Disc replacement using Pro-Disc C versus fusion: a prospective randomised and controlled radiographic and clinical study

Arthroplasty versus fusion in single-level cervical degenerative disc disease

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

Anterior cervical discectomy with arthroplasty versus arthrodesis for single-level cervical spondylosis: a systematic review and meta-analysis

OBJECTIVE

To estimate the effectiveness of anterior cervical discectomy with arthroplasty (ACDA) compared to anterior cervical discectomy with fusion (ACDF) for patient-important outcomes for single-level cervical spondylosis.

DATA SOURCES

Electronic databases (MEDLINE, EMBASE, Cochrane Register for Randomized Controlled Trials, BIOSIS and LILACS), archives of spine meetings and bibliographies of relevant articles.

STUDY SELECTION

We included RCTs of ACDF versus ACDA in adult patients with single-level cervical spondylosis reporting at least one of the following outcomes: functionality, neurological success, neck pain, arm pain, quality of life, surgery for adjacent level degeneration (ALD), reoperation and dysphonia/dysphagia. We used no language restrictions. We performed title and abstract screening and full text screening independently and in duplicate.

DATA SYNTHESIS

We used random-effects model to pool data using mean difference (MD) for continuous outcomes and relative risk (RR) for dichotomous outcomes. We used GRADE to evaluate the quality of evidence for each outcome.

RESULTS

Of 2804 citations, 9 articles reporting on 9 trials (1778 participants) were eligible. ACDA is associated with a clinically significant lower incidence of neurologic failure (RR = 0.53, 95% CI = 0.37-0.75, p = 0.0004) and improvement in the Neck pain visual analogue scale (VAS) (MD = 6.56, 95% CI = 3.22-9.90, p = 0.0001; Minimal clinically important difference (MCID) = 2.5. ACDA is associated with a statistically but not clinically significant improvement in Arm pain VAS and SF-36 physical component summary. ACDA is associated with non-statistically significant higher improvement in the Neck Disability Index Score and lower incidence of ALD requiring surgery, reoperation, and dysphagia/dysphonia.

CONCLUSIONS

There is no strong evidence to support the routine use of ACDA over ACDF in single-level cervical spondylosis. Current trials lack long-term data required to assess safety as well as surgery for ALD. We suggest that ACDA in patients with single level cervical spondylosis is an option although its benefits and indication over ACDF remain in question.

Motion analysis of single-level cervical total disc arthroplasty: a meta-analysis

OBJECTIVE

The purpose of this review was to investigate whether cervical total disc arthroplasty (CTDA) preserves motion of the treated level and what its effect is on adjacent segments.

METHODS

Relevant published reports were collected from PubMed, Medline and Cochrane library. The original studies were considered eligible only if the range of motion (ROM) of the index or adjacent level had been investigated. A meta-analysis was then performed on the collected data. Statistical heterogeneity across the various trials was tested using Cochran's Q statistic and I (2) ; in the case of heterogeneity, a random effect model was used.

RESULTS

The weighted mean differences (WMDs) of the index level were 0.34 (95% confidence interval [CI], -0.53∼1.21, P = 0.440) and 0.23 (95% CI, -1.92∼2.38, P = 0.834) in all included studies and randomized control trials (RCTs), respectively. The WMDs of the cranial adjacent levels, caudal adjacent levels and whole cervical spines were 1.01 (95% CI, 0.55∼1.47, P = 0.000), 1.10 (95% CI, 0.61∼1.59, P = 0.000) and 3.40 (95% CI, -6.02∼12.82, P = 0.479), respectively.

CONCLUSION

These findings suggest that the protective effect against adjacent segment degeneration provided by cervical arthroplasty might not be as good as has been believed. Long-term supporting evidence is still needed.

The use of self-mating PEEK as an alternative bearing material for cervical disc arthroplasty: a comparison of different simulator inputs and tribological environments

PURPOSE

The hypothesis for this study was that the simulated wear behavior of a hydroxyapatite coated, self-mating PEEK cervical disc arthroplasty device would be dependent on the simulated testing environment.

METHODS

Five groups of devices were evaluated under suggested ASTM and ISO load and motion profiles. The groups utilized different testing frequencies and protein content of simulator fluid, in addition to assessing the potential for third body wear. The average wear rates were determined using linear regression analysis with a generalized estimating equation. Significant differences between groups were determined using the Wald's test.

