Intermediate clinical and radiological results of cervical TDR (Mobi-C) with up to 2 years of follow-up

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Clinical and radiological outcome 1-year after cervical total disc replacement using the Signus ROTAIO - Prosthesis

INTRODUCTION

The instantaneous center of rotation (iCOR) of a motion segment has been shown to correlate with its total range of motion (ROM). Importantly, a correlation of the correct placement of cervical total disc replacement (cTDR) to preserve a physiological iCOR has been previously identified. However, changes of these parameters and the corresponding clinical relevance have hardly been analyzed. This study assesses the radiological and clinical correlation of iCOR and ROM following cTDR.

MATERIALS/METHODS

A retrospective multi-center observational study was conducted and radiological as well as clinical parameters were evaluated preoperatively and 1 year after cTDR with an unconstrained device. Radiographic parameters including flexion/extension X-rays (flex/ex), ROM, iCOR and the implant position in anterior-posterior direction (IP ap), as well as corresponding clinical parameters [(Neck Disability Index (NDI) and the visual analogue scale (VAS)] were assessed.

RESULTS

57 index segments of 53 patients treated with cTDR were analyzed. Pre- and post-operative ROM showed no significant changes (8.0° vs. 10.9°; p > 0.05). Significant correlations between iCOR and IP (Pearson's R: 0.6; p < 0.01) as well as between ROM and IP ap (Pearson's R: - 0.3; p = 0.04) were identified. NDI and VAS improved significantly (p < 0.01). A significant correlation between NDI and IP ap after 12 months (Pearson's R: - 0.39; p < 0.01) was found.

CONCLUSION

Implantation of the tested prosthesis maintains the ROM and results in a physiological iCOR. The exact position of the device correlates with the clinical outcome and emphasize the importance of implant design and precise implant positioning.

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

BACKGROUND CONTEXT

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

PURPOSE

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

STUDY DESIGN

Retrospective cohort and systematic review.

PATIENT SAMPLE

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

OUTCOME MEASURES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Cervical Total Disc Replacement: Food and Drug Administration-Approved Devices

The first US Food and Drug Administration (FDA) approval for cervical total disc replacement (CTDR) was issued in 2007. Since then, 8 more artificial discs have been granted FDA approval for single-level CTDR. Two of these have also been approved for 2-level CTDR. All devices are indicated for levels C3 to C7 for symptomatic patients with radiculopathy or myelopathy caused by disc herniation or spondylosis unresponsive to conservative management. Trials have shown noninferiority of CTDR compared with anterior cervical decompression and fusion in their overall success. Hybrid surgery and CTDR of 3 or more levels are not FDA approved.

Cervical Total Disc Replacement: Long-Term Outcomes

Degenerative disc disease and associated cervical spondylosis or stenosis are common conditions encountered in clinical practice. These conditions may cause progressive cervical radicular or myelopathic symptoms leading to significant impairment. Although anterior cervical discectomy and fusion (ACDF) has been a reliable surgical treatment of cervical myelopathy and radiculopathy, but limitations include loss of cervical range of motion, the concern for adjacent segment degeneration and disease, pseudoarthrosis, complications related to the choice of intervertebral graft, dysphagia, as well as standard anterior cervical approach risk. Cervical total disc arthroplasty has emerged as an alternative operative procedure to ACDF.

The Rate of Heterotopic Ossification Following Cervical Disc Arthroplasty: A Systematic Review and Comparison of Data

STUDY DESIGN

Systematic review.

OBJECTIVES

The purpose of the current study is to determine the overall incidence of Heterotopic Ossification (HO) following cervical disc arthroplasty (CDA) as well as per annum rates.

SUMMARY OF BACKGROUND DATA

CDA is a well-established surgical modality for treatment of one- and two-level degenerative disc disease that has failed conservative treatment. Despite its proven mid-term clinical success, the potential for accelerated HO following CDA remains an area of clinical concern.

METHODS

A MEDLINE literature search was performed using PubMed, the Cochrane Database of Systematic Reviews, and Embase from January 1980 to February 2018. We included studies involving adult patients, who underwent CDA, documentation of HO, with >12 month follow-up. The pooled results were obtained by calculating the effect size based on the logit event rate. Per annum rates were determined based on weighted averages according to average follow-up period.

RESULTS

The initial database review resulted in 230 articles, with 19 articles that met inclusion and exclusion criteria. These pooled results included 2151-disc levels and 1732 patients (50% men and 50% women) who underwent CDA and were evaluated for postoperative HO. The mean age was 45 years with a mean follow-up of 60 months. Sixteen studies reported the occurrence of severe HO resulting in 22.8% of disc levels developing severe HO. When stratifying these studies based on funding type, severe HO was reported at a rate of 21.6% by IDE studies and 27.9% by independent studies.

CONCLUSION

The findings of the pooled data show the incidence of severe HO following CDA to be 22.8%. However, there is a significant difference in reported rates of mild and severe HO between IDE and independent data. This alludes to possible underreporting of HO and severity of HO in the industry sponsored IDE studies when compared with independent studies.

LEVEL OF EVIDENCE

2.

External and internal responses of cervical disc arthroplasty and anterior cervical discectomy and fusion: A finite element modeling study

Surgical treatment for spinal disorders, such as cervical disc herniation and spondylosis, includes the removal of the intervertebral disc and replacement of biological or artificial materials. In the former case, bone graft is used to fill the space, and this conventional procedure is termed anterior cervical discectomy and fusion (ACDF). The latter surgery is termed as artificial disc replacement ADR) or cervical disc arthroplasty (CDA). Surgeries are most commonly performed at one or two levels. The present study was designed to determine the external (range of motion, ROM) and internal (anterior and posterior load sharing) responses of the spines with one-level and two-level surgeries in both models (ACDF and CDA) using a previously validated finite element model (FEM) of the subaxial cervical spinal column. The FEM simulated the vertebra (cancellous core and cortical shell of the body, posterior elements - laminae, pedicles and spinous processes), discs (anulus fibers, ground substance, and nucleus pulposus), anterior and posterior ligaments of the disc and facet joints, and interspinous and supraspinous ligaments. Appropriate material properties were assigned to the spinal components. The United States Food Drug Administration-approved Mobi-C was used for the CDA option. The FEM was exercised under pure flexion and extension moment loading of 2 Nm in the intact state. The overall ROM of the column was obtained. The hybrid loading protocol applied moments that matched the ROM in the intact spine for both one-level (C5-C6) and two-level (C5-C7) ACDF and CDA surgeries. ROM at the level(s) of surgery, termed the index level was obtained. These data along with anterior column load (ACL) and posterior column load (PCL) sharing were obtained for all surgical options at superior and inferior segments (termed adjacent segment outputs). Results for both one-level and two-level surgeries showed that ACDFs decreases ROM at the index level, while CDAs increase motions compared to the intact normal spine. The ROM, ACL, and PCL increased at both adjacent levels for the ACDF while CDA showed a decrease. Although two-level surgeries resulted in increased these biomechanical variables, greater changes to adjacent segment biomechanics in ACDF may accelerate adjacent segment disease. Decreased ROM and lower load sharing in CDAs may limit adjacent segment effects such as accelerated degeneration. Their increased posterior load sharing, however, may need additional attention for patients with suspected facet joint disease.

Artificial Discs in Cervical Disc Replacement: A Meta-Analysis for Comparison of Long-Term Outcomes

BACKGROUND

Cervical disc replacement (CDR) has emerged as an alternative to anterior cervical discectomy and fusion for the surgical treatment of degenerative cervical disc disease. Although comparison of the 2 techniques has been studied in the literature, a thorough assessment of all artificial discs between each has not been performed. The objective of the present study was to examine the long-term outcomes of 5 artificial discs.

METHODS

An electronic literature search was conducted for studies of CDR devices for all years available. Only articles in English were included. Heterotopic ossification, adjacent segment disease, and reoperation comprised the primary outcomes of interest. Pooled descriptive statistics with effect size (ES) and 95% confidence interval were used to synthesize the outcomes for each device.

RESULTS

Sixty-five studies (n = 5785) were included in the analysis. Comparison of the incidence of grade III/IV heterotopic ossification showed a significant variability between the 5 devices (P < 0.001) with ProDisc-C (ES, 38%; 95% confidence interval [CI], 24%-54%) having the highest incidence rate. Overall rate of adjacent segment disease was 14% (95% CI, 7%-23%) with significant associated heterogeneity (P < 0.001). Regarding 2-year reoperation risk, the overall incidence rate was 2% (95% CI, 1%-3%), with nonsignificant variability between devices (P = 0.63). The highest rate was observed in the Discover group (ES, 4%; 95% CI, 0%-13%).

CONCLUSIONS

The results of the present meta-analysis indicate that surgical and clinical outcomes may differ among different CDR devices. These findings may assist surgeons in tailoring their decision making to specific patient profiles. Future multicenter efforts are needed to validate associations found in this study.

Quality of Life in Patients Undergoing Spine Surgery: Systematic Review and Meta-Analysis

STUDY DESIGN

Meta-analysis.

