Cervical Artificial Disc Replacement Research Articles

Countermeasure of surgical position for patients of cervical artificial disc replacement

Objective To make a conclusion about the methods and main points of surgical position for cervical artificial disc replacement (CADR) . Methods We collected the data from January to December 2015 in West China Hospital of Sichuan University. It included 102 patients in the surgical group of cervical spine, which were cervical vertebra degeneration and doing CADR according to the segment, quantity of the replacement and whether belonged to hybrid surgical method, then we analyzed and determined how to achieve the desired surgical position. Results The surgical positions of the patients in this group all conformed to the requirements of the replacement and gave intraoperative excellent exposure and less blood loss, made the vision of decompression clear and thorough, made the position of replacement prosthesis great. There were no postoperative complications. The patients all healed and were discharged in 5 to 7 days after operation. There was no position offset of prosthesis and no extrusion in the following 6 to 18 months. It restored the ideal physiological lordosis of the cervical spine. Conclusions According to the different segment of the replacement, we analyze and remain the location of the preoperative cervical spinal neutrality and a bit of extension which make the artificial cervical disc in favor of being well placed during an operation and promote cervical spine to maintain normal physiological lordosis during early post-operation, and greatly reduce the incidence of postoperative pain of neck and shoulder. Key words: Cervical vertebrae surgery; Artificial cervical disc; Replacement; Surgical position; Settle

Clinical and Radiological Analysis of Bryan Cervical Artificial Disc Replacement for "Skip" Multi-Segment Cervical Spondylosis: Long-Term Follow-Up Results.

BackgroundThe aim of this study was to retrospectively analyze the clinical and radiological efficacy of Bryan cervical artificial disc replacement (ADR) for “skip” multi-segment cervical spondylosis (SCS).Material/MethodsWe enrolled 49 patients with SCS treated with either Bryan cervical ADR (18 cases) or ACDF (31 cases). Each case was evaluated preoperatively and at more than 48 months postoperatively in follow-up using the JOA, NDI, and VAS. Cervical sagittal curvature, total cervical ROM, and degree of middle segments of motion were also evaluated. MRI was used to assess adjacent segment degeneration(ASD), spinal cord compression, and signal changes.ResultsThe JOA, NDI, and VAS scores in the 2 groups improved significantly postoperatively. At the last follow-up, the results of Group Bryan were better than those of Group ACDF with respect to the incidence of axial symptoms (11.1% and 45.2%, respectively), VAS, ROM, and the degree of middle segments of motion. The ROM in Group Bryan was 38.2±4.6° and in Group ACDF was 25.3±4.6°. The middle segments of motion were 8.4±2.0° in Group Bryan and 12.2±2.2° in Group ACDF. There were no patients with ASD in Group Bryan. In Group ACDF, 1 case with an internal fixation device developed dislocation, and 2 cases developed degeneration, but there was no need for reoperation.ConclusionsADR for SCS can effectively improve neurological function and retain the overall activity of the cervical, thereby reducing ASD and the incidence of postoperative axial symptoms.

How to choose when implants of adjacent height both fit the disc space properly in single-level cervical artificial disc replacement.

In cervical artificial disc replacement (C-ADR), sometimes we encountered with such cases that implants of adjacent height both fit the target disc space properly. No study was available discussing the choice of implant height and the clinical outcomes under such circumstance. The purpose of this study was to evaluate the impact of different implant heights on the clinical outcomes and radiographic results when the implants of adjacent height both fit the disc space properly. This retrospective study included 34 patients underwent single-level C-ADR at the C5–C6 level at our institution. In these 34 patients, implant with either 5 mm height or 6 mm height fit the surgical level properly without overstretching the disc space or the facet joint space. Clinical outcomes were evaluated using the Japanese Orthopedic Association score, visual analog scale (VAS), and Neck Disability Index. Radiographic assessments were conducted on static and dynamic radiographs for the determination of the disc space height, intersegmental range of motion (ROM), and the ROM of the functional spinal unit (FSU) at the surgical level. The baseline information of the patients, such as age, gender, weight, follow-up time, and diagnosis, was similar between the 2 groups (P > .05). Postoperative mean VAS in group B was significantly lower than that in group A (2.1 ± 0.7 vs. 2.7 ± 1.0, P < .05). The mean VAS decrease in group B was significantly larger than that in group A (5.3 ± 0.8 vs. 4.6 ± 1.1, P < .05). Significant difference was found in the postoperative disc height of the surgical segment between the 2 groups (6.4 ± 0.4 mm vs. 7.5 ± 0.5 mm, P < .05). No significant differences were noted in the intersegmental ROM and ROM of the FSU between the 2 groups both before the surgery and at the last follow-up (P > .05). No hypermobility or instability was observed in these patients. Our results suggested that when implants of adjacent height both fit the disc space properly, using the larger implant could result in better pain relief without the risk of segmental hypermobility in patients underwent single-level C-ADR at the C5–C6 level.