RESULTS

The simulated wear behavior was shown to be highly dependent on the testing environment, where protein content more than decreasing the cyclic loading frequency resulted in increased wear, but was not dependent on the suggested load and motion profiles. It was demonstrated that a self-mating PEEK cervical disc arthroplasty device has wear rates that are similar to existing material combinations for cervical disc arthroplasty.

CONCLUSIONS

This study showed that at a time when data from retrieval analyses is deficient, it is important to test the wear resistance of cervical disc arthroplasty devices under various conditions. Long-term clinical results and ongoing implant retrievals are required for validation between clinical performance and simulator inputs.

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.

Assessment of adjacent-segment mobility after cervical disc replacement versus fusion: RCT with 1 year's results

Disc prostheses have been designed to restore and maintain cervical segmental motion and reduce the accelerated degeneration of the adjacent level. There is no knowledge about the reaction of the neighboured asymptomatic segments after implantation of prostheses or fusion. The effects of these procedures to segmental movement of the uninvolved vertebrae have not been subjected to studies so far. The objective of this study was to compare the segmental motion following cervical disc replacement versus fusion and the correlation to the clinical outcome. Another aim was to compare the segmental motion of the asymptomatic segments above the treated ones and to compare both with Roentgen stereometric analysis (RSA) including the asymptomatic segments. 20 patients with one-level cervical radiculopathy scheduled for surgery were randomized to arthroplasty (10 patients, study group) or anterior cervical discectomy and fusion (10 patients, control group). Clinical results were evaluated using Visual Analogue Scale and Neck Disability Index. RSA was performed immediately postoperative, after 6 and 12 months. The adjacent segment showed a significantly higher segmental motion in all three-dimensional axes in comparison to the segment treated with prostheses (P < 0.05). In the fusion group the segmental motion of the adjacent segment was significantly higher in all three-dimensional axes (P < 0.05) at each examination time. When the adjacent level of both groups is compared, the fusion group could show a higher segmental motion in all three-dimensional axes, but without significant difference (P > 0.05) 1 year after surgery. Regarding the clinical results, there was no significant difference in pain relief between both groups (P > 0.05). In conclusion, the adjacent segment could show a higher segmental motion, when compared with the segment either treated with prostheses or fusion. There was no significant difference in segmental motion adjacent to prosthesis or fusion. Clinical results did also show no significant difference in pain relief between both groups.

A systematic review of randomized trials on the effect of cervical disc arthroplasty on reducing adjacent-level degeneration

OBJECT

Anterior cervical discectomy and fusion had been considered a safe and effective procedure for radiculopathy and myelopathy in the cervical spine, but degeneration in adjacent spinal levels has been a problem in some patients after fusion. Since 2002, cervical disc arthroplasty has been established as an alternative to fusion. The objective of this study was to review data concerning the role of cervical arthroplasty in reducing adjacent-level degeneration.

METHODS

A systematic review was performed using the MEDLINE, EMBASE, Cochrane, and LILACS databases, focusing on a structured question involving the population of interest, types of intervention, types of control, and outcomes studied.

RESULTS

No study has specifically compared the results of arthroplasty with the results of fusion with respect to the rate of postoperative development of adjacent-segment degenerative disease. One paper described a rate for adjacent-level surgery. The level of evidence of that paper was classified 2b, and although its authors found a statistically significant between-groups difference (arthroplasty vs fusion) using log-rank analysis, re-analysis according to number needed to treat (in the current paper) did not reveal statistical significance.

CONCLUSIONS

Adjacent-level degeneration has not been adequately studied in a review of the available randomized controlled trials on this topic, and there is no clinical evidence of reduction in adjacent-level degeneration with the use of cervical arthroplasty.

A new zero-profile implant for stand-alone anterior cervical interbody fusion

BACKGROUND

Several studies suggest fusion rates are higher with anterior cervical discectomy and fusion procedures if supplemented with a plate. However, plates may be associated with higher postoperative morbidity and higher rates of dysphagia. This led to the development of a cervical stand-alone cage with integrated fixation for zero-profile segmental stabilization.

QUESTIONS/PURPOSES

We asked whether this new implant would be associated with a low rate of dysphagia and other short-term complications in patients having anterior cervical discectomy and fusion and would be able to achieve solid fusion and maintain postoperative reduction in pain.

METHODS

We prospectively followed 38 patients with radiculopathy/myelopathy undergoing anterior cervical discectomy and fusion using the new implant. Intraoperative parameters, clinical features (Neck Pain Disability Index, visual analog scale score for neck/arm pain, Odom's criteria), and dysphagia scores were recorded. Radiographs were taken to assess implant failure. Thirty-four patients had a minimum 6 months' followup (mean, 8 months; range, 6-11 months).

