Biomechanical Analysis of Hybrid Artificial Discs or Zero-Profile Devices for Treating 1-Level Adjacent Segment Degeneration in ACDF Revision Surgery.

OBJECTIVE: Cervical hybrid surgery optimizes the use of cervical disc arthroplasty (CDA) and zero-profile (ZOP) devices in anterior cervical discectomy and fusion (ACDF) but lacks uniform combination and biomechanical standards, especially in revision surgery (RS). This study aimed to investigate the biomechanical characteristics of adjacent segments of the different hybrid RS constructs in ACDF RS. METHODS: An intact 3-dimensional finite element model generated a normal cervical spine (C2-T1). This model was modified to the primary C5-6 ACDF model. Three RS models were created to treat C4-5 adjacent segment degeneration through implanting cages plus plates (Cage-Cage), ZOP devices (ZOP-Cage), or Bryan discs (CDA-Cage). A 1.0-Nm moment was applied to the primary C5-6 ACDF model to generate total C2-T1 range of motions (ROMs). Subsequently, a displacement load was applied to all RS models to match the total C2-T1 ROMs of the primary ACDF model. RESULTS: The ZOP-Cage model showed lower biomechanical responses including ROM, intradiscal pressure, maximum von Mises stress in discs, and facet joint force in adjacent segments compared to the Cage-Cage model. The CDA-Cage model exhibited the lowest biomechanical responses and ROM ratio at adjacent segments among all RS models, closely approached or lower than those in the primary ACDF model in most motion directions. Additionally, the maximum von Mises stress on the C3-4 and C6-7 discs increased in the Cage-Cage and ZOP-Cage models but decreased in the CDA-Cage model when compared to the primary ACDF model. CONCLUSION: The CDA-Cage construct had the lowest biomechanical responses with minimal kinematic change of adjacent segments. ZOP-Cage is the next best choice, especially if CDA is not suitable. This study provides a biomechanical reference for clinical hybrid RS decision-making to reduce the risk of ASD recurrence.

Risk factors of bone loss after Prestige-LP cervical disc arthroplasty.

PURPOSE: Cervical disc arthroplasty (CDA) is widely employed for patients diagnosed with cervical degenerative disc disease (CDDD). Postoperative bone loss (BL) represents a radiological alteration that is a relatively novel consideration in the realm of CDA. This study endeavors to examine the risk factors associated with BL following CDA, aiming to elucidate the underlying mechanisms and the impact of BL on surgical outcomes. METHODS: A retrospective study was undertaken, encompassing consecutive patients subjected to one-level CDA, two-level CDA, or two-level hybrid surgery (HS) for the treatment of CDDD at our institution. Patient demographic and perioperative data were systematically recorded. Radiological images obtained preoperatively, at 1-week post-operation, and during the last follow-up were collected and evaluated, following with statistical analyses. RESULTS: A total of 295 patients and 351 arthroplasty segments were involved in this study. Univariate logistic regressions indicated that age ≥ 45 years and two-level HS was associated with lower risk of BL; and a greater ΔDA (change of disc angle before and after surgery) was correlated with an increased risk of BL. Multivariate logistic regression determined that two-level HS and greater ΔDA were independent preventative and risk factors for BL, respectively. Further analysis revealed that severe BL significantly elevated the risk of implant subsidence compared to non-BL and mild BL. CONCLUSIONS: This study posited bone remodeling and micromotion as potential underlying mechanisms of BL. Subsequent research endeavors should delve into the divergent mechanisms and progression observed between lower- and higher-grade BL, aiming to prevent potential adverse outcomes associated with severe BL.

Cervical Disc Arthroplasty (CDA) versus Anterior Cervical Discectomy and Fusion (ACDF) for Two-Level Cervical Disc Degenerative Disease: An Updated Systematic Review and Meta-Analysis.

Background: Anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) are both considered to be efficacious surgical procedures for treating cervical spondylosis in patients with or without compression myelopathy. This updated systematic review and meta-analysis aimed to compare the outcomes of these procedures for the treatment of cervical degenerative disc disease (DDD) at two contiguous levels. Methods: The PubMed, EMBASE, and Cochrane CENTRAL databases were searched up to 1 May 2023. Studies comparing the outcomes between CDA and ACDF in patients with two-level cervical DDD were eligible for inclusion. Primary outcomes were surgical success rates and secondary surgery rates. Secondary outcomes were scores on the Neck Disability Index (NDI) and Visual Analogue Scale (VAS) for neck and arm pain, as well as the Japanese Orthopaedic Association (JOA) score for the severity of cervical compression myelopathy and complication rates. Results: In total, eight studies (two RCTs, four retrospective studies, and two prospective studies) with a total of 1155 patients (CDA: 598; ACDF: 557) were included. Pooled results revealed that CDA was associated with a significantly higher overall success rate (OR, 2.710, 95% CI: 1.949-3.770) and lower secondary surgery rate (OR, 0.254, 95% CI: 0.169-0.382) compared to ACDF. In addition, complication rates were significantly lower in the CDA group than in the ACDF group (OR, 0.548, 95% CI: 0.326 to 0.919). CDA was also associated with significantly greater improvements in neck pain VAS than ACDF. No significant differences were found in improvements in the arm VAS, NDI, and JOA scores between the two procedures. Conclusions: CDA may provide better postoperative outcomes for surgical success, secondary surgery, pain reduction, and postoperative complications than ACDF for treating patients with two-level cervical DDD.

