Long-term Evaluation of Cervical Disc Arthroplasty with the Mobi-C© Cervical Disc: A Randomized, Prospective, Multicenter Clinical Trial with Seven-Year Follow-up

Effect of device constraint: a comparative network meta-analysis of ACDF and cervical disc arthroplasty

BACKGROUND CONTEXT

Clinical trials have demonstrated that cervical disc arthroplasty (CDA) is an effective and safe alternative treatment to anterior cervical discectomy and fusion (ACDF) for cervical degenerative disc disease in the appropriately indicated patient population. Various devices for CDA exist, differing in the level of device constraint.

PURPOSE

To investigate outcomes following Anterior Cervical Discectomy and Fusion (ACDF) versus CDA stratified based on the level of device constraint: Constrained, Semiconstrained, and Unconstrained.

STUDY DESIGN

Systematic review and network meta-analysis.

PATIENT SAMPLE

2,932 CDA patients (979 Constrained, 1,214 Semiconstrained, 739 Unconstrained) and 2,601 ACDF patients from 41 studies that compared outcomes of patients undergoing CDA or ACDF at a single level at a minimum of 2 years follow-up.

OUTCOME MEASURES

Outcomes of interest included the development of adjacent segment degeneration (ASD), index and adjacent segment reoperation rates, range of motion (ROM), high-grade heterotopic ossification (HO, McAfee Grades 3/4), and patient-reported outcomes (NDI/VAS).

METHODS

CDA devices were grouped based on the degrees of freedom (DoF) allowed by the device, as either Constrained (3 DoF), Semiconstrained (4 or 5 DoF), or Unconstrained (6 DoF). A random effects network meta-analysis was conducted using standardized mean differences (SMD) and log relative risk (RR) were used to analyze continuous and categorical data, respectively.

RESULTS

Semiconstrained (p=.03) and Unconstrained CDA (p=.01) demonstrated a significantly lower risk for ASD than ACDF. All levels of CDA constraint demonstrated a significantly lower risk for subsequent adjacent segment surgery than ACDF (p<.001). Semiconstrained CDA also demonstrated a significantly lower risk for index level reoperation than both ACDF and Constrained CDA (p<.001). Unconstrained devices retained significantly greater ROM than both Constrained and Semiconstrained CDA (p<.001). As expected, all levels of device constraint retained significantly greater ROM than ACDF (p<.001). Constrained and Unconstrained devices both demonstrated significantly lower levels of disability on NDI than ACDF (p=.02). All levels of device constraint demonstrated significantly less neck pain than ACDF (p<.05), while Unconstrained CDA had significantly less arm pain than ACDF (p=.02) at final follow-up greater than 2 years.

CONCLUSION

Cervical Disc Arthroplasty, particularly the unconstrained and semiconstrained designs, appears to be more effective than ACDF in reducing the risk of adjacent segment degeneration and the need for further surgeries, while also allowing for greater range of motion and better patient-reported outcomes. Less constrained CDA conferred a lower risk for index level reoperation, while also retaining more range of motion than more constrained devices.

The Fragility of Statistical Findings in Cervical Disc Arthroplasty: a Systematic Review of Randomized Controlled Trials

PURPOSE

This study employs both the fragility index (FI) and fragility quotient (FQ) to assess the level of robustness in the cervical disc arthroplasty (CDA) literature. We hypothesize that dichotomous outcomes involving CDA would exhibit statistical vulnerability.

METHODS

A PubMed search was conducted to evaluate dichotomous data for randomized controlled trials (RCTs) in CDA literature from 2000 to 2023. The FI of each outcome was calculated through the reversal of a single outcome event until significance was reversed. The FQ was calculated by dividing each fragility index by the study sample size. The interquartile range (IQR) was also calculated for the FI and FQ.

RESULTS

Of the 1561 articles screened, 111 met the search criteria, with 35 RCTs evaluating CDA included for analysis. Six hundred and ninety-three outcome events with 130 significant (P < 0.05) outcomes and 563 nonsignificant (P ≥ 0.05) outcomes were identified. The overall FI and FQ for all 693 outcomes were 5 (IQR 3-7) and 0.019 (IQR 0.011-0.043). Fragility analysis of statistically significant outcomes and nonsignificant outcomes both revealed an FI of 5. All of the studies reported loss to follow-up (LTF) data where 65.7% (23) did not report or reported an LTF greater or equal to 5.

CONCLUSIONS

The literature regarding CDA RCTs lacks statistical robustness and may misrepresent the conclusions with the sole use of the P value. By implementing the FI and FQ along with the P value, we believe the interpretation and contextualization of the clinical data surrounding CDA will be better understood.

Cervical Disc Arthroplasty (CDA) versus Anterior Cervical Discectomy and Fusion (ACDF) for Two-Level Cervical Disc Degenerative Disease: An Updated Systematic Review and Meta-Analysis

Background: Anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) are both considered to be efficacious surgical procedures for treating cervical spondylosis in patients with or without compression myelopathy. This updated systematic review and meta-analysis aimed to compare the outcomes of these procedures for the treatment of cervical degenerative disc disease (DDD) at two contiguous levels. Methods: The PubMed, EMBASE, and Cochrane CENTRAL databases were searched up to 1 May 2023. Studies comparing the outcomes between CDA and ACDF in patients with two-level cervical DDD were eligible for inclusion. Primary outcomes were surgical success rates and secondary surgery rates. Secondary outcomes were scores on the Neck Disability Index (NDI) and Visual Analogue Scale (VAS) for neck and arm pain, as well as the Japanese Orthopaedic Association (JOA) score for the severity of cervical compression myelopathy and complication rates. Results: In total, eight studies (two RCTs, four retrospective studies, and two prospective studies) with a total of 1155 patients (CDA: 598; ACDF: 557) were included. Pooled results revealed that CDA was associated with a significantly higher overall success rate (OR, 2.710, 95% CI: 1.949-3.770) and lower secondary surgery rate (OR, 0.254, 95% CI: 0.169-0.382) compared to ACDF. In addition, complication rates were significantly lower in the CDA group than in the ACDF group (OR, 0.548, 95% CI: 0.326 to 0.919). CDA was also associated with significantly greater improvements in neck pain VAS than ACDF. No significant differences were found in improvements in the arm VAS, NDI, and JOA scores between the two procedures. Conclusions: CDA may provide better postoperative outcomes for surgical success, secondary surgery, pain reduction, and postoperative complications than ACDF for treating patients with two-level cervical DDD.

The Statistical Fragility of Trials Comparing Cervical Disc Arthroplasty and Anterior Cervical Discectomy and Fusion: A Meta Analysis

STUDY DESIGN

Meta-analysis.

OBJECTIVE

To assess the robustness of randomized controlled trials (RCTs) that compared cervical disc arthroplasty (CDA) and anterior cervical discectomy and fusion (ACDF) for the treatment of symptomatic degenerative cervical pathology by using fragility indices.

SUMMARY OF BACKGROUND DATA

RCTs comparing these surgical approaches have shown that CDA may be equivalent or even superior to ACDF due to better preservation of normal spinal kinematics.

MATERIALS AND METHODS

RCTs reporting clinical outcomes after CDA versus ACDF for degenerative cervical disc disease were evaluated. Data for outcome measures were classified as continuous or dichotomous. Continuous outcomes included: Neck Disability Index, overall pain, neck pain, radicular arm pain, and modified Japanese Orthopedic Association scores. Dichotomous outcomes included: any adjacent segment disease (ASD), superior-level ASD, and inferior-level ASD. The fragility index (FI) and continuous FI (CFI) were determined for dichotomous and continuous outcomes, respectively. The corresponding fragility quotient (FQ) and continuous FQ were calculated by dividing FI/CFI by sample size.

RESULTS

Twenty-five studies (78 outcome events) were included. Thirteen dichotomous events had a median FI of 7 [interquartile range (IQR): 3-10], and the median FQ was 0.043 (IQR: 0.035-0.066). Sixty-five continuous events had a median CFI of 14 (IQR: 9-22) and a median continuous FQ of 0.145 (IQR: 0.074-0.188). This indicates that, on average, altering the outcome of 4.3 patients out of 100 for the dichotomous outcomes and 14.5 out of 100 for continuous outcomes would reverse trial significance. Of the 13 dichotomous events that included a loss to follow-up data, 8 (61.5%) represented ≥7 patients lost. Of the 65 continuous events reporting the loss to follow-up data, 22 (33.8%) represented ≥14 patients lost.

CONCLUSION

RCTs comparing ACDF and CDA have fair to moderate statistical robustness and do not suffer from statistical fragility.

[Translated article] Less superior adjacent syndrome and lower reoperation rate. Medium- and long-term results of cervical arthroplasty versus anterior cervical arthrodesis: Systematic review and meta-analysis of randomized clinical trials

OBJECTIVE

To compare medium- and long-term postoperative surgical results, especially the adjacent syndrome rate, adverse event rate, and reoperation rate, of patients operated on with cervical arthroplasty or anterior cervical arthrodesis in published randomized clinical trials (RCTs), at one cervical level.

METHODS

Systematic review and meta-analysis. Thirteen RCTs were selected. The clinical, radiological and surgical results were analyzed, taking the adjacent syndrome rate and the reoperation rate as the primary objective of the study.

RESULTS

Two thousand nine hundred and sixty three patients were analyzed. The cervical arthroplasty group showed a lower rate of superior adjacent syndrome (P<0.001), lower reoperation rate (P<0.001), less radicular pain (P=0.002), and a better score of neck disability index (P=0.02) and SF-36 physical component (P=0.01). No significant differences were found in the lower adjacent syndrome rate, adverse event rate, neck pain scale, or SF-36 mental component. A range of motion of 7.91° was also found at final follow-up, and a heterotopic ossification rate of 9.67% in patients with cervical arthroplasty.

CONCLUSION

In the medium and long-term follow-up, cervical arthroplasty showed a lower rate of superior adjacent syndrome and a lower rate of reoperation. No statistically significant differences were found in the rate of inferior adjacent syndrome or in the rate of adverse events.

Less superior adjacent syndrome and lower reoperation rate. Medium- and long-term results of cervical arthroplasty versus anterior cervical arthrodesis: Systematic review and meta-analysis of randomized clinical trials

OBJECTIVE

To compare medium- and long-term postoperative surgical results, especially the adjacent syndrome rate, adverse event rate, and reoperation rate, of patients operated on with cervical arthroplasty or anterior cervical arthrodesis in published randomized clinical trials (RCTs), at one cervical level.

METHODS

Systematic review and meta-analysis. Thirteen RCTs were selected. The clinical, radiological and surgical results were analyzed, taking the adjacent syndrome rate and the reoperation rate as the primary objective of the study.