Artificial Cervical Disk Replacement for the Treatment of Adjacent Segment Disease After Anterior Cervical Decompression and Fusion.

Retrospective study. To evaluate the outcome of artificial cervical disk replacement (ACDR) for the treatment of adjacent segment disease (ASD) after anterior cervical decompression and fusion (ACDF). ACDF is the useful procedure for degenerative cervical diseases. However, studies have reported accelerated degeneration of functional spinal units adjacent to the fusion site after ACDF. Between January 2004 and January 2011, 32 inpatients (18 male, 14 female; age, 38-61 y; mean, 48 y) underwent ACDR for the treatment of ASD after previous ACDF (single-level: n=12; 2-level: n=15; 3-level: n=5). In 22 patients, ASD occurred above the fusion site, and in 10 it occurred below the site. After ACDR, the patients were followed up for 30-62 months (mean, 49 mo). Before and after ACDR, patients were evaluated using the pain visual analog scale (VAS), the Japanese Orthopedic Association (JOA) score, and neck disability index (NDI). In addition, the range of motion (ROM) of the replaced and adjacent unfused segments was measured by flexion/extension lateral radiography. Periprosthetic heterotopic ossification was detected using McAfee's classification. Degeneration of the adjacent unfused segment was evaluated using Goffin scale. All patients had successful surgery. Before ACDR, neck VAS, upper-limb VAS, JOA score, and NDI were 7.2±1.8, 6.9±1.1, 9.8±2.5, and 40.5±4.8, respectively. At the last follow-up, they were 1.2±0.3, 0.9±0.3, 14.5±1.1, and 9.0±2.5, respectively. Compared with presurgery, the improvements in VAS, JOA score, and NDI at the final follow-up were statistically significant (all P<0.05). During follow-up, prosthesis positioning was satisfactory without migration or downward movement. Preoperatively, the ROMs of the replaced and adjacent segments were 8.7±2.6 and 7.6±3.0, respectively. At the last follow-up, they were 8.5±2.2 and 7.2±2.6, respectively (both P>0.05). At the last follow-up, 2 patients had grade II heterotopic ossification; 3 patients had aggravated degeneration (vs. preoperative status) of the adjacent unfused segment. However, the reduction in Goffin grade was not statistically significant. Our follow-up shows that ACDR is an effective treatment for post-ACDF ASD. It can maintain the ROMs of the replaced segment as well as the adjacent unfused segment.

Analysis of the Factors That Could Predict Segmental Range of Motion After Cervical Artificial Disk Replacement: A 7-Year Follow-up Study.

A retrospective cohort study. To identify the potential preoperative factors and surgical technique factors that are associated with long-term range of motion (ROM) after surgery. Further, this article aimed to guide selection of patients with cervical artificial disk replacement and a fine surgical technique. Segmental ROM is the most important parameter concerning cervical kinematics after a cervical artificial disk replacement. There are few researches regarding the influencing factors on postoperative ROM, and consistent results have not yet been reported. The cohort comprised a total of 68 disks implanted into 57 patients who were retrospectively analyzed. The mean follow-up period was 84.1 months. Segmental ROM and other useful parameters were measured using lateral neutral, extension, and flexion radiographs, which were obtained preoperatively, 3 months after surgery, and at last follow-up. Preoperative CT and clinical assessment were also used. To find out associated factors, the patients were divided into 2 groups according to the segmental ROM at last follow-up. After surgery, the clinical outcomes were satisfactory. The segmental ROM at last follow-up (7.8±4.3 degrees) was preserved without significant change from preoperative ROM (8.8±3.8 degrees). The patients who had a better segmental ROM after surgery were found to have a higher preoperative segmental ROM, a younger age, a better disk insertion angle, and disk insertion depth. These 4 factors were identified as independent risk factors (P=0.027, 0.017, 0.036, and 0.046, respectively) for long-term ROM. The postoperative long-term, segmental ROM was well preserved and found to be affected by the preoperative segmental ROM, patient's age, disk insertion angle, and disk insertion depth.

The prevalence of heterotopic ossification among patients after cervical artificial disc replacement: A systematic review and meta-analysis.