Does the novel artificial cervical joint complex resolve the conflict between stability and mobility after anterior cervical surgery? a finite element study.

Background and objective: Our group has developed a novel artificial cervical joint complex (ACJC) as a motion preservation instrument for cervical corpectomy procedures. Through finite element analysis (FEA), this study aims to assess this prosthesis's mobility and stability in the context of physiological reconstruction of the cervical spine. Materials and methods: A finite element (FE)model of the subaxial cervical spine (C3-C7) was established and validated. ACJC arthroplasty, anterior cervical corpectomy and fusion (ACCF), and two-level cervical disc arthroplasty (CDA) were performed at C4-C6. Range of motion (ROM), intervertebral disc pressure (IDP), facet joint stress (FJS), and maximum von Mises stress on the prosthesis and vertebrae during loading were compared. Results: Compared to the intact model, the ROM in all three surgical groups demonstrated a decline, with the ACCF group exhibiting the most significant mobility loss, and the highest compensatory motion in adjacent segments. ACJC and artificial cervical disc prosthesis (ACDP) well-preserved cervical mobility. In the ACCF model, IDP and FJS in adjacent segments increased notably, whereas the index segments experienced the most significant FJS elevation in the CDA model. The ROM, IDP, and FJS in both index and adjacent segments of the ACJC model were intermediate between the other two. Stress distribution of ACCF instruments and ACJC prosthesis during the loading process was more dispersed, resulting in less impact on the adjacent vertebrae than in the CDA model. Conclusion: The biomechanical properties of the novel ACJC were comparable to the ACCF in constructing postoperative stability and equally preserved physiological mobility of the cervical spine as CDA without much impact on adjacent segments and facet joints. Thus, the novel ACJC effectively balanced postoperative stability with cervical motion preservation.

Clinical Outcomes and Complication Rates for Noncontiguous Anterior Cervical Discectomy and Fusion, Cervical Disc Arthroplasty, and Hybrid Cervical Surgery: A Systematic Review.

OBJECTIVE: This study examined clinical outcomes associated with 3 types of noncontiguous cervical surgeries - anterior cervical discectomy and fusion (ACDF), cervical disc arthroplasty (CDA), and hybrid cervical surgery (HCS) - to improve surgeon decision-making. METHODS: A systematic review was performed using PubMed, CINAHL, MEDLINE, and Web of Science from database inception until June 6th, 2023. Inclusion criteria were studies that reported any type of clinical outcome, examined noncontiguous ACDF, noncontiguous CDA, and/or noncontiguous HCS. RESULTS: Ten articles out of 523 articles initially retrieved were included. Patients (n = 388) had a mean age of 52 ± 5.1 years and a mean follow-up time of 33 ± 6.0 months. Overall, 119 patients underwent noncontiguous HCS, 65 underwent noncontiguous CDA, and 204 underwent noncontiguous ACDF. There appears to be no clinically meaningful difference in Neck Disability Index score, Japanese Orthopedic Association score, and improvement in pain based on surgery type. There were a total of 83 complications (21% of cases) with noncontiguous ACDF having a higher absolute rate of dysphagia (20%) as compared to noncontiguous HCS (6.7%) or noncontiguous CDA (6.2%). Noncontiguous ACDF had a higher absolute rate of adjacent segment degeneration anterior cervical discectomy and fusion as a reported complication (6.4%) as compared to noncontiguous HCS (1.7%) and noncontiguous CDA (0.0%). CONCLUSIONS: There may be no clinically meaningful difference in many clinical outcomes for different noncontiguous surgical interventions for noncontiguous (cervical degenerative disc disease). However, complication rates, such as dysphagia and anterior cervical discectomy and fusion, appear higher for noncontiguous ACDF as compared to noncontiguous CDA or HCS.

Effect of device constraint: a comparative network meta-analysis of ACDF and cervical disc arthroplasty.

