Artificial intelligence in predicting postoperative heterotopic ossification following anterior cervical disc replacement.

OBJECTIVE: This study aimed to develop and validate a machine learning (ML) model to predict high-grade heterotopic ossification (HO) following Anterior cervical disc replacement (ACDR). METHODS: Retrospective review of prospectively collected data of patients undergoing ACDR or hybrid surgery (HS) at a quaternary referral medical center was performed. Patients diagnosed as C3-7 single- or multi-level cervical disc degeneration disease with > 2 years of follow-up and complete pre- and postoperative radiological imaging were included. An ML-based algorithm was developed to predict high grade HO based on perioperative demographic, clinical, and radiographic parameters. Furthermore, model performance was evaluated according to discrimination and overall performance. RESULTS: In total, 339 ACDR segments were included (61.65% female, mean age 45.65 ± 8.03 years). Over 45.65 ± 8.03 months of follow-up, 48 (14.16%) segments developed high grade HO. The model demonstrated good discrimination and overall performance according to precision (High grade HO: 0.71 ± 0.01, none-low grade HO: 0.85 ± 0.02), recall (High grade HO: 0.68 ± 0.03, none-low grade HO: 0.87 ± 0.01), F1-score (High grade HO: 0.69 ± 0.02, none-low grade HO: 0.86 ± 0.01), and AUC (0.78 ± 0.08), with lower prosthesis­endplate depth ratio, higher height change, male, and lower postoperative-shell ROM identified as the most important predictive features. CONCLUSION: Through an ML approach, the model identified risk factors and predicted development of high grade HO following ACDR with good discrimination and overall performance. By addressing the shortcomings of traditional statistics and adopting a new logical approach, ML techniques can support discovery, clinical decision-making, and intraoperative techniques better.

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.

Revolutionizing Relief: Cervical Radiculopathy With Neurological Deficits Rescued by Cervical Disc Replacement.

Cervical radiculopathy is a common condition characterized by neck pain radiating to the upper and lower limbs, often accompanied by tingling sensations, numbness, and weakness. We present the case of a 32-year-old male who presented with left-sided cervical radiculopathy and neurological deficits. Clinical examination revealed left C5/C6/C7 hypoesthesia, diminished grip strength, reduced power in the left upper and lower extremities, and a positive Spurling test. Magnetic resonance imaging (MRI) of the cervical spine revealed multilevel cervical disc herniations at C4-C5 and C5-C6 levels, resulting in stenosis. The patient underwent anterior cervical discectomies with artificial disc replacement (cervical disc arthroplasty (CDA)) at the C5-C6 level. The surgical procedure was uneventful, and the patient experienced prompt relief from neurological symptoms within two weeks postoperatively. Follow-up radiographs at one week post-surgery demonstrated a preserved range of motion at each operated level with the artificial disc in situ. This case highlights the successful management of cervical radiculopathy with neurological deficits using anterior cervical discectomy and artificial disc replacement. The timely intervention led to the resolution of symptoms and restoration of function, demonstrating the efficacy of this surgical approach in alleviating radicular symptoms and preserving cervical spine mobility. Further studies and long-term follow-up are warranted to validate the long-term outcomes and durability of artificial disc replacement in such cases.

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.

Could the different surgical goals of fusion and non-fusion also be achieved in combination within the same patient? Clinical and radiological outcome of hybrid cervical spine surgery.

