Cervical Artificial Disc Replacement Research Articles

Advances in Cervical Artificial Disc Replacement for Cervical Spondylosis

Advances in Cervical Artificial Disc Replacement for Cervical Spondylosis

Comparison of the effects of different artificial discs on hybrid surgery: A finite element analysis.

In recent years, artificial cervical discs have been used in intervertebral disc replacement surgery and hybrid surgery (HS). The advantages and disadvantages of different artificial cervical discs in artificial cervical disc replacement surgery have been compared. However, few scholars have studied the biomechanical effects of various artificial disc prostheses on the human cervical spine in HS which include the Anterior Cervical Discectomy and Fusion (ACDF) and Cervical Disc Arthroplasty (CDA). This study compared the biomechanical behavior of Mobi-C and Prestige LP in the operative and adjacent segments during two-level hybrid surgery. A three-dimensional finite element model of C2-C7 was first established and validated. Subsequently, clinical surgery was then simulated to establish a surgical model of anterior cervical fusion at the C4-C5 level. Mobi-C and Prestige-LP artificial disc prostheses were implanted at the C5-C6 level to create two hybrid models. All finite element models were fixed on the lower endplate of the C7 vertebra and subjected to a load of 73.6 N and different directions of 1 Nm torque on the odontoid process of the C2 vertebra to simulate human flexion, extension, lateral bending, and axial rotation. This paper compares the ROM, intervertebral pressure, and facet joint force after hybrid surgery with the intact model. The results show that compared with Prestige LP, Mobi-C can improve ROM of the replacement segment and compensate for the intervertebral pressure of the adjacent segment more effectively, but the facet joint pressure of the replacement segment may be higher.

A New Method to Evaluate Pressure Distribution Using a 3D-Printed C2-C3 Cervical Spine Model with an Embedded Sensor Array

Cervical degenerative disc diseases such as myelopathy and radiculopathy often require conventional treatments like artificial cervical disc replacement or anterior cervical discectomy and fusion (ACDF). When designing a medical device, like the stand-alone cage, there are many design inputs to consider. However, the precise biomechanics of the force between the vertebrae and implanted devices under certain conditions require further investigation. In this study, a new method was developed to evaluate the pressure between the vertebrae and implanted devices by embedding a sensor array into a 3D-printed C2-C3 cervical spine. The 3D-printed cervical spine model was subjected to a range of axial loads while under flexion, extension, bending and compression conditions. Cables were used for the application of a preload and a robotic arm was used to recreate the natural spine motions (flexion, extension, and bending). To verify and predict the total pressure between the vertebrae and the implanted devices, a 3D finite element (FE) numerical mathematical model was developed. A preload was represented by applying 22 N of force on each of the anterior tubercles for the C2 vertebra. The results of this study suggest that the sensor is useful in identifying static pressure. The pressure with the robot arm was verified from the FE results under all conditions. This study indicates that the sensor array has promising potential to reduce the trial and error with implants for various surgical procedures, including multi-level artificial cervical disk replacement and ACDF, which may help clinicians to reduce pain, suffering, and costly follow-up procedures.

PP01 Health Technology Assessment Of Cervical Artificial Disc Replacement: Highlighting The Need For A Consistent International Approach

IntroductionCervical artificial disc replacement (C-ADR) is not a new technology but one that has seen many technological advances in the past 10 years. Indeed, a recent review described total disc arthroplasty as the most innovative development in the history of spinal surgery. The primary goals of C-ADR are to reduce or eliminate pain, and restore normal segmental motion. The aim of this analysis was to identify, extract and examine key health outcomes and economic data from published health technology assessment (HTA) reports on C-ADR, with the aim of understanding how the evolution of this technology has influenced assessments internationally.MethodsA comprehensive search of over 90 HTA organization websites and the INAHTA HTA database using key terms for C-ADR surgical procedures was coupled with a literature search of recent systematic reviews. No language restrictions were applied.ResultsTwenty HTA reports of C-ADR surgery published from 2005 to 2022 were included for review. Several HTAs (4/20) were updates or reassessments by the same agency and one was an update across agencies (Italy update of Belgian HTA). While many of the HTAs concluded C-ADR is as effective as standard care and superior in certain outcomes, there was no pattern or consistency in the conclusions or recommendations from these assessments, even as the evidence base expanded over time. Our analysis found this was largely due to variations in HTA approaches among agencies including: differences in research questions asked, PICO (Population, Intervention, Comparator, Outcomes) criteria and methods performed, such as: rapid versus full systematic reviews; inclusion of economic evaluations and/or budget impact analyses.Indeed, one of the only predictive factors for a positive HTA was a favorable cost-effectiveness analysis.ConclusionsC-ADR is an established technology with extensive HTA investigation internationally. The lack of a consistent approach taken by HTA bodies made prediction of successful HTA outcomes difficult. Future alignment of key evaluation processes and methods may help address current international variations and support consistent decision making on patient access.

