Historical review of cervical arthroplasty

A Review of Finite Element Modeling for Anterior Cervical Discectomy and Fusion

The cervical spine poses many complex challenges that require complex solutions. Anterior cervical discectomy and fusion (ACDF) has been one such technique often employed to address such issues. In order to address the problems with ACDF and assess the modifications that have been made to the technique over time, finite element analyses (FEA) have proven to be an effective tool. The variations of cervical spine FEA models that have been produced over the past couple of decades, particularly more recent representations of more complex geometries, have not yet been identified and characterized in any literature. Our objective was to present material property models and cervical spine models for various simulation purposes. The outlining and refinement of the FEA process will yield more reliable outcomes and provide a stable basis for the modeling protocols of the cervical spine.

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.

Safety and Validity of Anterior Cervical Disc Replacement for Single-level Cervical Disc Disease: Initial Two-year Follow-up of the Prospective Observational Post-marketing Surveillance Study for Japanese Patients

Anterior cervical disc replacement (ACDR) using cervical artificial disc (CAD) has the advantage of maintaining the range of motion (ROM) at the surgical level, subsequently reducing the postoperative risk of adjacent disc disease. Following the approval for the clinical use in Japan, a post-marketing surveillance (PMS) study was conducted for two different types of CAD, namely, Mobi-C (metal-on-plastic design) and Prestige LP (metal-on-metal design). The objective of this prospective observational multicenter study was to analyze the first 2-year surgical results of the PMS study of 1-level ACDR in Japan. A total of 54 patients were registered (Mobi-C, n = 24, MC group; Prestige LP, n = 30, PLP group). Preoperative neurological assessment revealed radiculopathy in 31 patients (57.4%) and myelopathy in 15 patients (27.8%). Preoperative radiological assessment classified the disease category as disc herniation in 15 patients (27.8%), osteophyte in 6 patients (11.1%), and both in 33 patients (61.1%). The postoperative follow-up rates at 6 weeks, 6 months, 1 year, and 2 years after ACDR were 92.6%, 87.0%, 83.3%, and 79.6%, respectively. In both groups, patients' neurological condition improved significantly after surgery. Radiographic assessment revealed loss of mobility at the surgical level in 9.5% of patients in the MC group and in 9.1% of patients in the PLP group. No secondary surgeries at the initial surgical level and no serious adverse events were observed in either group. The present results suggest that 1-level ACDR is safe, although medium- to long-term follow-up is mandatory to further verify the validity of ACDR for Japanese patients.

Cervical and Lumbar Disc Arthroplasty: A Review of Current Implant Design and Outcomes

While spinal disc pathology has traditionally been treated using fusion-based procedures, recent interest in motion-preserving disc arthroplasties has grown. Traditional spinal fusion is associated with loss of motion, alteration of native spine kinematics, and increased risks of adjacent segment disease. The motion conferred by disc arthroplasty is believed to combat these complications. While the first implant designs resulted in poor patient outcomes, recent advances in implant design and technology have shown promising radiographic and clinical outcomes when compared with traditional fusion. These results have led to a rapid increase in the utilization of disc arthroplasty, with rates of cervical arthroplasty nearly tripling over the course of 7 years. The purpose of this review was to discuss the evolution of implant design, the current implant designs utilized, and their associated outcomes. Although disc arthroplasty shows significant promise in addressing some of the drawbacks associated with fusion, it is not without its own risks. Osteolysis, implant migration, and the development of heterotopic ossification have all been associated with disc arthroplasty. As interest in these procedures grows, so does the interest in developing improved implant designs aimed at decreasing these adverse outcomes. Though they are still relatively new, cervical and lumbar disc arthroplasty are likely to become foundational methodologies for the treatment of disc pathology.

Anterior Cervical Discectomy and Fusion Using Zero-P System for Treatment of Cervical Spondylosis: A Meta-Analysis

Objective

The current study aimed to explore the efficacy of Zero profile intervertebral fusion system (Zero-P) and traditional anterior plate cage system (PC) in the treatment of cervical spondylotic myelopathy (CSM). Further, the present study evaluated effects of the treatments on medical security, height of intervertebral disc, adjacent-level ossification development (ALOD), and adjacent segmentation disease (ASD) through a systematic retrospective analysis.

Methods

Studies on Zero-P system and traditional anterior plate cage system for ACDF in the treatment of CSM were searched in PubMed, Web of Science, Ovid, Embase, and Cochrane Library databases. Two independent researchers screened articles, extracted data, and evaluated the quality of the articles based on the inclusion and exclusion criteria of the current study. RevMan5.3 software was used for meta-analysis following the guidelines of Cochrane collaboration network. Cervical curvature, interbody fusion rate, preoperative and postoperative disc height index (DHI), fusion cage sinking rate, postoperative dysphagia, ASD, ALOD, and loosening of screw were compared between the two groups.

Results

A total of 17 literatures were included in the present study, including 6 randomized controlled trials and 11 observational studies. The studies comprised a total of 1204 patients with CSM, including 605 patients in the Zero-P system group (Zero-P group) and 599 patients in the traditional animal plate cage group (PC group). Results of this meta-analysis showed that postoperative dysphagia [OR = 0.40, CI (0.28, 95% 0.58), P < 0.00001], ALOD [OR = 0.09, CI (0.02, 95% 0.39), P = 0.001], ASD [OR = 0.42, CI (0.20, 95% 0.86), P = 0.02], and screw loosening [OR = 0.20, CI (0.08, 95% 0.52), P = 0.0009] of the Zero-P group were significantly lower compared with the PC group. On the other hand, preoperative cervical curvature [WMD = −0.23, CI (−1.38, 95% 0.92), P = 0.69], postoperative cervical curvature [WMD = −0.38, CI (−1.77, 95% 1.01), P = 0.59], cage sinking rate [OR = 1.41, CI [0.52, 95% 3.82], P = 0.50], intervertebral fusion rate [OR = 0.76, CI (0.27, 95% 2.48), P = 0.38], preoperative DHI [WMD = −0.04, CI (−0.14, 95% 0.22), P = 0.65], and postoperative DHI [WMD = 0.06, CI (−0.22, 95% 0.34), P = 0.675] were not significantly different between the two groups.

Conclusion

It was evident that the Zero-P system used in ACDF is superior compared with the traditional anterior plate cage system in postoperative dysphagia, avoiding ALOD, ASD, and screw loosening.

