Sagittal alignment after Bryan cervical arthroplasty

Mid-term follow-up outcomes of single-level cervical total disc replacement versus anterior cervical discectomy and fusion for the treatment of cervical disc degenerative disease

BACKGROUND

The aim of the study was to evaluate the clinical and radiographic results of cervical total disc replacement (CTDR) and anterior cervical discectomy and fusion (ACDF) in the treatment of single-level cervical disc degenerative disease with a mid-term follow-up period.

METHODS

Seventy-two patients with C5/6 single-level cervical degenerative disc disease refractory to conservative interventions were randomly assigned to two groups: ACDF and CTDR. Clinical outcomes were assessed by using the Japanese Orthopedic Association (JOA) score and the neck disability index (NDI). Radiographic evaluations included range of motion (ROM), Cobb angles, heterotopic ossification (HO) and adjacent segment degeneration during follow-up.

RESULTS

Sixty-nine patients (35 CTDR and 34 ACDF) were followed up over 4 years (mean 50.3 months). At 1-month postoperation, the NDI scores in CTDR patients were significantly higher than those in ACDF patients, especially in the work, driving and recreation aspects. There was significant improvement in global ROM in CTDR patients than in ACDF patients. The postoperative ROM of the C4/5 segment in ACDF patients increased significantly, and no significant difference was shown in other adjacent segments. The occurrence of HO was 42.9% (15/35) in the CTDR group at the last follow-up, with Grade I in 3 cases, Grade II in 11 cases and Grade III in 1 case.

CONCLUSIONS

CTDR is an effective method in the treatment of single-level cervical disc degenerative disease. Compared to ACDF, CTDR is superior in the early improvement of quality of life, and restoration of segmental motion despite radiographic evidence of HO during a mid-term follow-up period.

Twenty-Year Radiographic Outcomes Following Single-Level Cervical Disc Arthroplasty: Results From a Prospective Randomized Controlled Trial

STUDY DESIGN

Prospective randomized controlled trial.

OBJECTIVE

Compare range of motion (ROM) and adjacent segment degeneration (ASD) following cervical disc arthroplasty (CDA) versus anterior cervical discectomy and fusion (ACDF) at 20-year follow-up.

SUMMARY OF BACKGROUND DATA

Anterior cervical discectomy and fusion is the standard of treatment for single-level cervical disc degeneration causing radiculopathy. CDA is claimed to reduce shear strain, and adjacent-level ROM changes are hypothesized to hasten ASD with ACDF.

MATERIALS AND METHODS

This study collected data on 47 patients randomized to ACDF or CDA. Lateral cervical spine radiographs were evaluated preoperatively, postoperatively, and at 20 years for alignment, ROM, ASD, and heterotopic ossification.

RESULTS

Eighty-two percent (18/22) of CDA patients and 84% (21/25) of ACDF patients followed up at 20 years. At 20 years, total cervical (C2-C7) ROM was statistically different between the CDA and fusion groups (47.8° vs . 33.4°, P =0.005). Total cervical ROM was not significantly different between preoperative and 20-year periods following CDA (45.6° vs . 47.4°, P =0.772) or ACDF (40.6° vs . 33.0°, P =0.192). Differences in postoperative and 20-year index-level ROM following CDA were not significant (10.1° vs . 10.2°, P =0.952). Final ASD grading was statistically lower following CDA versus ACDF at both adjacent levels ( P <0.005). Twenty-year adjacent-level ossification development was increased following ACDF versus CDA ( P <0.001). Polyethylene mean thickness decreased from 9.4 mm immediately postoperatively to 9.1 mm at 20-year follow up ( P =0.013). Differences in adjacent-level ROM from preoperative to 20-year follow-up in both the ACDF and CDA groups did not meet statistical significance ( P >0.05).

CONCLUSIONS

Cervical disc arthroplasty maintains index-level and total cervical ROM with very long-term follow-up. Total cervical ROM was higher at 20 years in CDA relative to ACDF. CDA results in lower rates of ASD and adjacent-level ossification development than ACDF.

Cervical Alignment Analysis Comparing Two-Level Cervical Disc Arthroplasty with Anterior Cervical Discectomy and Fusion with Anterior Plate Fixation

OBJECTIVE

This study assesses cervical alignments after 2-level cervical disc arthroplasty (CDA) versus anterior cervical discectomy and fusion (ACDF) with anterior plate fixation.

METHODS

Eighty-two patients who underwent 2-level CDA or ACDF in 2014-2019 were identified. Cervical alignment parameters were compared between the 2 cohorts. Subgroup analyses were performed to determine factors that differentiate alignment outcomes between the 2 procedures.

