Analysis of the three United States Food and Drug Administration investigational device exemption cervical arthroplasty trials

Biomechanical analysis of single and multi-level artificial disc replacement (ADR) in cervical spine using multi-scale loadings: A finite element study

Artificial disc replacement (ADR) is a clinical procedure used to diagnose cervical degenerative disc disease, preserving range of motion (ROM) at the fixation level and preventing adjacent segment degeneration (ASD). This study analyzed the biomechanics of ADR by examining range of motion (ROM), stress levels in bone and implants, and strain in the bone-implant interface using multi-scale loadings. The study focused on single- and double-level patients across various loading scales during physiological motions within the cervical spine. Results showed increased ROM in single-level and double-level fixations during physiological loadings, while ROM decreased at the adjacent level of fixation with the intact cervical spine model. The Prodisc-Implant metal endplate experienced a maximum von Mises stress of 432 MPa during axial rotation, confirming the long durability and biomechanical performance of the bone-implant interface.

Prospective Multicenter Trial of Cervical Arthroplasty with the ROTAIO® Cervical Disc Prosthesis

STUDY DESIGN

Clinical observational study.

OBJECTIVE

The ROTAIO® cervical disc prosthesis is a novel unconstrained implant with a variable center of rotation aiming at physiological motion. The objective of this multicenter prospective trial was to evaluate clinical outcome and complications within 2 years.

MATERIAL AND METHODS

120 patients (72 females and 48 males with median age of 43.0 years [23-60 yrs] underwent ACDA (ROTAIO®, SIGNUS Medical, Alzenau, Germany) and were prospectively followed for 24 months. Preoperative complaints were mainly associated with radiculopathy (n = 104) or myelopathy (n=16). There were 108 monosegmental and 12 bisegmental procedures including 6 hybrid constructs. Clinical outcome was evaluated at 3, 12 and 24 months in 100%, 96% and 77% of the cohort by VAS, NDI, WL-26, Patient`s Satisfaction Index (PSI), SF-36, Nurick Score, mJOA, Composite Success Rate, complications, patient`s overall satisfaction and analgesics use.

RESULTS

Highly significant clinical improvements were observed according to NDI and VAS (P < .0001 (arm); P < .001 (neck); P = .002 (head)) at all time points. Analgetic use could be reduced in 87.1 to 95.2%. Doctor`s visits have been reduced in 93.8% after 24 months. Patient`s overall satisfaction was high with 78.4 to 83.5% of patients. The composite success rate was 77.5% after 12 months and 76.9% after 24 months. There were no major complications in this series. Slight subsidence of the prosthesis was observed in 2 patients and 3 patients demonstrated fusion after 24 months. 2 patients developed symptomatic foraminal stenosis, so that implant removal and fusion was performed resulting in a revision rate of 1.7% in 2 years.

CONCLUSION

The ROTAIO® cervical disc prosthesis is a safe and efficient treatment option for symptomatic degenerative disc disease demonstrating highly significant clinical improvement and high patient`s overall satisfaction with very low revision rates at 2 years.

Multilevel Cervical Disk Arthroplasty: Moving Beyond Two Levels

Cervical disk arthroplasty (CDA) is well-studied for 1-level and 2-level cervical pathology. There is an increasing trend towards its utilization for greater than 2-level disease as an alternative to the gold standard, anterior cervical discectomy and fusion (ACDF). The number of high-level, prospective studies or randomized trials regarding multilevel CDA is limited but continues to grow as the procedure gains popularity. In appropriately indicated patients with multilevel disease caused by disk herniations or spondylosis without extensive facet arthropathy, CDA shows promising results. Multilevel CDA should be avoided in patients with prior spinal trauma, significant degenerative spondylolisthesis with translation, arthrodesis without mobility, severely incompetent facet joints, ossification of the posterior longitudinal ligament, or kyphotic deformity. With overall similar risk profiles to ACDF but lower theoretical rates of pseudarthrosis and adjacent segment disease, multilevel CDA has been shown to preserve, or perhaps even increase, preoperative cervical range of motion. There are negligible differences in postoperative neck and arm pain, VAS scores, modified Japanese Orthopaedic Association scores, and Neck Disability Index scores when comparing multilevel CDA and ACDF. Despite current indications for multilevel CDA largely being based on single and 2-level data, careful patient selection is critical. Expansion of indications can be expected as literature continues to emerge regarding outcomes and complications in multilevel CDA, as well as with improvements in prosthesis design.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Prospective, multicenter study of 2-level cervical arthroplasty with a PEEK-on-ceramic artificial disc

OBJECTIVE

The purpose of this study was to evaluate the safety and efficacy of a PEEK-on-ceramic cervical total disc replacement (cTDR) device for the treatment of 2-level cervical disc disease with radiculopathy and/or myelopathy.

METHODS

The study was a prospective, nonrandomized, historically controlled FDA investigational device exemption trial evaluating the Simplify Cervical Artificial Disc for use at 2 levels. The anterior cervical discectomy and fusion (ACDF) control group was derived from a propensity score-matched (using subclassification) cohort of patients who participated in an earlier prospective trial in which similar indications were used. The follow-up duration was 24 months. The primary outcome was a 4-point composite success classification. Other validated clinical and radiographic assessments were also evaluated.

RESULTS

The investigational group (n = 182) was compared with patients who underwent ACDF (n = 170) in a historical control group using propensity score analysis. The overall composite success rate was statistically significantly greater in the cTDR group compared with the ACDF group (86.7% vs 77.1%; p < 0.05). The mean Neck Disability Index scores improved significantly in both groups, with cTDR significantly lower at some follow-up points. At the 24-month follow-up, a minimum 15-point improvement in Neck Disability Index scores was achieved in 92.9% of the cTDR group and 83.5% of the ACDF group (p > 0.05). In both groups, neck and arm pain scores improved significantly (p < 0.05) by 6 weeks and improvement was maintained throughout follow-up. Segmental range of motion was maintained at both treated segments in the cTDR group. MRI performed in the cTDR group at 24 months postoperatively found minimal changes in facet joint degeneration. The rate of subsequent surgical intervention was 2.2% in the cTDR group and 8.8% in the ACDF group.

CONCLUSIONS

This study adds to the growing body of literature supporting cTDR for 2-level cervical disc disease with radiculopathy or myelopathy. cTDR showed a superior overall success rate compared to ACDF, while maintaining motion. These results support that the Simplify disc is a viable alternative to ACDF in appropriately selected patients with 2-level cervical spondylosis.

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

Introduction

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

Methods and analysis

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

Discussion

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

Trial registration

ClinicalTrials.gov NCT04623593. Registered on 29 September 2020.

Supplementary Information

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

Anterior Bone Loss in Cervical Disc Arthroplasty Correlates with Increased Cervical Lordosis

OBJECTIVE

Although cervical disc arthroplasty (CDA) has reportedly been associated with similarly low incidences of complications to anterior cervical discectomy and fusion, the phenomenon of anterior bone loss (ABL) is unique to CDA and has only recently gained notice. This study thus aimed to investigate the incidence of ABL and its correlation with cervical alignment post-operation.

METHODS

Consecutive patients who received CDA for herniated disc or spondylosis were retrospectively reviewed. The development and extent of ABL was detected by comparison of preoperative and postoperative serial images for the relative position of the anterior vertebral body with the CDA devices and graded into 3 levels: grade 1 (minor bone loss), grade 2 (anterior portion of the vertebral body without exposure of the artificial disc), and grade 3 (anterior portion of the vertebral body with exposure of the device).

