Lumbar spine: reliability of MR imaging findings.

PURPOSE: To characterize the inter- and intraobserver variability of qualitative, non-disk contour degenerative findings of the lumbar spine at magnetic resonance (MR) imaging. MATERIALS AND METHODS: The case accrual method used to perform this institutional review board-approved, HIPAA-compliant retrospective study was the random selection of 111 interpretable MR examination cases of subjects from the Spine Patient Outcomes Research Trial. The subjects were aged 18-87 years (mean, 53 years +/- 16 [standard deviation]). Four independent readers rated the cases according to defined criteria. A subsample of 40 MR examination cases was selected for reevaluation at least 1 month later. The following findings were assessed: spondylolisthesis, disk degeneration, marrow endplate abnormality (Modic changes), posterior anular hyperintense zone (HIZ), and facet arthropathy. Inter- and intraobserver agreement in rating the data was summarized by using weighted kappa statistics. RESULTS: Interobserver agreement was good (kappa = 0.66) in rating disk degeneration and moderate in rating spondylolisthesis (kappa = 0.55), Modic changes (kappa = 0.59), facet arthropathy (kappa = 0.54), and posterior HIZ (kappa = 0.44). Interobserver agreement in rating the extent of Modic changes was moderate: kappa Values were 0.43 for determining superior anteroposterior extent, 0.47 for determining superior craniocaudal extent, 0.57 for determining inferior anteroposterior extent, and 0.48 for determining inferior craniocaudal extent. Intraobserver agreement was good in rating spondylolisthesis (kappa = 0.66), disk degeneration (kappa = 0.74), Modic changes (kappa = 0.64), facet arthropathy (kappa = 0.69), and posterior HIZ (kappa = 0.67). Intraobserver agreement in rating the extent of Modic changes was moderate, with kappa values of 0.54 for superior anteroposterior, 0.60 for inferior anteroposterior, 0.50 for superior craniocaudal, and 0.60 for inferior craniocaudal extent determinations. CONCLUSION: The interpretation of general lumbar spine MR characteristics has sufficient reliability to warrant the further evaluation of these features as potential prognostic indicators.

Accuracy of MRI for diagnosis of discogenic pain.

BACKGROUND: Previous studies have compared MRI parameters to the results from discography. However, none have evaluated the overall diagnostic performance of MRI, taking into account that many MRI characteristics may be correlated. OBJECTIVE: Determine the accuracy of MRI for diagnosis of discogenic pain, taking into consideration the interdependence of MRI parameters. STUDY DESIGN: An observational report. SETTING: Sample of 143 patients, 92 male and 51 female in a spinal pain speciality center. Discography classification and scorings for MRI parameters were collected as outcome measures. METHODS: MRI and discography data were collected from patients with chronic low back pain. Five MRI characteristics were defined: high intensity zone, nuclear signal, disc height, disc contour, and bone marrow intensity change. On discography, each disc was classified as either positive or negative. The accuracy of MRI was evaluated using receiver operating characteristic curves. RESULTS: MRI parameters are correlated with each other and with discography findings, and these correlations affect the accuracy of MRI. Overall, nuclear signal alone is as accurate as any of the other MRI parameters, or combination of parameters, in the diagnosis of discogenic pain. While there is no difference in overall accuracy between nuclear signal and the other MRI parameters, these parameters do influence test performance when there is a moderate loss of nuclear signal. Moderate loss of nuclear signal and disc bulge has the best combination of sensitivity (79.8%) and specificity (79.3%). Adding moderate loss of disc height improves specificity (82.0%) slightly, and decreases sensitivity (73.6%) slightly, while incorporating high intensity zone grade II further improves specificity (92.6%) and decreases sensitivity (54.7%). High intensity zone grade I and bone marrow intensity change have minimal influence, even when there is moderate loss of nuclear signal. CONCLUSIONS: MRI parameters are correlated with each other and with discography findings, influencing the diagnostic performance of MRI. Combining MRI parameters improves the diagnostic performance of MRI, but only in the presence of moderate loss of nuclear signal. When there is either normal nuclear signal or severe loss of nuclear signal the other MRI parameters have no influence on test performance. The practical implication for physicians that use discography is that the most important single MRI parameter to consider is nuclear signal. If nuclear signal is normal the disc is very likely to be negative on discography, while if there is severe loss of nuclear signal it is very likely to be positive. Discography will be most useful in discs with moderate loss of nuclear signal, particularly if there are no other MRI abnormalities present.

