Reoperations Following Cervical Disc Replacement

Primary Cervical Disc Arthroplasty Among Medicare Beneficiaries Versus Alternative Payers: Is It Time to Consider Nationwide Coverage?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

As of 2022, the Centers for Medicare and Medicaid Services does not provide nationwide coverage for cervical disc arthroplasty (CDA). The aim was to determine whether Medicare beneficiaries have differences in: (1) lengths of stay (LOS); (2) complications; (3) readmissions; and (4) costs of care.

METHODS

Using the 2010 to 2020 PearlDiver database, we queried patients undergoing primary CDA for degenerative disc pathology. Study groups patients were those undergoing CDA with Medicare coverage (n = 1467); patients without Medicare coverage were the comparison cohort (n = 15,389). Endpoints were to compare demographics and comorbidities within the Elixhauser comorbidity index (ECI), LOS, 90-day complications, 90-day readmissions, and 90-day reimbursements. A multivariate logistic regression was used to calculate odds (OR) of medical complications and readmissions within 90-days. A P-value less than .003 was significant.

RESULTS

Patients with Medicare coverage undergoing CDA had higher mean ECI compared to alternative payers (5.24 vs 3.26; P < .0001). Mean LOS was significantly higher for Medicare beneficiaries (2.20 vs 1.76 days; P < .010). There was no significant differences in odds of all medical complications (OR: 1.19, 95% CI: .98-1.44; P = .069) or readmission rates (1.77% vs 1.33%, OR:0.82, 95% CI: .50-1.29; P = .417) within 90-days following the index procedure among Medicare beneficiaries vs alternative payers. Non-Medicare beneficiaries had higher 90-day reimbursements compared to Medicare beneficiaries ($6,700 vs $7,086,P < .001).

CONCLUSIONS

Medicare beneficiaries despite having slightly longer lengths of stay did not have higher rates of medical complications or readmissions. Surgeons and policy makers may use this data to consider alternative treatments in Medicare patients.

The Top 100 Cited Articles on Cervical Disc Arthroplasty: A Bibliometric Analysis

STUDY DESIGN

Bibliometric analysis.

OBJECTIVE

Cervical disc arthroplasty (CDA) has emerged as an effective surgical intervention for degenerative cervical disc disease with potential advantages over traditional cervical fusion. This bibliometric analysis aimed to assess the current state of research on CDA by analyzing the relevant literature using bibliometric indicators.

SUMMARY OF BACKGROUND DATA

Web of Science Core Collection.

METHODS

A comprehensive search was conducted using the Web of Science database, for articles related to CDA published in the last 19 years. The top 100 articles were reviewed using bibliometric analysis. Publication trends, citation patterns, authorship, and collaboration networks were analyzed using VOSviewer and the Bibliometrix package in RStudio.

RESULTS

The results revealed a significant increase in the number of publications related to CDA over the past 2 decades, with most of the articles being published in orthopedic and spine surgery journals. The most frequently cited articles were related to clinical outcomes, complications, and biomechanical studies of CDA. Co-authorship analysis identified influential authors and collaborative networks, highlighting the multidisciplinary nature of CDA research involving neurosurgeons, orthopedic surgeons, and engineers. Overall, this bibliometric analysis provides a comprehensive overview of the current state of research on CDA, highlighting the key research themes, influential authors, and collaborative networks in the field.

CONCLUSION

These findings can serve as a guide for researchers, clinicians, and policymakers to identify knowledge gaps, research trends, and future directions in the field of CDA.

Delayed Infection After Cervical Disc Arthroplasty: A Case Report and Review of the Literature

STUDY DESIGN

Case report and literature review.

OBJECTIVE

To report the relatively rare complication of delayed infection after cervical disc arthroplasty (CDA).

BACKGROUND

Delayed infection of the M6 device has been a rarely reported complication, with all cases described outside of the United States. The reliability of positive intraoperative cultures remains an ongoing debate.

METHODS

Cases were reviewed, and findings were summarized. A literature review was performed and discussed, with special consideration to current reports of delayed M6 infection, etiology, and utility of intraoperative cultures.

RESULTS

We present a case of delayed infection 6 years after primary 1-level CDA with the M6 device. At revision surgery, gross purulence was encountered. Intraoperative cultures finalized with Staphylococcus epidermidis and Cutibacterium acnes. The patient was revised with removal of the M6 and conversion to anterior cervical discectomy and fusion. A prolonged course of intravenous antibiotics was followed by an oral course for suppression. At the final follow-up, the patient's preoperative symptoms had resolved.

CONCLUSION

Delayed infection after CDA is a rare complication, with ongoing debate regarding the reliability of positive cultures. We describe an infected M6 and demonstrate the utility of implant removal, conversion to anterior cervical discectomy and fusion, and long-term antibiotics as definitive treatment.

LEVEL OF EVIDENCE

Level V-case report and literature review.

Anterior cervical discectomy and fusion versus cervical disc arthroplasty: an epidemiological review of 433,660 surgical patients from 2011 to 2021

BACKGROUND CONTEXT

Anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) are commonly performed operations to address cervical radiculopathy and myelopathy. Trends in utilization and revision surgery rates warrant investigation.

