Students' Device May Improve Chest Closure After Heart Surgery

To operate on the heart, surgeons usually cut through the breastbone. After correcting the heart problem, they reconnect the sternum by piercing it with steel wires, pulling the bone segments together and twisting the wires tight. Because this half-century-old technique poses some risks to both the surgeon and the patient, undergraduates at The Johns Hopkins University have invented a less intrusive and potentially safer chest closure system that threads locking polymer clasps through the ribs.

The 11-member team's prototype won first-place honors in the university's recent Biomedical Engineering Design Day competition. The project's sponsor, Surgical Transformations LLC, has obtained a provisional patent covering the system. If the idea appeals to enough surgeons, the firm plans to support further research and development to produce a commercial model.

Malcolm Lloyd, a physician and co-owner of the company, said he and his partner, heart surgeon Mark Sumeray, challenged the students last year to devise a better way to close the chest after surgery. "The premise was based on an unmet need identified by cardiothoracic surgeons," Lloyd said. "The students came up with a working prototype that hit all of the engineering requirements we proposed. The end result was better than my partner and I expected, particularly given the limitations they had in terms of resources."

The students produced their prototype, which resembles a stapler and uses standard locking cable ties, for about $1,500. Much of this went to a private prototyping shop that built the device according to the students' detailed design drawings. A roughly 8-inch curved piece extends from the handheld tool to guide the tie between and under the ribs, enabling a surgeon to connect both ends and pull the severed sternum parts toward one another. When one end of the tie is reinserted into the tool and the handles are squeezed, the device operates like a ratchet, tightening the clasp and bringing the pieces of the breastbone firmly together so that the healing process can begin.

In a class called Biomedical Engineering Design Teams, the project was adopted last fall by a group led by Chris Weier, a 23-year-old senior from Sterling Heights, Mich., and Neha Malhotra, a 20-year-old junior from Dubai, United Arab Emirates. As part of their research over two semesters, team members visited a human cadaver lab to study chest anatomy. They conducted tests in a hospital biomechanics lab to see how the polymer ties compared to the steel wires. Members of the team, which included six freshmen, three juniors and two seniors, also worked with a model chest skeleton.

"Everyone was really involved, and everyone made a contribution to the project," Malhotra said. "Getting a provisional patent made the team feel like we really accomplished something."

Weier added: "This was not just a textbook problem. This was like a real-life industrial project with deadlines and patent searches."