Cervical intervertebral disc replacement

One-Pot Construction of Articular Cartilage-Like Hydrogel Coating for Durable Aqueous Lubrication

Articular cartilage has an appropriate multilayer structure and superior tribological properties and provides a structural paradigm for design of lubricating materials. However, mimicking articular cartilage traits on prosthetic materials with durable lubrication remains a huge challenge. Herein, an ingenious three-in-one strategy is developed for constructing an articular cartilage-like bilayer hydrogel coating on the surface of ultra-high molecular weight polyethylene (BH-UPE), which makes full use of conceptions of interfacial interlinking, high-entanglement crosslinking, and interface-modulated polymerization. The hydrogel coating is tightly interlinked with UPE substrate through hydrogel-UPE interchain entanglement and bonding. The hydrogel chains are highly entangled with each other to form a dense tough layer with negligible hysteresis for load-bearing by reducing the amounts of crosslinker and hydrophilic initiator to p.p.m. levels. Meanwhile, the polymerization of monomers in the top surface region is suppressed via interface-modulated polymerization, thus introducing a porous surface for effective aqueous lubrication. As a result, BH-UPE exhibits an ultralow friction coefficient of 0.0048 during 10 000 cycles under a load of 0.9 MPa, demonstrating great potential as an advanced bearing material for disc prosthesis. This work may provide a new way to build stable bilayer coatings and have important implications for development of biological lubricating materials.

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.

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.

Comparing exercise and patient education with usual care in the treatment of hip dysplasia: a protocol for a randomised controlled trial with 6-month follow-up (MovetheHip trial)

INTRODUCTION

Surgery is not a viable treatment for all patients with hip dysplasia. Currently, usual care for these patients is limited to a consultation on self-management. We have shown that an exercise and patient education intervention is a feasible and acceptable intervention for patients not receiving surgery. Therefore, we aim to investigate whether patients with hip dysplasia randomised to exercise and patient education have a different mean change in self-reported pain compared with those randomised to usual care over 6 months. Furthermore, we aim to evaluate the cost-effectiveness and perform a process evaluation.

METHODS AND ANALYSIS

In a randomised controlled trial, 200 young and middle-aged patients will be randomised to either exercise and patient education or usual care at a 1:1 ratio through permuted block randomisation. The intervention group will receive exercise instruction and patient education over 6 months. The usual care group will receive one consultation on self-management of hip symptoms. The primary outcome is the self-reported mean change in the pain subscale of the Copenhagen Hip and Groin Outcome Score (HAGOS). Secondary outcomes include mean changes in the other HAGOS subscales, in the Short Version of the International Hip Outcome Tool, in performance, balance and maximal hip muscle strength. Between-group comparison from baseline to 6-month follow-up will be made with intention-to-treat analyses with a mixed-effects model. Cost-effectiveness will be evaluated by relating quality-adjusted life years and differences in HAGOS pain to differences in costs over 12 months. The functioning of the intervention will be evaluated as implementation, mechanisms of change and contextual factors.

ETHICS AND DISSEMINATION

The study protocol was approved by the Committee on Health Research Ethics in the Central Denmark Region and registered at ClinicalTrials. Positive, negative and inconclusive findings will be disseminated through international peer-reviewed scientific journals and international conferences.

TRIAL REGISTRATION NUMBER

NCT04795843.

Heterotopic Ossification After Prestige-LP Cervical Disc Arthroplasty Is Related to Insufficient Sagittal Coverage of the Endplate By the Prosthesis

Background

Heterotopic ossification (HO) is a major complication after cervical disc arthroplasty (CDR) that has attracted the attention of spine surgeons. There remains a great deal of controversy regarding the surgical risk factors. The present study investigated the correlation between insufficient sagittal coverage of the prosthesis-endplate and HO after CDR and explored strategies to prevent it.

