Comparing Allografts to Autografts for Maintenance of Cervical Sagittal Parameters and Clinical Outcomes Following Anterior Cervical Discectomy and Fusion With Anterior Cervical Plating

Variation of Odontoid Incidence According to Age in Asymptomatic Children

OBJECTIVE

To investigate the effect of age and sex on odontoid parameters and their relationships with cervical sagittal alignment in children.

METHODS

A total of 155 Chinese children without cervical symptoms were divided into groups by age: 3-12 years (87 participants), 13-18 years (68 participants), and sex: male (91 participants) and female (64 participants). Lateral plain radiographs of the whole spine were analyzed for (1) odontoid parameters: odontoid incidence (OI), odontoid tilt, and C2 slope (C2S); and (2) cervical sagittal parameters: C0-2, C2-3, C2-4, C2-5, C2-6, and C2-7 angles (cervical lordosis [CL]), T1 slope (T1S), and T1S minus CL (T1S-CL). Student's t-tests, linear regression analyses, and Pearson's correlation coefficient analyses were performed.

RESULTS

OI showed a significant difference between the 3-12 and 13-18 year groups (13.35°±4.32° vs. 17.21°±4.26°, P<0.001), and significant differences were also observed in odontoid tilt (P=0.001) and C2S (P<0.001) between different sexes. Positive correlations were found between age and OI in the 3-12 and 13-18 year groups (adjusted R2=0.104 and 0.048, respectively). OI and C2S were positively correlated with the C0-2 angle in all age and sex groups.

CONCLUSIONS

Age emerged as a critical determinant of OI, which increased with age among pediatric populations. Clinicians should carefully consider the disparity in OI during the assessment and restoration of cervical sagittal balance in children.

Analysis of Complications in Multilevel Anterior Cervical Discectomy and Fusion Using Osteobiologics Other than Bone Morphogenetic Protein: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

The aim of this study is to analyze the complications related to multilevel anterior cervical discectomy and fusion (ACDF) using osteobiologics other than bone morphogenetic protein (BMP).

METHODS

A systematic review of the literature was conducted using PubMed, EMBASE, Cochrane Library, and ClinicalTrials.gov databases. The search to identify studies reporting complications in multilevel ACDF surgery using osteobiologics other than bone morphogenetic protein was performed in August 2020. The study was reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA).

RESULTS

A total of 584 articles were found after searching the databases and removing duplicates. Next, screening was performed in a double reviewer process, and 153 eligible articles-with 4 retrospective studies-in full-text were selected; these met all inclusion criteria. A total of 197 patients received 3-level ACDF, while 72 patients received 4-level ACDF. Osteobiologics were used in all selected articles, allograft was used in 4 studies, autologous bone graft was utilized in 3 articles, and hydroxyapatite was used in 1 article. The main complications reported were dysphagia, adjacent segment disease, and pseudarthrosis.

CONCLUSIONS

Given the limited evidence, no conclusions on complications in multilevel ACDF using osteobiologics other than BMP could be made. However, descriptively, the most common complications found were dysphagia, adjacent segment disease, and pseudoarthrosis. Further prospective studies separately analyzing complications in multilevel ACDF by osteobiologics and a number of treated levels are needed.

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

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Efficiency of minimal oblique resection of the uncinate process during an anterior cervical discectomy and fusion

ABSTRACT

Hypertrophy of the uncinate process (UP) can cause radiculopathy. Minimal UP resection is considered to remove the lesion while minimizing the risk of complications. This study aimed to elucidate the surgical results of minimal oblique resection of the UP. This study is a retrospective review of about sixty segments in 34 patients who underwent anterior cervical discectomy and fusion (ACDF) with minimal oblique uncinectomy between 2016 and 2018. The cross-sectional area of the UP was measured pre- and postoperatively. The interspinous distance, segmental Cobb angle, subsidence, fusion rate, surgical time, estimated blood loss, and postoperative complications were evaluated. The mean resected areas of the UP were 17.4 ± 8.7 mm2 (25.9%) on the right and 17.3 ± 11.2 mm2 (26.2%) on the left. The difference in interspinous distance in flexion-extension was 7.1 ± 3.2 and 1.6 ± 0.6 mm pre- and postoperatively, respectively (P = .000). The fusion rate after ACDF was 91.7% when measured according to segment (55/60) and 91.2% when measured according to patients (31/34). The difference in the segmental Cobb angle in flexion-extension was 8.3 ± 6.2° and 1.9 ± 0.3° pre and postoperatively, respectively (P = .000). Subsidence occurred in 4 (11.8%) patients and 5 (8.3%) segments. The average surgical time per segment was 68.8 ± 9.3 minute, and the estimated blood loss was 48.5 ± 25.0 mL. Postoperative complications comprised 1 case each of neck swelling, wound infection, pneumonia, and gastrointestinal bleeding. Our findings therefore revealed that minimal oblique uncinectomy during an ACDF can maintain the stability of the uncovertebral joint while sufficiently decompressing the neural foramen.

