Alternative grafts in anterior cervical fusion

The fusion rates at different times of cortical iliac crest autograft or allograft compared with cages after anterior cervical discectomy and fusion: a meta-analysis

OBJECTIVE

The cortical iliac crest autograft (CICA)/structural allograft (SA) has still been recognized as the gold standard for the ACDF technique for its high degree of histocompatibility and osteoinduction ability though the flourishing and evolving cage development. However, there was no further indication for using CICA/SA in ACDF based on basic information of inpatients. Our operative experience implied that applying CICA/SA has an advantage on faster fusion but not the long-term fusion rate. Therefore, our study aimed to compare the fusion rates between CICA and cage, between SA and cage, and between CICA/CA and cage.

METHODS

Based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), a comprehensive literature search of electronic databases including PubMed, Embase, Cochrane Library and Web of Science was conducted to identify these clinical trials that investigated the postoperative 3, 6, 12 and 24 months fusion rates of CICA/structural SA versus cage. Assessment of risk of bias, data extraction and statistical analysis were then carried out by two independent authors with the resolve-by-consensus method. The primary outcome was fusion rate at 3, 6, 12 and 24 months postoperatively. The secondary outcomes were also meta-analyzed such as hardware complications, operative duration and hospitalization time. Our meta-analysis was registered with PROSPERO (Identifier: CRD42022345247).

RESULT

A total of 3451 segments (2398 patients) derived from 34 studies were included after the screening of 3366 articles. The segmental fusion rates of CICA were higher than cages at 3 (P = 0.184, I2 = 40.9%) and 6 (P = 0.147, I2 = 38.8%) months postoperatively, but not 12 (P = 0.988, I2 = 0.0%) and 24 (P = 0.055, I2 = 65.6%) months postoperatively. And there was no significant difference in segmental fusion rates between SA and cage at none of 3 (P = 0.047, I2 = 62.2%), 6 (P = 0.179, I2 = 41.9%) and 12 (P = 0.049, I2 = 58.0%) months after operations. As for secondary outcomes, the CICA was inferior to cages in terms of hardware complications, operative time, blood loss, hospitalization time, interbody height, disk height and Odom rating. The hardware complication of using SA was significantly higher than the cage, but not the hospitalization time, disk height, NDI and Odom rating.

CONCLUSION

Applying CICA has an advantage on faster fusion than using a cage but not the long-term fusion rate in ACDF. Future high-quality RCTs regarding the hardware complications between CICA and cage in younger patients are warranted for the deduced indication.

AO Spine Guideline for the Use of Osteobiologics (AOGO) in Anterior Cervical Discectomy and Fusion for Spinal Degenerative Cases

STUDY DESIGN

Guideline.

OBJECTIVES

To develop an international guideline (AOGO) about the use of osteobiologics in anterior cervical discectomy and fusion (ACDF) for treating degenerative spine conditions.

METHODS

The guideline development process was guided by AO Spine Knowledge Forum Degenerative (KF Degen) and followed the Guideline International Network McMaster Guideline Development Checklist. The process involved 73 participants with expertise in degenerative spine diseases and surgery from 22 countries. Fifteen systematic reviews were conducted addressing respective key topics and evidence was collected. The methodologist compiled the evidence into GRADE Evidence-to-Decision frameworks. Guideline panel members judged the outcomes and other criteria and made the final recommendations through consensus.

RESULTS

Five conditional recommendations were created. A conditional recommendation is about the use of allograft, autograft or a cage with an osteobiologic in primary ACDF surgery. Other conditional recommendations are about the use of osteobiologic for single- or multi-level ACDF, and for hybrid construct surgery. It is suggested that surgeons use other osteobiologics rather than human bone morphogenetic protein-2 (BMP-2) in common clinical situations. Surgeons are recommended to choose 1 graft over another or 1 osteobiologic over another primarily based on clinical situation, and the costs and availability of the materials.

CONCLUSION

This AOGO guideline is the first to provide recommendations for the use of osteobiologics in ACDF. Despite the comprehensive searches for evidence, there were few studies completed with small sample sizes and primarily as case series with inherent risks of bias. Therefore, high-quality clinical evidence is demanded to improve the guideline.

Structural Allograft Versus Mechanical Interbody Devices Augmented With Osteobiologics in Anterior Cervical Discectomy and Fusion: A Systematic Review

STUDY DESIGN

Systematic Literature Review.

OBJECTIVE

Perform a systematic review evaluating postoperative fusion rates for anterior cervical discectomy and fusion (ACDF) using structural allograft vs various interbody devices augmented with different osteobiologic materials.

METHODS

Comprehensive literature search using PubMed, Embase, The Cochrane Library, and Web of Science was performed. Included studies were those that reported results of 1-4 levels ACDF using pure structural allograft compared with a mechanical interbody device augmented with an osteobiologic. Excluded studies were those that reported on ACDF with cervical corpectomy; anterior and posterior cervical fusions; circumferential (360° or 540°) fusion or revision ACDF for nonunion or other conditions. Risk of bias was determined using the Cochrane review guidelines.