RESULTS

Two thousand nine hundred and sixty three patients were analyzed. The cervical arthroplasty group showed a lower rate of superior adjacent syndrome (P<0.001), lower reoperation rate (P<0.001), less radicular pain (P=0.002), and a better score of neck disability index (P=0.02) and SF-36 physical component (P=0.01). No significant differences were found in the lower adjacent syndrome rate, adverse event rate, neck pain scale, or SF-36 mental component. A range of motion of 7.91 degrees was also found at final follow-up, and a heterotopic ossification rate of 9.67% in patients with cervical arthroplasty.

CONCLUSION

In the medium and long-term follow-up, cervical arthroplasty showed a lower rate of superior adjacent syndrome and a lower rate of reoperation. No statistically significant differences were found in the rate of inferior adjacent syndrome or in the rate of adverse events.

Trends in Indications and Contraindications for Cervical Disk Arthroplasty from 2009 to 2019

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

Assess trends of indications and contraindications for the use of Cervical Disk Arthroplasty (CDA).

SUMMARY OF BACKGROUND DATA

As spine surgeons become more familiar with CDA, there have been expansions in indications.

METHODS

The Medicare Provider Analysis and Review Limited Data Sets for 2009, 2014, and 2019 were utilized. Patients undergoing elective CDA were included. Diagnosis for index surgery and "contraindications" as defined by original CDA Investigative Device Exemption (IDE) criteria were assessed. Variables were identified by the International Classification of Diseases (ICD)-9 or ICD-10 diagnosis and procedural codes.

RESULTS

A total of 1067 elective CDA patients were included. There were 230 patients in 2009, 300 patients in 2014, and 537 patients in 2019. The proportion of patients aged >65 increased from 35% to 51% (P<0.001). Incidence of CDA for radiculopathy increased from 57% to 69% (P<0.001), myelopathy increased from 23% to 78% (P<0.001), and spondylosis without radiculopathy or myelopathy decreased from 19% to 3% (P<0.001). There were increased incidences of ankylosing spondylitis (0.4% to 2.8%, P=0.007), long-term steroid use (1% to 2%, P=0.039), morbid obesity (2% to 6%, P=0.019), and osteoporosis (1% to 5%, P=0.014). The incidence of hybrid CDA and anterior cervical discectomy and fusion (ACDF) decreased from 28% to 23% (P=0.007).

CONCLUSION

From 2009 to 2019, the number of CDA performed in older patients increased. An increase in the use of CDA for the treatment of myelopathy and radiculopathy and a decrease in the treatment of isolated cervical spondylosis was observed. The proportion of CDA performed in patients with original IDE trial "contraindications" increased. Further research into the efficacy of CDA for patients with contraindications is warranted.

Are Patients With Segmental Cervical Kyphosis Appropriate Candidates for Cervical Disc Arthroplasty (CDA)? A Clinical and Radiographic Analysis Compared to Anterior Cervical Discectomy and Fusion (ACDF)

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To compare the clinical and radiographic outcomes of Anterior Cervical Discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) in patients with preoperative segmental kyphosis.

METHODS

Patients with segmental cervical kyphosis at the operative levels undergoing 1- or 2-level ACDF or CDA from 2017 to 2020 with 2 years of follow were identified. Patient demographics, perioperative data, complication rates, radiographic findings and reported outcomes were analyzed.

RESULTS

A total of 48 patients met inclusion criteria and were included in our study (ACDF: n = 24, CDA: n = 24). Patient demographic data between the 2 cohorts was similar expect for proportion of males (ACDF: 62.5% vs CDA: 33.3%, P = .043). There was no statistical significance in the change of segmental lordosis (ACDF: +8.09° vs CDA: +5.88°, P = .075) between the preoperative and final postoperative period. Additionally, the change in cervical lordosis was similar between groups (ACDF:+ 9.86° vs CDA: +7.60°, P = .226). VAS scores were similar between the 2 groups at every follow-up interval. NDI scores were significantly different at the 6-month, 12 month and the final follow-up. Mean improvements between preoperative and final postoperative periods were statistically superior in the CDA cohort compared to the ACDF cohort (ACDF: 22.8 vs CDA: 24.1, P = .0375).

CONCLUSION

CDA was superior to ACDF in regards to NDI scores following index procedure in patients with preoperative segmental cervical kyphosis. Those in the CDA cohort had similar complication rates, revision rates and radiographic outcomes as those who underwent ACDF.

Relative Efficacy of Cervical Total Disc Arthroplasty Devices and Anterior Cervical Discectomy and Fusion for Cervical Pathology: A Network Meta-Analysis

STUDY DESIGN

Systematic Review and Meta Analysis.

OBJECTIVE

This study sought to compare patient-reported outcomes, success, complications, and radiographic outcomes directly and indirectly between different cervical total disc arthroplasty (TDA) devices and anterior cervical discectomy and fusion (ACDF).

METHODS

Patients of prospective randomized controlled trials of 1-level cervical TDA with a minimum of 2 years follow up were identified in the literature. A frequentist network meta-analysis model was used to compare each outcome across the different TDA devices included and ACDF using the mixed effect sizes.

RESULTS

15 studies were included for quantitative analysis, reporting the outcomes of 2643 patients with an average follow-up was 67.3 months (range: 24-120 months), 1417 of whom underwent TDA and 1226 of whom underwent ACDF. Nine TDA devices were compared to ACDF, including the Bryan, Discover, Kineflex, M6, Mobi-C, PCM, Prestige ST, ProDisc-C, and Secure-C cervical prostheses. Several devices outperformed ACDF for certain outcomes, including Visual Analog Scale (VAS) Arm, Physical Component Score of the Short-Form Health Survey (SF PCS), neurological success, satisfaction, index-level secondary surgical interventions (SSI), and adjacent level surgeries. Cumulative ranking of each intervention assessed demonstrated the highest performance with the M6 prosthesis (P = .70), followed by Secure-C (P = .67), PCM (P = .57), Prestige ST (P = .57), ProDisc-C (P = .54), Mobi-C (P = .53), Bryan (P = .49), Kineflex (P = .49), Discover (P = .39), and ACDF (P = .14).

CONCLUSION

Cervical TDA was found to be superior on most outcomes assessed in the literature of high-quality clinical trials. While most devices demonstrated similar outcomes, certain prostheses such as the M6 were found to outperform others across several outcomes assessed. These findings suggest that the restoration of near-normal cervical kinematics may lead to improved outcomes.

Risk factors for failure to achieve minimal clinically important difference following cervical disc replacement

BACKGROUND CONTEXT

While cervical disc replacement (CDR) has been emerging as a reliable and efficacious treatment option for degenerative cervical spine pathology, not all patients undergoing CDR will achieve minimal clinically important difference (MCID) in patient-reported outcome measures (PROMs) postoperatively-risk factors for failure to achieve MCID in PROMs following CDR have not been established.

PURPOSE

To identify risk factors for failure to achieve MCID in Neck Disability Index (NDI, Visual Analog Scale (VAS) neck and arm following primary 1- or 2-level CDRs in the early and late postoperative periods.

STUDY DESIGN

Retrospective review of prospectively collected data.

PATIENT SAMPLE

Patients who had undergone primary 1- or 2-level CDR for the treatment of degenerative cervical pathology at a single institution with a minimum follow-up of 6 weeks between 2017 and 2022.

OUTCOME MEASURES

Patient-reported outcomes: Neck disability index (NDI), Visual analog scale (VAS) neck and arm, MCID.

METHODS

Minimal clinically important difference achievement rates for NDI, VAS-Neck, and VAS-Arm within early (within 3 months) and late (6 months to 2 years) postoperative periods were assessed based on previously established thresholds. Multivariate logistic regressions were performed for each PROM and evaluation period, with failure to achieve MCID assigned as the outcome variable, to establish models to identify risk factors for failure to achieve MCID and predictors for achievement of MCID. Predictor variables included in the analyses featured demographics, comorbidities, diagnoses/symptoms, and perioperative characteristics.

RESULTS

A total of 154 patients met the inclusion criteria. The majority of patients achieved MCID for NDI, VAS-Neck, and VAS-Arm for both early and late postoperative periods-79% achieved MCID for at least one of the PROMs in the early postoperative period, while 80% achieved MCID for at least one of the PROMs in the late postoperative period. Predominant neck pain was identified as a risk factor for failure to achieve MCID for NDI in the early (OR: 3.13 [1.10-8.87], p-value: .032) and late (OR: 5.01 [1.31-19.12], p-value: .018) postoperative periods, and VAS-Arm for the late postoperative period (OR: 36.63 [3.78-354.56], p-value: .002). Myelopathy was identified as a risk factor for failure to achieve MCID for VAS-Neck in the early postoperative period (OR: 3.40 [1.08-10.66], p-value: .036). Anxiety was identified as a risk factor for failure to achieve MCID for VAS-Neck in the late postoperative period (OR: 6.51 [1.91-22.18], p-value: .003). CDR at levels C5C7 was identified as a risk factor for failure to achieve MCID in NDI for the late postoperative period (OR: 9.74 [1.43-66.34], p-value: .020).

CONCLUSIONS

Our study identified several risk factors for failure to achieve MCID in common PROMs following CDR including predominant neck pain, myelopathy, anxiety, and CDR at levels C5-C7. These findings may help inform the approach to counseling patients on outcomes of CDR as the evidence suggests that those with the risk factors above may not improve as reliably after CDR.

A Novel Intraoperative Posture-Adjustment Apparatus for Correction of Cervical Lordosis in Anterior Cervical Surgery

OBJECTIVE

Cervical alignment is a crucial factor related to the success of anterior cervical surgical procedures. In patients with severe spinal cord compression, a traditional neck pillow (TNP) may not adequately correct cervical position during surgery. Therefore, the aim of this study was to introduce this innovative intraoperative posture-adjustment apparatus (IPAA), and explored its clinical and radiological results in cervical angle correction against TNP in patients who had undergone anterior cervical surgery.

METHODS

The clinical and radiological data of 86 patients who underwent anterior cervical surgery with a minimum follow-up period of 1 year were retrospectively reviewed. Of these, 58 patients underwent IPAA, whereas 28 underwent TNP. Radiological parameters such as the degree of C2-C7 lordosis (CL), functional spinal unit angle (FSUA), C7 slope (C7S), fusion rate, and adjacent segment disease (ASD) were recorded and compared between the groups. Clinical outcomes including the Japanese Orthopaedic Association (JOA), neck disability index (NDI), visual analogue scale (VAS) for neck and arm were recorded. Complications such as kyphosis, dysphagia, Braden Scale score, revision surgery, hematoma, cerebrospinal fluid leakage, wound infection, and deep venous thrombosis were also recorded. The independent t-test or Mann-Whitney U test was used to compare continuous data, and categorical variables were assessed using the Pearson's chi-square test or Fisher's exact test.