RESULTS

Three patients at 6 weeks and one patient at 6 months complained about minor dysphagia-related symptoms. There was no hardware failure recordable and all patients had evidence of fusion. Compared to preoperatively, visual analog scale pain score and Neck Pain Disability Index were reduced at 6 weeks' followup without change during further followup.

CONCLUSIONS

The new cervical stand-alone anterior fusion device allows decompression and fusion with low complication rates. The incidence of chronic postoperative dysphagia was infrequent in comparison to published data. Prospective randomized trials with more patients and longer followup are necessary to confirm these observations.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Comparison between single- and multi-level patients: clinical and radiological outcomes 2 years after cervical disc replacement

In cervical multi-level degenerative pathology, considering the morbidity of the extensive fusion techniques, some authors advocate for the multilevel disc replacement. This study compared the safety and efficacy of disc replacement with an unconstrained prosthesis in multi- versus single-level patients. A total of 231 patients with cervical degenerative disc disease (DDD) who were treated with cervical disc replacement and completed their 24 months follow-up were analyzed prospectively: 175 were treated at one level, 56 at 2 levels or more. Comparison between both groups was based on usual clinical and radiological outcomes [Neck Disability Index (NDI), Visual Analog Scale (VAS), Range of Motion, satisfaction]. Safety assessments, including complication and subsequent surgeries, were also documented and compared. Mean NDI and VAS scores for neck and arm pain were improved in both groups similarly. Improvement of mobility at treated segments was also similar. Nevertheless, in the multi-level group, analgesic use was significantly higher and occurrence of Heterotopic Ossification significantly lower than in the single-level group. Subject satisfaction was nearly equal, as 94.2% of single-level group patients would undergo the surgery again versus 94.5% in the multi-level group. The overall success rate did not differ significantly. Multi-level DDD is a challenging indication in the cervical spine. This study showed no major significant clinical difference between the two groups. We need further studies to know more about the impact of multi-level arthroplasty, especially on the adjacent segments, but these results demonstrate initial safety and effectiveness in this patient sample.

Artificial total disc replacement versus fusion for the cervical spine: a systematic review

Cervical total disc replacement (CTDR) has been increasingly used as an alternative to fusion surgery in patients with pain or neurological symptoms in the cervical spine who do not respond to non-surgical treatment. A systematic literature review has been conducted to evaluate whether CTDR is more efficacious and safer than fusion or non-surgical treatment. Published evidence up to date is summarised qualitatively according to the GRADE methodology. After 2 years of follow-up, studies demonstrated statistically significant non-inferiority of CTDR versus fusion with respect to the composite outcome 'overall success'. Single patient relevant endpoints such as pain, disability or quality of life improved in both groups with no superiority of CTDR. Both technologies showed similar complication rates. No evidence is available for the comparison between CTDR and non-surgical treatment. In the long run improvement of health outcomes seems to be similar in CTDR and fusion, however, the study quality is often severely limited. After both interventions, many patients still face problems. A difficulty per se is the correct diagnosis and indication for surgical interventions in the cervical spine. CTDR is no better than fusion in alleviating symptoms related to disc degeneration in the cervical spine. In the context of limited resources, a net cost comparison may be sensible. So far, CTDR is not recommended for routine use. As many trials are ongoing, re-evaluation at a later date will be required. Future research needs to address the relative effectiveness between CTDR and conservative treatment.

No justification for cervical disk prostheses in clinical practice: a meta-analysis of randomized controlled trials

OBJECTIVE

A meta-analysis was performed to evaluate whether a beneficial clinical effect of cervical disk prostheses over conventional cervical diskectomy with fusion exists.

METHODS

A literature search was completed ending February 4, 2009, that included the abstract books of recent major spine congresses. All studies reported the results of single-level cervical disease without myelopathy. The Visual Analog Score (VAS) of the arm, VAS of the neck, Neck Disability Index, Physical Composite Scores of the Short Form 36, and Mental Composite Score of the Short Form 36, as well as adverse events, were evaluated.

RESULTS

Nine records were found, totaling 1533 patients. Of these, 1165 were evaluable at the last follow-up at 12 or 24 months. As an effect measure, a pooled odds ratio (OR) was calculated at 12 and 24 months. At 12 months, the VAS arm reached statistical significance (OR = 0.698; 95% confidence interval [CI], 0.571-0.853), as did the VAS neck (OR = 0.690; 95% CI, 0.562-0.847), and the Physical Composite Scores (OR = 1.362; 95% CI, 1.103-1.682) and the Mental Composite Score (OR = 1.270; 95% CI, 1.029-1.569) of the Short Form 36, favoring arthroplasty. The Neck Disability Index at 24 months also reached statistical difference (OR = 0.794; 95% CI, 0.641-0.984). All other measurements did not reveal any statistical difference. The number of complications, including secondary surgeries for adjacent segment disease, did not differ.

