Midterm osteolysis-induced aseptic failure of the M6-C™ cervical total disc replacement secondary to polyethylene wear debris

Comparison of Revision Rates Among Patients Undergoing 2-Level ACDF, CDR, and Hybrid Constructs

STUDY DESIGN

Retrospective database study.

OBJECTIVE

Compare the revision rates of 2-level ACDF, CDR, and hybrid ACDF/CDR.

SUMMARY OF BACKGROUND DATA

While single-level CDR has been extensively studied, multilevel CDR and hybrid ACDF/CDR constructs have been less well studied.

METHODS

This study utilized a large commercial insurance database of patients 65 years old or younger. Patients undergoing 2-level ACDF, 2-level CDR, and hybrid 2-level ACDF/CDR were identified. Patients age 18 years or older with malignant, infectious, or neoplastic etiologies were excluded, as were those undergoing revision surgery or any concomitant posterior cervical surgery. Study follow-up was terminated at 5 years postoperatively. The primary outcome was revision surgery, including anterior and posterior decompression, fusion, and arthroplasty.

RESULTS

A total of 99,282 patients were included. The mean age was 51.3 years old (SD 8.1). The mean maximum follow-up was 2.1 years (SD 1.7). In all 3.2% (n=3197) underwent 2-level CDR, 0.5% (n=448) underwent hybrid 2-level ACDF/CDR, and 96.3% (n=95,637) underwent 2-level ACDF. At 5 years postoperatively, in Kaplan-Meier analysis, revision occurred in 10.0% of the CDR group, 12.4% of the hybrid group, and 10.0% of the ACDF group. In multivariable regression analysis, no significant differences in revision occurrence were observed between the CDR, hybrid, and ACDF groups (P<0.15 for all comparisons). In multivariable regression analysis stratified by plate versus stand-alone cage, patients with plated hybrid constructs had higher revision rates than those with both plated ACDF constructs (HR: 1.5, P=0.0387) and 2-level CDR (HR: 1.5, P=0.0477).

CONCLUSIONS

In this retrospective database study of patients 65 years old or younger undergoing 2-level anterior cervical surgery, there were no significant differences at 5-year follow-up in revision rates for patients undergoing 2-level CDR, 2-level ACDF, and hybrid ACDF/CDR surgeries. In subanalysis, patients specifically with a plated hybrid ACDF/CDR had a higher occurrence of revision versus those undergoing plated 2-level ACDF or 2-level CDR. Future multicenter, prospective research is necessary to further assess these findings.

Reoperation Strategy for Failure of Cervical Disc Arthroplasty at Index and Adjacent Levels

Cervical disc arthroplasty (CDA) is a motion-preserving alternative to anterior cervical discectomy and fusion (ACDF) for cervical degenerative disease, reducing adjacent segment degenerative disease (ASD). Despite its benefits, some patients experience CDA failure due to prosthesis-related complications, heterotopic ossification, segmental kyphosis, ASD, or facet joint degeneration, necessitating revision surgery. Reoperation strategies depend on the failure mechanism, instability, sagittal malalignment, and neural compression. Anterior revision is suited for prosthesis failure, recurrent disc herniation, or ASD, enabling prosthesis removal, decompression, and fusion. In select cases, reimplantation may restore motion. Posterior approaches are preferred for facet degeneration, multilevel stenosis, or posterior hypertrophy, with options including foraminotomy, laminoplasty, or laminectomy and fusion. Complex cases may require combined anterior and posterior surgery for optimal decompression and stability. This narrative review outlines revision strategies, emphasizing biomechanical assessment, radiographic evaluation, and patient-specific considerations. Despite surgical challenges, meticulous planning and execution can optimize outcomes.

Osteolysis after cervical disc arthroplasty with artificial cervical disc

PURPOSE

Cervical total disc arthroplasty (TDA) is a motion-preserving alternative to anterior cervical discectomy and fusion that has gained popularity among spine surgeons. Although generally effective, TDA has been associated with rare cases of progressive osteolysis, a complication whose natural history and impact on clinical outcomes are not well understood. This case report aims to present a case of progressive osteolysis following cervical TDA with the SpinalKinetics® M6-C Artificial Cervical Disc and to discuss the clinical approach and implications for patient management.

