise. Non-clinical as well as clinical factors were associated with implant choice, suggesting room for more consistent care algorithms.

A Comparison between Structural Allografts and Polyetheretherketone Interbody Spacers Used in Anterior Cervical Discectomy and Fusion: A Systematic Review and Meta-analysis

Among interbody implants used during anterior cervical discectomy and fusion (ACDF), structural allografts and polyetheretherketone (PEEK) are the most used spacers. Currently, no consensus has been established regarding the superiority of either implant, with US surgeons preferring structural allografts, whereas UK surgeons preferring PEEK. The purpose of this systematic review (level of evidence, 4) was to compare postoperative and patient-reported outcomes between the use of structural allografts PEEK interbody spacers during ACDF. Five electronic databases (PubMed, Embase, Scopus, Web of Science, and Cochrane) were searched for articles comparing the usage of structural allograft and PEEK interbody spacers during ACDF procedures from inception to April 10, 2023. The searches were conducted using the keywords "Spine," "Allograft," and "PEEK" and were performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. Subsequent quality and sensitivity analyses were performed on the included studies. Nine studies involving 1,074 patients were included. Compared with the PEEK group, the structural allograft group had comparable rates of postoperative pseudoarthrosis (p=0.58). However, when stratified according to the number of levels treated, the 3-level ACDF PEEK group was 3.45 times more likely to have postoperative pseudoarthrosis than the structural allograft group (p=0.01). Subsequent postoperative outcomes (rate of subsidence and change in the preoperative and postoperative segmental disc heights) were comparable between the PEEK and structural allograft groups. Patient-reported outcomes (Visual Analog Scale [VAS] of neck pain and Neck Disability Index [NDI]) were comparable. This study showed that for 3-level ACDFs, the use of structural allografts may confer higher fusion rates. However, VAS neck pain, NDI, and subsidence rates were comparable between structural allografts and PEEK cages. In addition, no significant difference in pseudoarthrosis rates was found between PEEK cages and structural allografts in patients undergoing 1- and 2-level ACDFs.

Dosing Strategy for Osteobiologics Used in ACDF Surgery: Influence on Fusion Rates and Associated Complications. A Systematic Literature Review

STUDY DESIGN

Systematic review.

OBJECTIVE

To assess the available evidence related to dose-dependent effectiveness (i.e., bone fusion) and morbidity of osteobiologics used in anterior cervical discectomy and fusion (ACDF).

METHODS

Studies with more than 9 adult patients with degenerated/herniated cervical discs operated for one-to four-levels ACDF reporting used osteobiologics doses, fusion rates at six months or later, and related comorbidities were included. PubMed, EMBASE, ClinicalTrials, and Cochrane were searched through September 2021. Data extracted in spread sheet and risk of bias assessed using MINORS and Rob-2.

RESULTS

Sixteen studies were selected and sub-grouped into BMP and non-BMP osteobiologics. For the 10 BMP studies, doses varied from 0.26 to 2.1 mg in 649 patients with fusion rates of 95.3 to 100% at 12 months. For other osteobiologics, each of six studies reported one type of osteobiologic in certain dose/concentration/volume in a total of 580 patients with fusion rates of 6.8 to 96.9% at 12 months. Risk of bias was low in three of the 13 non-randomized (18.75%) and in all the three randomized studies (100%).

CONCLUSIONS

Taking into account the inconsistent reporting within available literature, for BMP usage in ACDF, doses lower than 0.7 mg per level can achieve equal successful fusion rates as higher doses, and there is no complication-free dose proved yet. It seems that the lower the dose the lower the incidence of serious complications. As for non-BMP osteobiologics the studies are very limited for each osteobiologic and thus conclusions must be drawn individually and with caution.

The Use of Osteobiologics in Single versus Multi-Level Anterior Cervical Discectomy and Fusion: A Systematic Review

STUDY DESIGN

Systematic literature review.

OBJECTIVES

In this study we assessed evidence for the use of osteobiologics in single vs multi-level anterior cervical discectomy and fusion (ACDF) in patients with cervical spine degeneration. The primary objective was to compare fusion rates after single and multi-level surgery with different osteobiologics. Secondary objectives were to compare differences in patient reported outcome measures (PROMs) and complications.

METHODS

After a global team of reviewers was selected, a systematic review using different repositories was performed, confirming to PRISMA and GRADE guidelines. In total 1206 articles were identified and after applying inclusion and exclusion criteria, 11 articles were eligible for analysis. Extracted data included fusion rates, definition of fusion, patient reported outcome measures, types of osteobiologics used, complications, adverse events and revisions.

RESULTS

Fusion rates ranged from 87.7% to 100% for bone morphogenetic protein 2 (BMP-2) and 88.6% to 94.7% for demineralized bone matrix, while fusion rates reported for other osteobiologics were lower. All included studies showed PROMs improved significantly for each osteobiologic. However, no differences were reported when comparing osteobiologics, or when comparing single vs multi-level surgery specifically.