RESULTS

Compared with the pre-operative data, the post-operative CL, FSUA, and C7S were significantly increased in both groups. CL, FSUA, and C7S in the IPAA group (14.44 ± 4.94°, 7.36 ± 2.91°, 16.54 ± 4.63°) were significantly higher than those in the TNP group (7.17 ± 8.19°, 4.99 ± 5.36°, 14.19 ± 4.48°; P < 0.05). Although there were no significant differences between the groups in terms of VAS arm and JOA scores, the post-operative and final follow-up NDI and VAS neck scores in the IPAA group were significantly lower than those in the TNP group (p < 0.05). At the last follow-up, the TNP group had significantly more kyphotic patients than the IPAA group (2 vs. 0, p = 0,041). There was no significant difference between the groups in terms of fusion rate, ASD, or complications such as dysphagia, Braden's Scale score, revision surgery, hematoma, cerebrospinal fluid leakage, wound infection, or deep venous thrombosis.

CONCLUSION

IPAA was shown to be more effective than TNP in adjusting cervical alignment (CL, FSUA, and C7S). These findings suggest that IPAA could be used as an alternative way to TNP in neck setting and cervical alignment adjustment and IPAA could potentially improve clinical outcomes after anterior cervical surgery.

Mid-term and Long-term Outcomes After Total Cervical Disk Arthroplasty Compared With Anterior Cervical Discectomy and Fusion: A Systematic Review and Meta-analysis of Randomized Controlled Trials

STUDY DESIGN

A meta-analysis of randomized controlled trials (RCTs).

OBJECTIVE

The aim of this study was to compare mid-term to long-term outcomes of cervical disk arthroplasty (CDA) with those of anterior cervical discectomy and fusion (ACDF) for the treatment of symptomatic cervical degenerative disk disease.

SUMMARY OF BACKGROUND DATA

After ACDF to treat symptomatic cervical degenerative disk disease, the loss of motion at the index level due to fusion may accelerate adjacent-level disk degeneration. CDA was developed to preserve motion and reduce the risk of adjacent segment degeneration. Early-term to mid-term clinical outcomes from RCTs suggest noninferiority of CDA compared with ACDF, but it remains unclear whether CDA yields better mid-term to long-term outcomes than ACDF.

MATERIALS AND METHODS

Two independent reviewers searched PubMed, Embase, and the Cochrane Library for RCTs with at least 60 months of follow-up. The risk ratio or standardized mean difference (and 95% CIs) were calculated for dichotomous or continuous variables, respectively.

RESULTS

Eighteen reports of 14 RCTs published in 2014-2023 were included. The pooled analysis demonstrated that the CDA group had a significantly greater improvement in neurological success and Neck Disability Index than the ACDF group. The ACDF group exhibited a significantly better improvement in the Short Form-36 Health Survey Physical Component Summary than the CDA group. Radiographic adjacent segment degeneration was significantly lower in the CDA group at 60- and 84-month follow-ups; at 120-month follow-up, there was no significant difference between the 2 groups. Although the overall rate of secondary surgical procedures was significantly lower in the CDA group, we did not observe any significant difference at 60-month follow-up between the CDA and ACDF group and appreciated statistically significant lower rates of radiographic adjacent segment degeneration, and symptomatic adjacent-level disease requiring surgery at 84-month and 108- to 120-month follow-up. The rate of adverse events and the neck and arm pain scores in the CDA group were not significantly different from those of the ACDF group.

CONCLUSIONS

In this meta-analysis of 14 RCTs with 5- to 10-year follow-up data, CDA resulted in significantly better neurological success and Neck Disability Index scores and lower rates of radiographic adjacent segment degeneration, secondary surgical procedures, and symptomatic adjacent-level disease requiring surgery than ACDF. ACDF resulted in improved Short Form-36 Health Survey Physical Component Summary scores. However, the CDA and ACDF groups did not exhibit significant differences in overall changes in neck and arm pain scores or rates of adverse events.

Short-term and Long-term Complications of Cervical Disc Arthroplasty

STUDY DESIGN

A narrative review.

OBJECTIVE

This review discusses the short and long-term complications associated with cervical disc arthroplasty (CDA).

SUMMARY OF BACKGROUND DATA

CDA is a safe and effective motion-sparing alternative to fusion for the treatment of cervical disc pathology in patients with cervical radiculopathy or myelopathy. Although CDA offers advantages over fusion within a narrower set of indications, it introduces new technical challenges and potential complications.

METHODS

A systematic search of several large databases, including Cochrane Central, PubMed, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry, was conducted from January 2005 to August 2023 to identify published studies and clinical trials evaluating cervical disc replacement complications and outcomes.

RESULTS

Short-term complications are primarily related to surgical approach and include dysphagia reported as high as ~70%, laryngeal nerve injury ~0%-1.25%, Horner syndrome ~0.06%, hematoma ~0.01%, gross device extrusion ~0.3%, whereas long-term complications include adjacent segment disease reported at ~3.8%, osteolysis ~44%-64%, heterotopic ossification ~7.3%-69.2%, implant failure ~3.3%-3.7%, and implant wear, which varies depending on design.

CONCLUSIONS

Approaches for mitigating complications broadly include meticulous dissection, intraoperative techniques, and diligent postoperative follow-up. This review emphasizes the need for a comprehensive understanding and management of complications to enhance the safety, reproducibility, and success of CDA. As CDA continues to evolve, there remains a critical need for ongoing research to delve deeper into evaluating risk for complications and long-term patient outcomes.

Technique Pearls for Successful Cervical Disc Arthroplasty From More Than 20 Years of Surgical Experience

STUDY DESIGN

Surgical technique paper.

OBJECTIVE

To describe tips and pearls for cervical disc arthroplasty (CDA).

BACKGROUND

CDA has proven to be an effective means of treatment for degenerative cervical disc disease and cervical radiculopathy in properly selected patients who have previously failed non-operative treatment.

METHODS

Surgical tips and pearls garnered from more than 20 years of experience with CDA surgery are described.

RESULTS

This discussion focuses on pearls for successful procedures, including patient selection, patient positioning, surgical technique, and postoperative protocols.

CONCLUSIONS

In correctly selected patients, CDA can be effective in treating cervical degenerative disc disease and radiculopathy. The techniques described here can increase the chance of success and decrease complications.

Current and Expanded Indications for Cervical Disc Arthroplasty: Beyond the FDA IDE Studies

The widespread success of cervical disc arthroplasty (CDA) has led to an interest in expanding indications beyond those outlined in the initial Food and Drug Administration investigational device exemption studies. Some of these off-label indications currently include 3-level and 4-level CDA, hybrid constructs with adjacent segment anterior cervical discectomy and fusion or corpectomy constructs, pre-existing kyphosis, revision of a failed anterior cervical discectomy and fusion to a CDA, CDA in the setting of significant degenerative disc disease and/or facet joint arthropathy, CDA for congenital cervical stenosis, and CDA in the presence of ossification of the posterior longitudinal ligament. This review article will summarize the current literature pertaining to the aforementioned indications.

Emerging Technologies within Spine Surgery

New innovations within spine surgery continue to propel the field forward. These technologies improve surgeons' understanding of their patients and allow them to optimize treatment planning both in the operating room and clinic. Additionally, changes in the implants and surgeon practice habits continue to evolve secondary to emerging biomaterials and device design. With ongoing advancements, patients can expect enhanced preoperative decision-making, improved patient outcomes, and better intraoperative execution. Additionally, these changes may decrease many of the most common complications following spine surgery in order to reduce morbidity, mortality, and the need for reoperation. This article reviews some of these technological advancements and how they are projected to impact the field. As the field continues to advance, it is vital that practitioners remain knowledgeable of these changes in order to provide the most effective treatment possible.

The Anteroposterior Positioning of Viscoelastic Cervical Disc Prosthesis Does Not Alter the Outcomes

BACKGROUND

While first-generation articulated disc prostheses had an ideal positioning schematically as posterior as possible because of their geometrically determined center of rotation, the dogma may change for viscoelastic implants, whose center of rotation is free. Our hypothesis was to assess whether the anteroposterior positioning (APP) of a viscoelastic implant may influence the clinical or radiological outcomes at follow-up.

METHODS

Twenty-five patients (mean age 47 years) were evaluated, with an average follow-up of 25.9 months. The primary outcome was the implants' APP on lateral radiographs. APP between 0% and 49% meant anterior centering, 50% perfect centering, and 51% to 100% posterior centering. The cohort was divided into 2 groups: anterior positioning and posterior positioning. Measurements were performed blindly to the functional outcomes. Visual analog scale for neck pain and radicular pain and the Neck Disability Index were assessed. Range of motion was measured at the last follow-up. The C2 to C7 Cobb angle and the spinocranial angle were also measured.

RESULTS

The median crude offset from the vertebral endplate center was 0.4 mm (mean: 0.3 mm, Q1: -1.5 mm, Q3: 2 mm; range, -2.9 to 4 mm). The mean overall APP was 49%, 45.2% (95% CI, 43.2%-47.1%) in the anterior group, and 54.1% (95% CI, 51.4%-55.3%) in the posterior group. Fifteen patients were in the group anterior positioning and 10 in the group posterior positioning. The mean spinocranial angle was 79° preoperatively and 74° preoperatively (P = 0.04). Functional outcomes were significantly improved at the last follow-up (P < 10-4). There was no significant correlation between the APP, functional outcomes, and range of motion.

CONCLUSION

The APP of the CP-ESP viscoelastic disc arthroplasty does not significantly influence the clinical or radiological outcomes at follow-up. This study suggests that this type of implant tolerates greater variability in its implantation technique.

LEVEL OF EVIDENCE: 4

Cervical disc arthroplasty with the Baguera C prosthesis: clinical and radiological results of a 10-year follow-up study

PURPOSE

We evaluated the long-term safety, mobility and complications of cervical total disc arthroplasty with the Baguera®C prosthesis over 10 years.

METHODS

We included 91 patients treated by arthroplasty for cervical degenerative disc disease. A total of 113 prostheses were implanted (50 one-level, 44 two-level and 19 hybrid constructs). They were assessed for complications, clinically, with NDI and SF-12 questionnaires and by independent radiologists for ROM, HO, disc height and adjacent level degeneration.

