Hip & Knee Surgery - Orthoworld

EXECUTIVE INTERVIEWcontinued from page 16complexity. We’ve kept it simple. The Kinectiv Technologyimplants and instrumentation have been designed with significantconsultation from surgeons, O.R. personnel and sales representatives.Our goal was a streamlined, simple option for bothsurgeon and patient. Our sole use of the +0 heads gives the systemthat simplicity and eliminates the need for multiple head lengths,complicated charts and head size limitations. We have been quitepleased by the response from surgeons and O.R. teams who havefound that the intuitive and readily apparent 4mm leg length andoffset adjustments help improve operative flow.OPN: Zimmer isn’t the first to develop a mobile bearing knee implant.Why a new generation of mobile bearing knees?HP: There have been several generations of mobile bearingimplants, and as an industry we’ve learned that, for certainpatient demographics, a mobile bearing option can provide amore natural range of motion. As the market leader in total kneearthroplasty, we feel it’s imperative to offer a solution for this marketsegment that builds on the clinical legacy of our NexGen KneeSystem while offering unique and value added technologies. Thenext step is improving upon patient satisfaction and the implantfunction and performance expectations. To this end, the NexGenLPS-Flex Mobile Bearing Knee System (See Exhibit 4.) wasdesigned to accomplish three main goals: (1) to restore naturalkinematics, (2) to accommodate safe flexion to 155˚, and (3) toenable surgeons to utilize Minimally Invasive Solutions procedures.Exhibit 4: The NexGen LPS-Flex Mobile Bearing Knee System.HP: The NexGen LPS-Flex Mobile Bearing Knee System was theresult of our analysis of the effects and component interactionsthat result when knee prostheses undergo deep flexion, beyond120˚. Zimmer’s design allows for safe high flexion as the posteriorcondyles roll back up to 155˚. This higher flexion meets theneeds of patients with active daily living, leisure or work activities,as well as patients whose culture or social customs dictate frequentkneeling or sitting cross-legged.Antecedent mobile bearing designs have failed to address seriousfunctional limitations arising from the kinematics of kneerotation. The problem with competing mobile bearing implantsarises from the central location of the pivot point on the tibialbaseplate.Zimmer has designed the NexGen LPS-Flex Mobile BearingKnee with an anterior pivot (See Exhibit 5.), which is where bodymechanics tell us it should be – near the anterior cruciate ligamentsite. Anterior pivoting replicates the anatomic center of rotationand reduces patellofemoral forces. 8-11 Patellofemoral forces alsoincrease with greater medial/lateral displacement, which researchhas implicated in post-surgical anterior knee pain. Reduction inpatellofemoral forces could reduce patellar complications such aspatellar dislocation, component wear, damage and loosening. 8,9 Ananterior stop on the tibial baseplate effectively prevents the “spinout”seen in competing implants and noted in the literature. 12,13 Inregards to design features which facilitate minimally invasive surgicalapproaches, the height of the anterior trunnion is only10mm, which in combination with our “mini keel” tibial baseplate(See Exhibit 6.) reduces the need for tibial subluxation to insert thecomponents. Another key feature is Zimmer’s enhanced PScam/spine mechanism which, unlike most PS systems, drivesdown the spine of the articular surface, increasing resistance tosubluxation.Exhibit 5: The NexGen LPS-Flex Mobile Bearing KneeSystem with an anteriorpivot point.OPN: Tell us more about the benefits of the NexGen LPS-Flex MobileBearing Knee.OPN: Some companies claim that bone conservation is a key factor inhigh-flex knee implants. These companies criticize femoral designs suchas the LPS-Flex because an additional 2mm of bone must be removedfrom the posterior condyles compared to the standard femoral designs.HP: While bone conservation is always important, Zimmerresearch has shown the removal of an additional 2mm of bone isrequired to optimize the tibiofemoral contact area (See Exhibit 7.)continued on page 1918 ORTHOPAEDIC PRODUCT NEWS • November/December 2009