The report's authors qualified their findings. For starters, Group Health surgeons are all on salary, so volume of procedures does not influence their paychecks.
Second, it could not be determined whether the patients actually used the DVD or the online tool, or to what extent it may have influenced their decision.
Third, the followup period was six months, after which the patient may have gone ahead and had the surgery. "We cannot exclude the possibility that the decision aid implementation has only delayed the timing of joint replacement surgery," the authors wrote. "It is entirely possible, given the natural history of osteoarthritis, that patients who choose to forego joint replacement will reverse their decision later."
Fourth, Group Health providers have been during this study period moving to medical home payment models, and other initiatives are underway to make doctors and other clinicians aware of care costs and the importance of avoiding unnecessary procedures.
"Although osteoarthritis management was not a specific focus of the medical home initiative, it is possible that better primary care management of osteoarthritis may have contributed to observed declines in joint replacement," the researchers wrote.