BACKGROUND CONTEXT: Clinical trials have demonstrated that cervical disc arthroplasty (CDA) is an effective and safe alternative treatment to anterior cervical discectomy and fusion (ACDF) for cervical degenerative disc disease in the appropriately indicated patient population. Various devices for CDA exist, differing in the level of device constraint. PURPOSE: To investigate outcomes following Anterior Cervical Discectomy and Fusion (ACDF) versus CDA stratified based on the level of device constraint: Constrained, Semiconstrained, and Unconstrained. STUDY DESIGN: Systematic review and network meta-analysis. PATIENT SAMPLE: 2,932 CDA patients (979 Constrained, 1,214 Semiconstrained, 739 Unconstrained) and 2,601 ACDF patients from 41 studies that compared outcomes of patients undergoing CDA or ACDF at a single level at a minimum of 2 years follow-up. OUTCOME MEASURES: Outcomes of interest included the development of adjacent segment degeneration (ASD), index and adjacent segment reoperation rates, range of motion (ROM), high-grade heterotopic ossification (HO, McAfee Grades 3/4), and patient-reported outcomes (NDI/VAS). METHODS: CDA devices were grouped based on the degrees of freedom (DoF) allowed by the device, as either Constrained (3 DoF), Semiconstrained (4 or 5 DoF), or Unconstrained (6 DoF). A random effects network meta-analysis was conducted using standardized mean differences (SMD) and log relative risk (RR) were used to analyze continuous and categorical data, respectively. RESULTS: Semiconstrained (p=.03) and Unconstrained CDA (p=.01) demonstrated a significantly lower risk for ASD than ACDF. All levels of CDA constraint demonstrated a significantly lower risk for subsequent adjacent segment surgery than ACDF (p<.001). Semiconstrained CDA also demonstrated a significantly lower risk for index level reoperation than both ACDF and Constrained CDA (p<.001). Unconstrained devices retained significantly greater ROM than both Constrained and Semiconstrained CDA (p<.001). As expected, all levels of device constraint retained significantly greater ROM than ACDF (p<.001). Constrained and Unconstrained devices both demonstrated significantly lower levels of disability on NDI than ACDF (p=.02). All levels of device constraint demonstrated significantly less neck pain than ACDF (p<.05), while Unconstrained CDA had significantly less arm pain than ACDF (p=.02) at final follow-up greater than 2 years. CONCLUSION: Cervical Disc Arthroplasty, particularly the unconstrained and semiconstrained designs, appears to be more effective than ACDF in reducing the risk of adjacent segment degeneration and the need for further surgeries, while also allowing for greater range of motion and better patient-reported outcomes. Less constrained CDA conferred a lower risk for index level reoperation, while also retaining more range of motion than more constrained devices.

The Fragility of Statistical Findings in Cervical Disc Arthroplasty: a Systematic Review of Randomized Controlled Trials.

PURPOSE: This study employs both the fragility index (FI) and fragility quotient (FQ) to assess the level of robustness in the cervical disc arthroplasty (CDA) literature. We hypothesize that dichotomous outcomes involving CDA would exhibit statistical vulnerability. METHODS: A PubMed search was conducted to evaluate dichotomous data for randomized controlled trials (RCTs) in CDA literature from 2000 to 2023. The FI of each outcome was calculated through the reversal of a single outcome event until significance was reversed. The FQ was calculated by dividing each fragility index by the study sample size. The interquartile range (IQR) was also calculated for the FI and FQ. RESULTS: Of the 1561 articles screened, 111 met the search criteria, with 35 RCTs evaluating CDA included for analysis. Six hundred and ninety-three outcome events with 130 significant (P < 0.05) outcomes and 563 nonsignificant (P ≥ 0.05) outcomes were identified. The overall FI and FQ for all 693 outcomes were 5 (IQR 3-7) and 0.019 (IQR 0.011-0.043). Fragility analysis of statistically significant outcomes and nonsignificant outcomes both revealed an FI of 5. All of the studies reported loss to follow-up (LTF) data where 65.7% (23) did not report or reported an LTF greater or equal to 5. CONCLUSIONS: The literature regarding CDA RCTs lacks statistical robustness and may misrepresent the conclusions with the sole use of the P value. By implementing the FI and FQ along with the P value, we believe the interpretation and contextualization of the clinical data surrounding CDA will be better understood.

Clinical and Radiological Outcomes of Cervical Disc Arthroplasty in Patients with Modic Change.

OBJECTIVE: Modic change (MC) is defined as abnormalities observed in the intervertebral disc subchondral and adjacent vertebral endplate subchondral bone changes. Most studies on MC were reported in the lumbar spine and associated with lower back pain. However, MC has been rarely reported in the cervical spine, let alone in those who underwent cervical disc replacement (CDR). This study aimed to focus on MC in the cervical spine and reveal clinical and radiological parameters, especially heterotopic ossification (HO), for patients who underwent CDR. Furthermore, we illustrated the association between MC and HO. METHODS: We retrospectively reviewed patients who underwent CDA from January 2008 to December 2019. The Japanese Orthopaedic Association (JOA), Neck Disability Index (NDI), and Visual Analog Scale (VAS) scores were used to evaluate the clinical outcomes. Radiological evaluations were used to conclude the cervical alignment (CL) and range of motion (ROM) of C2-7, functional spinal unit angle (FSUA), shell angle (SA), FSU height, and HO. Univariate and multivariate logistic regressions were performed to identify the risk factors for HO. The Kaplan-Meier (K-M) method was used to analyze potential risk factors, and multivariate Cox regression was used to identify independent risk factors. RESULTS: A total of 139 patients were evaluated, with a mean follow-up time of 46.53 ± 26.60 months. Forty-nine patients were assigned to the MC group and 90 to the non-MC group. The incidence of MC was 35.3%, with type 2 being the most common. Clinical outcomes (JOA, NDI, VAS) showed no significant difference between the two groups. The differences in C2-7 ROM between the two groups were not significant, while the differences in SA ROM and FSUA ROM were significantly higher in the non-MC than in the MC group (p < 0.05). Besides, FSU height in MC group was significantly lower than that in non-MC group. Parameters concerning CL, including C2-7, FSUA, SA, were not significantly different between the two groups. The incidence of HO and high-grade HO, respectively, in the MC group was 83.7% and 30.6%, while that in the non-MC group was 53.3% and 2.2%, and such differences were significant (p < 0.05). Multivariate logistic regression analyses and Cox regression showed that MC and involved level were significantly associated with HO occurrence (p < 0.05). No implant migration and secondary surgery were observed. CONCLUSION: MC mainly affected the incidence of HO. Preoperative MC was significantly associated with HO formation after CDR and should be identified as a potential risk factor for HO. Rigorous criteria for MC should be taken into consideration when selecting appropriate candidates for CDR.