Biomechanics of Cervical Disc Arthroplasty Devices

Prosthesis design has an influence on the quantity and quality of postoperative motion after cervical disc arthroplasty. Prostheses with built-in resistance to angular and translational motion may have an advantage in restoring physiologic motion. The ability of a prosthesis to work with remaining bony and soft tissues to restore motion and load-sharing is a function of the kinematic degrees of freedom DOF, axis of rotation for a given motion, and device stiffness. How these characteristics allow the prosthesis to work with the patient's anatomy will determine whether the prosthesis is successful at restoring motion and mitigating adjacent-level stresses.

Biomechanics of Cervical Disc Arthroplasty-A Review of Concepts and Current Technology

Activities of daily living require the subaxial cervical spine (C2-C7) to have substantial mobility. Cervical degenerative changes can cause abnormal motions and altered load distribution, leading to pain and limiting the ability of individuals to perform activities of daily living. Anterior cervical discectomy and fusion (ACDF) has been widely used to treat symptomatic cervical spondylosis. Clinical studies have shown cervical disc arthroplasty (CDA) to be a viable alternative to ACDF for the treatment of radiculopathy and myelopathy. The benefits of CDA are based on the premise that preservation of physiologic motions and load-sharing at the treated level would lead to longevity of the index-level facet joints and mitigate the risk of adjacent segment degeneration.This review article classifies cervical disc prostheses according to their kinematic degrees of freedom and device constraints. Discussion on how these design features may affect cervical motion after implantation will provide the reader with valuable information on how disc prostheses may function clinically.The ability of a disc prosthesis to work in concert with remaining bony and soft tissue structures to restore physiologic motion and load-sharing is a function of the following design features and surgical factors: Kinematic degrees of freedom-Prostheses that allow translation independent of rotation allow, in theory, the spinal anatomy to dictate segmental motion after CDA potentially restoring physiologic motion and load-sharing. A 6-degrees-of-freedom disc prosthesis may be best equipped to achieve the intended function of CDA.Built-in stiffness-A disc prosthesis with built-in resistance to angular and translational motion may have an advantage in restoring stability to a hypermobile segment without eliminating motion.Surgical factors related to prosthesis implantation may influence cervical segments after CDA. These factors include the amount of disc space distraction caused by the prosthesis, prosthesis placement in the sagittal and coronal planes, and integrity of the soft tissue envelope.

Zero-profile versus cage-plate interbody fusion system in anterior cervical discectomy and fusion for the treatment of multilevel cervical spondylosis: A protocol of systematic review and meta-analysis

BACKGROUND

The objective of this meta-analysis was to summarize and identify the available evidence from these studies to estimate which device was better for multilevel cervical spondylotic myelopathy (MCSM). And provides clinicians with evidence on which to base their clinical decision making.

METHODS

This review will include all studies comparing the new Zero-profile versus cage-plate interbody fusion system in anterior cervical discectomy and fusion (ACDF) for the treatment of MCSM. The search strategy will be performed in 9 databases. We will not establish any limitations to language and publication status, published from inception to the July, 2020. Two reviewers will screen, select studies, extract data, and assess quality independently. Outcome is operative time, blood loss, clinical function outcome, radiologic outcomes, and complications. The methodological quality including the risk of bias of the included studies will be evaluated. We will carry out statistical analysis using RevMan 5.3 software.

RESULTS

This study will summarize current evidence to assess the efficacy and safety of Zero-profile versus cage-plate interbody fusion system in ACDF for the treatment of MCSM.

CONCLUSION

The findings of this study will provide helpful evidence for the clinician, and will promote further studies, as well as comparing the 2 devices in ACDF for MCSM REGISTRATION NUMBER:: INPLASY202070095 (DOI number: 10.37766/inplasy2020.7.0095).

Incidence of Subsidence of Seven Intervertebral Devices in Anterior Cervical Discectomy and Fusion: A Network Meta-Analysis

BACKGROUND

Subsidence is an incapacitating complication in anterior cervical discectomy and fusion (ACDF). However, the debate over which of the intervertebral devices is associated with lower incidence of subsidence remains to be settled.

METHODS

Seven dominant techniques comprising cage with plate (CP), iliac bone graft with plate (IP), Zero-profile cage with screws (Zero-P), ROI-C cages with clips (ROI-C), polyether ether ketone cage alone (PCA), iliac crest autogenous graft (ICAG), and titanium cage alone (TCA) were examined. The incidences of subsidence in the different groups were calculated and compared.

RESULTS

A total of 30 studies with 2264 patients were identified. Overall, the CP group presented the lowest incidence of subsidence, and its incidence was significantly lower than that in the Zero-P group, the PCA group, the ICAG group, and the TCA group (P < 0.05). The incidence of subsidence in the IP group was significantly lower than that in the PCA group, the ICAG group, and the TCA group (P < 0.05). In single-level ACDF, the CP group presented the lowest incidence of subsidence, and its incidence was significantly lower than that in the PCA group and the TCA group (P < 0.05). No difference was found between single-level and multilevel ACDF and the incidence of subsidence was higher in those undergoing single-level ACDF.

CONCLUSIONS

CP and IP resulted in a lower rate of subsidence than cage alone or ICAG. Zero-P and ROI-C cages led to similar subsidence rates with plate. All types of intervertebral device can be applied to both single-level and multilevel ACDF with comparable subsidence rate.

Cervical disc arthroplasty: 10-year outcomes of the Prestige LP cervical disc at a single level

OBJECTIVE

Food and Drug Administration-approved investigational device exemption (IDE) studies have provided level I evidence supporting cervical disc arthroplasty (CDA) as a safe and effective alternative to anterior cervical discectomy and fusion (ACDF). Long-term CDA outcomes continue to be evaluated. Here, the authors present outcomes at 10 years postoperatively for the single-level CDA arm of an IDE study (postapproval study).

METHODS

The primary endpoint was overall success, a composite variable composed of five criteria: 1) Neck Disability Index score improvement ≥ 15 points; 2) maintenance or improvement in neurological status; 3) no decline in anterior or posterior functional spinal unit (FSU) height of more than 2 mm compared to 6 weeks postoperatively; 4) no serious adverse event (AE) caused by the implant or the implant and the surgical procedure; and 5) no additional surgery classified as a failure. Additional safety and effectiveness measures included numeric rating scales for neck pain and arm pain, SF-36 quality-of-life physical and mental components, patient satisfaction, range of motion, and AEs.

