Correction: Clinical improvement after surgery for degenerative cervical myelopathy; A comparison of Patient-Reported Outcome Measures during 12-month follow-up.

[This corrects the article DOI: 10.1371/journal.pone.0264954.].

The Norwegian registry for spine surgery (NORspine): cohort profile.

PURPOSE: To review and describe the development, methods and cohort of the lumbosacral part of the Norwegian registry for spine surgery (NORspine). METHODS: NORspine was established in 2007. It is government funded, covers all providers and captures consecutive cases undergoing operations for degenerative disorders. Patients' participation is voluntary and requires informed consent. A set of baseline-, process- and outcome-variables (3 and 12 months) recommended by the International Consortium for Health Outcome Measurement is reported by surgeons and patients. The main outcome is the Oswestry disability index (ODI) at 12 months. RESULTS: We show satisfactory data quality assessed by completeness, timeliness, accuracy, relevance and comparability. The coverage rate has been 100% since 2016 and the capture rate has increased to 74% in 2021. The cohort consists of 60,647 (47.6% women) cases with mean age 55.7 years, registered during the years 2007 through 2021. The proportions > 70 years and with an American Society of Anaesthesiologists' Physical Classification System (ASA) score > II has increased gradually to 26.1% and 19.3%, respectively. Mean ODI at baseline was 43.0 (standard deviation 17.3). Most cases were operated with decompression for disc herniation (n = 26,557, 43.8%) or spinal stenosis (n = 26,545, 43.8%), and 7417 (12.2%) with additional or primary fusion. The response rate at 12 months follow-up was 71.6%. CONCLUSION: NORspine is a well-designed population-based comprehensive national clinical quality registry. The register's methods ensure appropriate data for quality surveillance and improvement, and research.

Impact of the number of previous lumbar operations on patient-reported outcomes after surgery for lumbar spinal stenosis or lumbar disc herniation.

Repeated lumbar spine surgery has been associated with inferior clinical outcomes. This study aimed to examine and quantify the impact of this association in a national clinical register cohort. This is a population-based study from the Norwegian Registry for Spine surgery (NORspine). We included 26,723 consecutive cases operated for lumbar spinal stenosis or lumbar disc herniation from January 2007 to December 2018. The primary outcome was the Oswestry Disability Index (ODI), presented as the proportions reaching a patient-acceptable symptom state (PASS; defined as an ODI raw score ≤ 22) and ODI raw and change scores at 12-month follow-up. Secondary outcomes were the Global Perceived Effect scale, the numerical rating scale for pain, the EuroQoL five-dimensions health questionnaire, occurrence of perioperative complications and wound infections, and working capability. Binary logistic regression analysis was conducted to examine how the number of previous operations influenced the odds of not reaching a PASS. The proportion reaching a PASS decreased from 66.0% (95% confidence interval (CI) 65.4 to 66.7) in cases with no previous operation to 22.0% (95% CI 15.2 to 30.3) in cases with four or more previous operations (p < 0.001). The odds of not reaching a PASS were 2.1 (95% CI 1.9 to 2.2) in cases with one previous operation, 2.6 (95% CI 2.3 to 3.0) in cases with two, 4.4 (95% CI 3.4 to 5.5) in cases with three, and 6.9 (95% CI 4.5 to 10.5) in cases with four or more previous operations. The ODI raw and change scores and the secondary outcomes showed similar trends. We found a dose-response relationship between increasing number of previous operations and inferior outcomes among patients operated for degenerative conditions in the lumbar spine. This information should be considered in the shared decision-making process prior to elective spine surgery.

Non-respondents do not bias outcome assessment after cervical spine surgery: a multicenter observational study from the Norwegian registry for spine surgery (NORspine).

