Intervertebral disc replacement for cervical degenerative disease--clinical results and functional outcome at two years in patients implanted with the Bryan cervical disc prosthesis

Short-term and Long-term Complications of Cervical Disc Arthroplasty

STUDY DESIGN

A narrative review.

OBJECTIVE

This review discusses the short and long-term complications associated with cervical disc arthroplasty (CDA).

SUMMARY OF BACKGROUND DATA

CDA is a safe and effective motion-sparing alternative to fusion for the treatment of cervical disc pathology in patients with cervical radiculopathy or myelopathy. Although CDA offers advantages over fusion within a narrower set of indications, it introduces new technical challenges and potential complications.

METHODS

A systematic search of several large databases, including Cochrane Central, PubMed, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry, was conducted from January 2005 to August 2023 to identify published studies and clinical trials evaluating cervical disc replacement complications and outcomes.

RESULTS

Short-term complications are primarily related to surgical approach and include dysphagia reported as high as ~70%, laryngeal nerve injury ~0%-1.25%, Horner syndrome ~0.06%, hematoma ~0.01%, gross device extrusion ~0.3%, whereas long-term complications include adjacent segment disease reported at ~3.8%, osteolysis ~44%-64%, heterotopic ossification ~7.3%-69.2%, implant failure ~3.3%-3.7%, and implant wear, which varies depending on design.

CONCLUSIONS

Approaches for mitigating complications broadly include meticulous dissection, intraoperative techniques, and diligent postoperative follow-up. This review emphasizes the need for a comprehensive understanding and management of complications to enhance the safety, reproducibility, and success of CDA. As CDA continues to evolve, there remains a critical need for ongoing research to delve deeper into evaluating risk for complications and long-term patient outcomes.

Failure in cervical total disc arthroplasty: single institution experience, systematic review of the literature, and proposal of the RUSH TDA failure classification system

BACKGROUND CONTEXT

Cervical total disc arthroplasty (TDA) is an alternative procedure to anterior cervical discectomy and fusion that facilitates neural decompression while both preserving motion of the spinal unit and decreasing the risk for degenerative changes at adjacent segments. However, due to its more recent introduction in clinical practice and low complication rates, the modes by which TDA may fail remain to be described.

PURPOSE

This study sought to identify the modes and frequencies of cervical TDA failure in order to propose a novel classification system.

STUDY DESIGN

Retrospective cohort and systematic review.

PATIENT SAMPLE

Patients who underwent single or two-level TDA for cervical radiculopathy or myelopathy at a single institution and in the literature of medium and large prospective studies.

OUTCOME MEASURES

Cervical TDA failure, defined as subsequent surgical intervention at the index segment.

METHODS

This study retrospectively reviewed patients who underwent single or two-level TDA for cervical radiculopathy or myelopathy at a single institution to identify the potential implant failure modes. A systematic review and meta-analysis of prospective data in the literature was then performed to further supplement failure mode identification and to describe the rates at which the various failure types occurred. Statistical analysis included between-group comparisons of Non-Failed and Failed patients and frequencies of each failure type among Failed patients.

RESULTS

A retrospective review at our institution of 169 patients (201 levels) identified eight failures, for a failure rate of 4.7%. Additionally, seven patients were revised who had the primary surgery at an outside institution. The systematic review of 3976 patients (4525 levels) identified 165 (4.1%) additional failures. Using this data, six primary failure types were classified, with several subtypes. These include recurrent or persistent index-level stenosis (Type I); migration (Type II) presenting as gross extrusion (A) or endplate failure with subsidence/acute fracture (B); instability (Type III) due to mechanical loosening (A), septic loosening (B), or device fracture (C); device motion loss (Type IV) such as "locking" of the device in kyphosis; implantation error (Type V) due to malposition (A) or improper sizing (B); and wear (Type VI) either without osteolysis (A) or with wear-particle-induced osteolysis (B). Stenosis (Type I) was the most common mode of failure found both through retrospective review and in the literature.

CONCLUSIONS

Cervical TDA fails through six primary mechanisms. While rates of certain failures requiring subsequent surgical intervention are low, it is possible that these complications may become more prevalent upon further longitudinal observation. Thus, future application and validation of this classification system is warranted to evaluate how failure frequencies change over time and with larger patient samples.

Viscoelastic cervical total disc replacement devices: Design concepts

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

Top 100 Cited Articles on Spinal Disc Arthroplasty Research

STUDY DESIGN

A bibliometric review of current literature.

OBJECTIVE

The purpose of this study was to identify and analyze the 100 most cited articles in spinal disc arthroplasty (SDA) research.

SUMMARY OF BACKGROUND DATA

In the last several decades, SDA has been widely performed all over the world, with increasing popularity of cervical disc arthroplasty (CDA). While there is a large number of articles on this topic, to our knowledge, there is no bibliometric analysis yet.

METHODS

All databases from the Web of Science were searched in a three-step approach. The information of the 100 most cited studies was collected, including title, first and last author, year of publication, journal, total citations, geographic origin, subspecialty, and types of artificial intervertebral disc for further analysis.

RESULTS

The 100 most-cited articles were published from 1966 to 2015 in 9 different journals and were cited from 66 to 346 times. A total of 11 countries contributed to the 100 articles and the United States topped the list, with 54 articles, followed by Germany and France, with 10 and nine articles, respectively. There were more studies in CDA (n = 53) than lumbar disc arthroplasty (n = 35). Most of the studies reported clinical and radiographic outcomes (n = 33). The most productive periods were from 2006 to 2010. The majority of publications were in Spine, which published 43 articles. In total, 12 authors published more than two articles on the list.

CONCLUSION

Of the top 100 most cited articles on SDA, cervical papers outnumbered lumbar articles and the United States had 55 articles, with no other countries having more than 10. Our paper can help readers determine which of the thousands of articles on this topic are the most impactful and important ones to be familiar with.

LEVEL OF EVIDENCE

3.

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.

The Effect of Footprint Mismatch on Heterotopic Ossification After Cervical Disk Replacement

STUDY DESIGN

This was a retrospective study.

OBJECTIVE

The objective of this study was to analyze risk factors of heterotopic ossification (HO) after cervical disk replacement (CDR) and evaluate the effect of footprint mismatch on HO.

SUMMARY OF BACKGROUND DATA

Incidence of HO after CDR is high, but the exact related factors have not been fully elucidated.

MATERIALS AND METHODS

Radiographic data of patients who had undergone CDR with Prestige LP or Discover prosthesis in Tongji Hospital from July 2012 to December 2015 were reviewed. HO was graded according to McAfee classification and classified according to Jin morphologic classification. Footprint matching degree was evaluated using 3-dimensional computed tomographic images. Cervical sagittal alignment, functional spinal unit height, and range of motion were measured on radiographs. Preexisting degeneration was scored using Walraevens scoring system. Postulated risk factors including general factors, cervical sagittal alignment, functional spinal unit height, range of motion, postoperative biomechanical changes, preexisting degeneration, number of surgical levels, prosthesis type, use of nonsteroid anti-inflammatory drugs, and footprint matching degree were analyzed by first univariate tests, and then multivariate logistic regression was done to examine the relation with HO occurrence. Effect of footprint mismatch on type 1 HO of morphologic classification was evaluated.

RESULTS

Data of 46 patients were collected; 43 were finally evaluated with a total 57 prostheses implanted, with a mean follow-up duration of 41.16±12.49 months. No significant differences in basic characteristics existed between 2 prosthesis groups, except follow-up time. Incidence of HO was 66.7%. Mean footprint matching degree in sagittal plane was 0.877±0.068 and in coronal plane was 0.852±0.092. Mean overall footprint matching degree was 0.699±0.102 (range: 0.388-0.993). Prosthesis type and footprint matching degree were significantly related with HO among all postulated risk factors in both univariate and multivariate analyses (P<0.05); the latter had larger Exp(B). Type 1 HO occurrence significantly related with footprint mismatch.

