Heterotopic ossification and clinical outcome in nonconstrained cervical arthroplasty 2 years after surgery: the Norwegian Cervical Arthroplasty Trial (NORCAT)

Incidence of Heterotopic Ossification at 10 years After Cervical Disk Replacement: A Systematic Review and Meta-analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

This study aimed to assess the incidence of heterotopic ossification (HO) 10 years after cervical disk replacement (CDR).

SUMMARY OF BACKGROUND DATA

HO is a common complication after CDR and may limit the range of motion of the artificial disk. As HO usually progresses slowly, a long-term follow-up is required to better understand its incidence. In recent years, the increasing number of original articles reporting 10-year outcomes gives us the opportunity to better understand the long-term incidence of HO.

MATERIALS AND METHODS

We searched PubMed, Medline, Embase, and Cochrane Library databases to identify eligible studies. The incidence of HO was pooled, and subgroup analysis was performed. Meta-regression analyses were conducted to identify factors contributing to heterogeneity.

RESULTS

Eleven studies with at least 10 years of follow-up comprising 1140 patients who underwent CDR were included. The pooled incidence of overall HO was 70% (95% CI, 60%-81%) at 10 years postoperatively, 60% (95% CI, 44%-75%) at five or six years postoperatively, and 50% (95% CI, 27%-72%) at one or two years postoperatively. The pooled incidence of severe HO (grade 3 or 4) was 37% (95% CI, 29%-45%), and mild HO (grade 1 to 2) was 30% (95% CI, 17%-44%) at 10 years of follow-up. Pooled range of motion decreased from 8.59° before surgery to 7.40° 10 years after surgery. Subgroup analysis showed that HO incidence differed according to the prosthesis type. The earlier publication was associated with a higher pooled incidence of severe HO in the meta-regression analysis.

CONCLUSIONS

This is the first meta-analysis providing detailed information on the pooled 10-year incidence of HO after CDR. The incidence of HO seems to increase with the length of follow-up.

LEVEL OF EVIDENCE

3.

The residual exposed endplate ratio is predictive of posterior heterotopic ossification after cervical Bryan disc arthroplasty

OBJECTIVES

Heterotopic ossification (HO), a major cause of dysfunction after disc arthroplasty (CDA). The aim of this study was to determine the cut value of the residual exposed endplate (REE) ratio and to predict the development of posterior HO after Bryan CDA.

METHODS

This retrospective study investigated the relationship between the REE ratio and posterior HO formation after Bryan CDA. Consecutive adult patients who underwent 1- or 2-level Bryan CDA by a single neurosurgeon between 2006 and 2016 with at least two years follow-up were included. Postoperative radiographic analysis and measurement were performed to obtain the REE ratio and the HO grade.

RESULTS

Of 249 patients with 384 surgical levels who underwent Bryan CDA during the study period, 114 (45.8 %) received 1-level CDA and 135 (54.2 %) received 2-level CDA. Lateral radiographs showed that 169 implants (44 %) had posterior HOs in all grades after two years or more of follow up and 14 implants (3.64 %) had severe HO (McAfee grades 3 and 4). In 329 implants (85.7 %), a comparison of radiographs to CT examination of HO grading showed a substantial relationship. Using area under the curve (AUC) analysis, a REE ratio >9 %, with 65.1 % sensitivity and 86.5 % specificity, was the cut point for posterior HO formation.

CONCLUSIONS

REE is highly correlated with the development of postoperative posterior HO after Bryan CDA, regardless of the level of implantation. An undersized implant causing a REE ratio >9 % is a predictor of postoperative posterior HO formation after cervical Bryan CDA.

Cervical Total Disc Replacement: Expanded Indications

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

Cervical Total Disc Replacement: Indications and Technique

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

Adjacent-Level Ossification Development in Single-Level Standalone Anterior Cervical Discectomy and Fusion Versus Anterior Cervical Discectomy and Fusion With Plate

STUDY DESIGN

Retrospective case control study.

OBJECTIVES

Adjacent-level ossification development (ALOD) is a distinct form of adjacent segmental degeneration that has been recognized to occur after anterior cervical discectomy and fusion (ACDF). It is unclear whether ACDF with plate versus standalone has an effect on rates of ALOD. This retrospective case-control study aims to assess the rate of ALOD in a large series of patients undergoing ACDF with and without plate and factors causing ALOD.

