The purpose of this study is to determine if subthreshold vibration, when applied to the residual limb of a lower limb amputee through their prosthetic socket, can sufficiently enhance peripheral sensation to result in an improved ability to balance and walk.

One of the many complications of diabetes is the loss of sensation in the feet. This sensory deficit can negatively impact the postural stability and mobility of non-amputees, since without feedback, it is simply more difficult to stand and walk. For lower limb amputees, the problem is compounded. These patients often have difficulty with prosthetic limb placement during maneuvering tasks, exhibit dramatic increases in the movement of their center of pressure during quiet standing, and both clinical and observational gait analysis reveal significant changes in their gait pattern relative to non-amputees.

The investigators' work proposes to explore the use of a novel prosthetic intervention for diabetic lower limb amputees. The investigators hypothesize that the intervention will sufficiently enhance proprioception to result in measurably improved postural stability and locomotor function for these patients. The intervention is based on a phenomenon known as stochastic resonance, whereby the application of sub-threshold vibration enables mechano-receptors previously unable to respond to stimuli to become more susceptible to depolarization. For Veterans with neuropathic proprioceptive losses, stochastic resonance may facilitate a functional response from subtle stimuli where gross inputs were formerly required.

Inclusion Criteria:

Amputee subjects:

• unilateral transtibial amputee of diabetic etiology,
• have been fit with a prosthesis and have used a prosthesis for at least one year,
• wear the prosthesis at least 4 hours per day,
• ambulate without upper extremity aids,
• have no history of injurious falls within the previous six months, and
• touch sensation measured by a 10 gauge Semmes-Weinstein Monofilament in the dermatomes of their residual limb.

Exclusion Criteria:

Subjects will be excluded if:

• they have a significant lower extremity pain condition, musculoskeletal disorder, or neurological deficit that interferes with their ability to pursue typical daily activities or alters their gait characteristics,
• their residual limb is ulcerated, or
• are currently using anticonvulsant medications for the treatment of neuropathic pain.