CONCLUSIONS

Incidence of HO after CDR was high, and serious footprint mismatch existed. HO occurrence was significantly related with prosthesis type and footprint matching degree; the latter played a more important role.

Artificial Discs in Cervical Disc Replacement: A Meta-Analysis for Comparison of Long-Term Outcomes

BACKGROUND

Cervical disc replacement (CDR) has emerged as an alternative to anterior cervical discectomy and fusion for the surgical treatment of degenerative cervical disc disease. Although comparison of the 2 techniques has been studied in the literature, a thorough assessment of all artificial discs between each has not been performed. The objective of the present study was to examine the long-term outcomes of 5 artificial discs.

METHODS

An electronic literature search was conducted for studies of CDR devices for all years available. Only articles in English were included. Heterotopic ossification, adjacent segment disease, and reoperation comprised the primary outcomes of interest. Pooled descriptive statistics with effect size (ES) and 95% confidence interval were used to synthesize the outcomes for each device.

RESULTS

Sixty-five studies (n = 5785) were included in the analysis. Comparison of the incidence of grade III/IV heterotopic ossification showed a significant variability between the 5 devices (P < 0.001) with ProDisc-C (ES, 38%; 95% confidence interval [CI], 24%-54%) having the highest incidence rate. Overall rate of adjacent segment disease was 14% (95% CI, 7%-23%) with significant associated heterogeneity (P < 0.001). Regarding 2-year reoperation risk, the overall incidence rate was 2% (95% CI, 1%-3%), with nonsignificant variability between devices (P = 0.63). The highest rate was observed in the Discover group (ES, 4%; 95% CI, 0%-13%).

CONCLUSIONS

The results of the present meta-analysis indicate that surgical and clinical outcomes may differ among different CDR devices. These findings may assist surgeons in tailoring their decision making to specific patient profiles. Future multicenter efforts are needed to validate associations found in this study.

Normal intervertebral segment rotation of the subaxial cervical spine: An in vivo study of dynamic neck motions

Background

Accurate knowledge of the intervertebral center of rotation (COR) and its corresponding range of motion (ROM) can help understand development of cervical pathology and guide surgical treatment.

Methods

Ten asymptomatic subjects were imaged using MRI and dual fluoroscopic imaging techniques during dynamic extension-flexion-extension (EFE) and axial left-right-left (LRL) rotation. The intervertebral segment CORs and ROMs were measured from C34 to C67, as the correlations between two variables were analyzed as well.

Results

During the EFE motion, the CORs were located at 32.4 ± 20.6%, -2.4 ± 11.7%, 21.8 ± 12.5% and 32.3 ± 25.5% posteriorly, and the corresponding ROMs were 13.8 ± 4.3°, 15.1 ± 5.1°, 14.4 ± 7.0° and 9.2 ± 4.3° from C34 to C67. The ROM of C67 was significantly smaller than other segments. The ROMs were not shown to significantly correlate to COR locations (r = −0.243, p = 0.132). During the LRL rotation cycle, the average CORs were at 85.6 ± 18.2%, 32.3 ± 25.3%, 15.7 ± 12.3% and 82.4 ± 31.3% posteriorly, and the corresponding ROMs were 3.5 ± 1.7°, 6.9 ± 3.8°, 9.6 ± 4.1° and 2.6 ± 2.5° from C34 to C67. The ROMs of C34 and C67 was significantly smaller than those of C45 and C56. A more posterior COR was associated with a less ROM during the neck rotation (r = −0.583, p < 0.001). The ROMs during EFE were significantly larger than those during LRL in each intervertebral level.

Conclusion

The CORs and ROMs of the subaxial cervical intervertebral segments were segment level- and neck motion-dependent during the in-vivo neck motions.

The translational potential of this article

Our study indicates that the subaxial cervical intervertebral CORs and ROMs were segment level- and neck motion-dependent. This may help to improve the artificial disc design as well as surgical technique by which the neck functional motion is restored following the cervical arthroplasty.

Cervical Artificial Disc Replacement With Discover Prosthesis Does Not Reduce the Midterm Risk of Heterotopic Ossification: Results of a Cohort Study

STUDY DESIGN

A prospective cohort study with 79 patients.

OBJECTIVE

To analyze the midterm incidence of heterotopic ossification (HO) after cervical artificial disc replacement with Discover prosthesis in treatment of cervical degenerative disc disease.

MATERIALS AND METHODS

A cohort of 79 patients with 102 Discover prostheses (56 monosegment and 23 bisegments) was evaluated. Clinical and radiographic follow-up was performed. The performance of HO of the operative segments was assessed annually after the operation for 4 years.

RESULTS

Early follow-up at 2 years postsurgical treatment showed satisfactory clinical outcomes. No significant changes on the mean Japanese Orthopaedic Association and Visual Analog Scale scores were detected at 3 and 4 years postoperation. The occurrence rate of HO was 5.9% in 1-year follow-up and 17.6% in 2-year follow-up, and then the percentages increased to 49.2% in 3-year follow-up and 65.6% in 4-year follow-up, respectively. No association between the HO grades and the type of the surgical segment was detected by the Fisher exact test (P-value=0.56). No prosthesis subsidence or excursion was identified during the whole follow-up period.

CONCLUSIONS

The use of Discover prosthesis resulted in satisfactory clinical outcomes after operation. However, the new prosthesis did not reduce the midterm risk of HO, despite the fact that the observed incidence was relatively low in the early follow-up.

The prevalence of heterotopic ossification among patients after cervical artificial disc replacement: A systematic review and meta-analysis

BACKGROUND

Prevalence estimates of heterotopic ossification (HO) following cervical artificial disc replacement (ADR) varied widely in previous studies. We conducted a systematic review and meta-analysis to summarize its point prevalence.

METHODS

Electronic searches of PubMed, Web of Science, Embase, and Cochrane Library databases were conducted to identify studies that reported prevalence of HO. Definitions of HO and severe HO were based on McAfee grading system. Random-effects model was used to estimate the pooled prevalence. We conducted subgroup analyses according to the different length of follow-up time, and performed univariate metaregression analyses to explore the effects of potential variables on the overall prevalence.

RESULTS

A total of 38 studies were included in this study. The pooled data showed that the prevalence of HO after cervical ADR within the 1 to 2 years, 2 to 5 years, and 5 to10 years of follow-up was 38.0% (95% confidence interval [CI], 30.2%-46.5%), 52.6% (95% CI, 43.1%-61.9%), and 53.6% (95% CI, 40.0%-66.7%), respectively, while the prevalence of severe HO was 10.9% (95% CI, 9.0%-13.2%), 22.2% (95% CI, 15.5%-30.7%), and 47.5% (95% CI, 30.0%-65.8%), respectively. Follow-up time was positively associated with the prevalence of severe HO (P < .01), and the 1-month growth of mean follow-up went with 0.63% increase of severe HO.

CONCLUSION

This meta-analysis reported data on the prevalence of HO and severe HO after cervical ADR, and provided information on its process of development. These should be useful to enable surgeons and patients to gain a better understanding of HO after cervical ADR.

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.

Heterotopic ossification following single-level anterior cervical discectomy and fusion: results from the prospective, multicenter, historically controlled trial comparing allograft to an optimized dose of rhBMP-2

OBJECTIVE

Heterotopic ossification (HO) has been reported following total hip, knee, cervical, and lumbar arthroplasty, as well as following posterolateral lumbar fusion using recombinant human bone morphogenetic protein–2 (rhBMP-2). Data regarding HO following anterior cervical discectomy and fusion (ACDF) with rhBMP-2 are sparse. A subanalysis was done of the prospective, multicenter, investigational device exemption trial that compared rhBMP-2 on an absorbable collagen sponge (ACS) versus allograft in ACDF for patients with symptomatic single-level cervical degenerative disc disease.