PURPOSE

To explore the epidemiology, postoperative complications, and reoperation rates of ACDF and CDA DESIGN: Retrospective cohort study.

PATIENT SAMPLE

A total of 433,660 patients who underwent ACDF or CDA between 2011 and 2021 were included in this study.

OUTCOME MEASURES

The following data were observed for all cases: patient demographics, complications, and revisions.

METHODS

The PearlDiver database was queried to identify patients who underwent ACDF and CDA between 2011 and 2021. Epidemiological analyses were performed to examine trends in cervical procedure utilization by age group and year. After matching by age, sex, Charlson Comorbidity Index (CCI), levels of operation, and reason for surgery, the early postoperative (2-week), short-term (2-year), and long-term (5-year) complications of both cervical procedures were examined.

RESULTS

In total, 404,195 ACDF and 29,465 CDA patients were included. ACDF utilization rose by 25.25% between 2011 and 2014 while CDA utilization rose by 654.24% between 2011-2019 followed by relative plateauing in both procedures. Mann-Kendall trend test confirmed a significant but small rise in ACDF and large rise in CDA procedures from 2011 to 2021 (p<.001). After matching, ACDF and CDA had an overall complication rate of 12.20% and 8.77%, respectively, with the most common complications being subsequent anterior revision (4.96% and 3.35%) and dysphagia (3.70% and 2.98%). The ACDF cohort, especially multilevel ACDF patients, generally had more complications and higher revision rates than the CDA cohort (p<.05).

CONCLUSIONS

While ACDF utilization has plateaued since 2014, CDA rates have risen by a staggering 654.24% over the past decade. ACDF and CDA complication and revision rates were relatively low in comparison to previously published values, with significantly lower rates in CDA. Although a lack of radiographic data in this study limits its power to recommend either procedure for individual patients with cervical radiculopathy or myelopathy, CDA may be associated with minor improvement in the complication and revision profile.

Risk Factors for Reoperation Following Single-Level Cervical Disc Arthroplasty as Utilized in a Representative Sample of United States Clinical Practice: A Retrospective PearlDiver Study

STUDY DESIGN

Retrospective Cohort.

OBJECTIVES

Most data regarding cervical disc arthroplasty (CDA) outcomes are from highly controlled clinical trials with strict inclusion/exclusion criteria. This study aimed to identify risk factors for CDA reoperation, in "real world" clinical practice using a national insurance claims database.

METHODS

The PearlDiver database was queried for patients (2010-2020) who underwent a subsequent cervical procedure following a single-level CDA. Patients with less than 2 years follow-up were excluded. Primary outcome was to evaluate risk factors for reoperation. Secondary outcome was to evaluate the types of reoperations. Risk factors were compared using descriptive statistics. Multivariate regression analyses were used to ascertain the association among risk factors and reoperation.

RESULTS

Of 14,202 patients who met inclusion criteria, 916 (6.5%) underwent reoperation. Patients undergoing reoperation were slightly older with higher Elixhauser Comorbidity Index (ECI) scores, however both were not risk factors for reoperation. Patients with diagnoses such as smoking, myelopathy, inflammatory disorders, spinal deformity, trauma, or a history of prior cervical surgery were at greater risk for reoperation. No association was found between the year of index surgery and reoperation risk. The most common reoperation procedure was cervical fusion.

CONCLUSIONS

As billed for in the United States since 2010, CDA was associated with a 6.5% reoperation rate over a mean follow-up time of 5.3 years. Smoking, myelopathy, inflammatory disorders, spinal deformity, and a history of prior cervical surgery or trauma are risk factors for reoperation following CDA. Though patients who underwent a reoperation were older, age was not found to be an independent risk factor for a subsequent procedure.

Revision Strategies for Cervical Disc Arthroplasty

STUDY DESIGN

Narrative review.

OBJECTIVE

To review indications and strategies for revision of cervical disc arthroplasty (CDA).

SUMMARY OF BACKGROUND DATA

No data were generated as part of this review.

METHODS

A narrative review of the literature was performed.

RESULTS

No results were generated as part of this review.

CONCLUSIONS

CDA is a proven, motion-sparing surgical option for the treatment of myelopathy or radiculopathy secondary to cervical degenerative disc disease. As is the case with any operation, a small percentage of CDA will require revision, which can be a technically demanding endeavor. Here we review available revision strategies and associated indications, a thorough understanding of which will aid the surgeon in finely tailoring their approach to varying presentations.

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.

Impact of Posterior Cervical Foraminotomy Before or After Cervical Disk Replacement: Current Evidence

STUDY DESIGN

Narrative review.

OBJECTIVES

The purpose of this study was to provide a review of the current evidence on the impact of posterior cervical foraminotomy (PCF) performed before or after cervical disk replacement (CDR).

SUMMARY OF BACKGROUND DATA

The impact of PCF on outcomes in the setting of CDR is an evolving field, given the recent widespread adoption of CDR and the relative rarity of patients who have undergone both procedures.

METHODS

A literature search was conducted using PubMed to determine current evidence regarding the indications, outcomes, and biomechanical effects of CDR and PCF when performed alone or in combination.

