RESUMO
Introduction: In order to improve the anchorage behavior of short hip stems, this development project aims at designing a short hip stem concept that preserves the femoral neck and minimizes interference with the physiological stress distribution of the femur. The new design will be evaluated according to ISO 7206-4 which is the standard for testing Implants for surgery. Methods: Basic CAD models based on an established short stem prosthesis were created and evaluated using finite element analysis. The best design was further developed to achieve a more deformable stem while maintaining stability. The model was validated through in vitro testing. Results: The "H-Beam" short stem showed a higher degree of deformation of approximately 142-144% compared to the established short stem. The FE model had a relative error of 0.98% and 1.07% compared to the in vitro tests. An operating procedure was outlined for this new short stem design. Discussion: The FE model is deemed valid due to small differences in comparison to in vitro testing. The short-stem prosthesis is more flexible and can be easily adapted to individual anatomy during surgery. The prosthesis length is similar to conventional prostheses, but the new stem design could allow better and faster osteointegration while preserving the cancellous bone structure.
RESUMO
To determine size and shape discrepancy between the bone of Korean women and the prostheses in total knee arthroplasty, the height(antero-posterior length) and width(medio-lateral length) of the distal femur and the proximal tibia were measured at the bone resection level for 104 knees of 62 female patients who underwent primary total knee arthroplasty and compared with the same parameters of the total knee prostheses designed by five different companies. On the condition that the height of the prostheses matched with each cases of the bone were optimal, the difference in the width was evaluated, and the criteria of the discrepancy were overhang if the width of the prosthesis was larger than bone, optimal if width of the prosthesis was same or smaller and difference was within 5 mm, and down-size if smaller and difference was over Smm. In femoral prostheses, 34.6% of all were optimal, 13.1%, overhang and 52.3%, down-size. In tibial prosthesis, 54.1% of all were optimal, 13.9%, overhang and 32%, down-size. In conclusion, although further investigation for clinical application is needed, there were discrepancies in size and shape between the femur and tibia of Korean women and total knee prostheses and improvement in design should be considered.
