Differences between soft-disc herniation and spondylosis in cervical arthroplasty: CT-documented heterotopic ossification with minimum 2 years of follow-up

The Impact of Endplate Coverage on Heterotopic Ossification Following Cervical Disc Replacement: A Systematic Review and Meta Analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

Describe the impact of endplate coverage on HO in cervical disc replacement (CDR).

SUMMARY OF BACKGROUND DATA

CDR is a motion-sparing alternative to anterior cervical discectomy and fusion. However, the high prevalence of heterotopic ossification threatens to diminish range of motion and limit this benefit associated with CDR.

MATERIALS AND METHODS

A systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. EMBASE and PubMed databases were queried. Results were deduplicated and screened. Relevant studies were included. All metrics that were reported in ≥3 studies were aggregated for analysis. SPSS was used to perform the meta-analysis.

RESULTS

A total of 10 studies were included in the systematic review. Endplate coverage was assessed using a wide variety of measurements, including anteroposterior implant depth (ID), endplate depth (ED), exposed endplate depth (EED), implant depth to endplate depth ratio (ID:ED), EED to ED ratio (EED:ED), implant width (IW) to endplate width (EW) ratio (IW:EW), and the implant area (IA) to endplate area (EA) ratio (IA:EA). No evidence has linked ID (three studies) to HO. Mixed evidence has linked ID:ED (3/5) and IW:ED (1/2) to HO. All available evidence has linked ED (2), EED (4), EED:ED (2), and IA:EA (1) to HO. In our meta-analysis, ID was not found to be a significant risk factor for HO. However, EED and ID:ED were found to be significant risk factors for HO formation.

CONCLUSIONS

Exposed endplate, especially as assessed by EED and ID:ED, is a significant risk factor for HO. Surgeons should focus on preoperative planning and intraoperative implant selection to maximize endplate coverage. While optimizing technique and implant selection is crucial, improved implant design may also be necessary to ensure that appropriate implant-endplate footprint matching is possible across the anatomic spectrum.

The Effect of Preoperative Cervical Spondylosis on Heterotopic Ossification After Cervical Disc Replacement

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

This study aimed to explore the effect of preoperative cervical spondylosis on the heterotopic ossification (HO) formation in different locations after cervical disc replacement (CDR).

METHODS

The degree of preoperative cervical spondylosis was evaluated radiologically, including the intervertebral disc, uncovertebral joints, facet joints and ligaments. The effects of cervical spondylosis on the HO formation after CDR were analyzed according to the location of HO. Multivariate logistic regression was performed to identify the independent factors.

RESULTS

149 patients with a total of 196 arthroplasty segments were involved in this study. HO, anterior HO (AHO), and posterior HO (PHO) developed in 59.69%, 22.96%, and 41.84% levels, respectively. The significant factors in univariate analysis for PHO after CDR included the disc height loss, anterior osteophytes, preoperative uncovertebral joint osteophytes and facet joint degeneration. The incidence of adjacent segment degeneration (ASD) was significantly higher in the PHO group compared to that without PHO at the last follow-up (P = .003). The disc height loss in high-grade HO was significantly more than that in low-grade group (P = .039). Multivariate analysis identified disc height loss was the only independent factor for PHO (P = .009). No significant degenerative factors related to the formation of AHO were found.

CONCLUSIONS

Preoperative cervical spondylosis predominantly affected the HO formation in the posterior disc space after CDR. The disc height loss was an independent risk factor for PHO formation. Rigorous criteria for the extent of preoperative disc height loss should be used when selecting appropriate candidates for CDR.

Incidence and Risk Factor of Implant Dislocation After Cervical Disk Arthroplasty: A Retrospective Cohort Analysis of 756 Patients

BACKGROUND

Implant dislocation after cervical disk arthroplasty (CDA) is obviously a critical complication, but no information about the incidence and associated risk factor has been reported.

OBJECTIVE

To investigate the incidence and risk factor of implant dislocation after CDA by a retrospective cohort analysis.

METHODS

A retrospective review of a consecutive series of CDA performed between January 2009 and March 2021 at a single institution was conducted. Analyses of chart records and radiological data established the incidence and associated risk factor of implant dislocation after CDA. A Kaplan-Meier survival estimation of implant survival was performed.

RESULTS

A total of 756 consecutive patients were included in this analysis. Five patients (0.7%) had a migration and even dropout of the artificial disk. The overall cumulative survival rate of the implant reached approximately 99.3% of the 756 patients. Preoperative kyphosis was significantly related to implant dislocation ( P = .016), with an odds ratio of 15.013.

CONCLUSION

The incidence of implant dislocation after CDA is as low as 0.7% or 5/756 patients. Preoperative kyphosis significantly increases the risk of postoperative implant dislocation by a factor of 15. The migrating implants could be revealed on radiographs as early as 0.9 to 1.4 months postoperatively and were revised to anterior cervical diskectomy and fusion within half a year. No new event of implant dislocation occurred half a year postoperatively. The overall cumulative survival rate of the implant reached 99.3% of the 756 patients. In conclusion, CDA remains a safe and reliable procedure.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Anterior Cervical Discectomy and Fusion Versus Cervical Disc Replacement in Patients With Significant Cervical Spondylosis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim was to compare clinical outcomes in patients with significant cervical spondylosis treated with cervical disc replacement (CDR) compared with anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

As CDR utilization has increased over the past decade, recent studies have investigated the outcomes of CDR in patients with more significant spondylotic changes and demonstrated improved postoperative patient-reported outcomes (PROs). However, no prior study has investigated clinical outcomes of patients with significant spondylotic changes treated with CDR in comparison to ACDF.

METHODS

Patients who underwent 1-level or 2-level CDR or ACDF with significant cervical spondylosis, quantified using a validated grading scale, were identified, and prospectively collected data was retrospectively reviewed. The following PROs were analyzed: Neck Disability Index (NDI), visual analog scale-Neck, visual analog scale-Arm, and PROMIS Physical Function (PROMIS-PF) Computer Adaptive Test Score. Demographic, operative, and radiographic variables, and achievement of minimum clinically important difference (MCID) for each PRO were compared between the 2 groups.