RESULTS

From the reported assessments at 7 years postoperatively to the 10-year postoperative follow-up, the scores for all patient-reported outcomes, rate of overall success (without FSU), and proportion of patients at least maintaining their neurological function remained stable for the CDA group. Nine patients had secondary surgery at the index level, increasing the secondary surgery cumulative rate from 6.6% to 10.3%. In that same time frame, four patients experienced a serious implant or implant/surgical procedure-related AE, for a 10-year cumulative rate of 7.8%. Seven patients had any second surgery at adjacent levels, for a 10-year cumulative rate of 13.8%. Average angular motion at both the index and adjacent levels was well maintained without creating hypermobility. Class IV heterotopic ossification increased from 1.2% at 2 years to 4.6% at 7 years and 9.0% at 10 years. Patient satisfaction was > 90% at 10 years.

CONCLUSIONS

CDA remained safe and effective out to 10 years postoperatively, with results comparable to 7-year outcomes and with high patient satisfaction.Clinical trial registration no.: NCT00667459 (clinicaltrials.gov).

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

Objectives

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

Methods

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

Results

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

Conclusion

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

Cervical Total Disk Arthroplasty

In the United States, cervical total disk arthroplasty (TDA) is US Federal Drug Administration (FDA) approved for use in both 1 and 2-level constructions for cervical disk disease resulting in myelopathy and/or radiculopathy. TDA designs vary in form, function, material composition, and even performance in?vivo. However, the therapeutic goals are the same: to remove the painful degenerative/damaged elements of the intervertebral discoligamenous joint complex, to preserve or restore the natural range of spinal motion, and to mitigate stresses on adjacent spinal segments, thereby theoretically limiting adjacent segment disease (ASDis). Cervical vertebrae exhibit complex, coupled motions that can be difficult to artificially replicate. Commonly available TDA designs include ball-and-socket rotation-only prostheses, ball-and-trough rotation and anterior-posterior translational prostheses, as well as unconstrained elastomeric disks that can rotate and translate freely in all directions. Each design has its respective advantages and disadvantages. At this time, available clinical evidence does not favor 1 design philosophy over another. The superiority of cervical TDA over the gold-standard anterior cervical discectomy and fusion is a subject of great controversy. Although most studies agree that cervical TDA is at least as effective as anterior cervical discectomy and fusion at reducing or eliminating preoperative pain and neurological symptoms, the clinical benefits of motion preservation- that is, reduced incidence of ASDis-are far less clear. Several short-to-mid-term studies suggest that disk arthroplasty reduces the radiographic incidence of adjacent segment degeneration; however, the degree to which this is clinically significant is disputed. At this time, TDA has not been clearly demonstrated to reduce symptomatic?ASDis.

Current practice of cervical disc arthroplasty: a survey among 383 AOSpine International members

OBJECTIVE

The use of cervical disc arthroplasty (CDA) in spinal practice is controversial. This may be explained by the lack of studies with a large sample size and long-term outcomes. With this survey the authors aimed to evaluate the opinions of spine surgeons on the use of CDA in the current treatment of cervical disc herniation (CDH).

METHODS

A web-based survey was sent to all members of AOSpine International by email using SurveyMonkey on July 18, 2016. A single reminder was sent on August 18, 2016. Questions included geographic location; specialty; associated practice model; number of discectomies performed annually; the use of CDA, anterior cervical discectomy (ACD), and anterior cervical discectomy and fusion (ACDF); and the expectations for clinical outcomes of these procedures.

RESULTS

A total of 383 questionnaires were analyzed. Almost all practitioners (97.9%) were male, with a mean of 15.0 ± 9.7 years of clinical experience. The majority of responders were orthopedic surgeons (54.6%). 84.3% performed ACDF as the standard technique for CDH. 47.8% of the surgeons occasionally used CDA, whereas 7.3% used CDA as standard approach for CDH. The most common arthroplasty device used was the ProDisc-C. Low evidence for benefits and higher costs were the most important reasons for not offering CDA. The risk of adjacent-level disease was considered smaller for CDA as compared with ACDF. However, ACDF was expected to have the highest effectiveness on arm pain (87.5%), followed by CDA (77.9%), while ACD had the least (12.6%).

CONCLUSIONS

In this survey, CDA was not considered to be the routine procedure to treat CDH. Reported benefits included the reduced risk of adjacent-level disease and preservation of motion of the neck. Lack of enough evidence on its effectiveness as well as higher costs were considered to be disadvantages of CDA. More research should be conducted on the implementation impact of CDA and the cost-effectiveness from society's perspective.

The new Zero-P implant can effectively reduce the risk of postoperative dysphagia and complications compared with the traditional anterior cage and plate: a systematic review and meta-analysis

Background

The low-profile angle-stable spacer Zero-P is a new kind of cervical fusion system that is claimed to limit the potential drawbacks and complications. The purpose of this meta-analysis was to compare the clinical and radiological results of the new Zero-P implant with those of the traditional anterior cage and plate in the treatment of symptomatic cervical spondylosis, and provides clinicians with evidence on which to base their clinical decision making.

Methods

The following electronic databases were searched: PMedline, PubMed, EMBASE, the Cochrane Central Register of Controlled Trials, Evidence Based Medicine Reviews, VIP, and CNKI. Conference posters and abstracts were also electronically searched. The efficacy was evaluated in intraoperative time, intraoperative blood loss, fusion rate and dysphagia.

Results

For intraoperative time and intraoperative blood loss, the meta-analysis revealed that the Zero-P surgical technique is not superior to the cage and plate technique . For fusion rate, the two techniques both had good bone fusion, however, this difference is not statistically significant. For decrease of JOA and dysphagia, the pooled data showed that the Zero-P surgical technique is superior to the cage and plate technique.

Conclusions

Zero-P interbody fusion can attain good clinical efficacy and a satisfactory fusion rate in the treatment of symptomatic cervical spondylosis. It also can effectively reduce the risk of postoperative dysphagia and its complications. However, owing to the lack of long-term follow-up, its long-term efficacy remains unknown.