RESULTS

8 articles reporting fusion rates of structural allograft and an interbody device/osteobiologic pair were included. All included studies compared fusion rates following ACDF among structural allograft vs non-allograft interbody device/osteobiologic pairs. Fusion rates were reported between 84% and 100% for structural allograft, while fusion rates for various interbody device/osteobiologic combinations ranged from 26% to 100%. Among non-allograft cage groups fusion rates varied from 73-100%. One study found PEEK cages filled with combinations of autograft, allograft, and demineralized bone matrix (DBM) to have an overall fusion rate of 26%. In one study comparing plate and zero-profile constructs, there was no difference in fusion rates for two-level fusions.

CONCLUSION

There was limited data comparing fusion outcomes of patients undergoing ACDF using structural allograft vs interbody devices augmented with osteobiologic materials to support superiority of one method.

Anterior Cervical Discectomy and Fusion Performed Using a CaO-SiO2-P2O5-B2O3 Bioactive Glass Ceramic or Polyetheretherketone Cage Filled with Hydroxyapatite/β-Tricalcium Phosphate: A Prospective Randomized Controlled Trial

A CaO-SiO₂-P₂O₅-B₂O₃ bioactive glass-ceramic (BGS-7) spacer provides high mechanical stability, produces a chemical bond to the adjacent endplate, and facilitates fusion after spine surgery. This prospective, randomized, single-blind, non-inferiority trial aimed to evaluate the radiographic outcomes and clinical efficacy of anterior cervical discectomy and fusion (ACDF) using a BGS-7 spacer for treating cervical degenerative disorders. Thirty-six patients underwent ACDF using a BGS-7 spacer (Group N), and 40 patients underwent ACDF using polyetheretherketone (PEEK) cages filled with a mixture of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) for the treatment of cervical degenerative disorders. The spinal fusion rate was assessed 12 months postoperatively using three-dimensional computed tomography (CT) and dynamic radiographs. Clinical outcomes included patient-reported outcome measures, visual analog scale scores for neck and arm pain, and scores from the neck disability index (NDI), European Quality of Life-5 Dimensions (EQ-5D), and 12-item Short Form Survey (SF-12v2). All participants were randomly assigned to undergo ACDF using either a BGS-7 spacer or PEEK cage filled with HA and β-TCP. The primary outcome was the fusion rate on CT scan image at 12 months after ACDF surgery based on a per-protocol strategy. Clinical outcomes and adverse events were also assessed. The 12-month fusion rates for the BGS-7 and PEEK groups based on CT scans were 81.8% and 74.4%, respectively, while those based on dynamic radiographs were 78.1% and 73.7%, respectively, with no significant difference between the groups. There were no significant differences in the clinical outcomes between the two groups. Neck pain, arm pain, NDI, EQ-5D, and SF-12v2 scores significantly improved postoperatively, with no significant differences between the groups. No adverse events were observed in either group. In ACDF surgery, the BGS-7 spacer showed similar fusion rates and clinical outcomes as PEEK cages filled with HA and β-TCP.

A Novel Cervical Vertebral Bone Quality Score Independently Predicts Cage Subsidence After Anterior Cervical Diskectomy and Fusion

BACKGROUND

Surgeons can preoperatively assess bone quality using dual-energy X-ray absorptiometry or computed tomography; however, this is not feasible for all patients. Recently, a MRI-based scoring system was used to evaluate the lumbar spine's vertebral bone quality.

OBJECTIVE

To create a similar MRI-based scoring system for the cervical spine (C-VBQ), correlate C-VBQ scores with computed tomography-Hounsfield units (HU), and evaluate the utility of this scoring system to independently predict cage subsidence after single-level anterior cervical diskectomy and fusion (ACDF).

METHODS

Demographic, procedure-related, and radiographic data were collected for patients. Pearson correlation test was used to determine the correlation between C-VBQ and HU. Cage subsidence was defined as ≥3 mm loss of fusion segmental height. A multivariate logistic regression model was built to determine the correlation between potential risk factors for subsidence.

RESULTS

Of 59 patients who underwent single-level ACDF, subsidence was found in 17 (28.8%). Mean C-VBQ scores were 2.22 ± 0.36 for no subsidence levels and 2.83 ± 0.38 ( P < .001) for subsidence levels. On multivariate analysis, a higher C-VBQ score was significantly associated with subsidence (odds ratio = 1.85, 95% CI = 1.39-2.46, P < .001) and was the only significant independent predictor of subsidence after ACDF. There was a significant negative correlation between HU and C-VBQ (r 2 = -0.49, P < .001).

CONCLUSION

We found that a higher C-VBQ score was significantly associated with cage subsidence after ACDF. Furthermore, there was a significant negative correlation between C-VBQ and HU. The C-VBQ score may be a valuable tool for assessing preoperative bone quality and independently predicting cage subsidence after ACDF.

Feasibility and safety of a CaO-SiO2-P2O5-B2O3 bioactive glass ceramic spacer in posterior lumbar interbody fusion compared with polyetheretherketone cage: a prospective randomized controlled trial

PURPOSE

The CaO-SiO2-P2O5-B2O3 glass-ceramic (BGS-7) spacer is a recently developed spacer that shows chemical bonding to bone with high mechanical stability. Further, this spacer achieves similar results to those of titanium cages. However, evidence regarding the advantages of the BGS-7 spacer is weak compared to polyetheretherketone (PEEK) cage. A randomized controlled trial is therefore warranted. The purpose of this study was to compare the radiographic and clinical efficacies and safety of the BGS-7 spacer compared to those of the PEEK cage in patients who underwent posterior lumbar interbody fusion (PLIF).