RESULTS

A total of 66 patients were included in the present study, of which 35 (53%) were treated with CDR and 31 (47%) with ACDF. The preoperative cervical spondylotic grade was similar between the 2 groups (1.8 vs. 2.2, P=0.27). At final follow-up, there was no significant difference in the absolute value for each PRO between the 2 groups (P>0.19) and both groups demonstrated significant improvement in each PRO compared with preoperative values (P<0.01). There was no significant difference in the percentage of patients achieving the MCID for each PRO when comparing CDR to ACDF (P>0.09).

CONCLUSIONS

A similar percentage of patients with significant degenerative cervical spondylosis achieved the MCID across multiple PROs when treated with CDR or ACDF. Patients in both treatment groups demonstrated significant improvement in all PROs assessed when compared with preoperative values.

LEVEL OF EVIDENCE

Level III.

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.

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

BACKGROUND

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

OBSERVATIONS

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

LESSONS

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

Risk Factors for High-Grade Heterotopic Ossification After Total Disc Replacement: A Single-Center Experience of 394 Cases

BACKGROUND

Heterotopic ossification (HO) is a common complication following total disc replacement (TDR). High-grade HO is a clinically relevant complication, however, only a few studies have evaluated risk factors for high-grade HO.

OBJECTIVE

To evaluate potential risk factors for HO and high-grade HO and their impact on clinical outcomes.

METHODS

We retrospectively reviewed patients who underwent TDR or hybrid surgery (HS) with Prestige-LP (Medtronic), Discover (Depuy), and Prodisc-C (Synthes). Clinical outcomes were assessed using Japanese Orthopaedic Association, Visual Analogue Scale, and Neck Disability Index scores. Radiological variables, including preoperative ossification, global and segmental range of motion (ROM), HO, and adjacent segment degeneration (ASD) were reviewed.

RESULTS

A total of 394 patients were evaluated. HO and high-grade HO occurred in 67.77% and 11.17% patients, respectively. Preoperative ossification was significantly associated with the occurrence of HO (P < .001, OR: 3.507, 95%CI: 2.211-5.562) and high-grade HO (P = .019, OR: 2.176, 95%CI: 1.137-4.166). The ROM of replacement levels and C2-7 were significantly lower in the high-grade HO group compared to those without high-grade HO: (3.80° vs 10.18°, P < .001) and (42.81° vs 54.00°, P < .001), respectively. The incidence of ASD was significantly higher in patients with high-grade HO than those without high-grade HO (22.73% vs 11.14%, P = .048).

CONCLUSION

Preoperative ossification was identified as a potential risk factor for HO and high-grade HO. Patients with high-grade HO had limited ROM of replacement levels and the cervical spine and had a high incidence of ASD compared to those without high-grade HO.

Cervical disc arthroplasty at C2–3: illustrative case

BACKGROUND

Since the beginning of the 21st century, cervical disc arthroplasty (CDA) has been accepted as an alternative to anterior cervical discectomy and fusion for surgical management of disc problems. The published clinical trials of CDA have included patients with radiculopathy or myelopathy caused by one- or two-level disc herniation at C3–7. However, it remains uncertain whether CDA is a viable option for C2–3 disc herniation.

OBSERVATIONS

In this report, a 52-year-old man presented with hand numbness, arm pain, and myelopathic symptoms that were refractory to medical treatment for more than 6 months. The magnetic resonance images demonstrated herniated discs at C2–3, C3–4, and C4–5, causing stenosis. There was no ossification of posterior longitudinal ligament and the spine was mobile, so he received anterior discectomies with artificial disc replacement at each of the C2–3, C3–4, and C4–5 levels. The surgery went smoothly, and his neurological symptoms were promptly relieved. The postoperative radiographs at 24 months demonstrated a preserved range of motion at each level.

LESSONS

To date, this was the first report of CDA performed at C2–3, which also involved three consecutive levels of disc replacement. The report suggested that both C2–3 and three-consecutive-level CDA may be a viable option for cervical disc disease.

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 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.

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.

Effect of preoperative segmental range of motion on patient outcomes in cervical disc arthroplasty

Background

Cervical disc arthroplasty (CDA) has been demonstrated, in clinical trials, as an effective and safe treatment for patients diagnosed with radiculopathy and/or myelopathy. However, the current CDA indication criteria, based on the preoperative segmental range of motion (ROM), comprises a wide range of variability. Although the arthroplasty level preserved ROM averages 7°-9° after CDA, there are no clear guidelines on preoperatively limited or excessive ROM at the index level, which could be considered as suitable for CDA.

Methods

This was a retrospective study of patients who underwent CDA between January 2008 and October 2018 using Prestige-LP discs in our hospital. They were divided into the small-ROM (≤5.5°) and the large-ROM (> 12.5°) groups according to preoperatively index-level ROM. Clinical outcomes, including the Japanese Orthopedics Association (JOA), Neck Disability Index (NDI), and Visual Analogue Scale (VAS) scores, were evaluated. Radiological parameters, including cervical lordosis, disc angle (DA), global and segmental ROM, disc height (DH), and complications were measured.

Results

One hundred and twenty six patients, with a total of 132 arthroplasty segments were analyzed. There were 64 patients in the small-ROM and 62 in the large-ROM group. There were more patients diagnosed with cervical spondylosis in the small-ROM than in the large-ROM group (P = 0.046). Patients in both groups had significantly improved JOA, NDI, and VAS scores after surgery, but the intergroup difference was not significant. Patients in the small-ROM group had dramatic postoperative increase in cervical lordosis, global and segmental ROM (P < 0.001). However, there was a paradoxical postoperative decrease in global and segmental ROM in the large-ROM group postoperatively (P < 0.001). Patients in the small-ROM group had lower preoperative DH (P = 0.012), and a higher rate of postoperative heterotopic ossification (HO) (P = 0.037).