METHODS

Data was collected for patients undergoing ACDF from January 2009 to July 2016. Data collected was from multiple centers and included demographic data, surgical data, radiological imaging at time of surgery, and serial follow-up imaging. The radiology for ALOD was independently reviewed. Cohorts were divided into ACDF with plate (Group P = plate) and ACDF without plate (Groups S = standalone) and outcomes were compared.

RESULTS

There were 260 patients with 138 (53%) in Group P and 122 (47%) in Group S. ALOD was observed in 15.3% of patients overall, 29% in group P and 2.8% in group S (P < .001). Following multivariate adjustment, statistically significant association was found between use of plate and ALOD (odds ratio = 12.8, 95% confidence interval = 3.52-45.45, P < .001). Plate-to-disc distance <5 mm was significantly associated with ALOD (odds ratio = 13.5, 95% confidence interval = 3.83-47.62, P < .001).

CONCLUSION

The use of anterior plate with ACDF was associated with ALOD. Plate-to-disc distance <5 mm was significantly associated with ALOD even after adjustment for confounding factors. We conclude utilization of standalone cages or cages with plate with more than 5 mm distance from adjacent disc to minimize ALOD.

Unintended fusion in cervical artificial disk replacement: a prospective study on heterotopic ossification, progression, and clinical outcome, with 5-year follow-up

PURPOSE

Heterotopic ossification (HO) may cause unintended fusion in artificial disk replacement (ADR), failing to preserve motion. The reported incidence of HO varies hugely. This study aimed to determine prevalence of HO, progression, predisposing factors to occurrence and to progression, and potential effect on clinical outcomes.

METHODS

Eighty-three patients treated with ADRs for cervical radiculopathy at one or two segments were extracted from a previously published RCT. Of the 83 patients, 59 had remaining ADR (79 implants) and sufficiently high-quality X-rays at 5 years of follow-up to allow analysis. HO was graded on plain films according to Mehren/Suchomel. Prevalence, progression, predisposing factors and effect on clinical outcome (Neck Disability Index-NDI) were analyzed.

RESULTS

At 2 years, HO was seen in 46/55 ADR implants (84%), severe enough to affect mobility in 27/55 (49%). At 5 years, HO was seen in 92% of 79 implants, severe in 71%. Male sex was a predisposing factor to HO. No predisposing factors to progression were identified. NDI was not affected by the severity of HO.

CONCLUSION

Almost all ADR implants in our study have HO at 5 years of follow-up. Male sex is a risk factor. Severe HO did not affect clinical outcome.

TRIAL REGISTRATION

Study registered at ISRCTN (registration number: 44347115).

The Assessment of Paravertebral Ossification Progression After Cervical Disc Arthroplasty Based on CT Images: A Long-term Follow-up

Objective

This study focused on the assessment of paravertebral ossification (PO) after cervical disc arthroplasty (CDA) using computed tomography (CT) images.

Methods

In this retrospective study, 52 patients (from 2004 to 2010) who received CDA at a single center were included (32 males). Preoperative and follow‐up X‐ray and CT images of all patients who underwent single‐level CDA were collected. PO from the C2/3 to C7/T1 in each patient was graded based on a CT grading system. Each segment was divided into operative level, adjacent level, or non‐adjacent level. The McAfee' classification system was used to grade PO using X‐ray plain film. The range of motion (ROM) and scores of neurological symptoms (Japanese Orthopaedic Association [JOA] score and Neck Disability Index [NDI]) at both preoperative and final follow‐up time were acquired. Progression and classification of PO in each group was compared using the chi‐square test. ROM between groups were compared using independent t‐test. JOA score and NDI between groups were compared using Mann–Whitney U test.