OBJECTIVE

Despite the increasing importance of tracking clinical outcomes using valid patient-reported outcome measures, most providers do not routinely obtain baseline preoperative health-related quality of life (HRQoL) data in patients undergoing spine surgery, precluding objective outcomes analysis in individual practices. We conducted a meta-analysis of pre- and postoperative HRQoL data obtained from the most commonly published instruments to use as reference values.

METHODS

We searched PubMed, EMBASE, and an institutional registry for studies reporting EQ-5D, SF-6D, and Short Form-36 Physical Component Summary scores in patients undergoing surgery for degenerative cervical and lumbar spinal conditions published between 2000 and 2014. Observational data was pooled meta-analytically using an inverse variance-weighted, random-effects model, and statistical comparisons were performed.

RESULTS

Ninety-nine articles were included in the final analysis. Baseline HRQoL scores varied by diagnosis for each of the 3 instruments. On average, postoperative HRQoL scores significantly improved following surgical intervention for each diagnosis using each instrument. There were statistically significant differences in baseline utility values between the EQ-5D and SF-6D instruments for all lumbar diagnoses.

CONCLUSIONS

The pooled HRQoL values presented in this study may be used by practitioners who would otherwise be precluded from quantifying their surgical outcomes due to a lack of baseline data. The results highlight differences in HRQoL between different degenerative spinal diagnoses, as well as the discrepancy between 2 common utility-based instruments. These findings emphasize the need to be cognizant of the specific instruments used when comparing the results of outcome studies.

Comparative Study Between M6-C and Mobi-C Cervical Artificial Disc Replacement: Biomechanical Outcomes and Comparison with Normative Data

OBJECTIVE

Cervical spondylosis affects a huge proportion of the middle-aged population. Degenerative changes can occur in multiple regions of the cervical spine typically affecting the joints, intervertebral discs and endplates. These changes lead to compression of adjacent nervous structures, which results in radiculopathic and myelopathic pain. Various treatment modalities are currently available with non-surgical approaches the initial go to if there is no symptomatic cord compression. Anterior cervical discectomy and fusion, or arthroplasty are the two common surgical approaches if non-surgical treatments fail to relieve symptoms of the patients or there are signs of central cord compression. However, studies have shown that there is an increased risk of adjacent segment disease related to fusion. Cervical disc arthroplasty aims to restore normal range of motion (ROM) in patients with pain and disability due to degenerative disc disease resistant to conservative care. Two common disc prostheses used include M6-C and Mobi-C. Both prostheses comprise a mobile polymer segment sandwiched between two metal endplates with mechanisms resembling an actual intervertebral disc. This study aims to compare the kinematics associated with these prostheses, against the normal range of motion in the non-degenerative population.

METHOD

Patients who underwent M6-C or Mobi-C disc replacements by the senior author from 2012 to 2015 were identified at a single tertiary institution. Routine 3-month postoperative lateral radiographs were analyzed for flexion and extension ROM angles at the involved vertebral level by two independent authors. Data was compared to previous published studies investigating cervical spine ROM of asymptomatic patients.

RESULTS

There was no statistical significance in the difference of overall flexion range between M6-C and Mobi-C prostheses. However, overall range of extension of Mobi-C was greater compared to M6-C (P = 0.028). At C_5-6 , the range of flexion for both implants were similar but lesser compared to asymptomatic patients (P < 0.001). Range of extension was greater in the Mobi-C group (14.2° ± 5.1°) compared to the M6-C (7.3° ± 4.6°) (P = 0.0009). At C_6-7 , there were no statistical differences in both range of flexion and extension between the two prostheses and asymptomatic patients (P > 0.05).

CONCLUSION

The early results regarding restoration of ROM following cervical arthroplasty using either M6-C or Mobi-C prosthesis are encouraging. Long-term follow-up studies are necessary to observe the change in ROM over time with physiological loading and wear patterns.

Dynamic foraminal dimensions during neck extension and rotation in fusion and artificial disc replacement: an observational study

BACKGROUND

Changes in the dimensions of the cervical neural foramina (CNF) are considered to be a key factor in nerve root compression and development of cervical radiculopathy. However, to what extent foraminal geometry differs between patients who underwent anterior cervical discectomy and fusion (ACDF) and those who underwent total disc arthroplasty with an artificial disc (AD) during physiological motion is largely unknown.

PURPOSE

The objective of this study is to compare CNF dimensions during physiological neck motion between ACDF and AD.

STUDY DESIGN/SETTING

This is a retrospective comparative analysis of prospectively collected, consecutive, non-randomized series of patients at a single institution.

PATIENT SAMPLE

A total of 16 single-level C5-C6 ACDF (4 males, 12 females; 28-71 years) and 7 single-level C5-C6 cervical arthroplasty patients (3 males, 4 females; 38-57 years), at least 12 months after surgery (23.6±6.8 months) were included.

OUTCOME MEASURES

Patient demographics, preoperative magnetic resonance imaging (MRI)-based measurements of cervical spine degeneration, and 2-year postoperative measurements of dynamic foraminal geometry were the outcome measures.

METHODS

Biplane X-ray images were acquired during axial neck rotation and neck extension. A computed tomography scan was also acquired from C3 to the first thoracic vertebrae. The subaxial cervical vertebrae (C3-C7) were reconstructed into three-dimensional (3D) bone models for use with model-based tracking. Foraminal height (FH) was calculated as the 3D distance between the superior point of the inferior pedicle and the inferior point of the superior pedicle using custom software. Foraminal width (FW) was similarly calculated as the 3D distance between the anterolateral aspect of the superior vertebral body inferior notch and the posterolateral aspect of the inferior vertebral body superior notch. Dynamic foraminal dimensions were quantified as the minimum (FH.Min, FW.Min), the range (FH.Range, FW.Range), and the median (FH.Med, FW.Med) of each trial and then averaged over trials. Mixed model analysis of variance framework was used to examine the differences between ACDF and AD groups. The initial severity of disc degeneration as determined from preoperative MRI images was introduced as covariates in the models.

RESULTS

At the operated level (C5-C6), FH.Med and FH.Range were smaller in ACDF than in AD during axial rotation and neck extension (p<.003 to p<.05). At the superior adjacent level (C4-C5), no significant difference was found. At the inferior adjacent level (C6-C7), FW.Range was greater in ACDF than in AD during axial rotation and extension (p<.05). At the non-adjacent level (C3-C4), FW.Range was greater in ACDF than in AD during extension (p<.008).

CONCLUSIONS

This study demonstrated decreases in foraminal dimensions and their range for ACDF compared with AD at the operated level. In contrast, it demonstrated increases in the range of foraminal dimensions during motion for ACDF compared with AD at the non-operated segments. Together, these data support the notion that increased mobility at the non-operated segments after ACDF may contribute to a greater risk for adjacent segment degeneration. Because of the significant presence of range variables in the findings, the current data also indicate that a dynamic evaluation is likely more appropriate for evaluation of the differences in foramina between ACDF and AD than a static evaluation.

Prosthesis and Hybrid Strategy Consideration for Treating Two-level Cervical Disc Degeneration in Hybrid Surgery

STUDY DESIGN

Biomechanical analysis using a validated nonlinear finite element (FE) model.

OBJECTIVE

The aim of this study was to combine the strategy of two-level hybrid surgery (HS) to explore how prostheses affect cervical biomechanics.

SUMMARY OF BACKGROUND DATA

Few FE studies have explored differences in biomechanical behavior between combined and stand-alone structured prostheses with HS. No FE studies have considered whether the prosthesis type and hybrid strategy influence two-level HS.

METHODS

Three prostheses-Prodisc-C, PCM, and DCI-were analyzed in flexion and extension during HS at C4-C6. There were two HS constructs: anterior cervical discectomy and fusion (ACDF) conducted at the C4-C5 levels and anterior cervical disc replacement (ACDR) conducted at C5-C6 levels (ACDF/ACDR); ACDR/ACDF.

RESULTS

Flexion motion at adjacent levels was greater than that of intact spine. A maximum increase of 80% was observed with PCM in the ACDF/ACDR group. Extension motion at adjacent levels for both hybrid strategies with PCM, however, was similar to that of intact spine (<10% change), whereas it increased by 14% to 32% with DCI. The strain energy-storing capability with DCI tended to be similar to that of normal discs. Facet stress at the infra-adjacent level, however, significantly increased with DCI in both groups, whereas it increased with PCM and Prodisc-C only in the ACDR/ACDF group. All prostheses produced overloads on cartilage at the arthroplasty level. Prodisc-C and PCM cores showed stress above the yield stress of ultrahigh-molecular-weight polyethylene.

CONCLUSION

Each prosthesis had advantages and disadvantages. In extension, DCI (vs. Prodisc-C and PCM) exhibited more compensation at adjacent levels in terms of motion, moments, and facet stress. The biomechanical performance of Prodisc-C was easily affected by the hybrid strategy. Thus, if only a combined-structure prosthesis is available for two-level HS (C4-C6 level), the hybrid strategy should be carefully evaluated and the ACDF/ACDR construct is recommended to avoid accelerating degeneration of adjacent segments.