Conclusion

Patients with preoperatively limited segmental ROM had severe HO, and achieved similar postoperative clinical outcomes as patients with preoperatively excessive segmental ROM. Patients with preoperatively limited segmental ROM showed a postoperative increase in segmental mobility, which decreased in patients with preoperatively excessive segmental ROM.

Single-level Bryan cervical disc arthroplasty: evaluation of radiological and clinical outcomes after 18 years of follow-up

PURPOSE

Many studies reported mid-term clinical and radiological outcomes after cervical disc arthroplasty. Only a few studies analysed the long-term results. The aim of the study was to evaluate the clinical and radiological outcomes in patients treated with single-level Bryan cervical disc arthroplasty after 18 years of follow-up.

METHODS

This study was a retrospective analysis of institutional databases concerning patients treated with Bryan cervical disc arthroplasty. SF36 PCS, NDI and VAS were used to evaluate clinical and functional outcomes. Standard, flexion-extension X-ray and MRI were used to evaluate the radiological results.

RESULTS

Fifty-seven patients treated with single-level Bryan cervical disc arthroplasty completed the 18-year follow-up. At the final follow-up, a residual movement was observed in 32 patients (56%). The treated level range of motion decreased from 10.1° pre-operatively to 6.1° at the last follow-up (p = 0.0021). The range of motion of the adjacent segments and of the cervical spine had no significant change. Disc degeneration of the adjacent segment after 18-year follow-up was observed in 77.1% of treated patients.

CONCLUSION

The clinical and radiographic outcomes 18 years after surgery are acceptable. The treated level range of motion reduction and the adjacent segment degeneration seems not to affect the clinical results after 18 years of follow-up.

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.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Cervical disc arthroplasty for less-mobile discs

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

Background

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

Methods

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

Results

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

Conclusions

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

Early Discharge for Anterior Cervical Fusion Surgery: Prediction of Readmission and Special Considerations for Older Adults

Anterior cervical discectomy and fusion (ACDF) is the standard surgical management for disc herniation and spondylosis worldwide and reportedly performed with short hospitalization and early discharge (ED). However, it is unknown if ED improves the outcomes of ACDF including among older adults. This cohort study included patients who underwent ACDF surgery in Taiwan over two years analyzed in two groups: the ED group (discharged within 48 hours), and the comparison group (hospitalized for more than 48 h). Both groups were followed-up for at least 180 days. Pre- and post-operative comorbidities, re-admissions and re-operations were analyzed using a multivariate cox-regression model, with bootstrapping, and Kaplan–Meier analysis. Among 5565 ACDF patients, the ED group (n = 405) had a higher chance (crude and adjusted hazard ratio = 2.33 and 2.39, both p < 0.001) of re-admission than the comparison group (n = 5160). The ED group had an insignificant trend toward more re-admissions for spinal problems and re-operations within 180 days. In the ED group, older age (≥60) and hypertension were predictive of re-admission. For ACDF surgery, the ED group had higher rates of re-admission within 180 days of post-op, suggesting that the current approach to ED requires modification or more cautious selection criteria be adopted, particularly for older adults.

Postoperative Heterotopic Ossification After Cervical Disc Replacement Is Likely a Reflection of the Degeneration Process

BACKGROUND

The cause of postoperative heterotopic ossification (HO) after cervical disc replacement (CDR) is unclear. The aim of the present study was to investigate the incidence of HO, its clinical significance, and whether the degree of preoperative degeneration was associated with its occurrence.

METHODS

Patients who had undergone CDR using the Prestige-LP disc with a minimum of 48 months of follow-up were included. The patients were divided into 2 groups stratified by the presence of HO. The clinical outcomes (visual analog scale for neck and arm pain, neck disability index, and Japanese Orthopaedic Association scores) and radiographic parameters were collected and analyzed pre- and postoperatively and compared between the 2 groups. The preoperative degeneration at the operated levels was evaluated using the Kellgren-Lawrence scale and Miyazaki magnetic resonance imaging grading system.

RESULTS

A total of 69 patients (89 levels) were identified, and the average age at surgery was 45.8 years. The overall incidence of HO at the final follow-up visit was 37.7% (26 of 69 of patients), and an increasing incidence and severity of HO was observed during the follow-up period. Significant and maintained improvements for all clinical outcome measures were observed, and the presence of HO did not influence these improvements. Segments with greater severe preoperative degeneration had a greater incidence of HO (P < 0.01). However, no statistical significant correlation between the degree of preoperative degeneration and the grade of HO was observed.

CONCLUSION

The presence of HO after CDR was a relatively frequent finding at the final follow-up visit but did not influence patients' improvements. Segments with higher grades of preoperative degeneration had a greater incidence of HO; thus, HO is likely a reflection of the degeneration process.

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

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

Heterotopic Ossification After Cervical Total Disc Replacement at 7 Years-Prevalence, Progression, Clinical Implications, and Risk Factors

Background

Heterotopic ossification (HO) is a known risk following cervical total disc replacement (CTDR) surgery, but the cause and effect of HO are not well understood. Reported HO rates vary, and few studies are specifically designed to report HO. The effects on outcomes, and the risk factors for the development of HO have been hypothesized and reported in small-population, retrospective analyses, using univariate statistics.

Methods

Posthoc, multiple-phase analysis of radiographic, clinical, and demographic data for CTDR as it relates to HO was performed. HO was radiographically graded for 164 one-level and 225 two-level CTDR patients using the McAfee and Mehren system. Analysis was performed to correlate HO grades to clinical outcomes and to evaluate potential risk factors for the development of HO using demographics and baseline clinical measures.

