Daily Bulletin 2015

MRI Effective in Detecting Adverse Reactions Around Arthroplasties

Thursday, Dec. 03, 2015

Hollis G. Potter, M.D.

Hollis G. Potter, M.D.

MRI is the most accurate means by which to detect adverse local tissue reaction (ALTR), tissue damage and bone loss around arthroplasties, according to presenter Hollis G. Potter, M.D., during her musculoskeletal keynote address on Wednesday.

"It's been shown to be the most sensitive test of all the other radiologic tests we have to really detect the magnitude of ALTR around implants," said Dr. Potter, chair of the Department of Radiology and Imaging and Coleman Chair in MRI Research at Hospital for Special Surgery (HSS) in New York City.

Dr. Potter began using MRI for arthroplasty around the turn of the millennium. At the time she said it was considered "crazy."

"The idea of putting something metal, like a joint replacement, into a very large magnet seemed crazy," Dr. Potter said. "There was concern that it would harm the patient. What we found was not only was it safe, it is also very efficacious."

ALTRs occur with all fixed- or mobile-bearing constructs in symptomatic and asymptomatic patients. Arthroplasties generate a small amount of metallic debris, which in most cases does not affect the patient. But in a small percentage of people, the immune response generated by the host reacts to the particles and creates areas of tissue necrosis.

"This is devastating for patients. For example, all the muscles around the hip can be destroyed. It requires additional surgery, which is associated with greater patient morbidity," Dr. Potter said.

Dr. Potter's research also determined that differences reflect variable host-mediated response to mount discernable synovitis patterns on MRI; maximum synovial thickness is highly correlated with a diagnosis of aseptic lymphocytic vasculitis-associated lesions (ALVAL) in patients with a modular head-neck and neck-stem implant; MRI/ultrasound protocols must allow for thickness measurements to be clear; and radiographic measurements, clinical symptoms or serum ion levels alone do not predict the presence and extent of wear-induced synovitis.

Using MRI has benefits beyond the patients—it can create a new revenue stream for radiology. She said she scans about 10-to-15 arthroplasties a day at HSS as part of her practice, aside from her research duties.

"It's opened up a whole new market for the business of imaging," Dr. Potter said in an interview before the presentation. "It's something that was nontraditional. Many people feel uncomfortable using these new areas of MR, but we're trying to push the envelope."

She added the orthopedic community already recognizes MR imaging as an effective tool for which to assess adverse reactions to the arthroplasty. While it isn't yet widespread in radiology, more places are seeing the value in utilizing it, including Dr. Potter's institution.

At HSS, patients with painful implants receive a radiograph exam to determine if there is an obvious fracture. After that they go directly for MR.

"MR is the accepted means by which they evaluate any kind of component – whether a shoulder or knee or hip – for patients that are dissatisfied with their implants but the clinician can't explain the cause," Dr. Potter said. "It has revolutionized the field."

Question of the Day:

The headphones patients usually wear while undergoing an MRI don't fit under our new head coil. Can I scan patients safely without them?

Tip of the day:

Power Doppler ultrasound can be used to image low-flow shallow vessels because it is independent of flow direction and angle.

The RSNA 2015 Daily Bulletin is owned and published by the Radiological Society of North America, Inc., 820 Jorie Blvd., Oak Brook, IL 60523.