Anterior cervical fusion with interbody cage containing beta-tricalcium phosphate augmented with plate fixation: a prospective randomized study with 2-year follow-up

Novel Calcium Phosphate Promotes Interbody Bony Fusion in a Porcine Anterior Cervical Discectomy and Fusion Model

STUDY DESIGN

Experimental porcine anterior cervical discectomy and fusion (ACDF) model: a proof-of-concept study.

OBJECTIVE

The effect of monetite synthetic bone graft (SBG) containing calcium pyrophosphate and β-tricalcium phosphate on cervical spinal fusion in a noninstrumented two-level large animal model.

SUMMARY OF BACKGROUND DATA

ACDF is the gold standard surgical technique for the treatment of degenerative cervical spinal diseases. However, pseudarthrosis associated with increased patient morbidity occurs in ∼2.6% of the surgeries. SBG may enhance bony fusion and subsequently decrease the risk of pseudarthrosis. Recent studies on monetite-based SBGs for use in large cranial defects in humans have shown promising bone healing results, necessitating further investigation of their use in cervical spinal fusion.

MATERIALS AND METHODS

Four adult female Danish Göttingen minipigs received partial cervical anterior discectomy and intervertebral defects at an upper and lower level. One defect was filled with SBG, and the other was left empty. Bony fusion was evaluated using computed tomography (CT) at three-month intervals for 12 months. Fifteen months postsurgery, the animals were euthanized for further ex vivo qualitative histopathologic and micro-CT evaluations. Fusion rates were compared using the Fisher exact test at each time point.

RESULTS

Increased interbody bony fusion rates were observed at SBG levels (4/4) compared with control levels (0/4) evaluated by CT at 6 and 9 months postsurgery ( P =0.029). Fusion was observed at all SBG levels 12 months postsurgery and at only one control level. Histopathologic evaluation confirmed high-quality interbody bony fusion at all SBG levels and fusion by spondylosis at one control level.

CONCLUSION

This proof-of-concept study provides preliminary evidence of a novel, calcium pyrophosphate-containing, and β-tricalcium phosphate-containing monetite SBG that promotes bony fusion compared with a negative control in a clinically relevant porcine model of ACDF.

Comparison of Interbody Fusion Strategies in Anterior Cervical Discectomy and Fusion: A Network Meta-Analysis and Systematic Review

OBJECTIVE

The optimal choice for fusion strategy in Anterior Cervical Discectomy and Fusion (ACDF) remains an unresolved issue. This study aims to perform a network meta-analysis and systematic review of fusion rate and complication rate of various fusion strategies used in ACDF.

METHODS

This study followed Prisma guidelines, and we searched PubMed, Embase, Cochrane Library, and Web of Science from inception to November 11, 2022, for Randomized Controlled trials comparing the efficacy and safety of fusion modalities in ACDF. The primary outcome was the fusion rate and complication rate. The PROSPERO number is CRD42022374440.

RESULTS

This meta-analysis identified 26 Randomized Controlled trial studies with 1789 patients across 15 fusion methods. The cage with autograft + plating showed the highest fusion rate, surpassing other methods like iliac crest bone graft (ICBG) and artificial bone graft (AFG). The stand-alone cage with autograft (SATG) had the second highest fusion rate. Regarding complication rate, the cage with AFG (CAFG) had the highest rate, more than other methods. The ICBG had a higher complication rate compared to ICBG + P, AFG, stand-alone cage with artificial bone graft, SATG, and CALG. The SATG performed well in both fusion and complication rate.

CONCLUSIONS

In this study, we conducted the first network meta-analysis to compare the efficacy and safety of various fusion methods in ACDF. Our findings suggest that SATG, with superior performance in fusion rate and complication rate, may be the optimal choice for ACDF. However, the results should be interpreted cautiously until additional research provides further evidence.

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.

Comparison of Different Osteobiologics in Terms of Imaging Modalities and Time Frames for Fusion Assessment in Anterior Cervical Discectomy and Fusion: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

The study's primary objective was to determine how osteobiologic choice affects fusion rates in patients undergoing anterior cervical discectomy and fusion (ACDF). The study's secondary objectives were to 1) determine the optimal timing of fusion assessment following ACDF and 2) determine if osteobiologic type affects the timing and optimal modality of fusion assessment.

METHODS

A systematic search of PubMed/MEDLINE was conducted for literature published from 2000 through October 2020 comparing anterior fusion in the cervical spine with various osteobiologics. Both comparative studies and case series of ≥10 patients were included.

RESULTS

A total of 74 studies met the inclusion criteria. Seventeen studies evaluated the efficacy of autograft on fusion outcomes, and 23 studies assessed the efficacy of allograft on fusion outcomes. 3 studies evaluated the efficacy of demineralized bone matrix, and seven assessed the efficacy of rhBMP-2 on fusion outcomes. Other limited studies evaluated the efficacy of ceramics and bioactive glasses on fusion outcomes, and 4 assessed the efficacy of stem cell products. Most studies utilized dynamic radiographs for the assessment of fusion. Overall, there was a general lack of supportive data to determine the optimal timing of fusion assessment meaningfully or if osteobiologic type influenced fusion timing.

CONCLUSIONS

Achieving fusion following ACDF appears to remain an intricate interplay between host biology and various surgical factors, including the selection of osteobiologics. While alternative osteobiologics to autograft exist and may produce acceptable fusion rates, limitations in study methodology prevent any definitive conclusions from existing literature.

Do Osteobiologics Augment Fusion in Anterior Cervical Discectomy and Fusion Surgery Performed With Mechanical Interbody Devices (Polyether ether ketone, Carbon Fiber, Metal Cages) and is the Fusion Rate Comparable to that With Autograft? A Systematic Review

STUDY DESIGN

Systematic Review of the Literature.

OBJECTIVE

The purpose of this study was to perform a systematic review describing fusion rates for anterior cervical discectomy and fusion (ACDF) using autograft vs various interbody devices augmented with different osteobiologic materials.

METHODS

A systematic review limited to the English language was performed in Medline, Embase and Cochrane library using Medical Subject Heading (MeSH) terms. Studies that evaluated fusion after ACDF using autografts and osteobiologics combined with PEEK, carbon fibre, or metal cages were searched for. Articles in full text that met the criteria were included in the review. The main outcomes evaluated were the time taken to merge, the definition of the fusion assessment, and the modality of the fusion assessment. The risk of bias of each article was assessed by the MINORS score or ROB 2.0 depending on the randomisation process.

RESULTS

The total number of references reviewed was six hundred and eighty-two. After applying the inclusion criteria, 54 were selected for the retrieval of the full text. Eight studies were selected and included for final analysis in this study. Fusion rates were reported between 83.3% and 100% for autograft groups compared to 46.5% and 100% for various interbody device/osteobiological combinations. The overall quality of the evidence in all radiographic fusion studies was considered insufficient due to a serious risk of bias.

CONCLUSION

Mechanical interbody devices augmented with osteobiologics performed similarly to autografts in terms of reliability and efficacy. Their time to fusion and fusion rate were comparable to autografts at the end of the final follow-up.

The Role of Osteobiologics in Augmenting Spine Fusion in Unplated Anterior Cervical Discectomy and Fusion Compared to Plated Constructs: A Systematic Review and Meta-analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

To compare clinical and radiographic outcomes as well as complications of unplated vs plated anterior cervical discectomy and fusion (ACDF) surgery considering the role of osteobiologics in single- and multi-level procedures.

METHODS

A systematic search of PubMed/MEDLINE, Scopus, CINAHL, EMBASE, CENTRAL, Cochrane and ClinicalTrials.gov databases was performed. Briefly, we sought to identify studies comparing unplated vs. plated ACDF for cervical degenerative disc disease reporting the use of osteobiologics in terms of clinical outcomes, radiographic fusion, and complications. Data on study population, follow-up time, type of cage and plate used, type of osteobiologic employed, number of levels treated, patient-reported outcomes (PROs), radiographic outcomes and complications were collected and compared. Relevant information was pooled for meta-analyses.

RESULTS

Thirty-eight studies met the inclusion criteria. No significant difference was found in terms of clinical outcomes between groups. Unplated ACDF was characterized by reduced blood loss, operation time and length of hospital stay. Fusion was achieved by the majority of patients in both groups, with no evidence of any specific contribution depending on the osteobiologics used. Dysphagia was more commonly associated with anterior plating, while cage subsidence prevailed in the unplated group.