Results

At 7 years, 1-level clinically relevant HO grades were 17.6% grade 3 and 11.1% grade 4. Two-level clinically relevant HO grades, evaluated using the highest patient grade, were 26.6% grade 3 and 10.8% grade 4. Interaction between HO and time revealed significance for neck disability index (NDI; P = .04) and Visual Analog Scale (VAS) neck pain (P = .02). When analyzed at each time point NDI was significant at 48-84 months and VAS neck at 60 months. For predictors 2 analyses were run; odds ratios indicated follow-up visit, male sex, and preoperative VAS neck pain are related to HO development, whereas hazard ratios indicated male sex, obesity, endplate coverage, levels treated, and preoperative VAS neck pain.

Conclusions

This is the largest study to report HO rates, and related outcomes and risk factors. To develop an accurate predictive model, further large-scale analyses need to be performed. Based on the results reported here, clinically relevant HO should be more accurately described as motion-restricting HO until a definitive link to outcomes has been established.

Ossification of the Posterior Longitudinal Ligament in Cervical Spine: Prevalence, Management, and Prognosis

Ossification of the posterior longitudinal ligament (OPLL) in the cervical spine and related neurological complications are not uncommon in East Asian countries. The estimated prevalence of cervical OPLL-related hospitalization is 7.7 per 100,000 person-years in Taiwan, and higher incidence rates have been observed in elderly and male patients. Although cervical OPLL is frequently insidious, it can eventually cause myelopathy and predispose patients to spinal cord injury (SCI). There are multiple options for managing cervical OPLL, ranging from observation to many kinds of surgical procedures, including posterior laminoplasty, laminectomy with or without fusion, anterior corpectomy with or without instrumentation, and circumferential decompression and fusion. None of these surgical approaches is free of complications. However, to date, there is still a lack of consensus regarding the choice of the surgical approach and the timing of surgical intervention. Cervical SCI and related neurological disabilities are more likely to occur in OPLL patients, who should therefore be cautioned regarding the possibility of a subsequent SCI if treated without surgery. This article aimed to review the prevalence, management strategies, and prognosis of cervical OPLL.

Progressive Bone Formation After Cervical Disc Replacement: Minimum of 5-Year Follow-up

STUDY DESIGN

Retrospective review.

OBJECTIVE

Our objective was to examine the prevalence, clinical significance, ramifications, and possible etiology of postoperative bone formation at the index level after cervical disc replacement (CDR) with a minimum of 5 years of follow-up.

SUMMARY OF BACKGROUND DATA

CDR can be complicated by postoperative ossification and unwanted ankylosis at the index level, which some authors have termed "heterotopic ossification." This terminology may be inaccurate as it assumes the postoperative bone formation is unnatural and a consequence of the CDR surgery. We advocate that this phenomenon has more to do with individual patient factors rather than the surgery.

METHODS

Patients who underwent Bryan CDR for cervical myelopathy or radiculopathy between 12/2003 and 8/2008 with a minimum of 5-years follow-up were analyzed. They were divided into two groups, those with and without postoperative bone formation. Patient-reported outcomes (Japanese Orthopaedic Association score, Neck Disability Index, Visual Analogue Scale for neck and arm pain) and radiographic parameters were collected pre- and postoperatively and compared between groups.

RESULTS

Sixty-one patients (76 levels) were identified (mean follow-up 94.2 mo). The overall incidence of postoperative ossification was 50%. Both groups had sustained significant improvements across all patient-reported outcome measures at final follow-up. Notably, patients with more severe preoperative cervical spondylosis had higher rates of postoperative ossification (P = 0.036) and adjacent segment degeneration (P = 0.010).

CONCLUSION

Although the long-term incidence of postoperative bone formation after CDR was relatively high, this did not adversely affect patient outcomes. Patients with more severe preoperative spondylosis had higher rates of postoperative ossification, suggesting that postoperative ossification at the CDR segment is likely one of progressive bone formation in individuals already predisposed to forming bone rather than one of alleged heterotopic ossification as a consequence of the surgery.

LEVEL OF EVIDENCE

3.

Generation and Development of Paravertebral Ossification in Cervical Artificial Disk Replacement: A Detailed Analytic Report Using Coronal Reconstruction CT

STUDY DESIGN

A retrospective follow-up study and review of images in published papers.

OBJECTIVE

To determine whether true heterotopic ossification (HO) occurs in artificial disk replacement (ADR); to evaluate the incidence of paravertebral ossification (PO) and its influence on ADR.

SUMMARY OF BACKGROUND DATA

HO is typically defined as the abnormal formation of true bone within extraskeletal soft tissues. However, HO in ADR does not fit this definition precisely, as it originates from vertebral body, making it hard to distinguish radiologically from preexisting osteophytes. In this study, the term used for bone formation around ADR is PO.

METHODS

First, all images in the published papers were evaluated as to whether the presented PO in ADR fit the classic definition of HO or osteophytes. Second, we studied 37 consecutive patients who underwent ADR and follow-up for minimum 24 months. The preoperative and follow-up incidence of PO and its influence on range of motion were evaluated using x-ray and computed tomography.

RESULTS

All 52 images of PO were found adjacent to the disk in 1 segment rather than entire cervical spine. Fifty (96.2%) of the POs were found to originate from the vertebral body rather than in the soft tissue. A total of 31 patients were included in the follow-up study. No significant difference was found in the incidence of PO between the follow-up and preoperation (61.29% vs. 48.39%, P>0.05). The range of motion of the ADR segment in patients with progressed PO (7.44±4.64 degrees) was significantly lower than that of patients with stable PO grade (12.13±4.42 degrees, P<0.01) at last follow-up.

CONCLUSIONS

A proportion of HO might in fact be the natural development of preoperative osteophytes, which is unrelated to ADR; the remaining HO might be due to changes in biomechanical environment after surgery, which promotes the grade of osteophytes and affects the segment motion.

An Analysis of Paravertebral Ossification in Cervical Artificial Disc Replacement: A Novel Classification Based on Computed Tomography

OBJECTIVE

Cervical artificial disc replacement (CADR) is a new technology in cervical spine surgery. However, CADR may result in paravertebral ossification (PO) after surgery and affect the mobility of the related spinal segments. The present widely used assessment method based on X-ray tomography cannot provide the position information of PO, and also PO detection rates by X-ray are low. The incidence of PO varies dramatically between studies. This study built a novel classification system based on cervical computer tomography (CT) scan to re-evaluate the incidence of PO and its influence on CADR, and also analyzed the predisposing factors of PO.