PURPOSE: Hybrid cervical spine surgery (HS) is a novel surgical strategy wherein an artificial disc replacement is done with a cervical fusion nearby with a stand-alone titanium cage to combine the advantages in both procedures. The aim of this study was to evaluate interactions of these devices within the same patient, and to analyze, if the different goal of each implant is accomplished. METHODS: Thirty-six patients were treated surgically within a non-randomized retrospective study framework with HS. Patients were examined preoperatively followed by clinical and radiological examination at least one year postoperative. Clinical outcome was detected with NDI, VAS arm/neck, pain self-assessment questionnaires and subjective patient satisfaction. Radiological assessments included RoM, segmental lordosis, cervical lordosis of C2-C7, subsidence, ap-migration and heterotopic ossifications (HO) at the cTDR levels. RESULTS: Statistically significant improvement of all clinical scores was observed (NDI 37.5 to 5.76; VASarm 6.41 to 0.69; VASneck 6.78 to 1.48). Adequate RoM was achieved at cTDR levels. RoM in the ACDF levels was reduced statistically significant (p < 0.001), and solid fusion (> 2°) was achieved in all evaluated fusion level. Global lordosis (C2-C7) increased statistically significant (2.4° to 8.1°). Subsidence and HO at the cTDR levels did not occur. CONCLUSIONS: HS results in preservation of the segmental motion in the cTDR and fast and solid fusion in the cage cohort simultaneously. Patient safety was proven. In carefully selected cases, HS is a safe and viable treatment option by choosing the right "philosophy" level per level.

The association of cervical sagittal alignment with anterior bone loss following single-level anterior cervical surgery.

Background: Anterior bone loss (ABL) is a common phenomenon after cervical disc replacement (CDR), which can also be observed after anterior cervical discectomy and fusion (ACDF). This study aimed to investigate the incidence and severity of ABL in single-level CDR and ACDF and explore the association of cervical sagittal alignment with ABL. Methods: This is a single-center retrospective cohort study. A total of 113 patients treated with CDR and 99 patients treated with ACDF were retrospectively reviewed from January 2014 to December 2018 in West China Hospital. Radiological data were collected at pre-operation, 1 week, 3 months postoperatively, and the last follow-up. The incidence and severity of ABL after both CDR and ACDF were evaluated. Cervical sagittal alignment parameters, including C0-C2 angle, cervical lordosis (CL), C2-C7 sagittal vertical axis (cSVA), T1 slope, functional spinal unit angle, disc angle, and surgical level slope, were evaluated. Results: ABL was identified in 75 (66.4%) patients in the CDR group and 57 (57.6%) patients in the ACDF group. There were no significant differences in the incidence, severity, and location of ABL between the ACDF and CDR groups. For patients who underwent ACDF, the proportion of females was significantly higher in the ABL group (64.9% vs. 33.3%, P=0.002), whereas the body mass index (BMI) was significantly lower in the ABL group compared to the non-ABL group (22.72±3.09 vs. 24.60±3.04, P=0.002). No effect of ABL on the short-term clinical outcomes of ACDF and CDR was observed. In the ACDF group, patients with ABL had significantly smaller postoperative CL (11.83°±8.24° vs. 15.25°±8.32°, P=0.04) and cSVA (17.77±10.08 vs. 23.35±9.86 mm, P=0.007). In the CDR group, no significant differences were found in the cervical sagittal parameters between patients with and without ABL (CL: 12.58±8.70 vs. 15.46±8.50, P=0.10; cSVA: 20.95±8.54 vs. 19.40±9.43, P=0.38). Conclusions: ABL is common after both CDR and ACDF with comparable incidence and severity. Cervical sagittal alignment was closely related to ABL after ACDF yet had less influence on ABL after CDR.

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.

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.

An additively manufactured model for preclinical testing of cervical devices.

