Light weight femoral stem optimization based on design and materials

摘要

One of the main constituents of total hip replacement (THR) is the design reconstruction of femoral stem component. The major causes of the debonding of the stembone interfaces include the aseptic loosening of the femoral stem, dislocation, wear, fatigue, micromotions, design factors, and certain biological responses generated due to the interaction of the implants with the body environment. The usage of cemented stems result in the generation of the high cement mantle stresses thereby results in the loosening of the implants. The porous stems developed by various manufactures are of solid stems with indentations, with collars, collarless, tapered stems; tear dropped polished stems without indentations offer greater rigidity, results in the transfer less load proximally, which results in greater stress shielding of the proximal femur. Stress shielding is found to be the major cause for the failure of the hip implants and revision surgeries. A stem of low stiffness alone would not suffice in achieving a reduced or optimal stress shielding. The biomaterials such as 316L stainless steel (SS), cobaltchromium alloys (CoCrMo), and titanium alloys (Ti6Al4V) used in THRs provide high strength to weight ratio and have an excellent biocompatibility. Skeletal femoral stems with varying cross sections were designed. The materials used for the design were 316L stainless steel and Ti6Al4V. The femoral stem with hexagonal cross section was optimized based on the design that has low weight and better load-bearing capacity. This novel design would ameliorate the implant fixation, aid in optimal rigidity, enhance the medullary revascularization, and offer better motility to the patient.