METHODS

In this retrospective study, 71 patients (from January 2004 to December 2009) who received cervical artificial disc replacement in our hospital were enrolled, and 82 cervical segments were replaced by Bryan discs. The range of motion (ROM) of the related cervical segments and scores of neurological symptoms (neck disability index [NDI] and Japanese Orthopaedic Association [JOA] scores) for both pre-surgery and last follow-up were acquired, respectively. After the establishment of a novel grading system for PO based on CT scan, we analyzed the CT images acquired before surgery and at the last time follow-up. Occurrence and distribution of PO at both time points were calculated. ROM between pre-surgery and post-surgery was compared by paired t-test stratified by PO stages. One-way ANOVA was used to compare NDI and JOA scores between high-grade and low-grade PO groups after surgery. The χ² -test was used to evaluate the risk (odds ratio) of predisposing factors in developing high-grade PO after surgery.

RESULTS

The CT-based classification system has good inter-observer and intra-observer reliability. The detection rate of PO by CT scan is higher than for traditional X-ray examination. The incidence of low-grade PO in all 82 segments at last follow-up is 32.9%. The occurrences of high-grade PO at preoperational and last follow-up time are 15.9% and 67.1%, respectively. The high-grade PO is mainly distributed around the uncovertebral joint. The pre-surgery and post-surgery ROM are similar in patients with low-grade PO at last follow-up time (9.80° ± 3.65° vs 10.03° ± 3.73°, P = 0.801); however, in patients with high-grade PO the post-surgery ROM decreases significantly compared to the pre-surgery ROM (9.73° ± 4.03° vs 6.63° ± 4.21°, P < 0.001). There is no statistical difference for JOA and NDI scores after surgery between high-grade and low-grade PO patients at final follow-up (P = 0.264, P = 0.703). The χ² -test indicates that patients with preoperational existence of PO have a high risk of high-grade PO after surgery (OR = 4, P = 0.012).

CONCLUSIONS

The novel CT image-based PO classification system has good intra-observer reliability. The incidence of PO after Bryan cervical disk replacement is relative high, and the high-grade PO is mainly distributed at the uncovertebral joint. The high-grade PO will affect the ROM after surgery; however, it does not affect the neurologic symptoms.

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°).

Differences between C3-4 and other subaxial levels of cervical disc arthroplasty: more heterotopic ossification at the 5-year follow-up

OBJECTIVE Several large-scale clinical trials demonstrate the efficacy of 1- and 2-level cervical disc arthroplasty (CDA) for degenerative disc disease (DDD) in the subaxial cervical spine, while other studies reveal that during physiological neck flexion, the C4-5 and C5-6 discs account for more motion than the C3-4 level, causing more DDD. This study aimed to compare the results of CDA at different levels. METHODS After a review of the medical records, 94 consecutive patients who underwent single-level CDA were divided into the C3-4 and non-C3-4 CDA groups (i.e., those including C4-5, C5-6, and C6-7). Clinical outcomes were measured using the visual analog scale for neck and arm pain and by the Japanese Orthopaedic Association scores. Postoperative range of motion (ROM) and heterotopic ossification (HO) were determined by radiography and CT, respectively. RESULTS Eighty-eight patients (93.6%; mean age 45.62 ± 10.91 years), including 41 (46.6%) female patients, underwent a mean follow-up of 4.90 ± 1.13 years. There were 11 patients in the C3-4 CDA group and 77 in the non-C3-4 CDA group. Both groups had significantly improved clinical outcomes at each time point after the surgery. The mean preoperative (7.75° vs 7.03°; p = 0.58) and postoperative (8.18° vs 8.45°; p = 0.59) ROMs were similar in both groups. The C3-4 CDA group had significantly greater prevalence (90.9% vs 58.44%; p = 0.02) and higher severity grades (2.27 ± 0.3 vs 0.97 ± 0.99; p = 0.0001) of HO. CONCLUSIONS Although CDA at C3-4 was infrequent, the improved clinical outcomes of CDA were similar at C3-4 to that in the other subaxial levels of the cervical spine at the approximately 5-year follow-ups. In this Asian population, who had a propensity to have ossification of the posterior longitudinal ligament, there was more HO formation in patients who received CDA at the C3-4 level than in other subaxial levels of the cervical spine. While the type of artificial discs could have confounded the issue, future studies with more patients are required to corroborate the phenomenon.

Application of Cervical Arthroplasty With Bryan Cervical Disc: 10-Year Follow-up Results in China

STUDY DESIGN

Retrospective study.

OBJECTIVE

The aims of this study were to evaluate the radiographic and clinical outcomes of Bryan cervical disc arthroplasty at 10-year follow-up.

SUMMARY OF BACKGROUND DATA

Cervical arthroplasty is a new technique for treating degenerative cervical disease. Previous reports have shown that cervical arthroplasty with Bryan disc gained good clinical outcomes at 4- to 6-year follow-up.

METHODS

Clinical outcomes and dynamic x-ray examination were evaluated at baseline and at final follow-up.

RESULTS

Thirty-three patients with complete clinical and radiographic data were included in this study. The mean follow-up period was 120.5 months (116-130 months). Twenty-five patients underwent single-level arthroplasty and 7 underwent arthroplasty at 2 levels. One patient underwent arthroplasty at 3 levels. Eight of the 33 patients presented with radiculopathy and 25 patients with myelopathy. The 42 levels of surgery included C3/4 (3 levels), C4/5 (7 levels), C5/6 (26 levels) and C6/7 (6 level). The mJOA score of the 25 patients with myelopathy was 11.8 at the baseline and 15.9 at the final follow-up. No patient suffered from adjacent segment disease. Two patients received revision surgeries at the index level for recurrent radiculopathy caused by osteophyte formation and heterotopic ossification. On x-ray examination, the range of motion at the operated level was 7.8 degree at the baseline and 4.7 degree at the final follow-up. Heterotopic ossification was observed in 29 (69.0%) levels and heterotopic ossification of Grade 4 was observed in 14 levels. Adjacent segment degeneration was observed in 30 (47.6%) levels.