Background:Prevalence estimates of heterotopic ossification (HO) following cervical artificial disc replacement (ADR) varied widely in previous studies. We conducted a systematic review and meta-analysis to summarize its point prevalence.Methods:Electronic searches of PubMed, Web of Science, Embase, and Cochrane Library databases were conducted to identify studies that reported prevalence of HO. Definitions of HO and severe HO were based on McAfee grading system. Random-effects model was used to estimate the pooled prevalence. We conducted subgroup analyses according to the different length of follow-up time, and performed univariate metaregression analyses to explore the effects of potential variables on the overall prevalence.Results:A total of 38 studies were included in this study. The pooled data showed that the prevalence of HO after cervical ADR within the 1 to 2 years, 2 to 5 years, and 5 to10 years of follow-up was 38.0% (95% confidence interval [CI], 30.2%–46.5%), 52.6% (95% CI, 43.1%–61.9%), and 53.6% (95% CI, 40.0%–66.7%), respectively, while the prevalence of severe HO was 10.9% (95% CI, 9.0%–13.2%), 22.2% (95% CI, 15.5%–30.7%), and 47.5% (95% CI, 30.0%–65.8%), respectively. Follow-up time was positively associated with the prevalence of severe HO (P < .01), and the 1-month growth of mean follow-up went with 0.63% increase of severe HO.Conclusion:This meta-analysis reported data on the prevalence of HO and severe HO after cervical ADR, and provided information on its process of development. These should be useful to enable surgeons and patients to gain a better understanding of HO after cervical ADR.

Cervical Disk Replacement With Discover Versus Fusion in a Single-Level Cervical Disk Disease: A Prospective Single-Center Randomized Trial With a Minimum 2-Year Follow-up.

Prospective randomized study. To compare the clinical outcome after Discover arthroplasty versus anterior cervical discectomy and fusion (ACDF) in patients treated for symptomatic single-level cervical disk disease. ACDF is still the gold standard for surgical treatment of cervical spine degenerative disk disease. However, results of many studies suggest that it may cause degenerative changes at levels immediately above and below the fusion, known as adjacent segment degenerative disease. Cervical arthroplasty has recently been introduced as an alternative to standard procedure of ACDF. It showed decreased surgical morbidity, decreased complications from postoperative immobilization, and an earlier return to previous level of function. A total of 105 consecutive patients with single-level cervical disk disease, producing radiculopathy and/or myelopathy were randomly divided into groups to undergo ACDF or Discover arthroplasty. All patients were evaluated with preoperative and postoperative serial radiographic studies and clinically, using Neck Disability Index, Visual Analog Scale and neurological status at 3, 6, 12, and 24 months. The results of our study indicate that cervical arthroplasty using Discover Artificial Cervical Disc provides favorable clinical and radiologic outcomes in a follow-up period of 24 months. There has been significant improvement in clinical parameters, Visual Analog Scale and Neck Disability Index, at 3, 6, 12, and 24 months in arthroplasty group comparing to control group. The Discover artificial cervical disc replacement offers favorable outcome compared with ACDF for a single-level cervical disk disease at short-term and long-term follow-up.

A 6-DOF parallel bone-grinding robot for cervical disc replacement surgery.

Artificial cervical disc replacement surgery has become an effective and main treatment method for cervical disease, which has become a more common and serious problem for people with sedentary work. To improve cervical disc replacement surgery significantly, a 6-DOF parallel bone-grinding robot is developed for cervical bone-grinding by image navigation and surgical plan. The bone-grinding robot including mechanical design and low level control is designed. The bone-grinding robot navigation is realized by optical positioning with spatial registration coordinate system defined. And a parametric robot bone-grinding plan and high level control have been developed for plane grinding for cervical top endplate and tail endplate grinding by a cylindrical grinding drill and spherical grinding for two articular surfaces of bones by a ball grinding drill. Finally, the surgical flow for a robot-assisted cervical disc replacement surgery procedure is present. The final experiments results verified the key technologies and performance of the robot-assisted surgery system concept excellently, which points out a promising clinical application with higher operability. Finally, study innovations, study limitations, and future works of this present study are discussed, and conclusions of this paper are also summarized further. This bone-grinding robot is still in the initial stage, and there are many problems to be solved from a clinical point of view. Moreover, the technique is promising and can give a good support for surgeons in future clinical work.