Purpose: Composite models have become commonplace for the assessment of fixation and stability of total joint replacements; however, there are no comparable models for the cervical spine to evaluate fixation. The goal of this study was to create the framework for a tunable non-homogeneous model of cervical vertebral body by identifying the relationships between strength, in-fill density, and lattice structure and creating a final architectural framework for specific strengths to be applied to the model. Methods: The range of material properties for cervical spine were identified from literature. Using additive manufacturing software, rectangular prints with three lattice structures, gyroid, triangle, zig-zag, and a range of in-fill densities were 3D-printed. The compressive and shear strengths for all combinations were calculated in the axial and coronal planes. Eleven unique vertebral regions were selected to represent the distribution of density. Each bone density was converted to strength and subsequently correlated to the lattice structure and in-fill density with the desired material properties. Finally, a complete cervical vertebra model was 3D-printed to ensure sufficient print quality. Results: Materials testing identified a relationship between in-fill densities and strength for all lattice structures. The axial compressive strength of the gyroid specimens ranged from 1.5 MPa at 10% infill to 31.3 MPa at 100% infill and the triangle structure ranged from 2.7 MPa at 10% infill to 58.4 MPa at 100% infill. Based on these results, a cervical vertebra model was created utilizing cervical cancellous strength values and the corresponding in-fill density and lattice structure combination. This model was then printed with 11 different in-fill densities ranging from 33% gyroid to 84% triangle to ensure successful integration of the non-homogeneous in-fill densities and lattice structures. Conclusions: The findings from this study introduced a framework for using additive manufacturing to create a tunable, customizable biomimetic model of a cervical vertebra.

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.

Cervical disc arthroplasty versus anterior cervical discectomy and fusion: an analysis of the Michigan Spine Surgery Improvement Collaborative Database.

BACKGROUND CONTEXT: Anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) are established surgical options for the treatment of cervical radiculopathy, myelopathy, and cervical degenerative disc disease. However, current literature does not demonstrate a clear superiority between ACDF and CDA. PURPOSE: To investigate procedural and patient-reported outcomes of ACDF and CDA among patients included in the Michigan Spine Surgery Improvement Collaborative (MSSIC) database. DESIGN: Retrospective study of prospectively collected outcomes registry data. PATIENT SAMPLE: Individuals within the MSSIC database presenting with radiculopathy, myelopathy, or cervical spondylosis refractory to typical conservative care undergoing primary ACDF or CDA from January 4, 2016, to November 5, 2021. OUTCOME MEASURES: Perioperative measures (including surgery length, length of stay, return to OR, any complications), patient-reported functional outcomes at 2-year follow-up (including return to work, patient satisfaction, PROMIS, EQ-5D, mJOA). METHODS: Patients undergoing ACDF were matched 4:1 with those undergoing CDA; propensity analysis performed on operative levels (1- and 2- level procedures), presenting condition, demographics, and comorbidities. Initial comparisons performed with univariate testing and multivariate analysis performed with Poisson generalized estimating equation models clustering on hospital. RESULTS: A total of 2,208 patients with ACDF and 552 patients with CDA were included. Baseline demographics were similar, with younger patients undergoing CDA (45.6 vs 48.6 years; p<.001). Myelopathy was more frequent in ACDF patients (30% vs 25%; p=.015). CDA was more frequently planned as an outpatient procedure. Length of stay was increased in ACDF (1.3 vs 1.0 days; p<.001). Functional outcomes were similar, with comparable proportions of patients meeting minimal clinically important difference thresholds in neck pain, arm pain, PROMIS, EQ-5D, and mJOA score. After multivariate regression, no significant differences were seen in surgical or functional outcomes. CONCLUSIONS: This study demonstrates similar outcomes for those undergoing ACDF and CDA at 2 years. Previous meta-analyses of CDA clinical trial data adhere to strict inclusion and exclusion criteria required by clinical studies; this registry data provides "real world" clinical outcomes reflecting current practices for ACDF and CDA patient selection.

Severe Obesity Is an Independent Risk Factor of Early Readmission and Nonhome Discharge After Cervical Disc Replacement.

