Artificial cervical disc arthroplasty: a systematic review

Anterior Cervical Decompression and Fusion for Neck Pain in Patients with Cervical Spondylosis: Pooled Results of Three Prospective Cohort Studies

INTRODUCTION

Currently, there is a lack of large-scale prospective cohort data to explore the response of neck pain to anterior cervical decompression and fusion (ACDF). The aim of this study was to investigate whether patients with neck pain can achieve consistent neck pain relief following ACDF regardless of preoperative neurological symptoms and number of surgical segments.

MATERIALS AND METHODS

The study was a pooled analysis of 3 multicenter prospective cohort studies. Patients with cervical radiculopathy and/or myelopathy with significant neck pain (visual analog scale [VAS] ≥ 4) who underwent ACDF were included. Neck pain VAS scores (VAS-neck) were collected at preoperative and postoperative follow-up time points (3 months, 6 months, and 1 year). Subgroup analyses were conducted for patients with radiculopathy, myelopathy, or myeloradiculopathy, as well as for single- versus multi-segment ACDF.

RESULTS

A total of 237 patients were confirmed. Patients showed significant improvement in VAS-neck at all follow-up time points compared with baseline (P < 0.001 for each). In the first year after surgery, VAS-neck were reduced by 3.3 points (57.0%) on average, and the rates of achieving minimum clinically important difference and patient acceptable symptom state were 72.2% and 73.8%, respectively. Meanwhile, one year after surgery, there was no significant difference in ΔVAS-neck, recovery rate, minimum clinically important difference, and patient acceptable symptom state attainment rate between the radiculopathy, myelopathy and myeloradiculopathy groups, and the same trend was observed between the single-segment and multi-segment groups.

CONCLUSIONS

This study found that ACDF significantly improved neck pain in patients with cervical spondylosis, regardless of preoperative neurological symptoms and number of surgical segments.

Hybrid Implants in Anterior Cervical Spine Surgery: The State of the Art and New Trends for Multilevel Degenerative Disc Disease

BACKGROUND

Anterior cervical discectomy and fusion (ACDF) still represents the first surgical option in the treatment of cervical degenerative disc disease (DDD) but is still burdened by several complications secondary to the loss of mobility at the treated segment and adjacent segment diseases (ASDs). To overcome those complications, hybrid surgery (HS) incorporating ACDF and cervical disc arthroplasty (CDA) is increasingly performed for DDD.

METHODS

We retrospectively reviewed the clinical, surgical, and outcome data of 85 consecutive patients (M/F, 41/44) harboring cervical disc herniation with or without osteophytes, with radiculopathy and with or without myelopathy, who underwent the anterior approach to a cervical discectomy on two or more levels with at least one disc prosthesis, along with a cage and plate or an O Profile screwed plate.

RESULTS

All the patients improved regardless of the cervical construct used. No significant relationship between different kinds of prosthesis and their surgical level; the number of cages; and the site of the cages (screwed and/or plated) was found concerning immediate stability, dynamic prosthesis effectiveness, and clinical improvement in all the patients up to the maximum follow-up time.

CONCLUSIONS

Although the optimal surgical technique for cervical DDD remains controversial, HS represents a safe and effective procedure in select patients with multilevel cervical DDD, as demonstrated by biomechanical and clinical studies and the present series.

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.

Outcomes of cervical disc replacement in patients with neck pain greater than arm pain

BACKGROUND CONTEXT

Although anterior cervical discectomy and fusion is believed to positively impact a patient's radicular symptoms as well as axial neck pain, the outcomes of cervical disc replacement (CDR) with regards to neck pain specifically have not been established.

PURPOSE

Primary: to assess clinical improvement following CDR in patients with neck pain greater than arm pain. Secondary: to compare the clinical outcomes between patients undergoing CDR for predominant neck pain (pNP), predominant arm pain (pAP), and equal neck and arm pain (ENAP).

STUDY DESIGN

Retrospective review of prospectively collected data.

PATIENT SAMPLE

Patients who had undergone one- or two-level CDR for the treatment of degenerative cervical pathology and had a minimum of 6-month follow-up were included and stratified into three cohorts based on their predominant location of pain: pNP, pAP, and ENAP.

OUTCOME MEASURES

Patient-reported outcomes: Neck Disability Index (NDI), Visual Analog Scale (VAS) neck and arm, Short Form 12-Item Physical Health Score (SF12-PHS), Short Form 12-Item Mental Health Score (SF12-MHS), minimal clinically important difference (MCID).

METHODS

Changes in Patient-reported outcomes from preoperative values to early (<6 months) and late (≥6 months) postoperative timepoints were analyzed within each of the three groups. The percentage of patients achieving MCID was also evaluated.

RESULTS

One hundred twenty-five patients (52 pNP, 30 pAP, 43 ENAP) were included. The pNP cohort demonstrated significant improvements in early and late NDI and VAS-Neck, early SF-12 MCS, and late SF-12 PCS. The pAP and ENAP cohorts demonstrated significant improvements in all PROMs, including NDI, VAS-Neck, VAS-Arm, SF-12 PCS, and SF-12 MCS, at both the early and late timepoints. No statistically significant differences were found in the MCID achievement rates for NDI, VAS-Neck, SF-12 PCS, and SF-12 MCS at the late timepoint amongst the three groups.

CONCLUSIONS

CDR leads to comparable improvement in neck pain and disability in patients presenting with neck pain greater than arm pain and meeting specific clinical and radiographic criteria.

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.

Early Experiences of One-Level Total Disc Replacement (Prestige LP) in Japan: A Comparison of Short-Term Outcomes with Anterior Cervical Discectomy with Fusion

Introduction

In Japan, cervical total disc replacement (TDR) was approved in 2017. However, because of its short history, no comparative study between cervical TDR and anterior cervical discectomy with fusion (ACDF) has been conducted in the country. Therefore, we examined and compared the surgical outcomes of TDR and ACDF for one-level cervical degenerative diseases.

Methods

In total, 50 patients who had received anterior surgeries for one-level cervical degenerative diseases were investigated. Among them, 25 underwent TDR (Prestige LP; Medtronic), whereas the other 25 patients underwent ACDF. ACDF samples were selected from cases conducted before the approval of TDR (-2017.9) and were retrospectively judged to be indicated for TDR. Before and at 1 year after surgery, clinical and radiological outcomes were evaluated.

Results

No significant differences in terms of patient demographics between the two groups were observed. A longer operative time was observed in the TDR group than in the ACDF group. Postoperatively, no differences in the Japanese Orthopaedic Association score for cervical myelopathy (C-JOA) score, neck pain visual analog scale, C2-7 angle, and C2-7 range of motion (ROM) were determined. TDR tended to show better neck disability index (NDI) scores postoperatively when compared with ACDF. The local angle at operative level was larger in ACDF. In TDR, the local ROMs were maintained postoperatively; however, in ACDF, the local ROM at the operative level was decreased, and the local ROMs at adjacent levels were increased postoperatively. In the TDR group, although heterotopic ossification was observed in 11 patients (44.0%), and anterior bone loss was identified in 14 patients (56.0%), these issues did not affect surgical outcomes.

Conclusions

Conclusively, no differences in terms of C-JOA score and neck pain between patients treated through TDR and ACDF were observed. However, a trend of better NDI scores was identified with TDR. While TDR maintained postoperative ROMs, ACDF showed an increase in the local ROMs at adjacent levels.