BACKGROUND: The Norwegian registry for spine surgery (NORspine) is a national clinical quality registry which has recorded more than 10,000 operations for degenerative conditions of the cervical spine since 2012. Registries are large observational cohorts, at risk for attrition bias. We therefore aimed to examine whether clinical outcomes differed between respondents and non-respondents to standardized questionnaire-based 12-month follow-up. METHODS: All eight public and private providers of cervical spine surgery in Norway report to NORspine. We included 334 consecutive patients who were registered with surgical treatment of degenerative conditions in the cervical spine in 2018 and did a retrospective analysis of prospectively collected register data and data on non-respondents' outcomes collected by telephone interviews. The primary outcome measure was patient-reported change in arm pain assessed with the numeric rating scale (NRS). Secondary outcome measures were change in neck pain assessed with the NRS, change in health-related quality of life assessed with EuroQol 5 Dimensions (EQ-5D), and patients' perceived benefit of the operation assessed by the Global Perceived Effect (GPE) scale. RESULTS: At baseline, there were few and small differences between the 238 (71.3%) respondents and the 96 (28.7%) non-respondents. We reached 76 (79.2%) non-respondents by telephone, and 63 (65.6%) consented to an interview. There was no statistically significant difference between groups in change in NRS score for arm pain (3.26 (95% CI 2.84 to 3.69) points for respondents and 2.77 (1.92 to 3.63) points for telephone interviewees) or any of the secondary outcome measures. CONCLUSIONS: The results indicate that patients lost to follow-up were missing at random. Analyses of outcomes based on data from respondents can be considered representative for the complete register cohort, if patient characteristics associated with attrition are controlled for.

Anterior surgical treatment for cervical degenerative radiculopathy: a prediction model for non-success.

PURPOSE: By using data from the Norwegian Registry for Spine Surgery, we wanted to develop and validate prediction models for non-success in patients operated with anterior surgical techniques for cervical degenerative radiculopathy (CDR). METHODS: This is a multicentre longitudinal study of 2022 patients undergoing CDR surgery and followed for 12 months to find prognostic models for non-success in neck disability and arm pain using multivariable logistic regression analysis. Model performance was evaluated by area under the receiver operating characteristic curve (AUC) and a calibration test. Internal validation by bootstrapping re-sampling with 1000 repetitions was applied to correct for over-optimism. The clinical usefulness of the neck disability model was explored by developing a risk matrix for individual case examples. RESULTS: Thirty-eight percent of patients experienced non-success in neck disability and 35% in arm pain. Loss to follow-up was 35% for both groups. Predictors for non-success in neck disability were high physical demands in work, low level of education, pending litigation, previous neck surgery, long duration of arm pain, medium-to-high baseline disability score and presence of anxiety/depression. AUC was 0.78 (95% CI, 0.75, 0.82). For the arm pain model, all predictors for non-success in neck disability, except for anxiety/depression, were found to be significant in addition to foreign mother tongue, smoking and medium-to-high baseline arm pain. AUC was 0.68 (95% CI, 0.64, 0.72). CONCLUSION: The neck disability model showed high discriminative performance, whereas the arm pain model was shown to be acceptable. Based upon the models, individualized risk estimates can be made and applied in shared decision-making with patients referred for surgical assessment.

What is success of treatment? Expected outcome scores in cervical radiculopathy patients were much higher than the previously reported cut-off values for success.