METHODS

The 54 participants who required one- or two-level PLIF due to lumbar degenerative disorders were randomly assigned to receive a BGS-7 spacer or PEEK cage. Visual analog scale (VAS), Oswestry Disability Index (ODI), European Quality of Life-5 Dimensions (EQ-5D), and painDETECT score were evaluated before surgery and at 3, 6, and 12 months after surgery. The fusion rate, degree of osteolysis, cage migration, and subsidence around the cage (spacer) were evaluated on computer tomography (CT) images at 12 months after surgery.

RESULTS

The 12-month fusion rates were 77.8% in the BGS-7 spacer group and 81.0% in the PEEK cage group, with no significant difference (p = 0.807). The result regarding the non-inferiority of BGS-7 spacer was inconclusive. The linear mixed model showed no significant intervention effect in VAS, ODI, EQ-5D, and painDETECT score at the 3-, 6-, or 12-month follow-up. In addition, we found no significant between-group differences in the extent of osteolysis, spacer migration. However, the subsidence around the cage was significantly lower in the BGS-7 spacer group.

CONCLUSIONS

This trial found similar fusion rates, and clinicoradiographic outcomes between the BGS-7 spacer and PEEK cage for PLIF. However, the non-inferiority was inconclusive. Safety concerns regarding fracture and migration of the BGS-7 spacer must be considered. Thus, the BGS-7 spacer design for PLIF surgery should be modified before further clinical use.

Biomechanical Analysis of Two-Level Novel Cage-Type Implant for Anterior Cervical Discectomy and Fusion: A Finite Element Analysis

One of the standard treatments for spinal diseases is anterior cervical discectomy and fusion (ACDF). ACDF is a secure and successful operation that prevents patients to improve their pain and function. The mechanical goal of the ACDF is to prevent motion between adjoining vertebrae by a novel cage-screw implant. The objective of this study is to analyze the biomechanical flexibility in terms of the range of motion (ROM) of two-level ACDF fixation using the finite element method (FEM). A CT scan-based FEM model of the cervical spine (C2-C7) is used and two-level cage is implanted at C4-C6 segments. A 50-N compressive force and 1-Nm moment are applied on C2 vertebrae and C7 is fixed in all directions. The ROM at two-level fixation (C4-C5-C6) is reduced by 55 to 88% compared with intact spine during all physiological movement. The ROM slightly increase (3-9%) at the adjacent segment. The maximum von Mises stress variations are 25-65 MPa during flexion-extension, lateral bending, and axial rotations under given loading. The maximum von Mises stress found in cage and screw is below the yield stress during all physiological movement.

Cage-screw and anterior plating combination reduces the risk of micromotion and subsidence in multilevel anterior cervical discectomy and fusion-a finite element study

BACKGROUND CONTEXT

Anterior cervical discectomy and fusion (ACDF) is widely used to treat patients with spinal disorders, where the cage is a critical component to achieve satisfactory fusion results. However, it is still not clear whether a cage with screws or without screws will be the best choice for long-term fusion as the micromotion (sliding distance) and subsidence (penetration) of the cage still take place repeatedly.

PURPOSE

This study aims to examine the effect of cage-screws on the biomechanical characteristics of the human spine, implanted cage, and associate hardware by comparing the micromotion and subsidence.

STUDY DESIGN

A finite element (FE) analysis study.

METHODS

A FE model of a C3-C5 cervical spine with ACDF was developed. The spinal segment was modeled with the removal of the anterior longitudinal ligament (ALL), posterior longitudinal ligament (PLL), and discectomy was then implanted with a cage-screw system. Three models were analyzed: the first was the original spine (S1 model), the second, S2, was implanted with cages and anterior plating, and the third, S3, was implanted with a cage-screw system in addition to the anterior plate. All investigations were under 1 N•m in flexion, extension, lateral bending, and axial rotation situations.

RESULTS

Finite element analysis (FEA) demonstrated that range of motion (ROM) at C3-C4 in the S2 model was significantly reduced more than that in the S3 model, while the ROM at both C4-C5 in the S3 model was reduced more than that in the S2 model in all simulations. The ROM at C3-C5 in the S1 model was reduced by over 5° in the S2 and S3 models in all loading conditions. The micromotion and subsidence at all contacts of C3-C5 in the S3 model were lower than that in the S2 model in all flexion, extension, bending, and axial simulations. The subsidence and micromotion could be seen in the barrier area of the S2 model, while they occurred near the edge of the screw in the S3 model.

CONCLUSIONS

These results showed that the cage-screw and anterior plating combination has promising potential to reduce the risk of micromotion and subsidence of implanted cages in two or more level ACDFs.

CLINICAL SIGNIFICANCE

The use of double segmental fixation with cage-screw anterior plating combination constructs may increase the stiffness of the construct and reduce the incidence of clinical and radiographic pseudarthrosis following multilevel ACDF, which in turn, could decrease the need for revision surgeries or supplemental posterior fixation.