CONCLUSION

The highest fusion rates after 2-level ACDF for cervical spine degeneration were reported when BMP-2 was used. However, PROMs did not differ between the different osteobiologics. Further blinded randomized trials should be performed to compare the use of BMP-2 in single vs multi-level ACDF specifically.

Effects of Structural Allograft versus Polyetheretherketone Cage in Patients Undergoing Spinal Fusion Surgery: A Systematic Review and Meta-Analysis

BACKGROUND

Inter body spacers have been widely used in patients undergoing spinal fusion surgery; however, it is not clear whether one implant shows superior clinical outcomes compared with the other. This systematic review and meta-analysis comprehensively evaluated the radiologic outcomes and patient-reported outcomes of structural allograft versus polyetheretherketone (PEEK) implants in patients undergoing spinal fusion surgery.

METHODS

Extensive literature searches were conducted on online databases, including MEDLINE, Embase, Web of Science, Cochrane Central Register of Controlled Trials, and Cochrane Library, until January 2023. The present study adheres to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, and the Newcastle-Ottawa Scale and Cochrane Collaboration Risk of Bias tool were used to assess the quality of the included studies.

RESULTS

Fifteen studies, encompassing 8020 patients, met the eligibility criteria. The results indicate that structural allografts show a higher fusion rate compared with PEEK implants (odds ratio [OR], 1.88; 95% confidence interval [CI], 1.05-3.37; P ＝0.03; I2 = 71%). In addition, the structural allograft group also had a lower pseudarthrosis rate (OR, 0.40; 95% CI, 0.20-0.80; P = 0.009; I2 = 75%) and reoperation rate (OR, 0.46; 95% CI, 0.26-0.81; P = 0.007; I2 = 38%).

CONCLUSIONS

Our systematic review and meta-analysis show that structural allograft has a higher fusion rate compared with PEEK implants in patients undergoing spinal fusion surgery. In addition, structural allograft has a lower pseudarthrosis rate and reoperation rate.

A Five-Year Cost-Utility Analysis Comparing Synthetic Cage Versus Allograft Use in Anterior Cervical Discectomy and Fusion Surgery for Cervical Spondylotic Myelopathy

STUDY DESIGN

Retrospective cost-utility analysis.

OBJECTIVE

To conduct a cost-analysis comparing synthetic cage (SC) versus allograft (Allo) over a five-year time horizon.

SUMMARY OF BACKGROUND DATA

SC and Allo are two commonly used interbody choices for anterior cervical discectomy and fusion (ACDF) surgery. Previous analyses comparative analyses have reached mixed conclusions regarding their cost-effectiveness, yet recent estimates provide high-quality evidence.

MATERIALS AND METHODS

A decision-analysis model comparing the use of Allo versus SC was developed for a hypothetical 60-year-old patient with cervical spondylotic myelopathy undergoing single-level ACDF surgery. A comprehensive literature review was performed to estimate probabilities, costs (2020 USD) and quality-adjusted life years (QALYs) gained over a five-year period. A probabilistic sensitivity analysis using a Monte Carlo simulation of 1000 patients was carried out to calculate incremental cost-effectiveness ratio and net monetary benefits. One-way deterministic sensitivity analysis was performed to estimate the contribution of individual parameters to uncertainty in the model.

RESULTS

The use of Allo was favored in 81.6% of the iterations at a societal willing-to-pay threshold of 50,000 USD/QALY. Allo dominated (higher net QALYs and lower net costs) in 67.8% of the iterations. The incremental net monetary benefits in the Allo group was 2650 USD at a willing-to-pay threshold of 50,000 USD/QALY. One-way deterministic sensitivity analysis revealed that the cost of the index surgery was the only factor which significantly contributed to uncertainty.

CONCLUSION

Cost-utility analysis suggests that Allo maybe a more cost-effective option compared with SCs in adult patients undergoing ACDF for cervical spondylotic myelopathy.

The Variability and Contributions to Cost of Anterior Cervical Discectomy and Fusion Constructs

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

To characterize the variability in cost for anterior cervical discectomy and fusion (ACDF) constructs and to identify key predictors of procedural cost.

SUMMARY OF BACKGROUND DATA

ACDF is commonly performed for surgical treatment of cervical radiculopathy and myelopathy. Numerous biomechanical constructs and graft/biological options are available, with most demonstrating relatively equivalent clinical results. Despite the substantial focus on value in spine care, the differences and contributions to procedural cost in ACDF have not been well defined.