Material/Methods

We included 73 patients who underwent Prestige-LP arthroplasty. Patients were divided into HO and non-HO groups. Related data, including radiological, clinical information, were collected. HO was graded using the McAfee classification. Analysis was performed to correlate HO to the surgical segmental range of motion (ROM) at last follow-up. To evaluate the insufficient sagittal coverage of the prosthesis-endplate and other factors for developing HO, receiver operating characteristic (ROC) curves were analyzed for insufficient sagittal coverage.

Results

Among 73 patients, 24 patients had HO at the last follow-up (HO incidence: 32.9%). The ROM in the HO group was significantly lower (P<0.001). The insufficient sagittal coverage of the upper and lower prosthesis-endplate, the height of intervertebral space, and the preoperative and postoperative ROM were related to HO (P<0.05). Multivariate logistic regression analysis showed that only insufficient sagittal coverage of the upper prosthesis-endplate was related to HO (P=0.023), and ROC curve analysis revealed that HO was more likely to occur with insufficient sagittal coverage distance ≥2.5 mm.

Conclusions

HO after CDR causes a reduction in ROM, the occurrence of which is associated with insufficient sagittal coverage of the prosthesis-endplate. HO was more likely to occur with insufficient sagittal coverage distance ≥2.5 mm.

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 cross-sectional analysis of 1347 complications for cervical disc replacements from medical device reports maintained by the United States Food and Drug Administration

BACKGROUND CONTEXT

Cervical disc replacement (CDR) has increased in popularity over the past decade based on published outcomes from FDA IDE studies with narrowly defined inclusion and exclusion criteria. A low rate of complications was noted in these studies. The broader complication profile for CDR in widespread clinical practice has yet to be described.

PURPOSE

To outline the complications reported to the FDA regarding commonly used CDR products STUDY DESIGN/SETTING: Retrospective database review PATIENT SAMPLE: Nationwide database of reported complications related to CDR products from patients across the country OUTCOME MEASURES: Complications related to CDR METHODS: We queried the MAUDE database and Alternative Summary Reporting (ASR) data files submitted between January 2005 to March 2020. The complications listed for seven FDA-approved CDR implants were analyzed. The entries in the databases were cataloged for complication type, date of entry, source of report, and whether the investigation was "complete". Reports that had too little information to extract relevant data were excluded.

RESULTS

There were 1,517 entries identified in the MAUDE database. After removal of duplicate entries and entries without sufficient information, there were 1,347 entries analyzed. The top five complications were (1) migration of implant (338 entries, 25.2%) (2) insertion problem/failure (312 entries, 23.3%) (3) neck pain (203 entries, 15.2%) (4) heterotopic ossification (108 entries, 8.1%) and (5) radiculopathy (90 entries, 8.1%). The number of analyzed implant-related MAUDE entries and most common implant-related complication for each implant was 209 entries for insertion problem/failure for Mobi-C; 158 entries for migration of implant for ProDisc-C; 154 entries for insertion problem/failure for Bryan cervical disc; 130 entries for migration of implant for Prestige cervical disc; 49 entries for migration of implant for PCM cervical disc; 12 entries for migration of implant for M6 and 10 entries for migration of implant for Secure-C. Only 263 entries (19.5%) were deemed "complete". Most entries were from the manufacturer/company representative/distributor (923 entries, 70%). There were no entries related to cervical disc replacement devices within the ASR data.

CONCLUSIONS

The MAUDE database highlights complications related to CDR implants that may not be emphasized in currently published studies. It is important to understand this broad complication profile for CDR to ensure safe utilization of this new technology.

An Eight-Year Follow-Up Study on the Treatment of Single-Level Cervical Spondylosis Through Intervertebral Disc Replacement and Anterior Cervical Decompression and Fusion

Objective

To compare the efficacy and safety of the postoperative long‐term effect of the treatment of single‐level cervical spondylosis through anterior cervical discectomy and fusion (ACDF) and artificial cervical disc replacement (ACDR).