METHODS

We reviewed the clinical course of a patient who underwent cervical TDA with the SpinalKinetics® M6-C Artificial Cervical Disc and subsequently developed progressive osteolysis. The patient's symptoms, diagnostic findings, and treatment progression were documented, with a focus on the timing of symptom onset, imaging, and the therapeutic interventions applied.

RESULTS

The patient demonstrated a delayed onset of symptoms related to osteolysis, which was identified through CT imaging as a progressive complication. The slow progression of osteolysis in this case underscores the need for careful monitoring, as early symptoms may be subtle but can lead to significant clinical implications if unaddressed.

CONCLUSION

This case highlights the potential for progressive osteolysis as a complication following cervical TDA, emphasizing the importance of ongoing surveillance and increased awareness among spine surgeons. Early identification and monitoring of osteolysis may mitigate the risk of severe outcomes and guide timely intervention.

Device profile of the Mobi-C artificial cervical disc: an overview of its safety and efficacy

INTRODUCTION

The Mobi-C Cervical Disc Replacement is a motion preserving alternative to anterior cervical discectomy and fusion in properly indicated patients. In 2013, Mobi-C became the first cervical disc in the United States approved to treat more than one level of the cervical spine. The FDA determined Mobi-C to be statistically superior to fusion at two levels, based on the primary endpoint of a prospective, concurrently controlled and randomized multicenter clinical trial.

AREAS COVERED

The history of Mobi-C and cervical disc arthroplasty is discussed. The unique biomechanics and structure of Mobi-C, the clinical results, the long term follow-up, the disc's biomechanics, and cost-effectiveness research are described. The competitive landscape is overviewed.

EXPERT OPINION

The evidence in this article supports the use of the Mobi-C cervical disc prosthesis as a viable alternative to fusion surgery in selected patients. Mobi-C has a relatively long track record compared to most other cervical disc prostheses. Thus far, Mobi-C is a very good option for preserving cervical motion based on long term follow-up, for achieving favorable clinical outcomes, and for maintaining patient safety. The Mobi-C cervical disc prosthesis is generally viewed positively, supported by clinical experience and research findings.

Cervical Disk Arthroplasty: Updated Considerations of an Evolving Technology

For years, anterior cervical diskectomy and fusion has been considered the benchmark for patients with cervical radiculopathy/myelopathy. However, concerns regarding adjacent segment pathology have promoted the popularity of cervical disk arthroplasty (CDA) with its motion-preserving properties. To replicate the natural cervical disk's six degrees of freedom and compressibility in cervical spine implants, designers need to carefully consider the level of constraint for stability and material selection. Recent CDA designs have incorporated strategies to facilitate unrestricted or semirestricted motion, deploying various articulating components and materials with distinct wear and compressibility properties. To optimize outcomes, patient selection considering additional degeneration of the cervical spine is critical. Clinical long-term studies have been reported in industry-funded FDA investigational device exemption and nonindustry-funded data for one-level and two-level CDA. There are limited data available on three-level and four-level CDA. Adverse events such as heterotopic ossification, osteolysis, migration, subsidence, and failure have been described, where analysis from explanted devices yields insight into in vivo wear and impingement performance. CDA has shown short-term cost advantages, such as decreased procedural expenses. Nonetheless, long-term analysis is necessary to assess possible economic tradeoffs. Advancements in designs may lead to improved implant longevity while evidence-based decision making will guide and responsibly manage the rapid advancement in CDA technology.

Reasons for Revision Surgery After Cervical Disk Arthroplasty Based on Medical Device Reports Maintained by the US Food and Drug Administration

STUDY DESIGN

Retrospective database review.

OBJECTIVE

The aim of this study was to analyze revisions of CDAs reported to the MAUDE database.

SUMMARY OF BACKGROUND DATA

Cervical disk arthroplasty (CDA) has emerged as a motion-preserving alternative to anterior cervical discectomy and fusion (ACDF) for degenerative cervical disease, demonstrating comparable outcomes. Despite the availability of variable CDA designs, there is limited data on the specific complications of individual CDAs. The Drug Administration's Manufacturer and User Facility Device Experience (MAUDE) database has been used to systematically report complications associated with CDAs. However, data on specific reasons for CDA revision remains scarce. The purpose of this study is to compare common complications associated with revision for different CDAs.

METHODS

The MAUDE database was queried from January 2005 to September 2023, including all nine FDA-approved CDAs. The full-text reports of each complication were categorized based on whether revision surgery was performed, the complications and the type of CDA collected and compared.