Quality assessment of systematic reviews of surgical treatment of cervical spine degenerative diseases: an overview

OBJECTIVE

To gather all systematic reviews of surgical treatment of degenerative cervical diseases and assess their quality, conclusions and outcomes.

METHODS

A literature search for systematic reviews of surgical treatment of degenerative cervical diseases was conducted. Studies should have at least one surgical procedure as an intervention. Included studies were assessed for quality through Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) and Assessment of Multiple Systematic Reviews (AMSTAR) questionnaires. Quality of studies was rated accordingly to their final score as very poor (<30%), poor (30%-50%), fair (50%-70%), good (70%-90%), and excellent (>90%). If an article reported a conclusion addressing its primary objective with supportive statistical evidence for it, they were deemed to have an evidence-based conclusion.

RESULTS

A total of 65 systematic reviews were included. According to AMSTAR and PRISMA, 1.5% to 6.2% of studies were rated as excellent, while good studies counted for 21.5% to 47.7%. According to AMSTAR, most studies were of fair quality (46.2%), and 6.2% of very poor quality. Mean PRISMA score was 70.2%, meaning studies of good quality. For both tools, performing a meta-analysis significantly increased studies scores and quality. Cervical spondylosis studies reached highest scores among diseases analyzed. Authors stated conclusions for interventions compared in 70.7% of studies, and only two of them were not supported by statistical evidence.

CONCLUSION

Systematic reviews of surgical treatment of cervical degenerative diseases present "fair" to "good" quality in their majority, and most of the reported conclusions are supported by statistical evidence. Including a meta-analysis significantly increases the quality of a systematic review.

Hybrid implants in anterior cervical decompressive surgery for degenerative disease

Background:

Anterior cervical discectomy and fusion (ACDF) still represent the mainstream surgical approach in the treatment of degenerative cervical Degenerative Disc Disease (DDD), being a loss of mobility at the treated segment and adjacent segment diseases well-known complications. To overcome those complications, hybrid surgery (HS) incorporating ACDF and cervical disk arthroplasty is increasingly performed for DDD.

Methods:

We retrospectively reviewed the clinical, surgical, and outcome data of 62 consecutive patients (male/female, 29/37) harboring cervical disk herniation with or without osteophytes, with radiculopathy with or without myelopathy, who underwent a cervical discectomy on two or more levels with the anterior approach with at least one disk prosthesis along with cage and plate or O Profile screwed plate.

Results:

All the patients improved regardless of the cervical construct used. No significant relationship between different kind of prostheses as well as their surgical level, the number and the site of the cages (screwed and/or plated) was found out concerning immediate stability, dynamic prosthesis effectiveness, and clinical improvement in all the patients up to the maximum follow-up.

Conclusions:

Although the optimal surgical technique for cervical DDD remains controversial, HS represents a safe and effective procedure in selected patients with multilevel cervical DDD, as demonstrated by biomechanical and clinical studies and the present series. Some technical aspects should be considered when dealing with this procedure, like the drilling of the endplate, and some radiological findings have to be detected because potentially predictive of future misplacement.

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.

Comparison between porous tantalum metal implants and autograft in anterior cervical discectomy and fusion: a meta-analysis

Aim: The objective of this study was to systematically compare the safety and efficacy of porous tantalum metal (TM) implants and autograft in single-level anterior cervical discectomy and fusion. Methods: Potential academic articles were acquired from the Cochrane Library, Medline, PubMed, Embase, Science Direct and other databases. The time range used was from the inception of the electronic databases to March 2018. Gray studies were identified from the references of included literature reports. STATA version 11.0 (Stata Corporation, TX, USA) was used to analyze the pooled data. Results: Four randomized, controlled trials (RCTs) were identified according to the retrieval process. There were significant differences in operation time (mean difference [MD]: -28.846, 95% confidence interval [CI: -47.087, -10.604], p = 0.002) and satisfaction rate (odds ratio [OR]: 2.196, 95% CI: [1.061-4. 546]; p = 0.034). However, no significant difference was detected in blood loss (MD: -73.606, 95% CI: [-217.720, 70.509], p = 0.317), hospital stay (MD: -0.512, 95% CI [-1.082, 0.058]; p = 0.079), fusion rate (OR: 0.497, 95% CI [0.079, 3.115]; p = 0.455), visual analog scale (MD: -0.310, 95% CI [-0.433, -0.186]; p < 0.001) or complication rate (risk difference [RD]: -0.140, 95% CI: [-0.378, 0.099]; p = 0.251). Conclusion: Porous TM implants are equally as effective and safe as autograft in anterior cervical discectomy and fusion processes. In addition, porous TM implants could reduce operation time and improve clinical satisfaction significantly.

Clinical presentation and outcome after anterior cervical discectomy and fusion for degenerative cervical disc disease

Background:

Anterior cervical discectomy and fusion (ACDF) is a well-described surgical approach for symptomatic degenerative cervical disc disease which does not respond to conservative management. In the present study, we assessed clinical presentation and outcomes of ACDF.

Materials and Methods:

The present study was conducted from October 1, 2015, to October 31, 2017, in the Department of Neurosurgery, Narayana Medical College and Hospital, Nellore, Andhra Pradesh, among 100 consecutive adult patients who underwent single- or two-level ACDF for degenerative cervical disc disease.

Results:

The mean age was 47.2 ± 12.8 years (range: 20–74 years). Majority of the patients were male (86/100). Presenting symptoms were neck pain (77%), limb weakness (73%), paresthesias (53%), radicular pain (49%), stiffness in limbs (16%), and bladder involvement (13%). Fusion was done with stand-alone titanium cage/bone graft or titanium cage/bone graft with anterior cervical plate. At the time of discharge, significant improvement in preoperative symptoms (neck pain [47/77-61%], radicular pain [31/49-63%], limb weakness [53/73-72.6%], paresthesias [44/53-83%], stiffness in limbs [13/16-81%], and bladder symptoms [8/13-61%]) was reported by majority of these patients. Majority of these patients also reported improvement in preoperative sensory deficits at the time of discharge. Postoperative complications were hoarseness of voice (22%), dysphagia (16%), deterioration of motor power (8%), and postoperative hematoma (7%).

Conclusions:

A significant proportion of patients with degenerative cervical disc disease show remarkable recovery after ACDF.

Cervical disc degeneration and neck pain

Cervical intervertebral disc has long been considered a common source of neck pain. However, the pain caused by the disc itself has not been clearly defined so far, and its diagnosis and treatment has always been controversial. Degenerative cervical disc has a rich supply of nerve fibers, is prone to inflammatory reactions, and is susceptible to pain that can be provoked by disc stimulation or distention, and can be eliminated by block. Overwhelming clinical evidence demonstrates that neck pain in patients with degenerative cervical radiculopathy or myelopathy can be subsided rapidly by anterior cervical surgery, further indicating that this neck pain stems from the pathology of cervical disc itself. Cervical discography is advocated as the only test that connects disease to symptoms, but the procedure remains controversial. If strict criteria and technique are maintained, discography can discriminate painful, symptomatic discs from nonpainful, asymptomatic discs. Discogenic neck pain alone without cervical disc herniation or cervical spondylosis accounts for a large proportion of chronic neck pain. For these patients who continue to have refractory neck pain and fail to respond to conservative treatment, anterior cervical fusion surgery or artificial cervical disc replacement may be a better choice, and preoperative cervical discography can guarantee the excellent surgical results. Existing basic and clinical studies have scientifically shown that cervical intervertebral disc degeneration can lead to neck pain.

