Does zero-profile anchored cage accompanied by a higher postoperative subsidence compared with cage-plate construct? A meta-analysis

Biomechanical comparison of multiple zero-profile systems in anterior cervical discectomy and fusion: a finite element analysis

BACKGROUND

Anterior cervical discectomy and fusion (ACDF) with zero-profile (ZP) implant is commonly used for cervical degenerative diseases, but subsidence remains a concern, particularly in osteoporosis. The two-screw ZP (TSZP), four-screw ZP (FSZP), and ROI-C implants are frequently applied, yet the biomechanical performance across varying bone qualities remains unclear.

METHODS

A finite element (FE) model of the cervical spine (C3-C7) was constructed with TSZP, FSZP, and ROI-C implants at C4/C5 to simulate normal and osteoporotic conditions. A 73.6 N load and 1 Nm torque were applied at C3 to simulate flexion, extension, lateral bending, and axial rotation, followed by biomechanical analysis.

RESULTS

The FSZP implant exhibited the smallest ranges of motion, followed by ROI-C, with the largest in TSZP. ROI-C showed the lowest peak implant system stresses, while TSZP had the highest on the anchoring device and FSZP on the cage. The TSZP implant had the highest cortical endplate stresses, whereas FSZP had the lowest in normal and ROI-C in osteoporosis. No significant differences were observed in adjacent intervertebral disc pressures. All parameters increased in osteoporosis, except cortical endplate stresses.

CONCLUSION

The FSZP implant provided superior stability, while ROI-C exhibited a lower risk of implant-related complications. The TSZP implant was more prone to subsidence, which may be mitigated by optimizing stress distribution and enhancing damage prevention. Biomechanical performance was poorer under osteoporotic conditions, highlighting the need for careful surgical planning.

Are Variable Screw Angle Change and Screw-to-Vertebral Body Ratio Associated With Radiographic Subsidence Following Anterior Cervical Discectomy and Fusion?

Study DesignRetrospective Cohort.ObjectiveThis study aims to assess the easily measurable radiographic landmarks of screw-to-vertebral body ratio and changes in screw angle to identify if they are associated with early subsidence following an Anterior cervical discectomy and fusion (ACDF).MethodsA retrospective cohort study was conducted on patients undergoing 1-3 level ACDF with allograft or PEEK cages. Preoperative, immediate postoperative, and 6-month postoperative radiographs were analyzed to measure intradiscal height (or distance between 2 vertebral bodies) as an anterior vertebral distance (AVD), middle (MVD), and posterior (PVD), screw angle, screw-to-vertebral body length ratio, and interscrew distance. Multivariate stepwise regression analyses were performed.Results92 patients were included (42 single-level, 32 two-level, and 18 3-level ACDFs). In single-level ACDFs, a decrease in the caudal screw angle was associated with a decrease in AVD (=.001) and MVD (P = .03). A decrease in the PVD was associated with a decrease in segmental lordosis (P < .001). For two-level ACDFs, a higher caudal screw-to-body ratio was associated with a lower MVD (P = .01).ConclusionSix months following an ACDF for degenerative pathology, a decrease in the caudal screw angle was associated with an increase in radiographic subsidence at the antero-medial aspect of the disc space albeit largely subclinical. This suggests that the caudal screw angle change may serve as a reliable radiographic marker for early radiographic subsidence. Furthermore, a greater screw-to-vertebral body ratio may be protective against radiographic subsidence in two-level ACDF procedures.

Influence of Cervical Level Fused on Subsidence of Cage and Allograft in Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

This study aims to evaluate the relationship between the cervical levels fused and the degree of subsidence following anterior cervical discectomy and fusion (ACDF) procedures.

BACKGROUND

Subsidence following ACDF may worsen clinical outcomes. Previous studies have linked lower cervical levels with higher rates of subsidence, but none have quantified the relative degree of subsidence between levels.

MATERIALS AND METHODS

Patients who underwent ACDF from 2016 to 2021 at a tertiary medical center were included in this study. Lateral cervical radiographs from the immediate postoperative period and the final follow-ups were used to calculate subsidence. Analysis of variance was used to examine the association between cervical levels fused and subsidence. Multivariable linear regression analysis controlled for age, sex, smoking status, osteopenia/osteoporosis, number of fused levels, cage-to-body ratio, and cage type while examining the relationship between the cervical level fused and subsidence.