RESULTS

A total of 678 revisions for nine CDAs were reported: Mobi-C (239), M6 (167), Prodisc-C (88), Prestige (60), PCM (44), Bryan (35), Secure (23), Simplify (21), and Discover (1). The top three complications associated with revision were migration (23.5%), neck pain (15.5%), and heterotopic ossification (6.6%). The most common complications per device were migration for Mobi-C (26.4%), Prodisc-C (21.3%), Prestige (24.6%), PCM (84.1%), Bryan (48.6%), Secure (30.4%), and Discover (100%). For M6, the most common complications associated with revision surgery were osteolysis (18.6%) and neck pain (18.6%), while neck pain (23.8%) was the most common for the Simplify.

CONCLUSIONS

The MAUDE database highlights complications related to CDA revision in which the primary complications consistently include implant migration, neck pain, and heterotopic ossification, varying in their rerelvance depending on the CDA.

LEVEL OF EVIDENCE

Level II.

Removals and Revisions of Cervical Total Disc Replacement Devices in a Consecutive Series of 1626 Patients Beginning With the First Case Experience in 2003

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The purpose of this study was to investigate the rate of cervical total disc replacement (TDR) device removal or revision.

BACKGROUND

Cervical TDR has gained acceptance as an alternative to anterior cervical discectomy and fusion in appropriately selected patients. There have been concerns over device safety, one measure of which is subsequent surgery related to device problems.

PATIENTS AND METHODS

A consecutive series of 1626 patients undergoing cervical TDR from 2003 to June 2021 were included, consisting of TDRs up to 3 levels and hybrids (TDR and fusion). TDR removal or revision surgeries and reasons for these surgeries, procedures performed, and duration from index procedure were recorded. Data were analyzed to determine the removal/revision rate and factors possibly related to these events.

RESULTS

There were 24 removals/revisions (1.48%) in the 1626 patients. Removal was performed in 23 cases (1.41%) and revision in 1 (0.06%). Among removal cases, anterior cervical discectomy and fusion was performed in 18 and TDR was replaced with another TDR in 5. Removals with fusion included 5 cases of osteolysis with/without Cutibacterium acnes , 4 device displacement/migration, 4 posterior spinal pathology, and one for each of the following: metal allergy, approach-related complications, malpositioning, subsidence, and hypermobility. The revision involved TDR repositioning 3 days after index surgery. There were 66 patients for whom a minimum of 10-year follow-up was confirmed, and none had removal/revision surgery 10 or more years after index surgery. There was no relationship between the occurrence of removal/revision and age, sex, body mass index, or physician experience (learning curve). The removal/revision rate was significantly higher in FDA trials versus postapproval (4.1% vs . 1.3%, P < 0.05).

CONCLUSION

In this large consecutive series of patients, 1.48% of cervical TDRs were removed/revised. The low rate of removals/revisions over a long period of time provides support for the devices' safety.

LEVEL OF EVIDENCE

Level IV.

Treatment of failed cervical total disc replacements in a series of 53 cases and description of a management strategy

PURPOSE

To describe modes of failure of cervical TDR, their related treatment strategies, and to describe a management strategy for the treatment of failed cervical TDR.

METHODS

This retrospective study was based on a consecutive series of 53 cervical TDR patients who underwent removal or revision surgery. Chart review was conducted to collect general descriptive data, reasons for TDR removal/revision, duration from index implantation to re-operation, and the subsequent procedure performed.

RESULTS

Among 53 patients, 36 underwent TDR removal and fusion, 16 underwent TDR removal and replacement with another TDR, and one patient's TDR was revised by repositioning. The mean duration from index surgery to removal/revision was 40.1 months (range: 3 days-222 months). In all cases, removal/revision surgery was completed without complication. The most common reason for removal was severe osteolysis, often involving C. acnes infection, and was primarily associated with one implant type. TDR removal and fusion were performed for subsidence, device migration, treatment of symptoms arising from posterior anatomy (facet joints, etc.), approach-related complications and pain. TDR replacement was feasible for hypermobility, metal allergy, implant locked in kyphosis, and oversized implant use. In one case of TDR malpositioning, the device was successfully revised into appropriate position.

CONCLUSION

After cervical TDR failure, replacing a TDR with another implant can be feasible. Reasons for revision or removal after cervical TDR surgery include biomechanical failure, implant migration, surgeon or technical error, or biological reasons. The type of failure can help the surgeon create a strategy to address these complications.