LEVEL OF EVIDENCE

5.

Understanding United States Investigational Device Exemption Studies-Clinical Relevance and Importance for Healthcare Economics

INTRODUCTION

The US Food and Drug Administration allows a previously unapproved device to be used clinically to collect safety and effectiveness data under their Investigational Device Exemption (IDE) category. The process usually falls under 3 different trial categories: noninferiority, equivalency, and superiority. To confidently inform our patients, understanding the basic concepts of these trials is paramount. The purpose of this manuscript was to provide a comprehensive review of these topics using recently published IDE trials and economic analyses of cervical total disc replacement as illustrative examples.

CASE STUDY MOBI-C ARTIFICIAL CERVICAL DISC

In 2006, an IDE was initiated to study the safety and effectiveness of total disc replacement controlled against the standard of care, anterior cervical discectomy, and fusion. Under the IDE, randomized controlled trials comparing both 1 and 2 level cervical disease were completed. The sponsor designed the initial trial as noninferiority; however, using adaptive methodology, superiority could be claimed in the 2-level investigation.

REVIEWING HEALTHCARE ECONOMICS

Healthcare economics are critical in medical decision making and reimbursement practices. Once both cost- and quality-adjusted life-year (QALY) are known for each patient, the incremental cost-effectiveness ratio is calculated. Willingness-to-pay is controversial, but a commonly cited guideline considers interventions costing below 20 000 $/QALY strongly cost effective and more than 100 000 $/QALY as not cost effective.

CONCLUSION

While large Food and Drug Administration IDE studies are often besieged by complex statistical considerations and calculations, it is fundamentally important that clinicians understand at least the terminology and basic concepts on a practical level.

Focal hypermobility observed in cervical arthroplasty with Mobi-C

In recent decades cervical arthroplasty, or cervical disc replacement, has been steadily increasing in popularity as a procedure for the treatment of degenerative pathologies of the cervical spine. This is based on an evolving body of literature that documents superior outcomes in cervical disc replacement over fusion, for both single and double level pathologies, in well selected patients. One of the more recent and popular implants currently on the market is the Mobi-C cervical artificial disc (LDR Medical; Troyes, France). In this paper we report on two cases where focal hypermobility was observed following total disc replacement using the Mobi-C cervical artificial disc. This is followed by a discussion as to potential contributing factors to this hypermobility in relation to both implant design, and operative technique, suggesting potential changes that might prevent this in future patients.

Biomechanical Analysis of Two-level Cervical Disc Replacement With a Stand-alone U-shaped Disc Implant

STUDY DESIGN

Biomechanical study using a three-dimensional nonlinear finite element model.

OBJECTIVE

To analyze biomechanical changes with three prostheses based on two-level arthroplasty and to verify the biomechanical efficiency of dynamic cervical implants (DCIs) with a stand-alone U-shaped structure.

SUMMARY OF BACKGROUND DATA

Few studies have compared biomechanical behavior of various prostheses as they relate with clinical results after two-level total disc replacement.

METHODS

Three arthroplasty devices Mobi-C, porous coated motion (PCM), and DCI were inserted at the C4-C6 disc space and analyzed. Displacement loading was applied to the center of the endplate at the C3 level to simulate flexion and extension motions.

RESULTS

The motion distributions in extension with DCI and in flexion with DCI and Mobi-C were relatively close to that in the intact model. Mobi-C and PCM obviously increased the combined extension range of motion at the index levels, but both resulted in about 45% decrease in extension moment. DCI showed a trend in strain energy similar to that of healthy discs. PCM exhibited a facet joint stress distribution almost similar to that of the intact model. DCI did not generate significant overloading at cartilage between the index levels, whereas the maximum facet joint stress increased with Mobi-C was about 39%. The maximum stress on a ultrahigh molecular-weight-polyethylene core was above the yield stress (42.43 MPa for Mobi-C and 30.94 MPa for PCM).

CONCLUSION

Each prosthesis shows its biomechanical advantages and disadvantages. However, DCI has the capacity to preserve motion and store energy under external loading, similar to the behavior of normal discs. Compared with Mobi-C, both DCI and PCM showed a lower stress at cartilage between index levels, which may avoid facet joint degeneration to some extent. Such a well-controlled arthroplasty device with a stand-alone structure may be a potential candidate and needs to be investigated in future studies.

LEVEL OF EVIDENCE

5.

The prevalence of heterotopic ossification among patients after cervical artificial disc replacement: A systematic review and meta-analysis

BACKGROUND

Prevalence estimates of heterotopic ossification (HO) following cervical artificial disc replacement (ADR) varied widely in previous studies. We conducted a systematic review and meta-analysis to summarize its point prevalence.

METHODS

Electronic searches of PubMed, Web of Science, Embase, and Cochrane Library databases were conducted to identify studies that reported prevalence of HO. Definitions of HO and severe HO were based on McAfee grading system. Random-effects model was used to estimate the pooled prevalence. We conducted subgroup analyses according to the different length of follow-up time, and performed univariate metaregression analyses to explore the effects of potential variables on the overall prevalence.

RESULTS

A total of 38 studies were included in this study. The pooled data showed that the prevalence of HO after cervical ADR within the 1 to 2 years, 2 to 5 years, and 5 to10 years of follow-up was 38.0% (95% confidence interval [CI], 30.2%-46.5%), 52.6% (95% CI, 43.1%-61.9%), and 53.6% (95% CI, 40.0%-66.7%), respectively, while the prevalence of severe HO was 10.9% (95% CI, 9.0%-13.2%), 22.2% (95% CI, 15.5%-30.7%), and 47.5% (95% CI, 30.0%-65.8%), respectively. Follow-up time was positively associated with the prevalence of severe HO (P < .01), and the 1-month growth of mean follow-up went with 0.63% increase of severe HO.

CONCLUSION

This meta-analysis reported data on the prevalence of HO and severe HO after cervical ADR, and provided information on its process of development. These should be useful to enable surgeons and patients to gain a better understanding of HO after cervical ADR.

[Analysis of the results of total cervical disc arthroplasty using a M6-C prosthesis: a multicenter study]

Cervical spondylosis and intervertebral disc (IVD) degeneration are the most common cause for compression of the spinal cord and/or its roots. Total IVD arthroplasty, as a modern alternative to surgical treatment of IVD degeneration, is gaining popularity in many neurosurgical clinics around the world. Aim - the study aim was to conduct a multicenter analysis of cervical spine arthroplasty with an IVD prosthesis M6-C ('Spinal Kinetics', USA).

MATERIAL AND METHODS

The study included 112 patients (77 males and 35 females). All patients underwent single-level discectomy with implantation of the artificial IVD prosthesis M6-C. The follow-up period was up to 36 months. Dynamic assessment of the prosthesis was based on clinical parameters (pain intensity in the cervical spine and upper extremities (visual analog scale - VAS); quality of life (Neck Disability Index - NDI)); and subjective satisfaction with the results of surgical treatment (Macnab scale) and instrumental data (range of motion in the operated spinal motion segment, degree of heterotopic ossification (McAfee-Suchomel classification), and time course of degenerative changes in the adjacent segments).

Comparative Analysis between Total Disc Replacement and Posterior Foraminotomy for Posterolateral Soft Disc Herniation with Unilateral Radiculopathy : Clinical and Biomechanical Results of a Minimum 5 Years Follow-up

OBJECTIVE

To compare the clinical outcomes and biomechanical effects of total disc replacement (TDR) and posterior cervical foraminotomy (PCF) and to propose relative inclusion criteria.

METHODS

Thirty-five patients who underwent surgery between 2006 and 2008 were included. All patients had single-level disease and only radiculopathy. The overall sagittal balance and angle and height of a functional segmental unit (FSU; upper and lower vertebral body of the operative lesion) were assessed by preoperative and follow-up radiographs. C2-7 range of motion (ROM), FSU, and the adjacent segment were also checked.

RESULTS

The clinical outcome of TDR (group A) was tended to be superior to that of PCF (group B) without statistical significance. In the group A, preoperative and postoperative upper adjacent segment level motion values were 8.6±2.3 and 8.4±2.0, and lower level motion values were 8.4±2.2 and 8.3±1.9. Preoperative and postoperative FSU heights were 37.0±2.1 and 37.1±1.8. In the group B, upper level adjacent segment motion values were 8.1±2.6 and 8.2±2.8, and lower level motion values were 6.5±3.3 and 6.3±3.1. FSU heights were 37.1±2.0 and 36.2±1.8. The postoperative FSU motion and height changes were significant (p<0.05). The patient's satisfaction rates for surgery were 88.2% in group A and 88.8% in group B.

CONCLUSION

TDR and PCF have favorable outcomes in patients with unilateral soft disc herniation. However, patients have different biomechanical backgrounds, so the patient's biomechanical characteristics and economic status should be understood and treated using the optimal procedure.