Methods

This is a retrospective contrastive study, which was conducted for the period of January 2007 and January 2009 at the Department of Spine Surgery of the First Affiliated Hospital of Xinjiang Medical University. A total of 113 patients were divided into two groups depending on the operation method: ACDF group (fusion group, n = 66) and ACDR group (replacement group, n = 47). The ACDR group comprised of 23 males and 24 females. The age of these patients ranged from 31–60 years, with an average age of 42.89 ± 6.30 years. The ACDF group comprised of 38 males and 28 females. The age of these patients ranged from 28–73 years old, with an average age of 49.38 ± 9.89 years old. The evaluation index included the visual analogue scale (VAS), neck disability index (NDI), range of motion, dysphagia, adjacent vertebral disease, and related complications (prosthesis displacement, heterotopic ossification, etc.).

Results

A total of 113 patients met the inclusion criteria, and these patients receive more than 96 months of follow‐up. The VAS and NDI of these two groups of patients significantly improved, when compared with those before the operation. In the last follow‐up visit, the range of motion in the ACDR group and ACDF group was 43.22 ± 3.58 and 32.54 ± 2.82, respectively, and both are significantly different comparing to the values measured before the operation (P < 0.05). The dysphagia incidence of the ACDR group was higher than that of the ACDF group at the 36th month, but was lower than that of the ACDF group in other points time. In the last follow‐up visit, six patients (12.77%) in the ACDR group and 18 patients (27.27%) in the ACDF suffered from adjacent segment degeneration (ASD). The general complication rate in the replacement group and fusion group was 38.31% and 37.88%, respectively, but the difference between the two groups was not statistically significant (P > 0.05).

Conclusion

Overall, the clinical efficacy and related complication rate of single‐level cervical spondylosis after an anterior cervical approach operation was superior in the ACDR group when compared to the ACDF group.

Safety and efficacy of cervical disc arthroplasty in preventing the adjacent segment disease: a meta-analysis of mid- to long-term outcomes in prospective, randomized, controlled multicenter studies

Objectives

Cervical disc arthroplasty (CDA) has become an alternative treatment for cervical radiculopathy and myelopathy. This technique preserves appropriate motion at both the index and adjacent disc levels and consequently may prevent adjacent segment degeneration (ASD). The authors performed a meta-analysis to compare the safety and efficacy of CDA to those of the gold standard, anterior cervical discectomy and fusion (ACDF). Both surgical and clinical parameters were employed to verify the hypothesis that CDA can reduce the risk of ASD.

Methods

The meta-analysis comprised high-quality randomized controlled trials that compared CDA and ACDF treatments of cervical degenerative disc disease. Included papers reported data for at least one of the following outcomes: 1) surgical parameters, 2) questionnaire clinical indices (pre- and postoperative values), and 3) complication rates at 24 months; in addition, for ASD we analyzed 60 month or longer follow-ups. We used mean differences (MDs) or ORs to compare treatment effects between CDA and ACDF.

Results

Twenty studies with 3,656 patients (2,140 with CDA and 1,516 with ACDF) met the inclusion criteria. CDA surgery, with mean duration longer than that of ACDF, was associated with higher blood loss. Visual analog scale neck pain score was significantly smaller for CDA (mean difference =−2.30, 95% CI [−3.72; −0.87], P=0.002). The frequency of dysphagia/dysphonia (OR =0.69, 95% CI [0.49; 0.98], P=0.04) as well as the long-term ASD rate for CDA was significantly smaller (OR =0.33, 95% CI [0.21; 0.50], P<0.0001).

Conclusion

A significantly lower probability of ASD reoperations in the CDA cohort after a 60-month or longer follow-up was the most important finding of this study. Despite the moderate quality of this evidence, the pooled data corroborated for the very first time that CDA was efficacious in preventing ASD.

Is the behavior of disc replacement adjacent to fusion affected by the location of the fused level in hybrid surgery?

BACKGROUND CONTEXT

Hybrid surgery (HS), consisting of cervical disc arthroplasty (CDA) at the mobile level, along with anterior cervical discectomy and fusion at the spondylotic level, could be a promising treatment for patients with multilevel cervical degenerative disc disease (DDD). An advantage of this technique is that it uses an optimal procedure according to the status of each level. However, information is lacking regarding the influence of the relative location of the replacement and the fusion segment in vivo.