Four-Level Cervical Disc Arthroplasty.

BACKGROUND: Multilevel anterior cervical discectomy and fusion inevitably yields a higher chance of pseudarthrosis or require more reoperations than single-level procedures. Therefore, multilevel cervical disc arthroplasty (CDA) could be an alternative surgery for cervical spondylosis, as it (particularly 3- and 4-level CDA) could preserve more functional motility than single-level disc diseases. This study aimed to investigate the clinical and radiological outcomes of 4-level CDA, a relatively infrequently indicated surgery. METHODS: The medical records of consecutive patients who underwent 4-level CDA were retrospectively reviewed. These highly selected patients typically had multilevel disc herniations with mild spondylosis. The inclusion criteria were symptomatic cervical spondylotic myelopathy, radiculopathy, or both, that were medically refractory. The clinical outcomes were assessed. The radiographic outcomes, including global and individual segmental range of motion (ROM) at C3-7, and any complications were also analyzed. RESULTS: Data from a total of 20 patients (mean age: 56 ± 8 years) with an average follow-up of 34 ± 20 months were analyzed. All patients reported improved clinical outcomes compared with that of preoperation, and the ROMs at C3-7 were not only preserved but also trended toward an increase (35 ± 8 vs 37 ± 10 degrees, pre- vs postoperation, P = 0.271) after the 4-level CDA. However, global cervical alignment remained unchanged. There was one permanent C5 radiculopathy, but no other neurological deteriorations or any reoperations occurred. CONCLUSION: For these rare but unique indications, 4-level CDA yielded clinical improvement and preserved segmental motility with low rates of complications. Four-level CDA is a safe and effective surgery, maintaining the ROM in patients with primarily disc herniations and mild spondylosis. CLINICAL RELEVANCE: For patients with mild spondylosis, whose degeneration at the cervical spine is not so severe, CDA is more suitable.

More anterior bone loss in middle vertebra after contiguous two-segment cervical disc arthroplasty.

BACKGROUND: Contiguous two-segment cervical disc arthroplasty (CDA) is safe and effective, while post-operative radiographic change is poorly understood. We aimed to clarify the morphological change of the three vertebral bodies operated on. METHODS: Patients admitted between 2015 and 2020 underwent contiguous two-level Prestige LP CDA were included. The follow-up was divided into immediate post-operation (≤ 1 week), early (≤ 6 months), and last follow-up (≥ 12 months). Clinical outcomes were measured by Japanese Orthopedic Association (JOA) score, visual analogue score (VAS), and neck disability index (NDI). Radiographic parameters on lateral radiographs included sagittal area, anterior-posterior diameters (superior, inferior endplate length, and waist length), and anterior and posterior heights. Sagittal parameters included disc angle, Cobb angle, range of motion, T1 slope, and C2-C7 sagittal vertical axis. Heterotopic ossification (HO) and anterior bone loss (ABL) were recorded. RESULTS: 78 patients were included. Clinical outcomes significantly improved. Of the three operation-related vertebrae, only middle vertebra decreased significantly in sagittal area at early follow-up. The four endplates that directly meet implants experienced significant early loss in length. Sagittal parameters were kept within an acceptable range. Both segments had a higher class of HO at last follow-up. More ABL happened to middle vertebra. The incidence and degree of ABL were higher for the endplates on middle vertebra only at early follow-up. CONCLUSION: Our findings indicated that after contiguous two-segment CDA, middle vertebra had a distinguishing morphological changing pattern that could be due to ABL, which deserves careful consideration before and during surgery.

Restoration of Range of Motion in the Cervical Spine through Single-Segment Artificial Disc Replacement Using the Baguera®C Prosthesis.