PURPOSE: Treatment success can be defined by asking a patient how they perceive their condition compared to prior to treatment, but it can also be defined by establishing success criteria in advance. We evaluated treatment outcome expectations in patients undergoing surgery or non-operative treatment for cervical radiculopathy. METHODS: The first 100 consecutive patients from an ongoing randomized controlled trial (NCT03674619) comparing the effectiveness of surgical and nonsurgical treatment for cervical radiculopathy were included. Patient-reported outcome measures and expected outcome and improvement were obtained before treatment. We compared these with previously published cut-off values for success. Arm pain, neck pain and headache were measured by a numeric rating scale. Neck disability index (NDI) was used to record pain-related disability. We applied Wilcoxon signed-rank test to compare the expected outcome scores for the two treatments. RESULTS: Patients reported mean NDI of 42.2 (95% CI 39.6-44.7) at baseline. The expected mean NDI one year after the treatment was 4 (95% CI 3.0-5.1). The expected mean reduction in NDI was 38.3 (95% CI 35.8-40.8). Calculated as a percentage change score, the patients expected a mean reduction of 91.2% (95% CI 89.2-93.2). Patient expectations were higher regarding surgical treatment for arm pain, neck pain and working ability, P < 0.001, but not for headache. CONCLUSIONS: The expected improvement after treatment of cervical radiculopathy was much higher than the previously reported cut-off values for success. Patients with cervical radiculopathy had higher expectations to surgical treatment.

Clinical improvement after surgery for degenerative cervical myelopathy; A comparison of Patient-Reported Outcome Measures during 12-month follow-up.

OBJECT: Although many patients report clinical improvement after surgery due to degenerative cervical myelopathy, the aim of intervention is to stop progression of spinal cord dysfunction. We wanted to provide estimates and assess achievement rates of Minimal Clinically Important Difference (MCID) at 3- and 12-month follow-up for Neck Disability Index (NDI), Numeric Rating Scale for arm pain (NRS-AP) and neck pain (NRS-NP), Euro-Qol (EQ-5D-3L), and European Myelopathy Score (EMS). METHODS: 614 degenerative cervical myelopathy patients undergoing surgery responded to Patient-Reported Outcome Measures (PROMs) prior to, 3 and 12 months after surgery. External criterion was the Global Perceived Effect Scale (1-7), defining MCID as "slightly better", "much better" and "completely recovered". MCID estimates with highest sensitivity and specificity were calculated by Receiver Operating Curves for change and percentage change scores in the whole sample and in anterior and posterior procedural groups. RESULTS: The NDI and NRS-NP percentage change scores were the most accurate PROMs with a MCID of 16%. The change score for NDI and percentage change scores for NDI, NRS-AP and NRS-NP were slightly higher in the anterior procedure group compared to the posterior procedure group, while remaining PROM estimates were similar across procedure type. The MCID achievement rates at 12-month follow-up ranged from 51% in EMS to 62% in NRS-NP. CONCLUSION: The NDI and NRS-NP percentage change scores were the most accurate PROMs to measure clinical improvement after surgery for degenerative cervical myelopathy. We recommend using different cut-off estimates for anterior and posterior approach procedures. A MCID achievement rate of 60% or less must be interpreted in the perspective that the main goal of surgery for degenerative cervical myelopathy is to prevent worsening of the condition.

Effect of Arthroplasty vs Fusion for Patients With Cervical Radiculopathy: A Randomized Clinical Trial.