RESULTS

Although both cohorts achieved significant focal lordosis (FL) and overall cervical lordotic (CL) gains, CDA cohorts achieved significantly greater 12-month FL gain (P = 0.022). However, in a multivariate analysis controlling for preoperative variables, FL gain was no longer significant. Although the CDA cervical sagittal vertical axis (cSVA) significantly improved at 3 (P = 0.030) and 12 (P = 0.007) months, these improvements were not superior to the ACDF cSVA. Male patients undergoing CDA achieved greater 12-month CL gain. Patients undergoing CDA with body mass index >25 kg/m² achieved greater 12-month FL gain. Patients undergoing CDA with symptom duration >12 months achieved greater FL gain at 3 and 12 months. Patients undergoing CDA with high baseline T1 slope or cSVA achieved greater 12-month cSVA reduction. Clinical outcomes were comparable between the 2 cohorts. Unlike the ACDF group, CL gain in the CDA group was significantly correlated with the cSVA reduction, which was associated with significant improvement in the Neck Disability Index, arm pain, and 12-Item Short-Form Mental Component Scores. Heterotopic ossification was not found to significantly affect patient outcome and cervical alignment in both cohorts.

CONCLUSIONS

ACDF and CDA are viable options for 2-level degenerative disc disease in carefully selected patients. Both approaches produced equivalent postoperative alignment changes in a 2-level operation.

Viscoelastic cervical total disc replacement devices: Design concepts

Cervical disc replacement (CDR) is a motion-preserving surgical procedure for treating patients with degenerative disorders. Numerous reports of first generation CDR "ball-and-socket" articulating devices have shown satisfactory clinical results. As a result, CDR devices have been safely implemented in the surgeon's armamentarium on a global scale. However, only minor design improvements have been made over the last few years, as first generation CDRs devices were based on traditional synovial joint arthroplasty designs. As a consequence, these articulating designs have limited resemblance to the complex kinematic behavior of a natural disc. This has driven the development of deformable viscoelastic CDR devices to better mimic the biomechanical behavior of a natural disc. As a result, several viscoelastic CDR devices have been developed in recent years that vary in terms of materials, design and clinical outcomes. Since these viscoelastic CDR devices are fairly new, their weaknesses and strengths, which are related to their design characteristics, have not been well described. Therefore, this literature review discusses design related advantages and disadvantages of deformable viscoelastic CDR devices. As such, this paper can provide insight for surgeons and engineers on specific design characteristics of several viscoelastic devices and could potentially help to develop and design future implants. Eleven viscoelastic CDR devices were identified. An extensive database search on the devices' tradenames in Medline and PubMed was performed next. The devices were categorized based on common design characteristics to give an overview of both category and device specific complications and advantages. Overall, literature shows that most of these viscoelastic CDR devices can provide motion in all six degrees-of-freedom and have a variable center of rotation. Nevertheless, the viscoelastic materials used do not have an extensive history in orthopedics, so the long-term material behavior in vivo is still unknown. Although the viscoelastic devices have common benefits and risks, each specific design and category also has its own design related advantages and drawbacks that are described in this review. Altogether, viscoelastic total disc replacements seem to be a promising option for the future of cervical arthroplasty, but long-term clinical outcome is needed to confirm the advantages of mimicking the viscoelasticity of a natural disc.

Effect of Disc Height and Degree of Distraction on Heterotopic Ossification After Cervical Disc Replacement

BACKGROUND

Heterotopic ossification (HO) is a potential and severe complication of cervical disc replacement (CDR). However, the underlying mechanism of CDR and its association with preoperative disc height loss (DHL) and postoperative degree of distraction remain unclear. We hypothesized that DHL and postoperative degree of distraction could predict HO after CDR.

METHODS

Data were obtained from 127 patients who underwent single-level CDR with a minimum follow-up of 2 years. DHL and adjusted degree of distraction (ADD) were obtained from lateral radiographs, and HO was evaluated at the last follow-up appointment. Receiver operating characteristic curves were calculated to verify the diagnostic value of DHL and ADD in predicting HO.

RESULTS

Both DHL and ADD were significantly larger in the HO group than in the non-HO group (P < 0.05). DHL ≥24.97% increased the risk of HO by 5 times (P = 0.003, 95% confidence interval 1.62-15.49), and ADD ≥36.67% increased the risk of HO by 3.87 times (P < 0.001, 95% confidence interval 1.81-8.27). A combined DHL and ADD (combined parameter) cutoff of 60.36 had a sensitivity of 87.18%, specificity of 67.35%, and area under the curve of 0.77 for predicting HO.

CONCLUSIONS

DHL and ADD are associated with the development of HO after CDR. The cutoff value of DHL may narrow the criteria for CDR with the aim of reducing HO formation. The combined parameter may help surgeons to select the most suitable implant height to reduce the prevalence of HO.