PURPOSE

We conducted the present study to investigate whether the location of the fusion affected the behavior of the disc replacement and adjacent segments in HS in vivo.

STUDY DESIGN

This is an observational study.

PATIENT SAMPLE

The numbers of patients in the arthroplasty-fusion (AF) and fusion-arthroplasty (FA) groups were 51 and 24, respectively.

OUTCOME MEASURES

The Japanese Orthopedic Association (JOA), Neck Disability Index (NDI), and Visual Analog Scale (VAS) scores were evaluated. Global and segmental lordosis, the range of motion (ROM) of C2-C7, and the operated and adjacent segments were measured. Fusion rate and radiological changes at adjacent levels were observed.

METHODS

Between January 2010 and July 2016, 75 patients with cervical DDD at two contiguous levels undergoing a two-level HS were retrospectively reviewed. The patients were divided into AF and FA groups according to the locations of the disc replacement. Clinical outcomes were evaluated according to the JOA, NDI, and VAS scores. Radiological parameters, including global and segmental lordosis, the ROM of C2-C7, the operated and adjacent segments, and complications, were also evaluated.

RESULTS

Although the JOA, NDI, and VAS scores were improved in both the AF and the FA groups, no significant differences were found between the two groups at any follow-up point. Both groups maintained cervical lordosis, but no difference was found between the groups. Segmental lordosis at the fusion segment was significantly improved postoperatively (p<.001), whereas it was maintained at the arthroplasty segment. The ROM of C2-C7 was significantly decreased in both groups postoperatively (AF p=.001, FA p=.014), but no difference was found between the groups. The FA group exhibited a non-significant improvement in ROM at the arthroplasty segment. The ROM adjacent to the arthroplasty segment was increased, although not significantly, whereas the ROM adjacent to the fusion segment was significantly improved after surgery in both groups (p<.001). Fusion was achieved in all patients. No significant difference in complications was found between the groups.

CONCLUSIONS

In HS, cephalic or caudal fusion segments to the arthroplasty segment did not affect the clinical outcomes and the behavior of CDA. However, the ROM of adjacent segments was affected by the location of the fusion segment; segments adjacent to fusion segments had greater ROMs than segments adjacent to arthroplasty segments.

Influence of assigned material combination in a simulated total cervical disc replacement design on kinematics of a model of the full cervical spine: A finite element analysis study

BACKGROUND

Although cervical total disc replacement (TDR) is becoming popular, there are no finite analysis (FEA) studies involving a model of the full spine cervical (C1-C7) and determination of the influence of materials assigned to different parts of a specified TDR design on biomechanics of the model when TDR implantation is simulated.

OBJECTIVE

To determine the influence of assigned material combination, for a given cervical TDR design, on the kinematics of a model of the full cervical spine.

METHODS

A three-dimensional solid model of the full cervical spine was constructed, a finite element mesh was obtained (INT Model), after which FEA was used to determine range of motion (ROM) at each of the intersegmental positions under three clinically-relevant loadings. INT model was then modified by simulated implantation of a notional endplates-and-mobile insert TDR design, at C5-C6 (TDR Model), and six clinically-relevant applied loadings were applied. Four variants of TDR Model were used, the difference between them being in the materials assigned to the endplates and the mobile insert. Under each of the loadings, principal motions at each of the intersegmental positions were determined and compared to counterpart motions when INT Model was used.

RESULTS

Comparison of ROM results of INT Model with relevant experimental results reported in the literature showed that the model was validated. With TDR Model, the smallest overall mean of the absolute values of the % change in principal intersegmental motions (relative to corresponding results in INT Model) was when the material assigned to both the endplates and the mobile insert was poly(ether-ether-ketone).

CONCLUSION

In a simulated implantation of a notional endplates-and-mobile-insert TDR design in a model of the full cervical spine, material combination assigned to the parts of the design exerts a marked influence on the kinematics of the model.