Heterotopic ossification following single-level anterior cervical discectomy and fusion: results from the prospective, multicenter, historically controlled trial comparing allograft to an optimized dose of rhBMP-2

OBJECTIVE

Heterotopic ossification (HO) has been reported following total hip, knee, cervical, and lumbar arthroplasty, as well as following posterolateral lumbar fusion using recombinant human bone morphogenetic protein–2 (rhBMP-2). Data regarding HO following anterior cervical discectomy and fusion (ACDF) with rhBMP-2 are sparse. A subanalysis was done of the prospective, multicenter, investigational device exemption trial that compared rhBMP-2 on an absorbable collagen sponge (ACS) versus allograft in ACDF for patients with symptomatic single-level cervical degenerative disc disease.

METHODS

To assess differences in types of HO observed in the treatment groups and effects of HO on functional and efficacy outcomes, clinical outcomes from previous disc replacement studies were compared between patients who received rhBMP-2/ACS versus allograft. Rate, location, grade, and size of ossifications were assessed preoperatively and at 24 months, and correlated with clinical outcomes.

RESULTS

Heterotopic ossification was primarily anterior in both groups. Preoperatively in both groups, and including osteophytes in the target regions, HO rates were high at 40.9% and 36.9% for the rhBMP-2/ACS and allograft groups, respectively (p = 0.350). At 24 months, the rate of HO in the rhBMP-2/ACS group was higher than in the allograft group (78.6% vs 59.2%, respectively; p < 0.001). At 24 months, the rate of superior-anterior adjacent-level Park Grade 3 HO was 4.2% in both groups, whereas the rate of Park Grade 2 HO was 19.0% in the rhBMP-2/ACS group compared with 9.8% in the allograft group. At 24 months, the rate of inferior-anterior adjacent-level Park Grade 2/3 HO was 11.9% in the rhBMP-2/ACS group compared with 5.9% in the allograft group. At 24 months, HO rates at the target implant level were similar (p = 0.963). At 24 months, the mean length and anteroposterior diameter of HO were significantly greater in the rhBMP-2/ACS group compared with the allograft group (p = 0.033 and 0.012, respectively). Regarding clinical correlation, at 24 months in both groups, Park Grade 3 HO at superior adjacent-level disc spaces significantly reduced range of motion, more so in the rhBMP-2/ACS group. At 24 months, HO negatively affected Neck Disability Index scores (excluding neck/arm pain scores), neurological status, and overall success in patients in the rhBMP-2/ACS group, but not in patients in the allograft group.

CONCLUSIONS

Implantation of rhBMP-2/ACS at 1.5 mg/ml with polyetheretherketone spacer and titanium plate is effective in inducing fusion and improving pain and function in patients undergoing ACDF for symptomatic single-level cervical degenerative disc disease. At 24 months, the rate and dimensions (length and anteroposterior diameter) of HO were higher in the rhBMP-2/ACS group. At 24 months, range of motion was reduced, with Park Grade 3 HO in both treatment groups. The impact of Park Grades 2 and 3 HO on Neck Disability Index success, neurological status, and overall success was not consistent among the treatment groups. The study data may offer a deeper understanding of HO after ACDF and may pave the way for improved device designs.

Clinical trial registration no.: IDE# G060021; data compared with pooled data from control arms of IDE# G010188/NCT00642876 and IDE# G000123/NCT00437190 (www.clinicaltrials.gov).

Five-year clinical results of cervical total disc replacement compared with anterior discectomy and fusion for treatment of 2-level symptomatic degenerative disc disease: a prospective, randomized, controlled, multicenter investigational device exemption clinical trial

OBJECTIVE

The purpose of this study was to report the outcome of a study of 2-level cervical total disc replacement (Mobi-C) versus anterior cervical discectomy and fusion (ACDF). Although the long-term outcome of single-level disc replacement has been extensively described, there have not been previous reports of the 5-year outcome of 2-level cervical disc replacement.

METHODS

This study reports the 5-year results of a prospective, randomized US FDA investigational device exemption (IDE) study conducted at 24 centers in patients with 2-level, contiguous, cervical spondylosis. Clinical outcomes at up to 60 months were evaluated, including validated outcome measures, incidence of reoperation, and adverse events. The complete study data and methodology were critically reviewed by 3 independent surgeon authors without affiliation with the IDE study or financial or institutional bias toward the study sponsor.

RESULTS

A total of 225 patients received the Mobi-C cervical total disc replacement device and 105 patients received ACDF. The Mobi-C and ACDF follow-up rates were 90.7% and 86.7%, respectively (p = 0.39), at 60 months. There was significant improvement in all outcome scores relative to baseline at all time points. The Mobi-C patients had significantly more improvement than ACDF patients in terms of Neck Disability Index score, SF-12 Physical Component Summary, and overall satisfaction with treatment at 60 months. The reoperation rate was significantly lower with Mobi-C (4%) versus ACDF (16%). There were no significant differences in the adverse event rate between groups.

CONCLUSIONS

Both cervical total disc replacement and ACDF significantly improved general and disease-specific measures compared with baseline. However, there was significantly greater improvement in general and disease-specific outcome measures and a lower rate of reoperation in the 2-level disc replacement patients versus ACDF control patients.

Clinical trial registration no. NCT00389597 (clinicaltrials.gov)

Four-year results of a prospective single-arm study on 200 semi-constrained total cervical disc prostheses: clinical and radiographic outcome

OBJECTIVE Recent studies have described encouraging outcomes after cervical total disc replacement (cTDR), but there are also critical debates regarding the long-term effects of heterotopic ossification (HO) and the prevalence of adjacent-level degeneration. The aim in this paper was to provide 4-year clinical and radiographic outcome results on the activ C disc prosthesis. METHODS A total of 200 subjects underwent single-level activ C (Aesculap AG) implantation between C-3 and C-7 for the treatment of symptomatic degenerative disc disease. Clinical and radiographic assessments were performed preoperatively, intraoperatively, at discharge, and again at 6 weeks, 6 months, 1 year, 2 years, and 4 years. Radiographic evaluations were done by an independent core laboratory using a specific software for quantitative motion analysis. RESULTS Neck Disability Index (NDI) and visual analog scale (VAS) score for neck and arm pain decreased significantly from baseline to the 4-year follow-up. The mean improvement for NDI was 20, for VAS severity and frequency of neck pain 26.4 and 28, and for VAS severity and frequency of arm pain 30.7 and 35.1, respectively. The neurological situation improved for the majority of patients (86.4%); 76.1% of cases were asymptomatic. Subsequent surgical interventions were reported in 7% of the cases, including device removals in 3%. In 2.5% a subsidence greater than 3 mm was recorded; 1 of these cases also had a migration greater than 3 mm. No device displacement, expulsion, disassembly, loose or fractured device, osteolysis, or facet joint degeneration at the index level was observed. Segmental lordotic alignment changed from -2.4° preoperatively to -6.2° at 4 years, and postoperative height was maintained during the follow-up. Advanced HO (Grade III and IV) was present in 27.1% of the cases; 82.4% showed segmental mobility. A progression of radiographic adjacent-segment degeneration occurred in 28.2%, but only 4.5% required surgical treatment. CONCLUSIONS The activ C is a safe and effective device for cervical disc replacement confirming the encouraging results after cTDR. Clinical trial registration no.: NCT02492724 ( clinicaltrials.gov ).

Adjacent segment degeneration and disease following cervical arthroplasty: a systematic review and meta-analysis

BACKGROUND CONTEXT

Cervical arthroplasty is an increasingly popular alternative for the treatment of cervical radiculopathy and myelopathy. This technique preserves motion at the index and adjacent disc levels, avoiding the restraints of fusion and potentially minimizing adjacent segment pathology onset during the postoperative period.

PURPOSE

This study aimed to identify all prospective studies reporting adjacent segment pathology rates for cervical arthroplasty.

STUDY DESIGN/SETTING

Systematic review and meta-analysis were carried out.

PATIENT SAMPLE

Studies reporting adjacent segment degeneration (ASDegeneration) and adjacent segment disease (ASDisease) rates in patients who underwent cervical arthroplasty comprised the patient sample.

OUTCOME MEASURES

Outcomes of interest included reported ASDegeneration and ASDisease events after cervical arthroplasty.

METHODS

We conducted a MEDLINE, SCOPUS, and Web of Science search for studies reporting ASDegeneration or ASDisease following cervical arthroplasty. A meta-analysis was performed to calculate effect summary values, 95% confidence intervals (CIs), Q values, and I(2) values. Forest plots were constructed for each analysis group.