CONCLUSION

Unplated and plated ACDF seem to provide similar outcomes irrespective of the osteobiologic used, with minor differences with doubtful clinical significance. However, the heterogeneity and high risk of bias affecting included studies markedly prevent significant conclusions.

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.

Subsidence following cervical discectomy and implant-to-bone ratio

Background

Implant subsidence is an undesirable effect after anterior cervical discectomy and fusion (ACDF). We investigated the relation between the rate of implant subsidence and the ratio of the implant surface area to the surface area of the adjacent bone.

Methods

We operated 170 disc spaces in a group of 104 patients. Two types of implants were used: 1) PEEK (polyetheretherketone) cages and 2) titanium-coated (TC) PEEK cages. Patients were randomised to receive a specific implant using a randomisation table. All implants had a surface area of 1.61 cm². Based on computed tomography images, bone surface areas were calculated for vertebral bodies immediately adjacent to the interbody implants. The implant-to-bone surface ratio was then calculated for each disc space. Implant subsidence was assessed over 12 months of follow-up, and associations between implant subsidence, the type of implant, and the implant-to-bone surface ratio were investigated.

Results

Twelve months after the surgery, computed tomography was performed on 86 patients (144 disc spaces). Furthermore, in 166 disc spaces and 102 patients, conventional radiographs were obtained.

Subsidence was observed in 21% of the examined intervertebral spaces, and it was more frequently associated with higher values of bone surface area and lower values of the implant-to-bone surface ratio. The type of implant (PEEK vs TC-PEEK cages) did not significantly influence the rate of implant subsidence.

Conclusions

Implant subsidence was significantly related to the value of a coefficient representing the ratio of the implant's surface area to the bone surface area of the adjacent vertebral bodies, with subsidence occurring significantly more rarely for coefficient values ≥ 0.37.

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.

Does Graft Position Affect Subsidence After Anterior Cervical Discectomy and Fusion?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Implant subsidence is an important prognostic factor after anterior cervical discectomy and fusion (ACDF). Our purpose in this study was to investigate whether graft position affects subsidence after ACDF and to determine if there is a difference in clinical results based on allograft subsidence and position.

METHODS

We reviewed 92 patients who underwent single-level ACDF with allograft and plate between January 2012 and October 2018. Treatment levels were divided based on allograft position within 2 mm of the posterior margin of the augmented plate (Anterior group) or at greater than 2 mm (Center group). Subsidence was defined as segmental vertebral body height decrease of 2 mm or more at 1 year compared to 1 week after surgery.

RESULTS

Overall subsidence prevalence was 15 (16%) cases. Subsidence was 11% in the Anterior group (8/73) and 39% in the Center group (7/19; P = .012). The subsidence group showed smaller graft footprint size (graft/endplate ratio) compared with the nonsubsidence group, and pseudarthrosis occurred frequently in the subsidence. There was no significant difference in clinical results according to graft position. These findings indicate that anterior graft position reduces risk of subsidence (95% confidence interval = 0.085-0.949).

CONCLUSION

To minimize risk of subsidence, the graft should be positioned on the anterior position of the surgical-level endplate. In addition, using a graft appropriate for endplate size will further reduce subsidence.

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

Context:

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

Aims:

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

Methods and Design:

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

Results:

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

Conclusions:

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

Degenerative Cervical Disorder-Stand-alone Cage Versus Cage and Cervical Plate: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

The objective of this study was to compare clinical and radiological outcomes following discectomy and anterior cervical fusion for the treatment of cervical degenerative disorder performed with stand-alone cages and anterior cervical plates.

METHODS

Electronic searches were performed in the MEDLINE, LILACS, and Cochrane Systematic Reviews databases, according to PRISMA guidelines, with no language or date restriction. The review was registered in PROSPERO under number CRD42018109180.

RESULTS

Six randomized clinical trials were selected, which evaluated at least one of the objectives of this work, such as pain control, bone consolidation, neurological symptoms, and cervical lordosis, thus satisfying the inclusion criteria. Articles that did not directly compare the 2 surgical techniques were excluded. A total of 309 patients were included and the results showed no significant difference in clinical (visual analogue scale and neck disability index) or radiological (cervical lordosis and fusion) outcome between the 2 groups. The operative time was shorter in the group with stand-alone cages (mean difference = -18.40; 95% CI = [-24.89, -11.92]; P < .66).

CONCLUSION

The stand-alone cages and anterior cervical plate techniques have similar clinical and radiological outcomes. Despite the significantly shorter operative time for one group, other randomized clinical trials are needed to establish conclusive evidence in favor of one of the comparative treatments.

β-tricalcium phosphate for bone substitution: Synthesis and properties

β-tricalcium phosphate (β-TCP) is one the most used and potent synthetic bone graft substitute. It is not only osteoconductive, but also osteoinductive. These properties, combined with its cell-mediated resorption, allow full bone defects regeneration. Its clinical outcome is sometimes considered to be "unpredictable", possibly due to a poor understanding of β-TCP physico-chemical properties: β-TCP crystallographic structure is not fully uncovered; recent results suggest that sintered β-TCP is coated with a Ca-rich alkaline phase; β-TCP apatite-forming ability and osteoinductivity may be enhanced by a hydrothermal treatment; β-TCP grain size and porosity are strongly modified by the presence of minute amounts of β-calcium pyrophosphate or hydroxyapatite impurities. The aim of the present article is to provide a critical, but still rather comprehensive review of the current state of knowledge on β-TCP, with a strong focus on its synthesis and physico-chemical properties, and their link to the in vivo response. STATEMENT OF SIGNIFICANCE: The present review documents the richness, breadth, and interest of the research devoted to β-tricalcium phosphate (β-TCP). β-TCP is synthetic, osteoconductive, osteoinductive, and its resorption is cell-mediated, thus making it one of the most potent bone graft substitutes. This comprehensive review reveals that there are a number of aspects, such as surface chemistry, crystallography, or stoichiometry deviations, that are still poorly understood. As such, β-TCP is still an exciting scientific playground despite a 50 year long history and > 200 yearly publications.

Could self-locking stand-alone cage reduce adjacent-level ossification development after aneterior cervical discectomy and fusion?

Numerous studies have shown that cervical arthrodesis is associated with the adjacent-segment pathology (ASP), such as adjacent-level ossification development (ALOD). However, it still remains largely unclear whether the self-locking stand-alone implant system can reduce the incidence of ALOD. In the present study, we prospectively recruited 120 patients with cervical degenerative disc disease (CDDD) who were treated by anterior cervical discectomy and fusion (ACDF). These patients were randomly and evenly divided into the ROI-C group and plate group. Clinical and radiologic follow-up was performed at 3, 6, 12, 24 and 36 months after surgery. Clinical evaluation included preoperative and postoperative assessments of Japanese Orthopaedic Association (JOA) score and Neck Disability Index (NDI) score. The presence and severity of ALOD, as well as the C2-7 Cobb angle, were assessed on the lateral cervical films during follow-up. There were no significant differences in JOA and NDI scores at each time point during the follow-up period between the two groups. ALOD occurred in 8.8% of 58 patients and 6.7% of 104 levels in the cage group. Moreover, ALOD occurred in 20.1% of 57 patients and 17.8% of 101 levels in the plate group. The ALOD was more serious in the plate group compared with the cage group. The C2-7 Cobb angle was significantly improved compared with that before the operation and could be maintained during the follow-up in both groups. The self-locking stand-alone cage was efficacious for ACDF, and it could reduce the incidence of ALOD compared with anterior plate and cage.

Strategies to Achieve Spinal Fusion in Multilevel Anterior Cervical Spine Surgery: An Overview

BACKGROUND

Anterior cervical fusion offers surgeons a safe and reliable surgical option for single-level and multilevel pathology; however, multilevel fusions pose a higher risk of complications than single-level fusions, including possible pseudoarthrosis, adjacent segment disease, sagittal imbalance, and construct subsidence. Various techniques can be used to mitigate risk in multilevel anterior cervical fusion.

QUESTIONS/PURPOSES

We reviewed the literature to determine the best surgical strategies in multilevel anterior cervical fusion.