RESULTS

When radicular symptoms persist following PCF, a CDR can be safely performed to provide further decompression. Conversely, a PCF can be safely performed following CDR for these same indications. The biomechanical effects of these procedures in combination demonstrate maintained stability when the facetectomy is less than 50% of the facet joint. Studies demonstrate that stability is not significantly decreased by the presence, amount, or level of posterior foraminotomies in the setting of CDR.

CONCLUSIONS

A PCF can be safely performed before or after cervical disk arthroplasty for recurrent radicular symptoms.

LEVEL OF EVIDENCE

Level V.

Level-specific Perioperative and Clinical Outcome Comparison: Cervical Disk Replacement Versus Anterior Cervical Diskectomy and Fusion at C5-C6 in Patients With Myeloradiculopathy

INTRODUCTION

This study compares perioperative and postoperative clinical outcomes in patients undergoing anterior cervical diskectomy and fusion (ACDF) or cervical disk replacement (CDR) at C5-C6 in patients with myeloradiculopathy.

METHODS

Primary, elective, single-level CDR or ACDF procedures at C5-C6 for patients with myeloradiculopathy were included. Patient-reported outcome measures (PROMs) included visual analog scale (VAS) neck, VAS arm, Neck Disability Index (NDI), Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS-PF), and Short-Form 12-Item Physical Composite Score (SF-12 PCS) collected at preoperative/6-week/12-week/6-month/1-year time points. Surgical cohorts were assessed for differences in demographics/perioperative characteristics using the chi square test and unpaired Student t-test for categorical and continuous variables, respectively. Achievement of minimum clinically important difference (MCID) was determined by comparing ΔPROMs with established thresholds. Outcome measures were compared at postoperative time points with the Student t-test, and improvement from preoperative baseline was assessed with a paired sample t-test.

RESULTS

One hundred thirty-seven patients were included, 43 CDR and 94 ACDF. CDR patients demonstrated significantly reduced surgical times (46.3 versus 55.1 minutes), estimated blood loss (24.4 versus 43.6 mL), revision surgery rates (0.0% versus 5.3%), postoperative length of stay (8.9 versus 23.0 hours), and postoperative narcotic consumption (P < 0.017, all). Complication rates and mean PROMs did not differ between cohorts. The CDR cohort markedly improved from baseline for all PROMs postoperatively except SF-12 PCS/PROMIS-PF at 6 weeks. The ACDF cohort markedly improved at each time point except VAS arm at 1 year, NDI at 6 weeks/1 year, and SF-12 PCS/PROMIS-PF at 6 weeks. A majority of both cohorts achieved overall MCID for VAS neck/NDI/PROMIS-PF. MCID achievement rates did not differ except NDI at 12 weeks/1 year and SF-12 PCS at 6 months, both favoring CDR.

DISCUSSION

Both procedural cohorts demonstrated similar long-term clinical outcomes for arm/neck pain and physical function; however, patients undergoing CDR at C5-C6 demonstrated an improved ability to maintain 1-year postoperative progress for neck disability with improved 1-year NDI MCID achievement. The CDR cohort, in addition, demonstrated an improved perioperative profile and reduced rate of revision surgery.

Factors Associated with Postoperative Rehospitalization in Patients with Cervical Disc Herniation

Cervical disc herniation (CDH) is a prevalent disease because of the poor living habits of and great pressure in modern society. Patients experience hand numbness, neck stiffness, soreness, and weakness due to neck nerve root compression, which leads to a gradual increase of neurosurgery outpatients. Although poor posture by the overuse of computers is possibly the origin of CDH, analysis of related factors causing the rehospitalization for CDH patients after surgery in Taiwan is not commonly reported. Thus, the present study focused on the demographics and surgery-related treatment on the relevance of rehospitalization for CDH patients after surgery. The design of the study was retrospective, and we collected data by medical record review, which was derived from the inpatient surgery data of patients at a medical center in southern Taiwan. The study lasted two years from 1 January 2017 to 31 December 2018, and a total of 248 patients underwent surgery for intervertebral disc protrusion in the neck. The retrospective study adopted narrative statistics, the chi-squared test, and binary logistic regression analysis to identify factors affecting postoperative rehospitalization. Among 248 postoperative patients with intervertebral disc protrusion, 178 underwent cervical fusion surgery, and 32 were rehospitalized after surgery for one-year follow up, accounting for an overall prevalence rate of 12.9%. There were no significant differences in sex, age, occupation, hypertension, anterior cervical discectomy and fusion, artificial disc replacement, hybrid surgery, and postoperative cervical coil use (p > 0.05). The results of binary logistic regression analysis showed statistically significant differences in abnormal body mass index (p = 0.0187, 95% CI = 1.238-10.499), diabetes (p = 0.0137, 95% CI = 1.288-9.224) and cervical vertebral surgery hospital days (p = 0.0004, 95% CI = 1.028-1.102), predicting the outcome of rehospitalization for CDH patients after surgery. The above results showed that abnormal body mass index, diabetes, and cervical vertebral surgery hospitalization days impacted rehospitalization in CDH patients after surgery. Thus, to prevent diabetes, weight control must be monitored, and maintaining correct posture can reduce CDH and decrease the rate of rehospitalization after surgery, which provides a critical reference for hospital managers and clinical staff.

