The purpose of this study is to optimize the Defense Advanced Research Projects Agency's (DARPA) advanced upper limb prosthesis, the Modular Prosthetic Limb (MPL), by evaluating the performance, usability, and patient acceptance of the MPL in a clinical setting. This study will be a non-randomized limited clinical optimization study. The study will consist of two phases. Up to twenty-four upper extremity amputees will be recruited in order to ensure twelve subjects for participation in the study: 6 trans-humeral amputees and 6 trans-radial amputees. During Phase 1, subjects will be evaluated for their potential to operate the MPL using a virtual limb controlled by signals from surface electromyograms (sEMG). The first six trans-humeral amputee subjects and the first six trans-radial amputee subjects with a demonstrated proficiency controlling the MPL based on analytical performance metrics will enter Phase 2. During Phase 2, each subject will be fitted for the prosthesis with a custom socket. The user will then evaluate the prosthesis during twelve 1- hour or 1 and one half-hour sessions, working with an occupational therapist and research associates and completing both quantitative and qualitative assessments.

Inclusion Criteria

• Male or female subjects, 18 to 65 years of age with a unilateral or bilateral upper-limb amputation at any time prior to enrollment
• Active duty military, beneficiary, retiree, and civilian non-beneficiaries are all eligible to participate in this minimal risk study.
• If non active duty military, proof of verified, current health insurance in the form of a health insurance card must be provided in person and health plan expiration date not prior to the end of the projected study participation period will be verified.
• No prior history of vertebral disk disease/condition, sciatica or radiculopathy.
• Ability to follow study instructions and likely to complete all required visits for both phases of the study.
• Normal neurological examination with the exception of limb amputation.
• Medically cleared to use a prosthetic device based on residual limb condition and overall health, including participants both with and without prior prosthetic experience.

Exclusion Criteria

• Age less than 18 or greater than 65.
• Presence of mild to severe traumatic brain injury - permanent or temporary impairments of cognitive, physical, and psychosocial functions with an associated diminished or altered state of consciousness - as indicated by neuropsychological screening that is currently performed routinely on patients by the TBI program at WRNMMCB and noted in the subject's medical record.
• Current, known uncontrolled systemic disease.
• Any condition or situation that, in the investigator's opinion, may put the subject at significant risk, confound the study results, or interfere significantly with the subject's participation in the study.
• Subjects with lack of effort as determined by the research team. Subjects will be screened for effort using the Test of Malingering Memory (TOMM), with a score lower than 42/50 serving as exclusionary.
• Significant Axis I or II diagnosis determined by a neurologist or psychiatrist in the 6 months prior to entry into the study.
• Use of a pacemaker, so as to minimize the risk of surface electromyography interference.
• Lack of health insurance.