RESULTS

No spontaneous migration, loss of fixation, subsidence, vascular complication or dislocation were observed. The reoperation rate was 1%. About 82.7% of the patients were pain free. About 9.9% were taking occasional grade I painkillers. Motricity and sensitivity were preserved in 98.8% and 96.3%. The NDI showed an average functional disability of 17.58%, 26% lower than preoperatively. The SF-12 scores were close to normal health. The average ROM at the treated level was 7.4°. Motion was preserved in 86.6%. Lack of motion was observed in 13.4%. Grades II and III H0 were present in 53.7% and 31.7%, respectively, Grade IV was present in 13.4%. Motion was preserved in 100% of the grades 0-III. The preoperative adjacent level disc height of 4.3 mm remained stable during all the follow-ups at 4.4 mm and 4.2 mm, respectively, at 5 and 10 years.

CONCLUSIONS

After 10 years, cervical arthroplasty with the Baguera®C prosthesis presents excellent safety and functional results and low complications. Motion was preserved in 86.6%, with a 7.4° ROM. Although common, HO did not hinder motion. Adjacent disc height preservation confirms some adjacent level degeneration protection.

The Role of Cervical Disc Arthroplasty in Elite Athletes

PURPOSE OF REVIEW

Cervical disc arthroplasty (CDA) for the treatment of symptomatic cervical disc herniations (CDH) is a promising treatment for professional athletes. In recent years, a number of high-profile athletes have returned to professional play within three months after CDA, raising important questions about the potential of this procedure within this patient group. We provide the first comprehensive review of available literature for the safety and efficacy of CDA in professional contact sport athletes.

RECENT FINDINGS

CDA provides theoretical biomechanical advantages over anterior cervical discectomy and fusion (ACDF) and posterior foraminotomy (PF), as CDA is the only operation for treatment of CDH that provides neural decompression, stability and height restoration, with preserved range of motion. While the comparative long-term results from each procedure are unknown, CDA has provided encouraging promise in its use in professional contact athletes. We aim to aid ongoing discussions regarding the controversies in spine surgery for professional athletes by providing a scientific review of the available evidence-based literature involving cervical disc arthroplasty in this population. In general, we believe that CDA is a viable alternative to ACDF and PF for the contact professional athlete who requires full neck range of motion and desires an expedited return to play. For collision athletes, the short- and long-term safety and efficacy profile of this procedure is promising but still unclear.

Is Cervical Disc Arthroplasty an Effective Treatment for Cervical Degenerative Disease With Osteopenia?

STUDY DESIGN

Retrospective case-control study.

OBJECTIVES

To evaluate postoperative outcomes of single-level cervical disc arthroplasty (CDA) in patients with osteopenia and compare these results with a matched cohort of normal bone mineral density (BMD).

METHODS

Patients who had undergone single-level CDA were collected and screened. Included patients were divided into the osteopenia group and the normal group. 38 eligible patients with osteopenia were included in the final analysis. Subsequently, a 1:1 match was utilized. Clinical, radiographic data, and complications were recorded. Appropriate statistical methods were applied to conduct analysis using SPSS version 24.0.

RESULTS

The mean follow-up time was 30.5 ± 27.3 months. The osteopenia group achieved satisfactory clinical outcomes, with no significant intergroup differences. Additionally, there were no significant differences between groups in any of the radiological parameters, either in cervical alignment or segmental height, or range of motion. The radiological incidence rate of adjacent segmental degeneration and heterotopic ossification (HO) was comparable in both groups, respectively, with a similar composition of ROM-limiting HO. However, the osteopenia group had a tendency of more implant subsidence (2.7% vs 15.2%). The logistic regression analysis showed the osteopenia group had a significantly higher incidence rate of anterior bone loss (ABL) (OR = 5.37, 95% CI: 1.50 - 19.22).

CONCLUSIONS

Single-level CDA for patients with osteopenia achieved similar satisfactory clinical outcomes compared with the normal BMD group. Meanwhile, the osteopenia group maintained adequate sagittal balance and segmental height. Based on this observation, this option may be feasible for selected patients with osteopenia.

Incidence of Heterotopic Ossification at 10 years After Cervical Disk Replacement: A Systematic Review and Meta-analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

This study aimed to assess the incidence of heterotopic ossification (HO) 10 years after cervical disk replacement (CDR).

SUMMARY OF BACKGROUND DATA

HO is a common complication after CDR and may limit the range of motion of the artificial disk. As HO usually progresses slowly, a long-term follow-up is required to better understand its incidence. In recent years, the increasing number of original articles reporting 10-year outcomes gives us the opportunity to better understand the long-term incidence of HO.

MATERIALS AND METHODS

We searched PubMed, Medline, Embase, and Cochrane Library databases to identify eligible studies. The incidence of HO was pooled, and subgroup analysis was performed. Meta-regression analyses were conducted to identify factors contributing to heterogeneity.

RESULTS

Eleven studies with at least 10 years of follow-up comprising 1140 patients who underwent CDR were included. The pooled incidence of overall HO was 70% (95% CI, 60%-81%) at 10 years postoperatively, 60% (95% CI, 44%-75%) at five or six years postoperatively, and 50% (95% CI, 27%-72%) at one or two years postoperatively. The pooled incidence of severe HO (grade 3 or 4) was 37% (95% CI, 29%-45%), and mild HO (grade 1 to 2) was 30% (95% CI, 17%-44%) at 10 years of follow-up. Pooled range of motion decreased from 8.59° before surgery to 7.40° 10 years after surgery. Subgroup analysis showed that HO incidence differed according to the prosthesis type. The earlier publication was associated with a higher pooled incidence of severe HO in the meta-regression analysis.

CONCLUSIONS

This is the first meta-analysis providing detailed information on the pooled 10-year incidence of HO after CDR. The incidence of HO seems to increase with the length of follow-up.

LEVEL OF EVIDENCE

3.

Long-Term Survivorship of Cervical Spine Procedures; A Survivorship Meta-Analysis and Meta-Regression

STUDY DESIGN

Systematic Review.

OBJECTIVES

To conduct a meta-analysis on the survivorship of commonly performed cervical spine procedures to develop survival function curves for (i) second surgery at any cervical level, and (ii) adjacent level surgery.

METHODS

A systematic review of was conducted following PRISMA guidelines. Articles with cohorts of greater than 20 patients followed for a minimum of 36 months and with available survival data were included. Procedures included were anterior cervical discectomy and fusion (ACDF), cervical disc arthroplasty (ADR), laminoplasty (LAMP), and posterior laminectomy and fusion (PDIF). Reconstructed individual patient data were pooled across studies using parametric Bayesian survival meta-regression.

RESULTS

Of 1829 initial titles, 16 citations were included for analysis. 73 811 patients were included in the second surgery analysis and 2858 patients in the adjacent level surgery analysis. We fit a Log normal accelerated failure time model to the second surgery data and a Gompertz proportional hazards model to the adjacent level surgery data. Relative to ACDF, the risk of second surgery was higher with ADR and PDIF with acceleration factors 1.73 (95% CrI: 1.04, 2.80) and 1.35 (95% CrI: 1.25, 1.46) respectively. Relative to ACDF, the risk of second surgery was lower with LAMP with deceleration factor .06 (95% CrI: .05, .07). ADR decreased the risk of adjacent level surgery with hazard ratio .43 (95% CrI: .33, .55).

CONCLUSIONS

In cases of clinical equipoise between fusion procedures, our analysis suggests superior survivorship with anterior procedures. For all procedures, laminoplasty demonstrated superior survivorship.

Cervical Disk Arthroplasty and Range of Motion at 7 Years: Impact on Adjacent Level Degeneration

STUDY DESIGN

Secondary analysis of data collected in a prospective, randomized, noninferiority Food and Drug Administration (FDA) Investigational Device Exemption (IDE) clinical trial.

OBJECTIVE

The objective of this study was to evaluate the impact of range of motion (ROM) following single-level cervical disk arthroplasty (CDA) on the development of radiographic adjacent level degeneration (ALD).

SUMMARY OF BACKGROUND DATA

The rationale for CDA is that maintenance of index-level ROM will decrease adjacent level stresses and ultimately reduce the development of ALD compared with anterior cervical discectomy and fusion. However, little information is available on the impact of hypermobility on the development of ALD after CDA.

MATERIALS AND METHODS

Radiographic assessments were evaluated for index-level flexion-extension ROM and ALD. Continuous data was assessed using 1-way analysis of variance. The relationship between ALD progression and ROM was evaluated using χ 2 tests. The α was set at 0.05.

RESULTS

More ALD progression was observed after anterior cervical discectomy and fusion than CDA ( P =0.002 at the superior and P =0.049 at the inferior level). Furthermore, there was an association between ALD progression and ROM ( P =0.014 at the superior level and P =0.050 at the inferior level) where patients with mid-ROM after CDA experienced the lowest frequency of ALD progression at the superior and inferior levels. Patients with the lowest and highest ROM after CDA experienced a greater increase in ALD score at the inferior level ( P =0.046). Sex and age were associated with ROM groups ( P =0.001 and 0.023, respectively).

CONCLUSIONS

While maintenance of index-level ROM is protective after CDA, patients with the highest ROM after CDA have similar rates of ALD progression to the lowest ROM and greater increases in ALD compared with mid-ROM after CDA. High ROM after CDA may contribute to ALD progression.

Observational, Multicenter Study of the Efficacy and Safety of Cervical Disk Arthroplasty With Mobi-C in the Treatment of Cervical Degenerative Disk Disease. Results at 10 years Follow-Up

BACKGROUND

Cervical disk arthroplasty replacement (CDA) was developed to avoid specific disadvantages of cervical fusion. The purpose of this paper is to provide 10-year follow-up results of an ongoing prospective study after CDA.

METHODS

Three hundred eighty-four patients treated using the Mobi-C (ZimVie, Troyes, France) were included in a prospective multicenter study. Routine clinical and radiologic examinations were reported preoperatively and postoperatively with up to 10-year follow-up. Complications and revision surgeries were also documented.

RESULTS

At 10 years showed significant improvement in all clinical outcomes [Neck Disability Index, visual analog scale (VAS) for arm and neck pain, physical component summary of SF36, and mental component summary of SF36). Motion at the index level increased significantly over baseline (mean range of motion=7.6 vs. 8 degrees at five years and 6.0 degrees preoperatively; P <0.001) and 71.3% of the implanted segments remained mobile (range of motion>3 degrees). Adjacent disks were also mobile at 10 years with the same mobility as preoperatively. At 10 years, 20.9% of the implanted segments demonstrated no heterotopic ossification. Thirty-four patients (8.9%) experienced 41 adverse events, with or without reoperation during the first five years. We found only two additional surgeries after five years. We observed an increased percentage of working patients and a decrease in medication consumption. Regarding the overall outcome, 94% of patients were satisfied.