METHODS

We searched the PubMed database for articles published from January 1980 through July 2019. Two authors identified relevant articles and then manually screened them for others to include in this review.

RESULTS

We initially identified 1936 articles and included 48 in our review. We found that clinical outcomes of multilevel anterior cervical fusion can be optimized through the use of biologics and graft selection, the evaluation of pre-existing deformity, the assessment of comorbidities, and the selection of fusion levels. Meticulous surgical technique in conjunction with modern surgical tools, such as instrumentation and biologics, allow surgeons to address complex cervical problems while limiting morbidity and enhancing clinical outcomes.

CONCLUSIONS

Multilevel anterior cervical fusions offer a relatively safe and reliable treatment option for both single-level and multilevel pathology.

Factors Influencing Interbody Cage Subsidence Following Anterior Cervical Discectomy and Fusion

STUDY DESIGN

This is a prospective study.

OBJECTIVE

The purpose of this study was to analyze the factors influencing subsidence following anterior cervical discectomy and fusion (ACDF) using a stand-alone cage.

SUMMARY OF BACKGROUND DATA

The relationship between cage subsidence and cage height and material has been reported in previous studies.

METHODS

Clinical and radiologic data from 78 patients, 105 levels, undergoing single-level and 2-level ACDF without plates from 2007 to 2015 were collected prospectively. Patients were followed for at least 12 months after surgery. Radiographs were obtained preoperatively, at 1 week, and at 1, 3, 6, and 12 months postoperatively to determine the presence of fusion and cage subsidence.

RESULTS

There was a correlation in cage height and subsidence (Spearman P<0.05). Cage subsidence was significantly shorter in the polyetheretherketone cages than in titanium cages (P<0.05). However, when cage height was <5 mm, the difference between the 2 groups was not significant. Large subsidence (>3 mm) was observed in 17 patients, 20 levels, many of whom exhibited sinking in the first month after surgery.

CONCLUSIONS

The greater the cage height, the greater the risk of cage subsidence in ACDF. Polyetheretherketone cages are superior to titanium cages for the maintenance of intervertebral height in cases where cage height is >5.5 mm.

LEVEL OF EVIDENCE

Level 3.

What is the most accurate radiographic criterion to determine anterior cervical fusion?

BACKGROUND CONTEXT

The accuracy of radiographic criteria for determining anterior cervical fusion remains controversial, and inconsistency in the literature makes a comparison of published clinical results problematic. The descriptions of bridging bone are still lacking and subjective, and the interpretation of images can be influenced by the type of graft or cage used.

PURPOSE

To assess and validate the diagnostic accuracies of four radiographic fusion criteria using the results of surgical exploration.

STUDY DESIGN

Retrospective, radiographic, and comparative study.

PATIENT SAMPLE

This study included patients who required anterior or posterior exploration of a previous anterior cervical arthrodesis level(s) ranging from C3-C4 to C7-T1 for suspected pseudarthrosis or adjacent-segment pathologies. They underwent radiologic examinations to determine the four fusion criteria. We included patients whose images were taken at least 1 year after the index surgery, and 82 patients with 151 cervical segments were enrolled.

OUTCOME MEASURES

The inter- and intra-rater reliabilities and validity that correlated with the results of surgical exploration for the four fusion criteria were assessed using data (fusion or not) that were collected by two raters.

METHODS

The four published radiographic fusion criteria were interspinous motion (ISM) < 1 mm and superjacent ISM ≥ 4 mm, seen on dynamic radiographs; conventional bridging bone, as seen on computed tomography (CT) scans; and extra-graft bridging bone (ExGBB) and intragraft bridging bone (InGBB), observed on multi-axial reconstructed CT scans. The criteria were evaluated by two raters (spine surgeons with 5 and 7 years of experience). The raters evaluated each criterion twice at two different time points, 3 to 4 weeks apart. First, ISM and conventional bridging bone on CT scans were evaluated, followed by ExGBB and InGBB, with a time interval of 4 months. This Research was supported by the Chung-Ang University Research Grants (less than 5,000 US dollars) in 2016.

RESULTS

The inter- and intra-rater reliability values of the ExGBB (0.887-0.933) criteria were the highest, followed by those for the ISM (0.860-0.906), bridging bone (0.755-0.907), and InGBB (0.656-0.695) criteria. The validity values that correlated with the exploration results were the highest for the ExGBB criteria (k=0.889), followed by the ISM (k=0.776), bridging bone (k=0.757), and InGBB (k=0.656) criteria and ExGBB showed the highest sensitivity (91.7%) and specificity (98.4%). Regarding the graft materials that were used, all criteria had the highest values in the auto-cortical group and lowest values in the cage group. Of note, sensitivity and specificity of ExGBB were 100% in autocortical group. In the cage group, the validity values for the ExGBB (k=0.663) and ISM (k=0.666) criteria were higher than those for the bridging bone (k=0.504) and InGBB (k=0.308) criteria CONCLUSION: The presence of ExGBB (anterior, posterior, or lateral to the graft or cage) correlated the best with surgical exploration. The ISM criteria demonstrated a similar accuracy to that of conventional bridging bone criteria on CT scans. In arthrodesed segments with auto-cortical bone, criteria showed the highest validity values. In cage group, ISM and ExGBB had acceptable accuracy, but the conventional bridging bone and InGBB were worse than guessing. We recommend that ISM and ExGBB criteria should be used to increase accuracy in patients who undergo arthrodesis with cages.

Evidence of Negative Effects of Defect Size and Older Patient Age by Quantitative CT-Based 3D Image Analysis in Ultraporous Beta-Tricalcium Phosphate Grafted Extremity Bone Defects at One Year

Introduction

Synthetic bone graft materials are commonly used to fill defects after curettage of benign bone lesions. Ultraporous beta tricalcium phosphate (TCP) is a popular synthetic compound used in this situation. Prior clinical studies based on plain X-ray analysis suggest incorporation of TCP is incomplete, even when combined with bone marrow (BMA).

Purpose

The purpose was to analyze volumetric CT-based changes in defects grafted with TCP with/without BMA in a completed prospective RCT to objectively determine (1) relationship between size and age versus TCP incorporation and (2) whether there is an advantage to addition of BMA.

Methods

Twenty-one patients with CT scans at ≥1 year follow-up available for digital analysis (TCP=10, TCP w/BMA =11) form the study population. CT image stacks were evaluated by creating volumetric masks using MIMICS imaging software for total defect, graft remaining, and graft incorporated volumes graft incorporation endpoints.

Results

Overall, there was significant (p=0.0029) negative correlation (r² = 0.38) between defect size and ratio of incorporated bone to defect size. This relationship remained strong (r² = 0.56) particularly for defects > 20 cc but not for smaller defects. Bone width was also a significantly related factor (r² = 0.94), with less graft incorporation in larger bone sites, in part likely due to the linear relationship between defect size and bone width. Relationship with age was complex and closely tied to defect volume. For larger defect volumes, younger patients were more successful at graft incorporation. Although age itself was not an independently significant factor, as defect volume increased, advanced age more negatively impacted new bone formation.

Conclusions

Larger size defect and affected bone and advancing age appear to be important negative factors in synthetic graft incorporation. Results showed no advantage to addition of BMA to TCP.

Evaluation of bony fusion after anterior cervical discectomy: a systematic literature review

PURPOSE

Anterior cervical discectomy and fusion (ACDF) has proven effective in treating radicular arm pain. Post-operatively, cervical spine stability is temporarily challenged, but data on bony fusion and speed of fusion are ambiguous; optimum evaluation method and criteria are debated.

AIM

To study bony fusion accomplishment and to obtain an overview of methods to evaluate fusion.

METHODS

A literature search was performed in PubMed and Embase. Included studies had to report original data concerning 1- or 2-level ACDF with intervertebral device or bone graft, where bony fusion was assessed using CT scans or X-rays.

RESULTS

A total of 146 articles comprising 10,208 patients were included. Bony fusion was generally defined as "the presence of trabecular bridging" and/or "the absence of motion". Fusion was accomplished in 90.1% of patients at the final follow-up. No gold standard for assessment could be derived from the results. Addition of plates and/or cages with screws resulted in slightly higher accomplishment of fusion, but differences were not clinically relevant. Eighteen studies correlated clinical outcome with bony fusion, and 3 found a significant correlation between accomplishment and better clinical outcome.