OBJECTIVE: Despite growing interest in cervical disc replacement (CDR) for conditions such as cervical radiculopathy, limited data exists describing the impact of obesity on early postoperative outcomes and complications. These data are especially important as nearly half of the adult population in the United States is expected to become obese (body mass index [BMI] ≥ 30 kg/m2) by 2030. The goal of this study was to compare the demographics, perioperative variables, and complication rates following CDR. METHODS: The 2005-2020 American College of Surgeons National Surgical Quality Improvement Program datasets were queried for patients who underwent primary 1- or 2-level CDR. Patients were divided into 3 cohorts: Nonobese (BMI: 18.5-29.9 kg/m2), Obese class-I (BMI: 30-34.9 kg/m2), Obese class-II/III (BMI ≥ 35 kg/m2). Morbidity was defined as the presence of any complication within 30 days postoperatively. Rates of 30-day readmission, reoperation, morbidity, individual complications, length of stay, frequency of nonhome discharge disposition were collected. RESULTS: A total of 5,397 patients were included for analysis: 3,130 were nonobese, 1,348 were obese class I, and 919 were obese class II/III. There were more 2-level CDRs performed in the class II/III cohort compared to the nonobese group (25.7% vs. 21.5%, respectively; p < 0.05). Class-II/III had more nonhome discharges than class I and nonobese (2.1% vs. 0.5% vs. 0.7%, respectively; p < 0.001). Readmission rates differed as well (nonobese: 0.5%, class I: 1.1%, class II/III: 2.1%; p < 0.001) with pairwise significance between class II/II and nonobese. Class II/III obesity was an independent risk factor for both readmission (odds ratio [OR], 3.32; p = 0.002) and nonhome discharge (OR, 2.51; p = 0.02). Neither 30-day reoperation nor morbidity rates demonstrated significance. No mortalities were reported. CONCLUSION: Although obese class-II/III were risk factors for 30-day readmission and nonhome discharge, there was no significant difference in reoperation rates or morbidity. CDR procedures can continue to be safely preformed independent of obesity status.

Long-term functional and radiological outcomes of cervical disc arthroplasty at a tertiary level spine center in India: A retrospective cohort analysis with minimum 2 years of follow-up.

Context: Cervical disc arthroplasty (CDA) was developed for the treatment of cervical disc disease with the potential advantages of preservation of physiological motion at a discal level, thereby potentially reducing adjacent level stresses and degeneration, which were a known complication of anterior cervical arthrodesis. The objective of this study was the assessment of long-term functional and radiological outcomes overtime in all the patients who underwent CDA from 2011 to 2019 at our institute. Materials and Methods: Forty-eight patients who underwent CDA (2011-2019) with a minimum 2-year follow-up were retrospectively evaluated. The functional outcome included the Visual Analog Score (VAS) and Neck Disability Index (NDI). Radiographs were assessed for range of motion (ROM) at the index surgical level, presence of heterotopic ossification (HO), and adjacent segment degeneration. Results: The mean follow-up was 5.79 ± 2.96 (2.16-11.75) years. Significant improvement (P < 0.05) was observed in the VAS (8.91 ± 2.52 [preoperative] to 0.89 ± 1.27 [follow-up]) and NDI (65.5% ±23.06% [preoperative] to 4.79 ± 3.87 [follow-up]) score. Motion at index level increased significantly from 5.53° preoperatively to 7.47°, and 92% of the implanted segments were still mobile (referring to the threshold of ROM > 3°). HOs are responsible for the fusion of 4/50 (8%) levels at the last follow-up. Distal and proximal adjacent disc degeneration occurred in 36% and 28% of patients, respectively. No migration of the implant was observed on the radiograph. Conclusion: Our study showed favorable clinical outcome of CDA with preservation of ROM at the index surgical level. CDA can be a promising alternative to anterior cervical arthrodesis when properly indicated.

Risk factors for failure to achieve minimal clinically important difference following cervical disc replacement.

