The trial is designed to test the effectiveness of a force-feedback cuff in combination with a myoelectric prosthesis in conveying information on grasp strength to the user, as well as the user's preference regarding the feature.

The human sensorimotor control system uses both feedforward planning and sensory feedback information, in order to actuate the musculoskeletal system and interact with the external environment, e.g. when modulating grip force for various object properties. As a result, lack of sensory input, as in the case of motor impairments or amputations, can dramatically affect activities of daily living (ADLs). The contribution of the proposed research will be to test the effectiveness of a novel, non-invasive prosthetic technology in delivering sensory information. The investigators' approach is "modality matching," in that it produces a sensation in the user similar to the type of information to be transmitted. Specifically, the approach will combine the Soft Hand Pro (SHP), an anthropomorphic, myoelectrically controlled prosthetic hand, with an upper limb force feedback device (CUFF) to provide patients with transradial amputations with grasp force (pressure) information.

Inclusion Criteria:

1. age > 18 years.
2. no prior experience with the CUFF device.
3. history of elbow disarticulation, transradial, or transhumeral limb loss (non-control subjects only).

Exclusion Criteria:

1. amputation for less than 6 months
2. clinical history of brachial plexopathy, cervical radiculopathy or polyneuropathy
3. orthopedic, joint degeneration (i.e., arthritis, verified by x-ray) affecting the hand or cervical spine that severely limit upper limb function
4. visual problems that would interfere with the grasp task
5. co-existing central nervous system disease with symptoms that limit upper extremity function (e.g., multiple sclerosis, motor neuron disease, myasthenia gravis, Parkinson's disease, dystonia) revealed in medical history
6. significant rigidity as assessed through range of motion testing
7. active psychiatric illness
8. significant cognitive impairments (a score < 24 on the Mini-Mental State Examination)
9. use of medications that might affect sensory and/or motor functions
10. inability to effectively control myoelectrics for study purposes (control subjects only)