Results

The average follow‐up time was 81.2 months. In comparison with the preoperative status, the progression of PO development in left and right areas (the Luschka joints areas) in the operative level groups was significantly more severe (area L,χ² value = 36.612, P < 0.001; area R, χ² value = 39.172, P < 0.001) than the non‐adjacent level groups. In contrast, although the prevalence of PO in all areas of the adjacent level groups was higher than that of the non‐adjacent level group in the same segments, there was no significant difference (P > 0.05) in the progression of PO development. The follow‐up high‐grade (grades III and IV) PO incidence rate using X‐ray grading system (3.85%) was significantly lower than that using CT grading system in area L (42.31%) and R (38.46%), but close to that in area A (5.77%) and P (1.92%). The final follow‐up ROM was not significantly different with preoperative ROM in patients with low‐grade PO (9.47° ± 4.12° vs. 9.76° ± 3.69°, P = 0.794). However, in patients with high‐grade PO, the final follow‐up ROM was significantly lower than preoperative ROM (5.77° ± 3.32° vs. 9.28° ± 4.15°, P < 0.001). There was no significant difference for JOA score and NDI at follow‐up between patients with high‐grade and low‐grade PO (JOA, 16.2 ± 1.1 vs. 16.8 ± 0.9, P = 0.489; NDI, 8.9 ± 6.1 vs. 8.0 ± 7.3, P = 0.317).

Conclusion

High‐grade PO was observed in the areas of the Luschka joints at the operative level after CDA, which was difficult to observe using X‐ray plain film. The PO formation at adjacent segments was not significant.

Comparing Heterotopic Ossification in Two Cervical Disc Prostheses

STUDY DESIGN

Retrospective analysis using data from randomized clinical trials.

OBJECTIVE

To compare the occurrence of heterotopic ossification (HO) between two cervical disc prostheses. Clinical outcome and range of motion (ROM) were also evaluated.

SUMMARY OF BACKGROUND DATA

Cervical arthroplasty was reported to be able to maintain the segmental ROM. However, controversy exists since the difference of the occurrence of HO concerning cervical prosthesis is still huge.

METHODS

Patients who underwent anterior cervical discectomy with arthroplasty for a cervical radiculopathy due to a herniated disc from the The Netherlands Cervical Kinematics (NECK) trial (activC; metal endplates with a polyethylene inlay and a keel for primary stability) and the PROCON trial (Bryan; metal-on-polymer with titanium coated endplates without a keel) were analyzed for HO at 12 and 24 months postoperatively. HO was scored according to the McAfee-Mehren classification. Segmental ROM was defined by a custom developed image analysis tool, and global cervical ROM was measured by Cobb's angle. Clinical outcome was evaluated by means of the neck disability index (NDI) as well as physical-component summary (PCS) and mental-component summary (MCS).

RESULTS

At 2-year follow-up, the occurrence of HO was 68% in patients treated with the activC prosthesis (severe HO 55%), which was comparable with 85% (P = 0.12) in patients with the Bryan disc (severe HO 44%; P = 0.43). The HO progression was similar between groups. Clinically, the patients had comparable NDI, PCS, and MCS at 2-year follow-up, and comparable improvement of clinical outcomes. The global ROM in the Bryan group (56.4 ± 10.8°) was significantly higher than in the activC group (49.5 ± 14.0, P = 0.044) at 2-year follow-up.

CONCLUSION

In comparison of two cervical disc prostheses the development of HO is independent on their architecture. Although global ROM was higher in the Bryan prosthesis group, this difference was not deemed clinically important, particularly because the clinical condition of patients with and without severe HO was comparable.

LEVEL OF EVIDENCE

2.

Prevalence of and Risk Factors for Heterotopic Ossification After Cervical Total Disc Replacement: A Systematic Review and Meta-Analysis

STUDY DESIGN

A systematic review and meta-analysis.

OBJECTIVES

The results from previous meta-analyses are limited by the small number of included studies. Moreover, the risk factors of heterotopic ossification (HO) have not been well studied. Therefore, this study aims to estimate the prevalence of HO after cervical total disc replacement (CTDR) at different follow-up time points and explore potential risk factors for HO.

METHODS

We searched databases to identify eligible studies that reported the rate of HO after CTDR. The pooled prevalence of HO, according to different grades of HO, length of follow-up and types of prosthesis, and 95% confidence intervals (CIs) were calculated. Multivariable meta-regression analyses were performed to identify factors that may contribute to the heterogeneity between estimates.

RESULTS

Of the 94 studies included, 82 studies reported an overall rate of HO, encompassing a total of 5861 cervical spinal levels that underwent CTDR. The overall pooled prevalence of HO was 32.5% (95% CI 26.7% to 38.4%). Single-level CTDR was associated with a higher overall rate of HO. When the rate of HO was stratified by McAfee/Mehren classification, the pooled prevalence of range of motion (ROM)-limiting HO was 11.0% (95% CI 9.2% to 12.8%). Latest publication, single-level CTDR, longer follow-up period, and studies published outside were associated with a higher rate of ROM-limiting HO.