Background: Anterior cervical discectomy and fusion (ACDF) is a standard procedure for degenerative diseases of the cervical spine, providing nerve decompression and spinal stabilization. However, it limits cervical spine motility, restricts fused segment activity, and may lead to adjacent degeneration. Cervical disc arthroplasty (CDA) is an accepted alternative that preserves the structure and flexibility of the cervical spine. This study aimed to explore the dynamic changes in the range of motion (ROM) of the cervical spine after CDA using a viscoelastic artificial disc, as well as the factors affecting mobility restoration. Methods: A retrospective analysis was conducted on 132 patients who underwent single-level anterior cervical discectomy and CDA from January 2015 to June 2022. Result: Analysis of data from 132 patients revealed a significant improvement in clinical outcomes. The mean ROM of C2-C7 and functional spinal unit (FSU) segments significantly increased from 2 to 36 months post-operatively. Cervical spine flexibility was preserved and enhanced after prosthesis implantation. However, it took six months for the cervical spine motility to stabilize. In addition, sex and age were found to impact motility restoration, with female and younger patients exhibiting larger ROMs post-surgery. Additionally, CDA at the C5-C6 level resulted in the greatest increase in ROM, potentially improving overall kinematic ability. Conclusions: Single-segment artificial disc arthroplasty effectively restores the ROM in degenerative cervical spine conditions.

Segment selection for fusion and artificial disc replacement in the hybrid surgical treatment of noncontiguous cervical spondylosis: a finite element analysis.

Introduction: The treatment of skip-level cervical degenerative disease (CDD) with no degenerative changes observed in the intervening segment (IS) is complicated. This research aims to provide a reference basis for selecting treatment approaches for noncontiguous CDD. Methods: To establish accurate finite element models (FEMs), this study included computed tomography (CT) data from 21 patients with CDD (10 males and 11 females) for modeling. The study primarily discusses four cross-segment surgical approaches: upper (C3/4) anterior cervical discectomy and fusion (ACDF) and lower (C5/6) cervical disc arthroplasty (CDA), FA model; upper CDA (C3/4) and lower ACDF (C5/6), AF model; upper ACDF (C3/4) and lower ACDF (C5/6), FF model; upper CDA (C3/4) and lower CDA (C5/6), AA model. An initial axial load of 73.6 N was applied at the motion center using the follower load technique. A moment of 1.0 Nm was applied at the center of the C2 vertebra to simulate the overall motion of the model. The statistical analysis was conducted using STATA version 14.0. Statistical significance was defined as a p value less than 0.05. Results: The AA group had significantly greater ROM in flexion and axial rotation in other segments compared to the FA group (p < 0.05). The FA group consistently exhibited higher average intervertebral disc pressure in C2/3 during all motions compared to the AF group (p < 0.001); however, the FA group displayed lower average intervertebral disc pressure in C6/7 during all motions (p < 0.05). The AA group had lower facet joint contact stresses during extension in all segments compared to the AF group (p < 0.05). The FA group exhibited significantly higher facet joint contact stresses during extension in C2/3 (p < 0.001) and C6/7 (p < 0.001) compared to the AF group. Discussion: The use of skip-level CDA is recommended for the treatment of non-contiguous CDD. The FA construct shows superior biomechanical performance compared to the AF construct.

Incidence and risk factors of heterotopic ossification after cervical Baguera C disc arthroplasty.

OBJECTIVE: This retrospective study was designed to evaluate the incidence and predisposing factors of heterotopic ossification (HO) after cervical disc arthroplasty (CDA) with a specific implant at 1 and 2 levels, and to investigate the biomechanical effects related to HO. The study goal was to identify ways to reduce the likelihood of HO formation after surgery. METHODS: The study included patients who underwent only 1- or 2-level CDA with the Baguera C disc between November 2014 and December 2021 at a single medical center. All patients were operated on by the same neurosurgeon. The surgical indication included 1-level or 2-level disc herniation between C3 and C7 with radiculopathy, myelopathy, or both, with minimal spondylosis. The various factors were assessed by evaluating plain radiographs and cervical CT scans. The presence of HO was evaluated at different intervals postsurgery, and HO severity was graded using the McAfee classification. RESULTS: Of 107 patients who underwent CDA, 47 (43.9%) had HO at 63 of 171 levels (36.8%). Most cases with HO were grade 1, and no grade 4 was observed. Statistically significant risk factors for HO were the length of endplate coverage ratio and inferior anterior residual exposed endplate (AREE); sex, age, implant height and width, shell angle, and pre- and postoperative functional spinal unit (FSU) angle were not significant. More AREE and greater kyphotic postoperative FSU angle in the flexion position were significant factors differentiating HO grades 0 and 1 from grades 2 and 3. Furthermore, the non-HO group showed a trend of higher range of motion at any postoperative time compared to the HO group, especially at 1 month after surgery. CONCLUSIONS: The HO incidence after CDA was correlated with the residual length of endplate coverage and inferior AREE. Additionally, the AREE and kyphotic postoperative FSU angle in the flexion position were associated with HO grade progression. Patients with HO also showed a trend of lower range of motion at 1 month after surgery. Using an adequately sized implant and encouraging neck motion may help prevent HO development and progression.

Risk Factors for Cervical Disc Arthroplasty Subsidence with Bryan Disc-A Retrospective Observational Analysis.

