This is a repeated measures prospective study and is no greater than a minimal risk study. All study procedures will be conducted at the Center for the Intrepid (CFI) through collaborative efforts of the Military Performance Lab at the CFI and the Sanders lab at the University of Washington. Data collected at the CFI will be coded, compiled, and shared with the University of Washington investigators.The objective of the research is to test if microprocessor-adjusting sockets improve Service member performance in Military specific activities compared to (a) user- operated, motor-driven adjustable sockets (i.e. sockets users adjust themselves), and (b) static (traditional) sockets. Investigators also test if microprocessor-adjusting sockets better maintain socket fit and limb fluid volume, and if self-reported outcomes are more favorable than for user-operated or static sockets. The hypotheses to be tested include:

During intense Military specific tasks, compared to the user-adjusted socket and the static socket, the microprocessor-adjusting socket will:

1. minimize translational movement between the residual limb and the prosthetic socket;
2. maintain residual limb fluid volume; and
3. maximize prosthetic socket comfort.

When using the microprocessor-adjusting socket compared to the user-adjusted socket and the static socket, participants will:

1. cover the greatest distance during a simulated combat patrol;
2. perform all high intensity Military specific tasks with less pain;
3. perform a simulated combat patrol nearer to uninjured levels of performance; and
4. rank usability at a level similar to the static socket.

The specific aims are to:

1. Fabricate microprocessor-adjusting sockets specific for Service members and Veterans with goals of returning to high-level physical activities

2. Evaluate Military task performance in Service members with transtibial amputation using "Readiness Assessments," while wearing three socket configurations: microprocessor-adjusting, user-adjusting, and static

   • Simulated combat patrol in a Virtual Realty Environment
   • Military version of a Functional Capacity Evaluation

3. Characterize user preference and usability of different socket configurations

The purpose of the proposed research is to evaluate the use of microprocessor-adjusting sockets during "Readiness Assessments" of Military tasks performed by Service members with transtibial amputation.

Participants will come to the Center For the Intrepid (CFI) for up to 10 visits to complete a pre-monitoring session (assess residual limb health and gather information regarding limb fluid volume); socket fitting session(s) (fitting of three sockets- static socket, a user-adjusted socket, and microprocessor-adjusting socket); and for military readiness assessments for each of the three socket conditions.

Data across the three socket conditions (static socket, user adjusted socket, and Microprocessor-adjusting sockets) will be tested for normality. When it normality can be assumed, a single factor repeated measures ANOVA will test between socket conditions. Mauchly's Test of Sphericity was be used to test if the variance is significantly different across all of the conditions. If the sphericity condition is violated, a Greenhouse-Geisser adjustment will be applied. When a significance effect is detected, pairwise comparisons using a Tukey post-hoc will be performed to determine which conditions are significantly different. When normality cannot be assumed, a Kruskal-Wallis H test will be used. When a significance effect is detected, pairwise comparisons using a Mann-Whitney post-hoc while adjusting the p-value for multiple comparisons will be performed to determine which conditions are significantly different. Statistical significance will be set to p<0.05

Inclusion Criteria:

• Males and females age 18 - 55 years
• Authorized to receive care at the Center for the Intrepid
• Unilateral or bilateral transtibial amputation
• Have experience performing military relevant tasks (e.g., Active duty Service Member or Veteran)
• Current prosthesis user
• Ability to comply with instructions associated with functional testing
• Able to provide written informed consent

Exclusion Criteria:

• Self-reported inability to safely ambulate for a minimum of twenty minutes continuously and unassisted
• History of medical or psychological disease that would preclude safe gait, load carriage, physical, or cognitive functional training or testing within a virtual reality environment as determined by the provider screening the subject (i.e. moderate/severe traumatic brain injury, stroke, renal failure, cardiac or pulmonary problems disease, severe anemia, and other medical conditions)
• Any injury sustained to the upper extremity which would preclude safe physical performance testing
• Self-reported Blindness
• Self-reported Pregnancy
• Self-reported Active infection
• Weight above 250 lbs (114 kg)
• Residual limb length shorter than 9cm as this is the minimum distance necessary to attach the bio-impendence sensors
• Score greater than 20% on the Modified Oswestry Low Back Pain Questionnaire as this will indicate greater than minimal disability due to low back pain.