Single-level Cervical Disc Replacement Research Articles

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

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. 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. 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). 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.

Single-level cervical disc replacement (CDR) versus anterior cervical discectomy and fusion (ACDF): A Nationwide matched analysis of complications, 30- and 90-day readmission rates, and cost

Single-level cervical disc replacement (CDR) versus anterior cervical discectomy and fusion (ACDF): A Nationwide matched analysis of complications, 30- and 90-day readmission rates, and cost

Up to 10-year surveillance comparison of survivability in single-level cervical disc replacement versus anterior cervical discectomy and fusion in New York.

Cervical disc replacement (CDR) is an alternative treatment to anterior cervical discectomy and fusion (ACDF), which is the current gold standard, for degenerative cervical diseases such as cervical spondylotic myelopathy and cervical radiculopathy. CDR has several theoretical benefits over ACDF, including preservation of motion, earlier return to unrestricted activity, and potentially a lower risk of adjacent-segment disease. Recent literature has reported positive clinical results for CDR, but few studies have investigated the long-term risk of revision surgery of CDR versus ACDF. The purpose of this study was to identify and analyze the epidemiological, clinical, and operative risk factors that affect revision rates following single-level CDR and ACDF procedures. A retrospective cohort was extracted from the Statewide Planning and Research Cooperative System using ICD-9 and CPT codes. Inclusion criteria were adult patients undergoing primary, subaxial (C3-7), single-level ACDF or CDR for cervical radiculopathy and/or cervical spondylotic myelopathy between 2005 and 2013. Survivability was defined as the time between the index procedure and the presence of a subsequent discharge record for cervical spinal fusion or disc replacement. Statistical analyses were performed using chi-square tests, t-tests, Cox proportional hazards models, and a Kaplan-Meier plot. A total of 7450 patients were included in this study (6615 ACDF and 835 CDR). When adjusted for patient demographics, the hazard ratios showed no significant differences in the incidence of revision risk between the two cohorts. The CDR cohort had a higher incidence of postoperative dysphagia (p < 0.05). Patients undergoing ACDF had a longer average hospital stay (2.8 vs 1.9 days, p < 0.001). There was no significant difference in time to revision surgery (p = 0.486). CDR and ACDF have both been shown to be effective treatments for cervical spine disease. CDR patients had a shorter average inpatient hospital stay compared with ACDF patients but tended to experience dysphagia more frequently. There was a tendency toward increased survivability of CDR; however, this was not found to be statistically significant at any time point. The large size and heterogeneity of each cohort and the availability of > 10 years of surveillance data differentiate this study from other published literature. This investigation has limitations inherent to large data analysis studies, including the implementation and inaccuracy of diagnosis and procedural coding; however, this reflects real-world use of coding by practitioners.

4. Single-level cervical disc replacement using a PEEK-on-ceramic implant: Results of a multicenter FDA IDE trial with 24-month follow up

