He calls it innovative. Others call it a big risk. In any case, the stem cell procedure that Governor Rick Perry of Texas had last month was an unapproved experimental way of fixing a common malady: a bad back.

Perry, the newest GOP presidential candidate, has access to the best possible care. Yet he and his doctor chose a treatment beyond mainstream medicine: He had stem cells taken from fat in his own body, grown in a lab, and then injected into his back and his bloodstream during a July 1 operation to fuse part of his spine.

The treatment carries potential risks ranging from blood clots to cancer and may run afoul of federal rules, doctors say. At least one patient died of a clot hours after an infusion of fat-derived stem cells outside the United States.