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

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.

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.

Polyetheretherketone development in bone tissue engineering and orthopedic surgery

Polyetheretherketone (PEEK) has been widely used in the medical field as an implant material, especially in bone tissue engineering and orthopedic surgery, in recent years. This material exhibits superior stability at high temperatures and is biosecured without harmful reactions. However, the chemical and biological inertness of PEEK still limits its applications. Recently, many approaches have been applied to improve its performance, including the modulation of physical morphology, chemical composition and antimicrobial agents, which advanced the osteointegration as well as antibacterial properties of PEEK materials. Based on the evolution of PEEK biomedical devices, many studies on the use of PEEK implants in spine surgery, joint surgery and trauma repair have been performed in the past few years, in most of which PEEK implants show better outcomes than traditional metal implants. This paper summarizes recent studies on the modification and application of biomedical PEEK materials, which provides further research directions for PEEK implants.

Which Radiographic Parameter Can Aid in Deciding Optimal Allograft Height for Anterior Cervical Discectomy and Fusion?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To identify preoperative radiographic parameters that can guide optimal allograft height selection for anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

Allograft height selection for ACDF depends on intraoperative assessment supported by trials; however, there is currently no radiographic reference parameter that could aid in allograft height selection for improved outcomes.

METHODS

A total of 148 patients who underwent ACDF using allografts and were followed up for more than 1 year were retrospectively reviewed. Fusion rates, subsidence, segmental lordosis, and foraminal height were assessed. Segments were divided into 2 groups according to whether the inserted allograft height was within 1 mm from the following 3 reference radiographic parameters: (1) uncinate process height, (2) adjacent disc height, and (3) preoperative disc height +2 mm.

RESULTS

This study included 101 patients with 163 segments. Segments with an allograft-uncinate height difference of ≤1 mm had a significantly higher fusion rate at 1-year follow-up compared with segments with allograft-uncinate height difference of >1 mm [85/107 (79.4%) vs. 35/56 (62.5%); P =0.025]. Subsidence, segmental lordosis, and foraminal height did not significantly differ between the groups when segments were divided according to uncinate height. Multivariate logistic regression analysis demonstrated that allograft-uncinate height difference of ≤1 mm and allograft failure were factors associated with fusion.

CONCLUSIONS

The uncinate process height can guide optimal allograft height selection for ACDF. Using an allograft with an allograft-uncinate height difference of ≤1 mm resulted in a higher fusion rate. Therefore, the uncinate process height should be checked preoperatively and used in conjunction with intraoperative assessment when selecting allograft height.

Assessment of Fusion After Anterior Cervical Discectomy and Fusion Using Convolutional Neural Network Algorithm

BACKGROUND

A convolutional neural network (CNN) is a deep learning (DL) model specialized for image processing, analysis, and classification.

OBJECTIVE

In this study, we evaluated whether a CNN model using lateral cervical spine radiographs as input data can help assess fusion after anterior cervical discectomy and fusion (ACDF).

STUDY DESIGN

Diagnostic imaging study using DL.

PATIENT SAMPLE

We included 187 patients who underwent ACDF and fusion assessment with postoperative one-year computed tomography and neutral and dynamic lateral cervical spine radiographs.

OUTCOME MEASURES

The performance of the CNN-based DL algorithm was evaluated in terms of accuracy and area under the curve.

MATERIALS AND METHODS

Fusion or nonunion was confirmed by cervical spine computed tomography. Among the 187 patients, 69.5% (130 patients) were randomly selected as the training set, and the remaining 30.5% (57 patients) were assigned to the validation set to evaluate model performance. Radiographs of the cervical spine were used as input images to develop a CNN-based DL algorithm. The CNN algorithm used three radiographs (neutral, flexion, and extension) per patient and showed the diagnostic results as fusion (0) or nonunion (1) for each radiograph. By combining the results of the three radiographs, the final decision for a patient was determined to be fusion (fusion ≥2) or nonunion (fusion ≤1). By combining the results of the three radiographs, the final decision for a patient was determined as fusion (fusion ≥2) or nonunion (nonunion ≤1).