METHODS

To assess differences in types of HO observed in the treatment groups and effects of HO on functional and efficacy outcomes, clinical outcomes from previous disc replacement studies were compared between patients who received rhBMP-2/ACS versus allograft. Rate, location, grade, and size of ossifications were assessed preoperatively and at 24 months, and correlated with clinical outcomes.

RESULTS

Heterotopic ossification was primarily anterior in both groups. Preoperatively in both groups, and including osteophytes in the target regions, HO rates were high at 40.9% and 36.9% for the rhBMP-2/ACS and allograft groups, respectively (p = 0.350). At 24 months, the rate of HO in the rhBMP-2/ACS group was higher than in the allograft group (78.6% vs 59.2%, respectively; p < 0.001). At 24 months, the rate of superior-anterior adjacent-level Park Grade 3 HO was 4.2% in both groups, whereas the rate of Park Grade 2 HO was 19.0% in the rhBMP-2/ACS group compared with 9.8% in the allograft group. At 24 months, the rate of inferior-anterior adjacent-level Park Grade 2/3 HO was 11.9% in the rhBMP-2/ACS group compared with 5.9% in the allograft group. At 24 months, HO rates at the target implant level were similar (p = 0.963). At 24 months, the mean length and anteroposterior diameter of HO were significantly greater in the rhBMP-2/ACS group compared with the allograft group (p = 0.033 and 0.012, respectively). Regarding clinical correlation, at 24 months in both groups, Park Grade 3 HO at superior adjacent-level disc spaces significantly reduced range of motion, more so in the rhBMP-2/ACS group. At 24 months, HO negatively affected Neck Disability Index scores (excluding neck/arm pain scores), neurological status, and overall success in patients in the rhBMP-2/ACS group, but not in patients in the allograft group.

CONCLUSIONS

Implantation of rhBMP-2/ACS at 1.5 mg/ml with polyetheretherketone spacer and titanium plate is effective in inducing fusion and improving pain and function in patients undergoing ACDF for symptomatic single-level cervical degenerative disc disease. At 24 months, the rate and dimensions (length and anteroposterior diameter) of HO were higher in the rhBMP-2/ACS group. At 24 months, range of motion was reduced, with Park Grade 3 HO in both treatment groups. The impact of Park Grades 2 and 3 HO on Neck Disability Index success, neurological status, and overall success was not consistent among the treatment groups. The study data may offer a deeper understanding of HO after ACDF and may pave the way for improved device designs.

Clinical trial registration no.: IDE# G060021; data compared with pooled data from control arms of IDE# G010188/NCT00642876 and IDE# G000123/NCT00437190 (www.clinicaltrials.gov).

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

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

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.

Cervical arthroplasty: a critical review of the literature

BACKGROUND CONTEXT

Cervical disc arthroplasty (CDA) is a motion-preserving procedure that is an alternative to fusion. Proponents of arthroplasty assert that it will maintain cervical motion and prevent or reduce adjacent segment degeneration. Accordingly, CDA, compared with fusion, would have the potential to improve clinical outcomes. Published studies have varying conclusions on whether CDA reduces complications and/or improves outcomes. As many of these previous studies have been funded by CDA manufacturers, we wanted to ascertain whether there was a greater likelihood for these studies to report positive results.

PURPOSE

To critically assess the available literature on cervical arthroplasty with a focus on the time of publication and conflict of interest (COI).

STUDY DESIGN/SETTING

Review of the literature.

METHODS

All clinical articles about CDA published in English through August 1, 2013 were identified on Medline. Any article that presented CDA clinical results was included. Study design, sample size, type of disc, length of follow-up, use of statistical analysis, quality-of-life (QOL) outcome scores, COI, and complications were recorded. A meta-analysis was conducted stratifying studies by COI and publication date to identify differences in complication rates reported.

RESULTS

Seventy-four studies were included that investigated 8 types of disc prosthesis and 22 met the criteria for a randomized controlled trial (RCT). All Level Ib RCTs reported superior quality-of-life outcomes for CDA versus anterior cervical discectomy and fusion (ACDF) at 24 months. Fifty of the 74 articles (68%) had a disclosure section, including all Level Ib RCTs, which had significant COIs related to the respective studies. Those studies without a COI reported mean weighted average adjacent segment disease rates of 6.3% with CDA and 6.2% with ACDF. In contrast, the reverse was reported by studies with a COI, for which the averages were 2.5% with CDA and 6.3% with ACDF. Those studies with a COI (n=31) had an overall weighted average heterotopic ossification rate of 22%, whereas those studies with no COI (n=43) had a rate of 46%.

CONCLUSIONS

Associated COIs did not influence QOL outcomes. Conflicts of interest were more likely to be present in studies published after 2008, and those with a COI reported greater adjacent segment disease rates for ACDF than CDA. In addition, heterotopic ossification rates were much lower in studies with COI versus those without COI. Thus, COIs did not affect QOL outcomes but were associated with lower complication rates.

Multi-level cervical disc arthroplasty (CDA) versus single-level CDA for the treatment of cervical disc diseases: a meta-analysis

PURPOSE

Cervical disc arthroplasty (CDA) was developed to treat cervical degenerated disc diseases with the advantages of preserving the kinematics of the functional spinal unit. However, the safety and reliability of multi-level CDA are still controverted when comparing to the single-level CDA. It has shown unclear benefits in terms of clinical results, functional recovery, heterotopic ossification, and the need for secondary surgical procedures. The purpose of this study is to estimate the effectiveness of multi-level cervical arthroplasty over single-level CDA for the treatment of cervical spondylosis and disc diseases.

METHODS

To compare the studies of multi-level CDA versus single-level CDA in patients with cervical spondylosis that reported at least one of the following outcomes: functionality, neck pain, arm pain, quality of life, reoperation and incidence of heterotopic ossification, electronic databases (Medline, Embase, Pubmed, Cochrane library, and Cochrane Central Register of Controlled Trials) were searched. No language restrictions were used. Two authors independently assessed the methodological quality of included studies and extracted the relevant data.

RESULTS

Out of Eight cohorts that were included in the study, four were prospective cohorts and the other four were retrospective. The results of the meta-analysis indicated that there was no significant difference in neck disability index scores, neck visual analog scale (VAS), arm VAS, morbidity of reoperation, heterotopic ossification, and parameters of living quality when comparing multi-level CDA with single-level CDA at 1 and 2 years follow-up postoperatively (p > 0.05).

CONCLUSIONS

The meta-analysis revealed that the outcomes and functional recovery of patients performed with multi-level CDA are equivalent to those with single-level CDA, which suggests the multi-level CDA is as effective and safe as single-level invention for the treatment of cervical spondylosis. Nonetheless, more well-designed studies with large groups of patients are needed to provide further evidence for the benefit and reliability of multi-level CDA in the treatment of cervical disc diseases.

Clinical and radiographic outcomes of dynamic cervical implant replacement for treatment of single-level degenerative cervical disc disease: a 24-month follow-up

PURPOSE

To determine the role of dynamic cervical implant (DCI) replacement for single-level degenerative cervical disc disease in Chinese patients.

METHODS

Thirty patients with single-level degenerative cervical disc disease were prospectively enrolled between April 2010 and August 2010 (12 women, 18 men; mean age 56.5 years). All patients underwent anterior cervical decompression, DCI replacement, clinical and radiological assessments preoperatively and at 1, 6, 12, and 24 months postoperatively, and Japanese Orthopaedic Association (JOA), Visual Analogue Scale (VAS), Neck Disability Index (NDI), and Short Form 36 (SF-36) scores. Lateral neutral radiographs provided the intervertebral space height. Lateral dynamic radiographs were taken to measure the range of motion (ROM) of the cervical spine and functional spinal unit (FSU) of the treated segment. We compared the amount of motion of the adjacent vertebral endplate and the intrinsic motion of the implant and calculated a correlation analysis.