Radiological Changes in Adjacent and Index Levels after Cervical Disc Arthroplasty

PURPOSE

The purpose of this retrospective study was to evaluate radiological and clinical outcomes in patients undergoing cervical disc arthroplasty (CDA) for cervical degenerative disc disease. The results may assist in surgical decision-making and enable more effective and safer implementation of cervical arthroplasty.

MATERIALS AND METHODS

A total of 125 patients who were treated with CDA between 2006 and 2019 were assessed. Radiological measurements and clinical outcomes included the visual analogue scale (VAS), the Neck Disability Index (NDI), and the Japanese Orthopaedic Association (JOA) myelopathy score assessment preoperatively and at ≥2 years of follow-up.

RESULTS

The mean follow-up period was 38 months (range, 25-114 months). Radiographic data demonstrated mobility at both the index and adjacent levels, with no signs of hypermobility at an adjacent level. There was a non-significant loss of cervical global motion and range of motion (ROM) of the functional spinal unit at the operated level, as well as the upper and lower adjacent disc levels, compared to preoperative status. The cervical global and segmental angle significantly increased. Postoperative neck VAS, NDI, and JOA scores showed meaningful improvements after one- and two-level CDA. We experienced a 29.60% incidence of heterotrophic ossification and a 3.20% reoperation rate due to cervical instability, implant subsidence, or osteolysis.

CONCLUSION

CDA is an effective surgical technique for optimizing clinical outcomes and radiological results. In particular, the preservation of cervical ROM with an artificial prosthesis at adjacent and index levels and improvement in cervical global alignment could reduce revision rates due to adjacent segment degeneration.

Cervical disc arthroplasty: What we know in 2020 and a literature review

Cervical disc arthroplasty (CDA) is a safe and effective option to improve clinical outcomes (e.g., NDI, VAS, and JOA) in degenerative cervical disc disease and compressive myelopathy. CDA's two main purported benefits have been that it maintains physiologic motion and thereby minimizes the biomechanical stresses placed on adjacent segments as compared to an ACDF. CDA might reduce the degeneration of adjacent segments, and the need for adjacent-level surgery. Reoperation rates of CDA have been reported to range from 1.8% to 5.4%, with a minimum 5-year follow-up. As the number of CDA procedures performed continues to increase, the need for revision surgery is also likely to increase. When performed skillfully in appropriate patients, CDA is an effective surgical technique to optimize clinical outcomes and radiological results. This review may assist surgical decision-making and enable a more effective and safer implementation of cervical arthroplasty for cervical degenerative disease.

Revision Surgeries at the Index Level After Cervical Disc Arthroplasty - A Systematic Review

Objective

To perform a systematic literature review on revision surgeries at the index level after cervical disc arthroplasty (CDA) failure.

Methods

A systematic literature review was performed according to the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. Prospective studies on patients who required a secondary surgery after CDA failure were included for analysis. The minimum follow-up for these studies was 5 years.

Results

Out of 864 studies in the original search group, a total of 20 studies were included. From a total of 4,087 patients, 161 patients required a reoperation at the index level. A total of 170 surgeries were performed, as some patients required multiple surgeries. The most common secondary procedures were anterior cervical discectomy and fusion (ACDF) (68%, N = 61) and posterior cervical fusion (15.5%, N = 14), followed by other reoperation (13.3%, N = 12). The associated outcomes for those who required a revision surgery were rarely mentioned in the included literature.

Conclusion

The long-term revision rate at the index level of failed CDA surgery was 3.9%, with a minimum 5-year follow-up. ACDF was the most commonly performed procedure to salvage a failed CDA. Some patients who required a new surgery after CDA failure may require a more extensive salvage procedure and even subsequent surgeries.

Revision Surgery for a Failed Artificial Disc

PURPOSE

This study aimed to present our experience with failures in C-TDR and revision surgery outcomes.

MATERIALS AND METHODS

We retrospectively examined patients who underwent revision surgery due to the failure of C-TDR between May 2005 to March 2019. Thirteen patients (8 males and 5 females) were included in this study. The mean age was 46.1 years (range: 22-61 years), and the average follow-up period was 19.5 months (range: 12-64 months). The outcome measures of pre- and post-operative neck and arm pain using a visual analogue scale (VAS) and functional impairment were assessed using a modified Japanese Orthopedic Association (JOA) scale and the Neck Disability Index (NDI).

RESULTS

The main complaints of patients were posterior neck pain (77%), radiculopathy (62%), and/or myelopathy (62%). The causes of failure of C-TDR were improper indications for the procedure, osteolysis and mobile implant use, inappropriate techniques, and postoperative infection. The most common surgical level was C5-6, followed by C4-5. After revision surgery, the neck and arm pain VAS (preoperative vs. postoperative: 5.46 vs. 1.31; 4.86 vs. 1.08), a modified JOA scale (14.46 vs. 16.69), and the NDI (29.77 vs. 9.31) scores were much improved.

