Weight-bearing MRI leads to musculoskeletal pain insights

The 0.6T Fonar Upright MRI is not in the same class as 3T scanners, but it features capabilities superconducting technologies can't match. High-field imaging is performed with the patient relaxed in a supine position. Upright imaging is conducted while the patient sits, stands, or flexes in a weight-bearing position to duplicate the conditions that cause his or her pain.

Upright MRI users say it excels in its niche. Its resolution is high enough to identify protruding discs, bone fractures, and meniscal tears, and its ability to image patients who are standing or sitting allows it to uncover pathology hidden when they are evaluated while lying down.

Research suggests that weight-bearing MRI is on the right track. In a 1999 study, Hans-Joachim Wilke, Ph.D., a physicist with the Institute for Orthopaedic Research and Biomechanics in Ulm, Germany, discovered that intravertebral pressure in the lumbar spine while the subject was seated was 11 times higher than when the subject was prone.

Dr. Francis W. Smith, a clinical professor of radiology at the University of Aberdeen in Scotland, operates the only Upright MRI scanner in a university environment. At EuroSpine 2007, Smith and Dr. Sandro Galea-Soler described how upright imaging revealed relevant lumbar spine abnormalities in 34 of 63 patients (54%) after a recent nondiagnostic conventional MR scan. Interpretation involved viewing 11 sagittal T2-weighted and three axial T2-weighted images, each through the lower five intervertebral discs in supine, neutral seated, flexion, and extension positions.

Most abnormalities were detected with the patient in a seated position, particularly in extension. Imaging depicted 17 cases of spinal instability with hypermobile intervertebral discs, 24 lateral disc prolapses, and seven central disc prolapses.

A study by Smith and Dr. Efthimios J. Karadimas at the University of Aberdeen in 2006 established that segmental motion in 30 patients with low back pain was related to the degree of disc degeneration. The results suggested that upright MRI offers patients with low back pain and sciatica the only way to obtain an accurate assessment of the spine, according to Smith.

Dr. Jean-Pierre Elsig, an orthopedic surgeon in Zurich, presented results at the 2007 European Society of Neurology meeting from a prospective study of 59 patients with neck and arm pain that demonstrated the superiority of upright MRI over recumbent imaging for diagnosing foraminal cervical stenosis. All the subjects were referred to Elsig's clinic after a negative recumbent MRI of the cervical spine.

The upright MRI studies depicted one to four foraminal stenoses in each of 37 patients. Twenty-four abnormalities appeared during extension, three with flexion, five with flexion and extension, three during rotation, and two during multi-axial positioning, Elsig said. The results suggested to Elsig that upright MRI, when available, should be considered mandatory for patients with position-dependent symptoms.

MISSING SOURCE OF PAIN

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It indirectly confirms that conventional MRI misses many spinal injuries, according to Dr. Sana Kahn, chairman of TrueMRI, a chain of 12 Upright MRI facilities in California and Nevada.

The AMA Guides notes that no pain-producing trauma can be found for 85% of patients who complain of back pain. It reports several pages later that the failure of medical and surgical investigations may result from looking at the wrong place and at the wrong time, he said.

"What we are saying is that patients are being examined in the wrong position," Kahn said.

To demonstrate the point, Kahn displayed a recumbent MR sagittal view of the lumbar spine showing an intervertebral protrusion above L6 adjacent to the same views of the patient taken in a weight-bearing seated position where protrusions at L4, L5, and L6 are conspicuous. The failure to appreciate the additional pathology could lead to failed surgery, a recurrence of pain, and a surgical follow-up.

"The cost associated with this is significant," Kahn said. "The second surgery is always harder than the first because of scar tissue, and the patient is likely to be skeptical about the surgeon because of problems with the first surgery."

The value of imaging while joints are bearing weight applies to knee imaging as well. One patient questioned the need for surgery for an anterior cruciate ligament tear. Meniscal alignment was considered unremarkable on images acquired with the patient in a supine position, Kahn said. The alignment of the femur shifted, however, when imaging was repeated when the patient was standing. The posterior aspect of the lateral meniscus shifted beyond the tip of the plateau.

"With this additional information, the decision favoring surgery became easy," Kahn said.

BRACHIAL PLEXUS INJURIES

The focus of Dr. Rahul K. Nath's practice at the Texas Nerve and Paralysis Institute in Houston is on the treatment of obstetrical brachial plexus injury (OBPI). His corrective surgical approach for about half of the 20 patients he treats every month relies on Upright MRI. The initial injury occurs at birth, and resulting bony abnormalities are usually treated during childhood, though surgeries can be required any time from infancy to adulthood.

Although the gross glenohumeral incongruence from OBPI can be detected with a clinical exam, it is important to know the precise relationship between the humeral head and the glenoid fossa before performing surgery, Nath said. Surgical relocation of the displaced head may be required to obtain the best possible long-term outcome.

MRI is the modality of choice for evaluating shoulder deformities, but conventional recumbent MRI is poorly suited to display OBPI, he said. Incongruities are not fully revealed without the effect of gravity, and the arm is usually placed in internal rotation when imaging is performed with the patient in a recumbent position. Upright MRI is performed with the shoulders hanging in a natural position to depict the extent of inferior subluxation.

A drawback to upright MRI is the increased potential for motion artifacts, especially when scanning young children, who often have trouble staying still. Choosing the right protocol, however, can minimize this problem. Sterling imaging quality, however, is not essential for these presurgical scans. Upright MRI is mainly used to examine the relationships between large structures, such as how the head of the humerus fits into the glenoid. It may be basic imaging, but Nath considers it indispensable.

Mr. Brice is senior editor of Diagnostic Imaging.