Early Recurrent Symptoms After Anterior Cervical Discectomy and Fusion Done for Myelopathy

We present a unique case with early recurrent myelopathic clinical manifestations following anterior cervical discectomy and fusion; however, he had an eventual diagnosis of multiple sclerosis rather than any residual cord compression on repeat imaging.

Analysis of the Variables Affecting the Incidence, Location, and Severity of Cage Subsidence Following Anterior Cervical Discectomy and Fusion Operation

BACKGROUND

For surgical management of degenerative cervical spine disease with myeloradiculopathy, stand-alone cages are frequently used in 1- and 2-level anterior cervical discectomy and fusion (ACDF) operations with a paucity of literature on factors influencing cage subsidence. The aim of this study was to analyze the variables affecting the incidence, location, and severity of cage subsidence.

METHODS

Retrospective review of prospectively collected data of 77 patients (95 levels) undergoing ACDF surgery was conducted. Variables analyzed were age, gender, sagittal alignment, maximum disc height (superior, inferior, and procedure levels), cage size, shape, location, degree of subsidence (minor <2 mm, mild 2-4 mm, moderate 5-7.5 mm, severe >7.5 mm) and location of subsidence.

RESULTS

The incidence of cage subsidence was 34% (32 levels), and 91% were minor or mild. Significantly lower mean maximum height of the inferior disc compared to the nonsubsidence group (5.17 versus 5.96; P = 0.0025) was recorded. Significantly greater incidence of subsidence (40%) was recorded in patients with abnormal cervical spine alignment (focal or diffuse kyphosis) versus 18% with normal alignment (P = 0.02). Greater incidence of subsidence was recorded with more anterior positioned cages (52%; p=0.01). No statistical significance was found for age, gender, superior disc height, or cage shape/size.

CONCLUSIONS

Greater incidence of cage subsidence is significantly associated with a lower maximum disc height of the disc below the operated level (<5.5 mm), abnormal sagittal alignment, and more anteriorly positioned cages. We found that the vast majority of cage subsidence was focal, minor to mild, without having any immediate or late clinical implications in terms of need for revision surgery.

PEEK interbody devices for multilevel anterior cervical discectomy and fusion: association with more than 6-fold higher rates of pseudarthrosis compared to structural allograft

OBJECTIVE

Common interbody graft options for anterior cervical discectomy and fusion (ACDF) include allograft and polyetheretherketone (PEEK). PEEK has gained popularity due to its radiolucent properties and a modulus of elasticity similar to that of bone. PEEK devices also result in higher billing costs than allograft, which may drive selection. A previous study found a 5-fold higher rate of pseudarthrosis with the use of PEEK devices compared with structural allograft in single-level ACDF. Here the authors report on the occurrence of pseudarthrosis with PEEK devices versus structural allograft in patients who underwent multilevel ACDF.

METHODS

The authors retrospectively reviewed 81 consecutive patients who underwent a multilevel ACDF and had radiographic follow-up for at least 1 year. Data were collected on age, sex, BMI, tobacco use, pseudarthrosis, and rate of reoperation for pseudarthrosis. Logistic regression was used for data analysis.

RESULTS

Of 81 patients, 35 had PEEK implants and 46 had structural allograft. There were no significant differences between age, sex, smoking status, or BMI in the 2 groups. There were 26/35 (74%) patients with PEEK implants who demonstrated radiographic evidence of pseudarthrosis, compared with 5/46 (11%) patients with structural allograft (p < 0.001, OR 22.2). Five patients (14%) with PEEK implants required reoperation for pseudarthrosis, compared with 0 patients with allograft (p = 0.013).

CONCLUSIONS

This study reinforces previous findings on 1-level ACDF outcomes and suggests that the use of PEEK in multilevel ACDF results in statistically significantly higher rates of radiographic pseudarthrosis and need for revision surgery than allograft. Surgeons should consider these findings when determining graft options, and reimbursement policies should reflect these discrepancies.

Complications of anterior cervical spine surgery: a systematic review of the literature

The anterior approach to the cervical spine is commonly utilized for a variety of degenerative, traumatic, neoplastic, and infectious indications. While many potential complications overlap with those of the posterior approach, the distinct anatomy of the anterior neck also presents a unique set of hazards. We performed a systematic review of the literature to assess the etiology, presentation, natural history, and management of these complications. Following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), a PubMed search was conducted to evaluate clinical studies and case reports of patients who suffered a complication of anterior cervical spine surgery. The search specifically included articles concerning adult human subjects, written in the English language, and published from 1989 to 2019. The PubMed search yielded 240 articles meeting our criteria. The overall rates of complications were as follows: dysphagia 5.3%, esophageal perforation 0.2%, recurrent laryngeal nerve palsy 1.3%, infection 1.2%, adjacent segment disease 8.1%, pseudarthrosis 2.0%, graft or hardware failure 2.1%, cerebrospinal fluid leak 0.5%, hematoma 1.0%, Horner syndrome 0.4%, C5 palsy 3.0%, vertebral artery injury 0.4%, and new or worsening neurological deficit 0.5%. Morbidity rates in anterior cervical spine surgery are low. Nevertheless, the unique anatomy of the anterior neck presents a wide variety of potential complications involving vascular, aerodigestive, neural, and osseous structures.