<h3>BACKGROUND CONTEXT</h3> Many early cervical total disc replacements (TDRs) produced motion through a ball-and-socket action, with metal endplates articulating with a plastic core. PEEK is used increasingly for spinal implants due to its mechanical properties and lack of artifact on imaging. A cervical TDR was designed with commercially pure titanium-coated PEEK endplates and a biconvex zirconia toughened alumina ceramic core. <h3>PURPOSE</h3> The purpose of this study was to compare this PEEK-on-ceramic TDR to anterior cervical discectomy and fusion (ACDF) to treat single-level cervical disc degeneration. <h3>STUDY DESIGN/SETTING</h3> This was a prospective, nonrandomized, multicenter Food and Drug Administration (FDA) Investigational Device Exemption (IDE) trial comparing the investigational group to a propensity-matched historic control group. <h3>PATIENT SAMPLE</h3> Patients received the PEEK-on-ceramic Simplify® Cervical Artificial Disc (n=150 patients from 16 sites). The historic control group included 117 propensity-matched ACDF patients from an earlier cervical TDR IDE trial employing the same inclusion/exclusion criteria. All patients were treated for single-level symptomatic cervical disc degeneration. <h3>OUTCOME MEASURES</h3> The primary outcome was a composite 5-point success classification at 24-month follow-up requiring: >15 point (of 100) improvement in Neck Disability Index (NDI) score; 2) maintenance/improvement in neurologic status; 3) no device failure; 4) no reoperation/revision/removal and/or supplemental fixation at the index level, and 5) no major adverse events. Outcome measures included NDI, visual analog scale (VAS) assessing neck and arm pain, neurological status, adverse events and subsequent surgery. Radiographic assessment included flexion/extension range of motion. Facet joints were assessed at 24 months comparing pre- to postoperative MRI images using a published 4-point scale. <h3>METHODS</h3> Evaluations were performed preoperatively and postoperatively within 2 and 6 weeks, and 3, 6, 12 and 24 months. The control was propensity match with ACDF patients from an earlier TDR vs ACDF trial, which used the same inclusion criteria and primary outcome assessments. <h3>RESULTS</h3> The overall composite success rate was significantly greater in the TDR group vs ACDF (93.0% vs 73.6%; p<0.001). Mean NDI, neck pain and arm pain scores improved significantly in both groups at all follow-up points. Mean NDI scores in the TDR group were significantly lower than ACDF scores at all follow-up points all p<0.01). Secondary surgical intervention was undertaken in 4 (2.7%) patients at the index level in the TDR group and 6 (5.1%) in the ACDF group. There were no significant differences in the rates of serious adverse events when comparing the two groups. The mean segmental range of motion of the treated level in the TDR group was 7.3° prior to surgery. This increased to 8.6° at 3-month follow-up and continued to increase to 9.6° at 24 months (p<0.001). Facet joint assessment by MRI at 24-month follow-up in the TDR group showed little change from preoperative. <h3>CONCLUSIONS</h3> The results of this study found that the Simplify® Cervical Artificial Disc produced outcomes similar or superior on some measures, including superiority in the composite success classification, compared with ACDF, for the treatment of single-level symptomatic cervical disc degeneration. ROM at the treated level increased from the preoperative value and was maintained throughout follow-up. Safety of the PEEK-on-ceramic disc was established with no device failures in the series. These results support that the device is a viable alternative to ACDF. <h3>FDA DEVICE/DRUG STATUS</h3> Simplify Cervical Disc Replacement (Approved for this indication)

Single-Level Cervical Disc Replacement Using a PEEK-on-Ceramic Implant: Results of a Multicenter FDA IDE Trial With 24-Month Follow-up.

Many early cervical total disc replacements (TDRs) produced motion through a ball-and-socket action, with metal endplates articulating with a plastic core. Polyetheretherketone (PEEK) is used increasingly for spinal implants due to its mechanical properties and lack of artifacts on imaging. A TDR was designed with titanium-coated PEEK endplates and a ceramic core. The purpose of this study was to compare this TDR with anterior cervical discectomy and fusion (ACDF) to treat single-level cervical disc degeneration. This was a prospective, nonrandomized, historically controlled, multicenter US Food and Drug Administration (FDA) Investigational Device Exemption (IDE) trial. Patients received the PEEK-on-ceramic Simplify® Cervical Artificial Disc (n = 150). The historic control group included 117 propensity-matched ACDF patients from an earlier IDE trial. The primary outcome was a composite success classification at the 24-month follow-up. Outcome measures included the Neck Disability Index (NDI), neurological status, adverse events, subsequent surgery, a visual analog scale assessing neck and arm pain, and the Dysphagia Handicap Index. Radiographic assessment included flexion/extension range of motion and heterotopic ossification. Facet joints were assessed at 24 months using MRI. The success rate was significantly greater in the TDR group vs the ACDF group (93.0% vs 73.6%; P < .001). Mean NDI, neck pain, and arm pain scores improved significantly in both groups at all follow-up points. Mean NDI scores in the TDR group were significantly lower than ACDF scores at all follow-up points. There were no significant differences in the rates of serious adverse events. The range of motion of the TDR level had increased significantly by 3 months and remained so throughout follow-up. Facet joint assessment by MRI in the TDR group showed little change from preoperation. The TDR had an acceptable safety profile and a significantly greater composite success rate than ACDF. These results support that the PEEK-on-ceramic TDR is a viable alternative to ACDF for single-level symptomatic disc degeneration. This study found that the PEEK-on-ceramic TDR is a viable treatment for symptoms related to cervical disc degeneration and offers similar or superior outcomes compared with fusion. 2.

