It is the summer of 2023, and Dr. Stephen Smith sits face-to-face with a model skeleton in the Engineering North building on the University of Notre Dame campus.

Smith is a neurosurgeon at Beacon Health System’s Memorial Hospital in downtown South Bend, Indiana, about a mile southwest of the University’s campus. He is talking with Ryan Roeder, a professor of aerospace and mechanical engineering, about a spinal fusion surgery Smith had just performed using a brand-new type of implant. Although he is looking at bones, it is clear that where others might see death, Smith sees a system teeming with life.

“Bone is an active organ,” Smith says, “and it undergoes continuous remodeling.”

“Remodeling” is not just an apt metaphor; it’s a technical term for the three-part biological process whereby cells digest old bone and deposit fresh, hardened bone in replacement. Remodeling is a key word for this surgery, because for the surgery to be successful, bone has to fuse with an implant—a lifeless material that Smith must insert into the living system of vertebrae and nerves that make up the cervical spine.

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Originally published by Brett Beasley at news.nd.edu on June 05, 2025.