A Biomechanical Evaluation of a Next-Generation Integrated and Modular ACDF Device Possessing Full-Plate, Half-Plate, and No-Profile Fixation Iterations

STUDY DESIGN

In vitro biomechanical study.

OBJECTIVES

The objective of this in vitro biomechanical range-of-motion (ROM) study was to evaluate spinal segmental stability following fixation with a novel anterior cervical discectomy and fusion (ACDF) device ("novel device") that possesses integrated and modular no-profile, half-plate, and full-plate fixation capabilities.

METHODS

Human cadaveric (n = 18, C3-T1) specimens were divided into 3 groups (n = 6/group). Each group would receive one novel device iteration. Specimen terminal ends were potted. Each specimen was first tested in an intact state, followed by anterior discectomy (C5/C6) and iterative instrumentation. Testing order: (1) novel device (group 1, no-profile; group 2, half-plate; group 3, full-plate); (2) novel device (all groups) with lateral mass screws (LMS); (3) traditional ACDF plate + cage; (4) traditional ACDF plate + cage + LMS. A 2 N·m moment was applied in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) via a kinematic testing machine. Segmental ROM was tracked and normalized to intact conditions. Comparative statistical analyses were performed.

RESULTS

Key findings: (1) the novel half- and full-plate constructs provided comparable reduction in FE and LB ROM to that of traditional plated ACDF (P ≥ .05); (2) the novel full-plate construct significantly exceeded all other anterior-only constructs (P ≤ .05) in AR ROM reduction; and (3) the novel half-plate construct significantly exceeded the no-profile construct in FE (P < .05).

CONCLUSIONS

The novel ACDF device may be a versatile alternative to traditional no-profile and independent plating techniques, as it provides comparable ROM reduction in all principle motion directions, across all device iterations.

Clinical and radiographic evaluation of bioactive glass in posterior cervical and lumbar spinal fusion

INTRODUCTION

Spinal surgery of degenerative painful segments is a valuable treatment option in the management of chronic cervical and low back pain. The surgery consists in stabilizing and fusing painful vertebral segment(s). The objective of the study was to report our experience with 45S5 bioactive glass (BAG) to obtain inter-vertebral fusion in the context of posterior spine surgery.

MATERIAL AND METHOD

In this retrospective study, 30 patients with a wide range of degenerative and traumatic conditions of the cervical or lumbar spine underwent spinal fusion utilizing a synthetic bone graft substitute of BAG (GlassBone™, Noraker, Lyon-Villeurbanne, France). The pain was evaluated by VAS score, and graft consolidation was assessed on according radiographic images at 1-year post-op.

RESULTS

All patients underwent posterior spinal fusion either in the cervical or the thoraco-lumbar spine. Multi-level fusions represented the majority of the cohort (43% of patients with more than seven levels treated). Radiographic imaging demonstrated excellent fusion rates (93%) at final follow-up, equivalent to the outcomes reported in the literature for autogenous bone, with excellent bone bridging and no spinal implant loosening. Only two cases of non-union were encountered. Additionally, 90% of the patients demonstrated recovery at 1 year after surgery with a pain reduction of 60%.

CONCLUSION

The results of this retrospective study suggest that the 45S5 BAG may be an interesting alternative option to autologous graft, in terms of safety and bone fusion efficiency.

LEVEL OF EVIDENCE

IV Retrospective study.

Fivefold higher rate of pseudarthrosis with polyetheretherketone interbody device than with structural allograft used for 1-level anterior cervical discectomy and fusion

In BriefThe authors examined fusion rates after single-level anterior cervical discectomy and fusion, comparing use of a structural allograft with use of polyetheretherketone (PEEK) interbody devices packed with bone graft. The results demonstrate superior results of structural allograft in terms of arthrodesis rates and reoperation rates. Currently, reimbursement rates substantially favor the use of PEEK and other synthetic devices, which the authors believe should be changed based on the results of this study.

Does pedicle screw fixation of the subaxial cervical spine provide adequate stabilization in a multilevel vertebral body fracture model? An in vitro biomechanical study

BACKGROUND

Cervical vertebral body fractures generally are treated through an anterior-posterior approach. Cervical pedicle screws offer an alternative to circumferential fixation. This biomechanical study quantifies whether cervical pedicle screws alone can restore the stability of a three-column vertebral body fracture, making standard 360° reconstruction unnecessary.

METHODS

Range of motion (2.0 Nm) in flexion-extension, lateral bending, and axial rotation was tested on 10 cadaveric specimens (five/group) at C2-T1 with a spine kinematics simulator. Specimens were tested for flexibility of intact when a fatigue protocol with instrumentation was used to evaluate construct longevity. For a C4-6 fracture, spines were instrumented with 360° reconstruction (corpectomy spacer + plate + lateral mass screws) (Group 1) or cervical pedicle screw reconstruction (C3 and C7 only) (Group 2).