Domestic artificial cervical disc interface pressure distribution and effect of bone-implant interface pressure on osseointegration

To analyze the distribution of stress in the upper and lower plates of the prosthesis-bone interface, and the effect of interface pressure on osseointegration. CT scanning was performed on goats at 1 week after artificial cervical disc replacement to establish the finite element model of C 3, 4. The stress distribution of the upper and lower plates of the interface was observed. At 6 and 12 months after replacement, Micro-CT scan and three dimensional reconstruction were performed to measure the bone volume fraction (BVF), trabecular number (Tb. N), trabecular thickness (Tb. Th), trabecular separation (Tb. Sp), bone mineral density (BMD), bone surface/bone volume (BS/BV), and trabecular pattern factor (Tb. Pf). The C 3 lower plate and C 4 upper plate of 4 normal goat were chosen to made the cylinder of the diameter of 2 mm. The gene expressions of receptor activator for nuclear factor κB ligand (RANKL), osteoprotegerin (OPG), transforming growth factor β (TGF-β), and macrophage colony-stimulating factor (M-CSF) were detected by real time fluorescent quantitative PCR at immediate after cutting and at 24 and 48 hours after culture. The samples of appropriate culture time were selected to made mechanical loading, and the gene expressions of RANKL, OPG, M-CSF, and TGF-β were detected by real time fluorescent quantitative PCR; no mechanical loading samples were used as normal controls. Under 25 N axial loading, the stress of the upper plate of C 3, 4 was concentrated to post median region, and the stress of the lower plate to middle-front region and two orbits. According to stress, the plate was divided into 5 regions. The Micro-CT scan showed that BMD, Tb.Th, BVF, and Tb.N significantly increased, and BS/BV, Tb.Sp, and Tb.Pf significantly decreased at 12 months after replacement when compared with ones at 6 months ( P<0.05). At 24 and 48 hours after culture, the gene expressions of RANKL, OPG, and TGF-β were signifi-cantly higher than those at immediate ( P<0.05), but no significant difference was found between at 24 and 48 hours after culture ( P>0.05). The mechanical loading test results at 24 hours after culture showed that the RANKL and OPG gene expressions and OPG/RANKL ratio in C 3 lower plate and C 4 upper plate were significantly up-regulated when compared with controls ( P<0.05), but no significant difference was shown in TGF-β and M-CSF gene expressions ( P>0.05). Domestic artificial cervical disc endplate has different pressure distribution, the stress of lower plate is higher than that of upper plate. Pressure has important effect on local osseointegration; the higher pressure area is, the osseointegration is better. Under the maximum pressure in interface, the osteoblast proliferation will increase, which is advantageous to the local osseointegration.

Long-term clinical and radiographic outcomes of the Prestige LP artificial cervical disc replacement at 2 levels: results from a prospective randomized controlled clinical trial.

OBJECTIVE The aim of this study was to assess long-term clinical safety and effectiveness in patients undergoing anterior cervical surgery using the Prestige LP artificial disc replacement (ADR) prosthesis to treat degenerative cervical spine disease at 2 adjacent levels compared with anterior cervical discectomy and fusion (ACDF). METHODS A prospective, randomized, controlled, multicenter FDA-approved clinical trial was conducted at 30 US centers, comparing the low-profile titanium ceramic composite-based Prestige LP ADR (n = 209) at 2 levels with ACDF (n = 188). Clinical and radiographic evaluations were completed preoperatively, intraoperatively, and at regular postoperative intervals to 84 months. The primary end point was overall success, a composite variable that included key safety and efficacy considerations. RESULTS At 84 months, the Prestige LP ADR demonstrated statistical superiority over fusion for overall success (observed rate 78.6% vs 62.7%; posterior probability of superiority [PPS] = 99.8%), Neck Disability Index success (87.0% vs 75.6%; PPS = 99.3%), and neurological success (91.6% vs 82.1%; PPS = 99.0%). All other study effectiveness measures were at least noninferior for ADR compared with ACDF. There was no statistically significant difference in the overall rate of implant-related or implant/surgical procedure-related adverse events up to 84 months (26.6% and 27.7%, respectively). However, the Prestige LP group had fewer serious (Grade 3 or 4) implant- or implant/surgical procedure-related adverse events (3.2% vs 7.2%, log hazard ratio [LHR] and 95% Bayesian credible interval [95% BCI] -1.19 [-2.29 to -0.15]). Patients in the Prestige LP group also underwent statistically significantly fewer second surgical procedures at the index levels (4.2%) than the fusion group (14.7%) (LHR -1.29 [95% BCI -2.12 to -0.46]). Angular range of motion at superior- and inferior-treated levels on average was maintained in the Prestige LP ADR group to 84 months. CONCLUSIONS The low-profile artificial cervical disc in this study, Prestige LP, implanted at 2 adjacent levels, maintains improved clinical outcomes and segmental motion 84 months after surgery and is a safe and effective alternative to fusion. Clinical trial registration no.: NCT00637156 (clinicaltrials.gov).