CONCLUSIONS

We provide a comprehensive overview of the prevalence of different grades of HO. This meta-analysis also identifies and rules out some risk factors for HO after CTDR.

Quantitative analysis of the correlation between preoperative cervical degeneration and postoperative heterotopic ossification after cervical disc replacement: minimum 10-year follow-up data

OBJECTIVE

The authors aimed to identify factors that may be useful for quantifying the amount of degenerative change in preoperative patients to identify ideal candidates for cervical disc replacement (CDR) in patients with a minimum of 10 years of follow-up data.

METHODS

During the period from December 2003 to August 2008, 54 patients underwent CDR with a Bryan cervical disc prosthesis performed by the same group of surgeons, and all of the patients in this group with at least 10 years of follow-up data were enrolled in this retrospective analysis of cases. Postoperative bone formation was graded in radiographic images by using the McAfee classification for heterotopic ossification. Preoperative degeneration was evaluated in radiographs based on a quantitative scoring system. After univariate analysis, the authors performed multifactor logistic regression analysis to identify significant factors. To determine the cutoff points for the significant factors, a receiver operating characteristic (ROC) curve analysis was conducted.

RESULTS

Study patients had a mean age of 43.6 years and an average follow-up period of 120.3 months. The patients as a group had a 68.2% overall incidence of bone formation. Based on univariate analysis results, data for patient sex, disc height, and the presence of anterior osteophytes and endplate sclerosis were included in the multivariate analysis. According to the analysis results, the identified independent risk factors for postoperative bone formation included disc height, the presence of anterior osteophytes, and endplate sclerosis, and according to a quantitative scoring system for degeneration of the cervical spine based on these variables, the ROC curve indicated that the optimal cutoff scores for these risk factors were 0.5, 1.5, and 1.5, respectively.

CONCLUSIONS

Among the patients who were followed up for at least 10 years after CDR, the incidence of postoperative bone formation was relatively high. The study results indicate that the degree of degeneration in the target level before surgery has a positive correlation with the incidence of postoperative ossification. Rigorous indication criteria for postoperative ossification should be applied in patients for whom CDR may be a treatment option.

The Survey of Cells Responsible for Heterotopic Ossification Development in Skeletal Muscles-Human and Mouse Models

Heterotopic ossification (HO) manifests as bone development in the skeletal muscles and surrounding soft tissues. It can be caused by injury, surgery, or may have a genetic background. In each case, its development might differ, and depending on the age, sex, and patient's conditions, it could lead to a more or a less severe outcome. In the case of the injury or surgery provoked ossification development, it could be, to some extent, prevented by treatments. As far as genetic disorders are concerned, such prevention approaches are highly limited. Many lines of evidence point to the inflammatory process and abnormalities in the bone morphogenetic factor signaling pathway as the molecular and cellular backgrounds for HO development. However, the clear targets allowing the design of treatments preventing or lowering HO have not been identified yet. In this review, we summarize current knowledge on HO types, its symptoms, and possible ways of prevention and treatment. We also describe the molecules and cells in which abnormal function could lead to HO development. We emphasize the studies involving animal models of HO as being of great importance for understanding and future designing of the tools to counteract this pathology.

Multilevel cervical arthroplasty-clinical and radiological outcomes

BACKGROUND

Cervical disc arthroplasty (CDA) is a valid option for single-level cervical disc disease (CDD) as an alternative to fusion. However, the use in 3- and 4-level disc disease is under scrutiny with scarce data published so far. Our aim was to study clinical and radiological outcomes of arthroplasty in patients with multilevel CDD.

METHODS

Retrospective analysis of clinical records, pre- and post-operative neutral/dynamic X-rays of patients who underwent CDA in multilevel CDD (2-4 levels). We evaluated sagittal balance parameters (C2-7 and index angle, SVA), global and segmental range of motion (ROM)), neck and arm VAS, Odom's criteria, re-operation rate, adjacent segment disease (ASD), willingness to undertake the same procedure again. Rate of heterotopic ossification (HO) was studied for follow-up >2 years. A subgroup analysis was performed regarding 2-level versus 3- or 4-level arthroplasty.

