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Novel Surgery Returns Local Nun to Ministry for 30th Anniversary

Protégé of Mother Teresa says robotic technology at Scripps is heaven-sent

Sister Margaret Castro stands outside.

Protégé of Mother Teresa says robotic technology at Scripps is heaven-sent

Sister Margaret Castro of St. Rita’s Parish in southeastern San Diego experienced extreme physical hardship while devoting her life to caring for others, including 14 years helping lepers in India alongside the recently sainted Mother Teresa. 

But just months before the celebration of her 30th anniversary at St. Rita’s, excruciating knee pain from an old injury threatened to sideline the energetic 78-year-old nun. Both of her knees were injured 15 years ago when a stack of folded tables in the school cafeteria fell into her legs. Her left knee had to be replaced immediately, but she waited as long as possible for surgery on her right knee. 

Eventually, she was using a cane and coping with unrelenting pain and grinding in her right knee as she climbed the 21 steps to her office, walked the hallways of the church’s elementary school or visited parishioners in the hospital.

“The pain was excruciating and I was taking pain pills or trying to pretend the pain didn’t exist,” Sister Margaret said. “It was so bad that I couldn’t kneel, and the day came when I couldn’t walk at all.”

Finally, the pain motivated her to see Scripps orthopedic surgeon David Fabi, MD, in December. He told her about a new knee replacement technology, and she thought it sounded worth a try.

Robotic knee replacement eliminated pain

Dr. Fabi used an innovative robotic technology, the NAVIO surgical system, to perform a total knee replacement surgery on Sister Margaret. Approved last year by the Food and Drug Administration for total knee replacement, the portable robotic system enabled Dr. Fabi to capture a 3-D digital picture of the bones and tissue inside the nun’s right knee. The technology identified exactly where he should cut to precisely align the knee replacement, providing similar rotation and flexibility to what Sister Margaret remembers having in her natural knee.

A few hours after her surgery at Scripps Mercy Hospital, a physical therapist had Sister Margaret walking down the hospital’s hallway and up a flight of stairs with the help of a walker. Days later she went to the convent, where she recuperated for three weeks before returning to her duties overseeing religious education and outreach to the Hispanic community.

“The surgery has greatly improved my quality of life because I can do all the things I did before the pain affected me, and now I can walk fast, too,” she said.

3-D technology increases accuracy and precision

Unlike other robotics-assisted platforms, the NAVIO technology does not require a pre-operative CT scan. Instead, the surgeon collects patient-specific data during the procedure through tiny sensors placed on the patient’s knee and leg bones, which communicate with the computer.

“The 3-D modeling robotic surgery system increases the accuracy and precision of total knee replacement surgery to as close to 100 percent as possible,” said Dr. Fabi, who has performed more total knee replacement procedures using this system than any other surgeon in the country. “Earlier generation computer navigation systems only provided data on how to make cuts to the bone in the joint. This new technology helps me achieve my goal of what I call ‘one and done,’ meaning one surgery for the rest of the patient’s life.”


Good for a lifetime sounded great to Sister Margaret. 

“I’m celebrating my 30th anniversary but I have no intention of retiring. Hopefully I’m going to be here, just as fast as I am right now, ministering to people until God calls me home,” said the nun, who has since referred several parishioners and nuns to Dr. Fabi.

Scripps is ranked among the nation’s best for orthopedic care by U.S. News & World Report based on key metrics such as quality, patient outcomes and system capabilities and facilities. 

“It’s wonderful when we are able to help people return to their active lifestyle with this surgery,” Dr. Fabi said. “It’s extra special when we can get someone like Sister Margaret back on her feet, because the community needs her.”