Kinematic Alignment - Frequently Asked Questions
What is a custom-fit total knee replacement?
A custom-fit knee replacement is a new technique that for the first time allows the surgeon to match the size and placement of the implant to the patient's unique knee anatomy. This custom-fit knee is made possible using Kinematic Alignment, a new technology developed by OtisMed Corporation.
Methodist Hospital's Orthopedic Surgeon Stephen Howell, MD, who helped pioneer this technology, is the first surgeon in California to offer custom-fit knee replacement with Kinematic Alignment to his patients. Methodist's other surgeons, Steven Barad, MD, and Harry Khasigian, MD, are also offering this technology.
How does custom-fit knee replacement work?
Using the Kinematic Alignment technology, the custom-fit knee replacement is done in three steps. First, a very precise measurement of taken of the patient's own knee using MRI. Second, special computer software uses the MRI to build a 3-dimensional model of that patient's arthritic knee. It then corrects the deformity to restore the patient's normal anatomy. Third, this model is used to help the surgeon determine exactly where bone cuts need to be made to ensure proper implant placement, or fit, for the individual patient.
Why is a custom-fit important in knee replacement?
Just as all fingerprints are unique, so are knees. Recent studies have shown that lower leg alignment varies a great deal from person to person. For example, out of 180 normal knees studied, more than 100 were bow-legged by an average of 2.5 degrees and over 70 were knock-kneed by about 1.5 degrees.
In addition, each patient's pattern of arthritis is different. These differences can have a tremendous impact on knee replacement, since a few degrees of variation in implant placement can lead to a less successful outcome for the patient and shortened implant life.
The Kinematic Alignment technology was developed to address these individual differences by treating each patient's knee as unique.
What are the patient benefits of a custom-fit total knee replacement?
Based on the 100 plus cases performed at Methodist Hospital, patient satisfaction with the Kinematic Alignment procedure is higher compared to other methods. Most patients are off a cane in less than three weeks and are going up and down stairs normally by six weeks. Patients also report that their knee feels very natural after surgery, with no tightness or instability.
How does this differ from the gender knee?
While some implant manufacturers have started developing their products to account for differences between men and women, the implants themselves don't address the very patient-specific nature of knee anatomy. In addition to bow legs and knocked knees, surgeons have seen variations due to things like ethnicity, age and lifestyle. For example, a relatively active 65 year-old grandmother may be different than a world-traveling 55-year old business executive.
The Kinematic Alignment technology was designed to help address these differences.
How else is this approach different from conventional TKR surgery?
Using the Kinematic Alignment technology, surgeons are able to spare a key ligament, called the posterior cruciate, which helps ensure proper alignment and a more natural feeling knee. This ligament is often cut during traditional knee replacement.
With Kinematic Alignment technology, each patient's surgical procedure is very well planned in advance and specific to that patient. Individualized cutting guides are developed to help the surgeon make bone cuts with high precision and little guesswork. This pre-planning and individualization reduces surgical time, meaning that the patient spends less time under anesthesia.