MATERIALS AND METHODS

We evaluated the records of patients who underwent a single level ACDF from 2016 to 2020 at 4 hospitals in a major metropolitan area. We abstracted demographics, insurance status, operative time, diagnosis, surgeon, institution, and components of procedural costs. Costs based on construct were compared using multivariable adjusted analyses using negative binomial regression. The primary outcome measures were cost differences between ACDF techniques.

RESULTS

Two hundred sixty-four patients were included, with procedures by 13 surgeons across 4 institutions. The total procedural cost for ACDF had a mean of US$2317 with wide variation (range, US$967-US$7370). Multivariable analysis revealed body mass index and use of polyether ether ketone to be correlated with increased cost while carbon fiber and autograft correlated with decreased cost. When comparing standalone device constructs to cases with anterior instrumentation (plate/screws), the total cost was significantly higher in the plate/screw group (US$2686±US$921 vs. US$1466±US$878, P<0.001).

CONCLUSIONS

We encountered wide variation in procedural costs associated with ACDF, including as much as an 8-fold difference in the cost of constructs. The most important drivers included instrumentation type and implant materials. Here, we identify potential targets of opportunity for health care organizations that are looking to reduce variance in procedural expenditures to improve health care savings associated with the performance of ACDF.

Prospective, Randomized, Blinded Clinical Trial Comparing PEEK and Allograft Spacers in Patients Undergoing Anterior Cervical Discectomy and Fusion Surgeries

STUDY DESIGN

Prospective, randomized, blinded clinical trial.

OBJECTIVE

To examine clinical and radiological outcomes in patients undergoing anterior cervical discectomy and fusion (ACDF) surgeries randomized to receive either polyether-ether-ketone (PEEK) or structural bone allografts.

SUMMARY OF BACKGROUND DATA

The biomechanical qualities as well as osteoconductive, osteogenic, and osteoinductive properties of various graft materials have been previously evaluated. There remain questions, however, as to whether there are any clinical and/or radiographic outcome differences in the selection of interbody graft types for ACDF.

METHODS

Patients undergoing one- to three-level ACDF with single anterior plate fixation were randomized (1:1 ratio) to receive either cortical allograft or PEEK interbody spacers. Radiographic and clinical outcomes were assessed at 3, 6, 12, and 24 months with an additional postoperative radiographic assessment.

RESULTS

A total of 120 patients were enrolled and randomized. Comparing clinical outcomes, no differences in arm or neck pain scores were noted; however, there was a statistically significant (≤0.041) improvement in SF-36 PCS scores for the allograft group at all follow-up time points and a tendency toward lower disability scores. Overall, evidence of radiographic fusion was achieved in 87 (91.6%) patients: five (10.2%) and three (6.5%) patients had pseudoarthrosis (P = 0.72) in the PEEK and allograft groups, respectively. At 24 months' follow-up time, any cervical or segmental alignment restoration achieved with surgery was lost and no statistically significant changes were detected when all levels of surgery were included. Likewise, there were no statistically significant differences between the groups for anterior or posterior body height measurements at the 24 months' follow-up. Approximately 20% of patients had anterior and posterior subsidence, all grade 0 regardless of the group assignment.

CONCLUSION

Comparable radiographic outcomes were observed for patients undergoing one- to three-level PEEK versus allograft-assisted ACDF surgeries. Although MCID comparisons suggest that allograft and PEEK-treated patients have similar clinical outcomes, testing that incorporates the magnitude of the change suggests that there may be a statistically significant greater magnitude of improvement for the allograft group patients, but further studies with a larger sample size would be helpful to determine if a true effect exists.

Biomaterials for Interbody Fusion in Bone Tissue Engineering

In recent years, interbody fusion cages have played an important role in interbody fusion surgery for treating diseases like disc protrusion and spondylolisthesis. However, traditional cages cannot achieve satisfactory results due to their unreasonable design, poor material biocompatibility, and induced osteogenesis ability, limiting their application. There are currently 3 ways to improve the fusion effect, as follows. First, the interbody fusion cage is designed to facilitate bone ingrowth through the preliminary design. Second, choose interbody fusion cages made of different materials to meet the variable needs of interbody fusion. Finally, complete post-processing steps, such as coating the designed cage, to achieve a suitable osseointegration microstructure, and add other bioactive materials to achieve the most suitable biological microenvironment of bone tissue and improve the fusion effect. The focus of this review is on the design methods of interbody fusion cages, a comparison of the advantages and disadvantages of various materials, the influence of post-processing techniques and additional materials on interbody fusion, and the prospects for the future development of interbody fusion cages.

Clinical outcomes after 4- and 5-level Anterior Cervical Discectomy and Fusion for treatment of symptomatic multilevel cervical spondylosis

OBJECTIVE

There are limited patient-reported outcome measure (PROM) data on 4- and 5-level ACDF. The largest series to date solely focused on complications. This retrospective series evaluates PROMs after 4- and 5-level ACDF.