Clinical and radiologic comparison of dynamic cervical implant arthroplasty and cervical total disc replacement for single-level cervical degenerative disc disease

Anterior cervical discectomy and fusion, to date the most successful spine procedure for the surgical treatment of cervical radiculopathy, has limitations that have led to the development of non-fusion cervical procedures, such as cervical total disc replacement (TDR) and dynamic cervical implant (DCI) arthroplasty. We compared the clinical and radiological results of DCI and cervical TDR for the treatment of single-level cervical degenerative disc disease in Chinese patients. A retrospective review of 179 patients with cervical spondylotic myelopathy who underwent DCI or TDR between April 2010 and October 2012 was conducted, and 152 consecutive patients (67 patients single-level DCI and 85 single-level TDR) who completed at least 2years of follow-up were included. Clinical and radiological assessments were performed preoperatively and at 1week and 3, 6, 12, and 24months postoperatively. The most common operative level was C5/C6 (49.3%). The differences in blood loss, duration of surgery, and duration of hospitalization were not statistically significant. The Japanese Orthopaedic Association scale, Visual Analog Scale, Neck Disability Index, and Short Form-36 scores improved significantly after surgery in both the DCI and TDR groups (P<0.05), but the differences were not statistically significant at the final follow-up. The rate of occurrence of heterotopic ossification was 22.4% and 28.2% in the DCI and TDR groups, respectively. As an effective non-fusion technique, DCI is a more economical procedure. Further prospective, randomized studies with long-term follow-up periods are needed to determine the long-term effects.

Wear assessments of a new cervical spinal disk prosthesis: Influence of loading and kinematic patterns during in vitro wear simulation

Surgical treatment is one of the effective methods of treatment in cervical spondylosis. The traditional method of operation is decompression fusion; however, this surgery results in restricted movement of cervical vertebra and adjacent segment degeneration. Due to the deficiency of traditional surgery, scholars have widely carried out artificial cervical disk replacement surgery and have achieved good clinical effects. Comparing to the characteristics of the common artificial cervical disk which is used frequently, we developed a new artificial cervical intervertebral disk prosthesis. The purpose of this study was to determine the wear behavior in a cervical total disk replacement system. The total disk replacement system tested consists of a ultra-high-molecular-weight polyethylene inlay articulating between a Ti6Al4V alloy superior plate and an inferior plate, using a spine wear simulator, per the ISO 18192-1:2011 standard test methods. Three rotations and axial force were applied on each station. The specimens were removed at 5 × 10(5) and 10(6) cycles and at intervals of 10(6) cycles thereafter to determine the actual mass loss. The serum was replaced every 5 × 10(5) cycles. The specimens were changed periodically among the different stations. A mean ultrahigh molecular weight polyethylene inlay wear rate of 0.53 mg per million cycles (standard = 0.13 mg per 10(6) cycles) was found after 10(7) cycles. All inferior plates showed slight scratching after 10(7) cycles. The impingement wear simulation introduced here proved to be suitable to predict in vivo impingement behavior in regard to the contact pattern seen on retrieved devices of the Pretic-I disk arthroplasty design in a preclinical test.

Long term preservation of motion with artificial cervical disc implants: A comparison between cervical disc replacement and rigid fusion with cage

Background:

With the advancement of technologies there is more interest in the maintenance of the spine's biomechanical properties focusing on the preservation of the functional motion segment. In present article we describe our experience with 25 cases managed with artificial cervical discs with 28 Solis cage following cervical discectomy with a mean follow-up period of 7.5 year.

Materials and Methods:

All surgeries were performed by single surgeon from March 2004 to June 2005 with a follow-up till date. Patients with symptomatic single or multiple level diseases that had no prior cervical surgery were candidates for the study. Cohort demographics were comparable. Standardized clinical outcome measures and radiographic examinations were used at prescribed post-operative intervals to compare the treatment groups. Relief in radicular pain, cervical spine motion, and degenerative changes at follow-up were noted.

Results:

In a total 53 cases, the mean age in prosthesis group was 47 years (age range: 30-63 years) and mean age in cage group was 44 years (32-62 years). Mean hospital stay was 2.7 days in both the groups. At 4 weeks complete cervical movements could be achieved in 19 cases in artificial disc group. Maintenance of movement after 7.5 years was in 76% of these patients. Lordosis was maintained in all cases till date. There was no mortality or wound infection in our series.

Conclusions:

We conclude that artificial cervical disc could be an alternative to fixed spinal fusion as it represents the most physiological substitute of disc. However, there is need for further studies to support the use of artificial cervical disc prosthesis.

Utilization trends of cervical artificial disc replacement after FDA approval compared with anterior cervical fusion: adoption of new technology

STUDY DESIGN

Epidemiologic study.

OBJECTIVE

To compare the utilization of anterior cervical discectomy and fusion (ACDF) versus cervical disc arthroplasty (CDA) in terms of patient and hospital characteristics during the 3 years after Food and Drug Administration (FDA) approval of CDA devices in 2007.

SUMMARY OF BACKGROUND DATA

There was a surge in CDA adoption in the 3 years prior to FDA approval of CDA devices in 2007. However, utilization trends of CDA versus ACDF since the FDA approval are unknown.

METHODS

The Nationwide Inpatient Sample database was used to identify CDA and ACDF procedures performed in the United States in the 3 years after FDA approval of CDA devices (2008-2010). The frequencies of CDA and ACDF were estimated, stratified by patient and hospital characteristics. Average length of hospital stay and total charges and costs were estimated. Multivariable analysis was performed to identify patient and hospital characteristics associated with CDA utilization.

RESULTS

In the 3 years after FDA approval of cervical disc devices, population-adjusted growth rates for CDA and ACDF were 4.9% and 11.8%, respectively (P = 0.6977). Female, African American and Medicaid patients were less likely to receive CDA. CDA was less likely to be performed in patients with cervical spondylotic changes and more likely to be performed in younger and healthier patients. CDA was less likely to be performed in the Midwestern United States or in public hospitals.

CONCLUSION

The prevalence of CDA increased in the 3 years after FDA approval with a growth rate that is approximately twice than that for ACDF. Although there seems to be CDA adoption, CDA growth seemed to have reached a plateau and ACDF still remained the dominant surgical strategy for cervical disc disease. Possible regional, racial, and sex disparities in CDA utilization and a more strict approach in the selection of CDA over traditional ACDF may have impeded rapid adoption of CDA.

LEVEL OF EVIDENCE

3.

History of cervical spine surgery: from nihilism to advanced reconstructive surgery

STUDY DESIGN

Review of literature.

OBJECTIVES

To review and analyze the evolution of cervical spine surgery from ancient times to current practice. The aim is to present an accessible overview, primarily intended for a broad readership.

METHODS

Descriptive literature review and analysis of the development of cervical spine surgery from the prehistoric era until today.

