It's not often that Mad magazine gets referenced in serious health policy circles. But the release last spring of dense draft regulations launching a key health reform component -- accountable care organizations -- unfortunately spurred comparisons to the magazine's mythical game of "43-man squamish," whose rules were deliberately made so convoluted that no one could figure out how to play.

Seven months later, the oft-maligned federal agency charged with writing these rules is no longer fielding Alfred E. Neuman jokes. Instead, it's the deserving recipient of thank-you letters for the dramatic improvements made since March to regulations for the pioneering Medicare Shared Savings Program.

Last week, the Center for Medicare and Medicaid Services (CMS), released the final rules for this voluntary and innovative program, which encourages hospitals, physicians and other providers to band together and assume responsibility for improving the health of a certain number of Medicare patients. These accountable care organizations, or ACOs, will be rewarded for improving patient outcomes. That will make this program, slated to begin in 2012, an early effort at payment reform. The nation's current piecemeal payment system is one of the main drivers of its soaring health care costs, because providers are rewarded for more care instead of better care.

It is clear from the changes that the CMS listened to the feedback provided by health industry leaders, many of whom looked at the rules and concluded that few providers would want to participate. There was a real risk that this promising new program would be stillborn.

Among the key changes made since last spring: reducing financial risk for participating providers, allowing providers to more quickly share in the savings they achieve, and reducing the number of ways that providers are gauged on the quality of care they provide. The number of these measurements has dropped from 65 to 33, which is still a healthy number. The remaining measures -- such as hospital readmissions or the percentage of patients who get cancer screenings -- are also robust gauges of patient health, according to Mark Zezza, a senior policy analyst with Commonwealth Fund.

Federal officials also expanded eligible ACO sponsors to include community health centers and some rural health clinics.

The scope of the changes made to the rules since March is almost unprecedented. The thoughtful improvements will likely entice more providers to form or join ACOs. The changes should also help calm concerns about federal agencies' ability to translate the legislative language of the massive 2010 Affordable Care Act into practical guidelines.

"It is my impression that you have succeeded in making the ACO regulations workable and attractive enough to garner an initial volume of voluntary participation," said a thank-you letter sent to the CMS this week by Donald Fisher, the president and CEO of the American Medical Group Association, whose members include some of the nation's most prestigious providers.

The changes also drew praise this week from Minnesota health care leaders, including Park Nicollet and Fairview Health Services. Fairview CEO Mark Eustis said Friday that his organization is still reviewing the new rules, but added that he is optimistic about participating in the program.

The Medicare Shared Savings program is estimated to save about $470 million by 2016. Federal officials are hopeful that as many as 240 ACOs will participate in the program by then. The ACO rules are still no easy read, and there's a steep learning curve ahead, but the regulatory changes will get the program off to a healthier start.