RESULTS

A total of 41 patients were analyzed with a mean follow-up of 24.1 months. Under serial radiologic examinations during follow-up, all patients (41 of 41 = 100%) had bone loss of various degrees, with grade 3 ABL the most common (30 of 41 = 73.1%). There were 8 and 3 patients who had grades 2 and 1 ABL, respectively. The changes of the Cobb angle (ΔCobb) trended towards higher grades of ABL.

CONCLUSIONS

During the mean follow-up of 2 years, ABL was a common radiologic finding. More than half of the patients (26 of 41, 63.4%) in the series gained cervical lordosis (ΔCobb >0) after CDA. These patients with increased cervical lordosis (ΔCobb >0) after CDA had higher grades of ABL.

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: Expanded Indications

Cervical total disc replacement (cTDR) is now a firm alternative to anterior cervical discectomy and fusion (ACDF) for degenerative disc disease (DDD). Robust level 1 data from Federal Drug Administration-approved clinical trials demonstrated that cTDR is in any case equally safe and effective compared with ACDF for 1- or 2-level DDD. Furthermore, from early postoperative to long-term follow-up of 10 to 15 years, cTDR rates superiorly in many primary clinical outcomes. According to the published literature, at least nine different cTDR devices share this consistent pattern. On the other hand, the surgical treatment of more than 2-level disc disease is haunted by an elusive paradox. It is easily understandable that 3- and 4-level ACDF, with the well-known associated limitations, is not the superlative intervention for a spine segment anatomically designed to provide motion, as cervical spine is. Furthermore, multilevel ACDF exacerbates many of the clinical and biomechanical complications related with single-level fusion. However, as cTDR is not immaculate of constraints and failures, its clinical safety and efficacy and cost-effectiveness in multilevel anterior compressive pathology need to be established. This article analyses the current available evidence supporting the expanded indication of cTDR to 3- and 4-level disc disease, either stand-alone or adjacent to fusion, from a less stringent European perspective.

Cervical Total Disc Replacement: Indications and Technique

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

Cervical disc arthroplasty for Klippel-Feil syndrome

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Adjacent-Segment Disease Following Spinal Arthroplasty

Intuitively, the introduction of artificial discs into spinal surgery offered the promise of reducing the incidence of adjacent segment (AS) reoperation compared with fusion. Several early clinical studies reported nonstatistically significant differences in AS disease between total disc replacement and fusion. Given the relatively low rate of AS reoperation (∼1%-2% per year) following fusion, any appropriately powered study designed to demonstrate a statistically significant difference compared with arthroplasty would require thousands of patients and/or long-term follow-up (>5 years). Therefore, these differences only become apparent with large study size or meta-analyses and longer follow-up.

Late complication of cervical disc arthroplasty: heterotopic ossification causing myelopathy after 10 years. Illustrative case

BACKGROUND

Heterotopic ossification (HO) is a well-documented complication of cervical disc arthroplasty (CDA), although it rarely causes adverse clinical effects. Despite high-grade HO possibly limiting segmental mobility, it is reportedly seldom associated with symptoms.

OBSERVATIONS

The authors report a case of a 46-year-old male patient who underwent hybrid CDA and anterior cervical discectomy and fusion for 3-level cervical disc herniation that caused myeloradiculopathy. The surgery was successful; the patient experienced nearly complete recovery postoperatively. The follow-up images, including computed tomography and magnetic resonance imaging scans, showed satisfactory decompression at the indexed levels without residual osteophytes or ossification of the posterior longitudinal ligament. However, 10 years later, the patient presented with symptomatic compressive myelopathy caused by severe HO that prompted a secondary surgery.

LESSONS

Although it is generally reported in the literature that HO is clinically innocuous, in this patient, it gradually and progressively developed and caused myelopathy, requiring a secondary surgery. Symptomatic HO can be expected over time, and patients with a high risk of HO deserve long-term follow-up after CDA. Further investigations are warranted to corroborate these risk factors, including multilevel calcified disc herniation, severe spondylosis, and suboptimal placement of the device during primary CDA surgery.

The Effect of T1-Slope in Spinal Parameters After Cervical Disc Arthroplasty

BACKGROUND

Although patients with cervical kyphosis are not ideal candidates for cervical disc arthroplasty (CDA), there is a paucity of data on patients with a straight or slightly lordotic neck.

OBJECTIVE

To correlate cervical lordosis, T1-slope, and clinical outcomes of CDA.

METHODS

The study retrospectively analyzed 95 patients who underwent 1-level CDA and had 2-yr follow-up. They were divided into a high T1-slope (≥28°) group (HTSG, n = 45) and a low T1-slope (<28°) group (LTSG, n = 50). Cervical spinal alignment parameters, including T1-slope, cervical lordosis (C2-7 Cobb angle), and segmental mobility (range of motion [ROM]) at the indexed level, were compared. The clinical outcomes were also assessed.

RESULTS

The mean T1-slope was 28.1 ± 7.0°. After CDA, the pre- and postoperative segmental motility remained similar and cervical lordosis was preserved. All the clinical outcomes improved after CDA. The HTSG were similar to the LTSG in age, sex, segmental mobility, and clinical outcomes. However, the HTSG had higher cervical lordosis than the LTSG. Furthermore, the LTSG had increased cervical lordosis (ΔC2-7 Cobb angle), whereas the HTSG had decreased lordosis after CDA. Patients of the LTSG, who had more improvement in cervical lordosis, had a trend toward increasing segmental mobility at the index level (ΔROM) than the HTSG.

CONCLUSION

In this series, T1-slope correlated well with global cervical lordosis but did not affect the segmental mobility. After CDA, the changes in cervical lordosis correlated with changes in segmental mobility. Therefore, segmental lordosis should be cautiously preserved during CDA as it could determine the mobility of the disc.

Complications and Complication Avoidance With Cervical Total Disc Replacement

Complications with cervical arthroplasty can be generalized to errors in patient selection or surgical technique. Patients with advanced spondylosis or osteophytic disease, severe facet arthropathy, osteoporosis, sagittal deformity, or preoperative instability are poor candidates for arthroplasty and are more prone to complications. Poor surgical technique can result in subsidence, expulsion, and kyphosis, and it can contribute to heterotopic ossification. Additionally, all of the inherent complications from an anterior cervical approach may occur with cervical artificial disc placement. This article will focus on the complications uniquely associated with cervical arthroplasty.

In cervical arthroplasty, only prosthesis with flexible biomechanical properties should be used for achieving a near-physiological motion pattern

Background

In cervical arthroplasty, qualitative motion analysis generally investigates the position of the center of rotation (COR) before and after surgery. But is the pre-op COR suitable as reference? We believe that only a comparison against healthy individuals can answer whether a physiological motion pattern has been achieved. The aim of our study was to examine how the COR for flexion/extension after insertion of 3 biomechanically completely different types of disc prostheses compares to healthy volunteers, and whether and how prosthesis design contributes to a more natural or maybe even worse motion pattern.

Methods

In 15 healthy volunteers, MRI in flexion and in extension was taken, and the coordinates for the CORs (COR-HV) from C3 to C7 were determined. Then pre- and post-op flexion/extension x-rays from 30 patients with a one-level disc prosthesis underwent analysis for determination of COR from C3 to C7; 10 patients who received a Bryan, a Prestige STLP, or a Discover prosthesis were chosen, respectively. Change of post-op COR position was investigated in relation to the COR-HV.

