Intramedullary instrument/device insertion during total joint replacement can generate high intramedullary pressures, with potential for clinical fat embolism syndrome. We evaluated effects of process parameters on intramedullary pressure generated when hammering an implant into a simulated femur analogue. Lower implant insertion speed, lower hammering force, a rubber- compared with steel-tipped hammer and a larger synthetic bone-to-implant radial gap reduced intramedullary pressure generated. Number of hammer strikes required to insert an implant increased with increasing marrow viscosity, whereas intramedullary pressure decreased with increasing viscosity. Significant intramedullary pressure reduction is obtained by applying more strikes of lower peak force using a rubber hammer tip, as opposed to fewer larger strikes. Caution should be exercised when instrumenting the distal femur, where viscosity is low and very high intramedullary pressures can be generated.



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