Development of an Electrical Stimulation Device for Osseointegrated Amputees - A Novel Approach for Expediting Skeletal Attachment and Rehabilitation

The projected number of American amputees is expected to rise to 3.6 million by 2050. Many of these individuals depend on artificial limbs to perform routine activities, but prosthetic suspensions using traditional socket technology can prove to be cumbersome and uncomfortable for a person with limb loss. Moreover, for those with high proximal amputations, limited residual limb length may prevent exoprosthesis attachment all together. Osseointegration technology is a novel operative procedure that allows integration between host tissue and an orthopaedic implant and has been shown to improve clinical outcomes by allowing direct transfer of loads to a bone-implant interface. However, the associated surgical procedures require long rehabilitation programs that may be reduced through expedited skeletal attachment via electrical stimulation. To determine optimal electrode size and placement, we have developed a system for computational modeling of the electric fields that arise during electrical stimulation of residual limbs. Three patients with retrospective CT scans were selected and three dimensional reconstructions were created using customized software (Seg3D and SCIRun). These software packages supported the development of patient specific models and allowed for interactive manipulation of electrode position and size; all variables that could affect the electric fields around a percutaneous osseointegrated implant. Preliminary results of the electric fields at the implant interface support the need for patient specific modeling in order to achieve the homogenous electric field distribution required to induce osteoblast migration and enhance skeletal fixation.