Results

The pre-operative COR is not congruent with the COR found in healthy subjects and therefore cannot be used as reference for investigation whether a disc prosthesis resembles natural motion. However, the comparison with healthy individuals shows that prosthesis insertion can change the coordinates of the COR to any direction in all levels from C3/4 to C6/7 regardless of the operated segment. Prostheses with flexible biomechanical properties can contribute to shift the COR toward normal, but devices with unphysiological biomechanical design, like fixed ball socket designs, for instance, can make the motion pattern even worse.

Conclusions

Even if the small cohorts in our study do not allow strong conclusions, it seems that in cervical arthroplasty, the biomechanical concept of the prosthesis has a significant impact whether a near-physiological motion pattern can be achieved or not. As it is a rumor but not scientifically proven that prosthesis design has no influence on clinical outcome, surgeons should only choose devices with flexible biomechanical properties for disc replacement.

Comparing Predictors of Complications After Anterior Cervical Diskectomy and Fusion, Total Disk Arthroplasty, and Combined Anterior Cervical Diskectomy and Fusion-Total Disk Arthroplasty With a Minimum 2-Year Follow-Up

INTRODUCTION

Outcomes after anterior cervical diskectomy and fusion (ACDF) and cervical total disk arthroplasty (TDA) are satisfactory, but related morbidity and revision surgery rates are notable. This study sought to determine complication variations among ACDF, TDA, and combined ACDF-TDA as well as predictors of postoperative complications.

METHODS

Patients undergoing 1- to 2-level ACDF and/or TDA with at least a 2-year follow-up from 2009 to 2011 were identified from the Statewide Planning and Research Cooperative System database. Patient demographics, hospital-related parameters, mortality, and postoperative outcomes were compared, and their predictors were identified using multivariate logistic regression.

RESULTS

A total of 16,510 and 449 individuals underwent ACDF and cervical TDA, respectively, and 201 underwent ACDF-TDA. ACDF-TDA patients had the highest rates of cardiac complications and pulmonary embolism (PE) (P ≤ 0.006), whereas TDA patients had higher individual surgical and device/implant/internal fixation complications (P ≤ 0.025). ACDF-TDA patients experienced the lowest rate of revisions. Cervical TDA increased the odds of any surgical complications (OR = 2.5, P = 0.002), overall complications (OR = 1.57, P = 0.034), and revisions (OR = 2.29, P < 0.001). Deyo index predicted any medical/surgical complications (OR = 1.43 and 1.19, respectively). Female sex was associated with increased odds of readmission (OR 1.30, P < 0.001) but was protective against medical complications (OR = 0.81, P = 0.013).

DISCUSSION

Combined ACDF-TDA procedures were not associated with increases in 2-year individual or overall complications, readmissions, or revisions.

LEVEL OF EVIDENCE

Level 3-Therapeutic study.

Spine Fixation Hardware: An Update

OBJECTIVE. The purpose of this article is to provide a review of the imaging of spine fixation hardware. CONCLUSION. As the prevalence of neck and back pain continues to increase, so does the number of surgical procedures used to treat such pain. Accordingly, new techniques and hardware designs are used, and the hardware will be seen on postoperative imaging. It is critical that radiologists understand the appropriate imaging modalities for the assessment of spine fixation hardware, recognize the normal imaging appearance of such hardware, and be able to detect hardware-related complications.

Financial Aspects of Cervical Disc Arthroplasty: A Narrative Review of Recent Literature

Recently, there has been significant interest in understanding the cost-effectiveness of treatments in spine surgery as health care systems in the United States move toward value-based care and alternative payment models. Previous studies have shown comparable outcomes of cervical disc arthroplasty (CDA) and anterior cervical discectomy fusion; however, there is a lack of consensus on the cost-effectiveness of CDA to support full adoption. Evidence of the limitations of these cost-analysis studies also exists in the literature, including industry funding, potential selection bias, and varying methods of calculating value. The goal of this narrative review is to provide an overview of the cost-effectiveness of CDA compared with anterior cervical discectomy and fusion, and potential limitations with cost-analysis studies in spine surgery.

Cervical Arthroplasty: Long-Term Outcomes of FDA IDE Trials

STUDY DESIGN

Special Issues MIS/Navigation.

OBJECTIVES

Over the past decade, cervical total disc replacement has been established in numerous randomized clinical trials as an alternative to anterior cervical discectomy and fusion. The purpose of this review is to evaluate the long-term outcomes after cervical arthroplasty.

METHODS/RESULTS

Early outcomes (studies with 2-year follow-up) after arthroplasty established the efficacy of total disc replacement and, more recently, long-term studies have shown the durability of these good clinical outcomes. Biomechanical and clinical data have demonstrated that this motion preservation technology decreases adjacent-level stresses compared with fusion. Additionally, long-term outcomes as well as outcomes after multilevel arthroplasty have now established the role of arthroplasty in select patient populations, namely patients with 1- and 2-level spondylosis/stenosis causing radiculopathy from C3-7.

CONCLUSIONS

Data on adjacent segment deterioration and adjacent segment reoperation remains controversial but suggest a positive effect after arthroplasty. But these are multifactorial issues and we still do not fully understand all the factors affecting adjacent segment pathology and longer-term studies after arthroplasty will continue to address this issue.

Transcorporeal Tunnel Approach for Cervical Radiculopathy and Myelopathy: A Systematic Review and Meta-Analysis

OBJECTIVE

The transcorporeal tunnel approach is a relatively new alternative of anterior cervical decompression and fusion for the treatment of cervical radiculopathy and myelopathy, with its main presumed advantage being the preservation of the intervertebral space. The aim of the present article is to present the outcomes of the systematic review and meta-analysis regarding the short-term outcomes of this surgical technique.

METHODS

A systematic review and a meta-analysis using the random-effects method of the available studies were performed to assess the safety and efficiency of the transcorporeal tunnel approach for cervical radiculopathy and myelopathy.

RESULTS

In total, 15 eligible studies were identified, with a cumulative number of 254 patients. Pooled data yielded a complication rate of 0.053 and a failure rate of the technique of 0.081; a patient-reported favorable outcome of 0.94 was documented. The available data did not allow for a definite conclusion on the effects of the technique on the intervertebral space height.

CONCLUSIONS

Although technically challenging, like all minimally invasive methods, the transcorporeal tunnel approach seems to be a safe and efficient option for the treatment of cervical radiculopathy and myelopathy, presenting comparable outcome profiles to alternative open or less invasive techniques.

Optimization of Three-Level Cervical Hybrid Surgery to Prevent Adjacent Segment Disease: A Finite Element Study

Hybrid surgery (HS) allows surgeons to tailor fusion and arthroplasty in the treatment of multiple-level cervical disc degeneration. However, the decision making of selecting either ACDF or ADR for each level in three-level HS remains controversial and has not been fully investigated. This study was aimed to optimize three-level cervical hybrid constructs by systematically investigating their biomechanical properties and their effect on adjacent levels. A finite element model of cervical spine (C2–C7) was developed, and eight C3–C6 surgical models including six HS were constructed. The range of motion (ROM) in flexion, extension, lateral bending, and axial rotation under 2.0 Nm moments with 30 N follower load were simulated. The von Mises stress, strain energy at the adjacent intervertebral disc (IVD) and force at the adjacent facet were calculated. The ROM of the hybrid constructs and adjacent levels was close to that of the intact spine. HS with arthroplasty performed at C5-6 had better performance in terms of ROM reduction at the inferior adjacent level (C6-7). Moreover, C-D-D and 3ADR had best performance in reducing the von Mises stress and strain energy at C6-7. All HS reduced the facet burden at both C2-3 and C6-7 levels. However, the major drawback of HS revealed here is that the effect of C6-7 protection is at the cost of increased C2-3 IVD burden. In conclusion, we recommend C-D-D and 3ADR for patient with C3–C6 disc degeneration without predisposing C2-3 condition. C-C-D could be a good alternative with a lower medical cost. This analysis guides the decision making in three-level cervical HS before future cadaver studies or human clinical trials.