CONCLUSION

A clinical benefit for the cervical disk prosthesis is not proven. Because none of the studies were blinded, bias of the patient or researcher is a probable explanation for the differences found. Therefore, these costly devices should not be used in daily clinical practice.

SWISSspine: the case of a governmentally required HTA-registry for total disc arthroplasty: results of cervical disc prostheses

STUDY DESIGN

Prospective multicenter observational case-series.

OBJECTIVE

The goal of the SWISSspine registry is to generate evidence about the safety and efficiency of these Medtech innovations.

SUMMARY OF BACKGROUND DATA

The Swiss federal office of public health required a mandatory nationwide HTA-registry for cervical total disc arthroplasty (TDA), among other technologies, to decide about reimbursement of these interventions.

METHODS

Between March 2005 and June 2008, 808 interventions with implantation of 925 discs from 5 different suppliers were performed. Surgeon-administered outcome instruments were primary intervention, implant, and follow-up forms; patient self-reported measures were EQ-5D, COSS, and a comorbidity questionnaire. Data are recorded perioperative, at 3 months and 1 year postoperative, and annually thereafter. RESULTS. There was significant and clinically relevant reduction of neck (preoperative/postoperative 59.3/24.8 points) and arm pain (preoperative/postoperative 64.9/17.6) on visual analogue scale (VAS) and consequently decreased analgesics consumption. Similarly, quality of life (QoL) improved from preoperative 0.42 to postoperative 0.82 points on EQ-5D scale. There were 4 intraoperative complications and 23 revisions during the same hospitalization for 691 monosegmental TDAs, and 2 complications and 6 revisions for 117 2-level surgeries. A pharmacologically treated depression was identified as important risk factor for achieving a clinically relevant pain alleviation >20 points on VAS. Two-level surgery resulted in similar outcomes compared with the monosegmental interventions.

CONCLUSION

Cervical TDA appeared as safe and efficacious in short-term pain alleviation, consequent reduction of pain killer consumption, and in improvement of QoL. A clinically relevant pain reduction of ≥20 points was most probable if patients had preoperative pain levels ≥40 points on VAS. A pharmacologically treated depression and 2-level surgery were identified as risk factors for less pronounced pain alleviation or QoL improvement.

Cervical disc arthroplasty

This technology overview addressed four questions that compared the difference in outcomes between patients undergoing cervical disc arthroplasty with patients undergoing anterior cervical diskectomy fusion. Most studies did not either report or conduct the appropriate statistical analyses to examine predictive characteristics in patients with successful clinical outcomes. Most studies were inconclusive or unreliable regarding clinical outcomes and revision and/or complication rates in patients who present with neck and/or arm pain. No significant difference in the length of hospital stay was reported; however, two studies included in the overview reported that patients treated with cervical disc arthroplasty returned to work in significantly fewer days (range, 14 to 16 days) than did patients treated with anterior cervical diskectomy fusion.

Benchmarking in the SWISSspine registry: results of 52 Dynardi lumbar total disc replacements compared with the data pool of 431 other lumbar disc prostheses

The SWISSspine registry is the first mandatory registry of its kind in the history of Swiss orthopaedics and it follows the principle of "coverage with evidence development". Its goal is the generation of evidence for a decision by the Swiss federal office of health about reimbursement of the concerned technologies and treatments by the basic health insurance of Switzerland. Recently, developed and clinically implemented, the Dynardi total disc arthroplasty (TDA) accounted for 10% of the implanted lumbar TDAs in the registry. We compared the outcomes of patients treated with Dynardi to those of the recipients of the other TDAs in the registry. Between March 2005 and October 2009, 483 patients with single-level TDA were documented in the registry. The 52 patients with a single Dynardi lumbar disc prosthesis implanted by two surgeons (CE and OS) were compared to the 431 patients who received one of the other prostheses. Data were collected in a prospective, observational multicenter mode. Surgery, implant, 3-month, 1-year, and 2-year follow-up forms as well as comorbidity, NASS and EQ-5D questionnaires were collected. For statistical analyses, the Wilcoxon signed-rank test and chi-square test were used. Multivariate regression analyses were also performed. Significant and clinically relevant reduction of low back pain and leg pain as well as improvement in quality of life was seen in both groups (P < 0.001 postop vs. preop). There were no inter-group differences regarding postoperative pain levels, intraoperative and follow-up complications or revision procedures with a new hospitalization. However, significantly more Dynardi patients achieved a minimum clinically relevant low back pain alleviation of 18 VAS points and a quality of life improvement of 0.25 EQ-5D points. The patients with Dynardi prosthesis showed a similar outcome to patients receiving the other TDAs in terms of postoperative low back and leg pain, complications, and revision procedures. A higher likelihood for achieving a minimum clinically relevant improvement of low back pain and quality of life in Dynardi patients was observed. This difference might be due to the large number of surgeons using other TDAs compared to only two surgeons using the Dynardi TDA, with corresponding variations in patient selection, patient-physician interaction and other factors, which cannot be assessed in a registry study.