Cervical Sagittal Alignment: Literature Review and Future Directions

Cervical alignment as a concept has come to the forefront for spine deformity research in the last decade. Studies on cervical sagittal alignment started from normative data, and expanded into correlation with global sagittal balance, prognosis of various conditions, outcomes of surgery, definition and classification of cervical deformity, and prediction of targets for ideal cervical reconstruction. Despite the recent robust research efforts, the definition of normal cervical sagittal alignment and cervical spine deformity continues to elude us. Further, many studies continue to view cervical alignment as a continuation of thoracolumbar deformity and do not take into account biomechanical features unique to the cervical spine that may influence cervical alignment, such as the importance of musculature connecting cranium-cervical-thoracic spine and upper extremities. In this article, we aim to summarize the relevant literature on cervical sagittal alignment, discuss key results, and list potential future direction for research using the '5W1H' framework; "WHO" are related?, "WHY" important?, "WHAT" to evaluate and "WHAT" is normal?, "HOW" to evaluate?, "WHEN" to apply sagittal balance?, and "WHERE" to go in the future?

Comparison of 10-year Outcomes of Bryan Cervical Disc Arthroplasty for Myelopathy and Radiculopathy

Objective

To evaluate the long‐term efficacy of Bryan cervical disc arthroplasty in the treatment of myelopathy patients compared with radiculopathy patients.

Methods

This study is a prospective study. Sixty‐six patients (38 patients in myelopathy group and 28 patients in radiculopathy group) who were treated with Bryan cervical disc arthroplasty between 2004 and 2007 and followed for 10 years were included in this study. The Japanese Orthopaedic Association (JOA) score, neck disability index (NDI), and Odom's criteria were used to evaluate the clinical outcomes. X‐ray, computed tomography (CT), and magnetic resonance imaging (MRI) were used to evaluate the radiographic outcomes including the global range of motion (ROM), segmental ROM, and segment alignment before the surgery and at last follow‐up. The incidence of segmental kyphosis, segmental mobility lost, and the grade of paravertebral ossification (PO) were also evaluated at last follow‐up.

Results

The JOA score and NDI improved in both groups. Thirty‐three of 38 patients in myelopathy group and all patients in radiculopathy group reported good or excellent outcomes according to Odom's criteria. The segmental ROM was (9.5° ± 4.4°) before surgery and maintained at (9.0° ± 5.5°) at last follow‐up in myelopathy group. The segmental ROM was (9.5° ± 4.6°) and (9.0° ± 5.3°) before surgery and at last follow‐up in radiculopathy group, respectively. The Bryan prosthesis remained mobile at last follow‐up for 30 patients (78.9%) in the myelopathy group and 22 patients (78.6%) in the radiculopathy group. Of the patients in the myelopathy group, 21.1% developed segmental kyphosis, as did 21.4% of patients in the radiculopathy group. The incidence of PO and high‐grade PO was 92.1 and 28.9% in the myelopathy group, and was 92.9 and 32.1% in the radiculopathy group. There was no significant difference between both groups.

Conclusions

Bryan cervical disc arthroplasty was an effective and safe technique in treating patients with myelopathy. The clinical and radiographic outcomes in the myelopathy group were similar to those in the radiculopathy group at the 10‐year follow‐up.

The association of cervical sagittal alignment with adjacent segment degeneration

Purpose

Cervical spine surgery may affect sagittal alignment parameters and induce accelerated degeneration of the cervical spine. Cervical sagittal alignment parameters of surgical patients will be correlated with radiological adjacent segment degeneration (ASD) and with clinical outcome parameters.

Methods

Patients were analysed from two randomized, double-blinded trials comparing anterior cervical discectomy with arthroplasty (ACDA), with intervertebral cage (ACDF) and without intervertebral cage (ACD). C2–C7 lordosis, T1 slope, C2–C7 sagittal vertical axis (SVA) and the occipito-cervical angle (OCI) were determined as cervical sagittal alignment parameters. Radiological ASD was scored by the combination of decrease in disc height and anterior osteophyte formation. Neck disability index (NDI), SF-36 PCS and MCS were evaluated as clinical outcomes.

Results

The cervical sagittal alignment parameters were comparable between the three treatment groups, both at baseline and at 2-year follow-up. Irrespective of surgical method, C2–C7 lordosis was found to increase from 11° to 13°, but the other parameters remained stable during follow-up. Only the OCI was demonstrated to be associated with the presence and positive progression of radiological ASD, both at baseline and at 2-year follow-up. NDI, SF-36 PCS and MCS were demonstrated not to be correlated with cervical sagittal alignment. Likewise, a correlation with the value or change of the OCI was absent.

Conclusion

OCI, an important factor to maintain horizontal gaze, was demonstrated to be associated with radiological ASD, suggesting that the occipito-cervical angle influences accelerated cervical degeneration. Since OCI did not change after surgery, degeneration of the cervical spine may be predicted by the value of OCI.

NECK trial

Dutch Trial Register Number NTR1289.

PROCON trial

Trial Register Number ISRCTN41681847.

Graphic abstract

These slides can be retrieved under Electronic Supplementary Material.

Does index level sagittal alignment determine adjacent level disc height loss?