RESULTS

The first evidence for surgical treatment of spinal disorders dates back to approximately 1500 BC. Conservative approaches to treatment have been the hallmark for thousands of years, but over the past 50 years progress has been rapid. We illustrate how nations have added elements to this complex subject and how knowledge has surpassed borders and language barriers. Transferral of knowledge occurred from Babylon (Bagdad) to Old Egypt, to the Greek and Roman empires and finally via the Middle East (Bagdad and Damascus) back to Europe. Recent advances in the field of anesthesia, imaging and spinal instrumentation have changed long-standing nihilism in the treatment of cervical spine pathologies to the current practice of advanced reconstructive surgery of the cervical spine. A critical approach to the evaluation of benefits and complications of these advanced surgical techniques for treatment of cervical spine disorders is required.

CONCLUSION

Advances in surgery now permit full mechanical reconstruction of the cervical spine. However, despite substantial experimental progress, spinal cord repair and restoration of lost functions remain a challenge. Modern surgeons are still looking for the best way to manage spine disorders.

Utilization trends of cervical artificial disc replacement during the FDA investigational device exemption clinical trials compared to anterior cervical fusion

While anterior cervical discectomy and fusion (ACDF) is the gold standard surgical treatment for cervical disc disease, concerns regarding adjacent segment degeneration lead to the development of cervical disc arthroplasty (CDA). This study compares the utilization trends of CDA versus ACDF during the period of the Food and Drug Administration Investigational Device Exemption clinical trials from 2004 to 2007. The Healthcare Cost and Utilization Project Nationwide Inpatient Sample database was used to identify CDA and ACDF procedures performed in the USA between 2004 and 2007. The prevalence of CDA and ACDF procedures was estimated and stratified by age, sex, diagnosis, census region, payor class, and hospital characteristics. The average length of hospital stay, total charges, and costs were also estimated. The number of CDA surgeries significantly increased annually from 2004 to 2007 and mostly took place at urban non-teaching hospitals. There were no regional differences between CDA and ACDF utilization. There was no difference between sex or admission type between CDA and ACDF patients. ACDF patients were older and had more diabetes, hypertension, and chronic obstructive pulmonary disease. CDA patients were more likely to be discharged home and had shorter hospital stays but had a higher rate of deep venous thrombosis than ACDF patients. Significantly more CDA patients had private insurance while more ACDF patients had Medicare. The average cost was higher for ACDF than CDA. While ACDF dominated surgical intervention for cervical disc disease during the trial period, CDA utilization increased at a significantly greater rate suggesting rapid early adoption.

A case of cervical metastases in a patient with preexisting cervical disc replacement and fusion after 2-year symptom-free interval: when do we need interdisciplinary diagnostics?

Recurrent cervical symptoms frequently occur after cervical disc replacement and fusion. To date, no algorithm for the diagnostic assessment of these symptoms has been established. We present a case report and review of the literature to illustrate the need for interdisciplinary diagnostics in recurrent cervicobrachialgia without pathological cervical imaging. The hospital chart, medical history, physical examination, and imaging of a single patient were reviewed. A 53-year-old man with preexisting cervical disc replacement and fusion presented with a new episode of cervicobrachialgia after a 2-year symptom-free interval. Cervical magnetic resonance imaging (MRI) showed no pathological findings. Six months later the patient reported increasing symptoms including numbness and weakness of the right arm. Repeated cervical MRI and thoracic computed tomography revealed cervical metastases with intraspinal tumor growth and an underlying extensive small cell bronchial carcinoma. In recurrent cervicobrachialgia, without pathological cervical imaging, interdisciplinary diagnostics are needed. Basic diagnostic tests may assist to exclude severe non-vertebrogenic pathologies.

Update on the evidence for adjacent segment degeneration and disease

BACKGROUND CONTEXT

The evidence surrounding the topic of adjacent segment degeneration and disease has increased dramatically with an abundant amount of literature discussing the incidence of and techniques to avoid it. However, this evidence is often confusing to discern because of various definitions of both adjacent segment degeneration and disease.

PURPOSE

To organize and review the recent evidence for adjacent segment degeneration and disease.

RESULTS

Although multifactorial, three distinct causes of adjacent segment disease in both the lumbar and cervical spine have been discussed: the natural history of the adjacent disc; biomechanical stress on the adjacent level caused by the fusion; and disruption of the anatomy at the adjacent level with the initial surgery. The incidence of adjacent segment degeneration in the lumbar spine has been widely reported in the literature from 0% to 100%; conversely, the reported incidence in the cervical spine is less variable. Similarly, strategies at avoiding adjacent segment disease in the lumbar spine include arthroplasty, dynamic fixation, and percutaneous fixation, whereas in the cervical spine the focus has remained on arthroplasty.

CONCLUSIONS

Adjacent segment disease and degeneration remain a multifactorial problem with several techniques being developed recently to minimize them. In the future, it is likely that the popularity of these techniques will be dependent on the long-term results, which are currently unavailable.

Activ C cervical disc replacement for myelopathy

Background:

Cervical disc replacement is becoming an increasingly popular treatment option for cervical myelopathy. It retains motion at the affected segment, unlike anterior cervical discectomy and fusion. The aim of this study is to assess the outcomes of a series of patients who underwent Activ C disc replacement for cervical myelopathy.

Materials and Methods:

A series of patients at the above Trust with clinical and radiological evidence of cervical myelopathy who were suitable for cervical disc replacement from 2007 to 2009 were included. Implants were inserted by one of two consultant surgeons {IMS, MO’M}. Patients were assessed preoperatively and at six, 12 and 24 months, postoperatively, with a visual analogue score (VAS) for neck and arm pain severity and frequency, the Neck Disability Index questionnaire (NDI) and the Centre for Epidemiologic Studies Depression questionnaire (CES-D).

Results:

Ten patients underwent surgery between May 2007 and July 2009, 6 women, and 4 men. Average age was 54 years (40-64). Disc levels replaced were: four at C4-5; eight at C5-6; seven at C6-7. Three patients had one disc replaced, five patients had two discs replaced, and two patients had three discs replaced. The VAS for neck pain improved from 5.9 pre-operatively to 1.4-24 months postoperatively and the VAS arm pain improved from 5.4 to 2.6. The NDI improved from 51% preoperatively to 26.8% at 24 months postoperatively. The CES-D showed a slight increase from 19.5 preoperatively to 21.7 at 24 months, postoperatively.

Conclusion:

Cervical decompression and disc replacement improves pain and function in patients with cervical myelopathy. This benefit is maintained at 24 months post op, with no cases requiring revision.

Artificial cervical disc arthroplasty: a systematic review

STUDY DESIGN

Systematic Review.