RESULTS

Of the 1,891 retrieved articles, 32 met inclusion criteria. The patient incidence of ASDegeneration and ASDisease was 8.3% (95% CI 3.8%-12.7%) and 0.9% (95% CI 0.1%-1.7%), respectively. The rate of ASDegeneration and ASDisease at individual levels was 10.5% (95% CI 6.1%-14.9%) and 0.2% (95% CI -0.1% to 0.5%), respectively. Studies following patients for 12-24 months reported a 5.1% (95% CI 2.1%-8.1%) incidence of ASDegeneration and 0.2% (95% CI 0.1%-0.2%) incidence of ASDisease. Conversely, studies following patients for greater than 24 months reported a 16.6% (5.8%-27.4%) incidence of ASDegeneration and 2.6% (95% CI 1.0%-4.2%) of ASDisease. This identified a statistically significant increase in ASDisease diagnosis with lengthier follow-up. Additionally, 1- and 2-level procedures resulted in a 7.4% (95% CI 3.3%-11.4%) and15.6% (95 CI-9.2% to 40.4%) incidence of ASDegeneration, respectively. Although there was an 8.2% increase in ASDegeneration following 2-level operations (relative to 1-level), it did not reach statistical significance. We were unable to analyze ASDisease incidence following 2-level arthroplasty (too few cases), but 1-level operations resulted in an ASDisease incidence of 0.8% (95% CI 0.1%-1.5%).

CONCLUSIONS

This review represents a comprehensive estimation of the actual incidence of ASDegeneration and ASDisease across a heterogeneous group of surgeons, patients, and arthroplasty techniques. Our investigation should serve as a framework for individual surgeons to understand the impact of various cervical arthroplasty techniques, follow-up duration, and surgical levels on the incidence of ASDegeneration and ASDisease during the postoperative period.

Seven-year cost-effectiveness of ProDisc-C total disc replacement: results from investigational device exemption and post-approval studies

OBJECTIVE The purpose of this study was to evaluate the 7-year cost-effectiveness of cervical total disc replacement (CTDR) versus anterior cervical discectomy and fusion (ACDF) for the treatment of patients with single-level symptomatic degenerative disc disease. A change in the spending trajectory for spine care is to be achieved, in part, through the selection of interventions that have been proven effective yet cost less than other options. This analysis complements and builds upon findings from other cost-effectiveness evaluations of CTDR through the use of long-term, patient-level data from a randomized study. METHODS This was a 7-year health economic evaluation comparing CTDR versus ACDF from the US commercial payer perspective. Prospectively collected health care resource utilization and treatment effects (quality-adjusted life years [QALYs]) were obtained from individual patient-level adverse event reports and SF-36 data, respectively, from the randomized, multicenter ProDisc-C total disc replacement investigational device exemption (IDE) study and post-approval study. Statistical distributions for unit costs were derived from a commercial claims database and applied using Monte Carlo simulation. Patient-level costs and effects were modeled via multivariate probabilistic analysis. Confidence intervals for 7-year costs, effects, and net monetary benefit (NMB) were obtained using the nonparametric percentile method from results of 10,000 bootstrap simulations. The robustness of results was assessed through scenario analysis and within a parametric regression model controlling for baseline variables. RESULTS Seven-year follow-up data were available for more than 70% of the 209 randomized patients. In the base-case analysis, CTDR resulted in mean per-patient cost savings of $12,789 (95% CI $5362-$20,856) and per-patient QALY gains of 0.16 (95% CI -0.073 to 0.39) compared with ACDF over 7 years. CTDR was more effective and less costly in 90.8% of probabilistic simulations. CTDR was cost-effective in 99.8% of sensitivity analysis simulations and generated a mean incremental NMB of $20,679 (95% CI $6053-$35,377) per patient at a willingness-to-pay threshold of $50,000/QALY. CONCLUSIONS Based on this modeling evaluation, CTDR was found to be more effective and less costly over a 7-year time horizon for patients with single-level symptomatic degenerative disc disease. These results are robust across a range of scenarios and perspectives and are intended to support value-based decision making.

Subsequent surgery rates after cervical total disc replacement using a Mobi-C Cervical Disc Prosthesis versus anterior cervical discectomy and fusion: a prospective randomized clinical trial with 5-year follow-up

OBJECTIVE Cervical total disc replacement (TDR) has been shown in a number of prospective clinical studies to be a viable treatment alternative to anterior cervical discectomy and fusion (ACDF) for the treatment of symptomatic degenerative disc disease. In addition to preserving motion, evidence suggests that cervical TDR may result in a lower incidence of subsequent surgical intervention than treatment with fusion. The goal of this study was to evaluate subsequent surgery rates up to 5 years in patients treated with TDR or ACDF at 1 or 2 contiguous levels between C-3 and C-7. METHODS This was a prospective, multicenter, randomized, unblinded clinical trial. Patients with symptomatic degenerative disc disease were enrolled to receive 1- or 2-level treatment with either TDR as the investigational device or ACDF as the control treatment. There were 260 patients in the 1-level study (179 TDR and 81 ACDF patients) and 339 patients in the 2-level study (234 TDR and 105 ACDF patients). RESULTS At 5 years, the occurrence of subsequent surgical intervention was significantly higher among ACDF patients for 1-level (TDR, 4.5% [8/179]; ACDF, 17.3% [14/81]; p = 0.0012) and 2-level (TDR, 7.3% [17/234]; ACDF, 21.0% [22/105], p = 0.0007) treatment. The TDR group demonstrated significantly fewer index- and adjacent-level subsequent surgeries in both the 1- and 2-level cohorts. CONCLUSIONS Five-year results showed treatment with cervical TDR to result in a significantly lower rate of subsequent surgical intervention than treatment with ACDF for both 1 and 2 levels of treatment. Clinical trial registration no.: NCT00389597 ( clinicaltrials.gov ).

Prospective, Randomized Comparison of Cervical Total Disk Replacement Versus Anterior Cervical Fusion: Results at 48 Months Follow-up

STUDY DESIGN

This was a prospective, randomized, controlled multicenter trial.

OBJECTIVE

The purpose of this study was to compare clinical outcomes at 4-year follow-up of patients receiving cervical total disk replacement (TDR) with those receiving anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

ACDF has been the traditional treatment for symptomatic disk degeneration. Several studies found single-level TDR to be as safe and effective as ACDF at ≥2 years follow-up.

METHODS

Patients from 23 centers were randomized in a 2:1 ratio with 164 receiving the investigational device (Mobi-C Cervical Disc Prosthesis) and 81 receiving ACDF using an anterior plate and allograft. Patients were evaluated preoperatively and 6 weeks, 3, 6, 12, 18, 24, 36, and 48 months postoperatively. Outcome assessments included a composite success score, Neck Disability Index, visual analog scales assessing neck and arm pain, patient satisfaction, major complications, subsequent surgery, segmental range of motion, and adjacent-segment degeneration.

RESULTS

The composite success rate was similar in the 2 groups at 48-month follow-up. Mean Neck Disability Index, visual analog scale, and SF-12 scores were significantly improved in early follow-up in both groups with improvements maintained throughout 48 months. On some measures, TDR had significantly greater improvement during early follow-up. At no follow-up were TDR scores significantly worse than ACDF scores. Subsequent surgery rate was significantly higher for ACDF compared with TDR (9.9% vs. 3.0%, P<0.05). Range of motion was maintained with TDR having a mean baseline value of 8 degrees compared with 10 degrees at 48 months. The incidence of adjacent-segment degeneration was significantly higher with ACDF at inferior and superior segments compared with TDR (inferior: 50% vs. 30%, P<0.025; superior: 53% vs. 34%, P<0.025).

CONCLUSIONS

Significant improvements were observed in pain and function. TDR patients maintained motion and had significantly lower rates of reoperation and adjacent-segment degeneration compared with ACDF. This study supports the safety and efficacy of TDR in appropriately selected patients.

Cervical spine alignment in disc arthroplasty: should we change our perspective?

PURPOSE

The alignment at the cervical spine has been considered a determinant of degeneration at the adjacent disc, but this issue in cervical disc replacement surgery is poorly explored and discussed in this patient population. The aim of this systematic review is to compare anterior cervical fusion and total disc replacement (TDR) in terms of preservation of the overall cervical alignment and complications.

METHODS

A systematic review of the current literature was performed, together with the evaluation of the methodological quality of all the retrieved studies.

RESULTS

In most of the retrieved studies, a tendency towards a more postoperative kyphotic alignment in TDR was reported. The reported mean complication rate was of 12.5 % (0-66.2 %). Complications associated with cervical prosthesis included heterotopic ossification, device migration, mechanical instability, failure, implant removal, reoperations and revision.

CONCLUSIONS

Even though cervical disc arthroplasty leads to similar outcomes compared to arthrodesis in the middle term follow-up, no evidence of superiority of cervical TDR is available up to date. We understand that the overall cervical alignment after TDR tends towards the loss of lordosis, but only longer follow-up can determine its influence on the clinical results.

Comparison of Clinical Outcomes of 1- and 2-Level Total Disc Replacement: Four-Year Results From a Prospective, Randomized, Controlled, Multicenter IDE Clinical Trial

STUDY DESIGN

A prospective, randomized, multicenter Food and Drug Administration Investigation Device Exemption study using total disc replacement as surgical treatment of degenerative disc disease at 1 or 2 contiguous levels of the cervical spine.

OBJECTIVE

To evaluate the safety and effectiveness of total disc replacement at single or 2 contiguous levels through 48 months of follow-up.