OBJECTIVE

The authors sought to compare the effect of index level sagittal alignment on cephalad radiographic adjacent segment pathology (RASP) in patients undergoing cervical total disc arthroplasty (TDA) or anterior cervical discectomy and fusion (ACDF).

METHODS

This was a retrospective study of prospectively collected radiographic data from 79 patients who underwent TDA or ACDF and were enrolled and followed prospectively at two centers in a multicenter FDA investigational device exemption trial of the Bryan cervical disc prosthesis used for arthroplasty. Neutral lateral radiographs were obtained pre- and postoperatively and at 1, 2, 4, and up to 7 years following surgery. The index level Cobb angle was measured both pre- and postoperatively. Cephalad disc degeneration was determined by a previously described measurement of the disc height/anteroposterior (AP) distance ratio.

RESULTS

Sixty-eight patients (n = 33 ACDF; n = 35 TDA) had complete radiographs and were included for analysis. Preoperatively, there was no difference in the index level Cobb angle between the ACDF and TDA patients. Postoperatively, the ACDF patients had a larger segment lordosis compared to the TDA patients (p = 0.002). Patients who had a postoperative kyphotic Cobb angle were more likely to have undergone TDA (p = 0.01). A significant decrease in the disc height/AP distance ratio occurred over time (p = 0.035), by an average of 0.01818 at 84 months. However, this decrease was not influenced by preoperative alignment, postoperative alignment, or type of surgery.

CONCLUSIONS

In this cohort of patients undergoing TDA and ACDF, the authors found that preoperative and postoperative sagittal alignment have no effect on RASP at follow-up of at least 7 years. They identified time as the only significant factor affecting RASP.

Surgical Strategies to Prevent Adjacent Segment Disease in the Cervical Spine

The most popular approach to treating symptomatic cervical disk disease is anterior cervical discectomy and fusion. Although this procedure has significant long-term clinical success, it is associated with progressive adjacent segment degeneration with an annual incidence of ∼3%. Total disk arthroplasty was designed as an alternative to fusion that could preserve segmental motion at the operative level and potentially delay or prevent adjacent-level breakdown. The etiology of adjacent segment pathology (ASP) is multifactorial, and it is likely that most cases of ASP are unavoidable. When attempting to surgically prevent ASP, it is important to consider nonfusion alternatives, be judicious in one's level selection, and attempt to restore sagittal alignment. When ASP becomes a clinical problem, it is important to have an algorithm for how best to treat it.

Clinical and radiological outcomes of cervical disc arthroplasty: ten year follow-up study

PURPOSE

Previous studies have demonstrated that cervical disc arthroplasty has favourable short- and medium-term clinical and radiological outcomes. However, long-term follow-up outcomes have rarely been reported. The purpose of this study was to evaluate the ten year follow-up clinical and radiological outcomes in patients who underwent Bryan cervical disc arthroplasty.

METHODS

Seventy-one patients who underwent single-level Bryan cervical disc arthroplasty with a minimum ten year follow-up were included in the study. Japanese Orthopaedic Association (JOA) score, neck disability index (NDI), and Odom's criteria were used to evaluate clinical outcomes. X-ray, CT, and MRI were used to evaluate the radiological outcomes.

RESULTS

At last follow-up, the JOA score and NDI improved significantly, and 65 patients (91.5%) had good or excellent outcomes according to Odom's criteria. The range of motion (ROM) at operated level was 9.7° pre-operatively and maintained to 8.6° at last follow-up. The sagittal alignment of operated level was decreased from 2.1° pre-operatively to 1.2° at last follow-up (P < 0.01). The ROM and sagittal alignment of cervical spine had no significant change. At last follow-up, 16 patients (22.5%) developed segmental kyphosis, and 33 patients (46.5%) developed adjacent segment degeneration. Paravertebral ossification (PO) was observed in 66 patients (93.0%), and high-grade PO (grades III and IV) was observed in 25 patients (35.2%).

CONCLUSIONS

The clinical and radiological outcomes of Bryan cervical disc arthroplasty over ten years follow-up are satisfying. However, the occurrence of high-grade PO restricted the ROM of operated level.

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.

Cervical sagittal alignment after different anterior discectomy procedures for single-level cervical degenerative disc disease: randomized controlled trial

Background

The effect of anterior cervical discectomy without fusion (ACD), ACD with fusion by stand-alone cage (ACDF) or with arthroplasty (ACDA) on cervical sagittal alignment is not known and is the subject of this study.

Methods

A total of 142 adult patients with single-level cervical disease were at random allocated to different procedures: ACD (45), ACDF (47) and ACDA (50). Upright cervical spine radiographs were obtained. Angles of the involved angle and the angle between C2 and C7 were determined.

Results

After a mean follow-up of 25.4 ± 18.4 months, the angles of the involved level comparing ACD with ACDA and ACD with ACDF were different, reaching statistical significance. However, the angle between C2 and C7 did not differ between groups or between preoperative values and at follow-up.