CONCLUSION

C-TDR is good surgical option. However, it is very important to adhere to strict surgical indications and contraindications to avoid failure of C-TDR. The results of reoperations were good regardless of the approach. Therefore, various reoperation options could be considered in patients with failed C-TDR.

Early Catastrophic Failure of Cervical Disc Arthroplasty: A Case Report

CASE

A 47-year-old healthy man underwent cervical disc arthroplasty (CDA) for a C6 radiculopathy. Two-week radiographs showed a well-positioned implant. At the 6-week postoperative visit, the inferior portion of the implant had displaced ventrally, with C6 anterior vertebral body collapse. The next day, the implant was removed and converted to a C5/6 anterior cervical discectomy and fusion. Bone biopsy was unremarkable.

CONCLUSIONS

This is the first reported case of early catastrophic failure of a well-positioned CDA in a healthy patient with good bone quality. Possible contributing mechanisms include hypermobility and anterior bone loss, factors previously associated with CDA.

Late Implant Failure in Cervical Disc Arthroplasty (M6-C, Spinal Kinetics) Causing Radiculopathy and Myelopathy

Cervical disc arthroplasty (CDA) is an approved surgical treatment option in selected patients with cervical spinal disc degeneration. Even though CDA is a standard procedure since 20 years, there is a lack of information about long term performance. The published reoperation rates after CDA are low and comparable to anterior cervical fusion. The authors describe a severe failure and dysfunction with a partial core dislocation of a cervical prosthesis into the spinal canal (M6-C, Spinal Kinetics, Sunnyvale, CA, USA). Six years after implantation of a cTDR (cervical Total Disk Replacement) of the M6 type at C4/5 level, a 52 year-old women presented herself with new clinical signs of cervical myelopathy and radicular pain. Complete posterior dislocation of the central core of the implant into the spinal canal was identified as a cause. The failed device was removed completely and an ACCF (anterior cervical corpectomy and fusion) was performed. Intraoperatively, rupture of the posterior portion of the mesh tissue with posterior dislocation of the whole prosthesis core was detected. This is the second described case of a severe implant failure with core dislocation in this type of cTDR device. Even though there are thousands of successful implantations and middle term outcomes, it seems to be necessary to continue with long term radiological follow up to exclude similar failure in this type of prosthesis.

Patient Selection in Cervical Disc Arthroplasty

BACKGROUND

Patient selection for cervical disc arthroplasty (CDA) in the United States remains a topic of debate among surgeons. Many surgeons base US patient selection for CDA implantation on the Food and Drug Administration (FDA) indications/contraindications. While off-label use does occur, the frequency and extent of off-label use in the US remains largely unknown. Outside the United States, patient selection is notably less stringent; however such data also remain largely unpublished or presented/published with a low level of evidence. Here, we will review the current approved US on-label patient selection criteria for CDA and discuss the rationale and supporting evidence to expand these criteria in the United States.

METHODS

A PubMed literature search was completed using the keywords "cervical disc arthroplasty" and "cervical disc replacement." The articles were evaluated by the authors for patient selection criteria.

CONCLUSIONS

The current published data do not conclusively prove that the patients excluded from CDA by strict adherence to FDA indications would benefit from CDA surgery over anterior cervical discectomy and fusion. As surgeons, it is a difficult decision regarding when to expand indications to include off-label use of CDA. In our practice, generally CDA patient selection agrees with the FDA indications and contraindications, as there is a lack of level 1 evidence to confirm effectiveness of CDA outside of the current FDA indications. We will likely need more well-constructed studies to include prospective and controlled trials that specifically evaluate the "off-label" applications before US surgeons are convinced to expand indications and insurance companies agree to reimburse.

Mechanical failure of the Mobi-C implant for artificial cervical disc replacement: report of 4 cases

Cervical spondylosis is one of the most commonly treated conditions in neurosurgery. Increasingly, cervical disc replacement (CDR) has become an alternative to traditional arthrodesis, particularly when treating younger patients. Thus, surgeons continue to gain a greater understanding of short- and long-term complications of arthroplasty. Here, the authors present a series of 4 patients initially treated with Mobi-C artificial disc implants who developed postoperative neck pain. Dynamic imaging revealed segmental kyphosis at the level of the implant. All implants were locked in the flexion position, and all patients required reoperation. This is the first reported case series of symptomatic segmental kyphosis after CDR.

M6-C cervical disc replacement failure associated with late onset infection

Cervical disc replacements are commonly used to treat degenerative disc disease. We present a case an M6-C disc replacement failure associated with Propionibacterium acnes infection three years post implantation.

Cervical Disc Replacement

Anterior cervical disc replacement (arthroplasty) has gained momentum over the past 2 decades. The ball-and-socket prosthesis design of arthroplasty has been shown to simulate normal motion in all 3 rotation planes at the level of surgery and replicates physiologic motion. Anterior cervical discectomy and fusion has been shown to be a safe and effective surgery over decades; cervical disc replacement counters some secondary effects owing to its preservation of segmental mobility, the potential to reduce adjacent segment degeneration, and the lack of plating or harvesting bone graft. The literature is growing in support of the success and longevity of arthroplasty.