CONCLUSIONS

Our 10-year results showed significant improvement in all clinical outcomes, with low rates of revision or failure. This experience in patients with long-term follow-up after CDA endorses durable, favorable outcomes in properly selected patients.

Does Facet Distraction Affect Patient Outcomes After ACDF?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim of this study is to determine if there is a correlation between the amount of facet distraction and postoperative patient-reported outcomes after ACDF.

METHODS

A retrospective cohort analysis of patients undergoing 1 to 3 level ACDF for degenerative pathologies at a single academic center was performed. Each patient received upright, lateral cervical spine x-rays at the immediate postoperative time point from which interfacet distance (facet distraction) was measured. Patient-reported outcome measures including NDI, PCS-12, MCS-12, VAS Neck, and VAS Arm pain scores were obtained preoperatively and at short-term (<3 months) and long-term (>1 year) follow-up. Receiver operating curves were generated to evaluate the possibility of a critical interfacet distraction distance. Univariate and multivariate analysis were performed to compare outcomes between groups based on the degree of facet distraction.

RESULTS

A total of 229 patients met the inclusion criteria. Receiver operating curves failed to yield a critical interfacet distraction distance associated with worse post-operative outcomes. Patients were instead grouped based on facet distraction distance below and above the third quartile (0.8mm-2.0 mm, 2.0mm-3.7 mm), with 173 and 56 patients in each respective group. Univariate analysis did not detect any statistically significant differences in outcome measures, recovery ratio, or % MCID achievement at short- and long-term follow-up between groups. Multivariate analysis also failed to demonstrate any significant differences between the facet distraction groups.

CONCLUSION

Increased interfacet distance did not correlate with increased neck pain or disability after an ACDF.

Multilevel cervical disc arthroplasty: a review of optimal surgical management and future directions

OBJECTIVE

Cervical disc arthroplasty (CDA) has been recognized as a popular option for cervical radiculopathy or myelopathy caused by disc problems that require surgery. There have been prospective randomized controlled trials comparing CDA to anterior cervical discectomy and fusion (ACDF) for 1- and 2-level disc herniations. However, the indications for CDA have been extended beyond the strict criteria of these clinical trials after widespread real-world experiences in the past decade. This article provides a bibliometric analysis with a review of the literature to understand the current trends of clinical practice and research on CDA.

METHODS

The PubMed database was searched using the keywords pertaining to CDA in human studies that were published before August 2022. Analyses of the bibliometrics, including the types of papers, levels of evidence, countries, and the number of disc levels involved were conducted. Moreover, a systematic review of the contents with the emphasis on the current practice of multilevel CDA and complex cervical disc problems was performed.

RESULTS

A total of 957 articles published during the span of 22 years were analyzed. Nearly one-quarter of the articles (232, 24.2%) were categorized as level I evidence, and 33.0% were categorized as levels I or II. These studies clearly demonstrated the viability and effectiveness of CDA regarding clinical and radiological outcomes, including neurological improvement, maintenance, and preservation of segmental mobility with relatively low risks for several years postoperation. Also, there have been more papers published during the last decade focusing on multilevel CDA and fewer involving the comparison of ACDF. Overall, there was a clustering of CDA papers published from the US and East Asian countries. Based on substantial clinical data of CDA for 1- and 2-level disc diseases, the practice and research of CDA show a trend toward multilevel and complex disease conditions.

CONCLUSIONS

CDA is an established surgical management procedure for 1- and 2-level cervical disc herniation and spondylosis. The success of motion preservation by CDA-with low rates of complications-has outscored ACDF in patients without deformity. For more than 2-level disc diseases, the surgery shows a trend toward multiple CDA or hybrid ACDF-CDA according to individual evaluation for each level of degeneration.

Cervical Total Disc Replacement and Anterior Cervical Discectomy and Fusion: Comparison of 30-Day Population Comorbidities and Perioperative Complications Using 6 Years of American College of Surgeons National Surgical Quality Improvement Program Participant Use File Data

OBJECTIVE

American College of Surgeons National Surgical Quality Improvement Program Participant Use File data from 2014 through 2019 were used to compare 1- and 2-level anterior cervical discectomy and fusion (ACDF) and cervical total disc replacement (cTDR) with respect to: patient demographics, comorbidities, adverse events, and 30-day morbidity rates.

METHODS

One- and 2-level ACDF and cTDR patients were identified by current procedural terminology codes. Demographics, comorbidities, and adverse events were summarized. Unmatched cohorts were compared using Wilcoxon Rank Sum test for continuous variables, Pearson χ2 test for categorical variables, and 30-day morbidity using inverse probability of treatment weighted log-binomial regression.

RESULTS

American College of Surgeons National Surgical Quality Improvement Program 2014 through 2019 Participant Use File datasets represent 4,862,497 unique patients, identifying 13,347 1-level, 6933 2-level ACDF, 3114 1-level, and 862 2-level cTDR patient cohorts. Statistically significant differences between cohorts are extensive: age, sex, race, admission status, patient origin, discharge disposition, emergent surgery, surgical specialty, American Society of Anesthesiologists classification, wound class, operative time, hospital LOS, BMI, functional status, smoking, diabetes, dyspnea, chronic obstructive pulmonary disease, congestive heart failure, hypertension, renal failure, dialysis, cancer, steroid use, anemia, bleeding disorders, systemic sepsis, and number of concurrent comorbid conditions. Inverse probability of treatment weighted log-binomial models, demonstrated increased risk of deep venous thrombosis/thrombophlebitis, pulmonary embolism, deep incisional surgical site infection, pneumonia, and unplanned return to operating room associated with ACDF while increased risk of cerebral vascular accident/stroke with neurological deficit and myocardial infarction associated with cTDR. The composite complications outcome favors cTDR over ACDF for 30-day morbidity. No mortalities occurred within the cTDR cohort.

CONCLUSIONS

Adjusting for demographics and comorbidities; ACDF has a higher average risk of adverse event. When ACDF and cTDR are equipoise, consideration for cTDR may be indicated in populations with higher rates of comorbid conditions.

Safety and Validity of Anterior Cervical Disc Replacement for Single-level Cervical Disc Disease: Initial Two-year Follow-up of the Prospective Observational Post-marketing Surveillance Study for Japanese Patients

Anterior cervical disc replacement (ACDR) using cervical artificial disc (CAD) has the advantage of maintaining the range of motion (ROM) at the surgical level, subsequently reducing the postoperative risk of adjacent disc disease. Following the approval for the clinical use in Japan, a post-marketing surveillance (PMS) study was conducted for two different types of CAD, namely, Mobi-C (metal-on-plastic design) and Prestige LP (metal-on-metal design). The objective of this prospective observational multicenter study was to analyze the first 2-year surgical results of the PMS study of 1-level ACDR in Japan. A total of 54 patients were registered (Mobi-C, n = 24, MC group; Prestige LP, n = 30, PLP group). Preoperative neurological assessment revealed radiculopathy in 31 patients (57.4%) and myelopathy in 15 patients (27.8%). Preoperative radiological assessment classified the disease category as disc herniation in 15 patients (27.8%), osteophyte in 6 patients (11.1%), and both in 33 patients (61.1%). The postoperative follow-up rates at 6 weeks, 6 months, 1 year, and 2 years after ACDR were 92.6%, 87.0%, 83.3%, and 79.6%, respectively. In both groups, patients' neurological condition improved significantly after surgery. Radiographic assessment revealed loss of mobility at the surgical level in 9.5% of patients in the MC group and in 9.1% of patients in the PLP group. No secondary surgeries at the initial surgical level and no serious adverse events were observed in either group. The present results suggest that 1-level ACDR is safe, although medium- to long-term follow-up is mandatory to further verify the validity of ACDR for Japanese patients.

Segmental range of motion after cervical total disc arthroplasty at long-term follow-up: a systematic review and meta-analysis

OBJECTIVE

As an alternative procedure to anterior cervical discectomy and fusion, total disc arthroplasty (TDA) facilitates direct neural decompression and disc height restoration while also preserving cervical spine kinematics. To date, few studies have reported long-term functional outcomes after TDA. This paper reports the results of a systematic review and meta-analysis that investigated how segmental range of motion (ROM) at the operative level is maintained with long-term follow-up.

METHODS

PubMed and MEDLINE were queried for all published studies pertaining to cervical TDA. The methodology for screening adhered strictly to the PRISMA guidelines. All English-language prospective studies that reported ROM preoperatively, 1 year postoperatively, and/or at long-term follow-up of 5 years or more were included. A meta-analysis was performed using Cochran's Q and I2 to test data for statistical heterogeneity, in which case a random-effects model was used. The mean differences (MDs) and associated 95% confidence intervals (CIs) were reported.

RESULTS

Of the 12 studies that met the inclusion criteria, 8 reported the long-term outcomes of 944 patients with an average (range) follow-up of 99.86 (60-142) months and were included in the meta-analysis. There was no difference between preoperative segmental ROM and segmental ROM at 1-year follow-up (MD 0.91°, 95% CI -1.25° to 3.07°, p = 0.410). After the exclusion of 1 study from the comparison between preoperative and 1-year ROM owing to significant statistical heterogeneity according to the sensitivity analysis, ROM significantly improved at 1 year postoperatively (MD 1.92°, 95% CI 1.04°-2.79°, p < 0.001). However, at longer-term follow-up, the authors again found no difference with preoperative segmental ROM, and no study was excluded on the basis of the results of further sensitivity analysis (MD -0.22°, 95% CI -1.69° to -1.23°, p = 0.760). In contrast, there was a significant decrease in ROM from 1 year postoperatively to final long-term follow-up (MD -0.77°, 95% CI -1.29° to -0.24°, p = 0.004).

CONCLUSIONS

Segmental ROM was found to initially improve beyond preoperative values for as long as 1 year postoperatively, but then ROM deteriorated back to values consistent with preoperative motion at long-term follow-up. Although additional studies with further longitudinal follow-up are needed, these findings further support the notion that cervical TDA may successfully maintain physiological spinal kinematics over the long term.

Longitudinal assessment of segmental motion of the cervical spine following total disc arthroplasty: a comparative analysis of devices

OBJECTIVE

Total disc arthroplasty (TDA) has been shown to be an effective and safe treatment for cervical degenerative disc disease at short- and midterm follow-up. However, there remains a paucity of literature reporting the differences between individual prosthesis designs with regard to device performance. In this study, the authors evaluated the long-term maintenance of segmental range of motion (ROM) at the operative cervical level across a diverse range of TDA devices.

