Triathlon

®

Design Rationale Don’t just replace the knee. Replace the way the knee moves.1-3

Table of Contents Design Motion

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Hyperextension/Extension. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Active Flexion.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Deep Flexion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Contact Area.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Rotation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Pivot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Recovery Fit

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Femur – Implant Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Femur – Instrument Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Tibial Coverage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Polyethylene

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Wear Resistance .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Oxidation Resistance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Mechanical Strength. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Fracture Toughness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

References

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Experience the difference of our circular, single-radius design.

Triathlon®   Design Rationale

Design Since its first use in surgery in 2004, Triathlon has demonstrated what a knee replacement system can offer patients.5,26 Triathlon’s distinction as a modern knee with a wealth of clinical support offers surgeons modern advancements in motion with confidence in implant selection. When Triathlon was designed, Stryker examined the leading reasons why knee replacements require revision25 and designed the features of Triathlon to address Early and Late Failure modes. Clinical studies 1,3,9,17,26 orthopedic registry results5 and laboratory studies 2,15,43,44 have demonstrated the potential performance and functional benefits of the Triathlon Knee System.

Early Failures Modes3 Revision Cause

Design Feature

Instability

Single Radius1-3,26 Anatomic Cam/Post Engagement11

Extensor Mechanism Deficiency

Single Radius1,4,9

Malposition

FlexRod12

Late Failures Modes3 Revision Cause

Design Feature

Polyethylene Wear

X3 Polyethylene,16 Locking Mechanism,15 Anterior Post Design,44 Appropriate Contact Area39,40

Loosening

Tibial Keel,43 Post Geometry,44 Rotary Arc17

When evaluating a knee system, the clinical questions to ask are the following:

1. Can it improve implant survivorship? A 2013 study showed implant survivorship was 99.7% at a final follow-up of 7 years with Triathlon.67

2. Can it improve patient recovery and function? Clinical studies have shown reduction in physiotherapy sessions,1 more rapid abandonment of crutches,1 and less anterior knee pain 9,26 comparing single radius to multi radius knees.

3. Can it introduce any new failure mode? X3 achieves oxidation resistance without the use of additives.16,18,19 Multiple attempts by manufacturers to combine additives into polyethylene have yielded unfavorable results including additive leaching and polyethylene damage.37,38

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Triathlon®   Design Rationale

Motion Hyperextension/Extension Triathlon is designed to allow for +/- 10 degrees of rotation in hyperextension and extension.44 In these early degrees of motion, Triathlon has demonstrated less post impingement and torque forces than other designs.44

Active Flexion Stryker’s single radius knee is designed to replace the way the knee moves.1-3 Traditional theory used a direct lateral view of knee motion to characterize the shape of the posterior condyles. From that view, the posterior condyles appeared oval in shape.20 Modern research examined the knee looking along the transepicondylar axis, which revealed that the shapes of the posterior condyles were circular.21,22 More specifically, a cadaver study showed that the active flexion radius ranged from 10° to 110°.21 Stryker’s virtual bone database of over 1,000 consecutive femurs provides support and rationale for Triathlon.53 This single radius has been discussed by various researchers,21,22 and is apparent in sample images of femurs from the SOMA database.53

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Deep Flexion Triathlon is designed to accommodate up to 150 degrees of deep flexion.28 This is achieved through the interaction of the shortened, flared posterior condyles and rotary arc. The flared posterior condyles7 and the rotary arc6 are designed to accommodate up to 20 degrees of internal/ external rotation. The shortened posterior condyles facilitate the relaxation of the soft tissues 6 and mitigate the need for additional tibial slope resection.

Deep Flexion

Harwin et al28

Mean

Max

126º

150º

“The Reality of Additional Insert Thicknesses” Balancing the knee is a principal goal in total knee replacement, and can be impacted by femoral geometry and technique. Some new knee systems offer 1mm incremental insert thicknesses.63,64 However, the data from a competitor offers little evidence that these insert options address a clinical need.59 Zimmer’s own data shows that as loads increase on the knee, the effect of 1mm incremental insert thicknesses on AP and IE laxity is reduced as shown in the chart.59

Average change [per 1mm of insert thickness]59

AP Laxity

1/3 mm

IE Laxity

2 degrees



•Z  immer tested up to 112 pounds of force (500 N), and the effect on AP and IE laxity is reduced as force increased.59 The average weight of a knee replacement patient is 185 pounds.61



•A  ctivities like walking, exercising, and golfing can lead to 2-4 times body weight of force.66

As the average knee replacement patient engages in these activities, how meaningful are these additional insert thicknesses? Instability is a leading cause for early revision,38 and one study demonstrated that Triathlon has 99.7% survivorship at 7 years.67

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Triathlon®   Design Rationale

Contact Area Triathlon is designed to exhibit an appropriate contact area throughout the range of motion.40

Figure 2: Contact patch for 30º flexion

Figure 4: Contact patch for 90º flexion

Comparing Contact Area Designs, like Triathlon,40 with smaller contact areas have been shown to wear less than designs with larger contact areas.39

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Rotation 60

15° Flexion ±10° Rotation

50 40

Company S

Company Z

Company J

Triathlon

Company S

0

Company J

20

Company Z

30

10

Traditional

0° Flexion ±10° Rotation

Triathlon

Triathlon is also designed to reduce rotational constraint compared to other systems.44

Peak to Peak Post Torque44

Torque (Nm)

Triathlon is designed to accommodate up to 20 degrees internal and external rotation.6,7,27 This can be accomplished via the patented rotary arc49 and the shortened and flared posterior condyles.

Design

Rotary Arc

Pivot Komistek et al demonstrated that the normal, healthy knee exhibits a medial pivot 80% of the time.24 Many traditional knee systems are designed based on this premise and drive a medial pivot. Komistek also demonstrated that patients with various knee replacement designs demonstrated a medial pivot 55% of the time.24 Given the variability in pivot in knee replacement patients, Triathlon was designed to allow the soft tissues to guide pivot. There are no design features in Triathlon that promote a particular pivot location, giving the patient’s soft tissues the ability to pivot as needed.

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Triathlon®   Design Rationale

Recovery A study showed that select patients without post-op complications who received Stryker’s single-radius knee replacement abandoned crutches sooner and required fewer physiotherapy sessions than patients with traditional knee replacements.1 Patients with a single radius knee have also demonstrated less anterior knee pain than patients with a multi radius knee.9,26 Triathlon also incorporates the same patellofemoral design as Duracon, which demonstrated