RESULTS

DCI showed good clinical and radiographic outcomes. At the final follow-up, JOA, VAS, NDI, and SF-36 average scores improved significantly. The intervertebral space height increased slightly after operation and was maintained during follow up. The ROM of the cervical spine and FSU decreased at early follow-up, but recovered to the preoperative level within 1-2 years. There was a high index of linear correlation between the motion of the adjacent vertebral endplate and the intrinsic motion of the implant.

CONCLUSIONS

DCI provided elastic dynamic stability for the targeted segment, and restored and sustained intervertebral space height and ROM of the cervical spine.

Total cervical disk replacement with a prestige LP® prosthesis: clinical and functional outcomes

Objective: To determine the clinical and functional results of short- and medium-term cervical arthroplasty with the Prestige LP® prosthesis for the treatment of compressive myelopathy, radiculopathy and axial pain with radiculopathty. Methods: This retrospective study, conducted from 2009 to 2012, included 18 patients. Only 16 were found for the second stage of research, conducted in 2011 and 2012. Pre- and postoperative assessments were carried out using the CSOQ (Cervical Spine Outcomes Questionnaire). Odom criteria were used only in the postoperative evaluation. Both were translated and adapted to the local culture. Results: There was no postoperative radiculopathy or other complications requiring prolonged hospitalization. In most patients, there was a significant improvement in axial pain and radiculopathy, and there was only one indication of conversion to fusion. Conclusions: In selected cases of cervical degenerative disc disease, herniated cervical disc and compressive myeolopathy, cervical arthroplasty proved to be an effective and safe treatment in the short and medium terms.

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.

The predisposing factors for the heterotopic ossification after cervical artificial disc replacement

BACKGROUND CONTEXT

Heterotopic ossification (HO) is defined as a formation of bone outside the skeletal system. The reported HO occurrence rate in cervical artificial disc replacement (ADR) is unexpectedly high and is known to vary. However, the predisposing factors for HO in cervical ADR have not yet been elucidated.

PURPOSE

Investigation of the predisposing factors of HO in cervical arthroplasty and the relationship between degeneration of the cervical spine and HO occurrence.

STUDY DESIGN

Retrospective study to discover predisposing factors of HO in cervical arthroplasty.

PATIENT SAMPLE

A total of 170 patients who underwent cervical ADR were enrolled including full follow-up clinical and radiologic data.

OUTCOME MEASURES

Radiologic outcomes were assessed by identification of HOs according to McAfee's classifications.

METHODS

This study enrolled a total of 170 patients who underwent cervical ADR. Pre-existing degenerative change included anterior or posterior osteophytes, ossification of the anterior longitudinal ligament, posterior longitudinal ligament, or ligamentum nuchae. The relationships between basic patient data, pre-existing degenerative change, and HO were investigated using linear logistic regression analysis.

RESULTS

Among all 170 patients, HO was found in 69 patients (40.6%). Among the postulated predisposing factors, only male gender and artificial disc device type were shown to be statistically significant. Unexpectedly, preoperative degenerative changes in the cervical spine exerted no significant influence on the occurrence of HOs. The odds ratio of male gender compared with female gender was 2.117. With regard to device type, the odds ratios of Mobi-C (LDR medical, Troyes, France) and ProDisc-C (Synthes, Inc., West Chester, PA, USA) were 5.262 and 7.449, respectively, compared with the Bryan disc.

CONCLUSIONS

Definite differences in occurrence rate according to the gender of patients and the prosthesis type were identified in this study. Moreover, factors indefinably expected to influence HO in the past were not shown to be risk factors thereof, the results of which may be meaningful to future studies.

Cervical arthroplasty with Discover prosthesis: clinical outcomes and analysis of factors that may influence postoperative range of motion

PURPOSE

The aim of this current study was to analyze the clinical outcomes after Discover cervical disc replacement and its effects on maintaining cervical lordosis and range of motion (ROM). The possible factors influencing postoperative ROM were analyzed.

METHOD

27 men and 28 women with a mean age of 46.4 ± 8.7 years were prospectively followed up for 2 years. Clinical outcomes were assessed using Japanese Orthopedic Association (JOA), Neck Disability Index (NDI), visual analog scale (VAS) and Odom's criteria. Radiographic information including segment and overall alignment, functional spinal unit (FSU) and overall ROM, and disc heights were prospectively collected during the follow-up. The correlations between the postoperative FSU ROM at last follow-up and influencing factors were analyzed.

RESULTS

Mean NDI, JOA and VAS scores showed statistical improvements at last follow-up. Anterior migration of the prosthesis was detected in six cases. Heterotopic ossification was observed in ten patients. Mean FSU angle, endplate angle of the treated level and mean overall cervical alignment were all improved significantly at last follow-up (P < 0.001). However, mean FSU ROM of the treated segment significantly decreased postoperatively (P = 0.008), while mean overall ROM showed no significant differences. A significant correlation was found between preoperative FSU ROM and postoperative FSU ROM by the Pearson correlation coefficient (r = 0.325, P = 0.034). Multiple linear regression analysis confirmed that preoperative FSU ROM contributed independently to a model with a coefficient of determination of 0.37 (P = 0.034).

CONCLUSIONS

In the 2 years follow-up, the Discover cervical disc arthroplasty has provided satisfactory clinical outcomes. It was able to substantially restore segment and overall cervical alignment while partially maintaining segment and overall cervical ROM. Additionally, we found that postoperative FSU ROM positively correlated with preoperative FSU ROM.

Five-year results of cervical disc prostheses in the SWISSspine registry

BACKGROUND

The Swiss Federal Office of Public Health demanded a nationwide HTA-registry for cervical total disc arthroplasty (TDA), to decide about its reimbursement. The goal of the SWISSspine registry is to generate evidence about the safety and efficiency of cervical TDA.

MATERIALS AND METHODS

Three hundred thirty-two cases treated between 3.2005 and 6.2006 who were eligible for 5 years follow-ups were included in the study. Follow-up rates for 3-6 months, 1, 2 and 5 years were 84.6, 74.4, 50.6 and 64.8 %, respectively. Outcome measures were neck and arm pain, medication, quality of life, intraoperative and postoperative complication and revision rates. In addition, segmental mobility, ossification, adjacent and distant segment degeneration were analyzed at the 5-year follow-up.

RESULTS

There was significant, clinically relevant and lasting reduction of neck (preop/postop 60/21 VAS points) and arm pain (preop/postop VAS 67/17) and a consequently decreased analgesics consumption and quality of life improvement (preop/postop 0.39/0.82 EQ-5D points) until the 5-year follow-up. The rates for intraoperative and early postoperative complications were 0.6 and 7.2 %, respectively. In 0.6 % an early and in 3.9 % a late revision surgery was performed. At the 5-year follow-up, the average range of motion of the mobile segments (88.2 %) was 10.2°. In 40.7 % of the patients osteophytes at least potentially affecting range of motion were seen.

CONCLUSIONS

Cervical TDA appeared as safe and efficient in long-term pain alleviation, consequent reduction of pain killer consumption and in improvement of quality of life. The improvement is stable over the 5 years postoperative period. The vast majority of treated segments remained mobile after 5 years, although 40.7 % of patients showed osteophytes.

Heterotopic ossification in cervical disc arthroplasty: Is it clinically relevant?

STUDY DESIGN

 Retrospective cohort study.

OBJECTIVE

 To analyze the presence and clinical relevance of heterotopic ossification (HO) at 3 years mean follow-up.

