Fit accuracy of available standard knee implants is insufficient
With the standard implants available on the market for knee replacement, the choice from the limited number of implant sizes is often a compromise, which has a potentially negative impact on knee function and pain. As part of a study by the Chair of Medical Engineering at RWTH Aachen University, distributions of femoral implant sizes were optimized for over 85,000 patients. With a tolerated error limit of ±1.5 mm for the anterior-posterior and ±3 mm for the medial-lateral direction, which were derived from a literature analysis, and 12 optimized implant sizes, a coverage of almost 85% was achieved. This represents a significant improvement over existing commercial standard implant systems. However, even with 30 implant sizes, complete population coverage could not be achieved. Therefore, even with 12 optimized standard sizes, a patient-specific customized implant appears to be recommended for approximately 15% of the patients examined.
The study has been published in the Journal of Orthopaedic Research (open-access): https://onlinelibrary.wiley.com/doi/10.1002/jor.25464