FINDINGS

Results are expressed as percentage of intact (100%). In Group 1, 360° reconstruction resulted in decreased motion during flexion-extension, lateral bending, and axial rotation, to 21.5%, 14.1%, and 48.6%, respectively, following 18,000 cycles of flexion-extension testing. In Group 2, cervical pedicle screw reconstruction led to reduced motion after cyclic flexion-extension testing, to 38.4%, 12.3%, and 51.1% during flexion-extension, lateral bending, and axial rotation, respectively.

INTERPRETATION

The 360° stabilization procedure provided the greatest initial stability. Cervical pedicle screw reconstruction resulted in less change in motion following cyclic loading with less variation from specimen to specimen, possibly caused by loosening of the shorter lateral mass screws. Cervical pedicle screw stabilization may be a viable alternative to 360° reconstruction for restoring multilevel vertebral body fracture.

Clinical Application of Ceramics in Anterior Cervical Discectomy and Fusion: A Review and Update

STUDY DESIGN

Narrative review.

OBJECTIVES

Anterior cervical discectomy and fusion (ACDF) is a reliable procedure, commonly used for cervical degenerative disc disease. For interbody fusions, autograft was the gold standard for decades; however, limited availability and donor site morbidities have led to a constant search for new materials. Clinically, it has been shown that calcium phosphate ceramics, including hydroxyapatite (HA) and tricalcium phosphate (TCP), are effective as osteoconductive materials and bone grafts. In this review, we present the current findings regarding the use of ceramics in ACDF.

METHODS

A review of the relevant literature examining the clinical use of ceramics in anterior cervical discectomy and fusion procedures was conducted using PubMed, OVID and Cochrane.

RESULT

HA, coralline HA, sandwiched HA, TCP, and biphasic calcium phosphate ceramics were used in combination with osteoinductive materials such as bone marrow aspirate and various cages composed of poly-ether-ether-ketone (PEEK), fiber carbon, and titanium. Stand-alone ceramic spacers have been associated with fracture and cracks. Metallic cages such as titanium endure the risk of subsidence and migration. PEEK cages in combination with ceramics were shown to be a suitable substitute for autograft.

CONCLUSION

None of the discussed options has demonstrated clear superiority over others, although direct comparisons are often difficult due to discrepancies in data collection and study methodologies. Future randomized clinical trials are warranted before definitive conclusions can be drawn.

Anterior cervical discectomy and fusion (ACDF) autograft versus graft substitutes: what do patients prefer?-A clinical study

BACKGROUND

Patient dissatisfaction with donor site morbidity has led to the search for alternative grafting options and techniques. This report compares patient satisfaction rates between autograft and graft substitutes for anterior cervical discectomy and fusion (ACDF).

METHODS

This study was performed with the approval of the local area health network ethics committee. Over a 9-year period, the author performed 574 ACDF procedures (697 levels). Of these, 22 patients had previous surgery with autograft, with a subsequent ACDF procedure performed using a graft substitute. Patients rated their satisfaction with pain, recovery, and preference of autograft versus a bone graft substitute. Graft substitutes used include: tricalcium phosphate/hydroxyapatite (TCP/HA) composite and iFactor placed within a polyetheretherketone (PEEK) cage.

RESULTS

Results demonstrated that 21/22 patients achieved a solid fusion with the graft substitute. A total of 20/22 patients rated the autograft incision more painful than the anterior cervical incision, and 21/22 preferred the graft substitute. Three patients had adjacent segment disc replacement performed after autograft/ACDF. All patients reported preference for the total disc replacement (TDR) procedure in terms of recovery and postoperative pain.

CONCLUSIONS

Patient satisfaction with bone graft substitutes is very high compared with autograft with all but one (21/22) preferring the graft substitute option. The author questions the traditional recommendation that autograft is the "gold standard" for ACDF. In modern age of graft substitutes, autograft should not be considered the gold standard, but an index option between other options for comparison.

Subsidence after single-level anterior cervical fusion with a stand-alone cage

To investigate the risk factors for subsidence in patients treated with stand-alone anterior cervical discectomy and fusion (ACDF) using polyetheretherketone (PEEK) cages for single-level degenerative cervical disease. Seventy-seven consecutive patients who underwent single-level stand-alone ACDF with a PEEK cage between 2005 and 2012 were included. Subsidence was defined as a decrease in the interbody height of more than 3mm on radiographs at the 1-year follow-up compared with that in the immediate post-operative image. Patients were divided into the subsidence and non-subsidence groups. The following factors were investigated in relation to the occurrence of subsidence: age, pre-operative overall cervical sagittal angle, segmental angle of the operated level, interbody height, cage height, cage devices and cage location (distance between anterior margin of the body endplate and that of the cage). The clinical outcomes were assessed with visual analog scale, modified Japanese Orthopedic Association score and neck disability index. Twenty-six out of the 77 (33.8%) patients had radiological signs of cage subsidence. Solid fusion was achieved in 25 out of the 26 patients (96.2%) in the subsidence group and in 47 out of the 51 patients (92.2%) in the non-subsidence group. More than 3mm distance between anterior margin of the vertebral body and that of the cage was significantly associated with subsidence (p<0.05). However, subsidence did not correlate with fusion rate or clinical outcomes. Cage location was the only significant risk factor. Therefore, cage location should be taken into consideration during stand-alone ACDF using PEEK cages.