Interobserver agreement using computed tomography to assess radiographic fusion criteria with a unique titanium interbody device.

The accuracy of using computed tomography (CT) to assess interbody fusion in patients with titanium implants has been questioned in the past. Radiologists have reported difficulty assessing fusion bone quality because of metal artifact and small graft windows. A new titanium interbody implant with a large footprint and a wide graft aperture has been developed. We conducted a study to determine the interobserver reliability of using CT to assess radiographic fusion variables with the new titanium interbody device. Patients underwent anterior lumbar interbody fusion with the same titanium interbody implant. Reconstructed CT images were obtained randomly at 6, 9, or 12 months. Two independent radiologists reviewed the scans. Interobserver reliability was calculated using the κ statistic. Fifty-six spinal fusion levels (33 patients) were analyzed. The radiologists agreed on 345 of the 392 fusion data points reviewed (κ = .88). Agreement for solid fusion formation was 0.77. This interbody device demonstrated minimal artifact and minimal subsidence, and trabecular bone was easily identified throughout the implant in the vast majority of cases reviewed. High interobserver agreement was noted across all radiographic variables assessed.

Magnetic resonance imaging predictors of surgical outcome in patients with lumbar intervertebral disc herniation.

STUDY DESIGN: A retrospective cohort design. OBJECTIVE: To determine whether baseline magnetic resonance imaging findings, including central/foraminal stenosis, Modic change, disc morphology, facet arthropathy, disc degeneration, nerve root impingement, and thecal sac compression, are associated with differential surgical treatment effect. SUMMARY OF BACKGROUND DATA: Intervertebral disc herniation remains the most common source of lumbar radiculopathy treated either with discectomy or nonoperative intervention. Although magnetic resonance imaging remains the reliable "gold standard" for diagnosis, uncertainty surrounds the relationship between magnetic resonance imaging findings and treatment outcomes. METHODS: Three hundred seven "complete" images from patients enrolled in a previous trial were de-identified and evaluated by 1 of 4 independent readers. Findings were compared with outcome measures including the Oswestry Disability Index. Differences in surgery and nonoperative treatment outcomes were evaluated between image characteristic subgroups and TE determined by the difference in Oswestry Disability Index scores. RESULTS: The cohort comprised 40% females with an average age of 41.5 (±11.6) years, 61% of whom underwent discectomy for intervertebral disc herniation. Patients undergoing surgery with Modic type I endplate changes had worse outcomes (-26.4 vs. -39.7 for none and -39.2 for type 2, P = 0.002) and smaller treatment effect (-3.5 vs. -19.3 for none and -15.7 for type 2, P = 0.003). Those with compression of ≥1/3 showed the greatest improvement within the surgical group (-41.9 for ≥1/3 vs. -31.6 for none and -38.1 for <1/3, P = 0.007) and the highest TE (-23 compared with -11.7 for none and -15.2 for <1/3, P = 0.015). Furthermore, patients with minimal nerve root impingement demonstrated worse surgical outcomes (-26.5 vs. -41.1 for "displaced" and -38.9 for "compressed," P = 0.016). CONCLUSION: Among patients with intervertebral disc herniation, those with thecal sac compression of 1/3 or more had greater surgical treatment effect than those with small disc herniations and Modic type I changes. In addition, patients with nerve root "compression" and "displacement" benefit more from surgery than those with minimal nerve root impingement. LEVEL OF EVIDENCE: 2.

Reliability of readings of magnetic resonance imaging features of lumbar spinal stenosis.