Background: Cervical disc arthroplasty (CDA) is currently used instead of fusion to preserve cervical spine motion. Cervical implant subsidence is a potential complication after CDA. Methods: Radiological measurements were recorded via patient anteroposterior and lateral radiographs in the neutral position. Subsidence was defined as a decrease of 3 mm or more in functional spinal unit height (FSUH) from which was measured on a post-operative (OP) radiograph. Results: This study included 104 patients who underwent 153 CDA levels with the Bryan Disc. Approximately one-quarter of the implants (22.9%) showed subsidence. Binary logistic regression analysis indicated that pre-OP mean disc height (DH) was identified as an independent risk factor for subsidence in multivariate analysis (0.151, 95% Confidence Interval 0-0.073, p = 0.018). Receiver operating characteristic curve analysis (area under the curve = 0.852, sensitivity 84.7%, specificity 77.1%) revealed a cut-off value of 4.48 mm for pre-OP Mean-DH in the risk for implant subsidence. Conclusions: In this study, the subsidence rate significantly increased when the implants were oversized beyond a pre-OP Mean-DH of approximately >4 mm. Moreover, the implant subsidence incidence was higher than that reported in previous studies. This is possibly due to endplate over-preparation or disc space over-distraction during placement at the same height as the Bryan Disc (8.5 mm).

Anterior cervical discectomy and fusion versus cervical disc arthroplasty: an epidemiological review of 433,660 surgical patients from 2011 to 2021.

BACKGROUND CONTEXT: Anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) are commonly performed operations to address cervical radiculopathy and myelopathy. Trends in utilization and revision surgery rates warrant investigation. PURPOSE: To explore the epidemiology, postoperative complications, and reoperation rates of ACDF and CDA. DESIGN: Retrospective cohort study. PATIENT SAMPLE: A total of 433,660 patients who underwent ACDF or CDA between 2011 and 2021 were included in this study. OUTCOME MEASURES: The following data were observed for all cases: patient demographics, complications, and revisions. METHODS: The PearlDiver database was queried to identify patients who underwent ACDF and CDA between 2011 and 2021. Epidemiological analyses were performed to examine trends in cervical procedure utilization by age group and year. After matching by age, sex, Charlson Comorbidity Index (CCI), levels of operation, and reason for surgery, the early postoperative (2-week), short-term (2-year), and long-term (5-year) complications of both cervical procedures were examined. RESULTS: In total, 404,195 ACDF and 29,465 CDA patients were included. ACDF utilization rose by 25.25% between 2011 and 2014 while CDA utilization rose by 654.24% between 2011-2019 followed by relative plateauing in both procedures. Mann-Kendall trend test confirmed a significant but small rise in ACDF and large rise in CDA procedures from 2011 to 2021 (p<.001). After matching, ACDF and CDA had an overall complication rate of 12.20% and 8.77%, respectively, with the most common complications being subsequent anterior revision (4.96% and 3.35%) and dysphagia (3.70% and 2.98%). The ACDF cohort, especially multilevel ACDF patients, generally had more complications and higher revision rates than the CDA cohort (p<.05). CONCLUSIONS: While ACDF utilization has plateaued since 2014, CDA rates have risen by a staggering 654.24% over the past decade. ACDF and CDA complication and revision rates were relatively low in comparison to previously published values, with significantly lower rates in CDA. Although a lack of radiographic data in this study limits its power to recommend either procedure for individual patients with cervical radiculopathy or myelopathy, CDA may be associated with minor improvement in the complication and revision profile.

Cervical Disc Arthroplasty: Rationale, Designs, and Results of Randomized Controlled Trials.

BACKGROUND: This review outlines clinical data and characteristics of current Food and Drug Administration (FDA)-approved implants in cervical disc replacement/cervical disc arthroplasty (CDR/CDA) to provide a centralized resource for spine surgeons. METHODS: Randomized controlled trials (RCTs) on CDR/CDA were identified using a search of the PubMed, Web of Science, and Google Scholar databases. The initial search identified 69 studies. Duplicates were removed, and the following inclusion criteria were applied when determining eligibility of RCTs for the current review: (1) discussing CDR/CDA prosthesis and (2) published within between 2010 and 2020. Studies without clinical data or that were not RCTs were excluded. All articles were reviewed independently by 2 authors, with the involvement of an arbitrator to facilitate consensus on any discrepancies. RESULTS: A total of 34 studies were included in the final review. Findings were synthesized into a comprehensive table describing key features and clinical results for each FDA-approved CDR/CDA implant and are overall suggestive of expanding indications and increasing utilization. CONCLUSIONS: RCTs have provided substantial evidence to support CDR/CDA for treating single- and 2-level cervical degenerative disc disease in place of conventional anterior cervical discectomy and fusion. CLINICAL RELEVANCE: This review provides a resource that consolidates relevant clinical data for current FDA-approved implants to help spine surgeons make an informed decision during preoperative planning.

Are Patients With Segmental Cervical Kyphosis Appropriate Candidates for Cervical Disc Arthroplasty (CDA)? A Clinical and Radiographic Analysis Compared to Anterior Cervical Discectomy and Fusion (ACDF).

