Orthopedic AdaptorOrthopedic AdaptorOral Presentation #4Oral Presentation #4

• Kate Huddleston

• Anna Duloy• Alexander Byall• Ashley

Goodnight

Schematic of Femur and TibiaSchematic of Femur and Tibia

Schematic of Knee with Prosthesis Schematic of Knee with Prosthesis (pre-periprosthetic Fracture) (pre-periprosthetic Fracture)

300,000 total knee replacements per year

Schematic of Femur and Tibia post-Schematic of Femur and Tibia post-Periprosthetic FracturePeriprosthetic Fracture

7,500 Periprosthetic Fractures Per Year

Project DefinitionProject Definition• To design an adaptor that will

connect the nail inserted into the shaft of the femur to the knee prosthesis, in the event that a periprosthetic femoral fracture has occurred

List of ConstraintsList of Constraints

• Hold the nail 5 degrees relative to the prosthetic joint

• Universal• Maintain rigid structure• Irremovable knee

prosthesis• Compatible with both

right and left knee

Project BackgroundProject Background• Periprosthetic femoral fractures• These fractures occur:

– when femur weakens during surgery

– in patients with osteoporosis and rheumatoid arthritis

• Patent Search - no current method to attach nail and prosthesis

ImportanceImportance• 300,000 total knee replacements

per year. Of these there are 7,500 cases of periprosthetic femoral fractures (Incidence rate 0.6%-2.5%)

• Target population: average age of patient is about 68, but age ranges from 42-92 years

CostCost• Cost of periprosthetic femoral

fracture repair:– $30,000 (physician, hospital stay,

radiology)

• Cost of adaptor:– Exact price unknown at this point– Material decided as titanium, but

specifications undecided

Attachment MechanismAttachment Mechanism• Brainstorm on pros and cons of each• Practicality of design• Ease of use• Twist and lock was a possible

mechanism:

Initial Adaptor SchematicInitial Adaptor Schematic

22ndnd Adaptor Schematic Adaptor Schematic

Current Adaptor SchematicCurrent Adaptor Schematic

Adaptor AdvantagesAdaptor Advantages

• Significantly quicker procedure– 2 pins versus 4

• Less surgical dissection– Less blood loss

• Better way to maintain alignment between femur and prosthetic knee

• Factors to consider:– Compatibility with nail (same material)

and prosthetic material– Oxidation reactions, Galvanic corrosion– Strength– Expense– Availability– Chosen Material:

• titanium (Grade 5 or 6-4) - nail and adaptor• cobalt chrome - knee

BiomaterialsBiomaterials

CAD Drawing for Current CAD Drawing for Current SchematicSchematic

CAD Drawing with Applied CAD Drawing with Applied StressesStresses

• Analysis for 100 N applied to both sides

• The maximum stress is 1500 MPa.

• Yield stress for titanium 6-4 is 800 MPa, so our adaptor would break.

DifficultiesDifficulties

• Head of the screw – too big• Waiting for exact dimensions of

the retrograde femoral nail• Difficultly measuring the prosthesis

PrototypePrototype• Machine Shop: Cupples J&J Co., Inc.

in Jackson, TN• Contact: John Landrum• Plastic prototype not possible• Titanium prototype wired with EDM• Not to cost over $200

Current StatusCurrent Status• Weekly meetings in Med Center

Orthopedics Lab with Advisors• Attachment Mechanism

– Details (dimensions)– Schematic– Specifications– CAD Drawing, Solidworks

• Contacted Johnson & Johnson• Waiting retrograde femoral nail

Future WorkFuture Work• Determine stresses on prototype• Continue work on CAD• Research mechanical properties of

titanium 6-4• Work on installation procedures• Continue meeting with advisors• Set up meeting with Dr. King for

needs

AcknowledgementsAcknowledgements

• We would like to thank the following people for their help:– Dr. Limbird– Jeff Gordon– Sue Larson– Mike Bailey– Dr. King

ReferencesReferences

• http://www.emedicine.com/orthoped/topic254.htm

• http://www.orthoteers.co.uk/Nrujp~ij33lm/Orthtkrperiprosthfrac.htm

• http://www.eng.hull.ac.uk/research/medical/fracture_plate_intro.htm