BACKGROUND CONTEXT: While cervical disc replacement (CDR) has been emerging as a reliable and efficacious treatment option for degenerative cervical spine pathology, not all patients undergoing CDR will achieve minimal clinically important difference (MCID) in patient-reported outcome measures (PROMs) postoperatively-risk factors for failure to achieve MCID in PROMs following CDR have not been established. PURPOSE: To identify risk factors for failure to achieve MCID in Neck Disability Index (NDI, Visual Analog Scale (VAS) neck and arm following primary 1- or 2-level CDRs in the early and late postoperative periods. STUDY DESIGN: Retrospective review of prospectively collected data. PATIENT SAMPLE: Patients who had undergone primary 1- or 2-level CDR for the treatment of degenerative cervical pathology at a single institution with a minimum follow-up of 6 weeks between 2017 and 2022. OUTCOME MEASURES: Patient-reported outcomes: Neck disability index (NDI), Visual analog scale (VAS) neck and arm, MCID. METHODS: Minimal clinically important difference achievement rates for NDI, VAS-Neck, and VAS-Arm within early (within 3 months) and late (6 months to 2 years) postoperative periods were assessed based on previously established thresholds. Multivariate logistic regressions were performed for each PROM and evaluation period, with failure to achieve MCID assigned as the outcome variable, to establish models to identify risk factors for failure to achieve MCID and predictors for achievement of MCID. Predictor variables included in the analyses featured demographics, comorbidities, diagnoses/symptoms, and perioperative characteristics. RESULTS: A total of 154 patients met the inclusion criteria. The majority of patients achieved MCID for NDI, VAS-Neck, and VAS-Arm for both early and late postoperative periods-79% achieved MCID for at least one of the PROMs in the early postoperative period, while 80% achieved MCID for at least one of the PROMs in the late postoperative period. Predominant neck pain was identified as a risk factor for failure to achieve MCID for NDI in the early (OR: 3.13 [1.10-8.87], p-value: .032) and late (OR: 5.01 [1.31-19.12], p-value: .018) postoperative periods, and VAS-Arm for the late postoperative period (OR: 36.63 [3.78-354.56], p-value: .002). Myelopathy was identified as a risk factor for failure to achieve MCID for VAS-Neck in the early postoperative period (OR: 3.40 [1.08-10.66], p-value: .036). Anxiety was identified as a risk factor for failure to achieve MCID for VAS-Neck in the late postoperative period (OR: 6.51 [1.91-22.18], p-value: .003). CDR at levels C5C7 was identified as a risk factor for failure to achieve MCID in NDI for the late postoperative period (OR: 9.74 [1.43-66.34], p-value: .020). CONCLUSIONS: Our study identified several risk factors for failure to achieve MCID in common PROMs following CDR including predominant neck pain, myelopathy, anxiety, and CDR at levels C5-C7. These findings may help inform the approach to counseling patients on outcomes of CDR as the evidence suggests that those with the risk factors above may not improve as reliably after CDR.

Post-Operative Physical Therapy Following Cervical Spine Surgery: Analysis of Patient-Reported Outcomes.

Introduction Post-operative physical therapy (PT) following anterior cervical discectomy and fusion (ACDF) surgery is often performed to improve a patient's functional ability and reduce neck pain. However, current literature evaluating the benefits of post-operative PT using patient-reported outcomes (PROs) is limited and remains inconclusive. Here we compare post-operative improvement between patients who did and did not undergo formal PT after ACDF using Patient-Reported Outcomes Measurement Information System (PROMIS) scores. Methods A retrospective observational study examining patients who underwent one- or two-level primary ACDF or cervical disc replacement (CDR) at an academic orthopedic hospital and who had PROMIS scores recorded pre-operatively and through two-year follow-up. Patients were stratified according to whether or not they attended formal postoperative PT. PROMIS scores and patient demographics were compared using the Mann-Whitney U test, Fisher's exact test, chi-square test of independence, and Student's t-test within and between cohorts. Results Two hundred and twenty patients were identified. Demographic differences between PT and no PT groups include age (PT 54.1 vs. no PT 49.5, p=0.005) and BMI (PT 28.1 vs. no PT 29.8, p=0.028). The only significant difference in post-operative PROMIS scores was in physical health scores at three months post-operatively (no PT 43.9 vs. PT 39.1, p=0.008). Physical health scores improved from baseline to one-year follow-up in both cohorts (PT +3.5, p=0.025; no PT +6.6, p=0.008). There were no significant differences when comparing improvements in physical health scores between groups at six months and one year. Conclusion In conclusion, there was no significance to support the benefits of post-operative PT as measured by PROMIS scores. No significant differences in PROMIS were observed between groups from pre-operative baseline scores to six-month and one-year follow-ups.