Single-Level Cervical Artificial Disc Replacement Compared with Cage Screw Implants: 2-Year Clinical and Radiological Outcomes Especially Adjacent Level Ossification.

Retrospective single-center, single-surgeon cohort study. Our goal was to compare the 2-year clinical and radiological results of artificial disc replacement (ADR) and cage screw (CS) implants in patients with cervical degenerative disc disease (DDD). Anterior cervical discectomy and fusion with CS implants are an acceptable alternative to traditional cageplate construct due to perceived decreased complications of dysphagia. However, patients may experience adjacent segment disease because of increased motion and intradiscal pressure. ADR is an alternative to restore the physiological kinematics of the operated disc. Few studies directly compare ADR and CS construct for their efficacy. Patients who received single-level ADR or CS between January 2008 and December 2018 were included. Data collected was preoperatively, intraoperatively, and postoperatively (6, 12, 24 months). Demographic information, surgical information, complications, follow-up surgery, and outcome ratings (Japanese Orthopaedic Association [JOA], Neck Disability Index [NDI], Visual Analog Scale [VAS] neck and arm, 36-item Short Form Health Survey [SF-36], EuroQoL-5 Dimension [EQ-5D]) were gathered. The radiological assessment included motion segment height, adjacent disc height, lordosis, cervical lordosis, T1 slope, the sagittal vertical axis C2-7, and adjacent level ossification development (ALOD). Fifty-eight patients were included (ADR: 37 and CS: 21). At 6 months, both groups' JOA, VAS, NDI, SF-36, and EQ-5D scores significantly improved, and the positive trends persisted at 2 years. Noted no significant difference in the enhancement of clinical scores except for the VAS arm (ADR: 5.95 vs. CS: 3.43, p =0.001). Radiological parameters were comparable except for the progression of ALOD of the subjacent disc (ADR: 29.7% vs. CS: 66.9%, p =0.02). No significant difference in adverse events or severe complications seen. ADR and CS obtain good clinical results for symptomatic single-level cervical DDD. ADR demonstrated a significant advantage over CS in the improvement of VAS arm and reduced progression of ALOD of the adjacent lower disc. No statistically significant difference of dysphonia or dysphagia between the two groups were seen, attributed to their comparable zero profile.

Comparative analysis of clinical efficacy between posterior percutaneous endoscopic discectomy and anterior cervical discectomy and fusion in the treatment of cervical spondylotic radiculopathy

