To design a Proximal Tibial Model using the tibial component, the cancellous and the cortical bones; and assembling these three parts together.

Additionally, to construct a new bone and tibia assembly and run Finite Element Analysis (FEA) on the model using Pro Mechanica to determine the Maximum Principal Stress and the von- Mises Stress exerted by the model.

DESIGN GOALS:

1. Effective kinematics restoration

2. Long term performance

3. Long term fixation

4. Installation with minimal damage to collateral structures

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A total knee replacement is a surgical procedure whereby the diseased knee joint is replaced with artificial material.

The thigh bone (or femur) abuts the large bone of the lower leg (tibia) at the knee joint. During a total knee replacement, the end of the femur bone is removed and replaced with a metal shell.

The end of the lower leg bone (tibia) is also removed and replaced with a channeled plastic piece with a metal stem.

Depending on the condition of the kneecap portion of the knee joint, a plastic "button" may also be added under the kneecap surface.

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Tibial tray and stem High performance Cortical and Cancellous bone

designs to fit the tibia A/P and M/L curvatures match normal knee Deep flexion ROM Excellent range of tibia sizing options FEA analysis on the proximal tibial model Stress analysis and Results

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The sizes applied to the tibial model are shown on the left. These are pretty standard and are observed in many commercial tibial systems.

These were referenced from the knee brochure from www.endotec.com

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The cancellous and cortical bone Pro/E Designs were provided by Dr. Makris (BME Department, NJIT).

The designs were created by using a standard swept blend and sketch options in Pro/E.

The bones were then cutout using the cutout feature.

Both the bones were assembled together using the assembly creation in Pro/E.

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Swept Blend

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Here is the exploded view of the Proximal tibial assembly.

In Pro/E, the view can be saved in the View Manager>explode> new.

This view is called Explode1.

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In the Applications section in Pro/E; click on Mechanica to run FEA

In Z-direction, apply a load of 100N on the top surface of the tibial component

Apply displacement constraint at the bottom of the bone

Assign the required materials and properties to the tibia and the bone

Run new static analysis for the results

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Force = 100 N applied on the top surface of the tibia

Displacement constraint at the bottom surface of the bone

TIBIA: Material used: TiAlly

› Young’s Modulus = 117.2 GPa› Poisson’s Ratio = 0.33

BONE:Material properties used: Cancellous Bone

› Young’s Modulus = 10.4 GPa› Poisson’s Ratio = 0.20

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Components Von- Mises Stress

(lbm/ (in sec2))

Maximum Principal Stress

(lbm/ (in sec2))

Bone+ Tibia 3.318 e2 1.084 e2

Bone 8.887 e1 3.142 e1

Tibia 3.318 e2 1.084 e2

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Tibial tray and stem constructed using the 10-32 thread Cortical and Cancellous bone designs to fit the tibia A/P and M/L curvatures would match the normal knee Excellent range of tibia sizing options: SIZE 1 used

(reference: www.endotec.com) FEA analysis on the proximal tibial model completed Stress analysis and Results obtained Results show that the von-Mises stress and the Maximum

Principal Stress are highest on the top surface of the tibia and the bottom curvature. This is understandable since the load is applied on the tibial surface. Also, the cutout on the bone shows a high stress due to the force applied on the tibia

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The scope and design goals of the project are achieved. A Proximal tibial model with a tibial component, a cortical and a cancellous bone assembled together were used as a model to run the FEA.

The results of the FEA showed higher stress on the top surface of the tibial tray and the bottom curvature of the tibial stem as suspected

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http://www.efunda.com/materials/alloys/titanium/properties.cfm www.endotec.com http://www.engineersedge.com/screw_threads_ch

art.htm

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