Extremity Imaging improves Rheumatoid Arthritis care

Nancy Walsh

Supplementing standard x-rays with extremity magnetic resonance imaging for the in-office diagnosis and monitoring of patients with rheumatoid arthritis could significantly improve the quality of care, according to Dr. Norman B. Gaylis, a rheumatologist in private practice in Aventura, Fla.

With biologic therapy having revolutionized the treatment of rheumatoid arthritis (RA), the key concern with regard to treatment decision making now is the early identification of erosive disease, Dr. Gaylis explained.

“We’re faced every day with the dilemma of which patients to put on a biologic agent. I think most rheumatologists at this point would agree that if you see erosions you are more likely to go with a biologic agent rather than staying with a conventional disease-modifying drug,” he said.

But early erosions and other early poor prognostic signs such as bone edema and synovial inflammation extending into bone and marrow cannot be seen on standard x-rays.

Therefore, by the time these erosions can be seen radiographically, it’s often too late—the damage has already been done, he explained.

Unlike x-ray, magnetic resonance imaging can detect early bone changes, where the bone marrow is being replaced by inflammatory synovial tissue, a process that results in the penetration of the cortical barrier, the invasion of the cortical bone, and exposure of the marrow to certain inflammatory triggers (J. Immunol. 2005;175:2579-88).

That MRI is more sensitive than radiography for detecting synovitis and marrow edema is not in question.

However, the conventional large-magnet high-field machines are typically utilized in hospital diagnostic facilities and are impractical for day-to-day-use in rheumatology, Dr. Gaylis said in an interview.

What’s more is that patients also find these large-magnet high-field machines very uncomfortable, especially since the position that is required for evaluation of the hand—similar to a swimmer’s position—is just about intolerable for a patient who has been diagnosed with active rheumatoid arthritis to maintain for any significant length of time, he said.

The recent introduction of smaller, less expensive, in-office MRI units designed for use on the extremities—already popular among orthopedic surgeons—eliminates these obstacles to access and comfort.

Approximately 100 rheumatology centers in the United States now use them.

Studies have shown that the results obtained with these extremity MRIs in the evaluation of rheumatoid hands are equivalent to those obtained with the standard units.

In one study that compared extremity low-field MRI with conventional MRI and radiography, sensitivity and specificity for both types of MRI read by more than one radiologist exceeded 90% (Ann. Rheum. Dis. 2005;64:1280-7).

The American College of Rheumatology (ACR) has remained skeptical about the utility of extremity MRI. In a white paper 2 years ago, the ACR indicated that, in their view, more work needed to be done to establish the validity of extremity MRI for RA.

Two central questions raised by the naysayers, according to Dr. Gaylis, are whether the MRI findings, undetectable using x-rays, are indeed erosions and whether these MRI findings are consistently reproducible from center to center and radiologist to radiologist.

In an editorial titled, “Magnetic Resonance Imaging in the Evaluation of Bone Damage in Rheumatoid Arthritis: A More Precise Image or Just a More Expensive One?” investigators from the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health noted that an early study found that when individual MRI lesions were tracked over 2 years, only one of four erosions detected on MRI indeed progressed to become radiographic lesions.

The investigators wrote, “Since the pathophysiologic basis of these ‘erosion-like lesions’ has not been determined, it is unclear which MRI lesions are destined to become ‘radiographic lesions’ and what the significance is of those MRI lesions that do not progress to become radiographic erosions” (Arthritis Rheum. 2003;48:585-9).

An answer to the question of whether MRI-detected erosions and edema are valid signs of early RA, however, was recently shown in a study in which patients scheduled for joint replacement surgery underwent MRI the day before surgery.

Following removal, sequential sections of the joint were analyzed histologically for bone marrow changes. The erosions and edema that had been detected on MRI clearly correlated with inflammation of the bone marrow and synovium (Arthritis Rheum. 2007;56:1118-24).

“Finally, some proof,” commented Dr. Gaylis.

Another advantage of using extremity MRI early in disease is to encourage patient adherence to therapy. The situation is very similar to what happened with bone densitometry for osteoporosis, according to Dr. Gaylis.

“When bone density measurement first was available, the only treatment for osteoporosis was calcium as well as the off-label use of medications such as sodium fluoride and etidronate disodium,” said Dr. Gaylis.

“Since bone densitometry was introduced, there has been an explosion of new medicines. We also have learned to make the diagnosis earlier and to more closely monitor disease activity, and it has certainly helped with patient compliance,” he added.

Patients will be much more inclined to continue taking their medication if they can see concrete results, he added.

That MRI can document the beneficial effects of early treatment also has now been confirmed in a retrospective study involving 48 patients in a single practice who were receiving infliximab.

The patients’ mean age was 58 years, and all fulfilled the ACR criteria for RA. The median infliximab dosage was 4 mg/kg, and the majority of patients also were receiving methotrexate in a median dose of 15 mg/week and prednisone in a median dosage of 10 mg/day.

Of the total of 83 baseline MRIs, 64 (in 41 patients) were abnormal.

Follow-up MRIs showed regression of joint erosions in nine metacarpophalangeal joints, in eight carpal bones, and in one metatarsophalangeal joint (Mod. Rheumatol. 2007;17:273-8).

“In-office MRI demonstrates subtle changes in erosion morphology in RA patients at the time of diagnosis and in response to therapy,” wrote Dr. Gaylis, who was the lead author of the study.

Reimbursement remains a concern, however. Because the ACR did not endorse extremity MRI for RA, and classified it as an unproven technology, reimbursement has been denied by insurers in many cases.

But this is changing, as more evidence accumulates in the literature and with the establishment of the International Society of Extremity MRI, which will hold its first meeting in the spring of 2008, he said.

And further acceptance can be expected shortly as the new society develops special training courses, as individual sites gain certification, and as the overall quality of services becomes more standardized across the board, according to Dr. Gaylis.

View full-size image.

Baseline T1 image (left) reveals erosions in the second & fourth metacarpal heads, which have healed on follow-up MRI (right). Courtesy Dr. Norman B. Gaylis

View full-size image.

T1 (top) and STIR (bottom) images reveal erosions throughout the proximal and distal carpal rows. Courtesy Dr. Norman B. Gaylis

Article published in Rheumatology News, Volume 6, Issue 9, September 2007

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