METHODS

 Thirty patients suffering from cervical radiculopathy and/or myelopathy treated with anterior disc replacement (ADR) were studied. HO was classified using the McAfee grading system. Range of motion was measured from flexion and extension x-rays. Short-form 36 and neck disability index (NDI) assessed functional outcome.

RESULTS

 Forty-five prostheses were implanted in 30 patients with cervical radiculopathy and/or myelopathy, mean age 40.9 years. Nineteen patients received 1 level and 11 patients received multilevel disc replacement. The incidence rate of HO was 42.2% (19 levels). Segmental range of motion was ≥3° in 93.8% of patients with HO. There was no significant difference in functional scores between those who did and those who did not develop HO. Males tended to develop HO more frequently than females, though this was not statistically significant. The indication for surgery (soft disc hernia or spondylosis) was not associated with the formation of HO.

CONCLUSIONS

 Functional improvement is maintained despite the presence of HO following cervical disc arthroplasty. Indications for arthroplasty should not be halted by the risk of HO. [Table: see text] The definiton of the different classes of evidence is available on page 83.

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

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

An analysis of heterotopic ossification in cervical disc arthroplasty: a novel morphologic classification of an ossified mass

BACKGROUND CONTEXT

Although the precise cause of heterotopic ossification (HO) remains unclear, it is certain that it increases with time. The reason why the reported occurrence rate has been given as a wider range is that there were no clinical reports that have addressed the occurrence rate based on the morphology and position.

PURPOSE

The aim of this retrospective study was to determine whether radiological parameters had an influence on the formation of HO and to compare the results after cervical arthroplasty using Bryan (Medtronic Sofamor Danek, Memphis, TN, USA), PCM (Cervitech, Rockaway, NJ, USA), and Prestige LP (Medtronic Sofamor Danek) implants.

STUDY DESIGN/SETTING

A retrospective study.

PATIENT SAMPLE

Eighty-one patients were included.

OUTCOME MEASUREMENT

The occurrence of HO was determined at the four corners of the disc space according to the McAfee classification system. Heterotopic ossifications were classified into Type 1, Type 2, and Type 3 HOs (end plate, traction spur, and teardrop types) based on their morphologic features. The presence of preoperative ossifications, sex, type of device, operated level, hybrid implantation, depth behind the prosthesis, cervical lordotic angle, and segmental angle between the footplates of the prosthesis were assessed as predictors in terms of location and morphologic features.

METHODS

Eighty-one patients after 95 cervical arthroplasties using the Bryan (35 segments), PCM (30 segments), and Prestige LP implants (30 segments) underwent postoperative radiographs or three-dimensional computed tomography with a mean follow-up period of 46, 39, and 30 months, respectively, after the operation.

RESULTS

The overall incidence of all cases and one-level subgroup were 64.2% and 60.3%, respectively. According to the types of device, the incidence of HO was 49% (Bryan), 80% (PCM), and 60% (Prestige). Type 1 HO (62.1%) was found only in the posterosuperior disc space. Type 2 HO (13.7%) was primarily detected in the anterosuperior disc space rather than the posterosuperior disc space (3.2%). Type 3 HO (4.2%) developed only in the anterior disc space. In the anterior disc space, the incidence of Type 2 and Type 3 HOs was highest in the PCM group. In the posterior disc space, the Bryan group showed a lower proportion in the high McAfee class than the other device groups. The occurrence of Type 1 HO in the posterosuperior disc space was significantly related with the presence of preoperative ossification (p=.030), ossification in the ligamentum nuchae (p=.027), male sex (p=.042), and PCM device (p=.012). A well-fitting (p<.002) and less lordotic segmental angle (p<.015) were correlated with Type 1 HO. Implantation in the upper cervical level (p=.016) and hybrid implantation with cage (p=.033) or artificial disc (p=.048) on the upper adjacent level were significant risk factors for anterior Type 2 HO. Cervical lordotic angle at 1 month after surgery had a significant connection with the occurrence of anterior Type 2 HO in both groups of all cases (p=.032) and one-level subgroup (p=.000).

CONCLUSIONS

Type 1 HO developed mostly in the posterior disc space. Type 2 HO was the dominant type in the anterior disc space. Type 3 HO developed only in the anterior disc space. It is certain that both Type 1 and Type 2 HOs are related to biomechanical stresses (compressive force for Type 1 HO and traction force for Type 2 HO). It is suggested that a cervical arthroplasty should be selected in terms of the implant level, hybrid conditions on the upper adjacent segment, disc design vulnerable to the pseudotranslation, the presence of preoperative ossification, and fitting implants to end plates to reduce the development of HO.

Artroplastia total de disco cervical com prótese de Bryan: resultados clínicos e funcionais

OBJETIVO: Avaliar resultados da artroplastia total disco cervical com a prótese de Bryan para tratamento da cervicobraquialgia (radiculopatia) e da mielopatia compressiva. MÉTODOS: No período de 2002 a 2007, a equipe da CECOL operou 65 pacientes. Somente 28 pacientes foram localizados em 2010 para uma nova coleta de dados. Foi feita avaliação pré e pós-operatória, utilizando-se o questionário CSOQ (Cervical Spine Outcomes Questionnaire). Os critérios de Odom foram utilizados somente na avaliação pós-operatória. Ambos foram traduzidos e adaptados para cultura local. RESULTADOS: Houve melhora funcional e sintomática significativa na maioria dos pacientes. A atenuação da dor cervical (axial) e braquial (radicular) foi semelhante. Os critérios Odom indicaram 82,1% de bons e ótimos resultados, 10% satisfatórios e 7% ruins. Houve apenas uma complicação (3%), que foi revertida com a artrodese anterior. CONCLUSÕES: A artroplastia total de disco cervical demonstrou ser um método seguro e eficaz para tratamento de casos selecionados de hérnia de disco cervical associada a radiculopatia e/ou mielopatia a curto e médio prazo.

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.

The effects of carpentry on heterotopic ossification and mobility in cervical arthroplasty: determination by computed tomography with a minimum 2-year follow-up

Object

Heterotopic ossification (HO) after cervical arthroplasty can limit the mobility of an artificial disc. In this study the authors used CT scanning to assess the formation of HO with the goal of investigating the correlation between the carpentry of arthroplasty, formation of HO, mobility, and clinical outcomes.

Methods

A retrospective review of medical records, radiological studies, and clinical evaluations was conducted for consecutive patients who underwent 1- or 2-level cervical arthroplasty with the Bryan disc. The patients underwent follow-up for more than 24 months. The formation of HO was assessed using CT scanning as the final determination. The perfectness of carpentry for each arthroplasty level was scrutinized using criteria composed of 2 parameters (postoperative shell kyphosis and inadequate endplate coverage). Levels were divided into the optimal carpentry group and the suboptimal carpentry group. Radiographic and clinical outcomes, including the visual analog scale and neck disability index, were compared between the groups.

Results

A total of 107 levels of Bryan discs were placed in 75 patients (mean age 46.71 ± 9.94 years) and were analyzed. There was a male predominance of 68.0% (51 men), and the mean follow-up duration was 38.56 ± 9.66 months. Heterotopic ossification was identified in 60 levels (56.1%) by CT scanning. Most cases of HO were low grade and did not correlate with the limitation in the segmental motion of the arthroplasty device. There were no significant differences in terms of age, sex, and number of arthroplasty levels between the optimal and the suboptimal carpentry groups. However, the suboptimal carpentry group had significantly more high-grade HO (≥ Grade 2) than the optimal carpentry group (13 levels [12.1%] vs 7 levels [6.5%], p = 0.027). There were also more immobile (range of motion < 3°) artificial discs in the suboptimal carpentry group than the optimal carpentry group (11 levels [10.3%] vs 4 levels [3.7%], p = 0.010). The clinical outcomes (neck and arm visual analog scale scores and Neck Disability Index) in both groups were similarly good.