Generation and Development of Paravertebral Ossification in Cervical Artificial Disk Replacement: A Detailed Analytic Report Using Coronal Reconstruction CT.

A retrospective follow-up study and review of images in published papers. To determine whether true heterotopic ossification (HO) occurs in artificial disk replacement (ADR); to evaluate the incidence of paravertebral ossification (PO) and its influence on ADR. HO is typically defined as the abnormal formation of true bone within extraskeletal soft tissues. However, HO in ADR does not fit this definition precisely, as it originates from vertebral body, making it hard to distinguish radiologically from preexisting osteophytes. In this study, the term used for bone formation around ADR is PO. First, all images in the published papers were evaluated as to whether the presented PO in ADR fit the classic definition of HO or osteophytes. Second, we studied 37 consecutive patients who underwent ADR and follow-up for minimum 24 months. The preoperative and follow-up incidence of PO and its influence on range of motion were evaluated using x-ray and computed tomography. All 52 images of PO were found adjacent to the disk in 1 segment rather than entire cervical spine. Fifty (96.2%) of the POs were found to originate from the vertebral body rather than in the soft tissue. A total of 31 patients were included in the follow-up study. No significant difference was found in the incidence of PO between the follow-up and preoperation (61.29% vs. 48.39%, P>0.05). The range of motion of the ADR segment in patients with progressed PO (7.44±4.64 degrees) was significantly lower than that of patients with stable PO grade (12.13±4.42 degrees, P<0.01) at last follow-up. A proportion of HO might in fact be the natural development of preoperative osteophytes, which is unrelated to ADR; the remaining HO might be due to changes in biomechanical environment after surgery, which promotes the grade of osteophytes and affects the segment motion.

Taux de ré-intervention après arthrodèse cervicale antérieure versus prothèse discale à quatre ans de recul minimum. Meta-analyse des études prospectives randomisées

InstructionAnterior cervical discectomy and fusion (ACDF) is a well-accepted surgical management strategy for radiculopathy and/or myelopathy. However, complications sometimes required subsequent surgery at the operated and adjacent levels. Artificial cervical disc replacement (ACDR) has been accepted as the most extensive non-fusion procedure and is designed to preserve motion. However, some specific complications can result in subsequent surgery, thus attracting the attention of investigators. HypothesisCompared with ACDF, ACDR had a lower subsequent surgery rates at both operated and adjacent levels after a minimum of four-years of follow-up. Material and methodsA meta-analysis was performed with articles published prior to February 2016. Only randomized controlled trials that reported a minimum of 4 years of follow-up with regard to the rates of subsequent surgeries after ACDR compared with ACDF were included in this study. Two reviewers independently screened the articles and data following the PRISMA statement. ResultsOur data showed that the pooled overall rate of subsequent surgery at the operated level and adjacent levels was lower in the ACDR group (7.4 %) than in the ACDF group (16.8 %) (P=0.0006). For subsequent surgery at the operated level, patients who received ACDR had a lower rate of subsequent surgery than patients who received ACDF (P<0.0001). With respect to the adjacent level, ACDR also had fewer subsequent surgeries compared with ACDF (P<0.0001). ConclusionACDR had significantly fewer subsequent surgical interventions compared with ACDF. However, a review of the literature showed that there were an insufficient number of studies with respect to subsequent surgery with a minimum of 4 years of follow-up. Hence, longer-term, multicenter studies are needed for better evaluation of the rate of subsequent surgery after ACDR. Level of evidenceLevel I, meta-analysis of high-powered prospective randomized trials.

Artificial Cervical Disk Replacement at Three Levels Following Multilevel Cervical Diskectomy

Artificial Cervical Disk Replacement at Three Levels Following Multilevel Cervical Diskectomy

Minimum four-year subsequent surgery rates of cervical disc replacement versus fusion: A meta-analysis of prospective randomized clinical trials

