Orthopedic Adaptor Oral Presentation #3 Kate Huddleston Anna Duloy Alexander Byall Ashley Goodnight

Schematic of Femur and Tibia

Schematic of Knee with Prosthesis (pre-periprosthetic Fracture)

Schematic of Femur and Tibia post-Periprosthetic Fracture

Project 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 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 Background Periprosthetic femoral fractures These fractures occur: when femur weakens during surgery in patients with osteoporosis and rheumatoid arthritis No current method to attach nail and prosthesis Background: Periprosthetic fracture is described as "an age-sex-specific increase in the rate of fracture in a given anatomical location with the presence of a prosthetic implant." A periprosthetic femoral fracture is seen if the anterior femoral cortex is notched and weakened during surgery and in patients with osteoporosis, rheumatoid arthritis, poor flexion, revision arthroplasty, and neurological disorders. The management of periprosthetic femoral fractures is quite complex, and often involves surgery. A wide variety of surgical techniques are described to treat these types of injuries, including the use of a retrograde femoral nail. As the number of implants placed increases, it is inevitable that associated fractures also become more common. Once a fracture occurs, treatment is complicated by osteoporosis, defects in the bone, and the presence of the implant. There are 300,000 total knee replacement surgeries performed per year. The incidence of a periprosthetic femoral fracture after total knee replacement is 0.6-2.5%. Using the average of 1.55% incidence rate, there are approximately 4,650 cases of the periprosthetic femoral fracture a year. This fracture can occur more than 10 years after joint replacement; thus, as the number of patients with replacements accumulates and life expectancy continues to grow, more fractures occur. The range of patients having this type of fracture ranges from early forties to early ninties with an average age of 68. They occur more so in women for a 2 to 1 ratio.

Importance 300,000 total knee replacements per year. Of these there are 4,650 cases of periprosthetic femoral fractures (Incidence rate 0.6%-2.5%) Target population: average age of patient is about 68, but range lies anywhere from 42-92

Cost Cost of periprosthetic femoral fracture repair: Cost of adaptor: $30,000 (physician, hospital stay, radiology) Cost of adaptor: Unknown at this point Material decided, but specifications undecided http://www.emedicine.com/orthoped/topic254.htm

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

Initial Adaptor Schematic

Current Adaptor Schematic

Adaptor Advantages Significantly quicker procedure 2 pins versus 4 Less surgical dissection Less blood loss Better way to maintain alignment between femur and prosthetic knee

Biomaterials 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

Current Status Weekly meetings in Med Center Orthopedics Lab with Advisors Attachment Mechanism Details (dimensions) Schematic Specifications Contacted Johnson & Johnson Ordered retrograde femoral nail

Future Work Work out details of chosen design Draw design on CAD Determine Stresses Work on installation procedures Continue meeting with advisors

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

References 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