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: To compare the clinical and radiographic outcomes of Anterior Cervical Discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) in patients with preoperative segmental kyphosis. METHODS: Patients with segmental cervical kyphosis at the operative levels undergoing 1- or 2-level ACDF or CDA from 2017 to 2020 with 2 years of follow were identified. Patient demographics, perioperative data, complication rates, radiographic findings and reported outcomes were analyzed. RESULTS: A total of 48 patients met inclusion criteria and were included in our study (ACDF: n = 24, CDA: n = 24). Patient demographic data between the 2 cohorts was similar expect for proportion of males (ACDF: 62.5% vs CDA: 33.3%, P = .043). There was no statistical significance in the change of segmental lordosis (ACDF: +8.09° vs CDA: +5.88°, P = .075) between the preoperative and final postoperative period. Additionally, the change in cervical lordosis was similar between groups (ACDF:+ 9.86° vs CDA: +7.60°, P = .226). VAS scores were similar between the 2 groups at every follow-up interval. NDI scores were significantly different at the 6-month, 12 month and the final follow-up. Mean improvements between preoperative and final postoperative periods were statistically superior in the CDA cohort compared to the ACDF cohort (ACDF: 22.8 vs CDA: 24.1, P = .0375). CONCLUSION: CDA was superior to ACDF in regards to NDI scores following index procedure in patients with preoperative segmental cervical kyphosis. Those in the CDA cohort had similar complication rates, revision rates and radiographic outcomes as those who underwent ACDF.

[Influence of preoperative symptom duration on effectiveness of cervical disc arthroplasty in cervical spondylotic radiculopathy patients].

Objective: To investigate the influence of preoperative symptom duration on effectiveness of cervical disc arthroplasty (CDA) in cervical spondylotic radiculopathy (CSR) patients. Methods: The clinical data of 90 CSR patients who underwent single-segment CDA between January 2008 and March 2020 and met the selection criteria were retrospectively analyzed. Based on preoperative symptom duration, patients were divided into an early intervention group (preoperative symptom duration <24 months) and a late intervention group (preoperative symptom duration ≥24 months). There was no significant difference in baseline data between the two groups ( P>0.05), including age, gender, body mass index, smoking status, surgical segment, preoperative neck disability index (NDI), visual analogue scale (VAS) score, cervical lordosis (CL), C 2-C 7 range of motion (ROM), disc angle (DA), disc ROM (DROM), and disc intervertebral height (DIH). The early intervention group had a slightly higher preoperative Japan Orthopedic Association (JOA) score than the late intervention group ( P<0.05). Perioperative indicators such as operation time, intraoperative blood loss, and postoperative hospital stay were recorded. The changes of JOA score, NDI, and VAS score at last follow-up compared with those before operation were used to evaluate the clinical efficacy, and the imaging evaluation of CL, C 2-C 7 ROM, DA, DROM, and DIH was performed before operation, immediately after operation, and at last follow-up. The incidence of prosthesis-related complications, including heterotopic ossification (HO), anterior bone loss (ABL), and prosthesis subsidence, was also assessed at last follow-up. Results: Patients in both groups were followed up 24-120 months, with an average of 53.4 months. There was no significant difference in operation time, intraoperative blood loss, or follow-up duration between the groups ( P>0.05). However, the late intervention group had significantly longer postoperative hospital stay compared to the early intervention group ( P<0.05). At last follow-up, there was no significant difference in the changes of JOA score, NDI, and VAS score between the two groups before and after operation ( P>0.05). During the follow-up, there was no surgical revision in the two groups, and there was no significant difference in the incidence of HO, ABL, and prosthesis subsidence between the two groups at last follow-up ( P>0.05). Imaging evaluation showed that there was no significant difference in CL, C 2-C 7 ROM, DA, DROM, and DIH between the two groups at each time point before and after operation ( P>0.05). The intra-group comparison showed that the early intervention group could maintain the immediate postoperative CL at last follow-up, while the late intervention group had recovered to the preoperative level. Additionally, the C 2-C 7 ROM, DROM, and DA had all recovered to preoperative levels at last follow-up in both groups; meanwhile, the DIH significantly increased immediately after operation and sustained until the last follow-up. Conclusion: Preoperative symptom duration significantly affects the effectiveness of CDA in CSR patients. Patients with preoperative symptom duration ≥24 months have longer postoperative hospital stays and potentially poorer ability to maintain CL compared with patients with preoperative symptom duration <24 months.

Prosthesis design and likelihood of achieving physiological range of motion after cervical disc arthroplasty: analysis of range of motion data from 1,173 patients from 7 IDE clinical trials.