InstructionAnterior cervical discectomy and fusion (ACDF) is a well-accepted surgical management strategy for radiculopathy and/or myelopathy. However, complications sometimes required subsequent surgery at the operated and adjacent levels. Artificial cervical disc replacement (ACDR) has been accepted as the most extensive non-fusion procedure and is designed to preserve motion. However, some specific complications can result in subsequent surgery, thus, attracting the attention of investigators. HypothesisCompared with ACDF, ACDR had a lower subsequent surgery rates at both operated and adjacent levels after a minimum of four-years of follow-up. Material and methodsA meta-analysis was performed with articles published prior to February 2016. Only randomized controlled trials that reported a minimum of 4 years of follow-up with regard to the rates of subsequent surgeries after ACDR compared with ACDF were included in this study. Two reviewers independently screened the articles and data following the PRISMA statement. ResultsOur data showed that the pooled overall rate of subsequent surgery at the operated level and adjacent levels was lower in the ACDR group (7.4%) than in the ACDF group (16.8%) (P=0.0006). For subsequent surgery at the operated level, patients who received ACDR had a lower rate of subsequent surgery than patients who received ACDF (P<0.0001). With respect to the adjacent level, ACDR also had fewer subsequent surgeries compared with ACDF (P<0.0001). ConclusionACDR had significantly fewer subsequent surgical interventions compared with ACDF, However, a review of the literature showed that there were an insufficient number of studies with respect to subsequent surgery with a minimum of 4 years of follow-up. Hence, longer-term, multicenter studies are needed for better evaluation of the rate of subsequent surgery after ACDR. Level of evidenceLevel I, meta-analysis of high-powered prospective randomized trials.

Artificial cervical disc replacement with the Prestige-LP prosthesis for the treatment of non-contiguous 2-level cervical degenerative disc disease: A minimum 24-month follow-up

ObjectiveWe describe the features of non-contiguous 2-level cervical degenerative disc disease (NCDDD), investigate the safety and feasibility of artificial cervical disc replacement (ACDR) for the treatment of NCDDD, and expect that our study will provide spine surgeons with an alternative procedure for NCDDD. MethodsTwenty-five patients with NCDDD received ACDR with a Prestige-LP prosthesis. Clinical outcomes were evaluated using the 36-Short Form (SF-36, Mental Component Summary [MCS] and Physical Component Summary [PCS]), Visual Analog Scale (VAS), Japanese Orthopedic Association (JOA), and Neck Disability Index (NDI) scores. Radiographic evaluations included cervical lordosis (CL), range of motion (ROM), and disc height (DH). Data regarding complications were collected as well. ResultsThe mean follow-up period was 32.24 months. Clinical outcomes, including SF-36 MCS and PCS, VAS, JOA, and NDI scores significantly improved at the 24-month follow-up (p<0.05). There were no significant differences in CL and ROM at the 24-month follow-up (p>0.05). Although there was a significant difference between the before and 3-month follow-up (p<0.05), the ROM of the intermediate segment (IS) showed a tendency of returning to the preoperative state. The DH of the IS was maintained at each measurement while the DH of the upper and lower operated segments significantly increased at the 24-month follow-up (p<0.05). One patient, whose prosthesis remained mobile at the last follow-up, showed evidence of heterotopic ossification (HO). ConclusionACDR with the Prestige-LP prosthesis is a safe and feasible alternative procedure for treatment of NCDDD. In the future, a large-sample, prospective randomized controlled study with long-term follow-up will be needed to further demonstrate noncontiguous ACDR as an optimal surgical option for NCDDD.

An Analysis of Paravertebral Ossification in Cervical Artificial Disc Replacement: A Novel Classification Based on Computed Tomography.

Cervical artificial disc replacement (CADR) is a new technology in cervical spine surgery. However, CADR may result in paravertebral ossification (PO) after surgery and affect the mobility of the related spinal segments. The present widely used assessment method based on X-ray tomography cannot provide the position information of PO, and also PO detection rates by X-ray are low. The incidence of PO varies dramatically between studies. This study built a novel classification system based on cervical computer tomography (CT) scan to re-evaluate the incidence of PO and its influence on CADR, and also analyzed the predisposing factors of PO. In this retrospective study, 71 patients (from January 2004 to December 2009) who received cervical artificial disc replacement in our hospital were enrolled, and 82 cervical segments were replaced by Bryan discs. The range of motion (ROM) of the related cervical segments and scores of neurological symptoms (neck disability index [NDI] and Japanese Orthopaedic Association [JOA] scores) for both pre-surgery and last follow-up were acquired, respectively. After the establishment of a novel grading system for PO based on CT scan, we analyzed the CT images acquired before surgery and at the last time follow-up. Occurrence and distribution of PO at both time points were calculated. ROM between pre-surgery and post-surgery was compared by paired t-test stratified by PO stages. One-way ANOVA was used to compare NDI and JOA scores between high-grade and low-grade PO groups after surgery. The χ2 -test was used to evaluate the risk (odds ratio) of predisposing factors in developing high-grade PO after surgery. The CT-based classification system has good inter-observer and intra-observer reliability. The detection rate of PO by CT scan is higher than for traditional X-ray examination. The incidence of low-grade PO in all 82 segments at last follow-up is 32.9%. The occurrences of high-grade PO at preoperational and last follow-up time are 15.9% and 67.1%, respectively. The high-grade PO is mainly distributed around the uncovertebral joint. The pre-surgery and post-surgery ROM are similar in patients with low-grade PO at last follow-up time (9.80° ± 3.65° vs 10.03° ± 3.73°, P = 0.801); however, in patients with high-grade PO the post-surgery ROM decreases significantly compared to the pre-surgery ROM (9.73° ± 4.03° vs 6.63° ± 4.21°, P < 0.001). There is no statistical difference for JOA and NDI scores after surgery between high-grade and low-grade PO patients at final follow-up (P = 0.264, P = 0.703). The χ2 -test indicates that patients with preoperational existence of PO have a high risk of high-grade PO after surgery (OR = 4, P = 0.012). The novel CT image-based PO classification system has good intra-observer reliability. The incidence of PO after Bryan cervical disk replacement is relative high, and the high-grade PO is mainly distributed at the uncovertebral joint. The high-grade PO will affect the ROM after surgery; however, it does not affect the neurologic symptoms.