RESULTS

This study includes 122 patients who underwent 227 levels fused. There were 16 (7.0%) C3-C4 fusions, 55 (24.2%) C4-C5 fusions, 97 (42.7%) C5-C6 fusions, and 59 (26.0%) C6-C7 fusions. There was a significant difference in the degree of anterior subsidence between cervical levels fused ( P = 0.013) with a mean subsidence of 1.0 mm (SD: 1.6) for C3-C4, 1.1 mm (SD: 1.4) for C4-C5, 1.8 mm (SD: 1.5) for C5-C6, and 1.8 mm (SD: 1.6) for C6-C7 fusions. Relative to C6-C7 fusions, C4-C5 ( P = 0.016), and C3-C4 ( P = 0.014) fusions were associated with decreased anterior subsidence, whereas C5-C6 ( P = 0.756) fusions were found to have similar degrees of anterior subsidence in the multivariable analysis.

CONCLUSION

We found upper cervical levels experienced a smaller degree of anterior subsidence than lower levels, after controlling for demographic and implant characteristics. Surgeons can consider using larger cages at lower cervical levels to minimize these risks.

Does Bone Preservation at the Anterior Edge of the Vertebral Body Affect the Subsidence of Zero-Profile Cages After Anterior Cervical Discectomy and Fusion?

OBJECTIVE

The purpose of this study was to investigate whether the preservation of the anterior edge of the vertebral body affects the cage subsidence and clinical outcomes after anterior cervical discectomy and fusion (ACDF) using zero-profile cages.

METHODS

We retrospectively analyzed 86 patients who underwent 1-3 levels of ACDF using zero-profile cages between December 2017 and June 2023. According to whether the anterior edge was protected, the patients were divided into an intact group and a defect group. Cage subsidence was defined as a ≥2 mm decrease in vertebral height at follow-up compared with measurement on postoperative day 2. The patients' radiological parameters and clinical outcomes were also analyzed.

RESULTS

The subsidence rate was 17.02% (8/47) in the intact group and 41.03% (16/39) in the defect group (P = 0.014). At the last follow-up, all patients in both groups achieved complete intervertebral fusion. The cervical lordosis of the 2 groups was effectively restored after surgery, and the visual analog scale and Neck Disability Indexscores of the 2 groups were significantly improved. Multivariate logistic regression analysis showed that the protective factor for zero-profile cage subsidence was bone protection at the anterior edge of the vertebral body (odds ratio = 0.270; 95% confidence interval = 0.091-0.804), and the risk factor was related to the height of the preoperative surgical segment (odds ratio = 2.285; 95% confidence interval = 1.395-3.743).

CONCLUSIONS

For patients who undergo ACDF with zero-profile cages, especially those with a higher surgical segment, bone protection at the anterior edge of the vertebral body can effectively reduce the risk of zero-profile cage subsidence, but there is no difference in the final clinical effect.

Biomechanical analysis of a newly designed and 3D printed plate-locking interbody cage: an observational study of finite element analysis

Anterior cervical interbody fusion (ACDF) has become a classic surgical procedure for the treatment of cervical degenerative diseases, and various interbody cages are widely used in this procedure. We used 3D printing technology to produce a new type of plate-locking cage, anticipating to achieve high fusion rate with the high biomechanical stability. This study is to compare the biomechanical characteristics between a newly designed interbody cage and a conventional Zero-profile cage during ACDF using finite element analysis. The CT images of a 35-year-old healthy male were extracted and saved in DICOM format. Mimics Research 19.0, Geomagic Wrap 2017, NX12. 0, Abaqus 6.14 were used to construct the finite element models, then, titanium plate, titanium screw, cages, and the residual parts of both groups were assembled with reference to the surgical approach of ACDF (C4/5), following the successful establishment of both surgical models, a total of six boundary and loading conditions were tested, including flexion, extension, left and right bending, and left and right axial torsion. It is found that the plate stress peak of the new cage group decreased 73.78 MPa, 70.00%; 77.17 MPa, 70.67%; 59.77 MPa, 64.97%; 49.94 MPa, 58.28%; 44.55 MPa, 68.38%; 46.14 MPa, 68.00% in flexion, extension, left bending, right bending, left axial torsion and right axial torsion, respectively. There were no obvious increases of C5 upper endoplate stress peak between these two surgical models (< 50%), except 11.68 MPa, 153.08%; 6.55 MPa, 51.45%; in flexion and extension. The 3D-printed porous plate-locking cage was shown to be biomechanically stable compared to the conventional Zero-profile cage, and it is worth noticing that the stress on the plate of the new cage is less than that on screw of the conventional cage, which indicates that the risk of fracture, loosening, and prolapse of the new cage is less likely to occur.