Progressive Bone Formation After Cervical Disc Replacement: Minimum of 5-Year Follow-up

STUDY DESIGN

Retrospective review.

OBJECTIVE

Our objective was to examine the prevalence, clinical significance, ramifications, and possible etiology of postoperative bone formation at the index level after cervical disc replacement (CDR) with a minimum of 5 years of follow-up.

SUMMARY OF BACKGROUND DATA

CDR can be complicated by postoperative ossification and unwanted ankylosis at the index level, which some authors have termed "heterotopic ossification." This terminology may be inaccurate as it assumes the postoperative bone formation is unnatural and a consequence of the CDR surgery. We advocate that this phenomenon has more to do with individual patient factors rather than the surgery.

METHODS

Patients who underwent Bryan CDR for cervical myelopathy or radiculopathy between 12/2003 and 8/2008 with a minimum of 5-years follow-up were analyzed. They were divided into two groups, those with and without postoperative bone formation. Patient-reported outcomes (Japanese Orthopaedic Association score, Neck Disability Index, Visual Analogue Scale for neck and arm pain) and radiographic parameters were collected pre- and postoperatively and compared between groups.

RESULTS

Sixty-one patients (76 levels) were identified (mean follow-up 94.2 mo). The overall incidence of postoperative ossification was 50%. Both groups had sustained significant improvements across all patient-reported outcome measures at final follow-up. Notably, patients with more severe preoperative cervical spondylosis had higher rates of postoperative ossification (P = 0.036) and adjacent segment degeneration (P = 0.010).

CONCLUSION

Although the long-term incidence of postoperative bone formation after CDR was relatively high, this did not adversely affect patient outcomes. Patients with more severe preoperative spondylosis had higher rates of postoperative ossification, suggesting that postoperative ossification at the CDR segment is likely one of progressive bone formation in individuals already predisposed to forming bone rather than one of alleged heterotopic ossification as a consequence of the surgery.

LEVEL OF EVIDENCE

3.

Anterior cervical discectomy and fusion: review and update for radiologists

OBJECTIVES

The goals of this article are to describe the various types of interbody grafts and anterior cervical plating systems, techniques for optimizing evaluation of cervical spine metallic implants on CT and MR imaging, expected appearance and complications of ACDF on postoperative imaging and imaging assessment of fusion. Optimization for optimizing metal induced artifacts.

CONCLUSION

Currently, ACDF is the most commonly performed surgical procedure for degenerative cervical spine disease. Interbody fusion is performed with bone grafts or interbody spacers, and may be supplemented with anterior cervical plating. Compressive pathologies at the vertebral body level may be addressed by simultaneous corpectomy. Postoperatively, imaging plays an integral role in routine screening of asymptomatic individuals, fusion assessment and evaluation of complications.

An in vivo comparison study in goats for a novel motion-preserving cervical joint system

Cervical degenerative disease is one of the most common spinal disorders worldwide, especially in older people. Anterior cervical corpectomy and fusion (ACCF) is a useful method for the surgical treatment of multi-level cervical degenerative disease. Anterior cervical disc replacement (ACDR) is considered as an alternative surgical method. However, both methods have drawbacks, particularly the neck motion decrease observed after arthrodesis, and arthroplasty should only be performed on patients presenting with cervical disc disease but without any vertebral body disease. Therefore, we designed a non-fusion cervical joint system, namely an artificial cervical vertebra and intervertebral complex (ACVC), to provide a novel treatment for multi-level cervical degenerative disease. To enhance the long-term stability of ACVC, we applied a hydroxyapatite (HA) biocoating on the surface of the artificial joint. Thirty-two goats were randomly divided into four groups: a sham control group, an ACVC group, an ACVC-HA group, and an ACCF group (titanium and plate fixation group). We performed the prosthesis implantation in our previously established goat model. We compared the clinical, radiological, biomechanical, and histological outcomes among these four different groups for 24 weeks post surgery. The goats successfully tolerated the entire experimental procedure. The kinematics data for the ACVC and ACVC-HA groups were similar. The range of motion (ROM) in adjacent level increased after ACCF but was not altered after ACVC or ACVC-HA implantation. Compared with the control group, no significant difference was found in ROM and neutral zone (NZ) in flexion-extension or lateral bending for the ACVC and ACVC-HA groups, whereas the ROM and NZ in rotation were significantly greater. Compared with the ACCF group, the ROM and NZ significantly increased in all directions. Overall, stiffness was significantly decreased in the ACVC and ACVC-HA groups compared with the control group and the ACCF group. Similar results were found after a fatigue test of 5,000 repetitions of axial rotation. The histological results showed more new bone formation and better bone implant contact in the ACVC-HA group than the ACVC group. Goat is an excellent animal model for cervical spine biomechanical study. Compared with the intact state and the ACCF group, ACVC could provide immediate stability and preserve segmental movement after discectomy and corpectomy. Besides, HA biocoating provide a better bone ingrowth, which is essential for long-term stability. In conclusion, ACVC-HA brings new insight to treat cervical degenerative disease.

ProDisc-C Total Disc Replacement Versus Anterior Cervical Discectomy and Fusion for Single-Level Symptomatic Cervical Disc Disease: Seven-Year Follow-up of the Prospective Randomized U.S. Food and Drug Administration Investigational Device Exemption Study

BACKGROUND

In patients with single-level cervical degenerative disc disease, total disc arthroplasty can relieve radicular pain and preserve functional motion between two vertebrae. We compared the efficacy and safety of cervical total disc arthroplasty with that of anterior cervical discectomy and fusion (ACDF) for the treatment of single-level cervical degenerative disc disease between C3-C4 and C6-C7.

METHODS

Two hundred and nine patients at thirteen sites were randomly treated with either total disc arthroplasty with ProDisc-C (n = 103) or with ACDF (n = 106). Patients were assessed preoperatively; at six weeks and three, six, twelve, eighteen, and twenty-four months postoperatively; and then annually until seven years postoperatively. Outcome measures included the Neck Disability Index (NDI), the Short Form-36 (SF-36), postoperative neurologic parameters, secondary surgical procedures, adverse events, neck and arm pain, and satisfaction scores.

RESULTS

At seven years, the overall follow-up rate was 92% (152 of 165). There were no significant differences in demographic factors, follow-up rate, or patient-reported outcomes between groups. Both procedures were effective in reducing neck and arm pain and improving and maintaining function and health-related quality of life. Neurologic status was improved or maintained in 88% and 89% of the patients in the ProDisc-C and ACDF groups, respectively. After seven years of follow-up, thirty secondary surgical procedures had been performed in nineteen (18%) of 106 patients in the ACDF group compared with seven secondary surgical procedures in seven (7%) of 103 patients in the ProDisc-C group (p = 0.0099). There were no significant differences in the rates of any device-related adverse events between the groups.