345 Elective Anterior Cervical Discectomy and Fusion vs Cervical Artificial Disc Replacement

INTRODUCTION:We conducted a retrospective cohort analysis of early outcomes after elective anterior cervical discectomy and fusion (ACDF) vs cervical artificial disc replacement (C-ADR) using the National Surgical Quality Improvement Program database. Risk factors associated with operation time, hos

Comparison of the incidence of patient-reported post-operative dysphagia between ACDF with a traditional anterior plate and artificial cervical disc replacement

PurposeCompared with anterior cervical discectomy and fusion (ACDF), cervical disc replacement (CDR) has provided satisfactory clinical results. The incidence of post-operative dysphagia between ACDF with a traditional anterior plate and CDR remains controversial. Considering the limited studies and knowledge in this area, a retrospective study focusing on post-operative dysphagia was conducted. MethodsThe Bazaz grading system was used to assess the severity of dysphagia at post-operative intervals including 1 week, 1 month, 3 months, 6 months, 12 months and 24 months respectively. The Chi-square test, Student t-test, Mann-Whitney U tests and Ordinal Logistic regression were used for data analysis when appropriate. Statistical significance was accepted at a probability value of <0.05. ResultsTwo hundred and thirty-one patients in the CDR group and one hundred and fifty-eight patients in Plate group were included in this study. The total incidences of dysphagia in the CDR and plate group were 36.58% and 60.43% at one week, 29.27% and 38.85% at one month, 21.95% and 31.65% at three months, 6.83% and 17.99% at six months, 5.85% and 14.39% at 12 months, and 4.39% and 10.07% at the final follow-up respectively (All P<0.05, Mann-Whitney U test). Ordinal Logistic regression analysis showed that female patients, two-level surgery, C4/5 surgery, and anterior cervical plating were significant risk factors for post-operative dysphagia (all P<0.05). ConclusionComparing ACDF with a plate, CDR with a Prestige LP can significantly reduce both transient and persistent post-operative dysphagia. Female patients, two-level surgery, C4/5 surgery and anterior cervical plating were associated with a higher incidence of dysphagia. Future prospective, randomized, controlled studies are needed to further validate these findings.

Clinical outcome of mid-term follow-up of anterior cervical non-fusion surgery versus anterior cervical discectomy and fusion for cervical spondylosis

