An AAOS-sponsored study of MRI use by orthopaedic surgeons found that owning imaging equipment made no difference in utilization behavior, when controlling for other variables. Reproduced from Zigler JE, Eismont FJ, Garfin SR, Vaccaro AR, eds: Spine Trauma 2, Rosemont, IL, American Academy of Orthopaedic Surgeons, 2011, P 58.


Published 3/1/2014
Julie Williams; Elizabeth Fassbender

Study of Medicare Claims Data Focuses on MRI Use

AAOS-funded study supports retaining IOAS exemptions

According to a new study of Medicare claims data on in-office magnetic resonance imaging (MRI) equipment ownership among orthopaedic surgery practices, no statistically significant differences in MRI utilization were found between orthopaedic surgeons who own MRI equipment and those who do not.

The study, which was funded by a grant from the American Association of Orthopaedic Surgeons (AAOS) State Legislative and Regulatory Initiatives Committee, found no statistically significant difference in the MRI utilization behavior of orthopaedic surgeons who obtain an on-site MRI and those who do not, when controlling for other variables such as practice size and payer mix. The findings indicate that any changes in Medicare policy related to the current law, which allows self-referral for certain physician activities such as imaging (as well as in-office physical therapy services, in-office pathology, and in-office provision of durable medical equipment), will not lead to reduced advanced imaging utilization.

Current law, commonly referred to as the Stark Law, prohibits so-called self-referral (a physician’s referring a patient for ancillary services to a provider or facility with whom the physician has a direct financial relationship). However, it also contains an exception that allows physicians to provide imaging and physical therapy services in-office, which is vital for providing efficient diagnoses and treatments.

This in-office ancillary services (IOAS) exception has been under scrutiny from both the administration and members of Congress as a potential cost-cutting measure. In a 2013 report, the Congressional Budget Office (CBO) estimated that removing imaging, physical therapy, and radiology services from the IOAS exception would save approximately $1.8 billion over 10 years. The AAOS has consistently held that such scores are incorrect, but until now, had no data to back up those assertions.

“We believe that once this study is finalized, it will provide significant statistical information to show that owning imaging equipment does not lead to increased utilization, as sometimes is suggested,” said Stephen M. McCollam, MD, past chairman of the State Legislative and Regulatory Initiatives Committee. “In fact, limiting in-office ancillary services would result in a number of negative consequences for both patients and physicians. Even payers may be negatively affected, due to increased costs from advanced imaging performed in higher cost facilities, with no guaranteed reduction in imaging utilization at all.”

Limiting the IOAS exception also results in lower quality care and higher costs to patients. Without access to in-office ancillary services, patients would be forced to receive ancillary services in new and unfamiliar settings with the probability of a less precise diagnosis, increased inefficiencies, and barriers to appropriate screenings and treatments. For some of the most vulnerable populations, such as the elderly or those with mobility issues, the IOAS exception is critically important because it also eliminates scheduling delays, prolonged waits, and the need to travel to other offices.

Multiple cohorts used
The study’s approach was new and more robust than previous studies because it used a matching process that compared truly similar practices. The study created multiple cohorts within the division of practices that owned an MRI or did not. These more narrow cohorts were based on the most salient practice characteristics.

For example, within the two major ownership cohorts (MRI or non-MRI), there were smaller cohorts based on the number of physicians in each practice. This enabled direct comparisons of MRI practices with multiple physicians with non-MRI practices with the same number of physicians. Previous studies did not have an appropriate comparison group and/or did not follow physician practices longitudinally.

The study involved a web-based survey of orthopaedic surgery practices to determine if and when the practice first acquired onsite MRI capacity. Then it built on the survey results by obtaining Medicare claims data for a sample of physicians affiliated with orthopaedic practices before and after onsite MRI acquisition as well as for a comparison sample of physicians in orthopaedic practices without onsite MRI capacity. This enabled them to investigate any changes in patterns of MRI use associated with the acquisition of onsite MRI capacity.

In all of the models, the findings indicated that the estimated impact of acquiring onsite MRI capacity on the change in Medicare MRI volume is consistently small and not statistically significant.

The study was conducted by Oxford Outcomes, with lead researcher Robert L. Ohsfeldt, PhD, of Texas A&M University. It was funded by a grant from the AAOS State Legislative and Regulatory Initiatives Committee.

Next steps
AAOS has started selectively sharing the preliminary results with targeted members of Congress and influential staff. Their response indicates that the study will be an extremely effective tool in the battle to protect the IOAS exemption.

In February, Dr. McCollam, James J. York, MD; Lawrence S. Halperin, MD; and Wilford K. Gibson, MD, met with several members of the Senate Finance Committee, including Senators Ben Cardin (D-Md.), Chuck Grassley (R-Iowa), Mike Enzi (R-Wyo.), Bill Nelson (D-Fla.), Johnny Isakson (R-Ga.), Mike Crapo (R-Idaho), and Rob Portman (R-Ohio) to brief them on the study. The AAOS has also met with staff from the President’s Office of Management and Budget, which last year recommended closing the IOAS exemption. AAOS is also planning to meet with the Congressional Budget Office, the General Accountability Office, and the Medicare Payment Advisory Commission.

When the study is finalized, it will be made available to all congressional staff on the relevant committees, with the ultimate goal of being published.

For more information on the IOAS, visit the Issues page of the AAOS government relations website,

Julie Williams is the senior manager, government relations, and Elizabeth Fassbender is the communications specialist in the AAOS office of government relations.

Additional Information
IOAS one-pager

Imaging services