BACKGROUND CONTEXT: The functional goals of cervical disc arthroplasty (CDA) are to restore enough range of motion (ROM) to reduce the risk of accelerated adjacent segment degeneration but limit excessive motion to maintain a biomechanically stable index segment. This motion-range is termed the "Physiological mobility range." Clinical studies report postoperative ROM averaged over all study subjects but they do not report what proportion of reconstructed segments yield ROM in the Physiological mobility range following CDA surgery. PURPOSE: To calculate the proportion of reconstructed segments that yield flexion-extension ROM (FE-ROM) in the Physiological mobility range (defined as 5°-16°) by analyzing the 24-month postoperative data reported by clinical trials of various cervical disc prostheses. STUDY DESIGN/SETTING: Analysis of 24-month postoperative FE-ROM data from clinical trials. PATIENT SAMPLE: Data from 1,173 patients from single-level disc replacement clinical trials of 7 cervical disc prostheses. OUTCOME MEASURES: 24-month postoperative index-level FE-ROM. METHODS: The FE-ROM histograms reported in Food and Drug Administration-Investigational Device Exemption (FDA-IDE) submissions and available for this analysis were used to calculate the frequencies of implanted levels with postoperative FE-ROM in the following motion-ranges: Hypomobile (0°-4°), Physiological (5°-16°), and Hypermobile (≥17°). The ROM histograms also allowed calculation of the average ROM of implanted segments in each of the 3 motion-ranges. RESULTS: Only 762 of 1,173 patients (implanted levels) yielded 24-month postCDA FE-ROM in the physiological mobility range (5°-16°). The proportions ranged from 60% to 79% across the 7 disc-prostheses, with an average of 65.0%±6.2%. Three-hundred and two (302) of 1,173 implanted levels yielded ROM in the 0°-4° range. The proportions ranged from 15% to 38% with an average of 25.7%±8.9%. One-hundred and nine (109) of 1,173 implanted levels yielded ROM of ≥17° with a range of 2%-21% and an average proportion of 9.3%±7.9%. The prosthesis with built-in stiffness due to its nucleus-annulus design yielded the highest proportion (103/131, 79%) of implanted segments in the physiological mobility range, compared to the cohort average of 65% (p<.01). Sixty-five of the 350 (18.6%) discs implanted with the 2 mobile-core designs in this cohort yielded ROM≥17° as compared to the cohort average of 9.3% (109/1,173) (p<.05). At 2-year postCDA, the "hypomobile" segments moved on average 2.4±1.2°, those in the "physiological-mobility" group moved 9.4±3.2°, and the hypermobile segments moved 19.6±2.6°. CONCLUSIONS: Prosthesis design significantly influenced the likelihood of achieving FE-ROM in the physiological mobility range, while avoiding hypomobility or hypermobility (p<.01). Postoperative ROM averaged over all study subjects provides incomplete information about the prosthesis performance - it does not tell us how many implanted segments achieve physiological mobility and how many end up with hypomobility or hypermobility. We conclude that the proportion of index levels achieving postCDA motions in the physiological mobility range (5°-16°) is a more useful outcome measure for future clinical trials.

Comparing outcomes between anterior cervical disc replacement (ACDR) and minimally invasive posterior cervical foraminotomy (MI-PCF) in the treatment of cervical radiculopathy.

BACKGROUND CONTEXT: Anterior cervical disc replacement (ACDR) and minimally invasive posterior cervical foraminotomy (MI-PCF) have emerged as two increasingly popular alternatives to anterior cervical discectomy and fusion (ACDF) for the management of cervical radiculopathy. Both techniques provide advantages of segmental motion preservation and lower rates of adjacent segment degeneration (ASD) compared to ACDF. PURPOSE: The purpose of this study was to analyze the clinical and functional outcomes of patients undergoing ACDR or MI-PCF for the treatment of unilateral cervical radiculopathy. STUDY DESIGN/SETTING: Retrospective Cohort Review. PATIENT SAMPLE: A total of 152 patients were included (86 ACDR and 66 MI-PCF). OUTCOME MEASURES: (1) Patient demographics; (2) perioperative data; (3) rates of complications and revisions; (5) visual analogue scale (VAS) and Neck Disability Index (NDI) scores. METHODS: A retrospective cohort review was performed to identify all patients at a single institution between 2012-2020 who underwent 1- or 2- level ACDR or MI-PCF from C3-C7 with a minimum follow-up of 24 months. Patient demographics, perioperative data, postoperative complications, and revisions were analyzed. Patient reported outcome measures including VAS and NDI scores were compared. RESULTS: The ACDR group had a significantly greater mean operative time (99.8 minutes vs 79.2 minutes, p<.001), but comparable estimated blood loss and length of stay following surgical intervention (p=.899). The overall complication rate was significantly greater in the ACDR group than the MI-PCF group (24.4% vs 6.2%; p=.003) but was largely driven by approach-related dysphagia in 20.9% of ACDR patients. The MI-PCF group had significantly greater revision rates (13.6% vs 1.2%; p=.002) with an average time to revision of 20.7 months in the MI-PCF group compared to 40.3 months in the ACDR group. The ACDR cohort had significantly greater improvements in NDI scores at the final follow-up (25.0 vs 21.3, p<.001). CONCLUSION: Our results suggest that ACDR offer clinically relevant advantages over MI-PCF in terms of long-term revision rates despite an increased approach-related risk of transient postoperative dysphagia. Additionally, patients in the ACDR cohort achieved greater mean improvements in NDI scores but these results may have limited clinical significance due to inability to reach minimally clinically important difference (MCID) thresholds.