Conclusions

Irrespective of the technique used for anterior cervical discectomy for single-level degenerative disc disease, the alignment of the cervical spine is unaltered.

Can segmental mobility be increased by cervical arthroplasty?

OBJECTIVE

Many reports have successfully demonstrated that cervical disc arthroplasty (CDA) can preserve range of motion after 1- or 2-level discectomy. However, few studies have addressed the extent of changes in segmental mobility after CDA or their clinical correlations.

METHODS

Data from consecutive patients who underwent 1-level CDA were retrospectively reviewed. Indications for surgery were medically intractable degenerative disc disease and spondylosis. Clinical outcomes, including visual analog scale (VAS)–measured neck and arm pain, Neck Disability Index (NDI), and Japanese Orthopaedic Association (JOA) scores, were analyzed. Radiographic outcomes, including C2–7 Cobb angle, the difference between pre- and postoperative C2–7 Cobb angle (ΔC2–7 Cobb angle), sagittal vertical axis (SVA), the difference between pre- and postoperative SVA (ΔSVA), segmental range of motion (ROM), and the difference between pre- and postoperative ROM (ΔROM), were assessed for their association with clinical outcomes. All patients underwent CT scanning, by which the presence and severity of heterotopic ossification (HO) were determined during the follow-up.

RESULTS

A total of 50 patients (mean age 45.6 ± 9.33 years) underwent a 1-level CDA (Prestige LP disc) and were followed up for a mean duration of 27.7 ± 8.76 months. All clinical outcomes, including VAS, NDI, and JOA scores, improved significantly after surgery. Preoperative and postoperative ROM values were similar (mean 9.5° vs 9.0°, p > 0.05) at each indexed level. The mean changes in segmental mobility (ΔROM) were −0.5° ± 6.13°. Patients with increased segmental mobility after surgery (ΔROM > 0°) had a lower incidence of HO and HO that was less severe (p = 0.048) than those whose ΔROM was < 0°. Segmental mobility (ROM) was significantly lower in patients with higher HO grade (p = 0.012), but it did not affect the clinical outcomes. The preoperative and postoperative C2–7 Cobb angles and SVA remained similar. The postoperative C2–7 Cobb angles, SVA, ΔC2–7 Cobb angles, and ΔSVA were not correlated to clinical outcomes after CDA.

CONCLUSIONS

Segmental mobility (as reflected by the mean ROM) and overall cervical alignment (i.e., mean SVA and C2–7 Cobb angle) had no significant impact on clinical outcomes after 1-level CDA. Patients with increased segmental mobility (ΔROM > 0°) had significantly less HO and similarly improved clinical outcomes than those with decreased segmental mobility (ΔROM < 0°).

10-year follow-up after implantation of the Bryan Cervical Disc Prosthesis

PURPOSE

Cervical arthroplasty is being used as an alternative for cervical fusion, but long-term follow-up results have rarely been reported. In this paper, we present 10-year follow-up results after implantation of the Bryan Cervical Disc Prosthesis in a single center.

METHODS

89 patients underwent implantation of a single-level Bryan Cervical Disc Prosthesis to treat radiculopathy and/or myelopathy. Clinical (Neurological Success, Neck Disability Index (NDI), Neck- and Arm-Pain, and SF-36) and radiological follow-up was prospectively organized up to 10 years after surgery. Adverse events and second surgeries were recorded and evaluated.

RESULTS

Ten-year follow-up data were available for 72 (81%) patients. Maintenance or improvement of the neurological state was seen in 89% of patients after 10-year follow-up. SF-36 PCS scores improved significantly at all follow-up points. SF-36 MCS improvement was significant at 4 and 6 year, but not at 8- and 10-year follow-up. Significant improvement for NDI, and Neck- and Arm-Pain scores was found for the subgroup of patients in whom these data were available. Mean angular motion of the prosthesis at 10-year follow-up was 8.6°. Mobility of the device, defined as >2° of angular motion, was reached in 81% of patients. During the study period, 21 patients (24%) developed new or recurrent radiculopathy or myelopathy, the majority of these being treated conservatively. Seven patients (8%) required 8 additional spine surgeries to treat persistent or recurrent symptoms. Of these, 2 patients (2%) were reoperated at the index level and at 5 (6%) an adjacent level.

CONCLUSION

In this study, favorable long-term clinical outcome after implantation of the Bryan Cervical Disc Prosthesis was seen, with the majority of prostheses remaining mobile after 10-year follow-up. However, still 6% of patients required adjacent level surgery.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Clinical trial registration no. NCT00389597 (clinicaltrials.gov)

Comparison of 2 Zero-Profile Implants in the Treatment of Single-Level Cervical Spondylotic Myelopathy: A Preliminary Clinical Study of Cervical Disc Arthroplasty versus Fusion

Objectives

Cervical disc arthroplasty (CDA) with Discover prosthesis or anterior cervical discectomy and fusion (ACDF) with Zero-P cage has been widely used in the treatment of cervical spondylotic myelopathy (CSM). However, little is known about the comparison of the 2 zero-profile implants in the treatment of single-level CSM. The aim was to compare the clinical outcomes and radiographic parameters of CDA with Discover prosthesis and ACDF with Zero-P cage for the treatment of single-level CSM.