Importance: Surgical treatment for cervical radiculopathy is increasing. Treatment with motion preserving anterior cervical disc arthroplasty was introduced to prevent symptomatic adjacent segment disease, and there is need to evaluate results of this treatment compared with standard anterior cervical discectomy and fusion. Objective: To investigate clinical outcomes at 5 years for arthroplasty vs fusion in patients who underwent surgical treatment for cervical radiculopathy. Design, Setting, and Participants: This multicenter, single-blinded, randomized clinical trial included patients aged 25 to 60 years with C6 or C7 radiculopathy referred to study sites' outpatient clinics from 2008 to 2013. Data were analyzed from December 2019 to December 2020. Interventions: Patients were randomly assigned to arthroplasty or fusion. Patients were blinded to which treatment they received. The surgical team was blinded until nerve root decompression was completed. Main Outcomes and Measures: The primary end point was change in Neck Disability Index (NDI) score. Secondary outcomes were arm and neck pain, measured with numeric rating scales (NRS); quality of life, measured with the EuroQol-5D (EQ-5D); reoperation rates; and adjacent segment disease. Results: Among 147 eligible patients, 4 (2.7%) declined to participate and 7 (4.8%) were excluded. A total of 136 patients were randomized (mean [SD] age, 44.1 [7.0] years; 73 (53.7%) women), with 68 patients randomized to arthroplasty and 68 patients randomized to fusion. A total of 114 patients (83.8%) completed the 5-year follow-up. In the arthroplasty group, the mean NDI score was 45.9 (95% CI, 43.3 to 48.4) points at baseline and 22.2 (95% CI, 18.0 to 26.3) points at 5 years follow-up, and in the fusion group, mean NDI score was 51.3 (95% CI, 48.1 to 54.4) points at baseline, and 21.3 (95% CI, 17.0 to 25.6) points at 5 years follow-up. The changes in mean NDI scores between baseline and 5 years were statistically significant for arthroplasty (mean change, 24.8 [95% CI, 19.8 to 29.9] points; P < .001) and fusion (mean change, 29.9 [95% CI, 24.0 to 35.9] points; P < .001), but the change in mean NDI scores was not significantly different between groups (difference, 5.1 [95% CI, -2.6 to 12.7] points; P = .19). There were no significant differences in changes in arm pain (mean [SE] change, 3.5 [0.5] vs 3.1 [0.4]; P = .47), neck pain (mean [SE] change, 3.0 [0.5] vs 3.4 [0.5]; P = .50), EQ-5D (mean [SE] change, 0.39 [0.4] vs 0.45 [0.6]; P = .46), patients requiring reoperation (10 patients [14.7%] vs 8 patients [11.8%]; P = .61), and adjacent segment disease (0 patients vs 1 patient [1.5%]; P = .32) between the arthroplasty and fusion groups. Conclusions and Relevance: In this randomized clinical trial, patients treated with arthroplasty and fusion reported similar and substantial clinical improvement at 5 years. Trial Registration: ClinicalTrials.gov Identifier: NCT00735176.

A randomised controlled trial comparing the effectiveness of surgical and nonsurgical treatment for cervical radiculopathy.

BACKGROUND: Cervical radiculopathy is usually caused by disc herniation or spondylosis. The prognosis is expected to be good in most patients, but there is limited scientific evidence on the indications for nonsurgical and surgical treatments. The aim of the present study is to evaluate and compare the effectiveness of surgical and nonsurgical treatment in two trials - including disc herniation and spondylosis, respectively, and to evaluate factors that contribute to better decision making. METHODS/DESIGN: Patients with disabling radicular arm pain and MRI-proven cervical disc herniation or spondylosis will be randomised to receive nonsurgical or surgical treatment. The follow-up period is one year and the sample size is estimated to be 50 for each arm in the two trials, giving a total of 200 patients. The primary outcomes are the Neck Disability Index and arm pain. Secondary outcomes include neck pain; EQ-5D and costs to evaluate cost-effectiveness; prognostic factors; CT and MRI scans, to estimate intervertebral foraminal area and nerve root compression; and the expected minimal improvement for willingness to undergo treatment. DISCUSSION: The outcomes of this study will contribute to better decision making in the treatment of cervical radiculopathy. TRIAL REGISTRATION: This study has been registered at ClinicalTrials.gov as NCT03674619, on September 17, 2018.

A man in his fifties with variable weakness and difficulty in walking. / En mann i 50-årene med varierende kraftsvikt og gangvansker.

