Introduction: Several factors of which many still are unknown may influence the mechanical strength of the impacted morsellised bone applied in revision hip surgery. To avoid initial subsidence of the prosthesis can be crucial for the survival of the revised joint. Impacted grinded bone forms a porous structure where the void space mainly is filled by liquid consisting of water and fat.

Purpose of Study: To determine the influence of moisture on the stiffness strength of impacted morsellised bone.

Material and methods: Juxtaarticular bovine bone is morsellised and experimentally impacted by standardised methods. The stiffness of the bone was recorded during bone sample construction and loading the impacted bone sample, in a brief undrained and a longer drained phase. Water and fat content were measured in loose and compressed bone material and could be altered by reproducible methods. A trial on drainage during impaction was executed. All studies were compared with a base line study. This trial was carried out as similar as possible to the routine, clinical situation.

Results: Dried bone had very high axial stiffness properties. Lowering fat content resulted in bone samples, which had significantly higher stiffness during the undrained loading period but did not diverge during drained loading. Drainage during impaction had no effect on axial strength of the bone.

Conclusion: Low water content in morsellised bone has considerable positive effect on the axial strength of impacted bone. Fat lowering may have a positive effect during initial load phase but this advantage diminishes over time. In this experimental study draining through impaction did not improve axial strength. This is probably due to the transitory effect impaction has on porous pressure.