OBJECTIVE

(1) To qualitatively analyze the literature on the efficacy and effectiveness of artificial cervical disc arthroplasty (ACDA). (2) To highlight methodological and reporting issues of randomized controlled trials (RCT) reports on effectiveness of ACDA compared to cervical fusion.

SUMMARY OF BACKGROUND DATA

ACDA is an alternate surgical procedure that may replace cervical fusion in selected patients suffering from cervical degenerative disc disease.

METHODS

We searched seven electronic databases, including MEDLINE, Cochrane Library, and EMBASE, unpublished sources, and reference lists for studies on the efficacy and effectiveness of ACDA compared to cervical fusion--the surgical standard of care for patients with cervical degenerative disc disease.

RESULTS

A total of 622 studies were retrieved, of which 18 (13 case series, four RCT reports, one nonrandomized comparative study) met the inclusion criteria for this review. The four RCTs and the nonrandomized comparative study concluded that the effectiveness of ACDA is not inferior to that of cervical fusion in the short term (up to 2-yr follow-up). The safety profile of both procedures appears similar. The case series reviewed noted improved clinical outcomes at 1 or 2 years after one or multiple-level ACDA.

CONCLUSION

ACDA is a surgical procedure that may replace cervical fusion in selected patients suffering from cervical degenerative disc disease. Within 2 years of follow-up, the effectiveness of ACDA appears similar to that of cervical fusion. Weak evidence exists that ACDA may be superior to fusion for treating neck and arm pain. Future studies should report change scores and change score variance in accordance with RCT guidelines, in order to strengthen credibility of conclusions and to facilitate meta-analyses of studies.

Cervical and lumbar spinal arthroplasty: clinical review

In contrast to cervical and lumbar fusion procedures, the principal aim of disk arthroplasty is to recapitulate the normal kinematics and biomechanics of the spinal segment affected. Following decompression of the neural elements, disk arthroplasty allows restoration of disk height and maintenance of spinal alignment. Based on clinical observations and biomechanical testing, the anticipated advantage of arthroplasty over standard arthrodesis techniques has been a proposed reduction in the development of symptomatic ALD. In this review of cervical and lumbar disk arthroplasty, we highlight the clinical results and experience with standard fusion techniques, incidence of ALD in the population of patients with surgical fusion, and indications for arthroplasty, as well as the biomechanical and clinical outcomes following arthroplasty. In addition, we introduce the devices currently available and provide a critical appraisal of the clinical evidence regarding arthroplasty procedures.

Finite element modeling of kinematic and load transmission alterations due to cervical intervertebral disc replacement

STUDY DESIGN

A parametric finite element investigation of the cervical spine.

OBJECTIVE

To determine what effect, if any, cervical disc replacement has on kinematics, facet contact parameters, and anterior column loading.

SUMMARY OF BACKGROUND DATA

Anterior cervical discectomy and fusion has been a standard treatment for certain spinal degenerative disorders, but evidence suggests that fusion contributes to adjacent-segment degeneration. Motion-sparing disc replacement implants are believed to reduce adjacent-segment degeneration by preserving kinematics at the treated level. Such implants have been shown to maintain the mobility of the intact spine, but the effects on load transfer between the anterior and posterior elements remain poorly understood.

METHODS

To investigate the effects of disc replacement on load transfer in the lower cervical spine, a finite element model was generated using cadaver-based computed tomography imagery. Mesh resolution was varied to establish model convergence, and cadaveric testing was undertaken to validate model predictions. The validated model was altered to include disc replacement prosthesis at the C4/C5 level. The effect of disc-replacement on range of motion, anteroposterior load distribution, contact forces in the facets, as well as the distribution of contact pressure on the facets were examined. Three sizes of implants were examined.

RESULTS

Model predictions indicate that the properly sized implant retains the mobility, load sharing, and contact force magnitude and distribution of the intact case. Mobility, load sharing, nuclear pressures, and contact pressures at the adjacent motion segments were not strongly affected by the presence of the properly sized implant, indicating that disc replacement may not be a significant cause of postoperative adjacent-level degeneration. Implant size affected certain mechanical parameters, such as anteroposterior load sharing, and did not affect compliance or range of motion.

CONCLUSION

The results of this work support the continued use of motion sparing implants in the lower cervical spine. Load sharing data indicate that implant size may be an important factor that merits further study; although, the deleterious effects of improper size selection may be less significant than those of fusion.

Primary and coupled motions after cervical total disc replacement using a compressible six-degree-of-freedom prosthesis

This study tested the hypotheses that (1) cervical total disc replacement with a compressible, six-degree-of-freedom prosthesis would allow restoration of physiologic range and quality of motion, and (2) the kinematic response would not be adversely affected by variability in prosthesis position in the sagittal plane. Twelve human cadaveric cervical spines were tested. Prostheses were implanted at C5-C6. Range of motion (ROM) was measured in flexion-extension, lateral bending, and axial rotation under ± 1.5 Nm moments. Motion coupling between axial rotation and lateral bending was calculated. Stiffness in the high flexibility zone was evaluated in all three testing modes, while the center of rotation (COR) was calculated using digital video fluoroscopic images in flexion-extension. Implantation in the middle position increased ROM in flexion-extension from 13.5 ± 2.3 to 15.7 ± 3.0° (p < 0.05), decreased axial rotation from 9.9 ± 1.7 to 8.3 ± 1.6° (p < 0.05), and decreased lateral bending from 8.0 ± 2.1 to 4.5 ± 1.1° (p < 0.05). Coupled lateral bending decreased from 0.62 ± 0.16 to 0.39 ± 0.15° for each degree of axial rotation (p < 0.05). Flexion-extension stiffness of the reconstructed segment with the prosthesis in the middle position did not deviate significantly from intact controls, whereas the lateral bending and axial rotation stiffness values were significantly larger than intact. Implanting the prosthesis in the posterior position as compared to the middle position did not significantly affect the ROM, motion coupling, or stiffness of the reconstructed segment; however, the COR location better approximated intact controls with the prosthesis midline located within ± 1 mm of the disc-space midline. Overall, the kinematic response after reconstruction with the compressible, six-degree-of-freedom prosthesis within ± 1 mm of the disc-space midline approximated the intact response in flexion-extension. Clinical studies are needed to understand and interpret the effects of limited restoration of lateral bending and axial rotation motions and motion coupling on clinical outcome.

Diagnosis and management of degenerative neck pain

Neck pain is a common presenting complaint, but the precise patho-aetiology is often unclear. Broadly speaking, the cause of neck pain can be considered as degenerative or non-degenerative (Table 1). While detailing the important non-degenerative causes the clinician should not miss, this article reviews the diagnosis and management of the common degenerative orthopaedic causes of neck pain.