One-Pot Construction of Articular Cartilage-Like Hydrogel Coating for Durable Aqueous Lubrication

Articular cartilage has an appropriate multilayer structure and superior tribological properties and provides a structural paradigm for design of lubricating materials. However, mimicking articular cartilage traits on prosthetic materials with durable lubrication remains a huge challenge. Herein, an ingenious three-in-one strategy is developed for constructing an articular cartilage-like bilayer hydrogel coating on the surface of ultra-high molecular weight polyethylene (BH-UPE), which makes full use of conceptions of interfacial interlinking, high-entanglement crosslinking, and interface-modulated polymerization. The hydrogel coating is tightly interlinked with UPE substrate through hydrogel-UPE interchain entanglement and bonding. The hydrogel chains are highly entangled with each other to form a dense tough layer with negligible hysteresis for load-bearing by reducing the amounts of crosslinker and hydrophilic initiator to p.p.m. levels. Meanwhile, the polymerization of monomers in the top surface region is suppressed via interface-modulated polymerization, thus introducing a porous surface for effective aqueous lubrication. As a result, BH-UPE exhibits an ultralow friction coefficient of 0.0048 during 10 000 cycles under a load of 0.9 MPa, demonstrating great potential as an advanced bearing material for disc prosthesis. This work may provide a new way to build stable bilayer coatings and have important implications for development of biological lubricating materials.

Proposal for a classification system of radiographic bone changes after cervical disc replacement

BACKGROUND

The goal of this study is to propose a classification system with a common nomenclature for radiographic observations of periprosthetic bone changes following cTDR.

METHODS

Aided by serial plain radiographs from recent cTDR cases (34 patients; 44 devices), a panel of experts assembled for the purpose of creating a classification system to aid in reproducibly and accurately identifying bony changes and assessing cTDR radiographic appearance. Subdividing the superior and inferior vertebral bodies into 3 equal sections, observed bone loss such as endplate rounding, cystic erosion adjacent to the endplate, and cystic erosion not adjacent to the endplate, is recorded. Determining if bone loss is progressive, based on serial radiographs, and estimating severity of bone loss (measured by the percentage of end plate involved) is recorded. Additional relevant bony changes and device observations include radiolucent lines, heterotopic ossification, vertebral body olisthesis, loss of core implant height, and presence of device migration, and subsidence.

RESULTS

Serial radiographs from 19 patients (25 devices) implanted with a variety of cTDR designs were assessed by 6 investigators including clinicians and scientists experienced in cTDR or appendicular skeleton joint replacement. The overall agreement of assessments ranged from 49.9% (95% bootstrap confidence interval 45.1-73.1%) to 94.7% (95% CI 86.9-100.0%). There was reasonable agreement on the presence or absence of bone loss or radiolucencies (range: 58.4% (95% CI 51.5-82.7%) to 94.7% (95% CI 86.9-100.0%), as well as in the progression of radiolucent lines (82.9% (95% CI 74.4-96.5%)).

CONCLUSIONS

The novel classification system proposed demonstrated good concordance among experienced investigators in this field and represents a useful advancement for improving reporting in cTDR studies.

Heterotopic ossification, osteolysis and implant failure following cervical total disc replacement with the M6-C™ artificial disc

INTRODUCTION

A recent study reported a 34% mid-term revision rate after M6-C™ cervical total disc replacement (CTDR) for wear-related osteolysis. Here, we aim to investigate the prevalence, risk factors, and radiographic characteristics of periprosthetic bony changes and implant failure of the M6-C™ artificial disc.

METHODS

We retrospectively analysed radiographic (conventional X-ray, CT scan) and clinical outcomes (EQ-5D-5L, Neck Disability Index (NDI), and Visual Analog Scale (VAS) for neck and arm pain) data collected during routine follow-up of patients who underwent CTDR with the M6-C™ between 2011 and 2015.

RESULTS

In total, 85 patients underwent CTDR with the M6-C™. Follow-up data were available for 43 patients (54% female, mean age 44 years) with 50 implants and a mean follow-up of 8.1 years (6.5-11 years). Implant failure with the presence of severe osteolysis was identified in 5 (12%) patients who were all male (p = 0.016) and implanted at the C5/6 level (p = 0.11). All failed implants required revision surgery. The overall prevalence of osteolysis was 44% (22/50 implants) and 34% (17/50 implants) for significant heterotopic ossification. Patients with high-grade osteolysis showed higher VAS arm pain (p = 0.05) and lower EQ-5D-VAS health VAS (p = 0.03).

