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Stability of Percutaneous, Osseointegrated Implants: A 12 Month Study Using an Amputated Ovine Model

Kent N. Bachus, PhD

An individual’s quality of life is greatly affected by the loss of one or more limbs. To restore function, socket prosthetics are traditionally used; however, these devices have issues with the fit of the prosthetic and are inadequate for some patients. To help restore these individuals to preamputation levels of activity, percutaneous, osseointegrated implants are being investigated to attach exoprostheses to the residual limb. We have established an ovine model to assess the function of a percutaneous, osseointegrated prostheses over a 12 month time period. The purpose of this study was to determine the stability of these implants over time by comparing in-vivo vertical limb forces before and after amputation as well as stride length and stance phase as a percent gait cycle, and post-mortem bone ingrowth, periprosthetic remodeling, and implant tensile tests on 0, 3, 6, 9, and 12 month animals.

The sheep loaded their amputated limb 84% of their preamputation condition 3 months following amputation. By 12 months, the loading had decreased to 77%. The animals primarily compensated by applying more load to the left forelimb and left hindlimb. Although there is not an increase in the amount the sheep are load bearing following surgery, this does confirm that the endoprostheses are being loaded.

The results from this study are very promising regarding the bone-implant interface. Over the next 6 months, bone ingrowth, periprosthetic remodeling, and bone implant strength will be assessed. This will lead to a better understanding of bone-implant stability and help in creating percutaneous, osseointegrated implants for humans. This work was supported by the Department of Defense PRMRP Grant (No. PRO54520).

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Last modified: Nov 09, 2009, 22:13 EST
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