METHODS

In this study, the authors retrospectively evaluated all consecutive patients who underwent 1- or 2-level cervical TDA between 2005 and 2020 at a single institution. Patients with a minimum of 6 months of follow-up and lateral flexion/extension radiographs preoperatively, 2 months postoperatively, and at final follow-up were included. Radiographic measurements included static segmental lordosis, segmental range of motion (ROM) on flexion/extension, global cervical (C2-7) ROM on flexion/extension, and disc space height. The paired t-test was used to evaluate improvement in radiographic parameters. Subanalysis between devices was performed using one-way ANCOVA. Significance was determined at p < 0.05.

RESULTS

A total of 85 patients (100 discs) were included, with a mean patient age of 46.01 ± 8.82 years and follow-up of 43.56 ± 39.36 months. Implantations included 22 (22.00%) M6-C, 51 (51.00%) Mobi-C, 14 (14.00%) PCM, and 13 (13.00%) ProDisc-C devices. There were no differences in baseline radiographic parameters between groups. At 2 months postoperatively, PCM provided significantly less segmental lordosis (p = 0.037) and segmental ROM (p = 0.039). At final follow-up, segmental ROM with both the PCM and ProDisc-C devices was significantly less than that with the M6-C and Mobi-C devices (p = 0.015). From preoperatively to 2 months postoperatively, PCM implantation led to a significant loss of lordosis (p < 0.001) and segmental ROM (p = 0.005) relative to the other devices. Moreover, a significantly greater decline in segmental ROM from 2 months postoperatively to final follow-up was seen with ProDisc-C, while segmental ROM increased significantly over time with Mobi-C (p = 0.049).

CONCLUSIONS

Analysis by TDA device brand demonstrated that motion preservation differs depending on disc design. Certain devices, including M6-C and Mobi-C, improve ROM on flexion/extension from preoperatively to postoperatively and continue to increase slightly at final follow-up. On the other hand, devices such as PCM and ProDisc-C contributed to greater segmental stiffness, with a gradual decline in ROM seen with ProDisc-C. Further studies are needed to understand how much segmental ROM is ideal after TDA for preservation of physiological cervical kinematics.

Top 100 most cited articles on anterior cervical discectomy and fusion

Study Design

Bibliometric analysis.

Objective

Anterior cervical discectomy and fusion (ACDF) is a typical surgical method in spine surgery and has progressed significantly in the last several decades. The purpose of this study is to determine how the 100 most-cited original articles on ACDF have been the most influential in this field by identifying and analyzing them.

Methods

The articles on ACDF were identified by searching the Thomson ISI Web of Science database on 30 May 2022. The 100 most-cited articles were selected according to specific criteria. The data extracted from the articles included title, publication date, total citations, journal name, first author, institutions, and keywords.

Results

The total number of citations was 13,181, with a mean number of 131.81 ± 100.18. The publication dates ranged from 1994 to 2018. Most of these articles originated in the United States (68%) and were published in the 2000s (32%) and 2010s (48%). Spine published most of the articles (30%), followed by the Journal of Neurosurgery-Spine (16%), Spine Journal (14%), and European Spine Journal (13%). The most prolific author was Dr. Todd J Albert (n = 7), with 1,312 citations. The Texas Back Institute was the most productive institution (n = 10). The keywords ACDF, cervical spine, cervical spine, and fusion showed the highest degree of centrality.

Conclusion

One hundred top-cited articles on ACDF were identified and analyzed in this study. We demonstrate that ACDF is a growing and popular area of research, with the focus of research varying through timeline trends. This will provide a comprehensive and detailed basis for spine surgeons to make clinical decisions and assimilate the research focus of cervical spine surgery.

Research protocol: Cervical Arthroplasty Cost Effectiveness Study (CACES): economic evaluation of anterior cervical discectomy with arthroplasty (ACDA) versus anterior cervical discectomy with fusion (ACDF) in the surgical treatment of cervical degenerative disc disease - a randomized controlled trial

Introduction

To date, there is no consensus on which anterior surgical technique is more cost-effective in treating cervical degenerative disc disease (CDDD). The most commonly used surgical treatment for patients with single- or multi-level symptomatic CDDD is anterior cervical discectomy with fusion (ACDF). However, new complaints of radiculopathy and/or myelopathy commonly develop at adjacent levels, also known as clinical adjacent segment pathology (CASP). The extent to which kinematics, surgery-induced fusion, natural history, and progression of disease play a role in the development of CASP remains unclear. Anterior cervical discectomy with arthroplasty (ACDA) is another treatment option that is thought to reduce the incidence of CASP by preserving motion in the operated segment. While ACDA is often discouraged, as the implant costs are higher while the clinical outcomes are similar to ACDF, preventing CASP might be a reason for ACDA to be a more cost-effective technique in the long term.

Methods and analysis

In this randomized controlled trial, patients will be randomized to receive ACDF or ACDA in a 1:1 ratio. Adult patients with single- or multi-level CDDD and symptoms of radiculopathy and/or myelopathy will be included. The primary outcome is cost-effectiveness and cost-utility of both techniques from a healthcare and societal perspective. Secondary objectives are the differences in clinical and radiological outcomes between the two techniques, as well as the qualitative process surrounding anterior decompression surgery. All outcomes will be measured at baseline and every 6 months until 4 years post-surgery.

Discussion

High-quality evidence regarding the cost-effectiveness of both ACDA and ACDF is lacking; to date, there are no prospective trials from a societal perspective. Considering the aging of the population and the rising healthcare costs, there is an urgent need for a solid clinical cost-effectiveness trial addressing this question.

Trial registration

ClinicalTrials.gov NCT04623593. Registered on 29 September 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06574-5.

Outcomes of cervical arthroplasty versus anterior cervical arthrodesis: a systematic review and meta-analysis of randomized clinical trials with a minimum follow-up of 7-year

PURPOSE

Compare the outcomes of randomized clinical trials of cervical disc arthroplasty (CDA) versus anterior cervical discectomy with fusion (ACDF), with a minimum follow-up of 7 years.

METHODS

Nine randomized clinical trials were selected. The clinical, radiological, and surgical outcomes were analyzed, including functional and pain scores, range of motion, adjacent segment degeneration, adverse events, and need for reoperation.

RESULTS

2664 patients were included in the study. Pooled results indicated that the CDA group had a significantly higher overall success rate (p < 0.001), a higher improvement in the neck disability index (NDI) (p = 0.002), less VAS arm pain (p = 0.01), and better health questionnaire SF-36 physical component (p = 0.01) than ACDF group. Likewise, the pooled results indicated a significantly higher motion rate (p < 0.001), less adjacent syndrome (p < 0.05), and a lower percentage of reoperation (p < 0.001) in the CDA group. There were no significant differences between the CDA and ACDF groups in the neck pain scale (p = 0.11), the health questionnaire SF-36 mental component (p = 0.10), and in adverse events (p = 0.42).

CONCLUSION

In long-term follow-up, CDA showed a better overall success rate, better improvement in NDI, less VAS arm pain, better health questionnaire SF-36 physical component, a higher motion rate, less adjacent syndrome, and less reoperation rate than ACDF. No significant differences were found in the neck pain scale, SF-36 mental component, and in adverse events.

A Systematic Review on Neurological Outcomes for Cervical Degenerative Myelopathy After Anterior Decompression Surgery: Motion Preservation vs Fusion

BACKGROUND

Although it is well established that surgically treated patients with cervical degenerative myelopathy (CDM) improve irrespective of the anterior decompression technique used, no consensus exists on what technique is superior in terms of neurological recovery. A general concern exists that anterior cervical discectomy with arthroplasty (ACDA) leads to less favorable outcomes in CDM due to microtrauma caused by preserved mobility. It is remarkable that current literature mainly uses pain scores to assess clinical outcomes after anterior decompression surgery, especially considering that pain may not be the most relevant outcome for CDM. This systematic review evaluated the literature concerning neurological outcomes in patients with CDM treated with anterior decompression surgery and assessed by validated myelopathy scores.

METHODS

Systematic searches were carried out in PubMed, EMBASE, Web of Science, CINAHL, and the Cochrane Library. Prospective studies were included when patients with isolated CDM were treated with anterior decompression surgery, and a validated myelopathy outcome score was used.

RESULTS

A total of 11 studies were included from the 16,032 identified studies. All studies used the modified Japanese Orthopedic Association (JOA) outcome score and showed improvement for all anterior techniques. The mean improvement in anterior cervical discectomy and fusion (ACDF) was 4.80 and 3.64 for the modified JOA and JOA outcome scores, respectively. The JOA for ACDA showed a mean improvement of 5.51. The overall quality of the included articles was low to moderate according to the Cochrane tool.

CONCLUSION

Neurological recovery of CDM is similar after all anterior decompression techniques, including ACDA when compared with ACDF.

CLINICAL RELEVANCE

The current literature gives no reason to dissuade the use of ACDA in cervical myelopathy.

LEVEL OF EVIDENCE: 3

Cost-effectiveness of anterior surgical decompression surgery for cervical degenerative disk disease: a systematic review of economic evaluations

PURPOSE

No clear consensus exists on which anterior surgical technique is most cost-effective for treating cervical degenerative disk disease (CDDD). One of the most common treatment options is anterior cervical discectomy with fusion (ACDF). Anterior cervical discectomy with arthroplasty (ACDA) was developed in an effort to reduce the incidence of clinical adjacent segment pathology and associated additional surgeries by preserving motion. This systematic review aims to evaluate the evidence regarding the cost-effectiveness of anterior surgical decompression techniques used to treat radiculopathy and/or myelopathy caused by CDDD.

METHODS

The search was conducted in PubMed, EMBASE, Web of Science, CINAHL, EconLit, NHS-EED and the Cochrane Library. Studies were included if healthcare costs and utility or effectivity measurements were mentioned.

RESULTS

A total of 23 studies were included out of the 1327 identified studies. In 9 of the 13 studies directly comparing ACDA and ACDF, ACDA was the most cost-effective technique, with an incremental cost effectiveness ratio ranging from $2.900/QALY to $98.475/QALY. There was great heterogeneity between the costs of due to different in- and exclusion criteria of costs and charges, cost perspective, baseline characteristics, and calculation methods. The methodological quality of the included studies was moderate.

CONCLUSION

The majority of studies report ACDA to be a more cost-effective technique in comparison with ACDF. The lack of uniform literature impedes any solid conclusions to be drawn. There is a need for high-quality cost-effectiveness research and uniformity in the conduct, design and reporting of economic evaluations concerning the treatment of CDDD.

TRIAL REGISTRATION

PROSPERO Registration: CRD42020207553 (04.10.2020).