Anterior Cervical Discectomy and Fusion with Zero-Profile Anchored Spacer Versus Plate and Cage for 3-Level Contiguous Cervical Degenerative Disease: A Systematic Review and Meta-Analysis

OBJECTIVE

To compare the safety, clinical outcomes, and radiological results of anterior cervical discectomy and fusion (ACDF) with zero-profile anchored spacer (ZPAS) versus plate and cage (PC) for 3-level contiguous cervical degenerative disease.

METHODS

The study was registered at PROSPERO (CRD42024512706). The Web of Science core collection, PubMed, and Embase were searched up to February 12, 2024. Review Manager 5.3 was used. The relative risk (RR) and 95% confidence interval were evaluated for dichotomous data. Continuous data were assessed using the mean difference and 95% confidence interval.

RESULTS

Nine studies comparing ACDF with ZPAS versus PC for 3-level contiguous cervical degenerative disease were included. The intraoperative blood loss and operation time in ZPAS were significantly less than those in PC. The subsidence rate, loss of cervical alignment, fusion segmental height, and intervertebral disc height were significantly greater in ZPAS than in PC. The cervical alignment and dysphagia rate within 6 months were significantly lower in ZPAS than in PC. The ASD of ZPAS was significantly lower than that of PC according to the sensitivity analysis when 1 study was excluded. No significant differences were identified in the other aspects.

CONCLUSIONS

Both ACDF with ZPAS and PC were safe and effective procedures. PC was associated with increased surgical trauma. The ZPAS could better decrease the incidence of ASD and dysphagia. ZPAS was also accompanied by high subsidence rate and poor cervical alignment.

A pragmatic single centre retrospective comparative review of complication profile between PEEK cages and Zero-P cage screw constructs

BACKGROUND

Anterior Decompression and Fusion (ACDF) is a common surgery recommended for symptomatic cervical degenerative disc disease after failed conservative care. There is no consensus on the choice of implants, and it varies between surgeons. This study aims to analyse the early complications following ACDF performed using a standalone cage versus a Zero-P (Cage Screw - (CS)) construct for patients with cervical degenerative disc disease.

METHODS

A total of 162 patients underwent an ACDF between August 2016 and July 2018. There were 83 patients (111 cervical disc levels) with standalone cage (SA) and 79 patients (111 cervical disc levels) with cage-screw (CS) fixation. There was no difference between the groups in terms of age, gender, and levels of surgery. The follow-up ranged from 2 months to 24 months. Complications, both clinical and radiological, were assessed between the groups.

RESULTS

Both the SA and Zero-P (CS) groups were subdivided into single and multilevel surgery. Complications encountered in the SA group were temporary swallowing problems 10, hoarseness of voice 3, cage migration 1, delayed union 1, Horner's syndrome 1, cage subsidence 2. In the CS group swallowing problems 4, hoarseness of voice 4, CSF leak 1, recurrent symptoms 1. The observed difference in the incidence of complications between the groups did not reach statistical significance. Univariate analysis between the groups did not show any difference in the improvement of cervical sagittal balance, fusion rate, subsidence, and complications encountered. Multivariate logistic regression analysis for complications showed no difference between the groups when assessed for smoking, gender, age, Charlson comorbidity index, levels of surgery, fusion status, Odom score, or the type of implant.

CONCLUSION

In this short-term study, the standalone (SA) cages showed no difference in their complication profile in comparison to a cage-screw construct for both single and multilevel ACDF. Standalone cages might be a cost-effective option without increased complication risks. Nevertheless, we propose a longer-term follow-up with a prospective randomized trial for further evaluation of this finding.

Analysis of risk factors for non-fusion of bone graft in anterior cervical discectomy and fusion: A clinical retrospective study

BACKGROUND

Bone graft fusion is a major concern among surgeons after Anterior Cervical Discectomy and Fusion (ACDF) surgery as non-fusion may lead to further physical and drug therapies.

METHODS

The related risk elements of non-fusion of bone graft in ACDF surgery were retrospectively assessed. Patients receiving ACDF operation in our hospital from January 2015 to December 2019 were retrospectively analyzed. According to the criteria, 107 study subjects were recruited with a total of 164 surgical segments. The general information of patients, bone graft materials, imaging parameters, and clinical efficacy was recorded. T-test, chi-square test and binary logistic regression evaluation were employed to explore the risk factors of bone graft nonunion.

