Load-bearing increases new bone formation in impacted and morselized allografts

The effects of mechanical loading on the incorporation of morselized impact ed grafts were addressed in this study. Twelve skeletally mature rabbits we re surgically treated, Six rabbits received a proximal tibial joint replace ment with a tibial tray and a load-bearing 25-mm long stem. The tibia was p acked with fresh frozen, morselized, cancellous rabbit bone. No cement was used, In six other rabbits only the stem was inserted, without a tibial tra y, leaving the stem and the likewise impacted bone graft mechanically unloa ded. The rabbits were euthanized after 6 weeks, and the tibias were section ed and analyzed by histomorphometric examination, In the loaded specimens t he graft was resorbed and replaced by new bone (30% of area of interest) to a larger extent than in the unloaded specimens, Mechanical loading of an i mpacted, morselized graft surrounding a conical uncemented stem, increased the amount of new bone that replaced the graft. The ability of morselized i mpacted grafts to allow mechanical stimulation of ingrown tissue appears to be a principal cause for the success of this grafting procedure.