A Comparative in vivo Study of Semi-constrained and Unconstrained Cervical Artificial Disc Prostheses

PURPOSE

The objective of this study is to directly compare different types of cervical artificial disc implants using an in vivo model capable of simulating the axial load on a neck that is similar to the human neck.

METHODS

Cervical arthroplasty was performed at C3-4 in 14 healthy female adult Alpine goats. The goats were divided into three groups. Group A received Bryan (unconstrained one-piece design); Group B received ProDisc-C (semi-constrained two-piece design); and Group C received Mobi-C (unconstrained three-piece design) artificial discs. The goats were monitored in a veterinary unit for 6 months with radiography at regular intervals.

RESULTS

Each goat tolerated cervical arthroplasty well and had satisfactory placement of their implant per intra-operative radiography. Implants monitored in Group A demonstrated no migration. One out of five implants in Group B experienced anterior migration at 3 months. In Group C, anterior migration and disintegration occurred in all four implants, with migration occurring during the first postoperative week in three implants and after 5 weeks in the fourth.

CONCLUSIONS

Unconstrained multi-piece artificial cervical discs may be prone to anterior migration and extrusion out of the disc space. This outcome deserves attention in individuals with a hypermobile neck and/or an occupation involving the use of a head-supported mass, such as helmets.

Anterior Bone Loss in Cervical Disc Arthroplasty

Study Design

Retrospective, longitudinal observational study.

Purpose

To describe the natural history of anterior bone loss (ABL) in cervical disc arthroplasty (CDA) and introduce a classification system for its assessment.

Overview of Literature

ABL has recently been recognized as a complication of CDA, but its cause and clinical effects remain unknown.

Methods

Patients with non-keeled CDA (146) were retrospectively reviewed. X-rays were examined at 6 weeks, 3, 6, 9, 12, 18, and 24 months, and annually thereafter for a minimum of 5 years. These were compared with the initial postoperative X-rays to determine the ABL. Visual Analog Scale pain scores were recorded at 3 months and 5 years. Neck Disability Index was recorded at postoperative 5 years. The natural history was determined and a classification system was introduced.

Results

Complete radiological assessment was available for 114 patients with 156 cervical disc replacements (CDRs) and 309 endplates (average age, 45.3 years; minimum, 28 years; maximum, 65 years; 57% females). ABL occurred in 57.1% of CDRs (45.5% mild, 8.3% moderate, and 3.2% severe) and commenced within 3 months of the operation and followed a benign course, with improvement in the bone stock after initial bone resorption. There was no relationship between ABL degree and pain or functional outcome, and no implants were revised.

Conclusions

ABL is common (57.1%). It occurs at an early stage (within 3 months) and typically follows a non-progressive natural history with stable radiographic features after the first year. Most ABL cases are mild, but severe ABL occurs in approximately 3% of CDAs. ABL does not affect the patients’ clinical outcome or the requirement for revision surgery. Surgeons should thus treat patients undergoing CDA considering ABL.

Trends in cervical disc arthroplasty and revisions in the Medicare database

Background

Due to increased postoperative complications with anterior cervical discectomy and fusion (ACDF), there has been an increasing interest in the use of cervical disc arthroplasty (CDA). Advancements in prosthetic designs and techniques have improved patient reported outcome measurements and minimized revision rates. There is a paucity in the literature regarding recent trends in CDA utilization and revision rates. The purpose of this study was to determine annual primary and revision CDA trends with the use of an administrative database.

Methods

A retrospective review from 2005-2014 was performed using the Medicare Standard Analytical Files from the PearlDiver supercomputer (PearlDiver Technologies, Fort Wayne, IN, USA). Patients who underwent primary CDA were queried using International Classification of Disease, ninth revision (ICD-9) and current procedural terminology (CPT) code 84.62 and 22856, respectively. Revision CDAs were queried using ICD-9 procedure code 84.66. Primary outcomes of this study included annual primary procedures, annual revision incidence (RI), and additional demographic data such as age, gender, geographic location, Charlson-Comorbidity Index (CCI); in addition to length of stay (LOS), cost, and reimbursement.

Results

The query returned 2,016 and 517 primary CDA and revision CDA procedures were performed in the Medicare database, respectively. The data showed that the CAGR of primary and revision CDA procedures to be 20.54% and 5.84% (P<0.001), respectively. RI and RB demonstrated a CAGR of -12.22% and -9.61%, respectively. Patients younger than the age of 65 represented the majority of the patients undergoing this procedure. Demographically, primary and revision CDAs were found highest in the South.

Conclusions

The data demonstrates a high rate of annual growth in CDA utilization (20.54%) and revision CDA (5.84%), indicating there is an increase demand for CDA in the United States. Compared to ACDF, patients who undergo CDA have improved patient reported outcome measurements and lower rates of postoperative complications.