CONCLUSIONS

Total disc arthroplasty with ProDisc-C is a safe and effective surgical treatment of single-level symptomatic cervical degenerative disc disease. Clinical outcomes after total disc arthroplasty with ProDisc-C were similar to those after ACDF. Patients treated with ProDisc-C had a lower probability of subsequent surgery, suggesting that total disc arthroplasty provides durable results and has the potential to slow the rate of adjacent-level disease.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Quality of systematic reviews: an example of studies comparing artificial disc replacement with fusion in the cervical spine

Cervical artificial disc replacement (C-ADR) is now an alternative to anterior cervical discectomy and fusion (ACDF). Many studies have evaluated the efficacy of C-ADR compared with ACDF. This led to a series of systematic reviews and meta-analyses to evaluate the evidence of the superiority of one intervention against the other. The aim of the study presented here was to evaluate the quality of these reviews and meta-analyses. Medline via Ovid, Embase, and Cochrane Library were searched using the keywords: (total disk replacement, prosthesis, implantation, discectomy, and arthroplasty) AND (cervical vertebrae, cervical spine, and spine) AND (systematic reviews, reviews, and meta-analysis). Screening and data extraction were conducted by two reviewers independently. Two reviewers then assessed the quality of the selected reviews and meta-analysis using 11-item AMSTAR score which is a validated measurement tool to assess the methodological quality of systematic reviews. Screening of full reports of 46 relevant abstracts resulted in the selection of 15 systematic reviews and/or meta-analyses as eligible for this study. The two reviewers' inter-rater agreement level was high as indicated by kappa of >0.72. The AMSTAR score of the reviews ranged from 3 to 11. Only one study (a Cochrane review) scored 100% (AMSTAR 11). Five studies scored below (AMSTAR 5) indicating low-quality reviews. The most significant drawbacks of reviews of a score below 5 were not using an extensive search strategy, failure to use the scientific quality of the included studies appropriately in formulating a conclusion, not assessing publication bias, and not reporting the excluded studies. With a significant exception of a Cochrane review, the methodological quality of systematic reviews evaluating the evidence of C-ADR versus ACDF has to be improved.

Factors that may affect outcome in cervical artificial disc replacement: a systematic review

PURPOSE

To identify the factors that may affect outcome in C-ADR and provide the pooled results of postoperative success rate of implanted segment range of motion (ROM), incidence of heterotopic ossification (HO), incidence of radiographic adjacent segment degeneration (r-ASD)/adjacent segment disease (ASD), and surgery rate for ASD.

METHODS

We systematically searched in PubMed, Embase, Cochrane library and Web of knowledge from 2001 to May 2015. Two independent reviewers screened the primary records. Eleven questions regarding the effect of patient selection issues and radiographic parameters issues on outcome were posed previously. Studies addressing the framed questions were included for analysis.

RESULTS

Twenty-two studies were included for the final analysis. Results showed that number of surgical level (single versus double-level) had no effect on primary clinical outcome and radiographic outcome, surgical level had no effect on clinical and radiographic outcome, and smoking habits had negative effect on clinical outcome. No evidence for the effect of patient's age and pathology category (radiculopathy or myelopathy) on outcome was found. The overall success rate of ROM was 79.4%. ROM of the implanted segment and cervical sagittal alignment had no effects on clinical outcome. The pooled incidences of grade 1-4 HO and grade 3-4 HO were 27.7 and 7.8%, respectively. The pooled incidence of r-ASD and surgery rate for ASD were 42.4 and 3.8%, respectively.

CONCLUSIONS

The available evidence showed that most of the pre-selected factors had no effect on outcome after C-ADR, and the ROM success rate, incidence of HO and r-ASD/ASD, and surgery rate for ASD are acceptable. There is a lack of evidence from RCTs for some factors.

Artificial disc and vertebra system: a novel motion preservation device for cervical spinal disease after vertebral corpectomy

OBJECTIVE

To determine the range of motion and stability of the human cadaveric cervical spine after the implantation of a novel artificial disc and vertebra system by comparing an intact group and a fusion group.

METHODS

Biomechanical tests were conducted on 18 human cadaveric cervical specimens. The range of motion and the stability index range of motion were measured to study the function and stability of the artificial disc and vertebra system of the intact group compared with the fusion group.

RESULTS

In all cases, the artificial disc and vertebra system maintained intervertebral motion and reestablished vertebral height at the operative level. After its implantation, there was no significant difference in the range of motion (ROM) of C(3-7) in all directions in the non-fusion group compared with the intact group (p>0.05), but significant differences were detected in flexion, extension and axial rotation compared with the fusion group (p<0.05). The ROM of adjacent segments (C(3-4), C(6-7)) of the non-fusion group decreased significantly in some directions compared with the fusion group (p<0.05). Significant differences in the C(4-6) ROM in some directions were detected between the non-fusion group and the intact group. In the fusion group, the C(4-6) ROM in all directions decreased significantly compared with the intact and non-fusion groups (p<0.01). The stability index ROM (SI-ROM) of some directions was negative in the non-fusion group, and a significant difference in SI-ROM was only found in the C(4-6) segment of the non-fusion group compared with the fusion group.

CONCLUSION

An artificial disc and vertebra system could restore vertebral height and preserve the dynamic function of the surgical area and could theoretically reduce the risk of adjacent segment degeneration compared with the anterior fusion procedure. However, our results should be considered with caution because of the low power of the study. The use of a larger sample should be considered in future studies.

WITHDRAWN: Arthroplasty versus fusion in single-level cervical degenerative disc disease

Background

There is ongoing debate about whether fusion or arthroplasty is superior in the treatment of single level cervical degenerative disc disease. Mainly because the intended advantage of arthroplasty over fusion, that is, the prevention of symptoms due to adjacent segment degeneration in the long term, is not confirmed yet. Until sufficient long‐term results become available, it is important to know whether results of one of the two treatments are superior to the other in the first one to two years.

Objectives

To assess the effects of arthroplasty versus fusion for radiculopathy or myelopathy, or both due to single level cervical degenerative disc disease.

Search methods

We searched the following databases for randomised controlled trials (RCTs): CENTRAL (The Cochrane Library 2011, Issue 2), MEDLINE, EMBASE, and EBMR. Additionally, we searched the System for Information on Grey Literature (SIGLE), subheading Biological and Medical Sciences, the US Food and Drug Administration (FDA) database on medical devices, and Clinicaltrials.gov to identify trials in progress. We also screened the reference list of all selected papers. Date of search: 25 May 2011.

Selection criteria

We included RCTs that directly compared any type of cervical fusion with any type of arthroplasty, with at least one year of follow‐up. Primary outcomes were arm pain, neck pain, neck‐related functional status, patient satisfaction, neurological outcome, and global health status. Secondary outcomes were the presence of (radiological) fusion, revision surgery at the treated level, secondary surgery on adjacent levels, segmental mobility of treated and adjacent levels, and work status.

Data collection and analysis

Study selection was performed independently by three review authors, and 'Risk of bias' assessment and data extraction were performed by two review authors. In case of missing data or insufficient information for a judgement about risk of bias, we tried to contact the study authors or the study sponsor. The data were entered into RevMan by one review author and subsequently checked by a second review author. We assessed the quality of evidence using GRADE. We analysed heterogeneity and performed sensitivity analyses for the pooled analyses.