RESULTS

Low housefield unit (HU) value, diabetes, allogeneic bone, and hydroxyapatite (HA) artificial bone could be risk factors for bone graft fusion in ACDF surgery. Further multivariate analysis was performed and confirmed those related factors of bone graft non-fusion including low HU value (non-fusion rate: 32.53% [27/83], OR = 5.024, p = 0.025), diabetes (non-fusion rate: 53.33% [8/15], OR = 4.776, p = 0.031), allogeneic bone (18.57% [13/70], OR = 3.964, p = 0.046), and artificial bone (68.29% [28/41], OR = 50.550, p < 0.01).

CONCLUSION

By looking at bone graft fusion, selecting autologous iliac bone is an ideal selection to avoid non-fusion of bone graft in ACDF. Diabetes was more important predictor of bone graft nonunion than low HU value. Larger sample size and longer follow-up are required to further confirm these findings in the future.

Cervical Vertebral Bone Quality Score Independently Predicts Zero-Profile Cage Subsidence After Single-Level Anterior Cervical Discectomy and Fusion

OBJECTIVE

This is the first study to evaluate the predictive value of the cervical vertebral bone quality (VBQ) score on zero-profile cage (ZPC)subsidence after anterior cervical discectomy and fusion (ACDF) using the Hounsfield units (HU) value of computed tomography as the reference.

METHODS

A total of 89 patients with at least 1 year of follow-up who underwent single-level ACDF with ZPC were retrospectively and consecutively included. VBQ and HU value were determined from preoperative T1-weighted magnetic resonance imaging and computed tomography. Subsidence was defined as ≥2 mm of migration of the cage into the superior or inferior endplate or both using lateral cervical spine radiography. The results were subjected to statistical analysis.

RESULTS

Subsidence was observed among 16 of the 89 study patients (Subsidence rate: 18.0%). The mean VBQ score was 2.94 ± 0.820 for patients with subsidence and 2.33 ± 0.814 for patients without subsidence. The multivariable analysis demonstrated that only an increased VBQ score (odds ratio: 1.823, 95% confidence interval : 0.918,3.620, P = 0.001) was associated with an increased rate of cage subsidence. There was a significant and moderate correlation between HU and VBQ (r = -0.507, P < 0.001). Using receiver operating characteristic curves, the area under the curve was 0.785, and the most appropriate threshold of VBQ was 2.68 (sensitivity 72.7%, specificity 82.1%).

CONCLUSIONS

The VBQ score may be a valuable tool for independently predicting ZPC subsidence after single-level ACDF.

Cervical vertebral Hounsfield units are a better predictor of Zero-P subsidence than the T-score of DXA in patients following single-level anterior cervical discectomy and fusion with zero-profile anchored spacer

OBJECTIVES

To determine the predictive effect of Hounsfield unit (HU) values in the cervical vertebral body measured by computed tomography (CT) and T-scores measured by dual-energy X-ray absorptiometry (DXA) on Zero-P subsidence after anterior cervical discectomy and fusion (ACDF)with Zero-P. In addition, we evaluated the most reliable measurement of cervical HU values.

METHODS

We reviewed 76 patients who underwent single-level Zero-P fusion for cervical spondylosis. HU values were measured on CT images according to previous studies. Univariate analysis was used to screen the influencing factors of Zero-P subsidence, and then, logistic regression was used to determine the independent risk factors. The area under the receiver operating characteristic curve (AUC) was used to evaluate the ability to predict Zero-P subsidence.

RESULTS

Twelve patients (15.8%) developed Zero-P subsidence. There were significant differences between subsidence group and non-subsidence group in terms of age, axial HU value, and HU value of midsagittal, midcoronal, and midaxial (MSCD), but there were no significant differences in lowest T-score and lowest BMD. The axial HU value (OR = 0.925) and HU value of MSCD (OR = 0.892) were independent risk factors for Zero-P subsidence, and the lowest T-score was not (OR = 1.186). The AUC of predicting Zero-P subsidence was 0.798 for axial HU value, 0.861 for HU value of MSCD, and 0.656 for T-score.