STUDY DESIGN: A reliability assessment of standardized magnetic resonance imaging (MRI) interpretations and measurements. OBJECTIVE: To determine the intra- and inter-reader reliability of MRI features of lumbar spinal stenosis (SPS), including severity of central, subarticular, and foraminal stenoses, grading of nerve root impingement, and measurements of cross-sectional area of the spinal canal and thecal sac. SUMMARY OF BACKGROUND DATA: MRI is commonly used to assess patients with spinal stenosis. Although a number of studies have evaluated the reliability of certain MRI characteristics, comprehensive evaluation of the reliability of MRI readings in spinal stenosis is lacking. METHODS: Fifty-eight randomly selected MR images from patients with SPS enrolled in the Spine Patient Outcomes Research Trial were evaluated. Qualitative ratings of imaging features were performed according to defined criteria by 4 independent readers (3 radiologists and 1 orthopedic surgeon). A sample of 20 MRIs was reevaluated by each reader at least 1 month later. Weighted kappa statistics were used to characterize intra- and inter-reader reliability for qualitative rating data. Separate quantitative measurements were performed by 2 other radiologists. Intraclass correlation coefficients and summaries of measurement error were used to characterize reliability for quantitative measurements. RESULTS: Intra-reader reliability was higher than inter-reader reliability for all features. Inter-reader reliability in assessing central stenosis was substantial, with an overall kappa of 0.73 (95% CI 0.69-0.77). Foraminal stenosis and nerve root impingement showed moderate to substantial agreement with overall kappa of 0.58 (95% CI 0.53-0.63) and 0.51 (95% CI 0.42-0.59), respectively. Subarticular zone stenosis yielded the poorest agreement (overall kappa 0.49; 95% CI 0.42-0.55) and showed marked variability in agreement between reader pairs. Quantitative measures showed inter-reader intraclass correlation coefficients ranging from 0.58 to 0.90. The mean absolute difference between readers in measured thecal sac area was 128 mm (13%). CONCLUSION: The imaging characteristics of spinal stenosis assessed in this study showed moderate to substantial reliability; future studies should assess whether these findings have prognostic significance in SPS patients.

Reliability of magnetic resonance imaging readings for lumbar disc herniation in the Spine Patient Outcomes Research Trial (SPORT).

STUDY DESIGN: Assessment of the reliability of standardized magnetic resonance imaging (MRI) interpretations and measurements. OBJECTIVE: To determine the intra- and inter-reader reliability of MRI parameters relevant to patients with intervertebral disc herniation (IDH), including disc morphology classification, degree of thecal sac compromise, grading of nerve root impingement, and measurements of cross-sectional area of the spinal canal, thecal sac, and disc fragment. SUMMARY OF BACKGROUND DATA: MRI is increasingly used to assess patients with sciatica and IDH, but the relationship between specific imaging characteristics and patient outcomes remains uncertain. Although other studies have evaluated the reliability of certain MRI characteristics, comprehensive evaluation of the reliability of readings of herniated disc features on MRI is lacking. METHODS: Sixty randomly selected MR images from patients with IDH enrolled in the Spine Patient Outcomes Research Trial were each rated according to defined criteria by 4 independent readers (3 radiologists and 1 orthopedic surgeon). Quantitative measurements were performed separately by 2 other radiologists. A sample of 20 MRIs was re-evaluated by each reader at least 1 month later. Agreement for rating data were assessed with kappa statistics using linear weights. Reliability of the quantitative measurements was assessed using intraclass correlation coefficients (ICCs) and summaries of measurement error. RESULTS: Inter-reader reliability was substantial for disc morphology [overall kappa 0.81 (95% confidence interval (CI): 0.78, 0.85)], moderate for thecal sac compression [overall kappa 0.54 (95% CI: 0.37, 0.68)], and moderate for grading nerve root impingement [overall kappa 0.47 (95% CI: 0.36, 0.56)]. Quantitative measures showed high ICCs of 0.87 to 0.96 for spinal canal and thecal sac cross-sectional areas. Measures of disc fragment area had moderate ICCs of 0.65 to 0.83. Mean absolute differences between measurements ranged from approximately 15% to 20%. CONCLUSION: Classification of disc morphology showed substantial intra- and inter-reader agreement, whereas thecal sac and nerve root compression showed more moderate reader reliability. Quantitative measures of canal and thecal sac area showed good reliability, whereas measurement of disc fragment area showed more modest reliability.