-Ujwal Parikh

Hip ResurfacingFemoral Component

Smith & Nephew, Inc

History of Hip Resurfacing

• Hip resurfacing procedures are performed since last 30-40 years but failed due to poor design.

• First performed by Dr. Derek Mc Minn and Dr. Roman Treacy.

• They performed the first metal on metal prosthesis at Royal Orthopedic Hospital Birmingham in 1996.

• FDA first approved BHR in 2006 by Smith & Nephew, Inc

What is HR?

• A conservative surgical technique of arthoplasty of hip.

• Done to mimic natural hip and have normal biomechanics, load transfer & range of motion at hip joint.

• Consists of 2-3 components:- Acetabular Component & Bearing surface- Femoral component

Who needs HR?

• Patients suffering from primary & secondary arthritis.

• Primary arthritis usually occurs in patients above 60 years.

• Secondary arthritis common in young patients and due to ankylosing spondylitis, rheumatoid arthritis, dysplasia and avascular necrosis of femoral head.

Design Input

BUECHEL-PAPPAS™ HIP REPLACEMENT SYSTEM – RESURFACING, ENDOTECH

Femur….

1. Femoral Head2. Femoral Neck3. Greater & Lesser

Trochanters

Reconstruction of Proximal Femur

• Scale Model• Sketch Trajectory• Create Datum Planes• Create Sketches• Use Swept Blend

Reconstruction of Proximal Femur

Anterior View Lateral View

Things To Remember…..

• Trajectory in center of bone and must follow bone curve.

• Vertex for all sketches should be at the same point.

• Use of blend should be in the same direction for all sketches

• VISUALISE!!!!

Construction of Femoral Component

Construction of FC

FC

• Dimensions:

• Material Used:Titanium Alloy- Ti6Al4V

My Implant (mm)

Outer Diameter 44.196

Stem Length 42

Inner Diameter 36.575

Family Table

• FT to avoid step cut if implant used to cut bone

Cut Out

Assembly (Bone + Implant)

Finite Element Analysis (FEA)

• Material Properties:Ti6Al4V Bone (Cortical)

Density 4.43 g/cc 1.8 g/cc

Poisson’s Ratio 0.342 0.04

Young’s Modulus 113.8 GPa 15 GPa

Yield Strength 950 MPa 130 MPa

FEA• Average male

weight= 190 lbf• To test the implant

we consider 2-3 times body weight = 450 lbf

• The Peak Load Axis is at 30 deg. with the vertical.

FEA

ConclusionMax Stress (Implant) Ultimate Yield Strength

33.5 Mpa 950 Mpa

Max Stress (Bone) Yield Strength

33.5 Mpa 130 MPa

The max. stress on implant and bone is less than ultimate yield strength for the implant and bone material .

Thus our implant has less chances for failure

Thank You !!!

References

• www.endotec.com• Smith & Nephew, Inc• http://www.hipresurfacingindia.com/• http://russellmeldrum.com/hips.html#• Fundamentals of Biomechanics- Ozkaya Nihat,

Nordin, Margareta• Wikipedia.org