Anterior Techniques in Managing Cervical Disc Disease

Surgical treatment may be indicated for select patients with cervical disc disease, whether it is cervical disc herniation or spondylosis due to degenerative changes, acute cervical injury due to trauma, or other underlying cervical pathology. Currently, there are various surgical techniques, including anterior, posterior, or combined approaches, in addition to new interventions being utilized in practice. Ideally, the surgical approach should be selected in consideration of each patient’s clinical presentation, imaging findings, and overall medical comorbidities on an individual basis. But the unique advantages and disadvantages of each surgical technique often complicate the therapy choice in managing cervical disc diseases. Although anterior cervical discectomy and fusion (ACDF) is the most widely accepted procedure performed for both single and multi-level cervical disc diseases, there are multiple modifications to this technique. Surgeons have access to different types of plates, screws, and cages and can adopt newer advances in the field such as stand-alone and minimally invasive techniques when indicated. In short, no consensus exists in terms of a single approach that is preferred for all patients. This article aims to review the standard of care for management of cervical disc disease with a focus on the surgical techniques and, in particular, the anterior approach, exploring the various surgical options within this technique.

Risk factors for anterior bone loss in cervical disc arthroplasty

OBJECTIVE The objective of this study was to identify the risk factors of anterior bone loss (ABL) in cervical disc arthroplasty (CDA) and the subsequent effect of this phenomenon. METHODS The authors performed a retrospective radiological review of 185 patients with a minimum 5-year follow-up after CDA (using Bryan, Discocerv, Mobi-C, or Baguera C). Postoperative radiographs were examined and compared to the initial postoperative films to determine the percentage of ABL. The relationship of ABL to potential risk factors was analyzed. RESULTS Complete radiological assessment was available in 145 patients with 193 CDRs and 383 endplates (average age 45 years, range 25-65 years, 54% women). ABL was identified in 63.7% of CDRs (48.7% mild, 11.9% moderate, 3.1% severe). Age (p = 0.770), sex (p = 0.200), postoperative alignment (p = 0.330), midflexion point (p = 0.509), maximal flexion (p = 0.080), and extension (p = 0.717) did not relate to ABL. There was no significant difference in the rate of severe ABL between implants. Multilevel surgery conferred an increased risk of any and severe ABL (p = 0.013 for both). The upper endplate, defined as superior to the CDA, was more commonly involved (p = 0.008), but there was no significant difference whether the endplate was between or not between implants (p = 0.226). The development of ABL did not affect the long-term range of movement (ROM) of the CDA, but did increase the overall risk of autofusion. ABL was not associated with pain or functional deficits. No patients required a reoperation or revision of their implant during the course of this study, and there were no cases of progressive ABL beyond the first year. CONCLUSIONS ABL is common in all implant types assessed, although most is mild. Age, sex, postoperative alignment, ROM, and midflexion point do not relate to this phenomenon. However, the greater the number of levels operated, the higher the risk of developing ABL. The development of ABL has no long-term effect on the mechanical functioning of the disc or necessity for revision surgery, although it may increase the rate of autofusion.

Differences of the Morphology of Subaxial Cervical Spine Endplates between Chinese and White Men and Women

Objective. The aim of this comparative anatomical study was to specifically investigate endplate morphology differences between Chinese and White men and women. Materials and Methods. Three-dimensional cervical endplate models were constructed using computed tomography imaging of 41 healthy Chinese and 24 White subjects. The morphologic measurements of cervical endplate included linear parameters (EPWu: upper endplate width; EPDu: upper endplate depth; EPWl: lower endplate width; and EPDl: lower endplate depth) and area parameters with a digital measuring system. Results. All linear parameters showed a constant increase from C3 to C7 except for EPDl in both the Chinese and the White subjects. An increase trend was observed on area parameters in both Chinese and White subjects. The ratio of EPWl/EPDl was smaller in Chinese females than in White females at C3, C4, and C6 levels (P < 0.05). The ratio of EPWl/EPDl was significantly different between the Chinese and White men at C4-5 levels (P < 0.05). Conclusions. Our data indicates that the morphology of subaxial cervical spine endplates between Chinese and White men and women is different in most of the linear and area parameters. This information could provide guidelines for the design of CDA implants and the improvement of surgical techniques.

Comparison between cervical disc arthroplasty and conservative treatment for patients with single level cervical radiculopathy at C5/6

BACKGROUND

Cervical radiculopathy is a common disease that affects millions of people. Patients usually are managed by conservative therapy and surgical treatments.

OBJECTIVE

To compare the clinical outcomes between cervical disc arthroplasty (CDA) and conservative management for patients with single level cervical radiculopathy at C5/6.

METHODS

Seventy-two patients with cervical radiculopathy that only affect C5/6 joints were included and thirty-two of them received CDA surgery, and forty patients were treated with conservative management. All the patients were followed up around 4 years. Cervical curvature, cervical range of motion (CROM), horizontal displacement of cervical spine, and intervertebral gap were measured by radiological examination.

RESULTS

All the patients have comparable disease severity based on pre-surgical radiological assessments. At the 4-year follow-up examination, patients with CDA surgery had less CROM at C5/6 level, while greater CROM at C4/5 level, than control group. Similarly, the horizontal displacement in CDA group decreased at C5/6 vertebrae, and increased at C4/5 level at the 4-year follow-up examination. The intervertebral gaps of patients in CDA group were larger than control group at one-year and last follow-up examination.

CONCLUSION

CDA surgery stabilized C5/6 vertebrae and increased the CROM and horizontal displacement of upper adjacent C4/5 vertebrae.