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.

Cervical disc arthroplasty for symptomatic cervical disc disease: Traditional and Bayesian meta-analysis with trial sequential analysis

OBJECTIVE

Cervical disc arthroplasty (CDA) has been designed as a substitute for anterior cervical discectomy and fusion (ACDF) in the treatment of symptomatic cervical disc disease (CDD). Several researchers have compared CDA with ACDF for the treatment of symptomatic CDD; however, the findings of these studies are inconclusive. Using recently published evidence, this meta-analysis was conducted to further verify the benefits and harms of using CDA for treatment of symptomatic CDD.

METHODS

Relevant trials were identified by searching the PubMed, EMBASE, and Cochrane Library databases. Outcomes were reported as odds ratio or standardized mean difference. Both traditional frequentist and Bayesian approaches were used to synthesize evidence within random-effects models. Trial sequential analysis (TSA) was applied to test the robustness of our findings and obtain more conservative estimates.

RESULTS

Nineteen trials were included. The findings of this meta-analysis demonstrated better overall, neck disability index (NDI), and neurological success; lower NDI and neck and arm pain scores; higher 36-Item Short Form Health Survey (SF-36) Physical Component Summary (PCS) and Mental Component Summary (MCS) scores; more patient satisfaction; greater range of motion at the operative level; and fewer secondary surgical procedures (all P < 0.05) in the CDA group compared with the ACDF group. CDA was not significantly different from ACDF in the rate of adverse events (P > 0.05). TSA of overall success suggested that the cumulative z-curve crossed both the conventional boundary and the trial sequential monitoring boundary for benefit, indicating sufficient and conclusive evidence had been ascertained.

CONCLUSIONS

For treating symptomatic CDD, CDA was superior to ACDF in terms of overall, NDI, and neurological success; NDI and neck and arm pain scores; SF-36 PCS and MCS scores; patient satisfaction; ROM at the operative level; and secondary surgical procedures rate. Additionally, there was no significant difference between CDA and ACDF in the rate of adverse events. However, as the CDA procedure is a relatively newer operative technique, long-term results and evaluation are necessary before CDA is routinely used in clinical practice.

Comparing Nonrandomized Observational Studies With Randomized Controlled Trials in Cervical Disc Arthroplasty: A Meta-analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

To compare the treatment effects of observational studies versus randomized controlled trials (RCTs) in cervical disc arthroplasty.

SUMMARY OF BACKGROUND DATA

RCTs can be logistically challenging and sometimes insufficiently generalizable; well-designed observational studies have been suggested as an alternative. We hypothesized that treatment effects of observational studies in cervical disc arthroplasty are similar to those of RCTs.

METHODS

We searched electronic database from 2000 to 2014. The Neck Disability Index (NDI) was the primary outcome from which the standardized pre-and-post mean difference (Hedges's g) was determined. Meta-analysis was performed to compare Hedges's g from observational studies to that of RCTs. Potential moderator variables including study quality, age, gender, industry sponsorship, location by continent, and disc types were also collected and analyzed. Observational studies were further stratified into prospective and retrospective, and they were compared to each other as well as to RCTs.

RESULTS

We identified nine RCTs, 28 observational studies, and one hybrid study for meta-analysis. NDI Hedges's g was 2.15 for RCTs and 2.03 for observational studies, which was not significant (P = 0.416). No significant difference was found in secondary outcomes. However, after further stratification, prospective observational studies had less treatment effect in Visual Analog Scale neck compared with that of RCTs (1.60 vs. 2.11, P = 0.006). RCTs recruited younger patients (44.1 vs. 45.6, P = 0.008) with worse NDI at baseline (54.30 vs. 46.92, P < 0.001). Patients treated with ProDisc-C showed less standardized improvement on the NDI compared with the patients treated with Prestige (1.41 vs. 2.48, P = 0.026).

CONCLUSION

Prospective observational studies that utilize the same features of RCTs such as inclusion and exclusion criteria validated clinical outcomes, and statistical methods can provide valuable information about the treatment effects on a generalizable population.