To explore the clinical efficacy of posterior percutaneous endoscopic discectomy(PPECD) in the treatment of cervical spondylotic radiculopathy. A total of 56 patiens with single segment cervical spondylotic radiculopathy from December 2017 to October 2020, were randomly divided into observation group and control group. In observation group, there were 16 males and 11 females, including 8 cases of C4,5, 13 cases of C5,6 and 6 cases of C6,7 performed posterior percutaneous endoscopic discectomy, aged from 34 to 61 years old with an average of (51.15±6.29) years old. In control group, there were 19 males and 10 females with single segment cervical spondylotic radiculopathy including 10 cases of C4,5, 14 cases of C5,6 and 5 cases of C6,7 performed anterior cervical discectomy and fusion, aged from 40 to 65 years old with an average of (53.24±5.31) years old. The operative time, intraoperative blood loss, postoperative time of lying in bed and length of postoperative hospital stay were recorded. Visual analogue scale(VAS) and neck disability index(NDI) were used to evaluate the clinical efficacy. Cervical plain films or MRIs, CTs were taken for re-visiting patients. All patients were followed up more than 2 years. The observation group patients were followed up, the duration ranged from 24 to 42 months with an average of (30.48±4.91) months. The control group patients were followed up, the duration ranged from 25 to 47 months, with an average of (32.76±4.53) months. Compared with control group, operative time, intraoperative blood loss, postoperative time of lying in bed and length of postoperative hospital stay were decreased(P<0.05). Compared with pre-operation, VAS of neck and upper limb and NDI at the latest follow-up between two groups were significantly improved(P<0.05). Compared with control group, VAS of neck and upper limb at 1 day after operation in observation group were significantly reduced(P<0.05). There was no significant difference in VAS of neck and upper limb and NID at 1, 3 months and the latest follow-up after operation between two groups(P>0.05). In the observation group, one patient's deltoid muscle strength was weakened to grade 4 after operation, and returned to normal after 12 weeks of conservative treatment. In control group, there was 1 case of postoperative adjacent spondylosis with symptoms of spinal compression after 2 years operation, then underwent cervical artificial intervertebral disc replacement. And there was 1 case of dysphagia after operation in control group and improved after 1 year. There was no significant difference in incidence of complications between two groups. PPECD has advantages of shortening operative time, decreasing intraoperative blood loss, reducing postoperative time of lying in bed and length of postoperative hospital stay. However, applicable age range of patients and long-term clinical efficacy needs further study.

Preparation and characterization of UHMWPE reinforced with polyester fibers for artificial cervical disc replacement (ACDR)

The purpose of this paper is to report on the preparation and improvement of a biocomposite material made from ultra-high molecular weight polyethylene for the replacement of natural discs. Such replacements are necessary due to intervertebral disc degradation as humans age, which can cause persistent pain due to nerve compression and high friction between vertebrae that can lead to vertebral corrosion. The material was shown to have excellent mechanical properties such as low coefficient of friction, and biocompatibility; however, it degraded with time due to wear failure. Moreover, The wear resistance was related to many factors, such as toughness. In the methodology of the current study, UHMWPE is reinforced with different percent of polyester (2, 4, 6, 8, 10%) to improve the mechanical properties of the polymer disc, thus enhancing its toughness and providing its high bearing ability for the load. The findings revealed that the tensile strength and modulus of elasticity improved by 43.415% and 34.286%, respectively, with the 6% polyester fibers due to the excellent entanglement between the matrix and reinforcing phase. The other mechanical properties, such as flexural strength and modulus, impact strength, fracture toughness, and compression strength, were also enhanced in this study. The highest value at 6% polyester fiber was found to be due to good bonding and adhesion between the polymer and polyester fibers. The Fourier Transformation Spectroscopy (FTIR) showed a shift on some peaks. The originality of this work is that the improvements due to the new bio-composite polymers for artificial implant cervical discs can open many applications in future for these materials.

Vertebral Artery Dissection Following Anterior Cervical Decompression and Artificial Disc Replacement

Vertebral artery dissection (VAD) is a rare vascular cause of acute stroke. Although VAD may be classified as spontaneous or traumatic, it is increasingly recognized that trivial mechanical stress typically precipitates this potentially dangerous condition. Herein, we report a rare case of VAD and acute stroke following anterior cervical decompression and artificial disc replacement (ADR). To our knowledge, there have been no other cases of acute vertebrobasilar stroke caused by VAD following anterior cervical decompression and ADR. This case highlights that, although rare, acute vertebrobasilar stroke may occur after the anterior cervical approach.

Cervical disc arthroplasty (CDA)/total disc replacement (TDR) vs. anterior cervical diskectomy/fusion (ACDF): A review.