Main results

We included nine studies (2400 participants), five of which had a low risk of bias. Eight of these studies were industry sponsored. The most important results showed low‐quality evidence for a small but significant difference in alleviation of arm pain at one to two years in favour of arthroplasty (mean difference (MD) ‐1.54; 95% confidence interval (CI) ‐2.86 to ‐0.22; 100‐point scale). A small study effect could not be ruled out for this outcome in the sensitivity analyses. This means that smaller studies (or small published subsets of larger studies) showed larger differences for this outcome, which may indicate publication bias. Also, moderate‐quality evidence showed a small difference in neck‐related functional status at one to two years in favour of arthroplasty (MD ‐2.79; 95% CI ‐4.73 to ‐0.85; 100‐point scale) and a small difference in neurological outcome in favour of arthroplasty (risk ratio (RR) 1.05; 95% CI 1.01 to 1.09). These two outcomes were robust to sensitivity analyses. For none of the primary outcomes, was a clinically relevant difference shown. Additionally, there was high‐quality evidence for a large, statistically significant difference in segmental mobility at one to two years (measured as degrees segmental range of motion) at the treated level (MD 6.90; 95% CI 5.45 to 8.35). There was low‐quality evidence that there was no statistically significant difference in secondary surgery at the adjacent levels at one to two years (RR 0.60; 95% CI 0.35 to 1.02). The latter was not robust to sensitivity analyses.

Authors' conclusions

There was a tendency for clinical results to be in favour of arthroplasty; often these were statistically significant. However, differences in effect size were invariably small and not clinically relevant for all primary outcomes. Significance was often gained or lost in the varying sensitivity analyses, probably owing to the relatively small number of studies, in combination with the small differences that were found. Given the fact that all of the included studies were not blinded, this could be due to patient or carer expectations. However, at this time both treatments can be seen as valid options with respect to results at a maximum of one to two years. Given the current absence of truly long‐term results, use of these mobile disc prostheses should still be limited to clinical trials. There was high‐quality evidence that the goal of preservation of segmental mobility in arthroplasty was met. A statistically significant effect on the incidence of secondary symptoms at adjacent levels, the primary goal of arthroplasty over fusion, was not found at one to two years. If there was a protective effect, this should become clearer over time. A future update, when studies with 'truly long‐term' results (five years or more) become available, should focus on this issue.

A herniated disc in the neck often causes radiating pain, numbness, and weakness in muscles of the neck, shoulders, arms, and hands. It may also lead to symptoms in the trunk and legs.

When there is no or insufficient relief of symptoms with non‐surgical treatment, surgery can be an option. Traditional 'fusion' surgery involves fusion of the two bones of the spine (the vertebrae) that form the disc space. Motion between these two vertebrae is then no longer possible.

It has been suggested that this may cause the adjacent parts of the spine to become more mobile, as compensation. This in turn might accelerate normal wear and tear in these parts of the spine, which could lead to new symptoms. At present this is not confirmed.

Mobile disc prostheses have been introduced in an effort to reduce the amount of new symptoms at the longer term after surgery by preserving motion between the vertebrae involved. Long‐term results are not available yet. However, it is important to know whether disc arthroplasty is at least as effective as fusion in relieving symptoms, the primary aim of surgery.

In this review we have searched for all studies in which the patient receives one of these two possible treatments at random.

We identified nine studies (2400 participants), and considered five of these to have high methodological quality. This review shows that patients who were treated with a mobile disc prosthesis had less pain radiating to the arm one to two years after surgery, and less disability owing to these complaints. However, the actual differences were very small, only between 1 and 5 points on a 100‐point scale. The overall quality of the evidence was low to moderate, which means that including new studies in future years could change these conclusions. The conclusion that mobility is in fact preserved after placement of a mobile disc prosthesis, compared to traditional 'fusion' surgery, is unlikely to change. Whether this preserved mobility will lead to fewer new symptoms in the future is uncertain based on results for the first one to two years after surgery.

Therefore, a comparison of results in the long term (five years or more) will be made when more studies with long‐term results have become available.

Using the modified Delphi method to establish a new Chinese clinical consensus of the treatments for cervical radiculopathy

PURPOSE

Although cervical radiculopathy is very common, there is no standard treatment for this condition, with little high-level evidence available to guide the treatment choice. Thus, this study aimed to review the current data on the management of cervical radiculopathy; and, further, to establish a new Chinese clinical consensus of the treatments for cervical radiculopathy using the Delphi method.

METHODS

First, a systematic review of the previously established treatment guidelines and of articles related to cervical radiculopathy was conducted to establish a protocol for the clinical consensus of the treatment for cervical radiculopathy. Second, from February 2012 to June 2014, we performed a modified Delphi survey in which the current professional opinions from 30 experienced experts, representing almost all of the Chinese provinces, were gathered. Three rounds were performed, and consensus was defined as ≥70% agreement.

RESULTS

Consensus of the treatments for cervical radiculopathy was reached on seven aspects, including the proportion of patients requiring only non-surgical therapies; the effectiveness of neck immobilization, physiotherapy, pharmacologic treatment; surgical indications; contraindications; surgery.

CONCLUSIONS

The modified Delphi study conducted herein reached a consensus concerning several treatment issues for cervical radiculopathy. In the absence of high-level evidence, at present, these expert opinion findings will help guide health care providers to define the appropriate treatment in their regions. Items with no consensus provide excellent areas for future research.

Multi-center, prospective, randomized, controlled investigational device exemption clinical trial comparing Mobi-C Cervical Artificial Disc to anterior discectomy and fusion in the treatment of symptomatic degenerative disc disease in the cervical spine

BACKGROUND

Anterior cervical discectomy and fusion (ACDF) is the gold standard for treating symptomatic cervical disc degeneration. Cervical total disc replacements (TDRs) have emerged as an alternative for some patients. The purpose of this study was to evaluate the safety and effectiveness of a new TDR device compared with ACDF for treating single-level cervical disc degeneration.

METHODS

This was a prospective, randomized, controlled, multicenter Food and Drug Administration (FDA) regulated Investigational Device Exemption (IDE) study. A total of 245 patients were treated (164 TDR: 81 ACDF). The primary outcome measure was overall success based on improvement in Neck Disability Index (NDI), no subsequent surgical interventions, and no adverse events (AEs) classified as major complications. Secondary outcome measures included SF-12, visual analog scale (VAS) assessing neck and arm pain, patient satisfaction, radiographic range of motion, and adjacent level degeneration. Patients were evaluated preoperatively and postoperatively at 6 weeks, 3, 6, 12, 18, and 24 months. The hypothesis was that the TDR success rate was non-inferior to ACDF at 24 months.

RESULTS

Overall success rates were 73.6% for TDR and 65.3% for ACDF, confirming non-inferiority (p < 0.0025). TDR demonstrated earlier improvements with significant differences in NDI scores at 6 weeks and 3 months, and VAS neck pain and SF-12 PCS scores at 6 weeks (p<0.05). Operative level range of motion in the TDR group was maintained throughout follow-up. Radiographic evidence of inferior adjacent segment degeneration was significantly greater with ACDF at 12 and 24 months (p < 0.05). AE rates were similar.

CONCLUSIONS

Mobi-C TDR is a safe and effective treatment for single-level disc degeneration, producing outcomes similar to ACDF with less adjacent segment degeneration.

LEVEL OF EVIDENCE

Level I.

CLINICAL RELEVANCE

This study adds to the literature supporting cervical TDR as a viable option to ACDF in appropriately selected patients with disc degeneration.