A microsurgical anterior cervical approach and the immediate impact of mechanical retractors: A case control study

Introduction:

A microsurgical anterior cervical approach with discectomy and fusion (MACDF) is one of the most widely used procedures for treating radicular disorders. This approach is highly successful; however, it is not free from complications. These can be associated with soft tissue injuries.

Aim of the Study:

The recognition of the risks for these complications should be identified for timely prevention and safe treatment.

Materials and Methods:

Study Design: Retrospective case control study. This study includes a retrospective case series of 37 patients, paying special attention to immediate complications related to the use of mechanical retraction of soft tissue (dysphagia, dysphonia, esophageal lesions and local hematoma); and a comparative analysis of the outcomes after changes in the retraction method.

Results:

All selected cases had a positive neurological symptom response in relation to neuropathic pain. Dysphagia and dysphonia were found during the first 72 h in 94.1% of the cases in which automatic mechanical retraction was used for more than one hour during the surgical procedure. A radical change was noted in the reduction of the symptoms after the use of only manual protective blades without automatic mechanical retraction: 5.1% dysphagia and 0% dysphonia in the immediate post-operative period, P = 0.001.

Conclusions:

Soft tissue damage due to the use of automatic retractors in MACDF is not minor and leads to general discomfort in the patient in spite of good neurological results. These problems most often occur when automatic retractors are used continuously for more than 1 hour, as well as when they are used in multiple levels. Dysphagia, dysphonia and local pain decreased with the use of transient manual blades for retraction, and with intermittent release following minimally invasive principles.

The Effect of the PEEK Cage on the Cervical Lordosis in Patients Undergoing Anterior Cervical Discectomy

BACKGROUND:

Loss of cervical lordosis is a significant factor in the development of degeneration of the spine with aging. This degenerative changings of the cervical spine would cause pressure effect on the cervical root and/or medulla spinalis.

AIM:

Our goal is to understand the effect of the PEEK cage on cervical lordosis in the early postoperative period. Also, to interpret the effects of one- level, two- level, three-level and four- level disc pathologies on cervical lordosis.

MATERIAL AND METHODS:

We retrospectively investigated our archive, and we selected thirty-four patients undergoing anterior cervical discectomy and fusion with PEEK cage filled with demineralized bone matrix (ACDFP).

RESULTS:

We determined that ACDFP provides improvement in the cervical lordosis angle in both groups. Also, we found statistically significant difference between group 1 and 2 regarding causes of radiculomyelopathy statistically.

CONCLUSION:

We achieved better cervical lordotic angles at the postoperative period by implanting one-level, two-level, three-level or four-level PEEK cage filled with demineralized bone matrix. Also, the causes of cervical root and or medulla spinalis impingement were different in group1 and 2. While extruded cervical disc impingement was the first pathology in group 1, osteophyte formation was the first pathology in group 2.

ISASS Policy Statement - cervical interbody

Morgan Lorio, MD, FACS, Chair, ISASS Task Force on Coding & Reimbursement In 2011, CPT code 22551 was revised to combine or bundle CPT codes 63075 and 22554 when both procedures were performed at the same site/same surgical session. The add on code +22552 is used to report each additional interspace. 2014 heralded a downward pressure on this now prime target code (for non-coverage?) 22551 through an egregious insurer attempt to redefine cervical arthrodesis, effectively removing spine surgeon choice and altering best practice without clinical evidence. Currently, spine surgeons are equally split on the use of allograft versus cages for cervical arthrodesis. Structural allograft, CPT code 20931, is reported once per same surgical session, regardless of the number of allografts used. CPT code 22851 which is designated solely for cage use, has a higher reimbursement than structural allograft, and may be reported for each inner space. Hence, the rationale behind why some payers wrongly consider "spine cages NOT medically necessary for cervical fusion." A timely consensus paper summarizing spine surgeon purview on the logical progressive evolution of cervical interbody fusion for ISASS/IASP membership was strategically identified as an advocacy focus by the ISASS Task Force. ISASS appreciates the authors' charge with gratitude. This article has both teeth and transparent clinical real-world merit.

A Prospective Randomized Clinical Trial Comparing Bone Union Rate Following Anterior Cervical Discectomy and Fusion Using a Polyetheretherketone Cage: Hydroxyapatite/B-Tricalcium Phosphate Mixture versus Hydroxyapatite/Demineralized Bone Matrix Mixture

Study Design

Prospective randomized noninferiority trial.

Purpose

To evaluate whether the union rate of anterior cervical discectomy and fusion (ACDF) using a polyetheretherketone (PEEK) cage filled with a mixture of hydroxyapatite (HA) and demineralized bone matrix (DBM) is inferior to that of a mixture of β-tricalcium phosphate (β-TCP) and HA.

Overview of Literature

There have been no clinical trials investigating the outcomes of a mixture of HA and DBM in a PEEK cage in ACDF.

