The NexGen RH Knee features a bone conserving modular hinge design that addresses key issues related to many conventional rotating hinge knee designs. The hinge system utilizes the same stems, cones, patellas, and both Trabecular Metal™* & Precoat augments as the NexGen LCCK Constrained Knee System. Bone cuts for the RH Knee system are similar to those of the LCCK system. This feature allows bone conservation as well as easy intra-operative conversions from LCCK.
Patello-femoral Kinematics
The NexGen RH Knee Femoral Component has the same patello-femoral design as the primary NexGen Femoral Components. The patella is fully supported up to 60° of flexion which increases the lateral subluxation resistance and provides a smooth transition from flexion to extension. This is achieved by the central location of the hinge axis which keeps the femoral condyles in a consistent sagittal plane allowing for more normal patellar tracking.
Condylar Loading
In many conventional rotating hinge knee designs, the hinge mechanism bears the majority of the compressive load until full extension is achieved. Designs that have the center of rotation located posteriorly can cause “booking” of the joint, which may result in stress on the cement interfaces or accelerated polyethylene bearing wear in the hinge. The NexGen RH Knee addresses these concerns as the RH Knee femoral component and articular surfaces are designed to maintain centralized contact throughout ROM (from -3° of hyperextension to 120°) resulting in 95% condylar loading through the tibial condyles.
Modularity
The modularity of the hinge post extension pin was designed to provide ease of implantation without requiring excessive distraction during component assembly and allowing the ability to maintain a minimum jump height of 40 mm. The final linking takes place when the hinge post extension is inserted into the tibial baseplate and tightened.
* The Zimmer Biomet NexGen® Trabecular Metal Tibial and Femoral Cones are for use only with the NexGen Complete Knee Solution System. When used with the LCCK System, the Trabecular Metal Cones are for cementless or cemented use. When used with the RH Knee System, the Trabecular Metal Cones are for cemented use only in the United States
