Implant Geometry Optimization

The three primary goals of this project were to ensure all devices fit as close as possible to any patient's bone, reduce the number of unique devices required, and optimize screw trajectories.

DePuy Synthes is a family company of Johnson & Johnson which specializes in orthopedic medical devices. During my co-op, I worked on a team which develops intramedullary nails to aid in the fixation of long bone fractures. Due to my skills and interest in CAD design, I began working on a plate which could be used in conjunction with a femoral nail to add support for patients with poor bone quality. By working with orthopedic surgeons and gathering input, we were able to establish what the maximum bone to plate distance was on various locations of the femur. I then utilized existing bone scans from a wide range of patient demographics to create "kilo" assemblies (explained in more depth below) in Creo. Next, I took measurements of the bone to plate distance for each assembly at three different locations. By compiling this data and comparing it to the requirements given by surgeons, I was able to determine where geometry adjustments needed to be made. In what was later called a fascinating idea, I then created "mega" and "giga" assemblies which were essentially assemblies of the individual bone and implant "kilo" assemblies carefully constrained together. This allowed me to see patterns and similarities between the bones and eventually separate all of the assemblies into two groups, where a unique implant would be contoured to each group. The existing implant CAD model was modified to make the top, middle, and bottom surfaces driven by individual splines, which together form a quilt surface. A visualization of this can be seen in the large figure below. By using this technique, the surfaces could be easily smoothed and contoured to fit the bone assemblies. Finally, I optimized the 3.5mm screw hole trajectories by adjusting their angle to minimize interference with the intramedullary nail, while also being as spread out as possible to allow for maximum support throughout the bone.

The above pictures show the implant before and after my optimization, and a visualization of my surfacing method.

As seen in the figures above, before I began my geometry changes and design optimization for the two groups, there were a number of bone assemblies that with the current implant design, had measurements which exceed the allowable distance. After my optimization, all measurements were within the allowable distance and fit closer to all bone scans, thereby improving quality of life for future patients.