Promotion of bony ingrowth by low intensity high frequency oscillatory intramedullary pressure stimulation

The ability of fluid flow stimulation to promote bony ingrowth was evaluated in an in vivo model. A fluid loading device and a stainless-steel screw implant were placed parallel to each other across the dorsal cortex of the left and right ulna diaphysis of 4 adult, one year old, skeletally mature male turkeys. The left ulna received a 30 Hz, 70 mmHg oscillatory intramedullary pressure stimuli. The right ulna served as the sham control. Backscatter electron microscopy was used to quantify the relative bony ingrowth into the space between the implant and cortical bone after four weeks of fluid flow stimulation. The non-stimulated ulna resulted in a mean 11% (±6.6) ingrowth of bone towards the implant. A daily 10- minute regimen of fluid flow stimulation caused 24%(±5.3) of the implant area available for ingrowth to be filled with bone. Although the difference between the amount of cortical bone growth into the non-stimulated and the fluid flow stimulated implant is not significant (p=0.068), this study, for the first time, showed that bone adaptation could be promoted by pure fluid flow stimulation.