Effect of Disc Height and Degree of Distraction on Heterotopic Ossification After Cervical Disc Replacement

Heterotopic ossification (HO) is a potential and severe complication of cervical disc replacement (CDR). However, the underlying mechanism of CDR and its association with preoperative disc height loss (DHL) and postoperative degree of distraction remain unclear. We hypothesized that DHL and postoperative degree of distraction could predict HO after CDR. Data were obtained from 127 patients who underwent single-level CDR with a minimum follow-up of 2 years. DHL and adjusted degree of distraction (ADD) were obtained from lateral radiographs, and HO was evaluated at the last follow-up appointment. Receiver operating characteristic curves were calculated to verify the diagnostic value of DHL and ADD in predicting HO. Both DHL and ADD were significantly larger in the HO group than in the non-HO group (P < 0.05). DHL ≥24.97% increased the risk of HO by 5 times (P= 0.003, 95% confidence interval 1.62-15.49), and ADD ≥36.67% increased the risk of HO by 3.87 times (P < 0.001, 95% confidence interval 1.81-8.27). A combined DHL and ADD (combined parameter) cutoff of 60.36 had a sensitivity of 87.18%, specificity of 67.35%, and area under the curve of 0.77 for predicting HO. DHL and ADD are associated with the development of HO after CDR. The cutoff value of DHL may narrow the criteria for CDR with the aim of reducing HO formation. The combined parameter may help surgeons to select the most suitable implant height to reduce the prevalence of HO.

Impact of heterotopic ossification after single-level cervical disc replacement on adjacent segment

Objective: To investigate the impact of heterotopic ossification (HO) after cervical disc replacement (CDR) on clinical outcome and radiological outcome of adjacent segment. Methods: The data of patients underwent single-level Prestige-LP CDR between January 2008 and March 2014 in West China Hospital with a minimum 36 months of follow-up were retrospectively analyzed in this study. The incidence of HO, whether it affected clinical outcome, and its impact on adjacent segment intervertebral disc height (IDH), range of motion (ROM) and adjacent segment degeneration were observed. The data were compared with independent sample t test between the two groups. Results: Ninety-two patients were included in this study, including 48 males and 44 females, the mean age was (44±8) years, and the mean follow-up was (62±23) months. At the final follow-up, 34 patients developed HO after CDR, but the incidence of Grade 4 HO was 7.6%. In both of the HO and non-HO groups, clinical outcomes at the final follow-up were all significantly improved when compared to those before the operation. And there was no significant differences in any clinical indexes between the HO and non-HO groups. The adjacent segment IDH before operation and at the final follow-up in the HO group and non-HO group were similar(t=0.596, 0.825 and t=0.877, 0.644, all P>0.05). The preoperative adjacent segment ROM of HO group was similar with that in non-HO group(t=0.056, 0.709, both P>0.05), but the adjacent segment ROM in HO group was higher than that in the non-HO group at the final follow-up (upper adjacent segment: 10.0°±2.0° vs 9.0°±1.3°; lower adjacent segment: 10.2°±1.9° vs 8.8°±1.3°, t=2.824, 4.022, both P<0.05). The incidence of adjacent segment degeneration of HO group was higher than that of non-HO group at the final follow-up(41.2% vs 19.0%, χ(2)=5.343, P<0.05). Conclusions: HO is a common phenomenon in the long-term follow-up after the CDR operation with Prestige LP prosthesis, but HO does not affect the improvement of clinical outcome. HO after CDR might be one of important risk factors accelerating adjacent segment degeneration.

123 - The Cost-Effectiveness of Single-Level Cervical Disc Replacement vs Anterior Cervical Discectomy and Fusion: A Markov Analysis

123 - The Cost-Effectiveness of Single-Level Cervical Disc Replacement vs Anterior Cervical Discectomy and Fusion: A Markov Analysis

Investigating the 7-Year Cost-Effectiveness of Single-Level Cervical Disc Replacement Compared to Anterior Cervical Discectomy and Fusion.

