Effect of load on the early incorporation of impacted morsellized allografts

Impacted morsellized bone grafts are clinically successful to restore bony defects after faded total hip arthroplasties. The incorporation process see ms to be dependent on the location where the reconstruction is performed, w hich suggests that load could play a role. In this study, we hypothesised t hat, as in fracture healing, physiological loading has a stimulatory effect on the process of early bone graft incorporation. To test this hypothesis we created a standardised defect in the distal femur of twelve goats. Allog raft. p bone chips were impacted into the defect and a subcutaneous pressur e implant was screwed in. With this implant the graft can be loaded under c ontrolled circumstances. Six goats were subjected to a daily loading regime of 3 MPa, the other six were non-loaded. After five weeks the bone mineral density was measured with peripheral quantitative computer tomography. The reafter, routine histology and histomorphometry were carried out. Bone mine ral density was not affected by load. Histology revealed microscopic eviden ce of bone graft incorporation, which proceeded in a similar way in both lo aded and non-loaded specimens. New bone was formed free in the stroma or on graft remnants after osteoclastic resorption of the graft. Only the area o f active incorporating bone graft was higher tinder load. In conclusion, th e formation of a new bony structure was not affected by load after five wee ks. However, load resulted in a larger area of active graft incorporation a t this early stage. Possibly biological and immunological factors govern th e early incorporation process independent of the local loading regime. (C) 2001 Elsevier Science Ltd. All rights reserved.