SUMMARY OF BACKGROUND DATA

Cervical total disc replacement has been shown to be a safe and effective alternative to anterior cervical discectomy and fusion at 24 months. Its motion-preserving capabilities may avoid accelerating adjacent segment pathology and thereby lower the rate of associated complications.

METHODS

Patients were randomized in a 2:1 ratio (total disc replacement [TDR]: anterior cervical discectomy and fusion [ACDF]) at 24 sites. Ultimately, 164 patients received TDR at 1 level and 225 patients received TDR at 2 contiguous levels. An additional 24 patients (15 one-level, 9 two-level) were treated with TDR as training cases.Outcome measures included neck disability index, visual analogue scale neck and arm pain, Short Form 12-item Health Survey (SF-12) Mental Composite Score (MCS) and Physical Composite Score (PCS), range of motion, major complication rates, and secondary surgery rates. Patients received follow-up examinations at regular intervals through 4 years after surgery.

RESULTS

Preoperative characteristics were statistically similar for the 1- and 2-level patient groups. Four-year follow-up rates were 83.1% (1-level) and 89.0% (2-level). There was no statistically significant difference between 1- and 2-level TDR groups for all clinical outcome measures. Both TDR groups experienced significant improvement at each follow-up when compared with preoperative scores. One case of migration was reported in the 2-level TDR group.

CONCLUSION

A 4-year post hoc comparison of 1- and 2-level TDR patients concurrently enrolled in a 24-center, Food and Drug Administration Investigation Device Exemption clinical trial indicated no statistical differences between groups in clinical outcomes, overall complication rates, and subsequent surgery rates.

LEVEL OF EVIDENCE

1.

Postoperative nonsteroidal antiinflammatory drugs and the prevention of heterotopic ossification after cervical arthroplasty: analysis using CT and a minimum 2-year follow-up

OBJECT Heterotopic ossification (HO) after cervical arthroplasty is not uncommon and may cause immobility of the disc. To prevent HO formation, study protocols of clinical trials for cervical arthroplasty undertaken by the US FDA included perioperative use of nonsteroidal antiinflammatory drugs (NSAIDs). However, there are few data supporting the use of NSAIDs to prevent HO after cervical arthroplasty. Therefore, this study aimed to evaluate the efficacy of NSAIDs in HO formation and clinical outcomes. METHODS Consecutive patients who underwent 1- or 2-level cervical arthroplasty with a minimum follow-up of 24 months were retrospectively reviewed. All patients were grouped into 1 of 2 groups, an NSAID group (those patients who had used NSAIDs postoperatively) and a non-NSAID group (those patients who had not used NSAIDs postoperatively). The formation of HO was detected and classified using CT in every patient. The incidence of HO formation, disc mobility, and clinical outcomes, including visual analog scale (VAS) scores of neck and arm pain, neck disability index (NDI) scores, and complications were compared between the two groups. Furthermore, a subgroup analysis of the patients in the NSAID group, comparing the selective cyclooxygenase (COX)-2 to nonselective COX-2 NSAID users, was also conducted for each of the above-mentioned parameters. RESULTS A total of 75 patients (mean age [± SD] 46.71 ± 9.94 years) with 107 operated levels were analyzed. The mean follow-up duration was 38.71 ± 9.55 months. There were no significant differences in age, sex, and levels of arthroplasty between the NSAID and non-NSAID groups. There was a nonsignificantly lower rate of HO formation in the NSAID group than the non-NSAID group (47.2% vs. 68.2%, respectively; p = 0.129). During follow-up, most of the arthroplasty levels remained mobile, with similar rates of immobile discs in the NSAID and non-NSAID groups (13.2% and 22.7%, respectively; p = 0.318). Furthermore, there was a nonsignificantly lower rate of HO formation in the selective COX-2 group than the nonselective COX-2 group (30.8% vs 52.5%, respectively; p = 0.213). The clinical outcomes, including VAS neck, VAS arm, and NDI scores at 24 months postoperatively, were all similar in the NSAID and non-NSAID groups, as well as the selective and nonselective COX-2 groups (all p > 0.05). CONCLUSIONS In this study there was a trend toward less HO formation and fewer immobile discs in patients who used postoperative NSAIDs after cervical arthroplasty than those who did not, but this trend did not reach statistical significance. Patients who used selective COX-2 NSAIDs had nonsignificantly less HO than those who used nonselective COX-2 NSAIDs. The clinical outcomes were not affected by the use of NSAIDs or the kinds of NSAIDs used (selective vs nonselective COX-2). However, the study was limited by the number of patients included, and the efficacy of NSAIDs in the prevention of HO after cervical arthroplasty may need further investigation to confirm these results.

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.

ISASS Policy Statement - Cervical Artificial Disc

Morgan Lorio, MD, FACS, Chair, ISASS Task Force on Coding & Reimbursement

The ISASS Task Force reached out to Domagoj Coric, MD to provide a timely summation on cervical disc arthroplasty given his special interest and recent IASP championship of this innovative technology to insure enhanced spine patient access. The ISASS Task Force is pleased with this step towards published ISASS societal policy and applauds Dr. Coric's effort; if ISASS is to continue to succeed we must continually harness the voluntary talents and energies of our members with gratitude.

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.

The Mobi-C cervical disc for one-level and two-level cervical disc replacement: a review of the literature

BACKGROUND

Cervical disc arthroplasty (CDA) is a novel motion-preserving procedure that is an alternative to fusion. The Mobi-C disc prosthesis, one of many Food and Drug Administration (FDA)-approved devices for CDA, is the only FDA-approved prosthesis for two-level CDA. Hence, it may allow for improved outcomes compared with multilevel fusion procedures.

PURPOSE

To critically assess the available literature on CDA with the Mobi-C prosthesis, with a focus on two-level CDA.

METHODS

All clinical articles involving the Mobi-C disc prosthesis for CDA through September 1, 2014 were identified on Medline. Any paper that presented Mobi-C CDA clinical results was included. Study design, sample size, length of follow-up, use of statistical analysis, quality of life outcome scores, conflict of interest, and complications were recorded.

RESULTS

Fifteen studies were included that investigated Mobi-C CDA, only one of which was a level Ib randomized control trial. All studies included showed non-inferiority of one-level Mobi-C CDA to one-level anterior cervical discectomy and fusion (ACDF). Only one study analyzed outcomes of one-level versus two-level Mobi-C CDA, and only one study analyzed two-level Mobi-C CDA versus two-level ACDF. In comparison with other cervical disc prostheses, the Mobi-C prosthesis is associated with higher rates of heterotopic ossification (HO). Studies with conflicts of interest reported lower rates of HO. Adjacent segment degeneration or disease, along with other complications, were not assessed in most studies.

CONCLUSION

One-level Mobi-C CDA is non-inferior, but not superior, to one-level ACDF for patients with cervical degenerative disc disease. The Mobi-C CDA procedure is associated with high rates of HO. Two-level Mobi-C CDA may be superior to two-level ACDF. However, insufficient evidence exists, thereby mandating a need for unbiased, well-designed prospective studies with well-defined outcomes in the future.

Fusion-nonfusion hybrid construct versus anterior cervical hybrid decompression and fusion: a comparative study for 3-level cervical degenerative disc diseases

STUDY DESIGN

A retrospective analysis.

OBJECTIVE

This study aimed to compare the safety and efficacy between the fusion-nonfusion hybrid construct (HC: anterior cervical corpectomy and fusion plus artificial disc replacement, ACCF plus cADR) and anterior cervical hybrid decompression and fusion (ACHDF: anterior cervical corpectomy and fusion plus discectomy and fusion, ACCF plus ACDF) for 3-level cervical degenerative disc diseases (cDDD).

SUMMARY OF BACKGROUND DATA

The optimal anterior technique for 3-level cDDD remains uncertain. Long-segment fusion substantially induced biomechanical changes at adjacent levels, which may lead to symptomatic adjacent segment degeneration. Hybrid surgery consisting of ACDF and cADR has been reported with good results for 2-level cDDD. In this context, ACCF combining with cADR may be an alternative to ACHDF for 3-level cDDD.

METHODS

Between 2009 and 2012, 28 patients with 3-level cDDD who underwent HC (n=13) and ACHDF (15) were retrospectively reviewed. Clinical assessments were based on Neck Disability Index, Japanese Orthopedic Association disability scale, visual analogue scale, Japanese Orthopedic Association recovery rate, and Odom criteria. Radiological analysis included range of motion of C2-C7 and adjacent segments and cervical lordosis. Perioperative parameters, radiological adjacent-level changes, and the complications were also assessed.

RESULTS

HC showed better Neck Disability Index improvement at 12 and 24 months, as well as Japanese Orthopedic Association and visual analogue scale improvement at 24 months postoperatively (P<0.05). HC had better outcome according to Odom criteria but not significantly (P>0.05). The range of motion of C2-C7 and adjacent segments was less compromised in HC (P<0.05). Both 2 groups showed significant lordosis recovery postoperatively (P<0.05), but no difference was found between groups (P>0.05). The incidence of adjacent-level degenerative changes and complications was higher in ACHDF but not significantly (P>0.05).

