Rep. Gabrielle Giffords (D-Ariz.) is happy but sore after undergoing skull surgery, her doctors said Thursday.

The congresswoman underwent a three-and-a-half hour operation Wednesday at the Memorial Hermann Hospital in Houston to attach a newly-fabricated piece of plastic skull.

The procedure went well and, as a result, she will no longer have to wear a protective helmet, her doctors said.

The surgery was described as carrying minimal risk but is significant because it means swelling is no longer a danger. It brings Giffords one step closer to her release from the hospital after she was wounded in a January shooting rampage in Tucson, Ariz. that left six people dead.

"Nobody is excited to go to surgery but she was pleased the step had come," her neurosurgeon, Dr. Dong Kim, said. "Initially she was in some pain, and had some nausea," after the operation, but "she was happy."

Giffords, 40, has hated wearing the helmet to protect her damaged skull and is eager to be rid of it, according to her chief of staff, Pia Carusone, though Kim did say Giffords will still need it for certain activities in the future.

Her husband, Commander Mark Kelly, was updated on the progress of her surgery while aboard the Endeavour shuttle at the International Space Station.

"She's doing really well, everything went as planned," he said in an interview with PBS NewsHour from the shuttle, "The neurosurgeons are very happy, she's getting back to therapy today [Thursday] so it actually went really, really well," he added.

Kelly had lobbied doctors to not remove his wife's hair for the surgery but Kim explained that to minimize the risk of infection, her head had to be completely shaved.

"Her hair will grow back very evenly and soon," the neurosurgeon said, adding, "I started calling her gorgeous Gabby today. She hasn't looked in the mirror yet but as soon as she does, she'll be very pleased."

Dr. Gerard Francisco, who is overseeing the rehabilitation program for Giffords, reported on her improvement saying she was increasingly "having meaningful and fun conversation" and "has even made some jokes."

Carusone said Giffords is keeping up with current events, noting her boss was interested to learn Donald Trump would not be running for president.

"She's curious and interested ... and misses Tucson," Carusone said.

Giffords' recovery, from an injury that kills 95 percent of those who suffer it, has been described as "miraculous" -- though doctors have not speculated on a date for her release or possible return to work.