CONCLUSION

We report a lower reoperation rate for failed M6-C™ implants than previously published, but confirmed that osteolysis and heterotopic ossification are common following CTDR with the M6-C™ and may be asymptomatic. Therefore, we strongly recommend ongoing clinical and radiographic monitoring after CTDR with the M6-C™, particularly for male patients implanted at the C5/6 level.

Prospective, multicenter clinical trial comparing the M6-C compressible cervical disc with anterior cervical discectomy and fusion for the treatment of single-level degenerative cervical radiculopathy: 5-year results of an FDA investigational device exemption study

BACKGROUND CONTEXT

Various total disc replacement (TDR) designs have been compared to anterior cervical discectomy and fusion (ACDF) with favorable short and long-term outcomes in FDA-approved investigational device exemption (IDE) trials. The unique design of M6-C, with a compressible viscoelastic nuclear core and an annular structure, has previously demonstrated favorable clinical outcomes through 24 months.

PURPOSE

To evaluate the long-term safety and effectiveness of the M6-C compressible artificial cervical disc and compare to ACDF at 5 years.

STUDY DESIGN

Prospective, multicenter, concurrently and historically controlled, FDA-approved IDE clinical trial.

PATIENT SAMPLE

Subjects with one-level symptomatic degenerative cervical radiculopathy were enrolled and received M6-C (n=160) or ACDF (n=189) treatment as part of the IDE study. Safety outcomes were evaluated at 5 years for all subjects. The primary effectiveness endpoint was available at 5 years for 113 M6-C subjects and 106 ACDF controls.

OUTCOME MEASURES

The primary endpoint of this analysis was composite clinical success (CCS) at 60 months. Secondary endpoints were function and pain (neck disability index, VAS), physical quality of life (SF-36, SF-12), safety, neurologic, and radiographic assessments.

METHODS

Propensity score subclassification was used to control for selection bias and match baseline covariates of the control group to the M6-C subjects. Sixty-month CCS rates were estimated for each treatment group using a generalized linear model controlling for propensity score.

RESULTS

At 5 years postoperatively, the M6-C treatment resulted in 82.3% CCS while the ACDF group showed 67.0% CCS (superiority p=.013). Secondary endpoints indicated that significantly more M6-C subjects achieved VAS neck and arm pain improvements and showed maintained or improved physical functioning on quality-of-life measures compared to baseline assessments. The M6-C group-maintained flexion-extension motion, with significantly greater increases from baseline disc height and disc angle than observed in the control group. The rates of M6-C subsequent surgical interventions (SSI; 3.1%) and definitely device- or procedure-related serious adverse events (SAE failure; 3.1%) were similar to ACDF rates (SSI=5.3%, SAE failure=4.8%; p>.05 for both).

CONCLUSIONS

Subjects treated with the M6-C artificial disc demonstrated superior 5-year achievement of clinical success when compared to ACDF controls. In addition, significantly more subjects in the M6-C group showed improved pain and physical functioning scores than observed in ACDF subjects, with no difference in reoperation rates or safety outcomes.

20-year Clinical Outcomes of Cervical Disk Arthroplasty: A Prospective, Randomized, Controlled Trial

STUDY DESIGN

Prospective, randomized, controlled trial.

OBJECTIVE

To compare clinical outcomes of anterior cervical discectomy and fusion (ACDF) and cervical disk arthroplasty (CDA) at 20 years.

SUMMARY OF BACKGROUND DATA

Concern for adjacent-level disease after ACDF prompted the development of CDA.

MATERIALS AND METHODS

Forty-seven patients with single-level cervical radiculopathy were randomized to either BRYAN CDA or ACDF for a Food and Drug Administration Investigational Device Exemption trial. At 20 years, patient-reported outcomes, including visual analog scales (VAS) for neck and arm pain, neck disability index (NDI), and reoperation rates, were analyzed.