Conclusions

Shell kyphosis and inadequate endplate coverage have adverse effects on the formation of HO and segmental mobility after cervical arthroplasty with the Bryan artificial disc. Appropriate carpentry is the more important factor in determining the maintenance of segmental motion. Although the midterm clinical outcome remained similarly good regardless of HO, the carpentry of cervical arthroplasty should not be overlooked. Further studies are needed to clarify the etiology of HO.

Cervical myelopathy after cervical total disc arthroplasty: case report and literature review

STUDY DESIGN

Case report and literature review.

OBJECTIVE

This article reports 2 cases in which the patients accepted revision surgery after cervical total disc arthroplasty (CTDA) because of iatrogenic neurological injury.

SUMMARY OF BACKGROUND DATA

CTDA has been increasingly investigated to treat cervical degenerative disc disease. However, there are limited reports focused on its complications, especially the neurological complications after the procedure.

METHODS

A 52-year-old man underwent total disc arthroplasty for C5-C6, but immediately after surgery, he experienced paralysis of his upper and lower limbs. Radiographical images indicated residual compression to the spinal cord in the level of C5-C6. Another patient, a 60-year-old man, underwent total disc arthroplasty for C4-C5. Afterward, he experienced severe neck pain and paralysis of upper and lower limbs. He was unresponsive to conservative treatments; thus, a laminectomy was performed 3 months later. However, little improvement was observed. Radiographical images indicated kyphosis and spinal cord compression at the level of C4-C5. Furthermore, both cases showed a high signal in the spinal cord by T2-weighted magnetic resonance image, suggestive of spinal cord injuries.

RESULTS

Revision surgeries were performed in both cases. Cervical implants were first removed by the anterior approach, and fusion was then performed after a complete decompression. Motor examination of the patient in case 1 showed grade 3 strength in both of his hands and feet 6 months after revision surgery. In case 2, the patient's severe neck pain was resolved at the early postoperative stage. Motor examination showed grade 1 strength in both of his hands and feet 3 months after revision surgery.

CONCLUSION

On the basis of presented cases and other reports, the surgical goals in these patients were prioritized as follows: (1) safe and adequate neurological decompression and (2) establishment and maintenance of cervical sagittal balance. Moreover, a criterion for selecting patients undergoing CTDA needs to be established in order to reduce the occurrence of neurological complications associated with the procedure.

Differences between 1- and 2-level cervical arthroplasty: more heterotopic ossification in 2-level disc replacement: Clinical article

OBJECT

The most currently accepted indication for cervical arthroplasty is 1- or 2-level degenerative disc disease (DDD) refractory to medical treatment. However, the randomized and controlled clinical trials by the US FDA investigational device exemption studies only compared cervical arthroplasty with anterior cervical discectomy and fusion for 1-level disease. Theoretically, 2-level cervical spondylosis usually implicates more advanced degeneration, whereas the 1-level DDD can be caused by merely a soft-disc herniation. This study aimed to investigate the differences between 1- and 2-level cervical arthroplasty.

METHODS

The authors analyzed data obtained in 87 consecutive patients who underwent 1- or 2-level cervical arthroplasty with Bryan disc. The patients were divided into the 1-level and the 2-level treatment groups. Clinical outcomes were measured using the visual analog scale (VAS) for the neck and arm pain and the Neck Disability Index (NDI), with a minimum follow-up of 30 months. Radiographic outcomes were evaluated on both radiographs and CT scans.

RESULTS

The study analyzed 98 levels of Bryan cervical arthroplasty in 70 patients (80.5%) who completed the evaluations in a mean follow-up period of 46.21 ± 9.85 months. There were 22 females (31.4%) and 48 males (68.6%), whose mean age was 46.57 ± 10.07 years at the time of surgery. The 1-level group had 42 patients (60.0%), while the 2-level group had 28 patients (40.0%). Patients in the 1-level group were younger than those in the 2-level group (mean 45.00 vs 48.93 years, p = 0.111 [not significant]). Proportional sex compositions and perioperative prescription of nonsteroidal antiinflammatory drugs were also similar in both groups (p = 0.227 and p = 1.000). The 2-level group had significantly greater EBL during surgery than the 1-level group (220.80 vs 111.89 ml, p = 0.024). Heterotopic ossification was identified more frequently in the 2-level group than the 1-level group (75.0% vs 40.5%, p = 0.009). Although most of the artificial discs remained mobile during the follow up, the 2-level group had fewer mobile discs (100% and 85.7%, p = 0.022) than the 1-level group. However, in both groups, the clinical outcomes measured by VAS for neck pain, VAS for arm pain, and NDI all significantly improved after surgery compared with that preoperatively, and there were no significant differences between the groups at any point of evaluation (that is, at 3, 6, 12, and 24 months after surgery).

CONCLUSIONS

Clinical outcomes of 1- and 2-level cervical arthroplasty were similar at 46 months after surgery, and patients in both groups had significantly improved compared with preoperative status. However, there was a significantly higher rate of heterotopic ossification formation and less mobility of the Bryan disc in patients who underwent 2-level arthroplasty. Although mobility to date has been maintained in the vast majority (94.3%) of patients, the long-term effects of heterotopic ossification warrant further investigation.

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

OBJECT

Cervical arthroplasty is a valid option for patients with single-level symptomatic cervical disc diseases causing neural tissue compression, but postoperative heterotopic ossification (HO) can limit the mobility of an artificial disc. In the present study the authors used CT scanning to assess HO formation, and they investigated differences in radiological and clinical outcomes in patients with either a soft-disc herniation or spondylosis who underwent cervical arthroplasty.

METHODS

Medical records, radiographs, and clinical evaluations of consecutive patients who underwent single-level cervical arthroplasty were reviewed. Arthroplasty was performed using the Bryan disc. The patients were divided into a soft-disc herniation group and a spondylosis group. Clinical outcomes were measured using the visual analog scale (VAS) for neck and arm pain and the Neck Disability Index (NDI), whereas HO grading was determined by studying CT scans. Radiological and clinical outcomes were analyzed, and the minimum follow-up duration was 24 months.

RESULTS

Forty-seven consecutive patients underwent a single-level cervical arthroplasty. Forty patients (85.1%) had complete radiological evaluations and clinical follow-up of more than 2 years. Patients were divided into 1 of 2 groups: soft-disc herniation (16 cases) and the spondylosis group (24 cases). Their mean age was 45.51 ± 11.12 years. Sixteen patients (40%) were female. Patients in the soft-disc herniation group were younger than those in the spondylosis group, but the difference was not statistically significant (42.88 vs 47.26, p = 0.227). The mean follow-up duration was 38.83 ± 9.74 months. Sex, estimated blood loss, implant size, and perioperative NSAID prescription were not significantly different between the groups (p = 0.792, 0.267, 0.581, and 1.000, respectively). The soft-disc herniation group had significantly less HO formation than the spondylosis group (1 HO [6.25%] vs 14 Hos [58.33%], p = 0.001). Almost all artificial discs in both groups remained mobile (100% and 95.8%, p = 0.408). The clinical outcomes were not significantly different between the groups at all postoperative time points of evaluation, and clinical improvements were also similar.

CONCLUSIONS

Clinical outcomes of single-level cervical arthroplasty for soft-disc herniation and spondylosis were similar 3 years after surgery. There was a significantly higher rate of HO formation in patients with spondylosis than in those with a soft-disc herniation. The mobility of the artificial disc is maintained, but the long-term effects of HO and its higher frequency in spondylotic cases warrant further investigation.