LEVEL OF EVIDENCE

4.

Traumatic Migration of the Bryan Cervical Disc Arthroplasty

Study Design Case study. Objective To describe a case of dislodgment and migration of the Bryan Cervical Disc (Medtronic Sofamor Danek, Memphis, Tennessee, United States) arthroplasty more than 6 months after implantation secondary to low-energy trauma. Methods The inpatient, outpatient, and radiographic medical records of a patient with traumatic migration of the Bryan Cervical Disc arthroplasty were reviewed. The authors have no relevant disclosures to report. Results A 36-year-old man with chronic left upper extremity radiculopathy underwent uncomplicated Bryan Cervical Disc arthroplasty at C5-C6, with complete resolution of his symptoms. Approximately 6 months after his index procedure, he sustained low-energy trauma to the posterior cervical spine, after being struck by a book falling from a shelf. The injury forced his neck into flexion, and though he did not have recurrence of his radiculopathy symptoms, radiographs demonstrated anterior migration of the arthroplasty device. He underwent revision to anterior cervical diskectomy and fusion. Conclusions Although extremely rare, it is imperative that surgeons consider the potential for failure of osseous integration in patients undergoing cervical disk arthroplasty, even beyond 3 to 6 months postoperatively. This concern is especially relevant to press-fit or milled devices like the Bryan Cervical Disc arthroplasty, which lack direct fixation into adjacent vertebral bodies. We are considering modification of our postoperative protocol to improve protection of the device after implantation, even beyond 3 months postoperatively.

Biomechanics of Artificial Disc Replacements Adjacent to a 2-Level Fusion in 4-Level Hybrid Constructs: An In Vitro Investigation

Background

The ideal procedure for multilevel cervical degenerative disc diseases remains controversial. Recent studies on hybrid surgery combining anterior cervical discectomy and fusion (ACDF) and artificial cervical disc replacement (ACDR) for 2-level and 3-level constructs have been reported in the literature. The purpose of this study was to estimate the biomechanics of 3 kinds of 4-level hybrid constructs, which are more likely to be used clinically compared to 4-level arthrodesis.

Material/Methods

Eighteen human cadaveric spines (C2–T1) were evaluated in different testing conditions: intact, with 3 kinds of 4-level hybrid constructs (hybrid C3–4 ACDR+C4–6 ACDF+C6–7ACDR; hybrid C3–5ACDF+C5–6ACDR+C6–7ACDR; hybrid C3–4ACDR+C4–5ACDR+C5–7ACDF); and 4-level fusion.

Results

Four-level fusion resulted in significant decrease in the C3–C7 ROM compared with the intact spine. The 3 different 4-level hybrid treatment groups caused only slight change at the instrumented levels compared to intact except for flexion. At the adjacent levels, 4-level fusion resulted in significant increase of contribution of both upper and lower adjacent levels. However, for the 3 hybrid constructs, significant changes of motion increase far lower than 4P at adjacent levels were only noted in partial loading conditions. No destabilizing effect or hypermobility were observed in any 4-level hybrid construct.

Conclusions

Four-level fusion significantly eliminated motion within the construct and increased motion at the adjacent segments. For all 3 different 4-level hybrid constructs, ACDR normalized motion of the index segment and adjacent segments with no significant hypermobility. Compared with the 4-level ACDF condition, the artificial discs in 4-level hybrid constructs had biomechanical advantages compared to fusion in normalizing adjacent level motion.

Biomechanics of Hybrid Anterior Cervical Fusion and Artificial Disc Replacement in 3-Level Constructs: An In Vitro Investigation

Background

The ideal surgical approach for cervical disk disease remains controversial, especially for multilevel cervical disease. The purpose of this study was to investigate the biomechanics of the cervical spine after 3-level hybrid surgery compared with 3-level anterior cervical discectomy and fusion (ACDF).