Solid radiographic fusion with a nonconstrained device 5 years after cervical arthroplasty

Cervical disc arthroplasty (CDA) has been gaining popularity as a surgical alternative to anterior cervical discectomy and fusion. Spontaneous fusion following a CDA is uncommon. A few anecdotal reports of heterotrophic ossification around the implant sites have been noted for the BRYAN, ProDisc-C, Mobi-C, PRESTIGE, and PCM devices. All CDA fusions reported to date have been in devices that are semiconstrained.

The authors reported the case of a 56-year-old man who presented with left C-7 radiculopathy and neck pain for 10 weeks after an assault injury. There was evidence of disc herniation at the C6–7 level. He was otherwise healthy with functional scores on the visual analog scale (VAS, 4.2); neck disability index (NDI, 16); and the 36-item short form health survey (SF-36; physical component summary [PSC] score 43 and mental component summary [MCS] score 47). The patient underwent total disc replacement in which the DISCOVER Artificial Cervical Disc (DePuy Spine, Inc.) was used. The patient was seen at regular follow-up visits up to 60 months. At his 60-month follow-up visit, he had complete radiographic fusion at the C6–7 level with bridging trabecular bone and no motion at the index site on dynamic imaging. He was pain free, with a VAS score of 0, NDI score of 0, and SF-36 PCS and MCS scores of 61 and 55, respectively.

Conclusions

This is the first case report that identifies the phenomenon of fusion around a nonconstrained cervical prosthesis. Despite this unwanted radiographic outcome, the patient's clinical outcome was excellent.

Anterior cervical disc replacement for degenerative disc disease

PURPOSE

To review the outcomes of anterior cervical disc replacement using the Prestige LP system for degenerative disc disease.

METHODS

Medical records of 12 men and 23 women aged 26 to 66 (mean, 46) years who underwent 48 anterior cervical disc replacements using the Prestige LP system by a single spine surgeon were reviewed. 22 patients underwent one-level disc replacement at C5-C6 (n=13) and C6-C7 (n=9), and 13 patients underwent 2-level disc replacement at C5-C6 and C6-C7 (n=11), C4-C5 and C5-C6 (n=1), and C6-C7 and C7-T1 (n=1). Neck Disability Index (NDI) score, visual analogue scale (VAS) for pain in the neck and arm, and physical and mental component scores of the Short Form 36 were evaluated at week 6 and months 6, 12, 24, 36, and 48.

RESULTS

The NDI score, VAS score for neck and arm pain, and physical and mental component scores of the Short Form 36 improved significantly after surgery (p<0.001). 80% of patients were satisfied with the treatment. One patient developed a neck haematoma on day 1 and underwent surgical evacuation. Another patient developed Horner's syndrome and achieved partial recovery at 6 weeks and complete recovery at 6 months. No patient had implant-related complications or reoperation.

CONCLUSION

The Prestige LP cervical disc implant was safe for one- and 2-level cervical disc replacement.

Cervical arthroplasty: a critical review of the literature

BACKGROUND CONTEXT

Cervical disc arthroplasty (CDA) is a motion-preserving procedure that is an alternative to fusion. Proponents of arthroplasty assert that it will maintain cervical motion and prevent or reduce adjacent segment degeneration. Accordingly, CDA, compared with fusion, would have the potential to improve clinical outcomes. Published studies have varying conclusions on whether CDA reduces complications and/or improves outcomes. As many of these previous studies have been funded by CDA manufacturers, we wanted to ascertain whether there was a greater likelihood for these studies to report positive results.

PURPOSE

To critically assess the available literature on cervical arthroplasty with a focus on the time of publication and conflict of interest (COI).

STUDY DESIGN/SETTING

Review of the literature.

METHODS

All clinical articles about CDA published in English through August 1, 2013 were identified on Medline. Any article that presented CDA clinical results was included. Study design, sample size, type of disc, length of follow-up, use of statistical analysis, quality-of-life (QOL) outcome scores, COI, and complications were recorded. A meta-analysis was conducted stratifying studies by COI and publication date to identify differences in complication rates reported.

RESULTS

Seventy-four studies were included that investigated 8 types of disc prosthesis and 22 met the criteria for a randomized controlled trial (RCT). All Level Ib RCTs reported superior quality-of-life outcomes for CDA versus anterior cervical discectomy and fusion (ACDF) at 24 months. Fifty of the 74 articles (68%) had a disclosure section, including all Level Ib RCTs, which had significant COIs related to the respective studies. Those studies without a COI reported mean weighted average adjacent segment disease rates of 6.3% with CDA and 6.2% with ACDF. In contrast, the reverse was reported by studies with a COI, for which the averages were 2.5% with CDA and 6.3% with ACDF. Those studies with a COI (n=31) had an overall weighted average heterotopic ossification rate of 22%, whereas those studies with no COI (n=43) had a rate of 46%.

CONCLUSIONS

Associated COIs did not influence QOL outcomes. Conflicts of interest were more likely to be present in studies published after 2008, and those with a COI reported greater adjacent segment disease rates for ACDF than CDA. In addition, heterotopic ossification rates were much lower in studies with COI versus those without COI. Thus, COIs did not affect QOL outcomes but were associated with lower complication rates.

Hybrid surgery for multilevel cervical degenerative disc diseases: a systematic review of biomechanical and clinical evidence

PURPOSE

The optimal surgical technique for multilevel cervical degenerative disc diseases (DDD) remains controversial. Hybrid surgery (HS) incorporating anterior cervical discectomy and fusion (ACDF) and cervical disc replacement (CDR) is increasingly performed for cervical DDD. This study aims to evaluate the biomechanical and clinical evidence available for HS and to provide a systematic review of current understanding of HS.

METHODS

This systematic review was undertaken by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement. Multiple databases and online registers of clinical trials were searched up to February 2014. The biomechanical and clinical studies on HS for cervical DDD written in English were included. Two authors independently assessed methodological quality and extracted data.

RESULTS

Fifteen studies including eight biomechanical studies and seven clinical studies were indentified. The biomechanical studies showed that HS was benefit to motion preservation of the operative levels and revealed less adverse effect on adjacent segments. All clinical studies demonstrated improvement in validated functional scores after HS. Segment motion and immobilization were achieved at the arthroplasty level and arthrodesis level, respectively. Postoperative assessments and complication rate were similar or in favor of HS when comparing with ACDF or CDR. However, the overall quality of evidence for HS was low to very low.

CONCLUSIONS

There is a paucity of high quality evidence for HS. HS may be a safe and efficacious technique to benefit a select group of multilevel cervical DDD, which is needed to be confirmed by further prospective, randomized controlled trials.