To evaluate the clinical and radiological outcomes of artificial cervical disc replacement (Prodisc-C), dynamic cervical implant and anterior cervical discectomy and fusion (ACDF) in the treatment of cervical spondylosis. From May 2011 to May 2013, a total of 44 cervical spondylosis patients that received cervical disc arthroplasty (Prodisc-C), dynamic cervical implant (DCI) or ACDF were retrospectively reviewed in Orthopedics Department, Beijing Chaoyang Hospital, Capital Medical University.The patients were divided into three groups by surgical methods.Parameters as gender, age, the operation time, blood loss and average hospital stay of three groups were compared.The patients were followed 3 months, 6 months, 12 months and 24 months postoperatively.Neck disability index (NDI), Japanese Orthopaedic Association (JOA) Score and Visual Analogue Scale (VAS) were used to evaluate the clinical outcomes of the three groups.We also measured the cervical lordosis, range of motion of surgical segment and adjacent segment and height of disc at pre-op and post-op. All the patients were got at least 24 months follow-up.The differences between postoperative JOA, NDI and VAS scores and preoperative scores were of statistical significance (P<0.05). There was no statistical difference in average hospital stay, JOA, NDI and VAS recovery rate (P>0.05) among three groups.But the operative time and intraoperative blood loss were statistically different (P<0.05). Compared the pre-and postoperative ROM of C2-7, operative, upper and lower levels of each group respectively, the difference between pre-and postoperative ROM of ACDF group were of statistically significant [(16.6±3.6)°, (22.3±4.6)°, (18.1±3.1)°, P<0.05], while was no statistically significant of non-fusion group(P>0.05). There was no statistically significant difference between pre-and postoperative ROM of upper and lower levels among three groups (P>0.05), but had statistically difference in operative levels [(7.0±1.0) mm, (9.2±1.5) mm, (6.8±1.4) mm, P<0.05]. And there are no serious postoperative complications. Two cervical non-fusion surgery and ACDF have received good clinical effects in the treatment of spondylotic myelopathy or radicular spondylosis.The artificial cervical disc replacement and dynamic cervical implant can not only recover cervical lordosis and keep the range of motion and stability of the surgical segment, but also reduce the incidence of compensatory motion at adjacent segments and will prevent from adjacent segment degeneration.

Enhancing Clinical Study Retention Rates to Avoid Follow-up Bias: How Do We Keep Our Study Participants from "The Land of the Lost"?

In an earlier publication, we discussed the importance of loss to follow-up, how it should be calculated, and how many patients can be lost to follow-up without mistrusting the results.1 We argued that incomplete follow-up could bias the results when the dropout rates are different between study groups or when the patients who drop out are different from those who do not drop out. Simply put, the patients lost to follow-up often have a different prognosis than those who complete the study. We discussed that properly calculating the loss to follow-up can only be done by determining the right denominator. That includes all those randomly assigned in a randomized controlled trial and all who had the procedure during a prespecified time in a cohort study. A good rule of thumb is that 20% poses serious threats to validity. However, even less than 20% loss to follow-up can be a problem. Now that we understand the significant impact that loss to follow-up can have on our study results, we want to shift our focus to strategies to limit loss to follow-up. Unfortunately for retrospective studies where the data has already been collected, the toothpaste is out of the tube; nothing can be done to improve patient participation in the study. However, with this study design it is worth documenting the flow of the patients through each stage of the study: enrollment, assignment, follow-up, and analysis. A diagram is strongly recommended (Fig. 1). Fig. 1 Example of participant flow in hypothetical retrospective case series evaluating the incidence of adjacent segment degeneration in two-level cervical artificial disk replacement (ADR). Enrollment includes the number of participants who were screened ... However, if you are involved in prospective data collection for randomized trials, longitudinal prospective cohort studies, or prospective registries, there are several safeguards and strategies that you should consider implementing from the beginning of the project. These will be discussed in this edition of Science in Spine. It is tempting to get excited about enrollment and then let your guard down during the follow-up phase. The problem is that it does not matter how many participants are enrolled if you cannot get them to the finish line. So the planning starts up front and the process continues with a diligent effort to maintain very high retention throughout the course of the study until the very last enrolled subject has finished his or her final follow-up. This result is difficult to accomplish without personnel and a commitment of resources. Every prospective study requiring follow-up beyond the perioperative period necessitates a project coordinator with experience in following participants over time, which can rarely be done effectively by clinician investigators who are busy with the day-to-day clinical responsibilities. The number of sites involved (if it is a multisite study) and the number of participants anticipated for enrollment will dictate what level of commitment you need from this project coordinator. Sometimes 25% effort is enough but often it requires 50% or more, even up to 100%, in larger multisite trials. This person needs to have strong organizational and communication skills. Ideally, the coordinator will have spent time on the “front lines” recruiting and following participants so that he or she can speak and problem solve the challenges that the study coordinators face in retaining subjects. An alternative is a central methods center that employs more than one coordinator part-time who is versed in the retention strategies. Once this person(s) is identified, and a comprehensive follow-up strategy is established, then flexibility and ingenuity are paramount as the study progresses because no study is alike. There will always be obstacles and nuances that may impact retention. Good project coordinators can respond to these challenges and enlist their clinical investigators and study coordinators along the way to help problem solve. The following sections provide a fairly self-explanatory checklist of strategies that have been employed by many successful clinical trialists. These are divided into a prestudy planning phase and a study execution phase, although there is distinct overlap in many of these. All need to be planned for and considered for Institutional Review Board (IRB) approval.