BACKGROUND: An active man in his fifties was treated for atrial fibrillation with ablation. One week later he noticed variable weakness in his lower extremities. In the days that followed, his symptoms improved but could vary from day to day. CASE PRESENTATION: On admission 3 months after the initial symptoms, he had spasticity and weakness in both lower extremities, with hyperreflexia and positive Babinski. Spinal fluid contained slightly elevated protein levels. Spinal MRI showed cord oedema and gadolinium enhancement over multiple spinal levels. Autoimmune myelitis was suspected, and he was treated with high dose steroids and rituximab. Due to lack of effect, repeated examinations were initiated. Information from his patient history regarding symptom exacerbation by walking or bending forward was emphasised. Repeated MRI showed unchanged spinal oedema and dilated peri- and intramedullary vessels. MRA and spinal digital DSA revealed a dural fistula at third lumbar level, with the left L3 radiculomedullary artery as the feed artery. The fistula was successfully ligated by the neurosurgeon. INTERPRETATION: Spinal vascular lesions are rare and the diagnosis may be challenging due to atypical presentation. The case shows that detailed information from the patient history and thorough clinical investigation is of paramount importance to disclose this probably underreported condition.

Distinguishing Anesthetized from Awake State in Patients: A New Approach Using One Second Segments of Raw EEG.

Objective: The objective of this study was to test whether properties of 1-s segments of spontaneous scalp EEG activity can be used to automatically distinguish the awake state from the anesthetized state in patients undergoing general propofol anesthesia. Methods: Twenty five channel EEG was recorded from 10 patients undergoing general intravenous propofol anesthesia with remifentanil during anterior cervical discectomy and fusion. From this, we extracted properties of the EEG by applying the Directed Transfer Function (DTF) directly to every 1-s segment of the raw EEG signal. The extracted properties were used to develop a data-driven classification algorithm to categorize patients as "anesthetized" or "awake" for every 1-s segment of raw EEG. Results: The properties of the EEG signal were significantly different in the awake and anesthetized states for at least 8 of the 25 channels (p < 0.05, Bonferroni corrected Wilcoxon rank-sum tests). Using these differences, our algorithms achieved classification accuracies of 95.9%. Conclusion: Properties of the DTF calculated from 1-s segments of raw EEG can be used to reliably classify whether the patients undergoing general anesthesia with propofol and remifentanil were awake or anesthetized. Significance: This method may be useful for developing automatic real-time monitors of anesthesia.

The Norwegian Cervical Arthroplasty Trial (NORCAT): 2-year clinical outcome after single-level cervical arthroplasty versus fusion-a prospective, single-blinded, randomized, controlled multicenter study.

PURPOSE: Standard surgical treatment for symptomatic cervical disc disease has been discectomy and fusion, but the use of arthroplasty, designed to preserve motion, has increased, and most studies report clinical outcome in its favor. Few of these trials, however, blinded the patients. We, therefore, conducted the Norwegian Cervical Arthroplasty Trial, and present 2-year clinical outcome after arthroplasty or fusion. METHODS: This multicenter trial included 136 patients with single-level cervical disc disease. The patients were randomized to arthroplasty or fusion, and blinded to the treatment modality. The surgical team was blinded to randomization until nerve root decompression was completed. Primary outcome was the self-rated Neck Disability Index. Secondary outcomes were the numeric rating scale for pain and quality of life questionnaires Short Form-36 and EuroQol-5Dimension-3 Level. RESULTS: There was a significant improvement in the primary and all secondary outcomes from baseline to 2-year follow-up for both arthroplasty and fusion (P < 0.001), and no observed significant between-group differences at any follow-up times. However, linear mixed model analyses, correcting for baseline values, dropouts and missing data, revealed a difference in Neck Disability Index (P = 0.049), and arm pain (P = 0.027) in favor of fusion at 2 years. The duration of surgery was longer (P < 0.001), and the frequency of reoperations higher (P = 0.029) with arthroplasty. CONCLUSION: The present study showed excellent clinical results and no significant difference between treatments at any scheduled follow-up. However, the rate of index level reoperations was higher and the duration of surgery longer with arthroplasty. TRIAL REGISTRATION: http://www.clinicaltrials.gov NCT 00735176.19.

Heterotopic ossification and clinical outcome in nonconstrained cervical arthroplasty 2 years after surgery: the Norwegian Cervical Arthroplasty Trial (NORCAT).