We performed a focused review to determine the "non-inferiority", potential superiority, and relative safety/efficacy for performing cervical disc arthroplasty (CDA)/total disc replacement (TDR) in carefully selected patients vs. anterior cervical diskectomy/fusion (ACDF). Notably, CDA/TDR were devised to preserve adjacent level range of motion (ROM), reduce the incidence of adjacent segment degeneration (ASD), and the need for secondary ASD surgery. We compared the incidence of ASD, reoperations for ASD, safety/efficacy, and outcomes for cervical CDA/TDR vs. ACDF. Indications, based upon the North American Spine Society (NASS) Coverage Policy Recommendations (Cervical Artificial Disc Replacement Revised 11/2015 and other studies) included the presence of radiculopathy or myelopathy/myeloradiculopathy at 1-2 levels between C3-C7 with/without neck pain. Contraindications for CDA/TDR procedures as quoted from the NASS Recommendations (i.e. cited above) included the presence of; "Infection…", "Osteoporosis and Osteopenia", "Instability…", "Sensitivity or Allergy to Implant Materials", "Severe Spondylosis…", "Severe Facet Joint Arthropathy…", "Ankylosing Spondylitis" (AS), "Rheumatoid Arthritis (RA), Previous Fracture…", "Ossification of the Posterior Longitudinal Ligament (OPLL)", and "Malignancy…". Other sources also included spinal stenosis and scoliosis. Cervical CDA/TDR studies in the appropriately selected patient population showed no inferiority/ occasionally superiority, reduced the incidence of ASD/need for secondary ASD surgery, and demonstrated comparable safety/efficacy vs. ACDF. Cervical CDA/TDR studies performed in appropriately selected patients showed a "lack of inferiority", occasional superiority, a reduction in the incidence of ASD, and ASD reoperation rates, plus comparable safety/efficacy vs. ACDF.

Cervical subtotal discectomy prosthesis validated in non-human primate model: A novel artificial cervical disc replacement concept?

Objective: To evaluate the biological function of cervical subtotal discectomy prosthesis (CSDP) implantation in a non-human primate model. Methods: A CSDP was tested for cytocompatibility and osseointegration capacity before implantation in non-human primates. Subsequently, the CSDP was improved based on three-dimensional CT measurements of the non-human primate cervical spine. Eight cynomolgus monkeys were selected for removal of the intervertebral disc and lower endplate of the C5/6 segment to complete the model construction for CSDP implantation. In 18-month follow-up, physiological indices, radiology, and kinematics were assessed to estimate the biological function of the CSDP in non-human primates, including biosafety, osseointegration, and biomechanics. Results: Co-cultured with the CSDP constituent titanium alloy (Ti6Al4V-AO), the mouse embryo osteoblast precursor cell MC3T3-E1 obtained extended adhesion, remarkable viability status, and cell proliferation. After implantation in the mouse femur for 28 days, the surface of Ti6Al4V-AO was covered by a large amount of new cancellous bone, which formed further connections with the femur cortical bone, and no toxicity was detected by blood physiology indices or histopathology. After completing implantation in primate models, no infection or osteolysis was observed, nor was any subsidence or displacement of the CSDP observed in CT scans in the 18-month follow-up. In particular, the interior of the cervical vertebra fixation structure was gradually filled with new trabecular bone, and the CSDP had achieved fixation and bony fusion in the vertebral body at 1 year post-operation. Meanwhile, no signs of inflammation, spinal cord compression, adjacent segment degeneration, or force line changes were observed in subsequent MRI observations. Moreover, there were no pathological changes of the joint trajectory, joint motion range, stride length, or the stance phase ratio revealed in the kinematics analysis at 3, 6, 12, or 18 months after CSDP implantation. Conclusion: We successfully designed a new cervical subtotal discectomy prosthesis and constructed an excellent non-human primate implantation model for the evaluation of subtotal disc replacement arthroplasty. Furthermore, we demonstrated that CSDP had outstanding safety, osseointegration capacity, and biomechanical stability in a non-human primate model, which might be a new choice in the treatment of cervical disc diseases and potentially change future outcomes of degenerative cervical diseases.

Comparison of anterior cervical discectomy and fusion versus artificial disc replacement for cervical spondylotic myelopathy: a meta-analysis.