Assessing the Effects of Publication Bias on Reported Outcomes of Cervical Disc Replacement and Anterior Cervical Discectomy and Fusion: A Meta-Epidemiologic Study

BACKGROUND

There have been several clinical trials as well as observational studies that have compared the outcomes of different cervical disc replacement (CDR) devices with anterior cervical disc replacement and fusion (ACDF). Although the results of these studies have provided sufficient evidence for the safety of CDR, there is still a lack of consensus in terms of longer-term outcomes, with studies providing equivocal results for the 2 procedures. In the current study, we used a novel methodology, a meta-epidemiologic study, to investigate the impact of study characteristics on the observed effects in the literature on CDR and ACDF.

METHODS

Data were abstracted from available meta-analyses regarding author, study author, year, intervention events, control events, and sample size, as well as year and geographic location of each study within the meta-analyses. We grouped the studies based on median year of publication as well as the region of the submitting author(s). Odds ratios, 95% confidence intervals (CIs), and standard errors of individual studies were calculated based on the number of events and sample size for each arm (ACDF or CDR). Further, results of outcomes from individual studies were pooled and a meta-analysis was conducted. Ratio of odds ratio (ROR) was used to assess the impact of each of these factors on estimates of the study for CDR versus ACDF.

RESULTS

A total of 13 meta-analyses were analyzed after exclusions. Using the results from 10 meta-analyses, we found that studies published before 2012 reported significantly lower odds of a reoperation after CDR (vs. ACDF), compared with studies published after 2012 (ROR, 0.51; 95% CI, 0.38-0.67; P < 0.001). We did not observe a significant impact of study year on difference in estimates between CDR and ACDF for adjacent segment disease (ROR, 0.99; 95% CI, 0.64-1.55; P = 0.465). The region of submitting author was also found to have no impact on results of published studies.

CONCLUSIONS

These results indicate that there may be a publication bias regarding the year of publication, with earlier studies reporting lower reoperation rates for CDR compared with ACDF.

Radiographic measurements of cervical alignment, fusion and subsidence after ACDF surgery and their impact on clinical outcome

BACKGROUND

Some recent studies indicate correlations between cervical alignment and clinical outcome after anterior cervical discectomy and fusion (ACDF) surgery. However, there still are no established criteria for the interpretation of alignment, fusion and subsidence in relation to clinical outcome.

METHODS

A retrospective analysis of 208 radiographs of patients following ACDF with stand-alone PEEK cage implantation was performed. The measurements were obtained on plain radiographs in lateral and anteroposterior projections as well as flexion/extension radiographs. Cervical alignment was measured using the Gore, Laing and Cobb methods; fusion was evaluated by an assortment of radiographic hallmarks: the presence of bridging bone, the Cobb angle and the distances between the tips and bases of the spinous processes of the operated segments, respectively. For assessment of subsidence, we used the Mochida method in addition to ventral and dorsal segmental height reduction. Correlation analysis between the different radiological characteristics and clinical outcome at a minimum follow-up of 12 months was conducted.

RESULTS

Two hundred and eight patients were evaluated for alignment, fusion and subsidence. Cervical alignment using the Gore and Cobb methods correlated among each other, but failed to exhibit significant correlation with clinical outcome. Interpretation of fusion rates varied greatly (43.9 to 89.4%) depending on the criteria used. Pearson coefficients between radiographic presence of pseudarthrosis and the measurements of the spinous process distances (0.595; p < 0.001), the Cobb angles (0.187; p = 0.007) and the presence of bridging bone (0.224; p < 0.001) each exhibited statistical significance. None of the methods employed significantly correlated with clinical outcome. Regarding subsidence, we found rates of 62%, 48% and 27% using the Mochida, ventral and dorsal segmental height reduction assessment methods, respectively. Pearson correlations between pairs of Mochida/ventral (r = 0.39; p = 0.66) and Mochida/dorsal (r = 0.007; p = 0.921) height reduction assessment methods were weak and no significant correlation between subsidence rates and clinical outcome was shown.

CONCLUSION

All measured parameters varied depending in the measurement method used. This was most pronounced for fusion. There was a moderate positive correlation between neck pain and subsidence as measured by the Mochida method.

Clinical and Radiographic Outcome of Patients With Cervical Spondylotic Myelopathy Undergoing Total Disc Replacement

STUDY DESIGN

A nonrandomized, prospective, and single-center clinical trial.

OBJECTIVE

The aim of this study was to investigate the clinical and radiographic efficacy of ProDisc Vivo cervical total disc replacement (cTDR) in patients with clinical and radiographic documented cervical spondylotic myelopathy (CSM), due to degenerative changes at the index level.

SUMMARY OF BACKGROUND DATA

Decompression and fusion is still the gold standard in patients with cervical myelopathy. Very limited data are available regarding the application of cTDR in patients with clinical and radiological documented CSM in context of clinical and radiographic outcomes.

METHODS

Clinical outcome scores included the Neck Disability Index (NDI), Visual Analogue Scale (VAS), arm and neck pain self-assessment questionnaires as well as the Nurick grade and the Japanese Orthopaedic Association (JOA) score. The radiological outcome included the range of motion (ROM), the segmental and global (C2-C7) lordosis, and the occurrence of heterotopic ossifications.

RESULTS

Eighteen consecutive patients (10 males, 8 females) with documented clinical and radiological signs of myelopathy were included in this investigation. The study population had a mean age of 52.4 years and a follow-up period of 20.3 months in average (range 3-48 months). The mean range ROM of the index level stayed consistent with 6.8° preoperatively and 7.2° (P = 0.578) at the last follow-up; the global lordosis in neutral position changed from 3.5° to 14.2° significantly (P = 0.005) in mean. The JOA score improved from 11.3 to 16.6 (P < 0.001) as well as the NDI 36.7 to 10.3 (P < 0.001) and the VAS score from 5.7/6.1 (arm/neck) to 1.3/2.0 (P < 0.001/P < 0.001). The mean Nurick grade was 1.33 preoperatively and dropped down in all cases to Nurick grade of 0 (P < 0.001).

CONCLUSION

cTDR (with ProDisc Vivio) in patients with CSM yielded good clinical and radiographic outcomes and found as a reliable, safe, and motion-preserving surgical treatment option, although its indication is very limited due to numerous exclusion criteria.

LEVEL OF EVIDENCE

4.

NuNec™ Cervical Disc Arthroplasty Improves Quality of Life in Cervical Radiculopathy and Myelopathy: A 2-yr Follow-up

BACKGROUND

Anterior cervical disc replacement is an alternative to fusion for the treatment of selected cases of radiculopathy and myelopathy. We report clinical and radiological outcomes after disc replacement with the NuNec™ artificial cervical disc (Pioneer® Surgical Technology, Marquette, Michigan) with subgroup analysis.

OBJECTIVE

To review clinical and radiological outcomes after anterior cervical disc replacement with the NuNec™ artificial cervical disc.

METHODS

A consecutive case series of patients undergoing cervical disc replacement with the NuNec™ artificial disc was conducted. Clinical outcomes were assessed by questionnaires preoperatively and up to 2 yr postoperatively including neck and arm pain, Neck Disability Index, Euroqol 5-dimensions, and Short Form-36; x-rays from the same period were analyzed for range of movement and presence of heterotopic ossification.