Methods

A total of 128 consecutive patients who underwent 1-level CDA with Discover prosthesis or ACDF with Zero-P cage for single-level CSM between September 2009 and December 2012 were included in this study. Clinical outcomes were evaluated using the Japanese Orthopaedic Association (JOA) score and Neck Disability Index (NDI). For radiographic assessment, the overall sagittal alignment (OSA), functional spinal unit (FSU) angle, and range of motion (ROM) at the index and adjacent levels were measured before and after surgery. Additionally, the complications were also recorded.

Results

Both treatments significantly improved all clinical parameters (P < 0.05), without statistically relevant differences between the 2 groups. The OSA and FSU angle increased significantly in both groups (P <0.05). Compared with Zero-P group, ROMs at the index levels were well maintained in the Discover group (P < 0.05). However, there were no statistical differences in the ROMs of adjacent levels between the 2 groups (P > 0.05). Besides, no significant differences existed in dysphagia, subsidence, or adjacent disc degeneration between the 2 groups (P > 0.05). However, significant differences occurred in prosthesis migration in CDA group.

Conclusions

The results of this study showed that clinical outcomes and radiographic parameters were satisfactory and comparable with the 2 techniques. However, more attention to prosthesis migration of artificial cervical disc should be paid in the postoperative early-term follow-up.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Factors that may affect outcome in cervical artificial disc replacement: a systematic review

PURPOSE

To identify the factors that may affect outcome in C-ADR and provide the pooled results of postoperative success rate of implanted segment range of motion (ROM), incidence of heterotopic ossification (HO), incidence of radiographic adjacent segment degeneration (r-ASD)/adjacent segment disease (ASD), and surgery rate for ASD.

METHODS

We systematically searched in PubMed, Embase, Cochrane library and Web of knowledge from 2001 to May 2015. Two independent reviewers screened the primary records. Eleven questions regarding the effect of patient selection issues and radiographic parameters issues on outcome were posed previously. Studies addressing the framed questions were included for analysis.

RESULTS

Twenty-two studies were included for the final analysis. Results showed that number of surgical level (single versus double-level) had no effect on primary clinical outcome and radiographic outcome, surgical level had no effect on clinical and radiographic outcome, and smoking habits had negative effect on clinical outcome. No evidence for the effect of patient's age and pathology category (radiculopathy or myelopathy) on outcome was found. The overall success rate of ROM was 79.4%. ROM of the implanted segment and cervical sagittal alignment had no effects on clinical outcome. The pooled incidences of grade 1-4 HO and grade 3-4 HO were 27.7 and 7.8%, respectively. The pooled incidence of r-ASD and surgery rate for ASD were 42.4 and 3.8%, respectively.

CONCLUSIONS

The available evidence showed that most of the pre-selected factors had no effect on outcome after C-ADR, and the ROM success rate, incidence of HO and r-ASD/ASD, and surgery rate for ASD are acceptable. There is a lack of evidence from RCTs for some factors.

WITHDRAWN: 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.

A herniated disc in the neck often causes radiating pain, numbness, and weakness in muscles of the neck, shoulders, arms, and hands. It may also lead to symptoms in the trunk and legs.

When there is no or insufficient relief of symptoms with non‐surgical treatment, surgery can be an option. Traditional 'fusion' surgery involves fusion of the two bones of the spine (the vertebrae) that form the disc space. Motion between these two vertebrae is then no longer possible.

It has been suggested that this may cause the adjacent parts of the spine to become more mobile, as compensation. This in turn might accelerate normal wear and tear in these parts of the spine, which could lead to new symptoms. At present this is not confirmed.

Mobile disc prostheses have been introduced in an effort to reduce the amount of new symptoms at the longer term after surgery by preserving motion between the vertebrae involved. Long‐term results are not available yet. However, it is important to know whether disc arthroplasty is at least as effective as fusion in relieving symptoms, the primary aim of surgery.

In this review we have searched for all studies in which the patient receives one of these two possible treatments at random.

We identified nine studies (2400 participants), and considered five of these to have high methodological quality. This review shows that patients who were treated with a mobile disc prosthesis had less pain radiating to the arm one to two years after surgery, and less disability owing to these complaints. However, the actual differences were very small, only between 1 and 5 points on a 100‐point scale. The overall quality of the evidence was low to moderate, which means that including new studies in future years could change these conclusions. The conclusion that mobility is in fact preserved after placement of a mobile disc prosthesis, compared to traditional 'fusion' surgery, is unlikely to change. Whether this preserved mobility will lead to fewer new symptoms in the future is uncertain based on results for the first one to two years after surgery.