CONCLUSIONS

Lower cervical HU value indicates a higher risk of subsidence in patients following Zero-P fusion for single-level cervical spondylosis. HU values were better predictors of Zero-P subsidence than DXA T-scores. In addition, the measurement of HU value in the midsagittal, midcoronal, and midaxial planes of the cervical vertebral body provides an effective method for predicting Zero-P subsidence.

Outcomes Following 2-Level Cervical Interventions with Cage-and-Plate, Zero-Profile, or Arthroplasty Constructs

BACKGROUND

Though cage-and-plate constructs are widely used for disk height restoration in surgery for cervical disc disease, concerns over range of motion limitations and adjacent disc space violations have fueled the development of artificial disc and zero-profile constructs. This study investigated the outcomes of patients undergoing two-level cervical interventions via arthroplasty, cage-and-plate, or zero-profile constructs.

METHODS

Patients undergoing two-level anterior cervical procedures between 2010 and 2020 were identified using an all-payer claims database. Logistic regression models were utilized to develop criteria for a 1:1:1-exact match procedure. The primary outcome was the need for additional surgery within 30 months, and the secondary outcomes included medical and surgical complications observed within 30 days of index intervention. P values < 0.05 were considered statistically significant.

RESULTS

133,831 patients were identified as undergoing two-level anterior cervical interventions. Seven thousand three hundred seventy-one records were analyzed through a 1:1:1 match. Patients who received zero-profile versus cage-and-plate constructs had significantly decreased odds of requiring additional surgery within 30 months (Odds Ratio [OR] 0.64; 95% Confidence Interval [CI] 0.51-0.81). However, postoperative medical complications were increased among patients who received zero-profile constructs compared to cage-and-plate (OR 1.59; 95%CI 1.07-2.37). Patients who underwent arthroplasty also had decreased odds for additional surgery versus cage-and-plate (OR 0.75; 95%CI 0.60-0.93). There was no significant difference between arthroplasty and cage-and-plate constructs in developing postoperative surgical or medical complications.

CONCLUSIONS

Among patients undergoing two-level interventions, cage-and-plate constructs were associated with increased odds of additional surgery within 30 months following index procedures when compared to zero-profile constructs or arthroplasty.

Overloaded vertebral body: a unique radiographic phenomenon following multilevel anterior cervical discectomy and fusion

PURPOSE

Because previous studies have not focused on postoperative cervical collapse, the purpose of the present study was to introduce the overloaded vertebral body (OVB) phenomenon following multilevel zero-profile anterior cervical discectomy and fusion (ACDF) as well as to investigate its effects on radiographic outcomes.

METHODS

We conducted a retrospective study involving patients who underwent ACDF. A total of 55 patients were included in the analysis, including 110 OVB and 110 non-OVB. The evaluated vertebral parameters included the vertebral cross-sectional area (CSA), wedge angle (WA), vertebral height [anterior (AH) and posterior (PH)] and anterior-posterior vertebral diameter [upper (UD) and lower (LD)].

RESULTS

The CSA and WA were significantly lower in the OVB group than in the non-OVB group at 3, 6, and 12 months after surgery as well as at the final follow-up (p < 0.01). The AH of the OVB group was significantly lower at 3, 6, and 12 months after surgery as well as at the final follow-up compared to 1 week after surgery (p < 0.01).

CONCLUSIONS

OVB, a new phenomenon following multilevel ACDF, is defined as the cervical vertebral body located in the middle of the surgical segments in multilevel anterior cervical spine surgery. Statistical analysis of vertebral parameters, including CSA, WA, AH, PH, UD, and LD, showed that OVB occurs mainly at the anterior edge of the vertebra and that its largest radiographic manifestation is the loss of height at the anterior edge of the vertebra in the early postoperative period.

Comparing zero-profile and conventional cage and plate in anterior cervical discectomy and fusion using finite-element modeling

Conventional cage and plate (CCP) implants usually used in ACDF surgery, do have limitations such as the development of postoperative dysphagia, adjacent segment degeneration, and soft tissue injury. To reduce the risk of these complications, zero-profile stand-alone cage were developed. We used finite-element modeling to compare the total von Mises stress applied to the bone, disc, endplate, cage and screw when using CCP and ZPSC implants. A 3-dimensional FE (Finite element) analysis was performed to investigate the effects of the CCP implant and ZPSC on the C3 ~ T1 vertebrae. We confirmed that the maximum von Mises stress applied with ZPSC implants was more than 2 times greater in the endplate than that applied with CCP implants. The 3D analysis of the ZPSC model von Mises stress measurements of screw shows areas of higher stress in red. Although using ZPSC implants in ACDF reduces CCP implant-related sequalae such as dysphagia, we have shown that greater von Mises stress is applied to the endplate, and screw when using ZPSC implants. This may explain the higher subsidence rate associated with ZPSC implant use in ACDF. When selecting an implant in ACDF, surgeons should consider patient characteristics and the advantages and disadvantages of each implant type.

