Knee prostheses reverse engineering: A preliminary investigation

Total Knee Arthroplasty is one of the most commonly performed orthopedic procedures and it is expected to grow in the next future . In the last past years, computer-assisted procedures represent one of the trends that are transforming the way of practicing medicine. Cornering the Total Knee Arthroplasty, digital models of the joints have been used to carry out simulation of their kinematics and mechanical performance. Whilst for the 3D digital reconstruction of the patient geometry several studies have been conducted, an approximated geometry of the prosthesis has been several times employed, with undeniable consequences on the final results. This paper aims at comparing two non-contact reverse engineering technologies to acquire the shape of femoral components employed for total knee arthroplasty. A high-level device (Konika Minolta Vivid 9i) and a mid-low cost laser (NextEngine) has been compared. For the comparison, a systematic procedure of acquisition and elaboration of the results has been adopted in order to have as unbiased as possible results. The procedure involves the use of the proprietary software of the scanners for the elaboration of the raw data and the meshing procedure has been kept the same for all the models. Since the as-is acquired mesh is of high-resolution, a decimation procedure has been carried out in order to make the 3D models lighter and easier to be handled. Once the decimation procedure has been evaluated comparing the original and the simplified models to one another, the digitalized models have been compared with the measurements taken from a coordinate measuring machines. As a preliminary result, the two lasers seem to be adequate to accomplish the reverse engineering process as required by this application. Of course, the mid-low cost laser would be preferable whether the performance will be confirmed to be (statistically) equal.