After 17 operations aimed at trying to save the left leg of Rebekah DiMartino, a mom severely injured in the Boston Marathon bombing more than 18 months ago, surgeons removed the lower part of the limb on Monday in an operation that she says will mark a "new beginning" in her life.

DiMartino was with her son, Noah, and then-boyfriend, Pete DiMartino, at the finish line of the city's iconic road race when the blasts went off on April 15, 2013. They were all wounded in the attack, but Rebekah's injuries were the most serious, with doctors opting to try to salvage her limb.

Pete, now her husband, said later Monday that the below-the-knee amputation at Memorial Hermann Katy Hospital outside Houston was a success. Rebekah joins at least 16 other survivors of the attack who had amputations because of the blasts.

"The fact that I was given a second chance at life that day is something that I will never again take for granted," DiMartino, 27, told NBC News on Saturday ahead of the surgery. "If I have to lose my leg in that process, so be it, because I'm still here."

Since the attack, DiMartino has had multiple procedures within the 17 operations, including the transplant of live muscle from her back to her wounded left foot and the installation of metal plates, screws and rods. She suffered a serious bone infection from the blast, as well as the loss of her fourth and fifth metatarsals on her left foot and a lot of tissue from her left leg, and she was on bed rest for several months.

"I've never been a runner, an outdoors person, but now I want to climb mountains, I want to run marathons. I want to do anything and everything that you can do with your legs, because it makes me appreciate them so much more now."

DiMartino has spent a lot of time in a wheelchair, having had limited ability to walk — with even short attempts at wearing a boot leaving her exhausted and hurting. Pain has been her constant companion, one she is hoping to leave behind with the amputation.

"Even though my leg is being chopped off and I won't be able to walk for a while, it's still a step forward to me," she said, noting that the debut of her next chapter was "such a relief."

Her physician, Dr. Bill McGarvey, said there were still conventional and non-conventional options for DiMartino to pursue with her leg, but he understood she had settled on having the amputation. It's not a given, however, that she will have relief from the pain by having the surgery.

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"I can't guarantee that," said McGarvey, an orthopedic surgeon at Memorial Hermann. "The difficult part about this is that there is sometimes an unpredictability that goes along with these procedures — persistent pain, function and all the things that you would expect.

"The assumption is that you take away the leg and all the problems go away, and it's not that simple," he added, noting issues could arise over prosthetic fitting, wear and practice, for example.

DiMartino is aware of the possible downsides but has also watched as other amputees have moved on with their lives. She wants to do the same and said she has set goals "that push you beyond your limits and get you out of your comfort zone," like participating in next year's Boston Marathon and competing in a triathlon to honor her late grandfather.

"I've never been a runner, an outdoors person, but now I want to climb mountains, I want to run marathons. I want to do anything and everything that you can do with your legs, because it makes me appreciate them so much more now," she said. "I still have a lot of living left to do."

McGarvey said that if all goes well, DiMartino could be taking her first steps three months after the operation.

"I think this is something she is committed to, and I think that with that kind of attitude and drive that she'll actually do very, very well," he said. "If we can get rid of the pain for her, I have no doubt that she's going to be successful."

McGarvey said later Monday that the surgery went well, with no surprises, though he did encounter some small shrapnel – remnants of the blast – in the area where he was removing the limb. DiMartino was awake about 30 minutes after the surgery and will spend a few days in the hospital before going home to recuperate, he said.

DiMartino said she knew the bid to salvage her lower left leg had been difficult on her family, too, who were hopeful she could keep it. Noah, now 7 years old, would cry when she tried to speak to him about the amputation. But in recent days, he has come around to the idea, she said, even deciding that getting a prosthetic was the "coolest thing" because she would become a "half-robot mom."

There have been tough emotional days for her as well, DiMartino said, noting that she constantly recalls the woman who died next to her (one of three people who were killed in the bombings) at the finish line, the sound of the blasts and the aftermath.

"I wonder if that's going to stay with me for the rest of my life, but that same thing keeps me very grounded, and it keeps me very motivated, because if I stop now, it means the terrorists have won, and they will never win," she said.

Although it has been a hard journey, DiMartino has had much to celebrate: her marriage to Pete around the one-year anniversary of the attack and their settling into a new home with Noah near her parents in Richmond, Texas. Pete has taken up woodworking, and Rebekah, who used to work in corporate housing, is beginning to do motivational speaking — a calling she found after the bombings.

This weekend was what DiMartino called her "Left Leg Last Hurrah" — a celebration of the future, rather than a somber goodbye.

She has no regrets about the last year and a half, saying it taught her what it is like to live as a disabled person and brought many new friends into her life. This week, two nurses who cared for her in Boston will be at her side, and other Boston Marathon amputees have offered their help.

This weekend was what DiMartino called her "Left Leg Last Hurrah" — a celebration of the future, rather than a somber goodbye.

"This is a new beginning for me. This is when the rest of my life starts. I've been in a limbo state for so long now that it really is going to be what pushes me forward and what allows me to be able to live my life to the fullest," she said. "It's OK. It really just is a leg."

Gallery:Injured Couple Creates New Life After Bombing