Clinical comparison of 2 implantation systems for single-level cervical disk replacement

The safety and effectiveness of 2 implantation systems for single-segment cervical disk replacement-the Bryan Cervical Disc System (Medtronic Inc, Minneapolis, Minnesota) and the ACCEL system (Medtronic Inc)-have not been clinically compared. A prospective, nonrandomized controlled study in consecutive patients with a minimum 2-year follow-up was performed. Fifty patients with single-level cervical disk degeneration who responded poorly to conservative treatment and underwent Bryan Cervical Disc replacement were involved. Fifty patients were included (24 in group A [Bryan Cervical Disc System] and 26 in group B [ACCEL system]).The patients' visual analog scale scores, Neck Disability Index (NDI) scores, Short Form 36 (SF-36) scores, Odom scores, operative time, blood loss, and complications were compared. Patients' baseline statuses were similar (P>.05). Visual analog scale for neck and arm pain, NDI, and SF-36 were significantly improved postoperatively (P<.05) in both groups, and no clinical differences were found between the groups (P>.05). All Odom scores were better than good. Mean operative time and average blood loss in group A (173±42.5 minutes and 250±159.8 mL, respectively), were both significantly higher than the values in group B (137.5±19.3 minutes and 138.1±86.7 mL, respectively) (P<.05). Complications included intraoperative bleeding, temporary throat discomfort, and slight migration of the prosthesis; there was no significant difference in the total complication rates between the 2 groups (P>.05). The 2 implantation systems displayed equal clinical effectiveness and safety, but the ACCEL system appears to have the advantages of shorter operative time and less blood loss.

Cervical disc arthroplasty: a critical review and appraisal of the latest available evidence

Anterior cervical discectomy and fusion (ACDF) has been a very successful procedure in the management of cervical radiculopathy and myelopathy. Concerns with adjacent segment disease and the desire to preserve physiological motion have led to technological and clinical efforts for cervical disc arthroplasty. The suggested move to cervical disc replacement has led to this latter procedure being one of the most scrutinised surgical treatments in the twenty-first century. Short- and medium-term prospective randomised clinical trials and systematic reviews show cervical disc replacement to be at least as good as ACDF as regards the clinical outcomes in the management of degenerative cervical spondylosis. This is logical since the neural decompression procedure is essentially the same. However, the rationale for arthroplasty over arthrodesis has been built on two main proposed roles: the preservation of segmental motion and the prevention of adjacent segment disease. Whilst results thus far show that this first role seems to be achieved, its clinical significance is as yet unproven; the second is so far not proven. In addition, the long-term fate of the implants is also unknown. Long-term safety and efficacy, therefore, still await further clinical studies.

Past, present, and future of cervical arthroplasty

Cervical arthroplasty was developed in an attempt to maintain cervical motion and potentially to avoid or minimize adjacent-segment degeneration. If cervical arthroplasty is successful, the long-term results of surgery for cervical disc disease should improve. However, problems associated with cervical arthroplasty have been reported: these include kyphosis, heterotopic ossification-induced motion limitation, no motion preservation even at the index level, and a higher revision rate in a limited number of cases compared with anterior cervical discectomy and fusion (ACDF). In addition, for degenerative cervical disc disorders, the risk of developing adjacent segment degeneration more than 2 years after surgery is reportedly similar for ACDF and cervical arthroplasty. Cervical disc arthroplasty is an emerging motion-sparing technology and is currently undergoing evaluation in many countries as an alternative to arthrodesis for the treatment of cervical radiculopathy and myelopathy. The decision whether to use arthrodesis or arthroplasty is a difficult one. The achievement of good prosthetic performance demands exacting implantation techniques to ensure correct placement. This fact underlines the increasing importance of special instrumentation and surgical skills that involve an understanding of prosthetic lubrication, wear, and biologic effects and familiarity with currently available information regarding kinematics, basic science, testing, and early clinical results. Fortunately, a number of devices are at the late preclinical study stage or at the early clinical trial stage, and results in many cases are promising. In the near future, it is likely that new designs will be produced to replace spinal discs totally or partially in a pathologic entity-specific manner.

Arthroplasty versus fusion in single-level cervical degenerative disc disease: a Cochrane review

STUDY DESIGN

A systematic review of randomized controlled trials (RCTs).

OBJECTIVE

To assess the effects of arthroplasty versus fusion in the treatment of radiculopathy or myelopathy, or both, due to single-level cervical degenerative disc disease.

SUMMARY OF BACKGROUND DATA

There is ongoing debate about whether fusion or arthroplasty is superior in the treatment of single-level cervical degenerative disc disease. Mainly because the intended advantage of arthroplasty compared with fusion, prevention of symptoms due to adjacent segment degeneration in the long term, is not confirmed yet. Until sufficient long-term results become available, it is important to know whether results of 1 of the 2 treatments are superior to the other in the first 1 to 2 years.

METHODS

We searched electronic databases for randomized controlled trials. We included randomized controlled trials that directly compared any type of cervical fusion with any type of cervical arthroplasty, with at least 1 year of follow-up. Study selection was performed independently by 3 review authors, and "risk of bias" assessment and data extraction were independently performed by 2 review authors. In case of missing data, we contacted the study authors or the study sponsor. We assessed the quality of evidence.

RESULTS

Nine studies (2400 participants) were included in this review; 5 of these studies had a low risk of bias. Results for the arthroplasty group were better than the fusion group for all primary comparisons, often statistically significant. For none of the primary outcomes was a clinically relevant difference in effect size shown. Quality of the evidence was low to moderate.

CONCLUSION

There is low to moderate quality evidence that results are consistently in favor of arthroplasty, often statistically significant. However, differences in effect size were invariably small and not clinically relevant for all primary outcomes.

LEVEL OF EVIDENCE

1.

Is cervical disc arthroplasty superior to fusion for treatment of symptomatic cervical disc disease? A meta-analysis

BACKGROUND

As the current standard treatment for symptomatic cervical disc disease, anterior cervical decompression and fusion may result in progressive degeneration or disease of the adjacent segments. Cervical disc arthroplasty was theoretically designed to be an ideal substitute for fusion by preserving motion at the operative level and delaying adjacent level degeneration. However, it remains unclear whether arthroplasty achieves that aim.

QUESTIONS/PURPOSES

We investigated whether cervical disc arthroplasty was associated with (1) better function (neck disability index, pain assessment, SF-36 mental and physical health surveys, neurologic status) than fusion, (2) a lower incidence of reoperation and major complications, and (3) a lower risk of subsequent adjacent segment degeneration.

METHODS

We conducted a comprehensive search in MEDLINE(®), EMBASE, and Cochrane Central Register of Controlled Trials and identified 503 papers. Of these, we identified 13 reports from 10 randomized controlled trials involving 2227 patients. We performed a meta-analysis of functional scores, rates of reoperation, and major complications. The strength of evidence was evaluated by using GRADE profiler software. Of the 10 trials, six trials including five prospective multicenter FDA-regulated studies were sponsored by industry. The mean follow-ups of the 10 trials ranged from 1 to 5 years.

RESULTS

Compared with anterior cervical decompression and fusion, cervical disc arthroplasty had better mean neck disability indexes (95% CI, -0.25 to -0.02), neurologic status (risk ratio [RR], 1.04; 95% CI, 1.00-1.08), with a reduced incidence of reoperation related to the index surgery (RR, 0.42; 95% CI, 0.22-0.79), and major surgical complications (RR, 0.45; 95% CI, 0.27-0.75) at a mean of 1 to 3 years. However, the operation rate at adjacent levels after two procedures was similar (95% CI, 0.31-1.27). The three studies with longer mean follow-ups of 4 to 5 years also showed similar superiority of all four parameters of cervical disc arthroplasty compared with fusion.

CONCLUSIONS

For treating symptomatic cervical disc disease, cervical disc arthroplasty appears to provide better function, a lower incidence of reoperation related to index surgery at 1 to 5 years, and lower major complication rates compared with fusion. However, cervical disc arthroplasty did not reduce the reoperation rate attributable to adjacent segment degeneration than fusion. Further, it is unclear whether these differences in subsequent surgery including arthroplasty revisions will persist beyond 5 years.