Anterior cervical discectomy and fusion (ACDF) has long been regarded as a gold standard in the treatment of cervical myelopathy. Subsequently, cervical artificial disc replacement (c-ADR) was developed and provides the advantage of motion preservation at the level of the intervertebral disc surgical site, which may also reduce stress at adjacent levels. The goal of this study was to compare clinical and functional outcomes in patients undergoing ACDF with those in patients undergoing c-ADR for cervical spondylotic myelopathy (CSM). A systematic literature review and meta-analysis were performed using the Embase, PubMed, and Cochrane Central Register of Controlled Trials databases from database inception to November 21, 2021. The authors compared Neck Disability Index (NDI), SF-36, and Japanese Orthopaedic Association (JOA) scores; complication rates; and reoperation rates for these two surgical procedures in CSM patients. The Mantel-Haenszel method and variance-weighted means were used to analyze outcomes after identifying articles that met study inclusion criteria. More surgical time was consumed in the c-ADR surgery (p = 0.04). Shorter hospital stays were noted in patients who had undergone c-ADR (p = 0.04). Patients who had undergone c-ADR tended to have better NDI scores (p = 0.02) and SF-36 scores (p = 0.001). Comparable outcomes in terms of JOA scores (p = 0.24) and neurological success rate (p = 0.12) were noted after the surgery. There was no significant between-group difference in the overall complication rates (c-ADR: 18% vs ACDF: 25%, p = 0.17). However, patients in the ACDF group had a higher reoperation rate than patients in the c-ADR group (4.6% vs 1.5%, p = 0.02). At the midterm follow-up after treatment of CSM, better functional outcomes as reflected by NDI and SF-36 scores were noted in the c-ADR group than those in the ACDF group. c-ADR had the advantage of retaining range of motion at the level of the intervertebral disc surgical site without causing more complications. A large sample size with long-term follow-up studies may be required to confirm these findings in the future.

Spinal Injuries in the Overhead Athlete.

Treatment of overhead athletes requires a systematic approach that will make an accurate diagnosis, deliver effective treatment, and make timely and safe return to sport. New data has shown success rates and return to play effectiveness after different types of cervical and lumbar surgery. Cervical foraminotomy has been shown to have the highest rate and fastest return to play, but with the highest incidence of need for revision surgery. Cervical artificial disc replacement has shown promising results in the general population and is being done more commonly in elite athletes, but has an unknown risk for failure. Cervical fusion is a well-established and effective treatment, but has the longest healing time and risk for adjacent level pathology. In the lumbar spine, discectomy has a long and proven track record, fusion is rarely performed but can be effective, and artificial disc replacement is extremely rare in an elite athlete. An effective and comprehensive approach can diagnose, treat, and return overhead athletes to competitive play.

Anterior Cervical Foraminotomy for Radiculopathy After Cervical Artificial Disc Replacement: Technique Description and Case Report.

Patients may occasionally have persistent or recurrent radicular symptoms after cervical artificial disc replacement (ADR) for cervical spondylotic radiculopathy. We describe our approach using anterior cervical foraminotomy (ACF) to provide symptom relief in such patients without the need to convert to a fusion or remove the ADR implant. Our operative technique for ACF after cervical ADR begins by starting at the lateral edge of the ADR at the superior end plate of the inferior vertebral body. The ipsilateral uncovertebral joint is drilled with a combination of a high-speed burr and diamond-coated burr to minimize the risk of injury to the vertebral artery. The neuroforamen is entered after drilling through the posterior aspect of the uncinate process. The exiting cervical nerve root should be directly visualized, and a Kerrison rongeur may be used to trace along the nerve root laterally to remove any remaining uncinate osteophyte or process. We queried our internal database for patients with recurrent or new radicular pain following cervical ADR who underwent ACF. Clinical characteristics and outcomes were reported. Five patients with recurrent radicular symptoms after ADR were reviewed. Two ACFs were performed at C5-6, and 2 were performed at C6-7. Four patients developed ipsilateral recurrent radicular symptoms, and only 1 patient developed contralateral new radicular symptoms. Three patients reported complete resolution of their new or recurrent radicular symptoms following ACF, and 2 patients reported only partial resolution. No patients required conversion to a fusion. In patients with recurrent symptoms of cervical spondylotic radiculopathy following ADR, ACF with uncovertebral joint resection can be used to provide direct foraminal decompression without the need for implant removal. This approach also preserves motion at the affected level, preserves cervical spinal stability, and prevents the need for spinal fusion. Patients with persistent or recurrent radicular symptoms after cervical ADR may achieve resolution of symptoms through a modified ACF technique.

