Why Medial-Pivot?

Kinematic Theory and Implant Design

In order to understand the functional outcome differences produced by various implant designs, it is critical to first examine the thought progressions that led to these designs. Many of today’s popular designs still adhere to outdated kinematic theories that incorporate less conforming tibiofemoral articulation to produce rollback. However, instead of producing rollback, these designs have been shown to produce instability and limited function.

The Evolution® Knee System restores function by replicating the natural AP stability and Medial-Pivot motion of the knee^[1],[2].

1) Dennis DA, Komistek RD, Mahfouz MR, Haas BD, Stiehl JB. Multicenter determination of in-vivo kinematics after total knee arthroplasty. Clin Ortho Relat Res. 2003
2) Freeman MA, Pinskerova V. The movement of the knee studied by magnetic resonance imaging. Clin Orthop Relat Res. 2003;(410):35-43.

The Evolution® Medial-Pivot knee is uniquely engineered to reproduce a healthy knee’s stability and motion. The Medial-Pivot knee features a highly conforming medial side that results from a constant radius design, reproducing the natural function and stability of the ACL and PCL^[1],[2]. This design is unique from every other less conforming traditional knee system. With a stable, pivoting medial side and a lateral side that rolls forward or backward throughout flexion, the Evolution® Knee System is designed to feel and function like a natural knee. The Medial-Pivot knee system enhances quadriceps efficiency and reduces the quadriceps avoidance found in traditional knee replacements. By enhancing quadriceps efficiency, the patient can have increased proprioception and a more normal feeling knee^[3]. Patients can tell a difference according to a peer-reviewed study that examined patient satisfaction among patients who underwent bilateral staged total knee replacement with different prostheses. A Medial-Pivot design was preferred equally to an ACL-PCL retaining prosthesis and preferred more than all other designs (CR, PS, and Mobile-Bearing)^[4].

1) Dennis DA, Komistek RD, Mahfouz MR, Haas BD, Stiehl JB. Conventry award paper: multicenter determination of in vivo kinematics after total knee arthroplasty. Clin Orthop Relat Res 2003;416:37-57. ,br>2) Schmidt R, Komistek RD, Blaha JD, Penenberg BL, Maloney WJ. Fluoroscopic analyses of cruciate-retaining and medial pivot knee implants. Clin Orthop Relat Res 2003;410:139-47.
3) LaMontagne M, et al. Quadriceps and Hamstring Muscle Activation and Function Following Medial Pivot and Posterior Stabilized TKA: Pilot Study.
4) Advance® Medial-Pivot was preferred over PS, PCL, and mobile bearing prostheses; preferred equally to the ACL-PCL design. Pritchett JW. Patients prefer a bicruciate-retaining or the medial pivot total knee prosthesis. J Arthroplasty. 2011 Feb;26(2):224-8.

Consequences of instability

Anterior knee pain

As the femoral component of a traditional implant design slides forward in early flexion, the added force causes the extensor mechanism to attempt to stabilise the knee during activities. This force eventually causes pain by tiring the extensor mechanism.

Loss of quadriceps performance

As the extensor mechanism tires, patients begin using a quadriceps avoidance gait to adapt to the weakening extensor, which can lead to pain.

In order for patients to compensate for the instability and pain, the quadriceps must continually contract in order to prevent the femur from sliding forward. Patients ultimately waste much of their quadriceps performance attempting to compensate for this instability.

Slower functional recovery

Lack of functional stability can hinder ability to get back to daily activities. Patients can feel less comfortable during activities such as moving up or down stairs and getting in and out of chairs.

Excellent outcomes and lower 30 days readmission rates

Evolution® Medial-Pivot knee achieves higher patient satisfaction than other total knee replacement designs on the market and shows a lower 30 days readmission rate and complications than traditional knee replacements^[1],[2].

“My patients that have had the Evolution Knee seem to get back to a normal degree of function more rapidly.”

– Dr. David Backstein MD, MEd, Toronto, ON

Improved stability and validated outcomes

The Evolution® Medial-Pivot knee system is built upon a legacy of 95% patient satisfaction^[1] with 98.8% survivorship at 17 years^[2], and features a design that enhances quadriceps efficiency^[3], allowing for improved proprioception.

1) Van Overschelde PP, Fitch DA. Patient satisfaction at 2 months following total knee replacement using a second generation medial-pivot system: follow-up of 250 consecutive cases. Ann Transl Med. 2016;4(18):339. doi:10.21037/atm.2016.08.41
2) Based on a retrospective study of Advance® Medial-Pivot. Macheras, G.A.; Galanakos, S.P.; Leptsos, P.; Anastasopoulos, P.P.; Papadakis, S. A. A long term clinical outcome of the Medial Pivot Knee Arthroplasty System. The Knee 24 (2017): 447-453.
3) LaMontagne M, et al. Quadriceps and Hamstring Muscle Activation and Function Following Medial Pivot and Posterior Stabilized TKA: Pilot Study.

Stability you can count on

Unique kinematic design

Evolution® Medial-Pivot Knee system exhibits a repeatable motion.

Replicates the kinematics of the natural knee.
Resists multi-directional motion often occurring in traditional knee replacements, which some studies have linked to increased wear.

– Dr. Russell Nevins MD, Las Vegas, NV