Do Inflammatory Cytokines Affect Patient Outcomes After ACDF?

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

The aim was to determine the relationship between serum inflammatory mediators, preoperative cervical spine disease severity, and clinical outcomes after anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

Given the role of the inflammatory cascade in spinal degenerative disease, it has been hypothesized that inflammatory markers may serve as a predictor of patient outcomes after surgery.

MATERIALS AND METHODS

All patients over age 18 who underwent ACDF for cervical spondylosis with associated radiculopathy and/or myelopathy between 2015 and 2017 from a single institution were prospectively recruited. Preoperative serum inflammatory markers including interleukin (IL)-6, IL-8, tumor necrosis factor-α, high-mobility group box-1 (HMGB1), and white blood cells were measured and correlated to patient demographics, surgical characteristics, duration of symptoms, previous opioid use, and preoperative and 1-year postoperative patient-reported outcomes measures (PROMs) including the neck disability index (NDI), visual analog scale neck pain, visual analog scale arm pain, and Physical and Mental Component Scores of the Short Form-12 (PCS and MCS, respectively) using spearman's rho coefficient.

RESULTS

A total of 77 patients were enrolled with follow-up PROMs available for 62% (n=48) of patients at a minimum of 1-year after ACDF. The absolute concentrations of IL-6 and tumor necrosis factor-α were found to be weakly correlated with one another (ρ=0.479). Preoperative symptoms lasting <1-year were weakly correlated with elevation in HMGB1 (ρ=0.421). All other patient demographics exhibited negligible correlation with the preoperative inflammatory markers. Lower preoperative PCS (ρ=0.355) and higher preoperative NDI (ρ=0.336) were weakly correlated with elevated HMGB1. Lower MCS (ρ=0.395) and higher NDI (ρ=0.317) preoperatively were weakly correlated with elevated white blood cells. Postoperative improvement in MCS (ρ=0.306) and MCS recovery ratio (ρ=0.321) exhibited a weakly positive correlation with IL-6.

CONCLUSION

Preoperative cytokine levels demonstrated minimal correlation with preoperative symptoms or clinical improvement, suggesting that profiling of patient cytokines has limited utility in predicting outcomes after ACDF.

LEVEL OF EVIDENCE

Level III.

Catastrophic delayed cervical arthroplasty failure: illustrative case

BACKGROUND

Cervical disc replacement (CDR) is an increasingly used alternative to fusion for symptomatic cervical disc disease. While more studies have suggested favorability of CDR over fusion procedures, limited data exist regarding implant fatigability. Here, the authors present a unique and previously unreported failure of the M6-C prosthesis causing spinal cord injury.

OBSERVATIONS

A 49-year-old female with history of cervical degenerative disease and prior C4–7 M6-C arthroplasty presented 9 years later after a minor fall from standing. She endorsed bilateral hand numbness ascending to forearms and shoulders, with dysesthesias and weakness. Imaging showed fractured arthroplasty penetrating the spinal cord. Revision surgery found a ruptured arthroplasty annulus with metal piece piercing the spinal cord. Partial C4 and C5 corpectomy was performed to remove the integrated fins of the arthroplasty and inspect the cord and dura. This was reconstructed with a corpectomy cage and plate. The patient made an excellent recovery, with improvement in her weakness and resolution of her sensory symptoms.

LESSONS

Possibility of fatigue-related failures presenting years after implantation have only been infrequently reported but can be catastrophic for patients. The authors encourage further discussions in this area, increased counseling with patients, and recommend a patient registry to better document adverse events.

How Do Patients With Predominant Neck Pain Improve After Anterior Cervical Discectomy and Fusion for Cervical Radiculopathy?

BACKGROUND

The presence of predominant pain in the arm vs the neck as a predictor of postoperative outcomes after anterior cervical discectomy and fusion (ACDF) has been seldom reported; therefore, the purpose of this study was to determine whether patients with predominant neck pain improve after surgery compared to patients with predominant arm pain or those with mixed symptoms in patients undergoing ACDF for radiculopathy.

METHODS

A retrospective cohort study was conducted on patients who underwent ACDF at a single center from 2016 to 2018. Patients were split into groups based on preoperative neck and arm pain scores: neck (N) pain dominant group (visual analog scale [VAS] neck ≥ VAS arm by 1.0 point); neutral group (VAS neck < VAS arm by 1.0 point); or arm (A) pain dominant group (VAS arm ≥ VAS neck by 1.0 point), using a threshold difference of 1.0 point. Subsequently, individuals were substratified into 2 groups based on the arm to neck pain ratio (ANR): non-arm pain dominant defined as ANR ≤1.0 and arm pain dominant (APD) defined as ANR >1.0. Patient-reported outcome measurements including Neck Disability Index (NDI), Physical Component Score-12, and Mental Component Score (MCS-12) were compared between groups.

RESULTS

No significant differences between groups when stratifying patients using a threshold difference of 1.0 point. When stratifying patients using the ANR, those in the APD group had significantly higher postoperative MCS-12 (P = 0.008) and NDI (P = 0.011) scores. In addition, the APD group showed a greater magnitude of improvement for MCS-12 and NDI scores (P = 0.043 and P = 0.038, respectively). Multiple linear regression showed that the A and the APD groups were both independent predictors of improvement in NDI.

CONCLUSION

Patients with dominant arm pain showed significantly greater improvement in terms of MCS-12 and NDI scores compared to patients with dominant neck pain.

CLINICAL RELEVANCE

To compare the impact of ACDF on arm and neck pain in the context of cervical radiculopathy using patient-reported outcome measures as an objective measurement.

LEVEL OF EVIDENCE: 3

Failure in cervical total disc arthroplasty: single institution experience, systematic review of the literature, and proposal of the RUSH TDA failure classification system

BACKGROUND CONTEXT

Cervical total disc arthroplasty (TDA) is an alternative procedure to anterior cervical discectomy and fusion that facilitates neural decompression while both preserving motion of the spinal unit and decreasing the risk for degenerative changes at adjacent segments. However, due to its more recent introduction in clinical practice and low complication rates, the modes by which TDA may fail remain to be described.

PURPOSE

This study sought to identify the modes and frequencies of cervical TDA failure in order to propose a novel classification system.

STUDY DESIGN

Retrospective cohort and systematic review.

PATIENT SAMPLE

Patients who underwent single or two-level TDA for cervical radiculopathy or myelopathy at a single institution and in the literature of medium and large prospective studies.

OUTCOME MEASURES

Cervical TDA failure, defined as subsequent surgical intervention at the index segment.

METHODS

This study retrospectively reviewed patients who underwent single or two-level TDA for cervical radiculopathy or myelopathy at a single institution to identify the potential implant failure modes. A systematic review and meta-analysis of prospective data in the literature was then performed to further supplement failure mode identification and to describe the rates at which the various failure types occurred. Statistical analysis included between-group comparisons of Non-Failed and Failed patients and frequencies of each failure type among Failed patients.

RESULTS

A retrospective review at our institution of 169 patients (201 levels) identified eight failures, for a failure rate of 4.7%. Additionally, seven patients were revised who had the primary surgery at an outside institution. The systematic review of 3976 patients (4525 levels) identified 165 (4.1%) additional failures. Using this data, six primary failure types were classified, with several subtypes. These include recurrent or persistent index-level stenosis (Type I); migration (Type II) presenting as gross extrusion (A) or endplate failure with subsidence/acute fracture (B); instability (Type III) due to mechanical loosening (A), septic loosening (B), or device fracture (C); device motion loss (Type IV) such as "locking" of the device in kyphosis; implantation error (Type V) due to malposition (A) or improper sizing (B); and wear (Type VI) either without osteolysis (A) or with wear-particle-induced osteolysis (B). Stenosis (Type I) was the most common mode of failure found both through retrospective review and in the literature.

CONCLUSIONS

Cervical TDA fails through six primary mechanisms. While rates of certain failures requiring subsequent surgical intervention are low, it is possible that these complications may become more prevalent upon further longitudinal observation. Thus, future application and validation of this classification system is warranted to evaluate how failure frequencies change over time and with larger patient samples.

A meta-analysis comparing the short- and mid- to long-term outcomes of artificial cervical disc replacement(ACDR) with anterior cervical discectomy and fusion (ACDF) for the treatment of cervical degenerative disc disease

PURPOSE

Anterior cervical discectomy and fusion (ACDF) surgery is commonly performed to treat cervical degenerative disc disease (CDDD). The lost of range of motion (ROM) is also found after ACDF, which contributes to degenerate in adjacent segment disease (ASD). Artificial cervical disc replacement (ACDR), an alternative to ACDF, is developed to preserve the ROM and reduce ASD. This article aims to compare the outcomes between ACDR and ACDF in the short-, mid-, and long-term.

METHODS

Databases including Cochrane, Embase, PubMed, and Web of Science were searched. Only RCTs were included in this meta-analysis, and the search strategy followed the requirements of the Cochrane Handbook. The strength of evidence was assessed using GRADE. Two reviewers independently assessed the methodological quality of each included study and extracted the relevant data.

RESULTS

Thirty prospective RCTs were included. Prolonged operative duration, better overall success, neurological success, and NDI success rates were found in ACDR group in all follow-up periods, with lower dysphagia/dysphonia during short-term follow-up. Moreover, a lower ASD was found in ACDR group during long-term follow-up and overall analysis, with lower reoperation rates in all follow-up periods. Comparable length of hospital stay and blood loss were found in both groups. Moreover, ASD was similar in short- and mid-term follow-ups, while dysphagia/dysphonia incidence was similar in mid- and long-term follow-ups. The incidence of implant events was comparable in all follow-up periods (p > 0.05).

CONCLUSIONS

ACDR is as effective as ACDF and superior for some success rates. Disc replacement can reduce the risk of dysphagia/dysphonia, ASD, and re-operation.

Clinical adjacent segment pathology after anterior cervical discectomy, with and without fusion, for cervical degenerative disc disease: A single center retrospective cohort study with long-term follow-up

Introduction

Research question

Materials & methods

Results

Discussion & conclusion

•

CASP developed in 9.7% patients, of whom 70.7% required additional adjacent level surgery.

•

Very low incidence of symptomatic cage subsidence after ACDF with stand-alone cages.

•

Discectomy alone significantly accelerated the development of CASP.

•

Baseline degeneration was not associated with the development of CASP.

Preliminary Clinical Outcome of One-level Mobi-C Total Disc Replacement in Japanese Population

Introduction

In 2018, the first Mobi-C^Ⓡ total disk replacement (TDR) case was performed in Japan. In this study, we examined the preliminary clinical outcome of Mobi-C^Ⓡ for degenerative cervical spine disease.