RESULTS

Thirty-two patients were included, 6 males and 26 females, mean age of 46 years (range, 30-63). Seventy-seven cervical disc levels were treated with the same artificial disc. Twenty-one patients were operated on 2 levels, nine in 3 levels, and 2 patients in 4 levels. Post-operatively, there was a decrease in SVA (-2.2±8.36 mm, P=0.098) and an increase in global (3.7±9.6º, P=0.042) and index (1.3±6.1º, P=0.071) ROM. Mean nVAS and aVAS decreased (7.5±1.1 to 2.5±1.5; 6.3±1.9 to 2.2±1.7, P<0.05). Two-level versus 3-4 level patient subgroups showed a lower SVA (-1.3±8.1 mm P=0.47; -3.4±6.3 mm P=0.107), a slight increase in global (1.6±9.4º P=0.44; 7.2±11.7º P=0.07) and index (1.1±4.7º P=0.12; 1.3±8.1º P=0.35) ROM. HO was present in 9.9% (7/71) of disc levels operated, none of them with grade 3 or 4.

CONCLUSIONS

Multilevel CDA provides good clinical and radiological outcomes, preserving global and segmental cervical mobility, while having a beneficial effect on sagittal balance. These results hold for 2 to 4 levels, making this technique a valuable option in selected patients with cervical multilevel CDD.

Is Anterior Bone Loss the Opposite of Anterior Heterotopic Ossification in Prestige-LP Cervical Disc Replacement?

BACKGROUND

Heterotopic ossification (HO) and anterior bone loss (ABL) are 2 complications in cervical disc replacement (CDR), which have impacts on the clinical outcomes. Physiologically, bone formation (HO) and bone loss are 2 sides of bone remodeling. However, clinically, some patients experienced anterior HO (AHO) after CDR, whereas other patients experienced ABL. Is there any factor in determining the fate of the vertebral bone in the anterior region? Is ABL the opposite of AHO? This study aims to answer these questions.

METHODS

Seventy patients with 1-level Prestige-LP CDR were retrospectively reviewed and were divided into an AHO group or ABL group. Radiologic outcomes, including cervical lordosis, sagittal vertical axis, functional spine unit angle, disc angle, range of motion, implant migration, subsidence, and adjacent segment degeneration were evaluated. Patient-reported clinical outcomes were also evaluated.

RESULTS

AHO group showed significantly lower disc angle after surgery (0.9° ± 4.2°), compared with ABL group (6.7° ± 4.7°) (P < 0.001). The preoperative segmental range of motion was significantly higher in the AHO group (10.2° ± 3.3°) than in the ABL group (8.2° ± 3.7°) (P = 0.042). No correlation was observed between clinical outcomes and the presence of anterior bone remodeling. Both groups maintained cervical alignment and functional spine unit angle during long-term follow-up. No significant difference was found in the end plate preparation, implant subsidence, migration, or adjacent segment degeneration rate between the 2 groups.

CONCLUSIONS

The differences in the disc angle showed the role of mechanical load in the anterior bone remodeling. Combined the results with the basic concepts of bone remodeling, ABL may be the opposite of AHO.

Effect of Prosthesis Width and Depth on Heterotopic Ossification After Cervical Disc Arthroplasty

STUDY DESIGN

Retrospective analysis.

OBJECTIVE

To investigate the effect of width and depth of the inserted cervical disc prosthesis on heterotopic ossification (HO) after cervical disc arthroplasty, and to explore the relationship between clinical outcome and HO.

SUMMARY OF BACKGROUND DATA

The mechanism of HO formation still remains unknown. Footprint mismatch of cervical disc prosthesis was common in cervical arthroplasty. Compared with endplate, some inserted prostheses were smaller in width and length.

METHODS

Retrospectively analyze the patients who underwent cervical disc arthroplasty with Prestige-LP Disc in our institute. Patients were divided into HO group or non-HO group according to the McAfee classification. The ratios of the width (Rw) and depth (Rd) of prosthesis to endplate were calculated. Radiographic and clinical assessments included: C2-7 angle, segmental angle, range of motion (ROM) of the index level, visual analogue scale, neck disability index, and Japanese orthopaedic association scores.