RESULTS

The CNN-based DL model demonstrated an accuracy of 89.5% and an area under the curve of 0.889 (95% confidence interval, 0.793-0.984).

CONCLUSION

The CNN algorithm for fusion assessment after ACDF trained using lateral cervical radiographs showed a relatively high diagnostic accuracy of 89.5% and is expected to be a useful aid in detecting pseudarthrosis.

An update of interbody cages for spine fusion surgeries: from shape design to materials

INTRODUCTION

Discectomy and interbody fusion are widely used in the treatment of intervertebral disc-related diseases. Among them, the interbody cage plays a significant role. However, the complications related to the interbody cage, such as nonunion or pseudoarthrosis, subsidence, loosening, and prolapse of the cage, cannot be ignored. By changing the design and material of the interbody fusion cage, a better fusion effect can be obtained, the incidence of appeal complications can be reduced, and the quality of life of patients after interbody fusion can be improved.

AREAS COVERED

This study reviewed the research progress of cage design and material and discussed the methods of cage design and material to promote intervertebral fusion.

EXPERT OPINION

Current treatment of cervical and lumbar degenerative disease requires interbody fusion to maintain decompression and to promote fusion and reduce the incidence of fusion failure through improvements in implant material, design, internal structure, and function. However, interbody fusion is not an optimal solution for treating vertebral instability.Abbreviations: ACDF, Anterior cervical discectomy and fusion; ALIF, anterior lumbar interbody fusion; Axi-aLIF, axial lumbar interbody fusion; BAK fusion cage, Bagby and Kuslich fusion cage; CADR, cervical artificial disc replacement; DBM, decalcified bone matrix; HA, hydroxyapatite; LLIF/XLIF, lateral or extreme lateral interbody fusion; MIS-TLIF, minimally invasive transforaminal lumbar interbody fusion; OLIF/ATP, oblique lumbar interbody fusion/anterior to psoas; PEEK, Poly-ether-ether-ketone; PLIF, posterior lumbar interbody fusion; ROI-C, Zero-profile Anchored Spacer; ROM, range of motion; SLM, selective melting forming; TLIF, transforaminal lumbar interbody fusion or.

Comparison of Fusion versus Nonunion After 4-Level and 5-Level Anterior Cervical Diskectomy and Fusion With Anterior Plate Fixation

BACKGROUND

Nonunion remains a concern in multilevel anterior cervical discectomy and fusion (ACDF), yet there are limited data on nonunion after 4 to 5-level ACDF. In fact, the largest series on 4-level or 5-level ACDF focused specifically on the swallowing outcomes.

OBJECTIVE

To assess nonunion after 4 to 5-level ACDF.

METHODS

Forty-one patients treated with 4 to 5-level ACDF with minimum of 12-month radiographic follow-up were retrospectively reviewed. Nonunion was found in 25 patients (61%) and 42 levels (25%) and complete fusion in 16 (39%) patients and 126 levels (75%). The 2 groups were further compared.

RESULTS

One-level nonunion was by far the most common pattern compared with multilevel nonunion. Nonunion occurred more frequently at the caudal than the cranial or middle segments ( P < .0001). There were significantly more subsidence ( P < .0001) and screw fractures/pullouts ( P < .0001) in the nonunion compared with the fusion group. The symptomatic patients were significantly younger than the asymptomatic patients ( P = .044). The symptomatic levels were significantly more than asymptomatic levels ( P = .048). Equal proportion of patients implanted with allograft and polyetheretherketone had nonunion. However, there were markedly more nonunion than fused levels with allograft and more fused than nonunion levels with polyetheretherketone ( P = .023). The reoperation rate was 24.4% and mostly due to nonunion. There were no reoperations within 90 days of the primary surgery.