Mid-long-term follow-up of operated level kinematics after single-level artificial cervical disc replacement with Bryan disc

ObjectiveEvaluation of the mid-long-term kinematics of single-level Bryan artificial cervical disc replacement (ACDR) in vivo by analyzing the center of rotation (COR) at the operated level.MethodsA retrospective analysis was conducted using data collected from 38 patients who underwent single-level Bryan ACDR from January 2010 to March 2013. Radiological parameters including range of motion (ROM), lordosis angle, translation, and COR were obtained. Clinical outcomes were assessed based on Odom Criteria, modified Japanese Orthopedic Association (mJOA), Neck Disability Index (NDI), and Visual Analogue Scale (VAS) scores. Correlations between COR and other follow-up data were discussed at the last follow-up.ResultsCompared with preoperative values, the last follow-up data showed that 86.84% of cases achieved good-or-excellent outcomes based on Odom criteria; Significant improvements were observed across all scales assessed for clinical outcomes (P < 0.05); Lordosis angle was significantly increased in both the overall cervical spine and the operated level (P < 0.05); ROM of the overall cervical spine, operated level, and adjacent levels was preserved (P > 0.05); There was no significant change in COR at the operated level (P > 0.05). At the last follow-up and at the operated level, COR (Y) showed negative correlations with ROM and translation (P < 0.05), but no follow-up data correlated with COR (X) were found (P > 0.05).ConclusionsSatisfactory clinical and radiological outcomes were achieved 7 years or more after single-level Bryan ACDR. At the operated level, preoperative COR was maintained, probably due to replicating the physiological interrelations of COR (Y), translation, and ROM.

Early efficacy of three dimensional printed anatomical biomimetic cervical artificial disc replacement in the treatment of cervical degenerative diseases

Objective: To investigate the efficacy and safety of a new cervical artificial disc prosthesis in the treatment of cervical degenerative diseases. Methods: The clinical data of 18 patients with single-level cervical degenerative diseases who underwent three dimensional printed anatomical bionic cervical disc replacement at Department of Spinal Surgery,Honghui Hospital,Xi'an Jiaotong University from May 2019 to July 2020 were analyzed retrospectively. There were 7 males and 11 females,aged (45±8) years old(range:28 to 58 years).The surgical segment was located at C3－4 level in 2 cases, C4－5 level in 5 cases, C5－6 level in 9 cases, and C6－7 level in 2 cases.The clinical and radiographic outcomes were recorded and compared at preoperative,postoperative times of one month and twelve months.The clinical assessments contained Japanese orthopedic association (JOA) score,neck disability index (NDI) and visual analogue scale (VAS).Imaging assessments included range of motion (ROM) of cervical spine, prosthesis subsidence and prosthesis anteroposterior migration.Repeated measurement variance analysis was used for comparison between groups,and paired t test was used for pairwise comparison. Results: All patients underwent the operation successfully and were followed up for more than 12 months.Compared with preoperative score,the JOA score,NDI and VAS were significantly improved after surgery (all P<0.01).There was no significant difference in postoperative ROM compared with 1-and 12-month preoperative ROM (t=1.570,P=0.135;t=1.744,P=0.099). The prosthesis subsidence was (0.29±0.13) mm (range: 0.18 to 0.50 mm) at 12-month postoperatively.The migration of prosthesis at 12-months postoperatively were (0.71±0.20) mm (range: 0.44 to 1.08 mm).There was no prosthesis subsidence or migration>2 mm at 12-month postoperatively. Conclusion: Three dimensional printed anatomical biomimetic cervical artificial disc replacement has a good early clinical effect in the treatment of cervical degenerative diseases, good mobility can be obtained while maintaining stability.

The development of artificial cervical disc replacement from the perspective of orthopedic bionic therapy

The modern surgical treatment of cervical degenerative disc disease can be traced back to the advent of anterior cervical decompression and fusion.With the emergence of fusion-related complications,different scholars have promoted the gradual transformation of cervical degenerative disc diseases from "fusion fixation" to "non-fusion reconstruction" through in-depth fusion with materials science,engineering mechanics and other disciplines.The innovation of this treatment concept is consistent with the original intention of "structural remodeling,functional reconstruction,maximum repair and reconstruction of the morphology and function of skeletal muscle system" in orthopedic bionic treatment,which is essentially in line with the "bionic alternative therapy" in orthopedic bionic therapy.This paper focuses on the surgical treatment of cervical degenerative disc diseases,reviews the development history of artificial cervical disc replacement,analyzes the evolution from orthopedic biomimetic therapy,and explores a new direction for the design of artificial cervical disc prostheses and the treatment of cervical degenerative disc diseases in the future.