Material/Methods

Eighteen human cadaveric spines (C2-T1) were evaluated under displacement-input protocol. After intact testing, a simulated hybrid construct or fusion construct was created between C3 to C6 and tested in the following 3 conditions: 3-level disc plate disc (3DPD), 3-level plate disc plate (3PDP), and 3-level plate (3P).

Results

Compared to intact, almost 65~80% of motion was successfully restricted at C3-C6 fusion levels (p<0.05). 3DPD construct resulted in slight increase at the 3 instrumented levels (p>0.05). 3PDP construct resulted in significant decrease of ROM at C3-C6 levels less than 3P (p<0.05). Both 3DPD and 3PDP caused significant reduction of ROM at the arthrodesis level and produced motion increase at the arthroplasty level. For adjacent levels, 3P resulted in markedly increased contribution of both upper and lower adjacent levels (p<0.05). Significant motion increases lower than 3P were only noted at partly adjacent levels in some conditions for 3DPD and 3PDP (p<0.05).

Conclusions

ACDF eliminated motion within the construct and greatly increased adjacent motion. Artificial cervical disc replacement normalized motion of its segment and adjacent segments. While hybrid conditions failed to restore normal motion within the construct, they significantly normalized motion in adjacent segments compared with the 3-level ACDF condition. The artificial disc in 3-level constructs has biomechanical advantages compared to fusion in normalizing motion.

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.

Minimum 4-year outcomes of cervical total disc arthroplasty versus fusion: a meta-analysis based on prospective randomized controlled trials

The prevalence of cervical disc disease is high, and the traditional surgical method of anterior cervical discectomy and fusion (ACDF) carries with it the disadvantages of motion loss at the operated level, and accelerated adjacent level disc degeneration. Preliminary results of the efficacy and reoperative rate comparing TDA versus ACDF have been reported; however, the long-term outcomes of TDA versus ACDF still remain a topic of debate. This review was prepared following the standard procedures set forth by the Cochrane Collaboration organization, and preferred reporting items for systematic reviews and meta-analyses (PRISMA). The only studies included were randomized controlled trials with a minimum of 4 years of follow-up data. The meta-analysis included the neck disability index (NDI), visual analog scale (VAS) of neck and arm pain, SF-36 physical component scores (SF-36 PCS), over success, neurological success, work status, implant-related complications, and secondary surgery events. Four randomized controlled trials meet the inclusion criteria. The long-term improvement of NDI, VAS of neck and arm pain, SF-36 PCS, over success, and neurological success favored the TDA group. The TDA group also had a lower incidence of secondary surgery for both the index level (RR: 0.45 [0.28, 0.72]) and adjacent level (RR: 0.53 [0.33, 0.88]). In this meta-analysis of 4 included RCTs with a minimum 4 years of follow-ups, total disc arthroplasty showed improvements over ACDF as measured by the NDI, VAS of neck and arm pain, and SF-36 PCS.

Cervical total disc replacement is superior to anterior cervical decompression and fusion: a meta-analysis of prospective randomized controlled trials

BACKGROUND

Despite being considered the standard surgical procedure for symptomatic cervical disc disease, anterior cervical decompression and fusion invariably accelerates adjacent segment degeneration. Cervical total disc replacement is a motion-preserving procedure developed as a substitute to fusion. Whether cervical total disc replacement is superior to fusion remains unclear.

METHODS

We comprehensively searched PubMed, EMBASE, Medline, and the Cochrane Library in accordance with the inclusion criteria to identify possible studies. The retrieved results were last updated on December 12, 2014. We classified the studies as short-term and midterm follow-up.

RESULTS

Nineteen randomized controlled trials involving 4516 cases were identified. Compared with anterior cervical decompression and fusion, cervical total disc replacement had better functional outcomes (neck disability index [NDI], NDI success, neurological success, neck pain scores reported on a numerical rating scale [NRS], visual analog scales scores and overall success), greater segmental motion at the index level, fewer adverse events and fewer secondary surgical procedures at the index and adjacent levels in short-term follow-up (P < 0.05). With midterm follow-up, the cervical total disc replacement group indicated superiority in the NDI, neurological success, pain assessment (NRS), and secondary surgical procedures at the index level (P < 0.05). The Short Form 36 (SF-36) and segmental motion at the adjacent level in the short-term follow-up showed no significant difference between the two procedures, as did the secondary surgical procedure rates at the adjacent level with midterm follow-up (P > 0.05).