CONCLUSION

Cervical arthroplasty using Bryan cervical disc prosthesis resulted in fine clinical outcomes in this study. Heterotopic ossification was common after Bryan disc arthroplasty, which decreased the range of motion.

LEVEL OF EVIDENCE

4.

Cervical Arthroplasty for Traumatic Disc Herniation: An Age- and Sex-matched Comparison with Anterior Cervical Discectomy and Fusion

BACKGROUND

The efficacy and safety of using cervical arthroplasty for degenerative disc disease have been demonstrated by prospective, randomized and controlled clinical trials. However, there are scant data on using cervical arthroplasty for traumatic disc herniation. Therefore, this study aimed to investigate the outcomes of patients who underwent cervical arthroplasty for traumatic disc herniation.

METHODS

This cohort included patients who were admitted through the emergency department for trauma. Only patients who had newly-onset, one- or two-level cervical disc disease causing radiculopathy or myelopathy were identified. None of these patients had previously sought for medical attention for such problems. Those patients who had severe spinal cord injury (i.e. American Spinal Injury Association scale A, B or C) or severe myelopathy (i.e. Nurick scale 4 or 5), bony fracture, dislocation, perched facet, kyphotic deformity, or instability were also excluded. An age- and sex-matched one-to-one comparison was made between patients who underwent cervical arthroplasty, on the one hand, and anterior cervical discectomy and fusion (ACDF).

RESULTS

A total of 30 trauma patients (15 in the arthroplasty group and 15 in the ACDF group) were analyzed, with a mean follow-up of 29.6 months. The demographic data were similar. Post-operation, the arthroplasty group had significant improvement in VAS of neck and arm pain, JOA, and NDI when compared to their pre-operation status. Similarly, the ACDF group also improved significantly after the operation. There were no differences between the two groups in post-operative VAS neck and arm pain, and JOA scores. The arthroplasty group maintained a range of motion in the indexed levels and had better NDI scores at 6-months post-operation than the ACDF group.

CONCLUSIONS

For selected patients (i.e. no spinal cord injury, no fracture, and no instability) with traumatic cervical disc herniation, cervical arthroplasty yields similar improvement in clinical outcomes to ACDF and preserves segmental mobility.

Does heterotopic ossification affect the outcomes of cervical total disc replacement? A meta-analysis

STUDY DESIGN

Meta-analysis.

OBJECTIVE

The purpose of this study was to answer the following questions: (1) Does heterotopic ossification (HO) negatively influence clinical outcomes after cervical total disc replacement (CTDR)? (2) Should patients be classified into HO and non-HO groups? (3) Is there a more rational classification?

SUMMARY OF BACKGROUND DATA

Heterotopic ossification has emerged as a common complication after CTDR and has been an important reason for reoperation, thus limiting the use of the surgery. However, the influence of HO on clinical outcomes after CTDR has not been well established.

METHODS

A meta-analysis was conducted with studies identified by searches of MEDLINE, EMBASE, and the Cochrane Library. We calculated the weighted mean differences of the visual analogue scale pain score, Neck Disability Index, and range of motion (ROM). Patients were classified into 2 groups under 3 classifications on the basis of the grade of HO. Results were pooled using a fixed effect model or a random effects model, according to the heterogeneity.

RESULTS

There were significant differences in ROM under all 3 classifications. The visual analogue scale pain score and the Neck Disability Index between the patients with and without HO showed no significant difference after CTDR. Significant differences in visual analogue scale pain score were observed when patients were classified into a "high-grade HO" group (McAfee grades 3 or 4 HO) and a "low-grade HO" group (McAfee grade 0, 1, or 2 HO).

CONCLUSIONS

The presence of HO is not associated with clinical outcomes after CTDR. However, the severity of HO actually impacts clinical outcomes in an inverse manner, which needs further investigation. It is inappropriate to classify patients on the basis of the presence of HO; further studies of the classifications (ROM-affecting HO vs. ROM-preserving HO; high-grade HO vs. low-grade HO) and cervical stability after CTDR are needed.

LEVEL OF EVIDENCE

2.

Postoperative nonsteroidal antiinflammatory drugs and the prevention of heterotopic ossification after cervical arthroplasty: analysis using CT and a minimum 2-year follow-up

OBJECT Heterotopic ossification (HO) after cervical arthroplasty is not uncommon and may cause immobility of the disc. To prevent HO formation, study protocols of clinical trials for cervical arthroplasty undertaken by the US FDA included perioperative use of nonsteroidal antiinflammatory drugs (NSAIDs). However, there are few data supporting the use of NSAIDs to prevent HO after cervical arthroplasty. Therefore, this study aimed to evaluate the efficacy of NSAIDs in HO formation and clinical outcomes. METHODS Consecutive patients who underwent 1- or 2-level cervical arthroplasty with a minimum follow-up of 24 months were retrospectively reviewed. All patients were grouped into 1 of 2 groups, an NSAID group (those patients who had used NSAIDs postoperatively) and a non-NSAID group (those patients who had not used NSAIDs postoperatively). The formation of HO was detected and classified using CT in every patient. The incidence of HO formation, disc mobility, and clinical outcomes, including visual analog scale (VAS) scores of neck and arm pain, neck disability index (NDI) scores, and complications were compared between the two groups. Furthermore, a subgroup analysis of the patients in the NSAID group, comparing the selective cyclooxygenase (COX)-2 to nonselective COX-2 NSAID users, was also conducted for each of the above-mentioned parameters. RESULTS A total of 75 patients (mean age [± SD] 46.71 ± 9.94 years) with 107 operated levels were analyzed. The mean follow-up duration was 38.71 ± 9.55 months. There were no significant differences in age, sex, and levels of arthroplasty between the NSAID and non-NSAID groups. There was a nonsignificantly lower rate of HO formation in the NSAID group than the non-NSAID group (47.2% vs. 68.2%, respectively; p = 0.129). During follow-up, most of the arthroplasty levels remained mobile, with similar rates of immobile discs in the NSAID and non-NSAID groups (13.2% and 22.7%, respectively; p = 0.318). Furthermore, there was a nonsignificantly lower rate of HO formation in the selective COX-2 group than the nonselective COX-2 group (30.8% vs 52.5%, respectively; p = 0.213). The clinical outcomes, including VAS neck, VAS arm, and NDI scores at 24 months postoperatively, were all similar in the NSAID and non-NSAID groups, as well as the selective and nonselective COX-2 groups (all p > 0.05). CONCLUSIONS In this study there was a trend toward less HO formation and fewer immobile discs in patients who used postoperative NSAIDs after cervical arthroplasty than those who did not, but this trend did not reach statistical significance. Patients who used selective COX-2 NSAIDs had nonsignificantly less HO than those who used nonselective COX-2 NSAIDs. The clinical outcomes were not affected by the use of NSAIDs or the kinds of NSAIDs used (selective vs nonselective COX-2). However, the study was limited by the number of patients included, and the efficacy of NSAIDs in the prevention of HO after cervical arthroplasty may need further investigation to confirm these results.