A meta-analysis comparing the short- and mid- to long-term outcomes of artificial cervical disc replacement(ACDR) with anterior cervical discectomy and fusion (ACDF) for the treatment of cervical degenerative disc disease.

Anterior cervical discectomy and fusion (ACDF) surgery is commonly performed to treat cervical degenerative disc disease (CDDD). The lost of range of motion (ROM) is also found after ACDF, which contributes to degenerate in adjacent segment disease (ASD). Artificial cervical disc replacement (ACDR), an alternative to ACDF, is developed to preserve the ROM and reduce ASD. This article aims to compare the outcomes between ACDR and ACDF in the short-, mid-, and long-term. Databases including Cochrane, Embase, PubMed, and Web of Science were searched. Only RCTs were included in this meta-analysis, and the search strategy followed the requirements of the Cochrane Handbook. The strength of evidence was assessed using GRADE. Two reviewers independently assessed the methodological quality of each included study and extracted the relevant data. Thirty prospective RCTs were included. Prolonged operative duration, better overall success, neurological success, and NDI success rates were found in ACDR group in all follow-up periods, with lower dysphagia/dysphonia during short-term follow-up. Moreover, a lower ASD was found in ACDR group during long-term follow-up and overall analysis, with lower reoperation rates in all follow-up periods. Comparable length of hospital stay and blood loss were found in both groups. Moreover, ASD was similar in short- and mid-term follow-ups, while dysphagia/dysphonia incidence was similar in mid- and long-term follow-ups. The incidence of implant events was comparable in all follow-up periods (p > 0.05). ACDR is as effective as ACDF and superior for some success rates. Disc replacement can reduce the risk of dysphagia/dysphonia, ASD, and re-operation.

Segmental Motion of Cervical Arthroplasty Leads to Decreased Adjacent-Level Degeneration: Analysis of the 7-Year Postoperative Results of a Multicenter Randomized Controlled Trial.

Cervical artificial disc replacement (C-ADR) has become a common and accepted surgical treatment for many patients with cervical disc degeneration/herniation and radiculopathy who have failed nonoperative treatment. Midterm follow-up studies of the original investigational device exemption trials comparing C-ADR to traditional anterior cervical discectomy and fusion (ACDF) have revealed C-ADR patients have less adjacent-level disease and fewer reoperations at 5 to 7 years. The purpose of this study was to examine the relationship of radiographic adjacent-level disease (R-ALD) with the amount of index-level segmental range of motion (ROM) in C-ADR patients using the long-term follow-up data from the ProDisc-C investigational device exemption trial. This was a post hoc analysis of a 1:1 randomized controlled trial. The initial previously described Food and Drug Administration-approved 2-year study was extended, and consenting patients in the original study were followed at annual intervals up to 7 years. Logistic regression was used to assess any progression in adjacent-level disease (ALD). Ordinal logistic regression was also used to assess the relationship between any progressive R-ALD and final flexion extension (F/E) ROM in C-ADR patients. Spearman's rank-order correlation was used when R-ALD was kept as an ordinal variable to assess the same relationship. At the last follow-up visit, the rate of progressive R-ALD was significantly higher in ACDF patients than in C-ADR patients. When C-ADR patients were divided into 3 groups based on final F/E ROM, those with 0° to 3° (n = 19), 4° to 6° (n = 15), and 7° (n = 42) of segmental motion at the index procedure level, the rate of progressive R-ALD trended significantly with final ROM (P = 0.01). C-ADR leads to a significant decrease in R-ALD compared to ACDF. The difference in R-ALD is related to the preservation of motion at the index level and resultant preservation of kinematics and forces across the adjacent disc space.

Comparison of Radiographic Reconstruction and Clinical Improvement between Artificial Cervical Disc Replacement and Anterior Cervical Discectomy and Fusion.