Revision surgeries following artificial disc replacement of cervical spine

Objective

We investigated causes and results of revision surgeries after artificial disc replacement of cervical spine (C-ADR).

Methods

Twenty-one patients (mean age: 52.8) who underwent revision surgery after C-ADR and who had a minimum 2-year of follow-up were included into this study. The mean time between the primary and revision surgeries was 21 months. During their primary surgeries, 14 patients underwent single level C-ADR, 2 two-level C-ADR, and 5 two-level hybrid surgery for 16 radiculopathy, 3 myelopathy, and 2 adjacent segment diseases. Causes for revision surgeries were at least one of the followings: 17 poor patient selections, 7 insufficient decompressions, 7 malpositions, 6 subsidences, 3 osteolysis, and 1 postoperative infection.

Results

Sixteen patients underwent anterior removal of C-ADR, one-level discectomy and fusion (N = 11), two-level discectomy (N = 3) or one-level corpectomy (N = 2) and fusion. Three patients of keel type C-ADR with heterotopic ossification underwent posterior laminoforaminotomy and fusion. Two patients underwent combined procedures due to infection or severe subsidence and osteolysis. At the 2-year follow-up, neck (7.3 vs 1.6) and arm (7.0 vs 1.3) visual analog scales and Neck Disability Index score (46.7 vs 16.32) were improved (all, p < 0.05). According to Odom's criteria, 86% of the patients were satisfied and 91% achieved solid fusion. No major complications developed except for transient dysphagia in 6 patients (29%).

Conclusions

In this small case series, revision surgeries provided successful outcomes in failed C-ADR without major complications. Careful patient selection and meticulous surgical techniques are important to avoid disappointing clinical outcome or even failure of C-ADR.

Level of evidence

Level IV, Therapeutic study.

A new cervical artificial disc prosthesis based on physiological curvature of end plate: a finite element analysis

STUDY DESIGN

The study aimed to build a new cervical artificial disc C3-C7 segment prosthesis, and perform a biomechanical comparison between the new prosthesis and the Prestige LP prosthesis using a three-dimensional non-linear finite element (FE) model.

PURPOSE

The study compared the biomechanical differences between the new cervical artificial disc prosthesis based on the physiological curvature of the end plate and the Prestige LP prosthesis after artificial disc replacement.

BACKGROUND CONTEXT

There has been no prior research on artificial disc prostheses based on the physiological curvature of the end plate; studies of biomechanical changes after cervical disc arthroplasty (CDR) are few.

METHODS

An FE model of the C3-C7 segments was developed and validated. A new cervical artificial disc prosthesis based on the physiological curvature of the end plate and the Prestige LP prosthesis were integrated at the C5-C6 segment into the validated FE model. All models were subjected to a follower load of 73.6 N and a 1 Nm in flexion-extension, lateral bending, and axial torsion. The segmental range of motion (ROM) and stress on the prostheses were analyzed.

RESULTS

The ROM in most segments after CDR with new cervical artificial disc prosthesis was more similar to that of the normal cervical spine than the Prestige LP prosthesis. However, there was no significant difference between the two prostheses. The stress on the new artificial disc was significantly less than that in the Prestige LP prosthesis.

CONCLUSIONS

There was no significant difference in ROM in all segments after CDR for the two prostheses. The stress on the new cervical artificial disc prosthesis based on the physiological curvature of the end plate was significantly less than that in the Prestige LP prosthesis. The new artificial disc prosthesis is feasible and effective, and can reduce the implant-bone interface stress on the end plate, which may be one of the causes of prosthesis subsidence.

Revision surgery for cervical artificial disc: Surgical technique and clinical results

OBJECTIVE

Cervical artificial disc replacement (C-ADR) was developed with the goal of preserving mobility of the cervical segment in patients with degenerative disc disease. So far, little is known about experiences with revision surgery and explantation of C-ADRs. Here, we report our experience with revision the third generation, Galileo-type disc prosthesis from a retrospective study of two institutions.

PATIENTS AND METHODS

Between November 2008 and July 2016, 16 patients with prior implantation of C-ADR underwent removal of the Galileo-type disc prosthesis (Signus, Medizintechnik, Germany) due to a call back by industry. In 10 patients C-ADR was replaced with an alternative prosthesis, 6 patients received an ACDF. Duration of surgery, time to revision, surgical procedure, complication rate, neurological status, histological findings and outcome were examined in two institutions.

RESULTS

The C-ADR was successfully revised in all patients. Surgery was performed through the same anterior approach as the initial access. Duration of the procedure varied between 43 and 80min. Access-related complications included irritation of the recurrent nerve in one patient and mal-positioning of the C-ADR in another patient. Follow up revealed two patients with permanent mild/moderate neurologic deficits, NDI (neck disability index) ranged between 10 and 42%.

CONCLUSIONS

Anterior exposure of the cervical spine for explantation and revision of C-ADR performed through the initial approach has an overall complication rate of 18.75%. Replacements of the Galileo-type disc prosthesis with an alternative prosthesis or conversion to ACDF are both suitable surgical options without significant difference in outcome.