CONCLUSIONS

In approximately 90% of patients, bony fusion is accomplished one year after ACDF. As there is no generally accepted definition of bony fusion, different measuring techniques cannot be compared to a gold standard and it is impossible to determine the most accurate method. Variations in study design hamper conclusions on optimising the rate of bony fusion by choice of material and/or additives. Insufficient attention is paid to correlation between bony fusion and clinical outcome. These slides can be retrieved from electronic supplementary material.

Implantation of an empty polyetheretherketone cage in anterior cervical discectomy and fusion: a prospective randomised controlled study with 2 years follow-up

PURPOSE

To compare the clinical outcomes, radiographic results and fusion rate of ACDF between empty PEEK cages and PEEK cages packed with β-tricalcium phosphate.

METHODS

Forty-five patients were prospectively enrolled with cervical degenerative disc disease who requiring ACDF with a PEEK cage. 23 patients were randomised to the study group (empty cages) and 22 patients were in the control group (cages filled with β-tricalcium phosphate). Both patient groups were fixed with a cervical locking plate. A CT scan was performed 12 months postoperatively and 24 months if not confirmed fused at 12 months to evaluate the status of fusion. Clinical status was evaluated using the Japanese Orthopaedic Association (JOA) score, the Oswestry Disability Index (ODI) and the Visual Analogue Scale (VAS).

RESULTS

46 levels (97.88%) in the study group and 44 levels (97.77%) in the control group were confirmed as fused at 24 months. There was no significant difference between the fusion rates observed in the study and control groups (p = 0.82). There was no significant difference in JOA, ODI, or VAS scores at 24 months follow-up. The results showed that the members of the non-fusion group tended to be older than the individuals in the fusion group at 12 months, but was not significant in statistics.

CONCLUSIONS

Similar fusion rates and clinical outcomes were achieved when using ACDF with PEEK cages and instrumentation, regardless of whether the cage was filled with bone substitute at 24 months follow-up. Fusion rates improved over time and are comparable between both groups. These slides can be retrieved under Electronic Supplementary material.

Anterior Cervical Spondylosis Surgical Interventions are Associated with Improved Lordosis and Neurological Outcomes at Latest Follow up: A Meta-analysis

Aim of this study was to evaluate the effect of cervical spondylosis surgery on cervical lordosis and to identify factors affecting the change by latest follow-up. Literature search was carried out in electronic databases and study selection followed a priori eligibility criteria. Random effects meta-analyses were performed to estimate effect size/s of change in lordosis after surgery (at latest follow-up) and metaregression analyses were performed to identify factors affecting this change. Nineteen studies (1845 patients; age 55.18 [95% CI: 54.78, 55.57] years; 60.99 [60.63, 61.36] % males; follow-up 25.59 [25.20, 25.99] months) were included. Whereas, corpectomy (4.06 [2.65, 5.46] degree; p < 0.00001) and discectomy (4.59 [2.07, 7.11] degree; p < 0.00001) were associated with increase, laminectomy (-1.87 [-8.40, 4.66] degree; p = 0.57) and laminoplasty (0.25 [-1.07, 1.56] degree; p = 0.711) were not associated with significant change in lordosis at latest follow-up. Change in Japanese Orthopedic Association (JOA)/modified JOA (mJOA) score at latest follow-up was also significantly (p = 0.0005) higher in anterior than in posterior surgery group. Change in lordosis at latest follow-up had significant positive relationship with follow-up duration but had significant inverse associations with age, male gender, and preoperative JOA/mJOA score, independently. In posterior surgery subjects, after adjusting for age and gender, preoperative JOA/mJOA score was significantly inversely related to change in lordosis.

Degenerative Cervical Disc Disease: Long-term Changes in Sagittal Alignment and Their Clinical Implications After Cervical Interbody Fusion Cage Subsidence: A Prospective Study With Standalone Lordotic Tantalum Cages

STUDY DESIGN

A retrospective, observational study of prospectively collected outcomes.

OBJECTIVE

To investigate the long-term clinical course of anterior cervical discectomy and fusion with interbody fusion cages (ACDF-IFC) with lordotic tantalum implants and to correlate the radiologic findings with the clinical outcomes, with special emphasis on the significance and the influence of implant subsidence.

SUMMARY OF BACKGROUND DATA

Cage subsidence is the most frequently reported complication after ACDF-IFC. However, most reports fail to correlate cage subsidence with lower fusion rates or with unsatisfactory clinical results.

METHODS

Forty-one consecutive patients with symptomatic degenerative cervical disk disease with failure of conservative treatment were included. All patients underwent 1-/2-level ACDF-IFC with lordotic tantalum implants. The mean follow-up was 4.91 years.

RESULTS

The final follow-up fusion rate was 96.96% (32/33). The interspace height (IH) at the affected levels was significantly incremented after implant insertion, and despite a gradual loss in the height over time, the final follow-up IH was significantly higher than that measured preoperatively (P<0.0001). Anterior IH and posterior IH lost 55.8% and 76.2% of the initially incremented height, respectively, with a final increase of 72% in the AIH-PIH height differential. Implant subsidence (>3 mm) occurred in 11 disk spaces (26.82%). Preoperative and postoperative IH were significantly higher in subsidence patients; however, there was no difference in the final follow-up IH (P>0.05). Patients with ≥3 years of follow-up (n=29) did not demonstrate further significant subsidence beyond the second year. Regarding C1-C7 lordosis, the segmental Cobb angle, the cervical Visual Analogue Scale, and Neck Disability Index questionnaires, no difference between patients with or without final follow-up endplate subsidence was encountered.

CONCLUSIONS

Until fusion occurs, tantalum cage settlement into the vertebral body is to be expected. Further subsidence could be the result of segmental adaptative changes. Graft subsidence did not affect the clinical outcome in any of our patients during long-term follow-up. The occurrence of dynamical implant subsidence had a positive effect on cervical lordosis, especially at the posterior IH.

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 fusion with interbody cage containing beta-tricalcium phosphate: Clinical and radiological results

Aim

Beta tricalcium phosphate (beta-TCP) is an osteoconductive, resorbable material. Its clinical effectiveness has been proved in many indications. This study was clinical and radiographic study report obtained in patients undergoing anterior cervical discectomy and fusion ACDF in which PEEK cages were filled beta-TCP in an injectable form.

Material and methods

Between January 2010 and June 2011, 16 consecutive patients underwent ACDF using PEEK cages with beta-TCP. The cohort compromised 10 men and 6 women with a mean age of 45.2 years. The surgery was performed when the patient had myelopathy or radiculopathy with progressive neurological deficit, or failure of conservative treatment (a minimum of 3 months). The patients were evaluated by Odom criteria preoperatively and postoperative 3rd, 6th, 12th and 24th months. Preop and postop pain was evaluated with visual analogue scala (VAS). Disc height and fusion success rates were evaluated.

Results

Preoperative average VAS score was 7.9 (7–10) for neck pain and 8 (7–10) for arm pain. At the final follow-up, these scores became 1.5 and 1.4 for neck and arm pain, respectively. The average improvement rate was 81% for neck pain and 82.5% for arm pain. Postop ODOM's criteria main rate was 3.4. Bone fusion was achieved in 14 segments (70%) at 3rd month, 19 segments (95%) at 12th month follow-up assessment.

Conclusion

Clinical and radiological results revealed that B-TCP is a good alternative synthetic fusion material for cervical interbody fusion.

Level of evidence: Level IV, therapeutic study.

The Effect of Dynamic Versus Static Plating Systems on Fusion Rates and Complications in 1-Level and/or 2-Level Anterior Cervical Discectomy and Fusion: A Systematic Review

STUDY DESIGN

A systematic review.

OBJECTIVE

To determine the effect of plate design on fusion rates in patients undergoing a 1- and 2-level anterior cervical discectomy and fusion (ACDF).

METHODS

Articles published between January 1, 2002 and January 1, 2015 were systematically reviewed to determine the fusion rate of 1- and 2-level ACDFs using either a fully constrained or semiconstrained locking plate. Additional variables that were collected included the number of levels, the type of graft/cage used, the study design, the method for determining fusion, and complications.