Background The surgical management of cervical degenerative disc degeneration (CDDD) has not reached a consensus. Artificial cervical disc replacement (ACDR) has been shown to be efficient in reducing symptoms after CDDD, although the topic remains highly controversial in this field. This study aimed to evaluate the effectiveness of ACDR on the treatment of CDDD on the aspect of radiographic reconstruction and clinical improvement compared with anterior cervical discectomy and fusion (ACDF). Methods This was a retrospective comparative study with 47 patients who underwent single-level ACDR and 46 patients who underwent single-level ACDF. The radiographic reconstruction was assessed by the cervical sagittal alignment parameters, consisting of two aspects, distance and angle, such as cervical sagittal vertical axis (cSVA), cervical lordosis (CL), T1 slope (T1s), and intervertebral space height (ISH). The clinical improvement was assessed by patient-related outcomes (PROs), consisting of two aspects, relief of axial neck pain and recovery of cervical dysfunction, measured through the Visual Analogue Scale (VAS), Neck Disability Index (NDI), and Japanese Orthopedic Association (JOA). Results Significant variations were achieved on aspects of radiographic reconstruction and clinical improvement after ACDR (P < 0.05), which were similar to that of the ACDF group (P < 0.05). A significantly larger postoperative range of motion (ROM) was found in patients less than 45 years of age in the ACDR group (P < 0.05). In addition, a significantly better postoperative JOA was found in patients with a preoperative ISH less than 4 mm in the ACDF group than that in the ACDR group (P < 0.05). Other than that mentioned above, no significant variations in radiographic and clinical outcomes were found between the two groups (P > 0.05). Conclusions Overall, this study showed that a similar capability in terms of radiographic reconstruction and clinical improvement was found between the two methods. Specific concerns should be analyzed while choosing between an ACDR and an ACDF. It should be pointed out that, based on our experience, if the patient is younger, ACDR is recommended; for patients with preoperative ISH less than 4 mm, ACDF is more recommended.

Biomechanical Analysis of Cervical Artificial Disc Replacement Using Cervical Subtotal Discectomy Prosthesis.

Background: Anterior cervical discectomy and fusion (ACDF) sacrifices segmental mobility, which can lead to the acceleration of adjacent segment degeneration. The challenge has promoted cervical artificial disc replacement (CADR) as a substitute for ACDF. However, CADR has revealed a series of new issues that are not found in ACDF, such as hypermobility, subsidence, and wear phenomenon. This study designed a cervical subtotal discectomy prosthesis (CSDP) consisting of a cervical disc prosthesis structure (CDP structure), cervical vertebra fixation structure (CVF structure), link structure, and locking screw, aiming to facilitate motion control and reduce subsidence. The aim of this study was to assess the biomechanics of the CSDP using finite element (FE) analysis, friction-wear test, and non-human primates implantation study.Study Design: For the FE analysis, based on an intact FE C2-C7 spinal model, a CSDP was implanted at C5-C6 to establish the CSDP FE model and compare it with the Prestige LP prosthesis (Medtronic Sofamor Danek, Minneapolis, MN, United States). The range of motion (ROM), bone-implant interface stress, and facet joint force were calculated under flexion extension, lateral bending, and axial rotation. In addition, CSDP was elevated 1 mm to mimic an improper implantation technique to analyze the biomechanics of CSDP errors in the FE model. Moreover, the friction-wear test was conducted in vitro to research CSDP durability and observe surface wear morphology and total wear volume. Finally, the CSDP was implanted into non-human primates, and its properties were evaluated and verified by radiology.Results: In the FE analysis, the ROM of the CSDP FE model was close to that of the intact FE model in the operative and adjacent segments. In the operative segment, the CSDP error FE model increased ROM in flexion extension, lateral bending, and axial rotation. The maximum stress in the CSDP FE model was similar to that of the intact FE model and was located in the peripheral cortical bone region. The facet joint force changes were minimal in extension, lateral bending, and axial rotation loads in CSDP. In the friction-wear test, after the 150-W movement simulation, both the CVF-link-junction and the CDP-link-junction had slight wear. In the CSDP non-human primate implantation study, no subsidence, dislocation, or loosening was observed.Conclusion: In the FE analysis, the biomechanical parameters of the CSDP FE model were relatively close to those of the intact FE model when compared with the Prestige LP FE model. In terms of CSDP error FE models, we demonstrated that the implantation position influences CSDP performance, such as ROM, bone-implant interface stress, and facet joint force. In addition, we performed a friction-wear test on the CSDP to prove its durability. Finally, CSDP studies with non-human primates have shown that the CSDP is effective.