Fusion versus disk replacement for degenerative conditions of the lumbar and cervical spine: quid est testimonium?

This article compares the outcomes following spinal fusion and disk replacement for degenerative conditions of the lumbar and cervical spine. The short-term outcomes of lumbar and cervical total disk replacement are equivalent to that following spinal fusion. Long-term follow-up studies of total disk replacement are necessary to confirm its potential benefit in reducing or preventing adjacent level degeneration. Also discussed is the philosophy of the surgical management of degenerative conditions of the lumbar and cervical spine.

Anterior cervical discectomy with fusion in patients with cervical disc degeneration: a prospective outcome study of 258 patients (181 fused with autologous bone graft and 77 fused with a PEEK cage)

Background

Anterior cervical discectomy with fusion (ACDF) is challenging with respect to both patient selection and choice of surgical procedure. The aim of this study was to evaluate the clinical outcome of ACDF, with respect to both patient selection and choice of surgical procedure: fusion with an autologous iliac crest graft (AICG) versus fusion with an artificial cage made of polyetheretherketone (PEEK).

Methods

This was a non-randomized prospective single-center outcome study of 258 patients who underwent ACDF for cervical disc degeneration (CDD). Fusion was attained with either tricortical AICG or PEEK cages without additional anterior plating, with treatment selected at surgeon's discretion. Radicular pain, neck-pain, headache and patient satisfaction with the treatment were scored using the visual analogue scale (VAS).

Results

The median age was 47.5 (28.3-82.8) years, and 44% of patients were female. 59% had single-level ACDF, 40% had two level ACDF and 1% had three-level ACDF. Of the patients, 181 were fused with AICG and 77 with a PEEK-cage. After surgery, the patients showed a significant reduction in radicular pain (ΔVAS = 3.05), neck pain (ΔVAS = 2.30) and headache (ΔVAS = 0.55). Six months after surgery, 48% of patients had returned to work: however 24% were still receiving workers' compensation.

Using univariate and multivariate analyses we found that high preoperative pain intensity was significantly associated with a decrease in pain intensity after surgery, for all three pain categories. There were no significant correlations between pain relief and the following patient characteristics: fusion method (AICG or PEEK-cage), sex, age, number of levels fused, disc level fused, previous neck surgery (except for neck pain), previous neck trauma, or preoperative symptom duration. Two hundred out of the 256 (78%) patients evaluated the surgical result as successful. Only 27/256 (11%) classified the surgical result as a failure. Patient satisfaction was significantly associated with pain relief after surgery.

Conclusions

ACDF is an effective treatment for radicular pain in selected patients with CDD after six months follow up.

Because of similar clinical outcomes and lack of donor site morbidity when using PEEK, we now prefer fusion with PEEK cage to AICG.

Lengthy symptom duration was not a negative prognostic marker in our patient population.

The number of patients who returned to work 6 months after surgery was lower than expected.

Overview of disc arthroplasty-past, present and future

Degenerative disc disease is one of the most frequent spinal disorders. The anatomy and the biomechanics of the intervertebral disc are very complex, and the pathomechanics of its degeneration are poorly understood. Despite this complexity and uncertainty, great advances have been made in the field of disc replacement technology, with promising results. Difficulties are continuously being encountered, but careful analysis of the results and intensive research and development will assist in countering these problems. There are approximately 40 clinical reports in the literature describing various aspects of randomised controlled trials involving intervertebral disc arthroplasty. However, the majority of these publications do not provide reliable information, in that they give only interim results and/or the results from just one of the many centres in multicentre studies. Such publications must be interpreted with caution, since they do not always represent the results of the whole study population and may hence be underpowered. We identified six randomised controlled trials that compared the final clinical outcomes of disc arthroplasty and spinal fusion. The present systematic review attempts to give an overview of the current status of disc arthroplasty.