RESULTS

Fifty-two articles and 3053 patients were included. No significant difference in the fusion rate for 1- and 2-level ACDF using a fully constrained plate (96.1%) and a semiconstrained plate (95.29%) was identified (P=0.84). No difference (P=0.85) in the total complication rate between fully constrained plates (3.20%) and semiconstrained plates (3.66%), or the rate of complications that required a revision (2.17% vs. 2.41%, P=0.82) was identified. However, semiconstrained plates had a nonsignificant increase in total dysphagia rates (odds ratio=1.660, P=0.28) and short-term dysphagia rates (odds ratio=2.349, P=0.10).

CONCLUSIONS

In patients undergoing a 1- or 2-level ACDF, there is no significant difference in the fusion or complication rate between fully constrained plates and semiconstrained plates.

LEVEL OF EVIDENCE

Level II-systematic review.

Titanium/Polyetheretherketone Cages for Cervical Arthrodesis with Degenerative and Traumatic Pathologies: Early Clinical Outcomes and Fusion Rates

OBJECTIVE

Anterior cervical discectomy and fusion is the most commonly employed surgical technique for treating cervical spondylosis. Although autologous bone grafts are considered the gold standard in achieving fusion, associated short- and long-term morbidities have led to a search for alternative materials. These have included carbon-fiber, titanium alloy (Ti) and ceramic and polyetheretherketone (PEEK) based implants. Recent attempts to optimize cage implants through using composite designs have combined Ti and PEEK. However, there are few published reports on the clinical and radiological outcomes of commercially available composite cages. Our study aimed to provide and evaluate initial outcomes of a composite Ti/PEEK cage.

METHODS

In this prospective single senior surgeon cohort study, 31 consecutive patients underwent a modified Smith-Robinson technique under general anesthesia and relevant data were collected. The study patients were aged between 18 and 75 years and underwent surgery from November 2013 to May 2014. Indications for surgery included traumatic and degenerative cervical disease that was unsuitable for or unresponsive to conservative management. All cages were between 5 and 8 mm and packed with super critical fluid sterilized allograft and bone marrow aspirate before insertion. Patients were followed-up for a minimum of 12 months. Fusion was assessed using fine cut CT and anteroposterior and lateral radiographs. Clinical outcomes were measured using a Visual Analogue Scale, Neck Oswestry Disability Index and Patient's Satisfaction Index.

RESULTS

Six of the original cohort were unavailable for adequate follow-up. The remaining 25 patients (17 men, 8 women; 33 operative levels) were observed for a mean of 14.6 months (range, 12-16 months). All operation levels were between C4 and C7 . Single-level operations were performed in 19 patients and additional plating in 14 patients. A fusion rate of 96% was achieved. Patients in both plated and non-plated groups experienced statistically significant improvements; good to excellent outcomes being seen in 92% of patients. There was one complication, namely recurrent laryngeal nerve palsy, which had partially resolved at 6 months follow-up.

CONCLUSION

The present study shows that enhancement of PEEK cages with Ti endplates is a safe and effective treatment with the potential for early osseointegration and early radiological evidence of fusion.

Zero-profile anchored cage reduces risk of postoperative dysphagia compared with cage with plate fixation after anterior cervical discectomy and fusion

PURPOSE

To compare the rate of postoperative dysphagia between zero-profile anchored cage fixation (ZPC group) and cage with plate fixation (CP group) after anterior cervical discectomy and fusion (ACDF).

METHODS

A meta-analysis of cohort studies between zero-profile anchored cage and conventional cage with plate fixation after ACDF for the treatment of cervical diseases from 2008 to May 2016. An extensive search of studies was performed in PubMed, Medline, Embase, Cochrane library and Google Scholar. Dysphagia rate was extracted. Data analysis was conducted with RevMan 5.2.

RESULTS

Sixteen trials involving 1066 patients were included in this meta-analysis. The results suggested that the ZPC group were associated with lower incidences of dysphagia than the CP group at postoperative immediately, 2 weeks, 2, 3, 6 and 12 months. In subgroup analysis, although significant differences were only found in the mild dysphagia at 3 and 6 months postoperatively and in the moderate dysphagia at 2 weeks after surgery; the ZPC group had a lower rate of postoperative dysphagia than the CCP group in short, medium and long term follow-up periods.

CONCLUSIONS

Zero-profile anchored cage had a lower risk of postoperative dysphagia than cage with plate.

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.

Bone substitutes and expanders in Spine Surgery: A review of their fusion efficacies

STUDY DESIGN

A narrative review of literature.

OBJECTIVE

This manuscript intends to provide a review of clinically relevant bone substitutes and bone expanders for spinal surgery in terms of efficacy and associated clinical outcomes, as reported in contemporary spine literature.

SUMMARY OF BACKGROUND DATA

Ever since the introduction of allograft as a substitute for autologous bone in spinal surgery, a sea of literature has surfaced, evaluating both established and newly emerging fusion alternatives. An understanding of the available fusion options and an organized evidence-based approach to their use in spine surgery is essential for achieving optimal results.

METHODS

A Medline search of English language literature published through March 2016 discussing bone graft substitutes and fusion extenders was performed. All clinical studies reporting radiological and/or patient outcomes following the use of bone substitutes were reviewed under the broad categories of Allografts, Demineralized Bone Matrices (DBM), Ceramics, Bone Morphogenic proteins (BMPs), Autologous growth factors (AGFs), Stem cell products and Synthetic Peptides. These were further grouped depending on their application in lumbar and cervical spine surgeries, deformity correction or other miscellaneous procedures viz. trauma, infection or tumors; wherever data was forthcoming. Studies in animal populations and experimental in vitro studies were excluded. Primary endpoints were radiological fusion rates and successful clinical outcomes.

RESULTS

A total of 181 clinical studies were found suitable to be included in the review. More than a third of the published articles (62 studies, 34.25%) focused on BMP. Ceramics (40 studies) and Allografts (39 studies) were the other two highly published groups of bone substitutes. Highest radiographic fusion rates were observed with BMPs, followed by allograft and DBM. There were no significant differences in the reported clinical outcomes across all classes of bone substitutes.

CONCLUSIONS

There is a clear publication bias in the literature, mostly favoring BMP. Based on the available data, BMP is however associated with the highest radiographic fusion rate. Allograft is also very well corroborated in the literature. The use of DBM as a bone expander to augment autograft is supported, especially in the lumbar spine. Ceramics are also utilized as bone graft extenders and results are generally supportive, although limited. The use of autologous growth factors is not substantiated at this time. Cell matrix or stem cell-based products and the synthetic peptides have inadequate data. More comparative studies are needed to evaluate the efficacy of bone graft substitutes overall.

A minimum 2-year comparative study of autologous cancellous bone grafting versus beta-tricalcium phosphate in anterior cervical discectomy and fusion using a rectangular titanium stand-alone cage

Although titanium stand-alone cages are commonly used in anterior cervical discectomy and fusion (ACDF), there are several concerns such as cage subsidence after surgery. The efficacy of β-tricalcium phosphate (β-TCP) granules as a packing material in 1- or 2-level ACDF using a rectangular titanium stand-alone cage is not fully understood. The purpose of this study is to investigate the validity of rectangular titanium stand-alone cages in 1- and 2-level ACDF with β-TCP. This retrospective study included 55 consecutive patients who underwent ACDF with autologous iliac cancellous bone grafting and 45 consecutive patients with β-TCP grafting. All patients completed at least 2-year postoperative follow-up. Univariate and multivariate analyses were performed to examine the associations between study variables and nonunion after surgery. Significant neurological recovery after surgery was obtained in both groups. Cage subsidence was noted in 14 of 72 cages (19.4 %) in the autograft group and 12 of 64 cages (18.8 %) in the β-TCP group. A total of 66 cages (91.7 %) in the autograft group showed osseous or partial union, and 58 cages (90.6 %) in the β-TCP group showed osseous or partial union by 2 years after surgery. There were no significant differences in cage subsidence and the bony fusion rate between the two groups. Multivariate analysis using a logistic regression model showed that fusion level at C6/7, 2-level fusion, and cage subsidence of grades 2-3 were significantly associated with nonunion at 2 years after surgery. Although an acceptable surgical outcome with negligible complication appears to justify the use of rectangular titanium stand-alone cages in 1- and 2-level ACDF with β-TCP, cage subsidence after surgery needs to be avoided to achieve acceptable bony fusion at the fused segments. Fusion level at C6/7 or 2-level fusion may be another risk factor of nonunion.

