Abstract
It has been generally accepted that dynamic mechanical load is important for normal bone physiology, remodeling and fracture healing. Impacted morsellized grafts can be seen as healing of many small fractured bone parts, involving bone remodelling, apposition and formation of new bone. Therefore load may be stimulative for the incorporation of this type of graft.
In a pilot study we observed a positive effect of load on the density of incorporated bone after 12 weeks. Based on these results we hypothesised that physiological loading has a stimulatory effect on the early stage of bone graft incorporation. To test this idea we implanted fresh frozen allograft bone chips in 12 goats and loaded these grafts with the newly developed subcutaneous pressure implant ( Lamerigts et al., Biomaterials2000; 21: 741–7). The goats were divided in two groups: non-loaded and loaded. The loaded group was subjected to a loading regime of 3 MPa for 5 days/week (1 Hz, one hour/day). After 5 weeks the bone mineral density was measured with quantitative CT scanning, followed by routine histology and histomorphometry.
Bone mineral density was not affected by load. Histology revealed microscopic evidence of normal bone graft incorporation as seen in previous studies. The amount of active incorporating bone was higher under load (p< 0.05).
The formation of a new bony structure was not affected by load in this early stage of bone graft incorporation. However, load resulted in a more active graft incorporation after 5 weeks. The difference between the loaded and non-loaded group might be partially obscured by a low level of physiological loading in the non-loaded group induced by the daily activity of the animals.