Residual Motion and Graft Type Do Not Influence Patient-reported Outcomes Following One- or Two-level Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Prospective cohort.

OBJECTIVE

The aim of this study was to determine the effect of graft type on residual motion and the relationship among residual motion, smoking, and patient-reported outcome (PRO) scores following anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

Although most patients develop solid fusion based on static imaging following ACDF, dynamic imaging has revealed that many patients continue to have residual motion at the arthrodesis.

METHODS

Forty-eight participants performed dynamic neck flexion/extension and axial rotation within a biplane radiography system 1 year following ACDF (21 one-level, 27 two-level). PRO scores included the Short Form-36, Neck Disability Index, and Cervical Spine Outcomes Questionnaire. An automated model-based tracking process matched subject-specific bone models to the biplane radiographs with sub-millimeter accuracy. Residual motion was measured across the entire arthrodesis site for both one- and two-level fusions in patients who received either allograft or autograft. Patients were divided into "pseudarthrosis" (>3° of flexion/extension residual motion) and "solid fusion" groups. Residual motion and PROs were compared between groups using Student t tests.

RESULTS

Patients who received allograft showed more total flexion/extension residual motion (4.1° vs. 2.8°, P = 0.12), although this failed to reach significance. No differences were noted in PROs based on graft type (all P > 0.08) or the presence of pseudarthrosis (all P > 0.13). No differences were noted in residual motion between smokers and nonsmokers (all P > 0.15); however, smokers who received allograft reported worse outcomes than nonsmokers who received allograft and smokers who received autograft.

CONCLUSION

Allograft may result in slightly more residual motion at the arthrodesis site 1 year after ACDF. However, there is minimal evidence that PROs are adversely affected by slightly increased residual motion, suggesting that the current definition of pseudarthrosis correlates poorly with clinically significant findings. Additionally, autograft appears to result in superior outcomes in patients who smoke.Level of Evidence: 2.

Sagittal balance of the cervical spine: a systematic review and meta-analysis

PURPOSE

The purpose of this systematic review and meta-analysis was to compare the cervical sagittal parameters between patients with cervical spine disorder and asymptomatic controls.

METHODS

Two independent authors systematically searched online databases including Pubmed, Scopus, Cochrane library, and Web of Science up to June 2020. Cervical sagittal balance parameters, such as T1 slope, cervical SVA (cSVA), and spine cranial angle (SCA), were compared between the cervical spine in healthy, symptomatic, and pre-operative participants. Where possible, we pooled data using random-effects meta-analysis, by CMA software. Heterogeneity and publication bias were assessed using the I-squared statistic and funnel plots, respectively.

RESULTS

A total of 102 studies, comprising 13,802 cases (52.7% female), were included in this meta-analysis. We used the Newcastle-Ottawa Scale (NOS) to evaluate the quality of studies included in this review. Funnel plot and Begg's test did not indicate obvious publication bias. The pooled analysis reveals that the mean (SD) values were: T1 slope (degree), 24.5 (0.98), 25.7 (0.99), 25.4 (0.34); cSVA (mm), 18.7 (1.76), 22.7 (0.66), 22.4 (0.68) for healthy population, symptomatic, and pre-operative assessment, respectively. The mean value of the SCA (degree) was 79.5 (3.55) and 75.6 (10.3) for healthy and symptomatic groups, respectively. Statistical differences were observed between the groups (all P values < 0.001).

CONCLUSION

The findings showed that the T1 slope and the cSVA were significantly lower among patients with cervical spine disorder compared to controls and higher for the SCA. Further well-conducted studies are needed to complement our findings.

Comparison of the effectiveness and safety of bioactive glass ceramic to allograft bone for anterior cervical discectomy and fusion with anterior plate fixation

Recently, a bioactive glass ceramic (BGC) has been developed for use as intervertebral cages for anterior cervical discectomy and fusion (ACDF). However, the effectiveness and safety of BGC cages remain to be evaluated. We completed a retrospective comparison of the radiological and clinical outcomes of 36 patients (52 levels) who underwent ACDF with a BGC cage and 35 patients (54 levels) using allograft bone. The following variables were compared between the two groups: the visual analog (VAS) neck and arm pain score and the neck disability index (NDI), measured before surgery and 1 year after; the change in Cobb's angle, between the C2 and C7 vertebrae, the global sagittal angle, and disc height compared from before surgery to 1 year after; and the rate of spinal fusion and cage subsidence at 1 and 2 years after surgery. The VAS and NDI scores were not different between the two groups. Similarly, the spinal fusion rate was not different between the BGC and allograft bone group at 1 year (73% and 87%, respectively; p = 0.07) and 2 years (94% and 91%, respectively; p = 0.54) after surgery. However, the rate of cage subsidence was higher in the allograft bone (43%) than the BGC (19%) group (p = 0.03), as was the rate of instrument-related failure (p = 0.028), with a specifically higher incidence of implant fracture or failure in the allograft bone group (p = 0.025). Overall, our findings indicate that BGC cages provide a feasible and safe alternative to allograft bone for ACDF.