RESULTS

Follow-up rate was 91.3%. Both groups showed significantly better NDI, VAS arm pain, and VAS neck pain scores at 20 years versus preoperative scores. Comparing CDA versus ACDF, there was no difference at 20 years in mean scores for NDI [11.1 (SD 14.1) vs. 19.9 (SD 17.2), P =0.087], mean VAS arm pain [0.9 (SD 2.4) vs. 2.3 (SD 2.8), P =0.095], or mean VAS neck pain [1.2 (SD 2.5) vs. 2.9 (3.3), P =0.073]. There was a significant difference between CDA versus ACDF groups in the change in VAS neck pain score between 10 and 20 years [respectively, -0.4 (SD 2.5) vs. 1.5 (SD 2.5), P =0.030]. Reoperations were reported in 41.7% of ACDF patients and 10.0% of CDA patients ( P =0.039).

CONCLUSIONS

Both CDA and ACDF are effective in treating cervical radiculopathy with sustained improvement in NDI, VAS neck and VAS arm pain at 20 years. CDA demonstrates lower reoperation rates than ACDF. There were no failures of the arthroplasty device requiring reoperation at the index level. The symptomatic nonunion rate of ACDF was 4.2% at 20 years. Despite a higher reoperation rate in the CDA group versus ACDF group, there was no difference in the 20-year NDI, VAS Neck, and VAS arm pain scores.

Biomechanics of Cervical Disk Replacement: Classifying Arthroplasty Implants

Cervical disk arthroplasty has been employed with increased frequency over the past 2 decades as a motion-preserving alternative to anterior cervical discectomy and fusion in select patients with myelopathy or radiculopathy secondary to degenerative disk disease. As indications continue to expand, an understanding of cervical kinematics and materials science is helpful for optimal implant selection. Cervical disk arthroplasty implants can be classified according to the mode of articulation and df , articulation material, and endplate construction. The incorporation of translational and rotational df allows the implant to emulate the dynamic and coupled centers of movement in the cervical spine. Durable and low-friction interfaces at the articulation sustain optimal performance and minimize particulate-induced tissue reactions. Endplate materials must facilitate osseous integration to ensure implant stability after primary fixation. These cardinal considerations underlie the design of the 9 implants currently approved by the FDA and serve as the foundation for further biomimetic research and development.

In Vitro Wear of a Novel Vitamin E Crosslinked Polyethylene Lumbar Total Joint Replacement

BACKGROUND

A novel, lumbar total joint replacement (TJR) design has been developed to treat degeneration across all three columns of the lumbar spine (anterior, middle, and posterior columns). Thus far, there has been no in vitro studies that establish the preclinical safety profile of the vitamin E-stabilized highly crosslinked polyethylene (VE-HXLPE) lumbar TJR relative to historical lumbar anterior disc replacement for the known risks of wear and impingement faced by all motion preserving designs for the lumbar spine.

QUESTIONS/PURPOSE

In this study we asked, (1) what is the wear performance of the VE-HXLPE lumbar TJR under ideal, clean conditions? (2) Is the wear performance of VE-HXLPE in lumbar TJR sensitive to more aggressive, abrasive conditions? (3) How does the VE-HXLPE lumbar TJR perform under impingement conditions?

METHOD

A lumbar TJR with bilateral VE-HXLPE superior bearings and CoCr inferior bearings was evaluated under clean, impingement, and abrasive conditions. Clean and abrasive testing were guided by ISO 18192-1 and impingement was assessed as per ASTM F3295. For abrasive testing, CoCr components were scratched to simulate in vivo abrasion. The devices were tested for 10 million cycles (MC) under clean conditions, 5 MC under abrasion, and 1 MC under impingement.

RESULT

Wear rates under clean and abrasive conditions were 1.2 ± 0.5 and 1.1 ± 0.6 mg/MC, respectively. The VE-HXLPE components demonstrated evidence of burnishing and multidirectional microscratching consistent with microabrasive conditions with the cobalt chromium spherical counterfaces. Under impingement, the wear rates ranged between 1.7 ± 1.1 (smallest size) and 3.9 ± 1.1 mg/MC (largest size). No functional or mechanical failure was observed across any of the wear modes.

CONCLUSIONS

Overall, we found that that a VE-HXLPE-on-CoCr lumbar total joint replacement design met or exceeded the benchmarks established by traditional anterior disc replacements, with wear rates previously reported in the literature ranging between 1 and 15 mg/MC.