RESULTS

A total of 44 NuNec™ discs were implanted in 33 patients. Clinical improvements were seen in all outcomes; significant improvements on the Neck Disability Index, Euroqol 5-dimensions, and physical domain of the Short Form-36 were maintained at 2 yr. There was a mean of 4° range of movement at the replacement disc level at 2 yr, a significant reduction from baseline; there was also progression in levels of heterotopic ossification. Complications included temporary dysphagia (10%) and progression of disease requiring foraminotomy (6%); no surgery for adjacent level disease was required. There was no significant difference in the outcomes of the radiculopathy and myelopathy groups.

CONCLUSION

Clinical outcomes using the NuNec™ disc replacement are comparable with other disc replacements. Although the range of movement is reduced, the reoperation rate is very low.

Recent advances in the management of cervical spondylotic myelopathy: bibliometric analysis and surgical perspectives

OBJECTIVE

Cervical spondylotic myelopathy (CSM) has become a prevalent cause of spinal cord dysfunction among the aging population worldwide. Although great strides have been made in spine surgery in past decades, the optimal timing and surgical strategy to treat CSM have remained controversial. In this article the authors aimed to analyze the current trends in studies of CSM and to summarize the recent advances of surgical techniques in its treatment.

METHODS

The PubMed database was searched using the keywords pertaining to CSM in human studies that were published between 1975 and 2018. Analyses of both the bibliometrics and contents, including the types of papers, authors, affiliations and countries, number of patients, and the surgical approaches were conducted. A systematic review of the literature was also performed with emphasis on the diagnosis and treatment of mild CSM.

RESULTS

A total of 1008 papers published during the span of 44 years were analyzed. These CSM studies mainly focused on the natural history, diagnosis, and treatment, and only a few prospective randomized trials were reported. For the authors and affiliations, there was a shift of clustering of papers toward Asian countries in the past decades. Regarding the treatment for CSM, there was an exponential growth of surgical series published, and there was a trend toward slightly more anterior than posterior approaches through the past decade. Patients with CSM had increased risks of neurological deterioration or spinal cord injury with nonoperative management. Because surgery might reduce the risks, and early surgery was likely to be correlated with better outcomes, there was a trend toward attention to mildly symptomatic CSM.

CONCLUSIONS

There is emerging enthusiasm for research on CSM worldwide, with more publications originating in Asian countries over the past few decades. The surgical management of CSM is evolving continuously toward early and anterior approaches. More prospective investigations on the optimal timing and choices of surgery are therefore needed.

Cervical disc arthroplasty for less-mobile discs

OBJECTIVE

The published clinical trials of cervical disc arthroplasty (CDA) have unanimously demonstrated the success of preservation of motion (average 7°-9°) at the index level for up to 10 years postoperatively. The inclusion criteria in these trials usually required patients to have evident mobility at the level to be treated (≥ 2° on lateral flexion-extension radiographs) prior to the surgery. Although the mean range of motion (ROM) remained similar after CDA, it was unclear in these trials if patients with less preoperative ROM would have different outcomes than patients with more ROM.

METHODS

A series of consecutive patients who underwent CDA at the level of C5-6 were followed up and retrospectively reviewed. The indications for surgery were medically refractory cervical radiculopathy, myelopathy, or both, caused by cervical disc herniation or spondylosis. All patients were assigned to 1 of 2 groups: a less-mobile group, which consisted of those patients who had an ROM of ≤ 5° at C5-6 preoperatively, or a more-mobile group, which consisted of patients whose ROM at C5-6 was > 5° preoperatively. Clinical outcomes, including visual analog scale, Neck Disability Index, and Japanese Orthopaedic Association Scale scores, were evaluated at each time point. Radiological outcomes were also assessed.

RESULTS

A total of 60 patients who had follow-up for more than 2 years were analyzed. There were 27 patients in the less-mobile group (mean preoperative ROM 3.0°) and 33 in the more-mobile group (mean ROM 11.7°). The 2 groups were similar in demographics, including age, sex, diabetes, and cigarette smoking. Both groups had significant improvements in clinical outcomes, with no significant differences between the 2 groups. However, the radiological evaluations demonstrated remarkable differences. The less-mobile group had a greater increase in ΔROM than the more-mobile group (ΔROM 5.5° vs 0.1°, p = 0.001), though the less-mobile group still had less segmental mobility (ROM 8.5° vs 11.7°, p = 0.04). The rates of complications were similar in both groups.

CONCLUSIONS

Preoperative segmental mobility did not alter the clinical outcomes of CDA. The preoperatively less-mobile (ROM ≤ 5°) discs had similar clinical improvements and greater increase of segmental mobility (ΔROM), but remained less mobile, than the preoperatively more-mobile (ROM > 5°) discs at 2 years postoperatively.

Evaluation of Current Trends in Treatment of Single-level Cervical Radiculopathy

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVES

The main objectives of this study were to identify epidemiological trends, differences, and complications in patients undergoing surgical treatment for single-level cervical radiculopathy (SLCR).

SUMMARY OF BACKGROUND DATA

SLCR that fails nonoperative management is effectively treated with either anterior cervical discectomy and fusion (ACDF), cervical disc replacement (CDR), or posterior cervical foraminotomy (PCF). Although studies have shown that all 3 options are clinically effective, trends in usage, differences in patient population, and differences in complications remain unknown.

MATERIALS AND METHODS

Patients who underwent either ACDF, CDR, or PCF in the treatment of SLCR from 2010 to 2016 were retrospectively reviewed using the National Surgical Quality Improvement Program (NSQIP) database. Demographic data consisted of sex, age, ASA class, body mass index, and inpatient/outpatient status. Complications included surgical site infection, pneumonia, reintubation, pulmonary embolism, deep vein thrombosis, readmissions, reoperations, operating time, and hospital length of stay. Utilization trends by year among the 3 procedures were also analyzed.

RESULTS

A total of 1102 patients with SLCR treated with single-level ACDF, CDR, or PCF were identified in NSQIP from 2010 to 2016. There was a relative increase in the number of CDR procedures (7.7%-16.1%) and a corresponding decrease in PCF procedures (20.3%-10.6%) without a significant effect on ACDF procedures (72.0%-73.3%). Patients who underwent CDR were younger and in a lower ASA class than those undergoing ACDF or PCF. Patients undergoing PCF were more likely to be treated as an outpatient. PCF procedures also had the shortest operating time and hospital length of stay. There were no significant differences in complications among the 3 procedures. Moreover, there were no significant trends in demographics or outcome measures.

CONCLUSIONS

ACDF remains the most common surgical treatment for patients with SLCR, and its utilization has remained consistent. Meanwhile, the increased utilization of CDR for the treatment of SLCR has resulted in a corresponding decrease in the utilization of PCF.

The Mobi-C® cervical disc and other devices for two-level disc replacement: overview of its safety and efficacy

INTRODUCTION

Cervical disc arthroplasty (CDA) has become an acceptable alternative for anterior cervical discectomy and fusion (ACDF) for a significant patient population with cervical radiculopathy and/or myelopathy secondary to degenerative changes in the cervical spine. There are sufficient mid- and long-term data supporting performance and safety of one-level CDA. With the success of single-level cervical CDA, considerable interest exists about CDA use for multilevel cervical degenerative disc disease (DDD). This review analyzes the safety and efficacy of two-level CDA for treatment of symptomatic cervical DDD with focus on the Mobi-C® Cervical Disc.