The Role of Cervical Disc Arthroplasty in Elite Athletes.

PURPOSE OF REVIEW: Cervical disc arthroplasty (CDA) for the treatment of symptomatic cervical disc herniations (CDH) is a promising treatment for professional athletes. In recent years, a number of high-profile athletes have returned to professional play within three months after CDA, raising important questions about the potential of this procedure within this patient group. We provide the first comprehensive review of available literature for the safety and efficacy of CDA in professional contact sport athletes. RECENT FINDINGS: CDA provides theoretical biomechanical advantages over anterior cervical discectomy and fusion (ACDF) and posterior foraminotomy (PF), as CDA is the only operation for treatment of CDH that provides neural decompression, stability and height restoration, with preserved range of motion. While the comparative long-term results from each procedure are unknown, CDA has provided encouraging promise in its use in professional contact athletes. We aim to aid ongoing discussions regarding the controversies in spine surgery for professional athletes by providing a scientific review of the available evidence-based literature involving cervical disc arthroplasty in this population. In general, we believe that CDA is a viable alternative to ACDF and PF for the contact professional athlete who requires full neck range of motion and desires an expedited return to play. For collision athletes, the short- and long-term safety and efficacy profile of this procedure is promising but still unclear.

Cervical disc arthroplasty with the Baguera C prosthesis: clinical and radiological results of a 10-year follow-up study.

PURPOSE: We evaluated the long-term safety, mobility and complications of cervical total disc arthroplasty with the Baguera®C prosthesis over 10 years. METHODS: We included 91 patients treated by arthroplasty for cervical degenerative disc disease. A total of 113 prostheses were implanted (50 one-level, 44 two-level and 19 hybrid constructs). They were assessed for complications, clinically, with NDI and SF-12 questionnaires and by independent radiologists for ROM, HO, disc height and adjacent level degeneration. RESULTS: No spontaneous migration, loss of fixation, subsidence, vascular complication or dislocation were observed. The reoperation rate was 1%. About 82.7% of the patients were pain free. About 9.9% were taking occasional grade I painkillers. Motricity and sensitivity were preserved in 98.8% and 96.3%. The NDI showed an average functional disability of 17.58%, 26% lower than preoperatively. The SF-12 scores were close to normal health. The average ROM at the treated level was 7.4°. Motion was preserved in 86.6%. Lack of motion was observed in 13.4%. Grades II and III H0 were present in 53.7% and 31.7%, respectively, Grade IV was present in 13.4%. Motion was preserved in 100% of the grades 0-III. The preoperative adjacent level disc height of 4.3 mm remained stable during all the follow-ups at 4.4 mm and 4.2 mm, respectively, at 5 and 10 years. CONCLUSIONS: After 10 years, cervical arthroplasty with the Baguera®C prosthesis presents excellent safety and functional results and low complications. Motion was preserved in 86.6%, with a 7.4° ROM. Although common, HO did not hinder motion. Adjacent disc height preservation confirms some adjacent level degeneration protection.

Observations of bony ongrowth and clinical fixation in two retrieved disc replacements.

Total disc replacements utilize textured coatings to maximize bony ongrowth. However, the contribution of direct bony attachment to overall fixation for total disc replacements has not been reported. The goal of the present study was to document the extent of bony attachment to the surfaces of two clinically functional total disc replacements that were securely fixed at the time of revision. Two metal-and-polymeric disc replacements, one cervical and one lumbar, were evaluated following surgical retrieval. The cervical device was retrieved at 8 months and the lumbar device at 28 months post-operative. Both devices were reported well-fixed at the time of removal, with large bone masses attached to one endplate of each device. Visual inspections, non-destructive gravimetric measurements, and surface metrology were performed to assess fixation. These inspections suggested that both devices had been fixed at the time of removal with little in vivo mechanical damage, as surgical extraction damage was noted on both devices and provided imaging showed a lack of device migration. Devices were then embedded and sectioned to evaluate the bone-implant interface. High resolution photographs and contact microradiographs were taken to assess bony attachment. In contrast to initial analysis, these images revealed radiolucent gaps between the endplates and bone masses. Little direct contact between the bone and endplate surface was identified and the original surgical cuts were still visible. Both devices were clinically fixed at the time of removal and neither had complications associated with loosening. However, osseointegration was minimal in one of the devices and altogether absent from the other. The findings of the present study suggest that other factors may influence overall clinical fixation such as the surgical preparation of the vertebral bone or the surface roughness of the treated endplates. Despite the limitations of the present study, this information is unique to the current total disc replacement literature and the ongrowth and fixation of devices should be considered as a topic for future investigation.