Subsidence as of 12 months after single-level anterior cervical inter-body fusion. Is it related to clinical outcomes?

BACKGROUND

Subsidence is a frequent phenomenon in the interbody fusion process in patients with anterior cervical discectomy and fusion (ACDF). There is little evidence of whether subsidence in the cervical spine has any impact on clinical outcomes.

OBJECTIVES

The purpose of this study is to investigate the correlation of subsidence and clinical outcomes after ACDF and to consider reasons subsidence might not cause unfavorable clinical outcomes.

METHODS

A total of 158 consecutive patients who underwent single-level ACDF were included. The patients were divided into a subsidence group (S-group) and a no subsidence group (N-group), with subsidence defined as a decrease by ≥3 mm in total intervertebral height (TIH). We analyzed outcomes resulting from subsidence, particularly focusing on clinical outcomes and subsequent global and segmental kyphosis using a repeated measure analysis of variance (RM-ANOVA).

RESULTS

Subsidence occurred in 74 patients (46.8%) as of a 12-month follow-up. The S-group included 58.6% with a stand-alone cage for interbody fusion (p = 0.002). Clinical outcomes improved significantly over time (neck pain, RM-ANOVA: F(1.3, 205) = 125.1, p < 0.001; arm pain, RM-ANOVA: F(1.3, 203) = 290.8, p < 0.001). There was no significant difference in interaction with subsidence and clinical outcomes between the S- and N-group (neck pain, RM-ANOVA: F(2,153) = 1.04, p = 0.356, partial η(2) = 0.229; arm pain, RM-ANOVA: F(2,153) = 0.56, p = 0.571, partial η(2) = 0.142). Segmental angle increased in both groups over time and showed a statistically significant difference between the S- and N-groups (RM-ANOVA: F(3,143) = 6.148, p = 0.001, partial η(2) = 0.959). Although, global cervical angle decreased generally and displayed no statically significant difference between the S- and N-group (RM-ANOVA: F(3,119) = 2.361, p = 0.075, partial η(2) = 0.056).

CONCLUSIONS

Radiographic subsidence after ACDF occurred in 46.8% patients as of 12 months after the single-level ACDF. The lack of correlation between bad clinical outcome and radiographic subsidence may be due to segmental kyphosis, preserved posterior height, and maintaining the global cervical angle.

A prospective randomized comparison of PEEK cage containing calcium sulphate or demineralized bone matrix with autograft in anterior cervical interbody fusion

PURPOSE

A variety of bone substitutes have been successfully used to fill PEEK cages in cervical interbody fusion in order to avoid the complications related to bone harvesting from the donor site. However, no controlled study has previously been conducted to compare the effectiveness of PEEK interbody cages containing calcium sulphate/ demineralized bone matrix (CS/DBM) with autogenous cancellous bone for the treatment of cervical spondylosis. The objective of this prospective, randomized clinical study was to evaluate the effectiveness of implanting PEEK cages containing CS/DBM for the treatment of cervical radiculopathy and/or myelopathy.

METHODS

Sixty-eight patients with cervical radiculopathy and/or myelopathy were randomly assigned to receive one- or two-level discectomy and fusion with PEEK interbody cages containing CS/DBM or autogenous iliac cancellous bone (AIB). The patients were followed up for two years postoperatively. The radiological and clinical outcomes were assessed during a two-year follow-up.

RESULTS

The mean blood loss was 75 ± 18.5 ml in the CS/DBM group and 100 ± 19.6 ml (P < 0.01) in the AIB group. The fusion rate was 94.3 % in the CS/DBM group and 100 % in the AIB group at 12-month follow-up. The fusion rate was 100 % at final follow-up in both groups. No significant difference (P > 0.05) was found regarding improvement of JOA score and segmental lordosis as well as neck and arm pain at all time intervals between the two groups. The total complication rate was significantly higher (P < 0.05) in the AIB group than in the CS/DBM group, but there was no significant difference between the two groups (P > 0.05) when comparing the complications in the neck.

CONCLUSIONS

In conclusion, the PEEK interbody fusion cage containing CS/DBM or AIB following one- or two-level discectomy had a similar outcome for cervical spondylotic radiculopathy and/or myelopathy. The rate of fusion and the recovery rate of JOA score between the two groups were the same. The filling of CS/DBM in the PEEK cage instead of AIB has the advantage of less operative blood loss and fewer complications at the donor site.

Impact of subsidence on clinical outcomes and radiographic fusion rates in anterior cervical discectomy and fusion: a systematic review

STUDY DESIGN

Systematic review.

OBJECTIVE

To provide a systematic review of published literature on the impact of subsidence on clinical outcomes and radiographic fusion rates after anterior cervical discectomy and fusion with plates or without plates.

BACKGROUND

Subsidence of interbody implants is common after anterior cervical spine fusions. The impact of subsidence on fusion rates and clinical outcomes is unknown.

METHODS

Systematic literature review on published articles on anterior cervical discectomy and fusion, which objectively measured graft subsidence, radiographic fusion rates, and clinical outcomes between April 1966 and December 2010.

RESULTS

A total of 35 articles that measured subsidence and provided fusion rates and/or clinical outcomes were selected for inclusion. The mean subsidence rate ranged from 19.3% to 42.5%. The rate of subsidence based on the type of implant ranged from 22.8% to 35.9%. The incidence of subsidence was not impacted by the type of implant (P=0.98). The overall fusion rate of the combined studies was 92.8% and was not impacted by subsidence irrespective of subsidence definition or the measurement technique used (P=0.19). Clinical outcomes were evaluated in 27 of 35 studies with all studies reporting an improvement in patient outcomes postoperatively.

CONCLUSIONS

Subsidence irrespective of the measurement technique or definition does not appear to have an impact on successful fusion and/or clinical outcomes. A validated definition and standard measurement technique for subsidence is needed to determine the actual incidence of subsidence and its impact on radiographic and clinical outcomes.

Comparative analysis of 3 different construct systems for single-level anterior cervical discectomy and fusion: stand-alone cage, iliac graft plus plate augmentation, and cage plus plating

STUDY DESIGN

A retrospective cohort-nested longitudinal study.

OBJECTIVE

To evaluate radiologic and clinically functional outcomes after single-level anterior cervical discectomy and fusion (ACDF) using 3 different fusion construct systems applying an accurate and reliable methodology.

SUMMARY OF BACKGROUND DATA

ACDF is an established procedure that uses 3 different fusion construct systems: cage alone (CA), iliac tricortical bone block with plate (IP), and cage with plate construct (CP). The outcome of a previous study is quite different and did not correlate with experimental studies.

METHODS

ACDF was performed on 158 patients (90 male and 68 female), who were followed up for >12 months. The patients were divided into the following 3 treatment groups: CA, IP, and CP. Factors related to outcome were also evaluated. Fusion rate, subsidence rate, and cervical angles were used to measure radiologic outcome. The Odom criteria and the visual analog scale were used to evaluate the clinical outcome.

RESULTS

The fusion rate was higher for patients in the IP (87.1%) and CP (79.5%) groups than for those in the CA group (63.2%) after 12 months of follow-up (P=0.019). The subsidence rate was lower for patients in the IP (28.1%) and CP (38.5%) groups than for those in the CA group (58.6%) (P=0.010). Subsidence occurred for the anterior height regardless of constructs. Radiating arm pain showed greater relief in the CP group than in the CA group (P=0.015). It improved more in the CP group than in the IP group, but the differences were not statistically significant (P=0.388). Other clinical outcomes did not show significant differences.

CONCLUSIONS

The trend of excellent radiologic outcome was observed for IP≥CP>CA. Plating may play a key role in the support of anterior height. As a result, plating prevents segmental kyphosis and subsidence and promotes bone fusion. Although the overall clinical outcomes were not different among the 3 groups, except for arm pain, more favorable trends regarding clinical outcome were observed for CP≥IP>CA.

Anterior cervical fusion assessment using reconstructed computed tomographic scans: surgical confirmation of 254 segments

STUDY DESIGN

Retrospective study developing diagnostic criteria.