Prevalence of heterotopic ossification after cervical total disc arthroplasty: a meta-analysis

BACKGROUND

Heterotopic ossification (HO) is a well-known complication after total hip and knee arthroplasty. But limited studies have focused on prevalence of HO following cervical total disc arthroplasty (CTDA) and the published data show controversial results.

OBJECTIVE

The purpose of this review is to investigate the prevalence of HO following CTDA by meta-analysis.

METHODS

The literatures were collected from PubMed, Embase and Cochrane library by using keywords as ([disc or disk] and [arthroplasty or replacement]) and (HO or delayed fusion or spontaneous fusion). The original studies were eligible only if the prevalence of HO and of advanced HO (Grade 3-4 according to McAfee) were investigated. A meta-analysis was then performed on collected data. Statistical heterogeneity across the various trials was tested using Cochran's Q, statistic and in the case of heterogeneity a random effect model was used. Tests of publication bias and sensitivity analysis were also performed.

RESULTS

Our data showed that the pooled prevalence of HO was 44.6% (95% confidence interval (CI), 37.2-45.6%) 12 months after CTDA and 58.2% (95% CI, 29.7-86.8%) 24 months after CTDA, while the advanced HO was 11.1% (95% CI, 5.5-16.7%) and 16.7% (95% CI, 4.6-28.9%), respectively. A significant heterogeneity was obtained. There was no publication bias and individual study had no significant effect on the pooled prevalence estimate.

CONCLUSION

Higher prevalence of HO was observed following CTDA, although HO was reported to be unrelated to the clinical improvement. It suggests that cervical disc replacement should be performed cautiously before obtaining long-term supporting evidence.

LEVEL OF EVIDENCE

Prognostic level III.

Artificial cervical disc arthroplasty: a systematic review

STUDY DESIGN

Systematic Review.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

Clinical and radiological outcomes of modified techniques in Bryan cervical disc arthroplasty

Kyphosis may occur after arthroplasty as the result of the disc insertion angle and overmilling; however, few studies have described techniques to avoid these factors. We investigated whether modified techniques of Bryan cervical disc arthroplasty can prevent adverse outcomes. Twenty patients (control group) underwent surgery using techniques described in the Bryan disc product monograph (Medtronic Sofamor Danek, Minneapolis, MN, USA). Twenty-nine patients (investigation group) underwent surgery using a modified technique which included changes in disc insertion angle, reducing overmilling of the endplates, ensuring the anterior borders of the two halves of the prosthesis were at the same horizontal line, and accurately fitting the prosthesis. Disability and pain were assessed using self-administered questionnaires and the change in functional spinal unit (FSU) angle between the two groups was also compared. Both groups demonstrated statistically significant improvement compared with preoperative values for the following functional outcomes measures. The mean neck pain Visual Analog Scale (VAS) scores before surgery were 73.45 (control) and 74.53 (investigation); at the 2-year follow-up these scores were 22.1 and 14.79 (p=0.0013), respectively. After surgery, 14 of 20 patients in the control group developed a tendency toward kyphosis of the FSU in the neutral position (range=-9°-13°, mean=-1.1°±5.05). Conversely, none of the 29 patients in the investigation group developed kyphosis of the FSU in the neutral position (range=0-10°, mean=3.79°±2.90) (p=0.0007). There was no statistically significant difference between the groups regarding preoperative and postoperative scores with the exception of neck pain VAS and FSU angle changes. There were no intraoperative complications, vascular or neurologic complications, spontaneous fusions, or device failures or explantations.

Polymethylmethacrylate-assisted ventral discectomy: rate of pseudarthrosis and clinical outcome with a minimum follow-up of 5 years

Background

Polymethylmethacrylate (PMMA) assisted ventral discectomy has been criticized for high rates of graft migration and pseudarthrosis when compared with various other fusion procedures for the treatment of cervical degenerative disc disease (DDD), therefore rendering it not the preferred choice of treatment today. Recently however spine surgery has been developing towards preservation rather than restriction of motion, indicating that fusion might not be necessary for clinical success. This study presents a long term comparison of clinical and radiological data from patients with pseudarthrosis and solid arthrodesis after PMMA assisted ventral discectomy was performed.

Methods

From 1986 to 2004 416 patients underwent ventral discectomy and PMMA interposition for DDD. The clinical and radiological outcome was assessed for 50 of 127 eligible patients after a mean of 8.1 years. Based on postoperative radiographs the patients were dichotomized in those with a pseudarthrosis (group A) and those with solid arthrodesis (group B).

Results

Pseudarthrosis with movement of more than 2 of the operated segment was noted in 17 cases (group A). In 33 cases no movement of the vertebral segment could be detected (group B). The analysis of the clinical data assessed through the neck disability index (NDI), the visual analogue scale (VAS) of neck and arm pain and Odom's criteria did not show any significant differences between the groups.

Patients from group B showed a trend to higher adjacent segment degeneration (ASD) than group A (p = 0.06). This correlated with the age of the patients.

Conclusions

PMMA assisted discectomy shows a high rate of pseudarthrosis. But the clinical long-term success does not seem to be negatively affected by this.

Longitudinal prospective long-term radiographic follow-up after treatment of single-level cervical disk disease with the Bryan Cervical Disc

BACKGROUND

Many short- and intermediate-term radiological and clinical studies on cervical arthroplasty with the Bryan Cervical Disc have been published, providing, most of the time, satisfactory results.

OBJECTIVE

To prospectively assess the intermediate and long-term radiographic characteristics of disk replacement surgery with the Bryan Cervical Disc and to correlate these results with clinical outcome.

METHODS

Range of motion was measured with a validated tool. Intervertebral disk degeneration was assessed with a quantitative scoring system. Heterotopic ossification was evaluated with a previously published scoring system. Device stability was investigated by measuring subsidence and anteroposterior migration. General clinical patient outcome was assessed with the Odom classification system.

RESULTS

Eighty-nine patients were initially included in this prospective long-term study. One patient was reoperated on at the index level and 4 were reoperated on at an adjacent level; those patients were not further analyzed. The mobility at the treated level was preserved in > or = 85% of our cases. The insertion of the prosthesis did not lead to an increase in mobility at the adjacent levels. The degeneration score increased at both adjacent levels. Heterotopic ossification was present in 34% to 39% of the patients, depending on the follow-up point. No cases of anteroposterior migration or subsidence were found. More than 82% of all patients had a good to excellent clinical outcome in the long run.

CONCLUSION

The device maintains preoperative motion at the index and adjacent levels, seems to protect against acceleration of adjacent-level degeneration as seen after anterior cervical discectomy and fusion, and remains securely anchored in the adjacent bone mass in the long run. Heterotopic ossification was frequently seen. The vast majority of all patients had a good to excellent clinical outcome.

Heterotopic ossification after cervical total disc replacement: determination by CT and effects on clinical outcomes

OBJECT

Heterotopic ossification (HO) after cervical total disc replacement (TDR) has been reported to impede artificial disc motion. In all previously reported cases of HO, assessment was based on plain radiographs. The authors hypothesized that CT scan is a more sensitive and accurate detector. The aims of this study were to assess the actual incidence of HO and its effect on outcome in a cohort of patients undergoing cervical TDR with the Bryan disc and to compare HO detection by means of plain radiographs and CT.

METHODS

The authors retrospectively assessed data from medical records, radiological studies, and clinical evaluations of patients who underwent 1- or 2-level cervical TDR with the Bryan disc and were followed up for more than 12 months. The presence and grading of HO according to the McAfee classification were assessed by CT scan, and these findings were compared with findings on plain radiographs. Thirty-six patients (mean age 46.61 ± 7.24 years; range 29-60 years; 21 men and 15 women) who underwent Bryan TDR at 52 levels were included in the study. The mean duration of CT follow-up was 19.03 ± 4.64 months; the mean duration of clinical follow-up was 26.78 ± 7.20 months.