Arthroplasty versus fusion in single-level cervical degenerative disc disease

BACKGROUND

There is ongoing debate about whether fusion or arthroplasty is superior in the treatment of single level cervical degenerative disc disease. Mainly because the intended advantage of arthroplasty over fusion, that is, the prevention of symptoms due to adjacent segment degeneration in the long term, is not confirmed yet. Until sufficient long-term results become available, it is important to know whether results of one of the two treatments are superior to the other in the first one to two years.

OBJECTIVES

To assess the effects of arthroplasty versus fusion for radiculopathy or myelopathy, or both due to single level cervical degenerative disc disease.

SEARCH METHODS

We searched the following databases for randomised controlled trials (RCTs): CENTRAL (The Cochrane Library 2011, Issue 2), MEDLINE, EMBASE, and EBMR. Additionally, we searched the System for Information on Grey Literature (SIGLE), subheading Biological and Medical Sciences, the US Food and Drug Administration (FDA) database on medical devices, and Clinicaltrials.gov to identify trials in progress. We also screened the reference list of all selected papers. Date of search: 25 May 2011.

SELECTION CRITERIA

We included RCTs that directly compared any type of cervical fusion with any type of arthroplasty, with at least one year of follow-up. Primary outcomes were arm pain, neck pain, neck-related functional status, patient satisfaction, neurological outcome, and global health status. Secondary outcomes were the presence of (radiological) fusion, revision surgery at the treated level, secondary surgery on adjacent levels, segmental mobility of treated and adjacent levels, and work status.

DATA COLLECTION AND ANALYSIS

Study selection was performed independently by three review authors, and 'Risk of bias' assessment and data extraction were performed by two review authors. In case of missing data or insufficient information for a judgement about risk of bias, we tried to contact the study authors or the study sponsor. The data were entered into RevMan by one review author and subsequently checked by a second review author. We assessed the quality of evidence using GRADE. We analysed heterogeneity and performed sensitivity analyses for the pooled analyses.

MAIN RESULTS

We included nine studies (2400 participants), five of which had a low risk of bias. Eight of these studies were industry sponsored. The most important results showed low-quality evidence for a small but significant difference in alleviation of arm pain at one to two years in favour of arthroplasty (mean difference (MD) -1.54; 95% confidence interval (CI) -2.86 to -0.22; 100-point scale). A small study effect could not be ruled out for this outcome in the sensitivity analyses. This means that smaller studies (or small published subsets of larger studies) showed larger differences for this outcome, which may indicate publication bias. Also, moderate-quality evidence showed a small difference in neck-related functional status at one to two years in favour of arthroplasty (MD -2.79; 95% CI -4.73 to -0.85; 100-point scale) and a small difference in neurological outcome in favour of arthroplasty (risk ratio (RR) 1.05; 95% CI 1.01 to 1.09). These two outcomes were robust to sensitivity analyses. For none of the primary outcomes, was a clinically relevant difference shown. Additionally, there was high-quality evidence for a large, statistically significant difference in segmental mobility at one to two years (measured as degrees segmental range of motion) at the treated level (MD 6.90; 95% CI 5.45 to 8.35). There was low-quality evidence that there was no statistically significant difference in secondary surgery at the adjacent levels at one to two years (RR 0.60; 95% CI 0.35 to 1.02). The latter was not robust to sensitivity analyses.

AUTHORS' CONCLUSIONS

There was a tendency for clinical results to be in favour of arthroplasty; often these were statistically significant. However, differences in effect size were invariably small and not clinically relevant for all primary outcomes. Significance was often gained or lost in the varying sensitivity analyses, probably owing to the relatively small number of studies, in combination with the small differences that were found. Given the fact that all of the included studies were not blinded, this could be due to patient or carer expectations. However, at this time both treatments can be seen as valid options with respect to results at a maximum of one to two years. Given the current absence of truly long-term results, use of these mobile disc prostheses should still be limited to clinical trials. There was high-quality evidence that the goal of preservation of segmental mobility in arthroplasty was met. A statistically significant effect on the incidence of secondary symptoms at adjacent levels, the primary goal of arthroplasty over fusion, was not found at one to two years. If there was a protective effect, this should become clearer over time. A future update, when studies with 'truly long-term' results (five years or more) become available, should focus on this issue.

Cervical total disc arthroplasty

Symptomatic adjacent segment degeneration of the cervical spine remains problematic for patients and surgeons alike. Despite advances in surgical techniques and instrumentation, the solution remains elusive. Spurred by the success of total joint arthroplasty in hips and knees, surgeons and industry have turned to motion preservation devices in the cervical spine. By preserving motion at the diseased level, the hope is that adjacent segment degeneration can be prevented. Multiple cervical disc arthroplasty devices have come onto the market and completed Food and Drug Administration Investigational Device Exemption trials. Though some of the early results demonstrate equivalency of arthroplasty to fusion, compelling evidence of benefits in terms of symptomatic adjacent segment degeneration are lacking. In addition, non-industry-sponsored studies indicate that these devices are equivalent to fusion in terms of adjacent segment degeneration. Longer-term studies will eventually provide the definitive answer.

Cervical disc arthroplasty versus fusion for single-level symptomatic cervical disc disease: a meta-analysis of randomized controlled trials

OBJECTIVE

To evaluate the safety and effectiveness of cervical disc arthroplasty (CDA) versus anterior cervical discectomy and fusion (ACDF) for single-level symptomatic cervical disc disease.

METHODS

We identified eligible randomized controlled trials (RCTs) in PubMed (April 2011), EMBASE (April 2011) and Cochrane Central Register of Controlled Trials (April 2011). Data were collected and extracted by two reviewers independently. The methodological quality and clinical relevance of the included studies were assessed. Data analysis was conducted with RevMan 5.0.

RESULTS

Six RCTs involving 1,745 patients were included. The pooled analysis showed a higher prevalence of neurological and overall success [(P = 0.004, RR = 1.06, 95% CI = 1.02-1.10), (P = 0.0005, RR = 1.14, 95% CI = 1.06-1.22)], and a lower incidence of dysphagia and reoperation related to adjacent-segment degeneration [(P = 0.04, RR = 0.30, 95% CI = 0.09-0.97), (P = 0.03, RR = 0.46, 95% CI = 0.23-0.91)] with CDA compared to ACDF. However, there was no statistical difference in neck disability index (P = 0.92, SMD = 0.01, 95% CI = -0.25 to 0.27), neck and arm pain scores[(P = 0.33, SMD = -0.12, 95% CI = -0.37 to 0.13), (P = 0.54, SMD = 0.17, 95% CI = -0.36 to 0.70)], incidence of complications related to the implant or surgical procedure and reoperation related to primary surgery [(P = 0.32, RR = 0.76, 95% CI = 0.45-1.30), (P = 0.09, RR = 0.48, 95% CI = 0.20-1.12)].

CONCLUSION

Compared with ACDF, CDA carry a lower incidence of dysphagia complications and reoperation related to adjacent-segment degeneration, and a higher prevalence of neurological and overall success at 2 years postoperatively. As the poor quality of the included studies, it is still uncertain whether CDR is more effective and safer than ACDF treating single-level symptomatic cervical disc disease. Future large-scale RCTs with long-term follow-up are needed to provide clear evidence.