AREAS COVERED

This review summarizes previously published articles in a literature search using keywords: 'two-level-anterior cervical arthrodesis; two-level anterior cervical decompression and fusion (ACDF); two-level cervical disc arthroplasty (CDA); two-level cervical total disc replacement; two-level symptomatic degenerative disc disease (DDD); Mobi-C® disc'.

EXPERT OPINION

Two-level CDA with the Mobi-C® device demonstrated equivalent, and in certain aspects, favorable outcomes compared to ACDF for treatment of symptomatic cervical 2-level degenerative disc disease (DDD) indicating a satisfactory safety and efficacy profile.

Radiological and clinical outcomes of cervical disc arthroplasty for the elderly: a comparison with young patients

Background

This study aimed to investigate whether cervical disc arthroplasty (CDA) would be equally effective in elderly patients as in the young. The inclusion criteria of published clinical trials for CDA-enrolled patients covered the ages from 18 to 78 years. However, there was a paucity of data addressing the differences of outcomes between older and the younger patients.

Methods

A series of consecutive patients who underwent one- or two-level CDA were retrospectively reviewed. Patients at the two extreme ends of the age distribution (≥65 and ≤ 40 years) were selected for comparison. Clinical outcome parameters included visual analog scale (VAS) of neck and arm pain, neck disability index (NDI), and Japanese Orthopaedic Association (JOA) scores. Radiographic outcomes included range of motion (ROM) at the indexed level and evaluation of heterotopic ossification (HO) by computed tomography (CT). Complication profiles were also investigated.

Results

There were 24 patients in the elderly group (≥65 years old) and 47 patients in the young group (≤40 years old) with an overall mean follow-up of 28.0 ± 21.97 months. The elderly group had more two-level CDA, and thus the mean operative time was longer (239 vs. 179 min, p < 0.05) than the young group. Both groups had similarly significant improvement in clinical outcomes at the final follow-up. All the replaced disc segments remained mobile on post-operative lateral flexion and extension radiographs. However, the elderly group had a slight decrease in mean ROM (− 0.32° ± 3.93°) at the index level after CDA when compared to that of pre-operation. In contrast, the young group had an increase in mean ROM (+ 0.68° ± 3.60°). The complication profiles were not different, though a trend toward dysphagia was noted in the elderly group (p = 0.073). The incidence or severity (grading) of HO was similar between the two groups.

Conclusions

During the follow-up of two years, CDA was equally effective for patients over 65 years old and those under 40 years in clinical improvement. Although the elderly group demonstrated a small reduction of mean ROM after CDA, in contrast to the young group which had a small increase, the segmental mobility was well preserved at every indexed level for each group.

Clinical and Radiological Outcome of a New Total Cervical Disc Replacement Design

STUDY DESIGN

A nonrandomized, prospective, and single-center clinical trial of the ProDisc Vivo prosthesis.

OBJECTIVE

The aim of this study was to investigate the clinical and radiological results of a refined total cervical disc replacement (cTDR), the ProDisc Vivo, with two years of follow-up (FU). The incidence of implant-related complications was recorded as a secondary outcome variable.

SUMMARY OF BACKGROUND DATA

Previous generations of the ProDisc artificial cervical disc replacement generate high primary stability due to keel-based designs with opening of the anterior cortex during the implantation and subsequent high rates of heterotopic ossifications.

METHODS

Clinical outcome scores included the Neck Disability Index (NDI), Visual Analogue Scale (VAS), arm and neck pain self-assessment questionnaires. The radiological outcome included the range of motion (ROM) and the occurrence of heterotopic ossifications. The incidence of implant-related complications with new implant design was recorded as a secondary outcome variable.

RESULTS

A total of 55 patients received a single-level treatment with the ProDisc Vivo cTDR between C3/4 and C6/7, with a follow-up rate of 78%. The clinical outcome scores improved in all parameters significantly (P = 0.0001) (NDI: 68.3 → 17.4; VAS arm: 6.3 → 1.4; VAS neck: 4.9 → 1.6). The ROM of the index-segment did not show a significant change (P = 0.26) (7.9° → 9.2°). Heterotopic ossifications at the index segment was found as grade 0 in 58%, grade 1 in 22%, grade 2 in 10%, grade 3 (with functional impairment of the prosthesis) in 7%, and grade 4 in 3% of the cases. We observed three implant-related complications (5.5%), with two implant dislocations anteriorly and one low-grade infect.

CONCLUSION

cTDR with ProDisc Vivo demonstrated a significant and sustained improvement of all clinical outcome parameters. A less invasive implantation mechanism with lower primary stability of the cTDR might be a reason for a higher dislocation rate than the keel-based previous generation ProDisc C.

LEVEL OF EVIDENCE

4.

Effects of smoking on cervical disc arthroplasty

Objective

Cigarette smoking can adversely affect bone fusion in patients who undergo anterior cervical discectomy and fusion. However, there is a paucity of data on smoking among patients who have undergone cervical disc arthroplasty (CDA). The present study aimed to compare the clinical and radiological outcomes of smokers to those of nonsmokers following CDA.

Methods

The authors retrospectively reviewed the records of consecutive patients who had undergone 1- or 2-level CDA for cervical disc herniation or spondylosis and had a minimum 2-year follow-up. All patients were grouped into a smoking group, which consisted of those who had consumed cigarettes within 6 months prior to the CDA surgery, or a nonsmoking group, which consisted of those who had not consumed cigarettes at all or within 6 months of the CDA. Clinical outcomes were evaluated according to the visual analog scale for neck and arm pain, Neck Disability Index, Japanese Orthopaedic Association Scale, and Nurick Scale at each time point of evaluation. Radiological outcomes were assessed using radiographs and CT for multiple parameters, including segmental range of motion (ROM), neutral lordotic curve, and presence of heterotopic ossification (HO).

Results

A total of 109 patients completed at least 2 years of follow-up and were analyzed (mean follow-up 42.3 months). There were 89 patients in the nonsmoking group and 20 in the smoking group. The latter group was younger and predominantly male (both p < 0.05) compared to the nonsmoking group. The two groups had similar improvements in all clinical outcomes after CDA compared to preoperatively. Radiological evaluations were also very similar between the two groups, except for two factors. The smoking group had well-preserved segmental ROM after CDA at an average of 8.1° (both pre- and postoperation). However, while the nonsmoking group remained mobile, segmental ROM decreased significantly (8.2° to 6.9°, p < 0.05) after CDA. There was a trend toward more HO development in the nonsmoking group than in the smoking group, but the difference was without significance (59.6% vs 50.0%, p = 0.43).

Conclusions

During an average 3.5 years of follow-up after 1- and 2-level CDA, cigarette smokers and nonsmokers had similar improvements in clinical outcomes. Moreover, segmental mobility was slightly better preserved in smokers. Since smoking status did not negatively impact outcomes, CDA may be a reasonable option for selected patients who have smoked.

Abbreviations

ACDF = anterior cervical discectomy and fusion; ASD = adjacent-segment degeneration; CDA = cervical disc arthroplasty; FDA = Food and Drug Administration; HO = heterotopic ossification; JOA = Japanese Orthopaedic Association; NDI = Neck Disability Index; ROM = range of motion; VAS = visual analog scale.