Therefore, a comparison of results in the long term (five years or more) will be made when more studies with long‐term results have become available.

Current concepts of anterior cervical discectomy and fusion: a review of literature

Anterior cervical discectomy and fusion (ACDF) is a safe and effective procedure for degenerative cervical spinal disease unresponsive to conservative management and its outstanding results have been reported. To increase fusion rates and decrease complications, numerous graft materials, cage, anterior plating and total disc replacement have been developed, and better results were reported from those, but still there are areas that have not been established. Therefore, we are going to analyze the treatment outcome with the various procedure through the literature review and determine the efficacy of ACDF.

Past, present, and future of cervical arthroplasty

Cervical arthroplasty was developed in an attempt to maintain cervical motion and potentially to avoid or minimize adjacent-segment degeneration. If cervical arthroplasty is successful, the long-term results of surgery for cervical disc disease should improve. However, problems associated with cervical arthroplasty have been reported: these include kyphosis, heterotopic ossification-induced motion limitation, no motion preservation even at the index level, and a higher revision rate in a limited number of cases compared with anterior cervical discectomy and fusion (ACDF). In addition, for degenerative cervical disc disorders, the risk of developing adjacent segment degeneration more than 2 years after surgery is reportedly similar for ACDF and cervical arthroplasty. Cervical disc arthroplasty is an emerging motion-sparing technology and is currently undergoing evaluation in many countries as an alternative to arthrodesis for the treatment of cervical radiculopathy and myelopathy. The decision whether to use arthrodesis or arthroplasty is a difficult one. The achievement of good prosthetic performance demands exacting implantation techniques to ensure correct placement. This fact underlines the increasing importance of special instrumentation and surgical skills that involve an understanding of prosthetic lubrication, wear, and biologic effects and familiarity with currently available information regarding kinematics, basic science, testing, and early clinical results. Fortunately, a number of devices are at the late preclinical study stage or at the early clinical trial stage, and results in many cases are promising. In the near future, it is likely that new designs will be produced to replace spinal discs totally or partially in a pathologic entity-specific manner.

Arthroplasty versus fusion in single-level cervical degenerative disc disease: a Cochrane review

STUDY DESIGN

A systematic review of randomized controlled trials (RCTs).

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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 compared with fusion, 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 1 of the 2 treatments are superior to the other in the first 1 to 2 years.

METHODS

We searched electronic databases for randomized controlled trials. We included randomized controlled trials that directly compared any type of cervical fusion with any type of cervical arthroplasty, with at least 1 year of follow-up. Study selection was performed independently by 3 review authors, and "risk of bias" assessment and data extraction were independently performed by 2 review authors. In case of missing data, we contacted the study authors or the study sponsor. We assessed the quality of evidence.

RESULTS

Nine studies (2400 participants) were included in this review; 5 of these studies had a low risk of bias. Results for the arthroplasty group were better than the fusion group for all primary comparisons, often statistically significant. For none of the primary outcomes was a clinically relevant difference in effect size shown. Quality of the evidence was low to moderate.

CONCLUSION

There is low to moderate quality evidence that results are consistently in favor of arthroplasty, often statistically significant. However, differences in effect size were invariably small and not clinically relevant for all primary outcomes.

LEVEL OF EVIDENCE

1.

Clinical and radiological follow-up of single-level Prestige LP cervical disc replacement

OBJECTIVE

To evaluate the clinical outcomes and radiographic results of patients who underwent single-level cervical arthroplasty using the Prestige LP.

METHOD

Thirty-one patients with single-level cervical disc disease received the Prestige LP disc replacement from June 2008 to December 2009. The neck disability index (NDI), Japanese Orthopedic Association score (JOA) and visual analogue scale (VAS) were used to assessed clinical outcomes pre-operatively and post-operatively at 24 months. The overall cervical alignment (C2-7 Cobb angle), the functional segmental unit (FSU) curvature, the range of motion (ROM) of treated and adjacent levels were measured, and the evidence of heterotopic ossification (HO) was observed from static and dynamic radiographs.

RESULTS

There was a statistically significant improvement in the NDI from 20.2 ± 7.5 to 6.4 ± 3.5 (P < 0.000), JOA from 12.8 ± 2.2 to 16.6 ± 0.6 (P < 0.000), the neck VAS score from 4.1 ± 2.5 to 1.4 ± 1.1 (P < 0.000), the arm VAS score from 4.6 ± 2.5 to 0.7 ± 1.1 (P < 0.000). The post-operative overall cervical alignment (9.3° ± 7.2°), ROM of treated level (7.6°) and adjacent level (upper level 9.4° ± 3.1°, lower level 9.1° ± 3.5°) are well maintained. The FSU were 0.2° ± 5.4° and 1.9° ± 5.5° at pre-operation and final follow-up with statistical significance (P = 0.011). Heterotopic ossification was evidenced in five operated segment (16 %).

