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Currently, there is no way to signify with coding that a magnetic resonance imaging (MRI) is open or positional. The service would be coded using the CPT code for the MRI scan.
In evaluating this approach to imaging, it is important to determine if positional magnetic resonance imaging (MRI) results in additional findings. However, it is also important to determine if treatment of these additional findings results in improved outcomes. This additional step is important given the previously described false-positive findings with MRI of the spine. For example, Jarvik and colleagues reported that many MRI findings have a high prevalence in subjects without low back pain and that findings such as bulging discs and disc protrusion are of limited diagnostic use. They also reported that the less common findings of moderate or severe central stenosis, root compression, and disc extrusion were more likely to be clinically relevant. (1)
A systematic review of emerging MRI technologies for musculoskeletal imaging under loading stress was prepared by the Tufts Medical Center Evidence-based Practice Center for the Agency for Healthcare Research and Quality (AHRQ) in 2011. (2) Included were 36 studies that used positional weight-bearing MRI in patients with musculoskeletal conditions. Also included were studies evaluating axial compression devices. Most studies were cross-sectional or had case-control designs. The most commonly imaged body region was the lumbar spine. Four studies of lumbar spine were identified that compared positional weight-bearing MRI with conventional MRI, myelography, or non-weight-bearing imaging in the same MRI device, however, these studies did not report the effect of the technology on patient outcomes. Two studies of foot imaging that compared weight-bearing MRI with MRI in the supine position with the same MRI device found that the two techniques provided similar information. Two studies of imaging the knee joint found differences between weight-bearing MRI and non-weight-bearing MRI using the same device; no functional outcomes were reported. The potential effect on image quality of low magnetic field strengths (< 0.6 Tesla) in weight-bearing MRI scanners was not assessed. The systematic review concluded that despite the large number of available studies, considerable uncertainty remains about the utility of this technique for the clinical management of musculoskeletal conditions.
One of the studies included in the systematic review was a quantitative comparison of positional MRI in neutral, flexion, and extension positions by Zou et al. in 2008. (3) The study included 553 patients (mean age, 46 years; range: 18–76 years) with symptomatic back pain with/without radiculopathy who were referred for kinetic/positional MRI (0.6 Tesla). The disc bulge on MRI in the three positions (neutral, flexion, and extension) was quantified by MRI analysis software, and the bulge size was compared independently by two spine surgeons who were unaware of the patient’s history and clinical findings. Increased disc bulge at extension and flexion, in comparison with neutral, was seen in 16% and 12% of discs, respectively. Diagnosis of grade 2 disc bulge that had been categorized as grade 1 in neutral position (i.e., missed diagnosis) was 19.5% for extension and 15.3% for flexion MRI.
Another study included in the systematic review was by Weishaupt and colleagues, who reported finding thirteen instances of nerve root deviation in the seated extension position in a 0.5 Tesla positional MRI compared with ten instances in the supine position in a 1.0 Tesla conventional MRI, in a group of 30 patients with chronic low back pain. (4) Diagnoses in the supine position changed in four disks (5%) in seated flexion and in seven disks (9%) in seated extension. They also reported that positional pain score differences were related to foraminal size. Vitaz et al. reported changes in spinal cord compression, angulation, and alignment that occurred during physiologic movement in 20 patients with cervical spine disorders. (5) They reported excellent or good image quality in 90% of cases.
Ferreiro Perez et al. compared recumbent and upright-sitting positions in 89 patients with disc herniation or spondylolisthesis (cervical or lumbar spine) in 2007. (6) Using a 0.6 Tesla Upright MRI system for both positions, pathology (disc herniation or spondylolisthesis) was identified in 68 patients (76%). Images from 18 patients (20%) were not interpretable due to motion artifact. Pathologic features were better identified (i.e., either only evident or seen to be enlarged) in 52 of the 68 patients (76%) when in the sitting position; 10 of these were only observed in the sitting position. Pathologic features were better identified in the recumbent position in 11 of the 68 patients (16%). The overall underestimation rate was calculated to be 62% for patients in the recumbent position and 16% for those in the upright-seated position. This research suggests that there may be advantages when the position during imaging is matched with the positional symptoms of the patient. However, a more appropriate comparison group would be a standard recumbent clinical MRI system (e.g., field strength >0.6 T). In addition, technical problems with motion artifact were due to poor stabilization in an upright-sitting position.
A 2008 study compared vertical (standing) MRI and recumbent MRI with axial loading in patients with lumbar spinal stenosis. (7) Sixteen patients with neurogenic claudication experienced mainly during walking or in an erect position, were recruited for this phase of the study. Each patient underwent four scans with a 0.6 Tesla Upright MRI system, consisting of vertical, horizontal with compression at a load of 40% of body weight, horizontal with no load, and finally horizontal with a 50% axial load. All horizontal scans were conducted with a cushion placed below the lower back to induce extension of the lumbar spine. Results showed similar dural sac cross-sectional area (DCSA) between the two positions, suggesting that the standing position may be adequately simulated while recumbent by axial loading and lordosis. Results were not correlated with patient symptoms in this study.
Conclusions: The literature shows a number of studies reporting that positional MRI can identify abnormalities in patients in whom conventional (supine) MRI did not identify significant abnormal findings. However, the clinical significance of these findings and the effect on patient outcomes is uncertain.
No studies were found that described clinical outcomes of patients whose treatments were selected on the new findings of positional MRI, and the incremental benefit of this imaging in clinical practice is not yet known. The clinical benefit of basing treatment decisions, including surgery, on these additional findings needs to be established. Studies that correlate the positional MRI findings with patient symptoms and outcomes of treatment are also needed. Another concern that needs further study is that positional scans, which use lower strength magnets, may be of lesser quality than those from traditional supine MRI. The scientific evidence at this time does not permit conclusions concerning the effect of this technology on health outcomes. Therefore, the use of positional MRI is considered experimental, investigational and unproven.
Practice Guidelines and Position Statements
A 2007 health technology assessment from the Washington State Health Care Authority determined that there was insufficient evidence to make any conclusions about upright MRI’s effectiveness, including whether upright MRI: accurately identifies an appropriate diagnosis; can safely and effectively replace other tests; or results in equivalent or better diagnostic or therapeutic outcomes. (8) Evidence considered the most compelling for this decision included:
- Technology is 10-years old, but no accuracy studies and very few reliability studies
- Of the studies available, most were poor quality and sample sizes were very small
- Image quality is lower and some evidence of higher percentage of individuals not being able to complete the test due to pain from positioning
- Other tests are currently available for diagnosing same conditions, even though it was noted that those tests might also have limitations
- One study that was of higher quality raised the possibility that upright MRI might be less beneficial due to decreased findings
- There are no evidence based clinical guidelines addressing appropriate upright MRI usage.
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