CONCLUSION

The nonunion rate for 4-level and 5-level ACDF may be higher than previously reported. Symptomatic nonunion remains a major reason for reoperation after multilevel ACDF. Baseline characteristics that negatively affect fusion may be obviated by careful patient selection.

Predictive nomogram of cage nonunion after anterior cervical discectomy and fusion: A retrospective study in a spine surgery center

The cage nonunion may cause serious consequences, including recurrent pain, radiculopathy, and kyphotic deformity. The risk factors for nonunion following anterior cervical discectomy and fusion (ACDF) are controversial. The aim of the study is to investigate the risk factors for nonunion in cervical spondylotic cases after ACDF. We enrolled 58 and 692 cases in the nonunion and union group respectively and followed up the cases at least 6 months. Patient demographic information, surgical details, cervical sagittal parameters, and the serum vitamin D level were collected. A logistic regression was performed to determine the independent predictors for nonunion, which were used for establishing a nomogram. In order to estimate the reliability and the net benefit of nomogram, we applied a receiver operating characteristic curve analysis, calibration curves and plotted decision curves. Using the multivariate logistic regression, we found that age (odds ratio [OR] = 1.16, P < .001), smoking (OR = 3.41, P = .001), angle of C2 to C7 (OR = 1.53, P < .001), number of operated levels (2 levels, OR = 0.42, P = .04; 3 levels, OR = 1.32, P = .54), and serum vitamin D (OR = 0.81, P < .001) were all significant predictors of nonunion (Table 3). The area under the curve of the model training cohort and validation cohort was 0.89 and 0.87, respectively. The calibration curves showed that the predicted outcome fitted well to the observed outcome in the training cohort (P = .102,) and validation cohort (P = .125). The decision curves showed the nomogram had more benefits than the All or None scheme if the threshold probability is >10% and <100% in training cohort and validation cohort. We found that age, smoking, angle of C2 to C7, number of operated levels, and serum vitamin D were all significant predictors of nonunion.

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.

Morphologic Change of CorticoCancellous Allograft Used for Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim of this study was to evaluate the incidence and clinical implications of graft morphologic changes in corticocancellous allografts used for anterior cervical discectomy and fusion (ACDF), such as graft resorption or fracture.

SUMMARY OF BACKGROUND DATA

Although cortico-cancellous allograft is one of the most commonly used interbody spacer for ACDF, clinical implications of allograft resorption or fracture is unclear.

METHODS

One-hundred and thirty-eight consecutive patients who underwent ACDF for degenerative cervical myelopathy or radiculopathy were retrospectively reviewed. Patients with allograft morphologic changes, including graft resorption and fracture (morphologic change group), were compared with patients without morphologic changes (unchanged group). Furthermore, operated segments with morphologic changes were compared with unchanged segments. Patient characteristics, cervical lordosis, segmental lordosis, fusion, subsidence, neck pain visual analogue scale (VAS), arm pain VAS, and neck disability index (NDi) scores were evaluated.

RESULTS

Ninety patients (149 segments) were included in the study. Allograft resorption or fracture was detected in 46 (51.1%) patients and 81 (54.3%) segments, respectively. The fusion rate of morphologic change segments was significantly lower than that of the unchanged segments (P < 0.001). Furthermore, segments with morphologic changes had significantly higher rates of subsidence compared to unchanged segments ( P < 0.001). Segmental lordosis at the final follow-up was significantly smaller in the morphologic change segments ( P < 0.001). Neck pain VAS, arm pain VAS, and NDI scores did not demonstrate significant intergroup differences.

CONCLUSION

Corticocancellous allograft demonstrated a high rate of graft morphologic change (54.3%). Graft resorption or fracture was associated with increased pseudarthrosis, subsidence, and decreased postoperative segmental lordosis; however, the clinical results were not significantly affected. Caution is needed when choosing to use corticocancellous allografts for ACDF due to the high rate of graft resorption or fracture and the negative implications of these risks.