Methods

Eighty-five eligible patients were randomly assigned to group B (n=43), in which a PEEK cage with a mixture of HA and DBM was used, or group C (n=42), in which a PEEK cage with a mixture of HA and β-TCP was used. The primary study endpoint was the fusion rate, which was assessed with dynamic radiographs and computed tomography (CT) scans. Secondary endpoints included pain intensity using a visual analogue scale, functional outcome using a neck disability index score, laboratory tests of inflammatory profiles, and the infection rate.

Results

Seventy-seven patients (38 in group B and 39 in group C) were included in the final analysis. One year postoperatively, bone fusion was achieved in 87% of group B patients and 87% of group C patients on dynamic radiographs, and 87% of group B patients and 72% of group C patients on CT scans (p=1.00 and 0.16, respectively). There were also no between-groups differences with respect to the secondary endpoints.

Conclusions

A HA/DBM mixture inside a PEEK cage can provide noninferior outcomes compared to a HA/TCP mixture in ACDF.

Zero-profile hybrid fusion construct versus 2-level plate fixation to treat adjacent-level disease in the cervical spine

OBJECT

Single-level anterior cervical discectomy and fusion (ACDF) is an established surgical treatment for cervical myelopathy. Within 10 years of undergoing ACDF, 19.2% of patients develop symptomatic adjacent-level degeneration. Performing ACDF adjacent to prior fusion requires exposure and removal of previously placed hardware, which may increase the risk of adverse outcomes. Zero-profile cervical implants combine an interbody spacer with an anterior plate into a single device that does not extend beyond the intervertebral disc space, potentially obviating the need to remove prior hardware. This study compared the biomechanical stability and adjacent-level range of motion (ROM) following placement of a zero-profile device (ZPD) adjacent to a single-level ACDF against a standard 2-level ACDF.

METHODS

In this in vitro biomechanical cadaveric study, multidirectional flexibility testing was performed by a robotic spine system that simulates flexion-extension, lateral bending, and axial rotation by applying a continuous pure moment load. Testing conditions were as follows: 1) intact, 2) C5-6 ACDF, 3) C4-5 ZPD supraadjacent to simulated fusion at C5-6, and 4) 2-level ACDF (C4-6). The sequence of the latter 2 test conditions was randomized. An unconstrained pure moment of 1.5 Nm with a 40-N simulated head weight load was applied to the intact condition first in all 3 planes of motion and then using the hybrid test protocol, overall intact kinematics were replicated subsequently for each surgical test condition. Intersegmental rotations were measured optoelectronically. Mean segmental ROM for operated levels and adjacent levels was recorded and normalized to the intact condition and expressed as a percent change from intact. A repeated-measures ANOVA was used to analyze the ROM between test conditions with a 95% level of significance.

RESULTS

No statistically significant differences in immediate construct stability were found between construct Patterns 3 and 4, in all planes of motion (p > 0.05). At the operated level, C4-5, the zero-profile construct showed greater decreases in axial rotation (-45% vs -36%) and lateral bending (-55% vs -38%), whereas the 2-level ACDF showed greater decreases in flexion-extension (-40% vs -34%). These differences were marginal and not statistically significant. Adjacent-level motion was nearly equivalent, with minor differences in flexion-extension.

CONCLUSIONS

When treating degeneration adjacent to a single-level ACDF, a zero-profile implant showed stabilizing potential at the operated level statistically similar to that of the standard revision with a 2-level plate. Revision for adjacent-level disease is common, and using a ZPD in this setting should be investigated clinically because it may be a faster, safer alternative.

Graft inserter for anterior cervical fusion

The authors have developed a simple instrument for graft insertion in anterior cervical fusion. This device obviates the need for screw distraction of the adjacent vertebrae or the use of an impactor for insertion. This device simplifies graft insertion where the disc space is narrow, particularly in multilevel fusions, and reduces the risk of over-penetration of the graft.

Risk factors for subsidence in anterior cervical fusion with stand-alone polyetheretherketone (PEEK) cages: a review of 82 cases and 182 levels

INTRODUCTION

To determine risk factors for subsidence in patients treated with anterior cervical discectomy and fusion (ACDF) and stand-alone polyetheretherketone (PEEK) cages.

MATERIALS AND METHODS

Records of patients with degenerative spondylosis or traumatic disc herniation resulting in radiculopathy or myelopathy between C2 and C7 who underwent ACDF with stand-alone PEEK cages were retrospectively reviewed. Cages were filled with autogenous cancellous bone harvested from iliac crest or hydroxyapatite. Subsidence was defined as a decrease of 3 mm or more of anterior or posterior disc height from that measured on the postoperative radiograph. Eighty-two patients (32 males, 50 females; 182 treatment levels) were included in the analysis.

RESULTS

Most patients had 1-2 treatment levels (62.2 %), and 37.8 % had 3-4 treatment levels. Treatment levels were from C2-7. Of the 82 patients, cage subsidence occurred in 31 patients, and at 39 treatment levels. Multivariable analysis showed that subsidence was more likely to occur in patients with more than two treatment levels, and more likely to occur at treatment levels C5-7 than at levels C2-5. Subsidence was not associated with postoperative alignment change but associated with more disc height change (relatively oversized cage).

CONCLUSION

Subsidence is associated with a greater number of treatment levels, treatment at C5-7 and relatively oversized cage use.