Bigger size and defatting of bone chips will increase cup stability

Morcellised bone allograft in an in vitro model was used to test the tenden cy towards cup rotation using small or larger fragment sizes of an impacted graft bed and different fat contents. A cup cemented on an impacted graft bed of larger sized bone chips from the Howex bone mill containing natural marrow fat was loaded eccentrically until the cup rotated. This required 34 50 N. The same chips impacted in the same way, but defatted with warm salin e solution required 7000 N for rotation. The smaller sized bone chips from the Tracer bone mill defated in a similar manner required only 1950 N for c up rotation. The conclusion was that larger sized chips, partly defatted, p revent rotation of a cup cemented on a graft bed.