Abstract
Study Design
Systematic Review.
Objectives
Cervical disc arthroplasty (CDA) is a motion-preserving alternative to fusion for degenerative cervical disc disease. Implant dislocation, though rare, can lead to severe complications. Despite growing CDA adoption, no systematic synthesis of dislocation risk factors exists, leaving clinicians without evidence-based guidelines. To our knowledge, our study is the first detailed systematic review on CDA-related implant migrations. Our study aims to synthesize literature on CDA-related migration, identify risk factors and evaluate overall management outcomes.
Methods
A structured literature review was conducted, identifying 16 relevant studies through PubMed. Data were extracted on study design, patient demographics, prosthesis type, migration direction and timing, risk factors, management approaches, and clinical outcomes.
Results
Among 40 dislocation cases, anterior migration predominated (70.0%), linked to trauma, hyperlordosis, or poor osseointegration. Posterior migration (17.5%) was associated with polyethylene wear or osteolysis. 5 cases were of unspecified direction (12.5%). 62.5% of the patients underwent revision surgery, with anterior cervical discectomy and fusion (ACDF) making up 88% of these revision surgeries. Two deaths occurred due to postoperative complications.
Conclusions
Careful patient selection, optimal implant sizing, and adherence to surgical technique are critical to minimizing dislocation. Surgeons should avoid CDA in kyphotic patients and consider constrained designs in high-risk cases. Early recognition and prompt surgical intervention lead to favourable outcomes.
Introduction
Cervical disc arthroplasty (CDA) is increasingly used as an alternative to fusion for cervical degenerative disc disease, offering motion preservation and reduced adjacent segment degeneration.1-16 CDA is a motion-preserving surgery that has been shown to improve clinical long-term outcomes, hence presenting itself as an alternative to fusion surgery.17-19 The preservation of segmental cervical range of motion prevents accelerated adjacent segment disease as compared to fusion surgeries. 20 Implant migration in CDA is generally defined as radiographically observed displacement of the prosthesis from its originally implanted position, with or without accompanying clinical symptoms while dislocations typically refer to a more substantial prosthesis displacement that generally leads to mechanical failure, loss of intended alignment, or the onset of clinical symptoms such as dysphagia or spinal cord compression resulting in neurological deficit, frequently necessitating surgical revision.2,9 Previous reports have highlighted varying mechanisms and risk factors contributing to implant migration, including surgical technique, implant design, and patient-specific factors.1-16 This systematic review aims to consolidate current literature on CDA-related implant migration, explore contributing factors, and offer actionable recommendations to mitigate the overall risk.
Methods
Literature Search
A systematic search of PubMed was performed in March 2025 following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) for articles containing the terms ‘cervical disc replacement’, ‘cervical disc arthroplasty’, ‘implant migration’ and ‘dislocation’. Studies were limited to those published within 15 years (2010 to present), written in English, involved human subjects, and reported clinical or radiological findings related to CDA implant migration or dislocations. Two authors screened through the initial yield of 240 articles, removing duplicates and then subsequently screening through the abstracts of the articles. The authors then performed a full-text review of 35 articles, further narrowing down to 16 studies (see Figure 1). Flow diagram of the literature search
Study Selection
Study Characteristics (Design, Prosthesis Type)
Data Extraction
Dislocation Outcomes (Direction, Risk Factors, Management)
Results
Quality Assessment of Included Studies
Prosthesis Type
Type of Prosthesis
Direction of Migrations
Anterior migration refers to forward displacement of the prosthesis towards the prevertebral soft tissues or oesophagus, whereas posterior migration denotes displacement into the spinal canal with potential neural compression. Figure 2 provides a schematic representation of these directions, while Figure 3 presents a lateral radiograph from an illustrative case of a Mobi-C anterior migration.
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The directional analysis of implant migrations revealed distinct patterns with important clinical implications (Table 5). Anterior migrations predominated, accounting for 28 cases (70.0%) of the total dislocations while posterior migrations accounted for 7 cases (17.5%) of the total dislocations. The clinical urgency of these cases was evident in the high revision rate, with 62.5% (25/40) requiring surgical intervention. The remaining 12.5% (n = 5) of dislocations with unspecified direction primarily derived from older studies with limited radiographic documentation and were successfully managed conservatively with favourable outcomes. Schematic illustration of anterior and posterior migration of a CDA implant Clinical radiograph showing anterior migration of a CDA implant, modified from Pelletier et al.
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. Direction of Implant Migration
Management of Migrations
Surgical Management of Implant Migration
Risk Factor Synthesis
Risk Factor Synthesis
Discussion
Implant migration following cervical disc arthroplasty is a multifactorial phenomenon. Anterior migrations were more prevalent and often related to biomechanical or technical issues. Posterior migrations, although less frequent, tended to present with more severe neurological compromise. The findings of this systematic review illuminate critical patterns in cervical disc arthroplasty (CDA) implant dislocations, with implications for surgical decision-making. This systematic review highlights two overarching themes in CDA dislocation: the importance of technical precision during surgery and the need for vigilant postoperative risk management.