PURPOSE: Heterotopic ossification is a phenomenon in cervical arthroplasty. Previous reports have mainly focused on various semiconstrained devices and only a few publications have focused on ossification around devices that are nonconstrained. The purpose of this study was to assess the occurrence of heterotopic ossification around a nonconstrained cervical device and how it affects clinical outcome 2 years after surgery. METHODS: Thirty-seven patients were included from a larger cohort of a randomized controlled trial (NORCAT) which compared single-level cervical arthroplasty with fusion. The occurrence of heterotopic ossification was assessed with a CT scan and two neuroradiologists determined its degree. For grading, we used the Mehren/Suchomel classification system (grade 0-4). The patients were divided by level of ossification, low grade (0-2) or high grade (3-4), and clinical outcomes were compared. Self-rated disability for neck and arm pain (Neck Disability Index), health-related quality of life (the Short Form-36 and EuroQol-5D), and pain (the Numeric Rating Scale 11) were used as clinical outcome measures. RESULTS: Heterotopic ossification was encountered in all patients 2 years after surgery. Complete fusion (grade 4) was found in 16 % of participants, and high-grade ossification (grade 3-4) occurred in 62 %. The remaining patients were classified as having low-grade ossification (grade 2). There were no differences in the clinical outcomes of patients with low- and high-grade ossification. CONCLUSION: High-grade heterotopic ossification and spontaneous fusion 2 years after surgery were seen in a significant number of patients. However, the degree of ossification did not influence the clinical outcome.

The use of surgery for cervical degenerative disease in Norway in the period 2008-2014 : A population-based study of 6511 procedures.

BACKGROUND: The incidence rate of surgical treatment of cervical degenerative diseases (CDD) has increased in the USA and a large geographic variation has been shown. Little is known about such rates in Scandinavia and Europe. The aim of this population-based study was to (1) investigate annual incidence rates of operations performed in Norway, (2) to compare trends and variations in rates for surgical indications with and without myelopathy, and (3) to compare variations in the use of surgery between residential areas. METHODS: Patients operated for CDD and recorded in the Norwegian Patient Registry from 2008 to 2014 were evaluated according to residential areas (resident county and Regional Health Authority (RHA) area), age, gender, treating hospital, and whether myelopathy was present or not. Surgical rates were adjusted for age and gender. Data from private health care were also included. RESULTS: The annual surgical rates increased by 74.1 % from 2008 to 2014 (12.5/100,000 inhabitants). The largest increase was for surgical treatment of radiculopathy, 86.5 %. Surgical rates for CDD varied in 2014 with a ratio of 1.5 between the highest and lowest RHA and with a ratio of 2.5 between the different residential counties within one RHA. The treatment rates for myelopathy were relatively stable over time, but showed an increase of 2.1/100,000 (44.6 %) from 2013 to 2014. CONCLUSIONS: Our study shows that the rate of surgical treatment for radiculopathy due to CDD has increased substantially from 2008 to 2014 for all RHAs in Norway. The incidence rate for surgical treatment of myelopathy was more stable. An unexplained and moderate geographic variation was found.

The Long-term Outcome After Resection of Intraspinal Nerve Sheath Tumors: Report of 131 Consecutive Cases.

