Impaction technique and graft treatment in revisions of the femoral component - Laboratory studies and clinical validation

The micromotions of femoral stems cemented into impacted bone-graft were st udied in 23 femora from adult sows. The model was validated against 2 patie nt groups. Conventional impaction technique and a new impaction technique u sing polished and rotating impactors were studied in the preclinical model and in 14 and 10 patients with type II defects. The specimens were loaded i n an MTS (Minneapolis Testing System) machine for 72,000 cycles at 250N to 3,250N. The bone-graft was rinsed in tepid water, and most of the bone marr ow and fat were removed. Radiostereometric measurements revealed small subs idence of the stems cemented into the specimens and the patients 6 weeks af ter the operation without any difference (median values, -0.06 to -0.16 mm) . Further studies of specimens operated with nontreated bone-graft showed t hat extraction of fat increased the stability. Our findings suggest that th e early postoperative implant stability after impaction grafting of the fem ur mainly is an effect of surgical technique and graft treatment. The new i mpaction technique, with which we hoped to obtain a more reproducible proce dure and less risk for perioperative fracture, resulted in stability equal to that obtained with the conventional technique.