History of cervical disc arthroplasty

Enthusiasm for cervical disc arthroplasty is based on the premise that motion-preserving devices attenuate the progression of adjacent-segment disease (ASD) in the cervical spine. Arthrodesis, on the other hand, results in abnormal load transfer on adjacent segments, leading to the acceleration of ASD. It has taken several decades of pioneering work to produce clinically relevant devices that mimic the kinematics of the intervertebral disc. The goal of this work is to trace the origins of cervical arthroplasty technology and highlight the attributes of devices currently available in the market.

Early results and review of the literature of a novel hybrid surgical technique combining cervical arthrodesis and disc arthroplasty for treating multilevel degenerative disc disease: opposite or complementary techniques?

We report the clinical and radiological results on the safety and efficacy of an unusual surgical strategy coupling anterior cervical discectomy and fusion and total disc replacement in a single-stage procedure, in patients with symptomatic, multilevel cervical degenerative disc disease (DDD). The proposed hybrid, single-stage, fusion-nonfusion technique aims either at restoring or maintaining motion where appropriate or favouring bony fusion when indicated by degenerative changes. Twenty-four patients (mean age 46.7 years) with symptomatic, multilevel DDD, either soft disc hernia or different stage spondylosis per single level, with predominant anterior myeloradicular compression and absence of severe alterations of cervical spine sagittal alignment, have been operated using such hybrid technique. Fifteen patients underwent a two-level surgery, seven patients received a three-level surgery and two a four-level procedure, for a total of 59 implanted devices (27 disc prostheses and 32 cages). Follow-up ranged between 12 and 40 months (mean 23.8 months). In all but one patient clinical follow-up (neurological examination, Nurick scale, NDI, SF-36) demonstrated significant improvement; radiological evaluation showed functioning disc prostheses (total range of motion 3-15 degrees ) and fusion through cages. None of the patients needed revision surgery for persisting or recurring symptoms, procedure-related complications or devices dislocations. To the authors' best knowledge, this is the first study with the longest available follow-up describing a different concept in the management of cervical multilevel DDD. Although larger series with longer follow-up are needed, in selected cases of symptomatic multilevel DDD, the proposed surgical strategy appears to be a safe and reliable application of combined arthroplasty and arthrodesis during a single surgical procedure.

Prognostic factors related to motion dynamics following cervical arthroplasty with a bryan disc: average 2-year follow-up

Background

This is a retrospective study to assess the prognostic factors influencing the postoperative motion dynamics and clinical outcome following cervical arthroplasty with a Bryan disc.

Methods

Twenty-seven patients (30 levels) consecutively underwent cervical arthroplasty using a Bryan disc (Medtronic Sofamor Danek, Memphis, Tennessee). Motion dynamics and clinical outcome (visual analogue score (VAS) and neck disability index (NDI) score) were examined preoperatively and at 1 month, 1 year, and final follow-up (average: 25 months). The prognostic factors influencing clinical outcome and postoperative motion dynamics were assessed.

Results

At last follow-up, mean VAS and NDI scores were significantly decreased from 8.33 ± 1.52 to 1.10 ± 0.99 (P = .001) and from 25.0 ± 15.9 to 9.2 ± 5.9 (P = .001), respectively. In a comparative study of pre- and postoperative motion changes at operated segments, mean segmental range of motion (ROM) increased from 6.96° ± 2.03° to 8.93° ± 3.53° (P = .014), and mean segmental angle decreased from 2.85° ± 3.27° to 1.21° ± 5.93° (P = .126). Mean global angle increased significantly from 14.54° ± 10.32° to 18.36° ± 11.10° (P = .003), and ROM increased non-significantly from 40.25° ± 13.51° to 41.56° ± 12.53° (P = .654). At upper and lower segments, ROMs did not change significantly postoperatively. The heights of functional segment units showed no change postoperatively (3.51 ± 0.21 to 3.49 ± 0.22, P = .701). No significant relationships were found between VAS and NDI improvement and changes in ROMs or segmental angles at last follow-up. Statistically, the postoperative functional segment unit (FSU) ROM decreased as the age of the patients increased (Spearman r = 0.391, P = .048). The gender and preoperative segmental ROM did not influence FSU ROM.

Conclusions

Our results demonstrate that cervical arthroplasty with the Bryan disc for the treatment of cervical degenerative provides a good clinical outcome and preserves motion postoperatively. The age of the patients and the preoperative segmental ROM significantly affect the postoperative FSU ROM. These factors however do not relate to the clinical outcome. The relationship between long-term outcome and these variables should be verified by a larger cohort study.

In vitro biomechanical comparison of cervical disk arthroplasty, ventral slot procedure, and smooth pins with polymethylmethacrylate fixation at treated and adjacent canine cervical motion units

OBJECTIVE

To compare the biomechanical properties of cervical arthroplasty to a ventral slot procedure and pin-polymethylmethacrylate (pin-PMMA) fixation.

SAMPLE POPULATION

Fresh cadaveric cervical (C2-T1) spines from 6 large dogs.

METHODS

Four spinal conditions were studied in each spinal specimen: intact, disk arthroplasty, ventral slot, and fixation with smooth pin-PMMA at C5-C6 intervertebral space. Axial compression, torsion, flexion-extension, and lateral bending moments were sequentially tested on each specimen for the 4 spinal conditions. Data from the C3-C4, C4-C5, C5-C6, and C6-C7 vertebral motion units (VMUs) were compared among treatments.

RESULTS

In axial compression and torsion, the ventral slot procedure allowed significantly less motion than intact, pin-PMMA, and arthroplasty groups at C5-C6. In lateral bending and flexion-extension, pin-PMMA had the least motion of C5-C6, followed by the arthroplasty group, intact spine, and ventral slot, all of which were significantly different from each other. Overall, the artificial disk was better able to mimic the behavior of the intact specimens compared with the ventral slot and pin-PMMA, producing similar displacements in axial compression and rotation in torsion, but more limited motion than intact in flexion-extension and in lateral bending.

CONCLUSION

Cervical spine specimens with an implanted prosthesis have biomechanical behaviors more similar to an intact spine compared with spinal specimens with ventral slot and pin-PMMA procedures. Cervical arthroplasty may then preserve some of the motion in the affected area after neural decompression while providing distraction.