CONCLUSIONS

Cervical total disc replacement presented favorable functional outcomes, fewer adverse events, and fewer secondary surgical procedures. The efficacy and safety of cervical total disc replacement are superior to those of fusion. Longer-term, multicenter studies are required for a better evaluation of the long-term efficacy and safety of the two procedures.

Early clinical and radiographical results of keel-less and shallow keel cervical disc replacement

Background:

Cervical disc replacements has been shown to be as effective as fusions in the treatment of radiculopathy or myelopathy due to disc prolapse. Newer implants were designed to reduce the difficulty of end-plate preparation. Since 2010, the authors have started using Discocerv (Alphatec Spine, Carlsbad, USA) a keel-less implant and Activ-C (B. Braun, Sheffield, UK), a shallow keel implant.

Aim:

The aim of this study was to compare the duration of surgery between cervical disc replacement and anterior cervical discectomy and fusion, and also to evaluate the functional outcome, complications, and radiographic outcome of cervical disc replacement.

Results:

Fifty patients were included (20 disc replacement and 30 fusion). This was a single surgeon retrospective study, with all surgery performed by the senior author (RT). The mean operation duration for single-level disc replacement was 2.6 h, and for single-level fusion was 2.4 h (P = 0.4684). For 2-levels surgery, the result was 3.5 h for 2-level hybrid surgery (one level disc replacement and one level fusion) and 3.4 h for fusion (P = 0.4489). Disc replacement resulted in preservation of an average of 67% of the angle of motion at the sagittal plane (FFflexion-extension). The average range of motion after disc replacement was 6.1°. The median clinical follow-up duration was 2 years (average 1.8 years). There was no incidence of major complications or significant neurovascular injury in this series of patients. A significant improvement in short form-36 scores was seen as early as 3 months postoperative (from 58 preoperative to 92 at 3 months). The improvement was sustained up to the fourth year of follow-up.

Conclusion:

Cervical arthroplasty with keel-less and shallow keel implants are safe and relatively easy to perform. The surgical time for disc replacement is not significantly longer than standard fusion surgery. There is reasonably good preservation of motion. The short-term functional improvement is good, and we await further long-term outcome results. The authors felt that cervical disc replacement will have an important role in the treatment of cervical degenerative disc disease in the future.

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.

Mid- to long-term outcomes after cervical disc arthroplasty compared with anterior discectomy and fusion: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

To evaluate the mid- to long-term clinical outcomes after cervical disc arthroplasty (CDA) as compared with anterior cervical discectomy and fusion (ACDF) for the treatment of symptomatic cervical disc disease.

METHODS

A systematic review and a meta-analysis were performed for articles published up to March 2013. Randomized controlled trials that reported mid- to long-term outcomes (≥48 months) after CDA as compared with ACDF were included. Two authors independently extracted the articles and the predefined data.

RESULTS

Five US Food and Drug Administration randomized controlled trials that reported 4-6 years of follow-up data were retrieved. Patients who underwent CDA had a lower mid- to long-term rate of reoperation and had greater mid- to long-term improvements in the Neck Disability Index, neck and arm pain scores, and Short Form 36 Health Survey physical component score than did those who underwent ACDF. Segmental motion was maintained in patients who underwent CDA. The mid- to long-term rates of adjacent segment disease and neurological success were not significantly different between the two groups.

CONCLUSIONS

CDA may result in better mid- to long-term functional recovery and a lower rate of subsequent surgical procedures than ACDF would. A review of the literature showed that only an insufficient number of studies had investigated adjacent segment disease; therefore, it is mandatory that adequate future research should focus in this direction.