A startup company is taking a customized approach to knee replacement surgery, creating knee implants on demand that exactly match a patient's anatomy. The company, ConforMIS, based in Burlington, MA, is bringing the technology of rapid prototyping, which converts a three-dimensional computer design into a physical object, into the field of orthopedics. The company believes that such custom-made implants can make knee replacement surgery faster, more accurate, and less traumatic to the patient.

Knee replacement surgery repairs damage and relieves pain in patients with severe osteoarthritis or knee injury. Total knee replacement involves removing diseased cartilage and bone from the surfaces of the knee joint--the thigh bone, shin bone, and kneecap--and replacing them with an artificial joint made from a combination of metal and plastic. A partial knee replacement can also be performed on one part of the joint.

Typically, a surgeon chooses an artificial joint from several options of different sizes. ConforMIS, however, creates a custom implant based on imaging data of a patient's knee joint, a technology that the company calls iFit. ConforMIS transforms images from CT or MRI scans into a three-dimensional computer model using computer-aided design (CAD) software, which serves as a template for manufacturing the implant.

Philipp Lang, president and CEO of ConforMIS, says that typically, surgeons must shape the patient's bone to fit the implant. Because the bone-facing side of ConforMIS's implant is matched to the patient's anatomy, it can reduce the amount of bone that the surgeon must cut. On the joint-facing side of the implant, Lang says, "we want to re-create the geometry that the patient had before he or she developed arthritis." He says that the ability to fit the implant to the patient without removing excess bone will speed recovery time and lessen pain.

Andrew Freiberg, an orthopedic surgeon who heads the joint replacement services at Massachusetts General Hospital and is not involved with the company, says that ConforMIS is an early example of an approach that has the potential to be important in the orthopedic field. However, he adds, "I'm not aware of any study that shows that custom-made implants give a better outcome" than traditional ones do. Lang says that the company is working with medical centers to conduct studies that will gather data about their outcomes.