Study Design:Cost-effectiveness analysis.Objectives:To determine the 7-year cost-effectiveness of cervical disc replacement (CDR) and anterior cervical discectomy and fusion (ACDF).Methods:We analyzed 7-year Short Form-36 Health Survey data collected from the Prestige Cervical Disc investigational device exemption study (IDE). The SF-6D algorithm was used to convert this data into health state utilities. Costs were calculated from the payer perspective, and quality adjusted life years (QALYs) were used to represent effectiveness. A Markov transition-state model was used to evaluate the cost-effectiveness of single-level CDR versus ACDF, and a Monte Carlo simulation was performed to assess the probabilistic sensitivity of the model.Results:CDR generated a 7-year cost of $172 989 compared to a 7-year cost of $143 714 for ACDF. CDR generated 4.53 QALYs compared to 3.85 QALYs generated by ACDF. The cost-effectiveness ratio of CDR was $38 247/QALY, while the cost-effectiveness ratio of ACDF was $37 325/QALY. The incremental cost-effectiveness ratio of CDR was $43 522/QALY, under the willingness to pay threshold of $50 000/QALY. Our probabilistic sensitivity analysis demonstrated CDR would be chosen 56% of the time based on 10 000 simulations.Conclusions:Single-level CDR and ACDF were both cost-effective strategies at 7 years for treating degenerative conditions of the cervical spine. Both the Markov simulation and the Monte Carlo simulation demonstrate CDR to be the more cost-effective strategy at 7 years. Continued analysis of IDE data should be performed to validate long-term cost-effectiveness of these treatment strategies.

Thirty-day readmission and reoperation rates after single-level anterior cervical discectomy and fusion versus those after cervical disc replacement.

OBJECTIVE The goal of this study was to compare 30-day readmission and reoperation rates after single-level anterior cervical discectomy and fusion (ACDF) versus those after cervical disc replacement (CDR). METHODS The authors used the 2013-2014 American College of Surgeons National Surgical Quality Improvement Program database. Included were adult patients who underwent first-time single-level ACDF or CDR for cervical spondylosis or disc herniation. Primary outcome measures were readmission and/or reoperation within 30 days of the original surgery. Logistic regression analysis was used to assess the independent effect of the procedure (ACDF or CDR) on outcome, and results are presented as odds ratios with 95% confidence intervals. RESULTS A total of 6077 patients met the inclusion criteria; 5590 (92.0%) patients underwent single-level ACDF, and 487 (8.0%) patients underwent CDR. The readmission rates were 2.6% for ACDF and 0.4% for CDR (p = 0.003). When stratified according to age groups, only patients between the ages of 41 and 60 years who underwent ACDF had a significantly higher readmission rate than those who underwent CDR (2.5% vs 0.7%, respectively; p = 0.028). After controlling for patient age, sex, body mass index, smoking status, history of chronic obstructive pulmonary disease (COPD), diabetes, hypertension, steroid use, and American Society of Anesthesiologists (ASA) class, patients who underwent CDR were significantly less likely to undergo readmission within 30 days than patients who underwent ACDF (OR 0.23 [95% CI 0.06-0.95]; p = 0.041). Patients with a history of COPD (OR 1.97 [95% CI 1.08-3.57]; p = 0.026) or hypertension (OR 1.62 [95% CI 1.10-2.38]; p = 0.013) and those at ASA Class IV (OR 14.6 [95% CI 1.69-125.75]; p = 0.015) were significantly more likely to require readmission within 30 days. The reoperation rates were 1.2% for ACDF and 0.4% for CDR (p = 0.086), and multivariate analysis revealed that CDR was not associated with lower odds of reoperation (OR 0.60 [95% CI 0.14-2.55]; p = 0.492). However, increasing age was associated with a higher risk (OR 1.02 [95% CI 1.00-1.05]; p = 0.031) of reoperation; a 2% increase in risk per year of age was found. CONCLUSIONS Patients who underwent single-level ACDF had a higher readmission rate than those who underwent single-level CDR in this study. When stratified according to age, this effect was seen only in the 41- to 60-year age group. No significant difference in the 30-day single-level ACDF and single-level CDR reoperation rates was found. Although patients in the ACDF group were older and sicker, other unmeasured covariates might have accounted for the increased rate of readmission in this group, and further investigation is encouraged.