Methods

We examined 24 consecutive patients who underwent 1-level TDR after 2018 and followed up for more than 6 months after surgery. The evaluation criteria included age, gender, diagnosis, follow-up period, surgical level, implant size, surgery time, intraoperative bleeding volume, complications, revision surgery, imaging findings, JOA score, and various questionnaires.

Results

The mean age was 52.7 years, 13 males and 11 females. There were 15 cases of cervical disk herniation and 9 cases of cervical spondylosis. The mean follow-up period was 17.4 months. Surgical levels were C3/4 in 4 cases, C4/5 in 2 cases, C5/6 in 16 cases, and C6/7 in 2 cases. The mean operation time was 138.5 minutes, the amount of intraoperative bleeding was 32.1 ml, and there were no serious intraoperative complications. The range of motion of the affected level increased significantly, from 6.6 degrees preoperatively to 12.2 degrees at final follow-up. No patients required revision surgery at final follow-up, and there were no cases of heterotopic ossification or adjacent segment disease. One patient exhibited radiculopathy due to mild subsidence 1 year after surgery, and 1 had asymptomatic contact of device plates. Preoperative and final JOA scores improved from 11.7 to 15.8 points, and NRS improved from 4.3 to 1.3 points for neck pain and 4.3 to 1.7 points for arm pain. Preoperative and final NDI improved from 39.7% to 14.0%, and EQ-5D improved from 0.602 to 0.801.

Conclusions

The short-term treatment outcomes of Mobi-C^Ⓡ TDR were generally favorable. Spine surgeons should comply with guidelines when introducing this procedure and strive to adopt this new technology in Japan.

Artificial disc replacement and adjacent-segment pathology: 10-year outcomes of a randomized trial

OBJECTIVE

Artificial disc replacement (ADR) is designed to preserve motion and thus protect against adjacent-segment pathology (ASP) and act as an alternative treatment to fusion surgery. The question remains, how well do ADR devices perform after 10 years of follow-up compared with fusion surgery in terms of patient satisfaction, sustainability, and protection against ASP?

METHODS

This was the 10-year follow-up study of 153 participants who underwent ADR or fusion surgery after anterior decompression due to cervical degenerative radiculopathy (ISRCTN registration no. 44347115). Scores on the Neck Disability Index (NDI), EQ-5D, and visual analog scale for neck and arm pain were obtained from the Swedish Spine Registry and analyzed using ANCOVA. Information about secondary surgical procedures was collected from medical records and presented as Kaplan-Meier curves. MRI and flexion-extension radiography were performed, and ASP was graded according to the Miyazaki classification system.

RESULTS

Ten participants were lost to follow-up, which left 143 participants (80 underwent ADR and 65 underwent anterior cervical discectomy and fusion). There were no differences between groups in terms of patient-reported outcome measures (10-year difference in NDI scores 1.7 points, 95% CI -5.1 to 8.5, p = 0.61). Nineteen (24%) participants in the ADR group compared with 9 (14%) in the fusion group underwent secondary surgical procedures. The higher reoperation rate of the ADR group was mainly due to 11 female participants with device loosening. The rates of reoperation due to ASP were similar between groups, which was confirmed with MRI assessment of ASP that also showed no differences between the groups (p = 0.21).

CONCLUSIONS

This was the first 10-year follow-up study to compare ADR with fusion surgery and to provide MRI information for the assessment of ASP. The authors found no benefit of ADR over fusion surgery after anterior decompression for cervical degenerative radiculopathy.

Study on biomechanical analysis of two-level cervical Mobi-C and arthrodesis

OBJECTIVE

To investigate the range of motion (ROM) index of a two-level cervical arthroplasty.

METHODS

Seven human cadaveric spines were biomechanically examined from C2 level to T1 level under intact status and the following conditions: 2-level arthroplasty (C4-C6) employing Mobi-C devices (MM group), 2-level anterior cervical discectomy and fusions (2-ACDFs) (FF group), and both as a hybrid surgery (HS) (MF group and FM group). Multidirectional flexibility examination was conducted according to the Panjabi hybrid testing protocol. Unconstrained intact moments of ±1.5 NM were performed for axial rotation (AR) flexion/extension (FE), and lateral bending (LB).

RESULTS

No statistical differences were found between the intact spine and MM group at the operative- and adjacent-level kinematics in the three loading conditions, except that C4-C5 ROM significantly increased in the axial rotation loading (P<0.05). Compared with the intact spine, MF group led to a significant decrease at the arthrodesis segment ROM C5-C6 in the three loading (P<0.05), with corresponding significantly increased at C4-C5 in FE and AR (P<0.05). FM group resulted in a significant decrease in ROM C4-C5 (P<0.05) with corresponding significantly increased at C5-C6 in FE, AR and LB (P<0.05). There was not any difference for non-operative level kinematics between MF group and FM group and intact spine. Compared with the intact spine, FF group led to a significant decrease at the arthrodesis-levels (P<0.05) and marked increase at the non-operative level kinematics.

CONCLUSION

A two-level Mobi-C and Hybrid construct generated better biomechanical conditions. This study suggested that two-level cervical total disc replacement or HS could become an alternative approach for therapy of two-level consecutive cervical spondylosis.

Metal-on-metal versus metal-on-plastic artificial discs in two-level anterior cervical disc replacement: a meta-analysis with follow-up of 5 years or more

BACKGROUND CONTEXT

Although highlighted in joint arthroplasty studies, long-term outcomes between differing biomaterial composites, such as metal-on-metal (MoM) and metal-on-plastic (MoP) in anterior cervical disc replacement (ACDR) have not been thoroughly investigated.

PURPOSE

The purpose of this study was to evaluate the patient-reported clinical outcomes, overall reoperation rates, complications, and rates of ASD of MoM versus MoP artificial discs in two-level ACDR for the treatment of cervical DDD.

STUDY DESIGN/SETTING

Meta-analysis and systematic review.

PATIENT SAMPLE

Nine hundred eighty patients (442 MoM, 538 MoP) across seven studies.

OUTCOME MEASURES

Patient reported clinical outcomes (NDI, VAS-n, VAS-a), overall reoperation rates, complications, and rates of ASD.

METHODS

A systematic search strategy of three electronic databases (PubMed, CINAHL Plus, and SCOPUS) was conducted utilizing terms related to two-level ACDR. All studies included had a sample size of >10 patients, had a minimum 5-year follow-up, and reported data on adjacent segment disease. Cadaver studies, non-English manuscripts, articles with less than 5-year follow-up and studies in which only single-level ACDR was investigated were excluded. A total of seven studies were included in this analysis. Studies were analyzed for demographic data, clinical outcome scores (NDI, VAS-neck, and VAS-arm), overall reoperation rates, complications, and rates of ASD. A random-effects model of meta-analysis was used for groups that were determined to be heterogenous and a fixed-effects model was utilized for groups that were not. An overlap of 95% confidence intervals suggests no statistically significant difference at the p<.05 level.

RESULTS

Seven studies were included with data on 980 patients (442 MoM, 538 MoP). The study population was 52.84% female, with a mean age of 48.01 years, and a mean follow-up of 85.66 months. The mean improvement in NDI was 34.42 (95% CI, 32.49-36.36) and 29.72 (95% CI, 27.15-32.29) for the MoM and MoP groups, respectively. The mean improvement in VAS-neck was 11.20 (95% CI, 10.69-11.70) and 8.78 (95% CI, 7.81-9.74) for the MoM and MoP groups, respectively. The mean improvement in VAS-arm was 10.73 (95% CI, 9.83-11.63) and 8.49 (95% CI, 7.59-9.39) for the MoM and MoP groups, respectively. 3.85% (95% CI, 2.40-6.10) of patients who underwent ACDR with a MoM implant required reoperation compared to 5.33% (95% CI, 3.68-7.65) of patients with a MoP implant. Heterotopic ossification and dysphagia were the most common complications in both groups. The MoM cohort showed a higher incidence of HO (72.62% vs. 21.07%), but a lower incidence of dysphagia (0.96% vs. 16.31%) compared to the MoP cohort. The MoM cohort had a larger proportion of patients with ASD who underwent subsequent surgery at an adjacent level (7.89% MoM versus 1.91% MoP).

CONCLUSIONS

Our present meta-analysis suggests that the use of MoM artificial discs in two-level ACDR results in superior clinical outcome score improvement, but higher rates of ASD requiring secondary surgery compared to MoP discs after a follow-up period of 5 years or more.

Cervical Total Disc Replacement: Indications and Technique

Cervical total disc replacement devices have been marketed in the United States (US) since 2007, with abundant level 1 evidence published on the treatment. Adherence to the strict inclusion/exclusion criteria and the surgical technique training of the US clinical trials remains the consistent and conservative approach to patient selection and implantation technique. However, patient selection and surgical technique remain debated among US surgeons as the published data and available cervical total disc replacements continue to grow.

Cervical disc arthroplasty for Klippel-Feil syndrome

OBJECTIVE

Klippel-Feil syndrome (KFS) is a congenital musculoskeletal condition characterized by improper segmentation of the cervical spine. This study aimed to evaluate outcomes of KFS patients who underwent cervical disc arthroplasty (CDA).

METHODS

Consecutive patients who underwent anterior cervical surgery were retrospectively reviewed. Those patients with KFS who received discectomy adjacent to the congenitally fused vertebral segments were extracted and grouped into either the fusion or the CDA group. Clinical and radiological evaluations included visual analog scales, Neck Disability Index (NDI), Japanese Orthopedic Association (JOA) scores, C2-7 range of motion (ROM), C2-7 Cobb angle, C2-7 sagittal vertical axis (SVA), and T1-slope.

RESULTS

Among 2320 patients, there were 41 with KFS (prevalence = 1.77%), who were younger than the entire cohort (53.3 vs 56.4 years). Thirty KFS patients had adjacent discs and were grouped into the CDA and fusion groups (14 vs 16). Type-I KFS with C3-4 involvement was the most common for both groups (92.8% vs 81.2% with 57% vs 50%, respectively). Post-operation, both groups demonstrated improvement of all the patient reported outcomes. The C2-7 ROM significantly decreased in the fusion group than that of pre-operation (12.8 ± 6° vs 28.1 ± 11.5°). In contrast, the CDA group successfully preserved C2-7 and segmental ROM without additional complications.

CONCLUSIONS

KFS is rare (prevalence = 1.77%) among cervical spine surgery patients, and it rarely affects the overall cervical spinal alignment, except that it decreases segmental mobility. CDA is a feasible option for KFS because it not only avoids long-segment fusion but also preserves segmental and global mobility.