Differences in Time to Achieve Minimum Clinically Important Difference Between Patients Undergoing Anterior Cervical Discectomy and Fusion and Cervical Disc Replacement.

OBJECTIVE: To compare patients undergoing anterior cervical discectomy and fusion (ACDF) versus cervical disc replacement (CDR) for time to minimum clinically important difference (MCID) achievement and predictors of delayed MCID achievement for the patient-reported outcomes (PROs), Patient-Reported Outcomes Measurement Information System Physical Function, Neck Disability Index, Visual Analog Scale (VAS) neck, and VAS arm. METHODS: PROs of patients undergoing ACDF or CDR were collected preoperatively and postoperatively at 6-week/12-week/6-month/1-year/2-year periods. MCID achievement was calculated through comparison of changes in Patient-Reported Outcomes Measurement to previously established values in literature. Time to MCID achievement and predictors for delayed MCID achievement were determined through Kaplan-Meier survival analysis and multivariable Cox regression, respectively. RESULTS: One hundred ninety-seven patients were identified, with 118 and 79 undergoing ACDF and CDR, respectively. Kaplan-Meier survival analysis demonstrated faster time to achieve MCID for CDR patients in Patient-Reported Outcomes Measurement Information System Physical Function (P = 0.006). Early predictors of MCID achievement through Cox regression were CDR procedure, Asian ethnicity, elevated preoperative PROs of VAS neck and VAS arm (hazard ratio, 1.16-7.28). Workers' compensation was a late predictor of MCID achievement (hazard ratio, 0.15). CONCLUSIONS: Most patients achieved MCID in physical function, disability, and back pain outcomes within 2 years of surgery. Patients undergoing CDR achieved MCID faster in physical function. Early predictors of MCID achievement were CDR procedure, Asian ethnicity, and elevated preoperative PROs of pain outcomes. Workers' compensation was a late predictor. These findings may be helpful in managing patient expectations.

Mechanical characterization of a novel biomimetic artificial disc for the cervical spine.

A novel biomimetic artificial intervertebral disc (bioAID) replacement implant has been developed containing a swelling hydrogel representing the nucleus pulposus, a tensile strong fiber jacket as annulus fibrosus and titanium endplates with pins to primarily secure the device between the vertebral bodies. In this study, the design safety of this novel implant was evaluated based on several biomechanical parameters, namely compressive strength, shear-compressive strength, risk of subsidence and device expulsion as well as identifying the diurnal creep-recovery characteristics of the device. The bioAID remained intact up to 1 kN under static axial compression and only 0.4 mm of translation was observed under a compressive shear load of 20 N. No subsidence was observed after 0.5 million cycles of sinusoidal compressive loading between 50 and 225 N. After applying 400 N in antero-posterior direction under 100 N axial compressive preload, approximately 2 mm displacement was found, being within the range of displacements reported for other commercially available cervical disc replacement devices. The diurnal creep recovery behavior of the bioAID closely resembled what has been reported for natural intervertebral discs in literature. Overall, these results indicate that the current design can withstand (shear-compression loads and is able to remain fixed in a mechanical design resembling the vertebral bodies. Moreover, it is one of the first implants that can closely mimic the poroelastic and viscoelastic behavior of natural disc under a diurnal loading pattern.