Two-level cervical disc replacement: perspectives and patient selection

Two-level cervical disc replacement: perspectives and patient selection Ankur S Narain,&nbsp;Fady Y Hijji,&nbsp;Daniel D Bohl,&nbsp;Kelly H Yom,&nbsp;Krishna T Kudaravalli,&nbsp;Kern Singh Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA Introduction: Cervical disc replacement (CDR) is an emerging treatment option for cervical degenerative disease. Postulated benefits of cervical disc replacement compared to anterior cervical discectomy and fusion include preserved motion at the operative segments and decreased motion at adjacent levels. Multiple studies have been performed investigating the outcomes of CDR in single-level pathology. The investigation of the use of CDR in two-level pathology is an emerging topic within the literature.Purpose: To critically evaluate the literature regarding two-level CDR in order to determine its utility compared to two-level cervical arthrodesis. Patient selection factors including indications and contraindications will also be explored.Methods: The PubMed database was searched for all articles published on the subject of two-level CDR up until October 2016. Studies were classified by publication year, study design, sample size, follow-up interval, and conflict of interest. Outcomes were recorded from each study, and included data on patient-reported outcomes, radiographic measurements, range of motion, peri- and postoperative complications, heterotopic ossification, adjacent segment disease, reoperation rate, and total intervention cost. Results: Fourteen studies were included in this review. All studies demonstrated at least noninferiority of two-level CDR compared to both two-level arthrodesis and single-level CDR. Patient selection in two-level CDR is driven by the inclusion and exclusion criteria presented in prospective, randomized controlled trials. The most common indication is subaxial degenerative disc disease over two contiguous levels presenting with radiculopathy or myelopathy. Furthermore, costs analyses trended toward at least noninferiority of two-level CDR.Conclusion: Two-level CDR is noninferior to two-level anterior cervical discectomy and fusion in terms of both outcomes and costs. While a few studies suggested superiority of two-level CDR, the presence of significant conflicts of interest by the study authors may introduce bias. Further prospective, randomized trials without conflicts of interest are necessary to determine if two-level CDR demonstrates truly superior outcomes. Keywords: cervical disc replacement, anterior cervical discectomy and fusion, two-level, patient selection, outcomes, conflict of interest

Collective commentaries regarding two articles disputing value of cervical disc arthroplasty vs. Anterior cervical diskectomy and fusion.

Collective commentaries regarding two articles disputing value of cervical disc arthroplasty vs. Anterior cervical diskectomy and fusion.

Cost-effectiveness analysis: comparing single-level cervical disc replacement and single-level anterior cervical discectomy and fusion

In recent years, there has been increased interest in the use of cervical disc replacement (CDR) as an alternative to anterior cervical discectomy and fusion (ACDF). While ACDF is a proven intervention for patients with myelopathy or radiculopathy, it does have inherent limitations. Cervical disc replacement was designed to preserve motion, avoid the limitations of fusion, and theoretically allow for a quicker return to activity. A number of recently published systematic reviews and randomized controlled trials have demonstrated positive clinical results for CDR, but no studies have revealed which of the 2 treatment strategies is more cost-effective. The purpose of this study was to evaluate the cost-effectiveness of CDR and ACDF by using the power of decision analysis. Additionally, the authors aimed to identify the most critical factors affecting procedural cost and effectiveness and to define thresholds for durability and function to focus and guide future research. The authors created a surgical decision model for the treatment of single-level cervical disc disease with associated radiculopathy. The literature was reviewed to identify possible outcomes and their likelihood following CDR and ACDF. Health state utility factors were determined from the literature and assigned to each possible outcome, and procedural effectiveness was expressed in units of quality-adjusted life years (QALYs). Using ICD-9 procedure codes and data from the Nationwide Inpatient Sample, the authors calculated the median cost of hospitalization by multiplying hospital charges by the hospital-specific cost-to-charge ratio. Gross physician costs were determined from the mean Medicare reimbursement for each current procedural terminology (CPT) code. Uncertainty as regards both cost and effectiveness numbers was assessed using sensitivity analysis. In the reference case, the model assumed a 20-year duration for the CDR prosthesis. Cervical disc replacement led to higher average QALYs gained at a lower cost to society if both strategies survived for 20 years ($3042/QALY for CDR vs $8760/QALY for ACDF). Sensitivity analysis revealed that CDR needed to survive at least 9.75 years to be considered a more cost-effective strategy than ACDF. Cervical disc replacement becomes an acceptable societal strategy as the prosthesis survival time approaches 11 years and the $50,000/QALY gained willingness-to-pay threshold is crossed. Sensitivity analysis also indicated that CDR must provide a utility state of at least 0.796 to be cost-effective. Both CDR and ACDF were shown to be cost-effective procedures in the reference case. Results of the sensitivity analysis indicated that CDR must remain functional for at least 14 years to establish greater cost-effectiveness than ACDF. Since the current literature has yet to demonstrate with certainty the actual durability and long-term functionality of CDR, future long-term studies are required to validate the present analysis.

