New Partial Knee Offers More Options for Patients
In 13 years of practice, Stuart Smith, MD, has performed about 5,000 joint replacements of the hip, shoulder and knee.
A partner at Tennessee Orthopaedic Alliance, the board certified orthopedic surgeon cares for patients at Baptist Hospital, Saint Thomas Hospital and Centennial Medical Center where full replacements are often warranted. However, Smith has always had an interest in taking a minimalist approach to optimizing outcomes.
The desire to retain as much of the natural structure as possible led him to mentally design a better mousetrap … or in this case, a partial knee replacement. Several years ago, a corporate representative of Memphis-based Smith & Nephew heard Smith lecture on his ideas regarding potential design improvements. When it came time for the company to work on their new partial knee implant, Smith and four others were invited to be part of the design team. The result is the Journey™ UNI, a unicompartmental knee system, which has been commercially available for a little more than six months.
Smith has already performed a little more than two dozen partial knee procedures … all at Baptist Hospital … using the new UNI design.
"Partial knee replacements, in general, have significant advantages over complete knee replacements in that you are doing as little surgery as possible and still fixing the problem," he said. Smith noted there are three major components of the knee. He estimated roughly 20 percent of the patients he sees are candidates for a unicompartmental replacement because only one knee component is involved.
In addition to a quicker recovery time, Smith noted the partial knee requires a smaller incision with less tissue to heal and a lower probability of infection. He continued, "The longer term advantage is you maintain all the ligaments and muscles in the knee, none of which you have to cut to insert this device, and they feel more natural than a total knee replacement."
Smith said studies comparing full and partial replacements have found patients overwhelmingly prefer the "less is more" approach. "They move better. They have a higher degree of flexion, and they allow for a more active lifestyle than a total knee replacement," Smith noted of partial knee systems.
Despite the benefits, he said the choice to do a full or partial implant really still amounts to a surgeon's preference and comfort level. He added that surgeons who didn't cut their teeth on partial implants during training are sometimes hesitant to use them.
"People say, 'Why not just go ahead and do a full knee?' Well, one way of correcting your knee pain would be amputation … but, of course, that would greatly limit function. That's kind of absurd, but it does illustrate the various degrees of doing things," he said of his answer for choosing a partial over a full whenever possible.
Smith added there is a nationwide trend to use the least invasive method possible to correct a problem. As surgeon awareness has increased, growth in the use of partial knee replacements has outpaced that of full knee replacements in cases where a UNI is warranted.
Although unicompartmental replacements have been available for years, Smith said the Journey UNI incorporates two aspects that differentiate it from other products –– a unique material option and simplified surgical technique.
For candidates who require resurfacing of the knee, pain is typically a result of nerve endings being exposed where cartilage has rubbed off. In general, the solution has been to affix an inert metallic cap so nothing moves against the bone.
With the Journey UNI, Smith explained, "The femoral cap is made out of ceramic materials (OXINIUM –– Oxidized Zirconium). It's actually titanium that has been treated in a certain way so that the surface becomes ceramic. It's got the positive benefit of not having the brittleness of ceramic; but because it is ceramic on the surface, it's incredibly smooth."
He added from an engineering standpoint, the implant is very forgiving in that it allows for slight variations in the alignment without significant deterioration in the wear. Additionally, the new implant allows for higher degrees of flexion, which is particularly germane to the typical partial knee population, which tends to skew younger and be more active.
From a surgical standpoint, Smith said, "I think one reason not every orthopedic surgeon performs these (unicompartmental implants) is the instrumentation and exposure demands can be somewhat intimidating." However, he continued, this new option has the benefit of instrumentation that is extremely simple, straightforward, and reproducible.
And Sometimes More is More
Another benefit of this latest option is that it is the finale in a four-part implant system. Smith & Nephew's Journey™ line now includes: Journey UNI, Journey PFJ (a patellofemoral joint system), Journey Deuce (a bi-compartmental system that preserves the anterior cruciate ligament), and the full Journey BCS (bi-cruciate stabilized knee system). Although each of these types of knee replacements has existed for years through different companies, they haven't been available under one umbrella in a modular format.
"The Journey knee system is the very first system to have all four types of knee replacements," Smith said. "It gives the surgeon all four of those potential types of operations at their hands at the time of surgery, which is really quite powerful."