Clinical results and development of heterotopic ossification in total cervical disc replacement during a 4-year follow-up

Cervical total disc replacement (CTDR) aims to decrease the incidence of adjacent segment disease through motion preservation in the operated disc space. Ongoing data collection and increasing number of studies describing heterotopic ossification (HO) resulting in decreased mobility of implants, forced us to carefully evaluate our long-term clinical and morphological results of patients with CTDR. We present the first 54 consecutive patients treated with 65 ProdiscC prostheses during a 12-month period (2/2004-3/2005). All patients signed an informed consent and were included in prospective long-term study approved by hospital ethical committee. The 1- and 2-year follow-up analysis were available for all patients included and 4-year results for 50 patients (60 implants). Clinical (neck disability index-NDI, visual analog scale-VAS) and radiological follow-up was conducted at 1-, 2- and 4-years after the procedure. The Mehren/Suchomel modification of McAfee scale was used to classify the appearance of HO. Mean preoperative NDI was 34.5%, VAS for neck pain intensity 4.6 and VAS for arm pain intensity 5.0. At 1-, 2- and 4-year follow-up, the mean NDI was 30.7, 27.2, and 30.4, mean VAS for neck pain intensity 2.5, 2.1 and 2.9 and mean VAS for arm pain intensity pain 2.2, 1.9 and 2.3, respectively. Significant HO (grade III) was present in 45% of implants and segmental ankylosis (grade IV) in another 18% 4 years after intervention. This finding had no clinical consequences and 92% of patients would undergo the same surgery again. Our clinical results (NDI, VAS) are comparable with fusion techniques. Although, advanced non-fusion technology is used, a significant frequency of HO formation and spontaneous fusion in cervical disc replacement surgery must be anticipated during long-term follow-up.

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

The interest in cervical total disc replacement (TDR) as an alternative to the so-far gold standard in the surgical treatment of degenerative disc disease (DDD), e.g anterior cervical discectomy and fusion (ACDF), is growing very rapidly. Many authors have established the fact that ACDF may result in progressive degeneration in adjacent segments. On the contrary, but still theoretically, preservation of motion with TDR at the surgically treated level may potentially reduce the occurrence of adjacent-level degeneration (ALD). The authors report the intermediate results of an undergoing multicentre prospective study of TDR with Mobi-C prosthesis. The aim of the study was to assess the safety and efficacy of the device in the treatment of DDD and secondary to evaluate the radiological status of adjacent levels and the occurrence of ossifications, at 2-year follow-up (FU). 76 patients have performed their 2-year FU visit and have been analyzed clinically and radiologically. Clinical outcomes (NDI, VAS, SF-36) and ROM measurements were analyzed pre-operatively and at the different post-operative time-points. Complications and re-operations were also assessed. Occurrences of heterotopic ossifications (HOs) and of adjacent disc degeneration radiographic changes have been analyzed from 2-year FU X-rays. The mean NDI and VAS scores for arm and neck are reduced significantly at each post-operative time-point compared to pre-operative condition. Motion is preserved over the time at index levels (mean ROM = 9 degrees at 2 years) and 85.5% of the segments are mobile at 2 years. HOs are responsible for the fusion of 6/76 levels at 2 years. However, presence of HO does not alter the clinical outcomes. The occurrence rate of radiological signs of ALD is very low at 2 years (9.1%). There has been no subsidence, no expulsion and no sub-luxation of the implant. Finally, after 2 years, 91% of the patients assume that they would undergo the procedure again. These intermediate results of TDR with Mobi-C are very encouraging and seem to confirm the efficacy and the safety of the device. Regarding the preservation of the status of the adjacent levels, the results of this unconstrained device are encouraging, but longer FU studies are needed to prove it.