RESULTS

On the basis of CT, HO was identified in 18 (50%) of 36 patients and 25 (48.1%) of 52 levels treated. Grade 1 HO was present in 9 of the levels treated (17.3%), Grade 2 in 13 levels (25.0%), Grade 3 in 2 levels (3.8%), and Grade 4 in 1 level (1.9%). Nineteen (76%) of the 25 affected levels were in patients who had undergone 2-level TDR. There was no significant association with patient sex or disc pathology. There was a tendency for HO development among older patients, but this finding was not statistically significant (mean age 48.8 ± 6.8 in patients with HO vs 44.4 ± 7.2 in those without HO, p = 0.065). Although HO was found in 25 levels, 96.2% of the treated levels (50 of 52) had segmental range of motion on dynamic (flexion and extension) radiographs. The concordance between HO grading by CT and radiography was high, with an intraclass correlation coefficient of 0.822 (lower limit of 95% CI: 0.710, p < 0.001). Patients who had HO had the same clinical success rate as those who did not (94.4% vs 94.4%, p = 1.00). The visual analog scale scores for neck and arm pain were significantly improved in both the HO and the non-HO group.

CONCLUSIONS

The rate of HO detected by CT scan in this cohort of patients undergoing cervical TDR with a Bryan disc was 48.1% per level treated and 50% per patient with minimal limitation of segmental motion (96.2% of levels remained mobile), but plain radiograph is an acceptable detection tool. Two-level surgery has a higher risk of HO, although development of HO does not affect clinical outcome.

Bryan total disc arthroplasty: a replacement disc for cervical disc disease

Total disc arthroplasty is a new option in the treatment of cervical degenerative disc disease. Several types of cervical disc prostheses currently challenge the gold-standard discectomy and fusion procedures. This review describes the Bryan Cervical Disc System and presents the Bryan prosthesis, its indications, surgical technique, complications, and outcomes, as given in the literature.

The influence of the axial, antero-posterior and lateral positions of the center of rotation of a ball-and-socket disc prosthesis on the cervical spine biomechanics

BACKGROUND

Previous studies documented the importance of the positioning and the design parameters of the prosthesis in determining the biomechanics of the implanted spine. However, a comprehensive biomechanical evaluation of the significance of these parameters is still lacking. Therefore, the paper is aimed to the quantification of their influence on the flexibility of the implanted spine and the force transmitted through the facet joints.

METHODS

A finite element model of the C5-C6 spine unit including a ball-and-socket disc prosthesis was built. Three probabilistic variables were considered: the axial, antero-posterior and lateral positions of the center of rotation. Randomized input parameters were generated with the Monte Carlo method. Pure moments of 1.6 Nm in flexion, extension, lateral bending and axial rotation were imposed to the upper endplate of C5; 100 simulations were conducted for the each of the considered loading conditions.

FINDINGS

Axial position of the center of rotation influenced the spine flexibility in all loading conditions and the facet force in extension, lateral bending and axial rotation. The antero-posterior position was found to influence the spine flexibility in flexion and extension, and the facet force in lateral bending and axial rotation. The lateral position was not significant.

INTERPRETATION

The effects of the positioning of a cervical disc prosthesis were estimated. A wide range of mechanical behaviors can be obtained by the manufacturers by appropriately manipulating the position of the center of rotation. A proper positioning of the artificial disc during the surgery, in particular in the antero-posterior direction, was found to be of critical importance.

Complications of Bryan cervical disc replacement

The primary goals of cervical disc replacement are to avoid fusion in the affected segment, maintain the mobility and function of the involved cervical segments, allow patients to quickly return to routine activities and reduce or eliminate adjacent-segment disease. A large number of patients have already undergone, and more and more patients will in the future undergo, cervical disc replacement. The cervical device which best preserves movement, and has therefore been the device of choice, has been the Bryan cervical disc. Although a safe surgical technique has been demonstrated and favorable results of using the Bryan disc reported, some complications have also accompanied this arthroplasty. Complications of Bryan cervical disc replacement include those related to the operative approach and decompression process, loosening and failure of the device, postoperative kyphosis, heterotopic ossification, and loss of movement due to spontaneous fusion. In order to avoid these complications, strict patient selection criteria and a meticulous knowledge of anatomy are necessary.

A clinical analysis of 4- and 6-year follow-up results after cervical disc replacement surgery using the Bryan Cervical Disc Prosthesis

OBJECT

In this study, long-term results are presented from clinical studies of the Bryan Cervical Disc Prosthesis at University Hospital Gasthuisberg in Leuven, Belgium. A total of 98 patients (89 with 1-level and 9 with 2-level implantations) agreed to participate in follow-up studies for up to 10 years postoperatively. This article focuses on the 4- and 6-year results. Patients in one of the clinical studies had either radiculopathy or myelopathy associated with spondylosis and/or disc herniations that did not respond to conservative treatment. Patients from the other clinical study received commercially available Bryan devices and the study protocol did not have specific inclusion/exclusion criteria. More than 90% of the patients were considered to have radiculopathy.

METHODS

Clinical measurements discussed in the article include the 36-Item Short Form Health Survey, Neck Disability Index, numerical ratings of neck and arm pain, neurological outcomes, and Odom classification. Angular motion findings from lateral flexion-extension radiographs are also presented. The occurrence of adverse events and second surgeries are examined as an indicator of device safety.

RESULTS

The clinical outcomes at 4 and 6 years postoperatively appear consistent with the previously reported results at 1 and 2 years postoperatively. The mean angular motion results at 4 and 6 years postoperatively for 1-level patients were 7.3 and 7.7 degrees, respectively. Two-level patients had slightly less motion at 4 and 6 years postoperatively with mean caudad values of 5.7 and 6.0 degrees, respectively, and cephalad values of 4.2 and 6.2 degrees, respectively. Efforts were made to capture adverse events, regardless of their nature and relatedness to the study surgery. This effort resulted in a relatively high number of recorded events. However, only 6 patients experienced events that were judged by the investigator to be related, either possibly or definitely, to the Bryan device. These events included device migration, device removal, and hoarseness and vocal cord paralysis, as well as 3 cases involving pain and neurological symptoms. Eight patients underwent further neck surgery to treat symptoms.

CONCLUSIONS

The favorable clinical and angular motion outcomes that were previously noted at 1- and 2-years' follow-up after cervical disc replacement with the Bryan Cervical Disc Prosthesis appear to persist after 4 and 6 years of follow-up.

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

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

Delayed hyper-reactivity to metal ions after cervical disc arthroplasty: a case report and literature review

STUDY DESIGN

Anecdotal case report.

OBJECTIVE

To report a very interesting and perplexing complication of cervical total disc arthroplasty that has not been previously reported in literature.

SUMMARY OF BACKGROUND DATA

Although there has been increasing interest in the field of artificial disc replacement to treat cervical degenerative disc disease, not much has been mentioned in the literature about the potential complications of the disc itself. We encountered a delayed complication in 1 patient that has not been reported in the literature.

METHOD

Thirty-nine-year-old white woman received total disc arthroplasty for herniated intervertebral disc at C5-C6 level uneventfully. She had recurrence of symptoms 9 months after the procedure and failed to respond to conservative measurements. Imaging revealed soft tissue mass posterior to the implanted disc encroaching the spinal cord.

RESULTS

Surgical explantation and exploration of the disc space revealed thick layer of abnormal hyaline cartilaginous tissue with chronic inflammatory debris. The patient had complete resolution of symptoms after the revision surgery.

CONCLUSION

Although there is increased enthusiasm about motion preservation technology and disc replacement surgery for intervertebral disc herniation, unexpected complications like the present case need to be shared within the scientific community to better understand the risks associated with these new and promising devices.