The Option of Motion Preservation in Cervical Spondylosis: Cervical Disc Arthroplasty Update

Cervical disc arthroplasty (CDA), or total disc replacement, has emerged as an option in the past two decades for the management of 1- and 2-level cervical disc herniation and spondylosis causing radiculopathy, myelopathy, or both. Multiple prospective randomized controlled trials have demonstrated CDA to be as safe and effective as anterior cervical discectomy and fusion, which has been the standard of care for decades. Moreover, CDA successfully preserved segmental mobility in the majority of surgical levels for 5–10 years. Although CDA has been suggested to have long-term efficacy for the reduction of adjacent segment disease in some studies, more data are needed on this topic. Surgery for CDA is more demanding for decompression, because indirect decompression by placement of a tall bone graft is not possible in CDA. The artificial discs should be properly sized, centered, and installed to allow movement of the vertebrae, and are commonly 6 mm high or less in most patients. The key to successful CDA surgery includes strict patient selection, generous decompression of the neural elements, accurate sizing of the device, and appropriately centered implant placement.

Preclinical Comparison of Thermal Tissue Effects from Traditional Electrosurgery and a Low-Temperature Electrosurgical Device during Anterior Cervical Discectomy and Fusion

Background

Exposure of the anterior cervical spine requires dissection in proximity to critical neurovascular structures. Monopolar electrosurgical (ES) devices generate heat in contacted tissues, resulting in thermal damage and temperature change. This study examined depth of thermal injury and temperature change associated with use of a low-temperature electrosurgical device (LTD) compared to traditional electrosurgery during a cadaveric anterior cervical discectomy and fusion (ACDF) dissection.

Methods

ACDF was performed, using ES or LTD, on cervical spines (C3-4 and C4-5) from 2 fresh human cadavers with intact neck soft tissues and no history of surgery. Cadavers were maintained at 22-23°C, and fiber-optic temperature sensors (Neoptix, Québec City, Québec, Canada) were placed near relevant structures to measure changes during dissection. Depth of thermal injury was assessed by hematoxylin and eosin and Masson's trichrome histology of fixed tissue specimens.

Results

Use of the LTD resulted in a statistically significant reduction in temperature change at platysma (3.0 ± 1.04 vs. 11.41 ± 3.10°C, P = .003), carotid sheath (7.32 ± 1.13 vs. 15.57 ± 2.56°C, P = .007), and longus colli (6.11 ± 1.32 vs. 12.9 ± 3.62°C, P = .016) compared to ES. Temperature change at the trachea was similar between groups (6.06 ± 1.99 vs. 4.96 ± 1.89°C, P = .528). Histology showed that LTD produced less mean and maximal depth of thermal injury compared to ES (mean: 0.5 vs. 1.2 mm; max: 0.9 vs. 1.8 mm; P < .05).

Conclusions

The results of this pilot study demonstrate that anterior cervical spine exposure using an LTD reduces tissue temperature change and depth of thermal injury compared to ES.

Clinical Relevance

Although exploratory, these results suggest that use of an LTD during ACDF may reduce the extent of thermal tissue injury during dissection. Future studies in live animal models are warranted to determine if thermal injury is a potential cause of common exposure-related complications, such as dysphagia and dysphonia.

The Effect of Local Versus Intravenous Corticosteroids on the Likelihood of Dysphagia and Dysphonia Following Anterior Cervical Discectomy and Fusion: A Single-Blinded, Prospective, Randomized Controlled Trial

BACKGROUND

Dysphagia and dysphonia are the most common postoperative complications following anterior cervical discectomy and fusion (ACDF). Although most postoperative dysphagia is mild and transient, severe dysphagia can have profound effects on overall patient health and on surgical outcomes. The purpose of this study was to compare the efficacy of local to intravenous (IV) steroid administration during ACDF on postoperative dysphagia and dysphonia.

METHODS

This was a single-blinded, prospective, randomized clinical trial. Seventy-five patients undergoing ACDF with cervical plating were randomized into 3 groups: control (no steroid), IV steroid (10 mg of IV dexamethasone at the time of closure), or local steroid (40 mg of local triamcinolone). Patient-reported outcome measures (PROMs) were collected for dysphagia, dysphonia, and neck pain postoperatively for 1 year.

RESULTS

Patient demographics were similar. Postoperative day 1 PROMs showed significantly lower scores for dysphonia (p = 0.015) and neck pain (p = 0.034) in the local steroid group. At 2 weeks postoperatively, the local steroid cohort showed significantly decreased prevalence of severe dysphagia (Eating Assessment Tool-10 [EAT-10], severe dysphagia, p = 0.027) compared with the control and IV steroid groups. Both steroid groups had significantly less severe dysphagia when compared with the control group at the 6-week and 3-month time points. At 1 year postoperatively, both steroid groups had significantly reduced dysphagia rates (p = 0.014) compared with the control group.

CONCLUSIONS

Both local and IV steroid administration after cervical plating in ACDF yielded better PROMs for dysphagia compared with a control group. This finding is particularly evident in the reduced number of patients who reported severe dysphagia symptoms following ACDF with local steroid application within the first 2 postoperative weeks. Future studies should attempt to stratify dysphagia severity when reporting outcomes related to anterior cervical spine surgery.

LEVEL OF EVIDENCE

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

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.

Adverse Events Following Cervical Disc Arthroplasty: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

Cervical arthroplasty is an increasingly popular treatment of cervical radiculopathy and myelopathy. An understanding of the potential adverse events (AEs) is important to help both clinicians and patients. We sought to provide a comprehensive systematic review of the AEs reported in all randomized controlled trials (RCTs) of cervical disc arthroplasty in an attempt to characterize the quality of reporting.

METHODS

We conducted a systematic review of MEDLINE and Web of Science for RCTs of cervical disc arthroplasty reporting AEs. We reported the most frequently mentioned AEs, including dysphagia/dysphonia, vascular compromise, dural injury, and infections. We recorded the presence of industry funding and scored the quality of collection methods and reporting of AEs.

RESULTS

Of the 3734 identified articles, 29 articles met full inclusion criteria. The quality of AE reporting varied significantly between studies, and a combined meta-analysis was not feasible. The 29 articles covered separate 19 RCTs. Eight studies were US Food and Drug Administration (FDA) investigational device exemption (IDE) trials. Rates were recorded for the following AEs: dysphagia/dysphonia (range = 1.3% to 27.2%), vascular compromise (range = 1.1% to 2.4%), cervical wound infection (range = 1.2% to 22.5%), and cerebrospinal fluid leak (range = 0.8% to 7.1%).

CONCLUSIONS

There is a lack of consistency in reporting of AEs among RCTs of cervical arthroplasty. FDA IDE trials scored better in AE event reporting compared to other studies. Standardized definitions for AEs and standardized data collection methodology are needed to improve future studies.

Clinical experience and two-year follow-up with a one-piece viscoelastic cervical total disc replacement

BACKGROUND

The purpose of this study is to present clinical outcome data from a 2-year post-market study of a viscoelastic one-piece cervical total disc replacement (TDR) in Europe.

METHODS

Thirty-nine patients were implanted at five surgical sites in an European post-market clinical study. Clinical outcomes included improvement of neck disability index (NDI) and visual analog scale scores for neck and arm pain from baseline to 2-year follow-up, neurological examinations, patients view on the success of surgery, complications, and subsequent surgical interventions.

RESULTS

Thirty patients had the Freedom^® Cervical Disc (FCD) implanted at a single level, and nine patients were implanted at two adjacent levels. The population had a similar distribution of male [20] and female [19] subjects, with a mean age of 45 years. All self-administered outcome measures showed significant clinically important improvements from baseline to the 2-year follow-up. Mean preoperative NDI score improved from 48% to 20%, 13%, 8%, 6% and 4% at 6 weeks, 3, 6, 12, and 24 months, respectively. Average preoperative visual analog scale (VAS) scores of the neck, right and left arm pain intensity and frequency showed significant improvement. All neurological outcome measurements showed immediate improvement from preoperative values and continued improvement throughout 2 years follow-up. From pre-op to 24 months, neurological deficits declined in the population from 21% to 6% for reflex function, 62% to 17% for sensory function, and 38% to 3% for motor function. No patients experienced a deterioration in any measured outcomes compared with the preoperative situation. Patient satisfaction increased over 2 years post-op, with 83% of patients responding that they would "definitely" choose to have the same treatment for their neck/arm condition and another 11% responding that they would "probably" choose to have the same treatment.