OBJECTIVE

To validate 2 computed tomography-based findings, extragraft bone bridging (ExGBB) and intragraft bone bridging (InGBB), as diagnostic criteria for anterior cervical fusion using subsequent surgical confirmation and to demonstrate the different diagnostic accuracy on the basis of the graft material used.

SUMMARY OF BACKGROUND DATA

The accuracy and the methodology for evaluating bone bridging on computed tomographic scans to determine anterior cervical fusion status have not been validated or standardized.

METHODS

One hundred ten patients with 254 surgically explored segments along with reconstructed computed tomographic scans were included. Bone bridging at each cervical level was assessed for ExGBB and InGBB. ExGBB was defined as complete cortical bridging at any peripheral margins (anterior, posterior, left, or right) of the operated disc space, outside of the graft. InGBB was defined as cortical or trabecular bridging within the confines of the graft only. ExGBB and InGBB were serially evaluated on reformatted coronal and sagittal views by 3 independent raters. The reliabilities and validities correlated with surgical exploration were evaluated.

RESULTS

Surgical exploration revealed 123 fused and 131 pseudarthrosis segments. The reliability of 3 raters showed near perfect agreement for ExGBB and substantial agreement for InGBB. ExGBB also had higher validity for all raters than did InGBB. The autocortical graft group had the highest accuracy for both InGBB and ExGBB, with both values being nearly identical. The allograft group had the next highest validity values. For the cage group, InGBB had the lowest specificity (53.2%) and positive predictive value (35.5%), whereas ExGBB had 100% sensitivity and negative predictive value.

CONCLUSION

ExGBB seems to be a far more reliable and accurate to determine anterior cervical fusion. The diagnostic criteria using bone bridging should be different based on the intradiscal materials. With cages in particular, InGBB seems unreliable and ExGBB is necessary to determine anterior cervical fusion.

Tissue-engineered bone formation in vivo for artificial laminae of the vertebral arch using β-tricalcium phosphate bioceramics seeded with mesenchymal stem cells

STUDY DESIGN

A rabbit laminectomy model was used to evaluate the efficacy of artificial laminae of vertebral arch using bone marrow-derived mesenchymal stem cells (MSCs) transplanted in porous beta-calcium phosphates (β-TCP) bioceramics.

OBJECTIVE

The aim of this study was to establish artificial lamina of the vertebral arch for bone tissue engineering using β-TCP bioceramics seeded with MSCs in a rabbit model of decompressive laminectomy.

SUMMARY OF BACKGROUND DATA

Decompressive laminectomy may induce various degrees of scar tissue and adhesion formation in the epidural space, and thus is the most common cause of failed back surgery syndrome. However, there is no effective method of bone defect treatment to control and reduce the scar tissue formation.

METHODS

MSCs were harvested from New Zealand rabbits (2-week old) by femoral bone marrow extraction. These cells were seeded into porous β-TCP bioceramics and cultivated for up to 3 weeks in the presence of osteogenic supplements. Segmental defects (20 × 8 mm) were created in 48 adult New Zealand rabbits that underwent laminectomy at the L5 to L6 levels. The animals were transplanted with cell media (control), β-TCP bioceramics (group I), or MSC-loaded β-TCP bioceramics (group II). Bone formation was evaluated after operation using scanning electron microscopy, computed tomography, magnetic resonance imaging, histomorphometry, and immunohistochemistry.

RESULTS

Scanning electron microscopy showed that MSCs filled the pores and surfaces of bioceramics in MSC-loaded β-TCP. In addition, significant increases in bone formation were observed in group II compared with other groups. Computed tomography and magnetic resonance imaging at 16 weeks showed that the artificial lamina of the vertebral arch was successfully formed. Hematoxylin-eosin and Masson trichrome staining were used to show the artificial laminae of the vertebral arch and the degraded bioceramics. In addition, immunohistochemistry results showed that the expression of bone morphogenetic protein-2 increased significantly in group II compared with group I at 2,4, and 8 weeks after implantation (P < 0.05).

CONCLUSION

β-TCP bioceramics seeded with MSCs are a promising source of tissue-engineered bone for the artificial lamina of the vertebral arch.

Anterior cervical fusion for radicular-disc conflict performed by three different procedures: clinical and radiographic analysis at long-term follow-up

PURPOSE

Purpose of the study was to analyze in a retrospective way the clinical and radiographic outcome of three different surgical techniques in patients who underwent anterior cervical fusion.

METHODS

Eighty-six patients affected by symptomatic cervical disc herniation or spondylosis underwent cervical anterior fusion. Patients were divided in three groups considering the surgical technique. Clinical outcomes were evaluated by Visual Analog Scale, Odom's criteria, Neck Disability Index. Radiographic evaluation included standard and functional X-rays.

RESULTS

At 7 years mean follow-up, a comparable improvement in clinical symptoms was observed in all groups. Radiographic findings showed a solid fusion in all patients but seven cases in group 2 showed a subsidence of the cage.

CONCLUSIONS

As shown by the obtained clinical and radiographic results, the anterior interbody fusion with stand-alone peek cage containing β-tricalcium phosphate could be considered an effective and reliable procedure.

Effect of various kinds of cervical spinal surgery on clinical outcomes: a systematic review and meta-analysis

The choice of a specific surgical technique should be based on its benefits and harms. Previous reviews have shown that the benefit of surgery over conservative care is not clearly demonstrated in patients with disorders of the cervical spine. Also, no additional benefit of fusion upon anterior decompression techniques could be found. A clear overview of other surgical techniques is lacking. We therefore aimed to assess the benefits and harms of cervical spinal surgery in patients with cervical disorders. We searched MEDLINE, EMBASE, CINAHL, and CENTRAL up to June 2012. Randomized controlled trials (RCTs) were selected which included adults with cervical disorders receiving a surgical intervention and that reported at least 1 clinically relevant outcome measure (eg, pain, function, recovery). Two authors independently assessed the risk of bias using the criteria recommended by the Cochrane Back Review Group and extracted the data. The quality of the evidence was rated using the GRADE method. We included 39 RCTs comparing different surgical interventions. We found low-quality evidence for no difference in effectiveness between various surgical techniques used for anterior discectomy. There is a small, clinically irrelevant benefit on recovery and pain in favour of prosthetic disc surgery when compared with fusion techniques. Unfortunately, in these studies the authors had a clear conflict of interest. The differences in benefits and harms between the various surgical techniques are small. The surgeon, patient, and health care provider can therefore make the choice of any surgical technique based on experience, preferences, or costs.

Current status of bone graft options for anterior interbody fusion of the cervical and lumbar spine

Anterior cervical discectomy and fusion (ACDF) and anterior lumbar interbody fusion (ALIF) are common surgical procedures for degenerative disc disease of the cervical and lumbar spine. Over the years, many bone graft options have been developed and investigated aimed at complimenting or substituting autograft bone, the traditional fusion substrate. Here, we summarise the historical context, biological basis and current best evidence for these bone graft options in ACDF and ALIF.

Biphasic calcium phosphate contained within a polyetheretherketone cage with and without plating for anterior cervical discectomy and fusion

OBJECTIVE

To evaluate the properties of a combination bone graft consisting of biphasic calcium phosphate ceramic, polyetheretherketone (PEEK) cage in one- and two-level surgery.

METHODS

Over a 12-month time period, a prospective single surgeon series of 75 patients were included in the study and 58 patients selected based on adequate data points. From these 58 patients, 32 were supplemented with anterior plate fixation and 26 patients without plating. Duration of clinical follow-up was a mean of 12.4 months (range, 6-26 months) in the Plated Group and 10.5 months (range, 6-21 months) in the Non-Plated Group.

RESULTS

A 100% fusion rate with nil graft related complications was achieved in the Plated group compared with 96.2% fusion and 11.5% subsidence rates reported in the Non-Plated group. Patients in both groups experienced statistically significant improvement in pain and functional outcomes compared to their pre-operative status; however, there was no significant difference in outcome between the Plated and Non-Plated Groups.

CONCLUSIONS

Biphasic calcium phosphate ceramic contained within a PEEK cage is an effective implant for use in anterior cervical surgery with high fusion rates and good clinical outcome.