Comparison of radiographic changes after ACDF versus Bryan disc arthroplasty in single and bi-level cases

The object of this study is to compare radiographic outcomes of anterior cervical decompression and fusion (ACDF) versus cervical disc replacement using the Bryan Cervical Disc Prosthesis (Medtronic Sofamor Danek, Memphis, TN) in terms of range of motion (ROM), Functional spinal unit (FSU), overall sagittal alignment (C2-C7), anterior intervertebral height (AIH), posterior intervertebral height (PIH) and radiographic changes at the implanted and adjacent levels. The study consisted of 105 patients. A total of 63 Bryan disc were placed in 51 patients. A single level procedure was performed in 39 patients and a two-level procedure in the other 12. Fifty-four patients underwent ACDF, 26 single level cases and 28 double level cases. The Bryan group had a mean follow-up 19 months (12-38). Mean follow-up for the ACDF group was 20 months (12-40 months). All patients were evaluated using static and dynamic cervical spine radiographs as well as MR imaging. All patients underwent anterior cervical discectomy followed by autogenous bone graft with plate (or implantation of a cage) or the Bryan artificial disc prosthesis. Clinical evaluation included the visual analogue scale (VAS), and neck disability index (NDI). Radiographic evaluation included static and dynamic flexion-extension radiographs using the computer software (Infinitt PiviewSTAR 5051) program. ROM, disc space angle, intervertebral height were measured at the operative site and adjacent levels. FSU and overall sagittal alignment (C2-C7) were also measured pre-operatively, postoperatively and at final follow-up. Radiological change was analyzed using chi(2) test (95% confidence interval). Other data were analyzed using the mixed model (SAS enterprises guide 4.1 versions). There was clinical improvement within each group in terms of VAS and NDI scores from pre-op to final follow-up but not significantly between the two groups for both single (VAS p=0.8371, NDI p=0.2872) and double (VAS p=0.2938, NDI p=0.6753) level surgeries. Overall, ROM and intervertebral height was relatively well maintained during the follow-up in the Bryan group compared to ACDF. Regardless of the number of levels operated on, significant differences were noted for overall ROM of the cervical spine (p<0.0001) and all other levels except at the upper adjacent level for single level surgeries (p=0.2872). Statistically significant (p<0.0001 and p=0.0172) differences in the trend of intervertebral height measurements between the two groups were noted at all levels except for the AIH of single level surgeries at the upper (p=0.1264) and lower (p=0.7598) adjacent levels as well as PIH for double level surgeries at the upper (p=0.8363) adjacent level. Radiological change was 3.5 times more observed for the ACDF group. Clinical status of both groups, regardless of the number of levels, showed improvement. Although clinical outcomes between the two groups were not significantly different at final follow-up, radiographic parameters, namely ROM and intervertebral heights at the operated site, some adjacent levels as well as FSU and overall sagittal alignment of the cervical spine were relatively well maintained in Bryan group compared to ACDF group. We surmise that to a certain degree, the maintenance of these parameters could contribute to reduce development of adjacent level change. Noteworthy is that radiographic change was 3.5 times more observed for ACDF surgeries. A longer period of evaluation is needed, to see if all these radiographic changes will translate to symptomatic adjacent level disease.

Cervical intradiscal radiofrequency lesioning: a feasiblity study

OBJECTIVE

The objective of this benchtop study was to establish if single site, long duration intradiscal radiofrequency (RF) at two different positions could generate adequate heating throughout the intervertebral disc to potentially ablate intradiscal nociceptors.

DESIGN

The disarticulated cervical spines from four fresh frozen cadavers were studied. Temperature recording was completed from two different positions of the RF needle. The needle was either placed in the middle of the disc in four discs, or it was inserted in the posterior quarter of the disc, in eight discs. Thermocouple measurements were made every 2 minutes from three positions: middle of the disc, posterolateral aspect of the disc, and in the anterior third of the disc.

SETTING

Fluoroscopy suite.

MATERIALS

Disarticulated cervical spine specimens.

INTERVENTIONS

Intradiscal RF lesioning in the middle and posterior portion of the cervical disc at 85 degrees C for 10 minutes.

OUTCOME MEASURES

Local temperature within the disc.

RESULTS

Lesioning in either the middle or posterior portion of the disc failed to provide sufficient temperature increases throughout the cervical disc to achieve adequate denervation.

CONCLUSIONS

As in the lumbar spine, intradiscal cervical RF provides too focal a thermal profile to effectively denervate the disc even in an ex vivo experiment. Thus, single site, long duration cervical intradiscal RF lesioning in vivo cannot be recommended.

Biomechanical studies on cervical total disc arthroplasty: a literature review

BACKGROUND

Many models of cervical disc prostheses are currently commercially available or under clinical trial, and are based on several design concepts and built employing different materials. This paper is targeted to the understanding of the possible relationships between the geometrical, mechanical and material properties of the various cervical disc prostheses and the restoration of a correct biomechanics of the implanted spine.

METHODS

Papers about cervical disc arthroplasty, based on ex vivo testing, mathematical models, and radiographic measurements, were included in the present review.