BACKGROUND: The existing literature on recurrence rates and long-term clinical outcome after resection of intraspinal nerve sheath tumors is limited. OBJECTIVE: To evaluate progression-free survival, overall survival, and long-term clinical outcome in a consecutive series of 131 patients with symptomatic intraspinal nerve sheath tumors. METHODS: Medical charts were retrospectively reviewed. Surviving patients voluntarily participated in a clinical history and physical examination that focused on neurological function and current tumor status. RESULTS: Follow-up data are 100% complete; median follow-up time was 6.1 years. All patients (100%) had surgery as the first line of treatment; gross total resection was performed in 112 patients (85.5%) and subtotal resection in 19 patients (14.5%). Five-year progression-free survival was 89%. The following risk factors for recurrence were identified: neurofibroma, malignant peripheral nerve sheath tumor, subtotal resection, neurofibromatoses/schwannomatosis, and advancing age at diagnosis. More than 95% of patients had neurological function compatible with an independent life at follow-up. The rate of tumor recurrence in nonneurofibromatosis patients undergoing total resection of a single schwannoma was 3% (3/93), in comparison with a recurrence rate of 32% (12/38) in the remaining patients. CONCLUSION: Gross total resection is the gold standard treatment for patients with intraspinal nerve sheath tumors. In a time of limited health care resources, we recommend that follow-up be focused on the subgroup of patients with a high risk of recurrence. The benefit of long-term, yearly magnetic resonance imaging follow-up with respect to recurrence in nonneurofibromatosis patients undergoing gross total resection of a single schwannoma is, in our opinion, questionable. 1NF2, neurofibromatosis 2NST, nerve sheath tumorOS, overall survivalPFS, progression-free survivalSTR, subtotal resectionWHO, World Health Organization.

Idiopathic ventral spinal cord herniation: an increasingly recognized cause of thoracic myelopathy.

Idiopathic spinal cord herniation (ISCH), where a segment of the spinal cord has herniated through a ventral defect in the dura, is a rarely encountered cause of thoracic myelopathy. The purpose of our study was to increase the clinical awareness of this condition by presenting our experience with seven consecutive cases treated in our department since 2005. All the patients developed pronounced spastic paraparesis or Brown-Séquard syndrome for several years (mean, 4.7 years) prior to diagnosis. MRI was consistent with a transdural spinal cord herniation in the mid-thoracic region in all the cases. The patients underwent surgical reduction of the herniated spinal cord and closure of the dural defect using an artificial dural patch. At follow-up, three patients experienced considerable clinical improvement, one had slight improvement, one had transient improvement, and two were unchanged. Two of the four patients with sphincter dysfunction regained sphincter control. MRI showed realignment of the spinal cord in all the patients. ISCH is probably a more common cause of thoracic myelopathy than previously recognized. The patients usually develop progressive myelopathy for several years before the correct diagnosis is made. Early diagnosis is important in order to treat the patients before the myelopathy has become advanced.

Magnetic resonance imaging evaluation after implantation of a titanium cervical disc prosthesis: a comparison of 1.5 and 3 Tesla magnet strength.

PURPOSE: Cervical disc prostheses induce significant amount of artifact in magnetic resonance imaging which may complicate radiologic follow-up after surgery. The purpose of this study was to investigate as to what extent the artifact, induced by the frequently used Discover(®) cervical disc prosthesis, impedes interpretation of the MR images at operated and adjacent levels in 1.5 and 3 Tesla MR. METHODS: Ten subsequent patients were investigated in both 1.5 and 3 Tesla MR with standard image sequences one year following anterior cervical discectomy with arthroplasty. OUTCOME MEASURES: Two neuroradiologists evaluated the images by consensus. Emphasis was made on signal changes in medulla at all levels and visualization of root canals at operated and adjacent levels. A "blur artifact ratio" was calculated and defined as the height of the artifact on T1 sagittal images related to the operated level. RESULTS: The artifacts induced in 1.5 and 3 Tesla MR were of entirely different character and evaluation of the spinal cord at operated level was impossible in both magnets. Artifacts also made the root canals difficult to assess at operated level and more pronounced in the 3 Tesla MR. At the adjacent levels however, the spinal cord and root canals were completely visualized in all patients. The "blur artifact" induced at operated level was also more pronounced in the 3 Tesla MR. CONCLUSIONS: The artifact induced by the Discover(®) titanium disc prosthesis in both 1.5 and 3 Tesla MR, makes interpretation of the spinal cord impossible and visualization of the root canals difficult at operated level. Adjusting the MR sequences to produce the least amount of artifact is important.