CONCLUSION

HC may be an alternative to ACHDF for 3-level cDDD due to the equivalent or superior early clinical outcomes, less compromised C2-C7 range of motion, and less impact at adjacent levels.

LEVEL OF EVIDENCE

3.

Clinical and radiographic analysis of an artificial cervical disc: 7-year follow-up from the Prestige prospective randomized controlled clinical trial

Object

The authors assess the long-term safety and efficacy of cervical disc replacement with the Prestige Cervical Disc in a prospective, randomized, multicenter trial at 7 years of follow-up.

Methods

At 31 investigational sites, 541 patients with single-level cervical disc disease with radiculopathy were randomized to 1 of 2 treatment groups: 276 investigational group patients underwent anterior cervical discectomy and arthroplasty with the Prestige disc, and 265 control group patients underwent anterior cervical discectomy and fusion. Clinical outcomes included Neck Disability Index, the 36-Item Short-Form Health Survey, and neck and arm pain scores. Radiographs were assessed for angle of motion and fusion. Clinical and radiographic outcomes were evaluated preoperatively, intraoperatively, and at 1.5, 3, 6, 12, 24, 36, 60, and 84 months.

Results

Of the 541 patients treated, 395 patients (73%; 212 investigational and 183 control patients) completed 7 years of clinical follow-up. Significant improvements achieved by 1.5 months in both groups were sustained at 7 years. In the investigational group, mean Neck Disability Index improvements from preoperative scores were 38.2 and 37.5 at 60 and 84 months, respectively. In the control group, the corresponding means were 33.8 and 31.9. The differences between the investigational and control groups at the 60-month and 84-month periods were significant (p = 0.014 and 0.002, respectively). The overall rates of maintenance or improvement in neurological status in the investigational group were significantly higher: 92.2% and 88.2% at 60 months and 84 months, respectively, compared with 85.7% and 79.7% in the control group (p = 0.017 and 0.011, respectively). At 84 months, the percentage of working patients in the investigational group was 73.9%, and in the control group, 73.1%. Postoperatively, the implant effectively maintained average angular motion of 6.67° at 60 months and 6.75° at 84 months. Cumulative rates for surgery at the index level were lower (p < 0.001) in the investigational group (11 [4.8%] of 276) when compared with the control group (29 [13.7%] of 265) (based on life-table method), and there were statistical differences between the investigational and control groups with specific regard to the rate of subsequent revision and supplemental fixation surgical procedures. Rates for additional surgical procedures that involved adjacent levels were lower in the investigational group than in the control group (11 [4.6%] of 276 vs 24 [11.9%] of 265, respectively).

Conclusions

Cervical disc arthroplasty has the potential for preserving motion at the operated level while providing biomechanical stability and global neck mobility and may result in a reduction in adjacent-segment degeneration. The Prestige Cervical Disc maintains improved clinical outcomes and segmental motion after implantation at 7-year follow-up. Clinical trial registration no. NCT00642876 (ClinicalTrials.gov).

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.

Multi-level cervical disc arthroplasty (CDA) versus single-level CDA for the treatment of cervical disc diseases: a meta-analysis

PURPOSE

Cervical disc arthroplasty (CDA) was developed to treat cervical degenerated disc diseases with the advantages of preserving the kinematics of the functional spinal unit. However, the safety and reliability of multi-level CDA are still controverted when comparing to the single-level CDA. It has shown unclear benefits in terms of clinical results, functional recovery, heterotopic ossification, and the need for secondary surgical procedures. The purpose of this study is to estimate the effectiveness of multi-level cervical arthroplasty over single-level CDA for the treatment of cervical spondylosis and disc diseases.

METHODS

To compare the studies of multi-level CDA versus single-level CDA in patients with cervical spondylosis that reported at least one of the following outcomes: functionality, neck pain, arm pain, quality of life, reoperation and incidence of heterotopic ossification, electronic databases (Medline, Embase, Pubmed, Cochrane library, and Cochrane Central Register of Controlled Trials) were searched. No language restrictions were used. Two authors independently assessed the methodological quality of included studies and extracted the relevant data.

RESULTS

Out of Eight cohorts that were included in the study, four were prospective cohorts and the other four were retrospective. The results of the meta-analysis indicated that there was no significant difference in neck disability index scores, neck visual analog scale (VAS), arm VAS, morbidity of reoperation, heterotopic ossification, and parameters of living quality when comparing multi-level CDA with single-level CDA at 1 and 2 years follow-up postoperatively (p > 0.05).

CONCLUSIONS

The meta-analysis revealed that the outcomes and functional recovery of patients performed with multi-level CDA are equivalent to those with single-level CDA, which suggests the multi-level CDA is as effective and safe as single-level invention for the treatment of cervical spondylosis. Nonetheless, more well-designed studies with large groups of patients are needed to provide further evidence for the benefit and reliability of multi-level CDA in the treatment of cervical disc diseases.

Three-dimensional motion analysis of the cervical spine for comparison of anterior cervical decompression and fusion versus artificial disc replacement in 17 patients

Object

Cervical arthroplasty with an artificial disc (AD) has emerged as an alternative to anterior cervical discectomy and fusion (ACDF) for the management of cervical spondylosis. This study aims to provide 3D motion analysis data comparing patients after ACDF and AD replacement.

Methods

Ten patients who underwent C5–6 ACDF and 7 who underwent C5–6 AD replacement were enrolled. Using biplanar fluoroscopy and a model-based track technique (accurate up to 0.6 mm and 0.6°), motion analysis of axial rotation and flexion-extension of the neck was performed. Three nonoperative segments (C3–4, C4–5, and C6–7) were assessed for both intervertebral rotation (coronal, sagittal, and axial planes) and facet shear (anteroposterior and mediolateral).

Results

There was no difference in total neck motion comparing ACDF and AD replacement for neck extension (43.3° ± 10.2° vs 44.3° ± 12.6°, p = 0.866) and rotation (36.0° ± 6.5° vs 38.2° ± 9.3°, p = 0.576). For extension, when measured as a percentage of total neck motion, there was a greater amount of rotation at the nonoperated segments in the ACDF group than in the AD group (p = 0.003). When comparing specific motion segments, greater normalized rotation was seen in the ACDF group at C3–4 (33.2% ± 4.9% vs 26.8% ± 6.6%, p = 0.036) and C6–7 (28.5% ± 6.7% vs 20.5% ± 5.5%, p = 0.009) but not at C4–5 (33.5% ± 6.4% vs 31.8% ± 4.0%, p = 0.562). For neck rotation, greater rotation was observed at the nonoperative segments in the ACDF group than in the AD group (p = 0.024), but the differences between individual segments did not reach significance (p ≥ 0.146). Increased mediolateral facet shear was seen on neck extension with ACDF versus AD replacement (p = 0.008). Comparing each segment, C3–4 (0.9 ± 0.5 mm vs 0.4 ± 0.1 mm, p = 0.039) and C4–5 (1.0 ± 0.4 mm vs 0.5 ± 0.2 mm, p = 0.022) showed increased shear while C6–7 (1.0 ± 0.4 mm vs 1.0 ± 0.5 mm, p = 0.767) did not.

Conclusions

This study illustrates increased motion at nonoperative segments in patients who have undergone ACDF compared with those who have undergone AD replacement. Further studies will be required to examine whether these changes contribute to adjacent-segment disease.

Does sagittal position of the CTDR-related centre of rotation influence functional outcome? Prospective 2-year follow-up analysis

PURPOSE

Recent studies describe significant rates of heterotopic ossification (HO) after cervical total disc replacement (CTDR). Little is known about the reasons, and one aspect that requires further in vivo investigation is the biomechanical alteration after CTDR and the role of the implant-related centre of rotation (CORi) in particular. The role of the sagittal position of the CORi on functional outcome in two versions of a semi-constrained disc prosthesis with sagittally different CORi is the topic of this study.

METHODS

Patients were candidates for single-level CTDR between C3 and C7 who suffered from CDDD and received a standard or flat version of activ C™ (Aesculap AG, Tuttlingen). Clinical and radiographic assessments were determined preoperatively, intraoperatively, at discharge and again at 6 weeks, 6 months, 1 and 2 years. Radiographic examinations were performed independently using specialized quantitative motion analysis software.

RESULTS

Clinical outcome improved significantly regarding NDI as well as VAS on neck and arm pain with no differences in mean improvement by study group. Segmental angle measures show a significantly better lordotic alignment for both groups after surgery, but the degree of correction achieved is higher in the flat group. Correlation analysis proves that the more anterior the CORi is positioned, the higher the lordotic correction is achieved (Pearson rho -0.385). Segmental ROM decreased in the standard group but was maintained for flat implants. At present, our data do not demonstrate a correlation between CORi and ROM at 2 years. Two years after surgery, severe HO grade III-IV was present in 31.6 % standard and 13.1 % flat cases with significant differences. Grouping according to HO severity showed comparable sagittal positions of CORi for flat implants but a more posterior position in the severe HO group for standard implants.