Arthroplasty for cervical spondylotic myelopathy: similar results to patients with only radiculopathy at 3 years' follow-up

Object

Cervical arthroplasty has been accepted as a viable option for surgical management of cervical spondylosis or degenerative disc disease (DDD). The best candidates for cervical arthroplasty are young patients who have radiculopathy caused by herniated disc with competent facet joints. However, it remains uncertain whether arthroplasty is equally effective for patients who have cervical myelopathy caused by DDD. The aim of this study was to compare the outcomes of arthroplasty for patients with cervical spondylotic myelopathy (CSM) and patients with radiculopathy without CSM.

Methods

A total of 151 consecutive cases involving patients with CSM or radiculopathy caused by DDD and who underwent one- or two-level cervical arthroplasty were included in this study. Clinical outcome evaluations and radiographic studies were reviewed. Clinical outcome measurements included the Visual Analog Scale (VAS) of neck and arm pain, Japanese Orthopaedic Association (JOA) scores, and the Neck Disability Index (NDI) in every patient. For patients with CSM, Nurick scores were recorded for evaluation of cervical myelopathy. Radiographic studies included lateral dynamic radiographs and CT for detection of the formation of heterotopic ossification .

Results

Of the 151 consecutive patients with cervical DDD, 125 (82.8%; 72 patients in the myelopathy group and 53 in the radiculopathy group) had at least 24 months of clinical and radiographic follow-up. The mean duration of follow-up in these patients was 36.4 months (range 24–56 months). There was no difference in sex distribution between the 2 groups. However, the mean age of the patients in the myelopathy group was approximately 6 years greater than that of the radiculopathy group (53.1 vs 47.2 years, p < 0.001). The mean operation time, mean estimated blood loss, and the percentage of patients prescribed perioperative analgesic agents were similar in both groups (p = 0.754, 0.652, and 0.113, respectively). There were significant improvements in VAS neck and arm pain, JOA scores, and NDI in both groups. Nurick scores in the myelopathy group also improved significantly after surgery. In radiographic evaluations, 92.5% of patients in the radiculopathy group and 95.8% of those in the radiculopathy group retained spinal motion (no significant difference). Evaluation of CT scans showed heterotopic ossification in 34 patients (47.2%) in the myelopathy group and 25 patients (47.1%) in the radiculopathy group (p = 0.995). At a mean of over 3 years postoperatively, no secondary surgery was reported in either group.

Conclusions

The severity of myelopathy improves after cervical arthroplasty in patients with CSM caused by DDD. At 3-year follow-up, the clinical and radiographic outcomes of cervical arthroplasty in DDD patients with CSM are similar to those patients who have only cervical radiculopathy. Therefore, cervical arthroplasty is a viable option for patients with CSM caused by DDD who require anterior surgery. However, comparison with the standard surgical treatment of anterior cervical discectomy and fusion is necessary to corroborate the outcomes of arthroplasty for CSM.

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.

Differences between arthroplasty and anterior cervical fusion in two-level cervical degenerative disc disease

PURPOSE

Although arthroplasty is an accepted option for two-level disease, there is a paucity of data regarding outcomes of two-level cervical arthroplasty. The current study was designed to determine differences between two-level cervical arthroplasty and anterior fusion.

METHODS

Seventy-seven consecutive patients who underwent two-level anterior cervical operations for degenerative disc disease were divided into the arthroplasty (37 patients) and fusion (40 patients) groups. Clinical outcomes were measured by Visual Analogue Scale (VAS) of neck and arm pain, Japanese Orthopedic Association (JOA) scores, and Neck Disability Index (NDI). Every patient was evaluated by radiography and computed tomography for fusion or detection of heterotopic ossification.

RESULTS

Thirty-seven patients (with 74 levels of Bryan discs) were compared with 40 patients who had two-level anterior fusion (mean follow-up of 39.6 ± 6.7 months). There was no difference in sex, but the mean age of the arthroplasty group was significantly younger (52.1 ± 9.1 vs. 63.0 ± 10.6 years, p < 0.001). The mean estimated blood loss was similar (p = 0.135), but the mean operation time was longer in the arthroplasty group (315.5 ± 82.0 versus 224.9 ± 61.8 min, p < 0.001). At 24 months post-operation, the arthroplasty group had increased their range of motion than pre-operation (23.5° versus 20.1°, p = 0.018). There were significant improvements in neck or arm VAS, JOA scores, and NDI in both groups. However, there were no differences in clinical outcomes or adverse events between the two groups.

CONCLUSIONS

Clinical outcomes of two-level arthroplasty and anterior cervical fusion are similar 39.6 months after surgery. Cervical arthroplasty preserves mobility at the index levels without increased adverse effects.