Zero-profile anchored spacer versus conventional plate-cage construct in bilevel anterior cervical discectomy and fusion: a systematic review and meta-analysis

BACKGROUND

Zero-profile anchored spacers (ZAS) and plate-cage constructs (PCC) are currently employed when performing anterior cervical discectomy and fusion (ACDF). Nevertheless, the efficacy and safety of both devices in bilevel ACDF remain controversial. The goal of our meta-analysis is to assess the overall long-term efficacy and security among ZAS and PCC in bilevel ACDF.

METHODS

A search of four electronic databases was conducted to identify researches that compared ZAS with PCC for bilevel ACDF. Stata MP 17.0 software was used for this meta-analysis.

RESULTS

Nine researches with a total of 580 patients were involved. In comparison to PCC, ZAS significantly reduced intraoperative bleeding and postoperative dysphagia rates. No significant differences were found concerning operation time, JOA score, NDI score, cervical Cobb angle, fusion rates, the incidence of adjacent segmental degeneration (ASD) and implant sinking rates at last follow-up.

CONCLUSION

Compared to PCC, ZAS achieved similar efficacy and security in bilevel ACDF with respect to operative time, JOA score, NDI score, cervical Cobb angle, fusion rates, implant sinking rates and ASD rates at final follow-up. It is worth noting that ZAS offered considerable benefits over conventional PCC for the reduction of intraoperative bleeding and postoperative dysphagia. Therefore, for patients requiring bilevel ACDF, ZAS seems superior to PCC. Given the limitations of our study, larger prospective randomised controlled trials are needed to establish reliable proof to consolidate our conclusions.

Outcomes of different zero-profile spacers in the treatment of two-level cervical degenerative disk disease

PURPOSE

The purpose of this study was to analyze the clinical and radiological outcomes of two different zero-profile spacers (ROI-C and anchor-C) in contiguous two-level ACDF for CDDD patients.

METHODS

We retrospectively analyzed patients who underwent contiguous two-level ACDF due to CDDD between January 2015 and December 2020 in our hospital. Patients who received ROI-C and anchor-C were included as the study groups, and those who underwent plate-cage construct (PCC) were included as the control group. The primary outcome measures were radiographical parameters, and the secondary outcome measures were dysphagia, JOA scores and VAS scores for these patients.

RESULTS

A total of 91 patients were enrolled in the study; there were 31, 21 and 39 patients in the ROI-C, anchor-C and PCC groups, respectively. The mean follow-up duration was 24.52 months (range, 18-48 months) in the ROI-C group, 24.38 months (range, 16-52 months) in the anchor-C group and 25.18 months (range, 15-54 months) in the PCC group. The loss of the intervertebral space height and cage subsidence rate in the ROI-C group were significantly higher than those in the anchor-C group and PCC group at the final follow-up (P < 0.05). The ROI-C group showed a lower incidence of adjacent segment degeneration than the anchor-C group and PCC group, but the difference was not significant. The fusion rates were not different among these three groups. The early dysphagia rate was significantly lower in the patients with zero-profile spacers than in the PCC group (P < 0.05), but the difference was not significant at the last follow-up. No relevant differences were found in the JOA scores and VAS scores.

CONCLUSIONS

Zero-profile spacers showed promising clinical outcomes in CDDD patients having contiguous two-level ACDF. However, ROI-C resulted in a higher intervertebral space height loss and a higher cage subsidence rate than anchor-C during the follow-up.

Self-locking stand-alone cage versus cage-plate fixation in monosegmental anterior cervical discectomy and fusion with a minimum 2-year follow-up: a systematic review and meta-analysis

BACKGROUND

Currently, self-locking stand-alone cages (SSC) are commonly applied in anterior cervical discectomy and fusion (ACDF), as are cage-plate constructs (CPC). However, it remains controversial concerning the long-term effectiveness of both apparatuses. Our purpose is to compare long-term effectiveness of SSC with CPC in monosegmental ACDF.