Sagittal Alignment After Single Cervical Disc Arthroplasty

Prospective study. To analyze the sagittal balance after single-level cervical disc replacement (CDR) and range of motion (ROM). To define clinical and radiologic parameters those have a significant correlation with segmental and overall cervical curvature after CDR. Clinical outcomes and ROM after CDR with Mobi-C (LDR, Troyes, France) prosthesis have been documented in few studies. No earlier report of this prosthesis has studied correlations between static and dynamic parameters or those between static parameters and clinical outcomes. Forty patients were evaluated. Clinical outcome was assessed using the Short Form-36 questionnaire, Neck Disability Index, and a Visual Analog Scale. Spineview software (Surgiview, Paris, France) was used to investigate sagittal balance parameters and ROM. The mean follow-up was 24.3 months (range: 12 to 36 mo). Clinical outcomes were satisfactory. There was a significant improvement of Short Form-36, Neck Disability Index, and Visual Analog Scale scores. Mean ROM was 8.3 degrees preoperatively and 11.0 degrees postoperatively (P=0.013). Mean preoperative C2C7 curvature was 12.8 and 16.0 degrees at last follow-up (P=0.001). Mean preoperative functional spinal unit (FSU) angle was 2.3 and 5.3 degrees postoperatively (P<0.0001). Mean postoperative shell angle was 5.5 degrees. There was a significant correlation between postoperative C2C7 alignment and preoperative C2C7 alignment, change of C2C7 alignment, preoperative and postoperative FSU angle, and prosthesis shell angle. There was also a significant correlation between postoperative FSU angle and preoperative C2C7 alignment, preoperative FSU angle, change of FSU angle, and prosthesis shell angle. Regression analysis showed that prosthesis shell angle and preoperative FSU angle contributed significantly to postoperative FSU angle. Moreover, preoperative C2C7 alignment, preoperative FSU angle, postoperative FSU angle, and prosthesis shell angle contributed significantly to postoperative C2C7 alignment. No significant correlation was observed between ROM and sagittal parameters. Few correlations were found between sagittal alignment and clinical results. CDR with this prosthesis provided favorable clinical outcomes and maintains ROM of the FSU, overall and segmental cervical alignment. Long-term follow-up will be needed to assess the effectiveness and advantages of this procedure.

Analysis of the incidence and clinical effect of the heterotopic ossification in a single-level cervical artificial disc replacement

Background context Heterotopic ossification (HO) is a well-known phenomenon occurring after joint arthroplasty. However, its incidence and clinical effects have not yet been clearly identified with cervical disc replacement. Purpose The first aim of this study was to evaluate the incidence of HO in single-level cervical disc replacement. The second aim was to identify the relationship of HO with clinical outcomes and radiological findings. Study design A retrospective study of 48 patients who underwent single-level artificial disc replacement in one of our clinics. Patient sample Between November 2004 and December 2008, 48 consecutive patients underwent single-level cervical artificial disc replacement in Seoul Wooridul Hospital, Seoul, Korea. Outcomes measures Clinical outcomes were graded using visual analog scale (VAS) scores (score range, 0–10, with 0 reflecting no pain). Functional outcomes were measured using Oswestry Disability Index (ODI) scores. Radiological outcomes were evaluated with follow-up dynamic X-ray. Methods Occurrence of HO was investigated with the McAfee classification on the follow-up cervical dynamic X-ray. We also measured cervical range of motion (ROM) to identify HO's biomechanical effects. For the clinical effects, the VAS and the ODI were evaluated in correlation with the occurrence of HO. Results In 48 treated patients, a total of 13 HOs were detectable. Grade 1 and 2 HO occurred in 11 patients and Grade 3 HO in two patients. Mean occurrence of HO was observed on the 11th month after the surgery. HO that led to the restriction of the ROM was not present in any patients. The clinical outcome was not significantly correlated with the occurrence of HO. Conclusions The overall incidence of HO after cervical artificial disc replacement was relatively high. However, Grade 3 and 4 HO that limit the ROM rarely occurred. Moreover, the occurrence of HO did not affect the clinical symptoms and biomechanical dynamics. A longer follow-up with a larger group of patients should be undertaken, which may demonstrate a higher rate of HO and long-term effects on the ROM.

