New Studies Examine ConforMIS Custom Implant Outcomes

ConforMIS Inc., a developer of customized total knee implant systems, has reported the results from two in-vivo clinical studies comparing the motion patterns of patients treated with the company’s iTotal knee versus off-the-shelf implants. The studies involved the first-ever use of an advanced real-time mobile X-ray fluoroscopy system designed to measure a wider range of natural movements.

Results were introduced among other studies presented during the 2014 International Congress for Joint Reconstruction (ICJR) Pan Pacific Orthopaedic Congress held last month in Hawaii.

Both studies, according to the company, demonstrated that the motion pattern and stability of customized ConforMIS implants, compared to traditional, off-the-shelf implants, more closely behaved like a normal knee. Replicating the motion of a patient’s knee is critical to achieving a more stable, natural feeling knee and achieving normal function.

The ConforMIS total knee replacement is designed to eliminate causes of patient dissatisfaction common with traditional off-the-shelf implants, by matching not only the unique size but also the unique 3-D shape of each patient’s knee.

“The goal of knee replacement surgery is for the patient to ultimately forget about the knee implant,” said Philipp Lang, M.D., MBA, chairman and CEO of ConforMIS. “The ability of the ConforMIS implant to more closely match the motion patterns of a normal knee is further confirmation that individually designed, customized implants are a true breakthrough in knee replacement technology.”

The studies follow a recently presented study at the British Association for Surgery of the Knee (BASK) Annual Meeting that showed 100 percent of patients in a series of 106 ConforMIS iTotal knee replacements reported a normal feeling knee.¹ The new data adds to the growing body of evidence that a customized approach to implant design results in a knee that moves and feels more like a normal knee, company officials claim.

In the first study presented at the ICJR: “In Vivo Kinematics for Subjects Implanted With Either a Traditional or a Customized, Total Knee Replacement,” lead researcher William Kurtz, M.D., evaluated patients treated with the ConforMIS customized implant and compared them to patients treated with one of the leading off-the-shelf implants while they performed a variety of activities.

Results of the study showed differences in the overall motion and pattern between the two subject groups:
• 91 percent of patients with a ConforMIS customized knee experienced a motion pattern and rotation consistent with the normal knee, compared to only 56 percent of patients with an off-the-shelf implant;
• None of the ConforMIS patients had any abnormal lift off of the implant of either the inside (medial) or outside (lateral) portion of the knee, compared to 56 percent for off-the-shelf patients. Abnormal lift off of the implant is an indication of instability (a “wobbly” knee) and abnormal movement of the knee; and
• Patients with a ConforMIS knee achieved greater overall range of motion compared to off-the-shelf patients.

“These findings show that ConforMIS patients experienced motion and stability that is consistent with a normal knee, while patients with an off-the-shelf knee implant experienced knee motion inconsistent with how a normal knee behaves,” said Kurtz, an orthopedic surgeon at Saint Thomas Midtown Hospital in Nashville, Tenn.

In the second study presented at the ICJR, “In Vivo Kinematics for Customized, Individually Made vs. Traditional Total Knee During a Deep Knee Bend and Chair Rise,” lead researcher Harold Cates, M.D., evaluated kinematics of patients with a ConforMIS customized implant versus another off-the-shelf implant while they performed basic movements. Patients were asked to perform a deep knee bend to measure an important function called femoral rollback to better understand if the knee replacement behaves like a normal knee.

Results, according to the company, showed that:
• All ConforMIS subjects experienced posterior femoral rollback of their lateral condyle, consistent with the motion of a normal knee, compared with only 50 percent of traditional, off-the-shelf subjects; and
• Subjects in the ConforMIS arm achieved more natural rotation patterns and more normal contact patterns of the femur (thigh bone) and tibia (shine bone) compared to subjects with an off-the-shelf implant.

The studies are the first-ever results using an advanced real-time X-ray mobile fluoroscopic system developed by Drs. William Hamel and Richard Komistek to evaluate knee motion and kinematics. The mobile system allows researchers to monitor a wider range of natural movement. For example, rather than having patients walk on a treadmill, the mobile fluoroscopy unit follows patients as they walk normally.

Bedford, Mass.-based ConforMIS is privately held. The company’s partial and total knee replacement solutions, the iUni G2, iDuo G2 and iTotal G2, are individually designed for patients, and have been cleared by the U.S. Food and Drug Administration and are CE marked in Europe.

For other ConforMIS-related studies from the ICJR meeting, click here.

For a recent Orthopedic Design & Technology profile of ConforMIS, click here.

References:
1. Kurtz, el al; Early Outcomes Utilizing a First-Generation Customized Patient-Specific TKA Implant, 2014 BASK Annual Meeting