Elastic resistance of the spine: Why does motion preservation surgery almost fail?

Single metamere motility should not be interpreted merely as a movement on the 3 planes but also, and above all, as elastic resistance to dynamic stress on these 3 planes. In the light of this consideration, the aim of motion preservation is to neutralize excessive movements while preserving the physiological biomechanical properties of the metamere involved to interrupt the progression of degenerative processes and to prevent adjacent segment disease. Despite the fact that a myriad of devices have been developed with the purpose of achieving dynamic neutralization of the spine, there are now some doubts regarding the true efficacy of these devices.

Heterotopic Ossification after Cervical Arthroplasty with ProDisc-C: Time Course Radiographic Follow-up over 3 years

Objective

Heterotopic ossification (HO) is a well-known complication after total hip replacement. But the occurrence rate by the time-course, clinical effect and risk factors of HO after total cervical disc replacement (TCDR) are not well described. The purpose of this study is to evaluate the occurrence rate by the time-course and risk factors for HO after TCDR with a ProDisc-C.

Methods

Thirty-two patients whom followed up more than one year after the TCDR are enrolled. Radiographic study was done at 12, 24 and 36 months after the TCDR and classified HO with McAfee classification. Segmental range of motion, preoperative existence of spondylosis, type of operation, disc space occupying ratio by artificial disc, surgical level are analyzed to identify the risk factors of HO. The visual analog scale and the neck disability index were evaluated preoperatively and at last follow-up time for clinical parameters.

Results

Eighteen patients (56%) showed HO at 12 months, 18 patients (86%) showed HO at 24 months and 6 patients (89%) showed HO at 36 months after the TCDR. Clinical significant HO(Grade 3 and 4) was shown in one patient (3%) at 12 months, 3 patients (14%) at 24 months and 5 patients (56%) at 36 months. Only post-operative follow-up period increases the risk of development clinical significant HO. All patients showed improvement of clinical parameters (p<0.005).

Conclusion

Incidence of HO is getting higher as time course progress. However, there are no relation between clinical outcome and radiologic change of ROM and the grade of HO.

Heterotopic ossification in vertebral interlaminar/interspinous instrumentation: report of a case

We present here a rare case of heterotopic ossification in interspinous/interlaminar Coflex device. The classical surgical indications for these implants are degenerative canal stenosis, discogenic low back pain, disk herniations, facet syndrome, and instability. However, fractures of spinous processes are a potential risk after interspinous/interlaminar devices' implantation. Recently, heterotopic ossification, a well-known complication of hip and knee arthroplasty, has been reported after cervical and lumbar prosthesis. We performed undercutting and implantation of the dynamic interspinous/interlaminar device to treat an adult male patient with L4-L5 stenosis. The patient underwent 45-day imaging and clinical followup, and we observed both a neurological and imaging improvement. A CT bone scan, performed 3 years after surgery for recurrence of neurogenic claudication, showed a new stenosis due to an abnormal ossification all over the device. To our knowledge, this is the first reported case of heterotopic ossification in an interspinous/interlaminar dynamic device. Accordingly, we aim to suggest it as a new complication of interspinous/interlaminar devices.

High prevalence of heterotopic ossification after cervical disc arthroplasty: outcome and intraoperative findings following explantation of 22 cervical disc prostheses

OBJECT

Cervical disc arthroplasty (CDA) has been increasingly used for the treatment of cervical disc herniations. However, the impact of CDA on adjacent-segment degeneration and the degree of heterotopic ossification (HO) of the treated segment remain a subject of controversy. Due to a product failure of the Galileo-type disc prosthesis, 22 of these devices were explanted. The radiological and clinical course in each case was investigated in detail with an emphasis on the incidence of HO and facet joint degeneration 18 months following the operation. Intraoperative findings regarding ossification and implant fixation were documented. Thus, the authors were able to describe the true rate of adjacent-segment degeneration and HO following CDA and the clinical relevance thereof.

METHODS

In all 22 patients, functional radiographic imaging was performed prior to surgery, 3 and 12 months after surgery, and prior to disc prosthesis explantation. At all time points, the range of motion (ROM) in the operated and adjacent segments was determined. A motion index was calculated using the preoperative and all postoperative ROMs (preoperative ROM/postoperative ROM). Computed tomography was used preoperatively to measure the height of the index segment, extent of HO, and the degree of the progression of facet arthrosis, and was used postoperatively prior to prosthesis explantation. Patients completed clinical questionnaires that included a visual analog scale and the Neck Disability Index.

RESULTS

The motion index of the index segment declined gradually from 1.4 at 3 months postoperative to 1.2 prior to explantation, while the motion index of the adjacent upper segment increased from 0.9 to 1.3. The mean ROM of the index segment was 10.4° ± 6.7°, and fusion was observed in 2 (9%) of the 22 patients. Prosthesis migration was present in 3 patients (13.6%). Severe HO (Grades 3 and 4) was present in 17.4%. Computed tomography showed a significant increase of segmental height of the index segment (1.6 ± 1.1 mm, p = 0.035), and a significant increase of left-sided lateral osteophytes (1.7 ± 2.1 mm, p = 0.009). The incidence of severe osteophyte formation (> 2 mm) occurred in 40%. Intraoperative findings reflected the results from CT, with primary lateral proliferation of osteophytes found in approximately 25% of patients. The mean visual analog scale scores were 3.8 ± 2.7 (neck) and 2.4 ± 2.5 (arms), and the mean Neck Disability Index score was 30 ± 22. No correlation was found between radiological and clinical parameters.

CONCLUSIONS

In this study, a higher incidence of HO after CDA could be demonstrated using CT, compared with studies using fluoroscopy only. However, patient selection and/or the operative technique might have contributed to the high prevalence of osteophyte formation. Thus, the exact indication for CDA has to be reconsidered. Because implant migration was detected, using fixation in the present CDA model appears suboptimal.