CLINICAL RELEVANCE

Cervical arthroplasty should be further investigated in vivo to determine if it is a viable alternative to the ventral slot or pin-PMMA procedures for surgical treatment of cervical diseases in dogs and in particular for treatment of disk-associated caudal cervical spondylomyelopathy.

Quantitative anatomy of the endplate of the middle and lower cervical vertebrae in Koreans

STUDY DESIGN

Assessment of the size and shape of cervical vertebral endplates in Koreans.

OBJECTIVE

To obtain data regarding cervical vertebrae and propose an appropriate size for artificial discs in Koreans.

SUMMARY OF BACKGROUND DATA

The use of various types of cervical artificial discs has increased in recent years; hence, it is important to develop endplate implants of appropriate size. In this study, we determined the quantitative anatomy of cervical endplates in Koreans and proposed a new angular parameter.

METHODS

This study details the quantitative surface anatomy of the middle and lower cervical vertebral endplates based on the study of 272 cervical vertebrae in Korean cadavers. Computed tomographic images were obtained from 57 Korean cadavers (28 males and 29 females). The mean age and height were 51.14 years (range, 21-60 years) and 161 cm (range, 146-175 cm), respectively. The images were reconstructed, and linear parameters (EPWu, upper endplate width; EPDu, upper endplate depth; EPWl, lower endplate width; and EPDl, lower endplate depth) and an angular parameter (AUA, anterior wall to uncovertebral joint angle) were measured. RESULTS.: The width and depth of both the upper and lower endplates increased from C3 through C7. The EPDu, EPWl, and EPDl values of Koreans were similar to those reported in whites, while the EPWu value in this study were smaller than those reported in whites. The AUA for C4 differed significantly between the sexes. The linear parameter values obtained using Korean cadavers were compared with those obtained using white and Singaporean subjects. The EPWu values of Koreans were smaller than those reported in whites, while the values for all the parameters were considerably larger than those reported in Singaporeans. The AUA indicated the existence of various relationships between the endplate and the uncovertebral joint.

CONCLUSIONS

This data can be used to develop cervical devices for Koreans. The AUA should be studied in other populations.

Early Clinical and Radiologic Outcomes of Cervical Arthroplasty with Bryan Cervical Disc Prosthesis

Among 61 patients underwent disc replacement with the Bryan prosthesis, 47 patients were followed more than 3 months and their clinical and radiologic data were retrospectively analyzed to clarify very early clinical and radiologic outcomes and complications of disc arthroplasty with the Bryan Cervical Disc prosthesis during the learning period. Mean follow-up period was 6 months. Mean age was 45.6 years. Single-level procedure was done in 39 patients and 2-level in 8; a total of 55 levels replaced. Neck disability index improved from 59.8% to 22.9%. Visual analog pain score (VAS) of the neck improved from 8.4 to 1.6. VAS of shoulder/arm pain improved from 8.8 to 2.4. Mean patients' subjective improvement rate of symptoms was 71.1%. According to improvement in the neck disability index and VAS (over 50% improvement rate in each parameter), patients' subjective improvement rate (over 50%), and patients' satisfaction, the surgical success was achieved in 39 patients (83%). Eight patients (17%) showed failure. Mean segmental angle became more kyphotic after surgery from -0.7 degree of kyphosis (-11 to 7.7 degrees) to -1.3 degrees (-32 to 20.9 degrees) without statistical significance (P=0.55). Among 24 segments that showed preoperative kyphosis, 13 (54.2%) showed aggravated kyphosis, 7 (29.1%) showed decreased kyphosis and 4 (16.7%) recovered to lordosis. Among 31 segments that showed preoperative lordosis, 19 (61.3%) showed loss of lordosis and 12 (38.7%) showed increased lordosis. Mean range of motion increased significantly after surgery (6.7 to 8.5 degrees, P=0.04). Preoperative and postoperative segmental kyphosis was not related to clinical success. Cervical arthroplasty with the Bryan Cervical Disc prosthesis failed to restore segmental lordotic angle. A concern arises because it is well known that the fusion in kyphotic curvature causes more frequent problems on adjacent levels in anterior cervical discectomy and fusion. For the present, it seems preferable to exclude the patient who already has significant segmental kyphosis from disc arthroplasty with Bryan Cervical Disc prosthesis.

Cervical spine arthroplasty biomechanics

The advent of cervical intervertebral disc replacement represents an exciting and new frontier in the treatment of myelopathy and discogenic pain. The goal of most disc arthroplasty designs is to attempt to approximate the normal spinal motion as much as possible. This survey article provides a general overview as to the goals of cervical disc replacement, the current state of knowledge concerning how these devices have been evaluated, and a commentary on future work that should be performed to characterize these devices fully.

General Considerations for Cervical Arthroplasty with Technique for Prodisc-C

Motion-preserving spinal arthroplasty is a triumph of modern biomechanics, material sciences, and surgical technique. The ability to remove entire intervertebral discs and re-place them with prostheses that preserve height and alignment as well as motion and stability, all the while alleviating the pain and spinal cord compression, is the result of nearly 50 years of progress in joint arthroplasty. Although the clear benefit or danger of artificial cervical discs is still unknown, they are already fundamentally changing the field of cervical spine surgery and are undoubtedly going to establish their place in the armamentarium for spinal surgeons. Short-term follow-up studies indicate that cervical arthroplasty is as safe and effective as traditional fusion surgery, but follow-up studies are no longer needed.

Treatment of the painful motion segment: cervical arthroplasty

STUDY DESIGN

A retrospective review of the literature.

OBJECTIVE

This work serves as a comprehensive update of cervical arthroplasty.

SUMMARY OF BACKGROUND DATA

Cervical arthroplasty has developed as a means to preserve normal spinal motion after an anterior cervical discectomy. Preserving motion may lead to an acute improvement in patient outcome and may decrease the incidence of symptomatic adjacent segment disease in the long-term.

METHODS

The literature concerning the outcomes following anterior cervical decompression and fusion, the indications for cervical arthroplasty, the indications and contraindications for arthroplasty, the surgical technique, and early outcome studies for those devices currently in U.S. FDA IDE trials are reviewed.

RESULTS

The most data are available for the Prestige, Bryan, and ProDisc-C devices. While these devices all preserve normal segmental motion, the articulations vary (metal on metal, metal on polyurethane, and metal on ultra-high molecular weight polyethylene). Wear testing indicates that these devices will have a long life once implanted. Preliminary outcomes compare very favorably to anterior decompression and arthrodesis.

CONCLUSIONS

Cervical arthroplasty is a promising new technology that may improve patient outcome following anterior cervical decompression.