CONCLUSIONS

The FCD performs as expected in patients with single-level and two-level degenerative disc disease.

Cervical Total Disc Replacement and Anterior Cervical Discectomy and Fusion: Reoperation Rates, Complications, and Hospital Resource Utilization in 72 688 Patients in the United States

BACKGROUND

Healthcare readmissions are important causes of increased cost and have profound clinical impact. Thirty-day readmissions in spine surgery have been well documented. However, rates, causes, and outcomes are not well understood outside 30 d.

OBJECTIVE

To analyze 30- and 90-d readmissions for a retrospective cohort of anterior cervical discectomy and fusions (ACDF) and total disc replacement (TDR) for degenerative cervical conditions.

METHODS

The Nationwide Readmissions Database approximates 50% of all US hospitalizations with patient identifiers to track patients longitudinally. Patients greater than 18 yr old were identified. Rates of readmission for 30 and 90 d were calculated. Predictor variables, complications, outcomes, and costs were analyzed via univariate and multivariable analyses.

RESULTS

Between January and September 2013, 72 688 patients were identified. The 30- and 90-d readmission rates were 2.67% and 5.97%, respectively. The most prevalent reason for 30-d readmission was complication of medical/surgical care (20.3%), whereas for 90-d readmission it was degenerative spine etiology (19.2%). Common risk factors for 30- and 90-d readmission included older age, male gender, Medicare/Medicaid, prolonged initial length of stay, and various comorbidities. Unique risk factors for 30- and 90-d readmissions included adverse discharge disposition and mechanical implant-related complications, respectively. When comparing ACDF and TDR, ACDFs were associated with increased 90-d readmissions (6.0% vs 4.3%). The TDR cohort had a shorter length of stay, lower complication rate, and fewer adverse discharge dispositions.

CONCLUSION

Identification of readmission causes and predictors is important to potentially allow for changes in periperative management. Decreasing readmissions would improve patient outcomes and reduce healthcare costs.

Clinical and radiological outcome at 10 years of follow-up after total cervical disc replacement

PURPOSE

Previous studies have demonstrated that total cervical disc replacement (cTDR) represents a viable treatment alternative to the 'gold standard' anterior cervical discectomy and fusion for the treatment of well-defined cervical pathologies at short- and mid-term follow-up (FU). However, the implementation and acceptance of a non-fusion philosophy is closely associated with its avoidance of adjacent segment degeneration. Proof of the functional sustainability and clinical improvement of symptoms at long-term FU is still pending. The aim of this ongoing prospective study was to investigate the clinical and radiological results of cTDR at long-term FU.

METHODS

50 patients were treated surgically within a non-randomised prospective study framework with cTDR (ProDisc C™, Synthes, Paoli, PA, USA). Patients were examined preoperatively followed by routine clinical and radiological examinations at 1, 5 and 10 years after surgery, respectively. In addition to the clinical scores, conventional X-ray images of the cervical spine were taken in anteroposterior and lateral view as well as flexion/extension images. Clinical outcome scores included parameters such as the Neck Disability Index (NDI), Visual Analogue Scale (VAS), arm and neck pain self-assessment questionnaires as well as subjective patient satisfaction rates. The radiological outcome variables included the range of motion (ROM) of the implanted prosthesis between maximum flexion and extension images, the occurrence of heterotopic ossifications and radiographic signs of adjacent segment degenerative changes. The reoperation rate following cTDR was recorded as a secondary outcome variable.

RESULTS

A significant and maintained clinical improvement of all clinical outcome scores was observed after a mean FU of 10.2 years (VASarm 6.3-2.1; VASneck 6.4-1.9; NDI 21-6; p < 0.05). An increase in the incidence and the extent of heterotopic ossifications was noted during the post-operative course with a significant influence on the function of the prosthesis, which, however, did not reveal any detrimental effect on the patients' clinical symptomatology. Prosthesis mobility declined from 9.0° preoperatively and 9.1° at 1 year FU to 7.7° and 7.6° at the five- and ten-year FU examinations, respectively. Radiological signs of adjacent segment degeneration were detected in 13/38 (35.7%), however, in only 3/38 (7.9%) patients this radiological changes were associated with clinical symptoms requiring conservative treatment. Intraoperative technical failure in two cases required interbody fusion with a cage (2/50). One patient (1/48, 2.1%) treated this motion device had revision surgery at the index level.

CONCLUSION

Cervical total disc replacement with ProDisc C demonstrated a significant and maintained improvement of all clinical outcome parameters at a follow-up of ≥10 years. The present long-term data reveal that with an exceptionally low implant-related reoperation rate and low symptomatic adjacent segment degeneration rate, cTDR may be regarded as a safe and viable treatment option.

Artificial Cervical Disk Replacement for the Treatment of Adjacent Segment Disease After Anterior Cervical Decompression and Fusion

STUDY DESIGN

Retrospective study.

OBJECTIVE

To evaluate the outcome of artificial cervical disk replacement (ACDR) for the treatment of adjacent segment disease (ASD) after anterior cervical decompression and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

ACDF is the useful procedure for degenerative cervical diseases. However, studies have reported accelerated degeneration of functional spinal units adjacent to the fusion site after ACDF.

MATERIALS AND METHODS

Between January 2004 and January 2011, 32 inpatients (18 male, 14 female; age, 38-61 y; mean, 48 y) underwent ACDR for the treatment of ASD after previous ACDF (single-level: n=12; 2-level: n=15; 3-level: n=5). In 22 patients, ASD occurred above the fusion site, and in 10 it occurred below the site. After ACDR, the patients were followed up for 30-62 months (mean, 49 mo). Before and after ACDR, patients were evaluated using the pain visual analog scale (VAS), the Japanese Orthopedic Association (JOA) score, and neck disability index (NDI). In addition, the range of motion (ROM) of the replaced and adjacent unfused segments was measured by flexion/extension lateral radiography. Periprosthetic heterotopic ossification was detected using McAfee's classification. Degeneration of the adjacent unfused segment was evaluated using Goffin scale.

RESULTS

All patients had successful surgery. Before ACDR, neck VAS, upper-limb VAS, JOA score, and NDI were 7.2±1.8, 6.9±1.1, 9.8±2.5, and 40.5±4.8, respectively. At the last follow-up, they were 1.2±0.3, 0.9±0.3, 14.5±1.1, and 9.0±2.5, respectively. Compared with presurgery, the improvements in VAS, JOA score, and NDI at the final follow-up were statistically significant (all P<0.05). During follow-up, prosthesis positioning was satisfactory without migration or downward movement. Preoperatively, the ROMs of the replaced and adjacent segments were 8.7±2.6 and 7.6±3.0, respectively. At the last follow-up, they were 8.5±2.2 and 7.2±2.6, respectively (both P>0.05). At the last follow-up, 2 patients had grade II heterotopic ossification; 3 patients had aggravated degeneration (vs. preoperative status) of the adjacent unfused segment. However, the reduction in Goffin grade was not statistically significant.

CONCLUSIONS

Our follow-up shows that ACDR is an effective treatment for post-ACDF ASD. It can maintain the ROMs of the replaced segment as well as the adjacent unfused segment.