Knee replacement, or arthroplasty, is one of the more common orthopedic procedures performed in the United States, with over 600,000 such procedures performed annually. Most commonly, knee replacement is indicated due to painful and debilitating osteoarthritis, and while this surgery was historically reserved for elderly patients with severe joint disease, knee replacement is becoming more and more common among individuals in the 45-65 year old range who develop arthritic disease and want to maintain their active lifestyles.
The first knee replacement was performed in 1968 and since then the technology of knee arthroplasty has been continually evolving. Traditionally, surgeons work with manufactured implants in a range of sizes, surgically resurfacing the articulating surfaces of the patient’s knee to accommodate the closest fitting implant size. This method can often result in painful implant overhang or joint instability requiring revision. Customized implants have been available, but mostly for rare cases and at great expense. In the late 1990s computerized tomography (CT) and magnetic resonance imaging (MRI) data were beginning to be utilized to create customized tibial and femoral cutting guides to align standard implants to patient’s articular surfaces. Individualized instruments evolved from this technology. ConforMIS Inc. (www.conformis.com) has taken the next step by using imaging technology and proprietary software that they have named the iFit ® system to create patient specific implant and surgical instrumentation sets. The company currently offers three customizable models, the iTotal®, iUni® and iDuo®, representing total and uni-compartmental replacement options respectively with the “i” standing for individualized. This is unique in that the implants themselves are individually designed based on digital 3D images from a CT scan of the patient’s knee. Using an initial CT scan, a patient’s customized implants, instruments and cutting guides are can be designed using the ConforMIS software.
Dr. Wallace Huff is an orthopedic surgeon who practices in Lexington at St. Joseph’s East while also maintaining a patient base in Corbin and Somerset. He began using the ConforMIS knee implants in 2013 and has seen such positive results he is now doing two or three ConforMIS replacements weekly, in addition to traditional knee arthroplasty. For new patients, he finds that 85 to 90 percent are candidates for ConforMIS customized implants versus the traditional “off the shelf” implants. Huff says that the ConforMIS implants are especially suited for younger patients, (less than 70 years old) partly because the customized fit of the replaced joint allows superior mechanical alignment which translates into enhanced stability and balance during activities such as stair climbing, bending and kneeling. Another huge benefit of the customized implants is that they are thinner than traditional implants, requiring less resection of native bone and cartilage during surgical placement. This results in less bleeding and preserves patient bone stock, if there is need for further revision, as often is the case, 15 to 20 years down the line.
Additionally, with traditional “off the shelf” implants surgeons often have to do extensive ligament and soft tissue release in order to approximate the native joint anatomy—the result often being that the ligament tension is still slightly off and the replacement knee doesn’t feel completely balanced during flexion and extension. Because the ConforMIS implants are designed and created for a precise fit to the patient’s anatomy, the native ligaments are often already the appropriate length to accommodate the new hardware without the need for extensive manipulation by the surgeon. Huff says that maintaining the native ligament tension allows him to achieve a more anatomic result with a joint alignment and function closely resembling the pre-deformity knee. This provides a great advantage to patients with ConforMIS implants who experience enhanced balance and stability. Dr. Huff has several patients with both a traditional knee replacement and a ConforMIS replacement and these patients say their ConforMIS knee “feels more like my knee.”
Huff believes that tailor made implants are part of a growing trend, improving the quality and efficiency of knee arthroplasty. Most insurance plans cover the customized implants because ConforMIS has priced their technology competitively. The operating room costs can be extensive with traditional “off the shelf” implants, requiring multiple instrument trays and extensive operative manipulation required to achieve balanced joint alignment with the implants in place. The customized all-inclusive implant and instrument package shipped from the manufacturer benefits the hospital by eliminating many of these challenges, increasing intra-operative efficiency and reducing pre- and post-operative maintenance costs. As is, the procedure itself takes 1.5 hours in the operating room with one or two days in the hospital. Huff anticipates that in the near future, as this trend of customized, streamlined arthroplasty continues, knee replacement will commonly be performed as an outpatient procedure.
A video from ConforMIS Inc. showcasing the iTotal can be seen at: http://www.conformis.com
By Dr. Jenny Wheeler