RESULTS

The mean follow-up time was 47.7 months. At the last follow-up, the overall incidence of HO was 34.3% (35/102). There were 35 patients in the HO-group, and 67 patients in the non-HO group. The overall Rw and Rd were 0.887 ± 0.057 and 0.927 ± 0.048, respectively. Both the Rw and Rd of HO-group were smaller than those of non-HO group (0.869 vs. 0.897, P = 0.033; 0.888 vs. 0.948, P < 0.001). There were no significant differences in visual analogue scale, neck disability index, or Japanese orthopaedic association scores, C2-7 angle, or segmental angle between the two groups. But the HO group had less ROM of the index level than the non-HO group (5.3° vs. 9.0°).

CONCLUSION

Some of prosthesis had insufficient coverage to the endplate in width and depth. Insufficient coverage of endplate in width and depth may induce the formation of HO. HO could reduce the ROM of the index level, but did not influence the clinical outcome.

LEVEL OF EVIDENCE

3.

Adverse Events Following Cervical Disc Arthroplasty: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Are Controversial Issues in Cervical Total Disc Replacement Resolved or Unresolved?: A Review of Literature and Recent Updates

Since the launch of cervical total disc replacement (CTDR) in the early 2000s, many clinical studies have reported better outcomes of CTDR compared to those of anterior cervical discectomy and fusion. However, CTDR is still a new and innovative procedure with limited indications for clinical application in spinal surgery, particularly, for young patients presenting with soft disc herniation with radiculopathy and/or myelopathy. In addition, some controversial issues related to the assessment of clinical outcomes of CTDR remain unresolved. These issues, including surgical outcomes, adjacent segment degeneration (ASD), heterotopic ossification (HO), wear debris and tissue reaction, and multilevel total disc replacement (TDR) and hybrid surgeries are a common concern of spine surgeons and need to be resolved. Among them, the effect of CTDR on patient outcomes and ASD is theoretically and clinically important; however, this issue remains disputable. Additionally, HO, wear debris, multilevel TDR, and hybrid surgery tend to favor CTDR in terms of their effects on outcomes, but the potential of these factors for jeopardizing patients' safety postoperatively and/or to exert harmful effects on surgical outcomes in longer-term follow-up cannot be ignored. Consequently, it is too early to determine the therapeutic efficacy and cost-effectiveness of CTDR and will require considerable time and studies to provide appropriate answers regarding the same. For these reasons, CTDR requires longer-term follow-up data.

The Norwegian Cervical Arthroplasty Trial (NORCAT): 2-year clinical outcome after single-level cervical arthroplasty versus fusion-a prospective, single-blinded, randomized, controlled multicenter study

PURPOSE

Standard surgical treatment for symptomatic cervical disc disease has been discectomy and fusion, but the use of arthroplasty, designed to preserve motion, has increased, and most studies report clinical outcome in its favor. Few of these trials, however, blinded the patients. We, therefore, conducted the Norwegian Cervical Arthroplasty Trial, and present 2-year clinical outcome after arthroplasty or fusion.

METHODS

This multicenter trial included 136 patients with single-level cervical disc disease. The patients were randomized to arthroplasty or fusion, and blinded to the treatment modality. The surgical team was blinded to randomization until nerve root decompression was completed. Primary outcome was the self-rated Neck Disability Index. Secondary outcomes were the numeric rating scale for pain and quality of life questionnaires Short Form-36 and EuroQol-5Dimension-3 Level.

RESULTS

There was a significant improvement in the primary and all secondary outcomes from baseline to 2-year follow-up for both arthroplasty and fusion (P < 0.001), and no observed significant between-group differences at any follow-up times. However, linear mixed model analyses, correcting for baseline values, dropouts and missing data, revealed a difference in Neck Disability Index (P = 0.049), and arm pain (P = 0.027) in favor of fusion at 2 years. The duration of surgery was longer (P < 0.001), and the frequency of reoperations higher (P = 0.029) with arthroplasty.

CONCLUSION

The present study showed excellent clinical results and no significant difference between treatments at any scheduled follow-up. However, the rate of index level reoperations was higher and the duration of surgery longer with arthroplasty.

TRIAL REGISTRATION

http://www.clinicaltrials.gov NCT 00735176.19.