FINDINGS

Although disc arthroplasty was found to be generally able to preserve a nearly physiological motion in the cervical spine, several alterations in the spine biomechanics due to disc arthroplasty were reported in the literature. An increase of the range of motion at the implanted level was observed in some ex vivo studies. Loss of mobility and heterotopic ossification were reported in radiographic investigations. Loss of lordosis at the implanted level was detected as well. Wear debris was usually found very limited and device stability seemed not to be an actual problem.

INTERPRETATION

The possible relationships between the observed alterations in the spine biomechanics after disc arthroplasty and the properties of the various cervical disc prostheses have been reviewed. Clinical studies are needed to assess the validity of the considerations inferred from the biomechanical papers.

Comparative analysis of cervical arthroplasty using mobi-c(r) and anterior cervical discectomy and fusion using the solis(r) -cage

OBJECTIVE

Although anterior cervical discectomy and fusion (ACDF) is the standard treatment for degenerative cervical disc disease, concerns regarding adjacent level degeneration and loss of motion have suggested that arthroplasty may be a better alternative. We have compared clinical and radiological results in patients with cervical disc herniations treated with arthroplasty and ACDF.

METHODS

We evaluated 53 patients treated for cervical disc herniations with radiculopathy, 21 of whom underwent arthroplasty and 32 of whom underwent ACDF. Clinical results included the Visual Analogue Scale (VAS) score for upper extremity radiculopathy, neck disability index (NDI), duration of hospital stay and convalescence time. All patients were assessed radiologically by measuring cervical lordosis, segmental lordosis and segmental range-of-movement (ROM) of operated and adjacent disc levels.

RESULTS

Mean hospital stay (5.62 vs. 6.26 days, p<0.05) and interval between surgery and return to work (1.10 vs. 2.92 weeks, p<0.05) were significantly shorter in the arthroplasty than in the fusion group. Mean NDI and extremity VAS score improved after 12 months in both groups. Although it was not significant, segmental ROM of adjacent levels was higher in the fusion group than in the arthroplasty group. And, segmental motion of operated levels in arthroplasty group maintained more than preoperative value at last follow up.

CONCLUSION

Although clinical results were similar in the two groups, postoperative recovery was significantly shorter in the arthroplasty group. Although it was not significant, ROM of adjacent segments was less in the arthroplasty group. Motion of operated levels in arthroplasty group was preserved at last follow up.

The prevalence of indications and contraindications to cervical total disc replacement

BACKGROUND CONTEXT

Although the prevalence of indications and contraindications to lumbar total disc replacement (TDR) has been evaluated, no study to date has quantified the potential candidacy for cervical disc replacement in practice.

PURPOSE

To report the potential candidacy rate for cervical TDR from both an academic and private practice spine surgery setting.

STUDY DESIGN/SETTING

Retrospective case series.

PATIENT SAMPLE

Patient record review of 167 consecutive patients who underwent cervical spine surgery by 1 of 2 orthopedic spine surgeons between January 1, 2003 and January 1, 2005.

OUTCOME MEASURES

Evaluation of potential candidacy for cervical TDR, with emphasis on both contraindications and indications.

METHODS

In this study, we used the published contraindications and indications listed in trials of four different cervical disc arthroplasty devices: ProDisc-C (Synthes Spine, West Chester, PA), PRESTIGE LP (Medtronik Sofamor Danek, Memphis, TN), Bryan Cervical Disc prosthesis (Medtronik Sofamor Danek, Memphis, TN), and Porous Coated Motion (PCM; Cervitech, Rockaway, NJ). The proportion of patients who met both inclusion and exclusion criteria was calculated. We also examined the proportion of patients who would be candidates for cervical TDR if the indications were expanded to include the treatment for adjacent segment disease (ASD).

RESULTS

Of the 167 patients (mean age 50.8 years, range 20-89 years) reviewed, 91.6% (153/167) had fusion surgery and 8.4% (14/167) had nonfusion surgery. Fifty-seven percent (95/167) had absolute contraindications to cervical TDR, and within this group the average number of contraindications was 2.1 (SD=1.2, range 0-5). Forty-three percent (72/167) met the strict inclusion criteria, and had no exclusion criteria. If the indications were expanded to include treatment for ASD, an additional 4.2% (7/167) of the patients would have qualified as candidates for cervical TDR.

CONCLUSIONS

Compared with lumbar TDR, total disc replacement may have a larger potential role in the treatment of cervical degenerative conditions, as 43% of patients would have met the strict criteria for TDR candidacy, or 47% if the indications were expanded to include treatment for ASD.