I pride myself on having an extraordinarily high tolerance for medical gore, but I have to admit that the phrase “bone saw” always gives me the willies. Which is probably why I was intrigued when I first heard that there was a company out in Burlington, MA, that makes a new kind of implant for knee surgery—one that can be installed with none or little of what orthopedists so demurely call “bone resection.” That, and the fact that, given family history, I fear that one of these days I’m going to be one of the hundreds of thousands of people in the U.S. each year who winds up having a knee or two replaced.
Indeed, it turns out that the implants that ConforMIS is making offer alternatives to standard total knee replacement. Several of them fall into an emerging category of “resurfacing devices” that cover bone damaged by arthritis or trauma with smooth pieces of plastic or metal—while leaving the bulk of the joint intact. ConforMIS’s trick for minimizing the slicing and dicing that needs to be done to implant these devices, explains Philipp Lang, the company’s chairman and founder, is to tailor each one to precisely fit the patient’s existing anatomy.
“The fundamental challenge is that a joint is a complex 3-D structure, and it has tremendous variability between patients,” says Lang, who in his day job is the director of musculoskeletal radiology at Boston’s Brigham and Women’s Hospital and associate professor at Harvard Medical School. Traditional knee implants are not fitted to a particular patient, so surgeons must cut bone “to fit the patient to the implant.”
What ConforMIS does instead is use data from MRIs or CT scans taken before surgery to generate a 3-D model of a patient’s knee and design an implant to conform exactly to the area in need of repair (hence the first part of the firm’s name—the second part is for Minimally Invasive Surgery). The company then uses computer-driven machining or prototyping tools to fabricate the implant, a process that takes four to six weeks, as well as custom surgical tools for implanting it.
From the patient’s perspective, preserving bone is important for a couple of reasons, Lang says. For one thing, it makes for much faster short-term recovery. Though a central aim of the surgery is to relieve pain, conventional knee replacement leaves a notoriously painful aftermath. Lang says that hard data on recovery is difficult to come by, but one study showed that it took an average of seven weeks for patients to get back to their pre-operative levels of pain. In a clinical trial of ConforMIS’s smallest implant, which doesn’t require any bone resection, patients already showed improvements over their pre-op pain levels at the time they were discharged from the hospital, he says. (ConforMIS’s larger implants do require a little bit of bone cutting, but not nearly as much as a conventional device.)
The other consideration is that orthopedic implants don’t last forever, and many patients wind up needing repeat surgeries down the road. Each time a surgeon cuts the bone to fit it to an implant, “that’s bone you’ve lost for future surgeries,” Lang says. “You’re burning bridges.”
The made-to-order approach has a business advantage as well: it eliminates the need for the company
