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The APEX PS Knee™ was designed to address the needs of today’s high demand patient.

Key design features of the APEX PS Knee include:

  • Bone Preserving Box Cut
  • Extended Patella Track
  • Advanced Cam and Post Geometries
  • High Flex Design

Dual Dovetail Locking Mechanism
PS-locking

  • Secure Insert Placement: The entire range of APEX Knee System Inserts load onto our patented Dual Dovetail Locking Mechanism anteriorly, and are locked into place using a Morse tapered bolt.
  • Minimized Motion and Wear: The Dual Dovetail Rail and Groove System has been designed and extensively tested to minimize micro motion, and the potential of backside wear.
  • Reliable Fit: The Morse taper on the bolt prevents the bolt from loosening.

Precise Femoral/Tibial Matching

APEX Knee™ tibial inserts are designed to precisely match the size of the tibial insert to the femoral components. This matching optimizes contact areas, resulting in contact stresses lower than 15MPa in extension. This precise matching is unique in that the femur and tibia can be sized independently. The full range of 9 femoral sizes allow the best possible coverage of the knee joint.

Ps-insert-comparison

Femoral Tibial Matching Options:

  • Versatile Tibial Insert Pairing: Tibial inserts can be one size higher or any size lower than the tibial tray size.
  • Maximized Coverage: Tibial/ insert sizing options allow the tibial tray with the best possible coverage of the tibial plateau to be used with an insert that matches the femoral component.
  • Un-compromised Performance: Deep spherical condyles allow natural knee kinematics, as femoral rotation (< 7°) can still be achieved in flexion, while maintaining consistent femoral contact and even stress distribution.

Asymmetric Implants & “Plus” Sizing

PS-Asymmetry

The asymmetry of both the femoral and tibial components is a result of a highly detailed intra-operative anthropomorphic study.* Matching the left and right geometry, as well as AP/ML implant proportions to patient anatomy provides the best possible component fit and stability.

In addition to asymmetric components, intermediate, or “Plus”sizes are available to address different femoral structures.

“Plus” Size Option Benefits:

  • Maintain Box Cut: Utilize a thinner anterior flange and a larger A/P to M/L size ratio while maintaining the same box cut.
  • Intra-operative Flexibility: Give surgeons the option to intra-operatively change femoral size without having to re-cut the femur.

ps-sizing

* Data on file at OMNIlife science™, Inc.

 

The following characteristics set the APEX PS Knee apart from the competition:

 

Redefining the PS Knee “Box Cut”

ps-box-cut

A traditional “box cut” is both imprecise and leaves sharp edges that can create undesirable stress risers in the distal femur.

Cylindrical resection of the APEX PS Knee™ cut allows:

  • Smooth Line: Sharp edges are eliminated with a cylindical cut.
  • Force Distribution: The bone distributes forces evenly and effectively.
  • Bone Preservation: Utilizing of the natural shape of the intercondylar fossa, the APEX PS Knee can preserve as much bone stock as possible, reducing the risk of intraoperative fractures.[1]

PS-Graph

 

The Apex PS Knee’s box cut geometry grows proportionally with femoral size, minimizing bone loss without compromising stability.


APEX PS Knee Cut Comparison Chart

1. Haas, Nelson, Laskin: “Posterior stabilized knee arthroplasty: an assessment of bone resection” The Knee 7 (2000) 25-29.

 

Advanced Cam + Post Interface

Historically, PS Knees have been associated with polyethylene wear and fractures of the post. This has led to osteolysis and premature complications.[2]

To address the issues of wear and post fracture, the APEX PS Knee has:

  • Minimized Contact: The rounded post of the APEX PS is designed to alleviate point contact.
  • Eliminated Articulation: With the cam engaging at >80° flexion, there is no cam and post articulation during normal gait.
  • Stress Reduction: The rounded cam is located on the posterior 1/3 of the tibial plateau, and is designed to roll down the post, limiting stress and maximizing jump hight during flexion.
  • Increased Post Support: The APEX PS locking bolt provides additional support to the post.
  • Additional Tibial Insert Options: For cases that need additional varus/valgus support, constrained (PS-C) tibial inserts are also offered, limiting varus/valgus liftoff.
2. Hamai, Miura, Marsuda, Shimoto, Higaki, Iwamoto: “Contact Stress at the Anterior Aspect of the Tibial Post in Posterior-Stabilized Total Knee Replacement” The Journal of Bone & Joint Surgery. 2010; 92:1765-1773

 

Advanced Patella Tracking

The APEX PS Knee uses an elongated patella track that nearly replicates the APEX CR Knee:

PS-patella-track

Smooth Articulation: The deep, wide patella groove is set at a 6° Q angle — Allowing smooth articulation with a spherical dome patella.

Patella Stress Reduction: The patella groove provides excellent patellofemoral contact, reducing stress on the patella into deep flexion.

Solutions to Patella Clunk: In typical PS designs, the patella can travel through 50° of flexion along the trochlear groove, before contact with the intercondylar notch. Interference between the patella and the notch has been associated with “patella clunk” and premature patella wear.[3]

ps-track-line

The APEX PS Knee Design helps prevent “Patella Clunk” through:

Advanced Patella Contact: The APEX PS femoral component offers 80° of uninterrupted patella tracking, providing patella contact throughout normal gait

Kinematics: Advanced patella geometry, combined with the extended trochlear groove, provides excellent patellar kinematics throughout entire range of motion.

3. Pollock, Ammeen, Engh: “Synovial Entrapment: A Complication of Posterior Stabilized Total Knee Arthroplasty” The Journal of Bone & Joint Surgery. 2002; 84:2174-2178.

 

Advanced Surgical Technique

Simple, efficient and precise.

Simple Transition: Utilizes the same 4-in-1 cutting block as the APEX CR Knee, making a seamless transition from a cruciate retaining to a posterior stabilized knee.

Efficient Cut Process: The cylindrical box cut matches the anatomical path of the intercondylar fossa, limiting the amount of bone resected and eliminating the need for multiple saw captures.

Precise Size Matching: The APEX Knee Systems (PS/CR) allow surgeons the ability to intra-operatively match the size of the tibial insert to the femoral components. Thus ensuring selection of a tibial tray with the best possible tibial plateu coverage paired with an insert that precisely matches the femoral component.

Copyright 2015 OMNIlife science, Inc.
For more information contact OMNI.