CONCLUSIONS

The Prestige LP disc arthroplasty maintains favorable clinical outcomes, preserves the overall cervical alignment, FSU curvature, ROM of treated level and adjacent levels.

A meta-analysis comparing the results of cervical disc arthroplasty with anterior cervical discectomy and fusion (ACDF) for the treatment of symptomatic cervical disc disease

BACKGROUND

Anterior cervical discectomy and fusion is a standard treatment for symptomatic cervical disc disease, but pseudarthrosis and accelerated adjacent-level disc degeneration may develop. Cervical disc arthroplasty was developed to preserve the kinematics of the functional spinal unit. Trials comparing arthroplasty with anterior cervical discectomy and fusion have shown unclear benefits in terms of clinical results, neck motion at the operated level, adverse events, and the need for secondary surgical procedures.

METHODS

Only randomized clinical trials were included in this meta-analysis, and the search strategy followed the requirements of the Cochrane Library Handbook. Two reviewers independently assessed the methodological quality of each included study and extracted the relevant data.

RESULTS

Twenty-seven randomized clinical trials were included; twelve studies were Level I and fifteen were Level II. The results of the meta-analysis indicated longer operative times, more blood loss, lower neck and arm pain scores reported on a visual analog scale, better neurological success, greater motion at the operated level, fewer secondary surgical procedures, and fewer such procedures that involved supplemental fixation or revision in the arthroplasty group compared with the anterior cervical discectomy and fusion group. These differences were significant (p < 0.05). The two groups had similar lengths of hospital stay, Neck Disability Index scores, and rates of adverse events, removals, and reoperations (p > 0.05).

CONCLUSIONS

The meta-analysis revealed that anterior cervical discectomy and fusion was associated with shorter operative times and less blood loss compared with arthroplasty. Other outcomes after arthroplasty (length of hospital stay, clinical indices, range of motion at the operated level, adverse events, and secondary surgical procedures) were superior or equivalent to the outcomes after anterior cervical discectomy and fusion.

Kinematics of the cervical adjacent segments after disc arthroplasty compared with anterior discectomy and fusion: a systematic review and meta-analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

To determine the kinematics of the adjacent segments and global cervical spine after cervical arthroplasty compared with anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

Adjacent segment pathology after ACDF is a significant concern. Arthroplasty may decrease the risk of adjacent segment degeneration by maintaining normal spinal kinematics compared with fusion. However, the differences in the in vivo kinematics of the adjacent segments after cervical fusion versus arthroplasty have not been clearly established.

METHODS

A systematic literature review of studies comparing adjacent segment kinematic changes between fusion and arthroplasty was performed. We included randomized controlled trials and cohort studies that compared cervical arthroplasty with ACDF in adults with degenerative disease and reported on at least 1 outcome of interest. Meta-analysis was performed using a random-effects model where appropriate. The standardized mean difference of changes from baseline to follow-up between treatment groups was determined. Recommendations were made using Grades of Recommendation Assessment, Development, and Evaluation criteria.

RESULTS

We identified 12 studies, including 7 randomized controlled trials, 4 cohort studies, and 1 case-control study that evaluated kinematic measurements at the adjacent segments or the global cervical spine (C2-C7) after cervical arthroplasty compared with ACDF. We found no statistically significant differences between treatment groups in the change in range of motion (ROM) at the cranial or caudal adjacent segments from baseline to 2 years of follow-up. However, there was low evidence that the global cervical spine (C2-C7) had significantly greater change in ROM after arthroplasty compared with ACDF: patients had a greater angular ROM as measured up to 2 years after arthroplasty. We found no statistically significant differences between treatment groups in the change in the horizontal or vertical centers of rotation at the adjacent segments as measured up to 2 years after surgery. Regarding sagittal alignment, the cranial and caudal adjacent segments both became significantly more lordotic after arthroplasty compared with fusion at 1 to 2 years after surgery. However, there was no statistically significant difference between treatment groups in the change in global cervical sagittal alignment from baseline to 2 years. CONCLUSION.: There is no statistically or clinically significant difference in the adjacent segment ROM or centers of rotation after cervical arthroplasty compared with ACDF. However, the change in sagittal alignment at the cranial and caudal adjacent segments was significantly more lordotic after arthroplasty compared with fusion. In addition, although we found that there was no statistically significant difference between treatment groups in the change in global cervical (C2-C7) sagittal alignment, there was a significantly greater change in the angular ROM of the cervical spine at up to 2 years after arthroplasty than occurred after fusion.

CONSENSUS STATEMENT

Patients can be advised that single-level arthroplasty and ACDF result in clinically similar kinematic changes at short-term follow-up. Strength of Statement: Strong.

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.