METHODS

Pertinent data from adult patients treated with a 4- or 5-level ACDF in 2011-2019 were analyzed. PROMs and minimal clinically important differences (MCID) were assessed. Factors associated with favorable and unfavorable outcomes were identified.

RESULTS

There were thirty-four patients (thirty underwent 4-level and four underwent 5-level ACDFs) with mean age of 59.6; 55.9% were women. At 3 months, there were significant improvements in PROMs except SF-12 MCS with modest improvement. At 12 months, there were significant improvements in PROMs except SF-12 PCS with moderate improvement. The proportions of patients that met the MCID cut-offs ranged from 35.3% (NRS-neck) to 75% (VR-12 PCS) at 3 months and 38.2% (NRS-arm) to 65.5% (VR-12 MCS) at 12 months. Shorter symptom duration was associated with significantly reduced postoperative pain and NDI scores. Shorter length of stay was associated with significantly improved postoperative functional outcomes. 4-level compared 5-level ACDF patients achieved better postoperative PROMs. Shorter procedure duration was associated with improved PROMs at 3 months. No patients returned to the operating room within 30 days. Patients that required reoperation achieved significantly inferior NDI, NRS-neck, and SF-12 PCS at 3 months.

CONCLUSIONS

This study demonstrated satisfactory PROMs up to 12 months after 4- and 5-level ACDF despite the complication rate. With thorough preoperative planning and meticulous technique, performing this procedure in carefully selected patients may be associated with acceptable PROM.

Nonunion Rates After Anterior Cervical Discectomy and Fusion: Comparison of Polyetheretherketone vs Structural Allograft Implants

BACKGROUND

Although advances in implant materials, such as polyetheretherketone (PEEK), have been developed aimed to improve outcome after anterior cervical discectomy and fusion (ACDF), it is essential to confirm whether these changes translate into clinically important sustained benefits.

OBJECTIVE

To compare the radiographic and clinical outcomes of patients undergoing up to 3-level ACDF with PEEK vs structural allograft implants.

METHODS

In this cohort study, radiographic and symptomatic nonunion rates were compared in consecutive patients who underwent 1 to 3 level ACDF with allograft or PEEK implant. Prospectively collected clinical data and patient-reported outcome (PRO) scores were compared between the allograft and PEEK groups. Regression analysis was performed to determine the predictors of nonunion.

RESULTS

In total, 194 of 404 patients met the inclusion criteria (79% allograft vs 21% PEEK). Preoperative demographic variables were comparable between the 2 groups except for age. The rate of radiographic nonunion was higher with PEEK implants (39% vs 27%, P = .0035). However, a higher proportion of nonunion in the allograft cohort required posterior instrumentation (14% vs 3%, P = .039). Patients with multilevel procedures and PEEK implants had up to 5.8 times the risk of radiographic nonunion, whereas younger patients, active smokers, and multilevel procedures were at higher risk of symptomatic nonunion.

CONCLUSION

Along with implant material, factors such as younger age, active smoking status, and the number of operated levels were independent predictors of fusion failure. Given the impact of nonunion on PRO, perioperative optimization of modifiable factors and surgical planning are essential to ensure a successful outcome.

Synthetic Cages Associated With Increased Rates of Revision Surgery and Higher Costs Compared to Allograft in ACDF in the Nonelderly Patient

Objective

The aim of this study was to compare all-cause reoperation rates and costs in nonelderly patients treated with anterior cervical discectomy and fusion (ACDF) with structural allograft versus synthetic cages for degenerative pathology.

Methods

We queried a private claims database to identify adult patients (≤ 65 years) who underwent single-level ACDF in a hospital setting using either structural allograft or a synthetic cage (polyetheretherketone, metal, or hybrid device), from 2010 to 2016. The rate of all-cause reoperations at 2 years were compared between the 2 groups. Index hospitalization costs and 90-day complication rates were also compared. Significance was set at p < 0.05.

Results

A total of 26,754 patients were included in the study. 11,514 patients (43%) underwent ACDF with structural allograft and 15,240 (57%) underwent ACDF with a synthetic cage. The patients in the allograft group were younger and more likely to be male. There was no significant difference between the 2 groups with respect to 90-day complications including: wound dehiscence, dysphagia, dysphonia, and hematoma/seroma. In the 2-year postoperative period, the synthetic cage group had a significantly higher rate of allcause reoperation compared to the allograft group (9.1% vs. 8.0%, p = 0.002). Index hospitalization costs were significantly higher in the synthetic cage group compared to those in the allograft group ($23,475 vs. $20,836, p < 0.001).

Conclusion

Structural allograft is associated with lower all-cause reoperation rates and lower index costs in nonelderly patients undergoing ACDF surgery for degenerative pathology. It is important to understand this data as we transition toward value-based care.