METHODS

Four electronic databases were queried to identify studies comparing SSC versus CPC in monosegmental ACDF. The meta-analysis was carried out with the use of the Stata MP 17.0 software package.

RESULTS

Ten trials with 979 patients were included. Compared to CPC, SSC significantly reduced operative time, intraoperative blood loss, duration of hospitalisation, cervical Cobb angle at final follow-up, 1-month postoperative dysphagia rate, and incidence of adjacent segment degeneration (ASD) at final follow-up. No significant difference was found regarding 1-month postoperative cervical Cobb angle, JOA scores, NDI scores, fusion rate and cage subsidence rate at final follow-up.

CONCLUSION

Both devices achieved similar long-term effectiveness in monosegmental ACDF regarding JOA scores, NDI scores, fusion rate and cage subsidence rate. SSC had significant advantages over CPC in reducing surgical duration, intraoperative bleeding, duration of hospitalisation, as well as rates of dysphagia and ASD after surgery. Therefore, SSC is a better option than CPC in monosegmental ACDF. However, SSC is inferior to CPC in maintaining cervical curvature at long-term follow-up. Whether radiological changes affect clinical symptoms needs confirmation in trials with longer follow-up.

Zero-profile implant versus conventional cage-plate construct in anterior cervical discectomy and fusion for the treatment of single-level degenerative cervical spondylosis: a systematic review and meta-analysis

BACKGROUND

The clinical outcomes of single-level anterior cervical discectomy and fusion (ACDF) with the Zero-profile (Zero-p) were evaluated in comparison with the anterior cervical cage-plate construct (CPC).

METHODS

We performed a systematic search covering PubMed, Embase, Cochrane Central Register of Controlled Trials, Web of Science, Medline, China National Knowledge Infrastructure (NCKI), Wan Fang Database, and Wei Pu Database. Articles focused on single-level ACDF or data of the single - level that can be extracted were included, and articles that did not directly compare Zero-p and CPC were excluded. Twenty-seven studies were included with a total of 1866 patients, 931 in the Zero-p group and 935 in the CPC group. All outcomes were analyzed using Review Manager 5.4.

RESULTS

The meta-analysis outcomes indicated that operative time (WMD = - 12.47, 95% CI (- 16.89, - 8.05), P < 0.00001), intraoperative blood loss (WMD = - 13.30, 95% CI (- 18.83, - 7.78), P < 0.00001), risk of adjacent segment degeneration (ASD) (OR 0.31, 95% CI (0.20, 0.48), P < 0.0001), risk of dysphagia of short-term (OR 0.40, 95% CI (0.30, 0.54), P < 0.0001), medium-term (OR 0.31, 95% CI (0.20, 0.49), P < 0.0001), and long-term (OR 0.29, 95% CI (0.17, 0.51), P < 0.0001) of Zero-p group were significantly lower. The JOA score of Zero-p group at the final follow-up was significantly higher (WMD = - 0.17, 95% CI (- 0.32, - 0.03), P = 0.02). There were no significant differences in length of stay (LOS), Neck Disability Index (NDI), Visual Analogue Score (VAS), fusion rate, segmental Cobb angle, cervical Cobb angle, prevertebral soft tissue thickness (PSTT), SF-36, subsidence, implant failure, and hoarseness between the two groups. This study was registered with PROSPERO, CRD42022347146.

CONCLUSION

Zero-p group reduced operative time, intraoperative blood loss, JOA score at follow-up and reduced the incidence of dysphagia and postoperative ASD, but the two devices had the same efficacy in restoring the cervical curvature, preventing the cage subsidence, and in postoperative VAS, NDI, LOS, PSTT, SF-36, fusion rate, implant failure, and hoarseness in single-level ACDF. The use of Zero-p in single-level ACDF was recommended.

Anterior cervical discectomy and fusion with zero-profile versus stand-alone cages for two-level cervical spondylosis: A retrospective cohort study

OBJECTIVE

To assess the mid-long-term clinical and radiological outcomes of zero-profile (ZP) compared with stand-alone (ST) cages for two-level anterior cervical discectomy and fusion (ACDF).

METHODS

We included 77 patients (39 women and 38 men) who underwent two-level ACDF between May 5, 2016, and May 5, 2020, and who were followed up for at least 1 year. The subjects were divided into the ST (n = 38) and ZP (n = 39) group. For the evaluation of functional status, Japanese Orthopedic Association (JOA), Neck Disability Index (NDI), and Visual Analogue Scale (VAS) scores were used. Additionally, radiological outcomes and procedure complications were observed at final follow-up.