CONCLUSIONS

Our results confirm the influence of CORi location on segmental alignment, kinematics and HO for a semi-constrained CTDR, but it also indicates a multifactorial process.

Total disc replacement

Total disc replacement (TDR) (partial disc replacement will not be described) has been used in the lumbar spine since the 1980s, and more recently in the cervical spine. Although the biomechanical concepts are the same and both are inserted through an anterior approach, lumbar TDR is conventionally indicated for chronic low back pain, whereas cervical TDR is used for soft discal hernia resulting in cervicobrachial neuralgia. The insertion technique must be rigorous, with precise centering in the disc space, taking account of vascular anatomy, which is more complex in the lumbar region, particularly proximally to L5-S1. All of the numerous studies, including prospective randomized comparative trials, have demonstrated non-inferiority to fusion, or even short-term superiority regarding speed of improvement. The main implant-related complication is bridging heterotopic ossification with resulting loss of range of motion and increased rates of adjacent segment degeneration, although with an incidence lower than after arthrodesis. A sufficiently long follow-up, which has not yet been reached, will be necessary to establish definitively an advantage for TDR, particularly in the cervical spine.

Heterotopic ossification in cervical total disk replacement: a finite element analysis

Heterotopic ossification is one of the possible complications following cervical total disk replacement. Although there are numerous hypotheses regarding the etiology of heterotopic ossification, the main causes of heterotopic ossification remain unknown. In this study, we hypothesize that heterotopic ossification formation is related to external loading in the cervical vertebrae after total disk replacement. A two-dimensional finite element model of a cervical vertebra treated by total disk replacement in the sagittal plane was developed. The bone adaptation process of heterotopic ossification was simulated based on strain energy density under both compressive and shear forces. Different types of heterotopic ossification formation were analyzed according to the directions of forces. Two distinct types of heterotopic ossification following cervical total disk replacement were predicted, which was consistent with previous clinical studies. Type 1 heterotopic ossification was observed in the posterior upper part of the vertebra under compressive forces, while type 2 heterotopic ossification was detected mostly in the anterior upper part under shear forces. In addition, heterotopic ossification formation enhanced the strain energy distribution, which is known to be related to bone remodeling. This article presents the effects of different mechanical loading conditions on the occurrence of heterotopic ossification following cervical total disk replacement, and the results may be useful for the design of artificial disks that minimize heterotopic ossification.

Comparison of one-level microendoscopy laminoforaminotomy and cervical arthroplasty in cervical spondylotic radiculopathy: a minimum 2-year follow-up study

BACKGROUND

This study aims to compare the perioperative parameters and clinical results between microendoscopy laminoforaminotomy (MELF) and cervical arthroplasty (CA) in the treatment of one-level cervical spondylotic radiculopathy in a retrospective study.

METHODS

From 2003 to 2007, a total of 97 patients with one-level cervical spondylotic radiculopathy were treated. Forty-five patients underwent CA. Fifty-two patients underwent MELF. Patient demographics and operative data were collected with a minimum 2-year follow-up. Perioperative parameters were compared. Clinical assessment in terms of neck disability index (NDI), short form (SF)-36, and visual analogue scale (VAS) of arm pain and neck pain was performed prior to surgery and at 1.5, 3, 6, 12, and 24 months after surgery.

RESULTS

Fluoroscopy time (CA, 60.3 s; MELF, 12.1 s; P < 0.01) and surgical time (CA, 95.1 min; MELF, 24.0 min; P < 0.01) were significantly longer in the CA cases. Shorter hospitalized days (CA, 1.1 days; MELF, 0.13 days; P < 0.01) and less estimated blood loss (EBL; CA, 75.8 ml; MELF, 31.9 ml; P < 0.01) were observed in the MELF group. Both CA and MELF groups showed significant improvement in NDI, VAS of neck pain and arm pain, and SF-36 (P < 0.05 for each) at 1.5, 3, 6, 12, and 24 months after surgery, but there was no significant difference between them (P > 0.05).

CONCLUSIONS

As alternatives of anterior cervical decompression and fusion (ACDF), both CA and MELF can produce satisfactory clinical outcomes. MELF has the additional benefits of less blood loss, less surgical time, less X-ray time, and shorter hospital stay.

Differences between arthroplasty and anterior cervical fusion in two-level cervical degenerative disc disease

PURPOSE

Although arthroplasty is an accepted option for two-level disease, there is a paucity of data regarding outcomes of two-level cervical arthroplasty. The current study was designed to determine differences between two-level cervical arthroplasty and anterior fusion.

METHODS

Seventy-seven consecutive patients who underwent two-level anterior cervical operations for degenerative disc disease were divided into the arthroplasty (37 patients) and fusion (40 patients) groups. Clinical outcomes were measured by Visual Analogue Scale (VAS) of neck and arm pain, Japanese Orthopedic Association (JOA) scores, and Neck Disability Index (NDI). Every patient was evaluated by radiography and computed tomography for fusion or detection of heterotopic ossification.

RESULTS

Thirty-seven patients (with 74 levels of Bryan discs) were compared with 40 patients who had two-level anterior fusion (mean follow-up of 39.6 ± 6.7 months). There was no difference in sex, but the mean age of the arthroplasty group was significantly younger (52.1 ± 9.1 vs. 63.0 ± 10.6 years, p < 0.001). The mean estimated blood loss was similar (p = 0.135), but the mean operation time was longer in the arthroplasty group (315.5 ± 82.0 versus 224.9 ± 61.8 min, p < 0.001). At 24 months post-operation, the arthroplasty group had increased their range of motion than pre-operation (23.5° versus 20.1°, p = 0.018). There were significant improvements in neck or arm VAS, JOA scores, and NDI in both groups. However, there were no differences in clinical outcomes or adverse events between the two groups.

CONCLUSIONS

Clinical outcomes of two-level arthroplasty and anterior cervical fusion are similar 39.6 months after surgery. Cervical arthroplasty preserves mobility at the index levels without increased adverse effects.

Cervical arthroplasty with Discover prosthesis: clinical outcomes and analysis of factors that may influence postoperative range of motion

PURPOSE

The aim of this current study was to analyze the clinical outcomes after Discover cervical disc replacement and its effects on maintaining cervical lordosis and range of motion (ROM). The possible factors influencing postoperative ROM were analyzed.

METHOD

27 men and 28 women with a mean age of 46.4 ± 8.7 years were prospectively followed up for 2 years. Clinical outcomes were assessed using Japanese Orthopedic Association (JOA), Neck Disability Index (NDI), visual analog scale (VAS) and Odom's criteria. Radiographic information including segment and overall alignment, functional spinal unit (FSU) and overall ROM, and disc heights were prospectively collected during the follow-up. The correlations between the postoperative FSU ROM at last follow-up and influencing factors were analyzed.

RESULTS

Mean NDI, JOA and VAS scores showed statistical improvements at last follow-up. Anterior migration of the prosthesis was detected in six cases. Heterotopic ossification was observed in ten patients. Mean FSU angle, endplate angle of the treated level and mean overall cervical alignment were all improved significantly at last follow-up (P < 0.001). However, mean FSU ROM of the treated segment significantly decreased postoperatively (P = 0.008), while mean overall ROM showed no significant differences. A significant correlation was found between preoperative FSU ROM and postoperative FSU ROM by the Pearson correlation coefficient (r = 0.325, P = 0.034). Multiple linear regression analysis confirmed that preoperative FSU ROM contributed independently to a model with a coefficient of determination of 0.37 (P = 0.034).

CONCLUSIONS

In the 2 years follow-up, the Discover cervical disc arthroplasty has provided satisfactory clinical outcomes. It was able to substantially restore segment and overall cervical alignment while partially maintaining segment and overall cervical ROM. Additionally, we found that postoperative FSU ROM positively correlated with preoperative FSU ROM.

Cervical adjacent segment pathology following fusion: Is it due to fusion?

Adjacent segment pathology affects 25% of patients within ten years of anterior cervical diskectomy and fusion (ACDF). Laboratory studies demonstrate fused segments increase adjacent level stress including elevated intradiscal pressure and increased range of motion. Radiographic adjacent segment pathology (RASP) has been associated to ACDF in multiple statistically significant studies. Randomized controlled trials (RCTs) comparing anterior cervical discectomy and arthroplasty (ACDA) and ACDF have confirmed ACDF accelerates RASP. The question of greatest clinical interest is whether ACDA, artificial disc surgery, results in fewer adjacent level surgeries than ACDF. Current RCT follow up results reveal only non statistically significant trends favoring ACDA yet the post operative periods are only two to four years. Statistically significant increased RASP in ACDF patients however is already documented. The RCT patients’ average ages are in the mid forties with an expected longevity of up to forty more years. Early statistically significant increased RASP in the ACDF patients supports our prediction that given sufficient follow up of ten or more years, fusion will lead to statistically significant higher rate of adjacent level surgery compared to artificial disc surgery.