Analysis of Segmental Cervical Spine Vertebral Motion After Prodisc-C Cervical Disc Replacement

Retrospective study of patients enrolled in a prospective randomized Food and Drug Administration trial with single level cervical disc replacement (CDR) with the ProDisc-C (Synthes, Paoli, PA). Evaluate the segmental range of motion (ROM) in the cervical spine pre- and postoperative after CDR. Each cervical level is believed to have its own biomechanical characteristics, ultimately leading to different sagittal and lateral ROM. Our understanding of the factors that influence motion after CDR continues to change and expand. One hundred sixty-four patients with single level ProDisc-C arthroplasty were evaluated radiographically using Medical Metrics (QMATM, Medical Metrics, Inc., Houston, TX). Pre- and postoperative disc height and ROM were measured from standing lateral and flexion-extension radiographs. Of these 164 patients, 44 had a CDR at C6/C7, 96 at C5/C6, 18 at C4/C5, and 6 at C3/C4. The mean follow-up was of 24 months. Statistical analysis evaluated the difference in mean ROM between the groups. Before surgery, C4/C5 had more sagittal ROM compared with C3/C4, C5/C6, and C6/C7 (P < 0.001.) Before surgery, C4/C5 also had more lateral ROM compared with C3/C4, C5/C6, and C6/C7 (P = 0.015). After surgery, there were no significant differences in sagittal and lateral ROM between C3/C4, C4/C5, C5/C6, and C6/C7. The delta (difference between pre- and postoperative) proved that the C4/C5 CDR actually lost sagittal ROM (-2.5 degrees ) compared with the other levels, which gained sagittal ROM, C3/C4 (0.9 degrees ), C5/C6 (1.8 degrees ), and C6/C7 (1.6 degrees ); P = 0.037. There was no significant difference in the delta lateral ROM between the segments: C3/C4, C4/C5, C5/C6, and C6/C7. CDR approximates the different segmental sagittal and lateral ROM. Although C4/C5 had negative delta ROM in the sagittal and lateral planes, it provided a satisfactory final ROM. Long-term clinical outcome studies are needed to properly evaluate if these differences could ultimately affect the patients everyday life.

Superiority of Multilevel Cervical Arthroplasty Outcomes Versus Single-Level Outcomes

Class 2 level of evidence: This is a prospective, consecutive series of 229 prosthetic implantations that were concurrently enrolled between single-level versus multilevel cervical arthroplasty comprising an FDA Pilot Study. This study investigated multilevel cervical disc replacement in relation to single-level cervical arthroplasty to find if the same reduction in clinical success would occur with this alternative treatment. Usually, the clinical outcomes of instrumented cervical fusions deteriorate as the number of vertebral levels of involvement increases. A total of 229 patients presented with cervical herniated nucleus pulposus, cervical spondylosis, and/or adjacent segment disease with cervical radiculopathy or myelopathy. Following anterior cervical neurologic decompression seventy-one patients required porous coated motion (PCM) cervical arthroplasties from C3-C4 to C7-T1 (Group S, single level). Sixty-nine patients underwent 158 multilevel PCM cervical arthroplasties (Group M, multilevel) during the same time interval, for the same indications, performed by the same surgeons under the same clinical protocol: double level, 53 cases; three levels, 12 cases: and 4 levels, 4 cases. The self-assessment outcomes instruments showed significantly more improvement for the multilevel cases. The mean improvement in the NDI for the single cases was 37.6% versus the multilevel cases mean improvement in NDI was 52.6% (P = 0.021). The difference between the two was statistically significant. The mean improvement in the VAS showed the same association: single-level mean improvement 58.4% versus the multilevel cases mean VAS improvement was 65.9%. The Odom's were also more improved for the multilevel versus the single-level group: 93.9% versus 90.5% in the excellent, good, and fair categories. The reoperation rates and serious adverse events were similar between the single-level (S = 3) to the multilevel arthroplasty (M = 2) groups. Kaplan-Meier implant survivorship analysis at 3 years for the cohort of 229 prostheses was 94.5% (confidence interval, 1.00-0.820). This prospective study of cervical arthroplasty is the first report to date showing significantly improved clinical outcomes for multilevel cervical arthroplasty compared with single-level cervical disc replacement using an FDA validated outcome instrument.

6:12 170. Comparison of multiple level vs. single level cervical disc replacement: 178 consecutive prostheses

6:12 170. Comparison of multiple level vs. single level cervical disc replacement: 178 consecutive prostheses