Biomechanical Vulnerabilities and Technical Precision in Surgical Execution
Anterior migrations which accounted for 70.0% of cases were strongly associated with biomechanical overload— often from trauma, implant sizing errors or endplate compromise as seen in Table 6. These failures tend to cluster in early postoperative periods when osseointegration is incomplete. In contrast, posterior dislocations (17.5 %) typically resulted from late degenerative processes like polyethylene wear or osteolysis, often manifesting >9 months post-implantation.3,14 This temporal dichotomy underscores that anterior failures reflect acute mechanical factors, while posterior failures reflect chronic material limitations. However, it is worth noting that posterior migrations have been described to have a higher rate of mortality overall. 2 Particular caution is warranted for osteoporotic patients, given the established association between poor bone quality and late osteolysis-related failures. 14 Patients with existing segmental misalignments (kyphosis) should also be excluded from cervical disc arthroplasty to minimise the potential risk of disc migrations. 5 The single reported case of intra-prosthetic dislocation involved rupture of a Mobi-C polyethylene core at nine months post-implantation, highlighting possible material limitations. 3
Surgical technique emerges as a critical modifiable factor in dislocation prevention. Implant sizing proves particularly crucial as seen in the studies done by Pelletier and Ozbek et al. where undersized implants resulted in overloading and eventual implant migration.1,11 The prosthesis should cover the endplates of the vertebrae and midline positioning is key to minimise the risks of migration. This may be facilitated by pre-operative imaging such as computed tomography (CT) to enhance surgical planning.
Endplate preservation during surgical preparation represents another key consideration. Endplate destruction was noted in the case report by Zhai et al. which increased the possibility of implant migration. 8 The normal endplates function to prevent prosthesis migration, subsidence into the bone and fusion which may disrupt the prosthesis itself. 11 Thus, a broken endplate may result in higher incidence of implant migrations post-operatively. 11 As cervical disc arthroplasty becomes more popular, surgeons should carefully handle the endplate and choose appropriate implants. While ACDF was widely employed for most revision surgeries in the studies included in our study, we note that Zhai et al. proposed a single-level corpectomy with iliac bone graft for cases of endplate destruction of two vertebras, resulting in symptom resolution. 8
Managing Post-Operative Risk
The early postoperative period represents a particular window of vulnerability due to incomplete osseointegration. Even minor trauma or manoeuvres involving cervical hyperflexion or hyperextension may disrupt the bone-implant interface during this period. 10 Khan et al reported a notable case in 2020 where routine laryngoscopy just 30 days post-implantation displaced a well-positioned ProDisc-C prosthesis anteriorly by 8.5 mm 10 . Hence, special considerations should apply to airway management in the early post-operative period. For 10 months post-implantation, any required intubation should employ fibre-optic or video laryngoscopy with manual in-line stabilization to avoid displacing immature implants. 10 This case underscores how even relatively low-energy forces can disrupt the immature bone-implant interface before osseointegration completes.7,10 The initial 6-month osseointegration period demands vigilant monitoring. Routine radiographic surveillance at regular intervals is essential for early detection of asymptomatic migrations.5,7 Clinicians should maintain a high index of suspicion in patients presenting with new-onset dysphagia, neck pain, or neurologic symptoms, particularly after trauma with low threshold for immediate imaging given the potential for rapid neurological deterioration. 2 Conservative management may be appropriate for asymptomatic, non-progressive migrations, but symptomatic or unstable dislocations require prompt surgical intervention.
Study Limitations
We note several limitations in our manuscript. The majority of included studies were case reports or small retrospective series, limiting the generalizability of the findings. Additionally, heterogeneity in reporting migration direction, prosthesis types, and outcome measures complicates direct comparison across studies. There is also ambiguity on the exact definition of implant migration and dislocations, which could have precipitated the exclusion of more studies. A uniform radiological definition of migration or dislocation could not be consistently extracted due to heterogeneity in reporting thresholds. The absence of long-term data on newer implants also remains a critical gap that future prospective trials should address.
Conclusion
Cervical disc arthroplasty dislocation, although rare, follows distinct patterns shaped by surgical technique, implant design, and patient-specific risk factors. Anterior migrations are typically early mechanical failures linked to trauma, improper sizing and endplate violation, while posterior migrations tend to occur later due to material wear or osteolysis. Preoperative planning should include assessment for kyphotic alignment, osteoporosis, or other contraindications. Intraoperatively, meticulous sizing and preservation of endplate integrity are essential. Postoperatively, the early osseointegration window requires special care, including routine interval imaging and modified airway management where necessary. When implant dislocation occurs, early recognition and timely revision, most often with ACDF, are key to optimizing outcomes though asymptomatic patients without neurological deficits may be managed conservatively. These findings provide an evidence-based framework for reducing the risk of CDA implant migration and enhancing patient safety.
Footnotes
Author’s Contribution
AA was involved in study design, analyzing and interpreting study data and writing of the manuscript. SKD, LD, HLTT were involved in study design. CZ was involved in study concept, design, analyzing and interpreting study data and writing of the manuscript.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data Availability Statement
All data generated or analysed during this study are included in this published article