RESULTS

Both groups had excellent clinical outcomes at the final follow-up. There were no significant intergroup (ZP vs. ST) differences in the fusion rate (91.02% vs. 90.79%, P > 0.05) and postoperative dysphagia (15.4% vs. 2.6%, P = 0.108). However, the disc height at the final follow-up in the ZP group was higher than that in the ST group (6.86 ± 0.84 vs. 6.17 ± 1.03, P = 0.002). The ZP group accomplished a lower loss of cervical lordosis (18.46 ± 4.78 vs. 16.55 ± 4.36, P = 0.071), but without reaching statistical significance.

CONCLUSION

ACDF with either ZP or ST cages turns out to be a dependable strategy for two-level ACDF in terms of clinical results. However, compared with the ST, the ZP cage may achieve a significantly lower loss of disc height.

A New Potential Complication in 2-Level Anterior Cervical Discectomy and Fusion with Zero-Profile Devices: Collapse of the Middle Cervical Vertebra

OBJECTIVE

The objective of this study was to describe a new potential complication, collapse in the middle cervical vertebra of consecutive 2-level anterior cervical discectomy and fusion (ACDF), and discuss its possible mechanism.

METHODS

Clinical and radiologic outcome data from 27 consecutive 2-level ACDF patients using zero-profile devices were collected at 1, 3, 6, and 12 months postoperatively, as well as the last follow-up. Dysphagia was assessed using the Bazaz score, and clinical outcomes were analyzed using the neck disability index and Japanese Orthopaedic Association score. Radiographic evaluation included measurements of the overall and surgical segment curvature, identification of collapse, and assessment of the ratio of anterior height and wedge of the upper, middle, and lower vertebrae in the surgical segment.

RESULTS

The application of zero-profile devices to treat consecutive 2-level cervical spondylosis mostly resulted in good midterm clinical outcomes. Surprisingly, as evidenced by the significantly decreased anterior height and wedge ratio of the middle cervical vertebra, collapse was noted immediately in the middle vertebra in 4 patients at 1 month (n = 3) and 3 months (n = 1). The collapse increased for no more than 6 months, and there was no deterioration of clinical and radiological outcomes at the last follow-up.

CONCLUSIONS

Collapse in the middle cervical vertebra of consecutive 2-level ACDF with the application of zero-profile devices can occur in the early postoperative period, which may be due to axial stress concentration and blood supply damage in the middle cervical vertebral body.

Comparative Analysis of Cage Subsidence in Anterior Cervical Decompression and Fusion: Zero Profile Anchored Spacer (ROI-C) vs. Conventional Cage and Plate Construct

Background: Anterior cervical discectomy and fusion (ACDF) has been widely performed to treat cervical generative diseases. Cage subsidence is a complication after ACDF. Although it is known that segmental kyphosis, acceleration of adjacent segmental disease, and restenosis may occur due to cages subsidence; however detailed research comparing zero-profile cages (ROI-C) and conventional plate and cage construct (CPC) on cage subsidence has been lacking.

Objective: The objectives of this study was to compare the rate of postoperative cage subsidence between zero profile anchored spacer (ROI-C) and conventional cage and plate construct (CPC) and investigate the risk factors associated with cage subsidence following ACDF.

Methods: Seventy-four patients with ACDF who received either ROI-C or CPC treatment from October 2013 to August 2018 were included in this retrospective cohort study. Clinical and radiological outcomes and the incidence of cage subsidence at final follow up-were compared between groups. All patients were further categorized into the cage subsidence (CS) and non-cage subsidence (NCS) groups for subgroup analysis.

Results: The overall subsidence rate was higher in the ROI-C group than in the CPC group (66.67 vs. 38.46%, P = 0.006). The incidence of cage subsidence was significantly different between groups for multiple-segment surgeries (75 vs. 34.6%, P = 0.003), but not for single-segment surgeries (54.55 vs. 42.30%, P = 0.563). Male sex, operation in multiple segments, using an ROI-C, and over-distraction increased the risk of subsidence. Clinical outcomes and fusion rates were not affected by cage subsidence.

Conclusion: ROI-C use resulted in a higher subsidence rate than CPC use in multi-segment ACDF procedures. The male sex, the use of ROI-C, operation in multiple segments, and over-distraction were the most significant factors associated with an increase in the risk of cage subsidence.