Cervical pedicle screw fixation combined with laminoplasty for cervical spondylotic myelopathy with instability

STUDY DESIGN

A retrospective study.

PURPOSE

To evaluate the surgical results of cervical pedicle screw (CPS) fixation combined with laminoplasty for treating cervical spondylotic myelopathy (CSM) with instability.

OVERVIEW OF LITERATURE

Cervical fixation and spinal cord decompression are required for CSM patients with instability. However, only a few studies have reported on CPS fixation combined with posterior decompression for unstable CSM patients.

METHODS

Thirteen patients that underwent CPS fixation combined with laminoplasty for CSM with instability were evaluated in this study. We assessed the clinical and radiological results of the surgical procedures. The Japanese Orthopedic Association (JOA) scoring system was used to evaluate the clinical results. The percentages of sli p, difference in sli p angle between maximum flexion and maximum extension of unstable intervertebrae, and perforation rate of CPS were evaluated.

RESULTS

The mean JOA scores before surgery, immediately after surgery, and at final follow-up were 9.1, 13.3, and 12.6, respectively. The mean percentages of sli p before surgery, immediately after surgery, and at final follow-up were 9.1%, 3.2%, and 3.5%, respectively; there were significant improvements immediately after surgery and at final follow-up. The difference in sli p angle between the maximum flexion and maximum extension of the unstable intervertebrae changed from 9.0° before surgery to 1.6° at the final follow-up. The perforation rate of CPS was 10.9%.

CONCLUSIONS

The results suggest that CPS fixation combined with laminoplasty is an effective surgical procedure for treating CSM with instability.

Clinical and radiographic outcomes of extreme lateral approach to interbody fusion with β-tricalcium phosphate and hydroxyapatite composite for lumbar degenerative conditions

Background

Historically, iliac crest bone graft has been used as the graft of choice for lumbar spine fusion procedures. Because fusion techniques have become less invasive, the demand for minimally disruptive grafting options has increased. This prospective study was performed to assess clinical and radiographic outcomes of patients treated with an iliac crest bone graft alternative and lateral lumbar interbody fusion.

Methods

Fifty degenerative lumbar patients were treated with the extreme lateral approach to interbody fusion and a β-tricalcium phosphate–hydroxyapatite graft with bone marrow aspirate (BMA) at 1 or 2 adjacent levels. BMA was collected from the iliac crest with a bone aspiration needle and applied to the FormaGraft (NuVasive, Inc., San Diego, California) in a 1:1 ratio. Radiolucent cages were filled with FormaGraft strips, granules, or blocks and implanted in a standard fashion. Clinical data were collected at baseline, 6 weeks, and 3, 6, and 12 months and included visual analog scale, Oswestry Disability Index, and Short Form 36 patient-reported assessments. Fusion assessments were made from neutral anteroposterior/lateral radiographs, lateral flexion/extension radiographs, and computed tomography images taken at least 12 months after surgery.

Results

Forty-four patients treated at 49 levels completed follow-up. The mean patient age was 54.7 ± 10.8 years, and mean body mass index was 30.8 ± 7.7 kg/m². Radiographic fusion was observed in 41 of 44 assessed levels (93.2%). Blood loss was less than 100 mL in 95.5% of patients. Of the patients, 93.2% spent 1 night or less in the hospital. By the 6-week follow-up, all clinical outcomes were significantly improved (P < .05). Improvements were maintained or increased throughout the course of follow-up.

Conclusions

This report shows that the technique of extreme lateral approach to interbody fusion in combination with FormaGraft and BMA in the interbody space is a safe and effective treatment option for interbody fusion of the lumbar spine when compared with other approaches and biologic options.

Cage subsidence does not, but cervical lordosis improvement does affect the long-term results of anterior cervical fusion with stand-alone cage for degenerative cervical disc disease: a retrospective study

OBJECTIVE

Clinical outcomes of the stand-alone cage have been encouraging when used in anterior cervical discectomy and fusion (ACDF), but concerns remain regarding its complications, especially cage subsidence. This retrospective study was undertaken to investigate the long-term radiological and clinical outcomes of the stand-alone titanium cage and to evaluate the incidence of cage subsidence in relation to the clinical outcome in the surgical treatment of degenerative cervical disc disease.

METHODS

A total of 57 consecutive patients (68 levels) who underwent ACDF using a titanium box cage for the treatment of cervical radiculopathy and/or myelopathy were reviewed for the radiological and clinical outcomes. They were followed for at least 5 years. Radiographs were obtained before and after surgery, 3 months postoperatively, and at the final follow-up to determine the presence of fusion and cage subsidence. The Cobb angle of C2-C7 and the vertebral bodies adjacent to the treated disc were measured to evaluate the cervical sagittal alignment and local lordosis. The disc height was measured as well. The clinical outcomes were evaluated using the Japanese Orthopaedic Association (JOA) score for cervical myelopathy, before and after surgery, and at the final follow-up. The recovery rate of JOA score was also calculated. The Visual Analogue Scale (VAS) score of neck and radicular pain were evaluated as well. The fusion rate was 95.6% (65/68) 3 months after surgery.

RESULTS

Successful bone fusion was achieved in all patients at the final follow-up. Cage subsidence occurred in 13 cages (19.1%) at 3-month follow-up; however, there was no relation between fusion and cage subsidence. Cervical and local lordosis improved after surgery, with the improvement preserved at the final follow-up. The preoperative disc height of both subsidence and non-subsidence patients was similar; however, postoperative posterior disc height (PDH) of subsidence group was significantly greater than of non-subsidence group. Significant improvement of the JOA score was noted immediately after surgery and at the final follow-up. There was no significant difference of the recovery rate of JOA score between subsidence and non-subsidence groups. The recovery rate of JOA score was significantly related to the improvement of the C2-C7 Cobb angle. The VAS score regarding neck and radicular pain was significantly improved after surgery and at the final follow-up. There was no significant difference of the neck and radicular pain between both subsidence and non-subsidence groups.

CONCLUSIONS

The results suggest that the clinical and radiological outcomes of the stand-alone titanium box cage for the surgical treatment of one- or two-level degenerative cervical disc disease are satisfactory. Cage subsidence does not exert significant impact upon the long-term clinical outcome although it is common for the stand-alone cages. The cervical lordosis may be more important for the long-term clinical outcome than cage subsidence.

Safety and effectiveness of bone allografts in anterior cervical discectomy and fusion surgery

STUDY DESIGN

Systematic review.

OBJECTIVE

The primary aim of this review was to evaluate clinical and radiographic outcomes in studies of anterior cervical discectomy and fusion (ACDF) using allograft versus ACDF with autograft, ACDF with cage devices, and cervical disc arthroplasty for the treatment of symptomatic cervical disc disease.

SUMMARY OF BACKGROUND DATA

ACDF remains the standard of care for patients with cervical radiculopathy who are unresponsive to conservative medical care. However, no known study has compared patient outcomes after ACDF with allograft, ACDF with autograft, ACDF with cage, and disc arthroplasty.

METHODS

After applying strict inclusion criteria, 21 comparisons from 20 studies formed the basis for this review. Patient outcomes included neck and arm pain, neck disability index (NDI), physical component summary (PCS), and mental component summary (MCS) scores from the SF-36, radiographic fusion rate, and select adverse events (e.g., wound infection, dysphagia, and adjacent segment degeneration).

RESULTS

The four treatment groups included ACDF with allograft (allograft, n = 1341), ACDF with autograft (autograft, n = 568), ACDF with cage (cage, n = 87), and cervical disc arthroplasty (arthroplasty, n = 603). Neck pain was reduced similarly by 63% to 69% in all groups. Comparable improvements were realized in arm pain after ACDF with allograft (75%) or arthroplasty (73%) that were greater than other treatment groups (62-68%). There was notable improvement in neck disability (61-65%) with allograft and arthroplasty after treatment. PCS scores improved with allograft (42%) and arthroplasty (44%). MCS scores improved modestly (16-21%) with allograft and arthroplasty. Fusion rates were 91% for allograft and autograft and 97% for cage. Adverse events were uncommon in all groups.

CONCLUSION

ACDF with allograft, ACDF with autograft, ACDF with cage, and cervical disc arthroplasty show similar improvements in pain, function, and quality of life with correspondingly low adverse event rates. All ACDF procedures result in high fusion rates.