CLINICAL RELEVANCE

The potential clinical benefits of this novel TJR design, which avoids long-term facet complications through facet removal with a posterior approach, were found to be balanced by the in vitro tribological performance of the VE-HXLPE bearings. Our encouraging in vitro findings have supported initiating an FDA-regulated clinical trial for the design which is currently under way.

The Role of Cervical Disc Arthroplasty in Elite Athletes

PURPOSE OF REVIEW

Cervical disc arthroplasty (CDA) for the treatment of symptomatic cervical disc herniations (CDH) is a promising treatment for professional athletes. In recent years, a number of high-profile athletes have returned to professional play within three months after CDA, raising important questions about the potential of this procedure within this patient group. We provide the first comprehensive review of available literature for the safety and efficacy of CDA in professional contact sport athletes.

RECENT FINDINGS

CDA provides theoretical biomechanical advantages over anterior cervical discectomy and fusion (ACDF) and posterior foraminotomy (PF), as CDA is the only operation for treatment of CDH that provides neural decompression, stability and height restoration, with preserved range of motion. While the comparative long-term results from each procedure are unknown, CDA has provided encouraging promise in its use in professional contact athletes. We aim to aid ongoing discussions regarding the controversies in spine surgery for professional athletes by providing a scientific review of the available evidence-based literature involving cervical disc arthroplasty in this population. In general, we believe that CDA is a viable alternative to ACDF and PF for the contact professional athlete who requires full neck range of motion and desires an expedited return to play. For collision athletes, the short- and long-term safety and efficacy profile of this procedure is promising but still unclear.

A dynamic pedicle screw system using polyethylene insert for the lumbar spine

Rigid spinal fusion with instrumentation has been widely applied in treating degenerative spinal disorders and has shown excellent and stable surgical results. However, adjacent segment pathology or implants' loosening could be problematic due to the spine's segmental fusion. Therefore, this study verified a novel concept for posterior stabilization with polyethylene inserts inside a pedicle screw assembly using bone models. We observed that although the gripping capacity of the dynamic pedicle screw system using a tensile and compression tester was less than half that of the rigid pedicle screw system, the flexion-extension moment of the dynamic pedicle screws was significantly lower than that of the rigid pedicle screws. Furthermore, while the bending force of the rigid pedicle screw assembly increased linearly with an increase in the bending angle throughout the test, that of the dynamic pedicle screw assembly also increased linearly until a bending angle of 2.5° was reached. However, this angle decreased at a bending angle of more than 2.5°. Additionally, the fatigue test of 1.0 × 10⁶ cycles showed that the pull-out force of the dynamic pedicle screws from two different polyurethane foam blocks was significantly higher than that of the rigid pedicle screws. Therefore, based on our results, we propose that the device can be applied in clinical cases to reduce screw loosening and adjacent segment pathology.

Delayed Failure of M6-C Cervical Disc Arthroplasty After Conversion of Adjacent Cervical Disc Arthroplasty to Fusion: A Case Report

CASE

We present a delayed failure of an M6-C cervical disc arthroplasty after conversion of a subjacent failed cervical disc arthroplasty to fusion. The annular component had failed, and the core had been ejected. Histology demonstrated a giant cell reaction to polyethylene debris, and tissue cultures were positive for Cutibacterium acnes.

CONCLUSION

This is the first report of M6-C failure after conversion of an adjacent arthroplasty to fusion. A growing number of reports surrounding the M6-C failure rate and mechanisms raise concern about the device's durability and underscore the importance of routine clinical and radiographic surveillance for these patients.

Explant analysis of a Discocerv cervical disc: A case study for a ceramic-on-ceramic cervical disc

Explant analyses are key to better understanding the effectiveness of medical implants in replacing natural joints. For the first time, an explanted Discocerv cervical disc was examined. The implant utilised the articulation of a caudal zirconia cup (inferior component) and a cephalic alumina head (superior component). The articulating surface of the superior alumina head had an average surface roughness of 0.016 ± 0.003 μm (Sa) and the articulating surface of the inferior zirconia cup had an average surface roughness of 0.015 ± 0.002 μm (Sa). Both articulating surfaces had negative skewness, indicating the removal of local peaks. The difference between the average surface roughness of the components was not significant (p-value: 0.741). Dark grey marks were observed on both of the articulating surfaces, which were found to be adhered titanium debris that was generated due to component impingement. This titanium debris may explain the small amount of metallosis that was reported at explantation. Some transfer of zirconium to the alumina articulating surface was also seen.